F1000Research F1000Research 2046-1402 F1000 Research Limited London, UK 10.12688/f1000research.157612.3 Research Article Articles Prevalence and risk factors of Acinetobacter baumannii infection in Pediatric Intensive Care Unit at Thammasat University Hospital

[version 3; peer review: 2 approved]

 Bunjoungmanee Pornumpa Conceptualization Methodology Project Administration Supervision Writing – Original Draft Preparation Writing – Review & Editing https://orcid.org/0000-0002-1285-7672 a 1 Rattanapan Kornkamon Conceptualization Investigation 1 Neamkul Yamonbhorn Investigation Writing – Original Draft Preparation 1 Tangsathapornpong Auchara Data Curation 1 Mungkornkaew Narissara Investigation Resources 2 Kulalert Prapasri Formal Analysis Software Validation 3 Department of Pediatrics, Faculty of Medicine, Thammasat University, Amphoe Khlong Laung, Pathum Thani, 12120, Thailand Head of Microbiology Laboratory, Thammasat University Hospital, Amphoe Khlong Luang, Pathum Thani, 12120, Thailand Department of Clinical Epidemiology, Faculty of Medicine, Thammasat University, Amphoe Khlong Luang,, Pathum Thani, 12120, Thailand pornumpa@tu.ac.th

No competing interests were disclosed.

 20 5 2025 2024 13 1269 16 5 2025 Copyright: © 2025 Bunjoungmanee P et al. 2025 This is an open access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background

Acinetobacter baumannii infection (ABI) is a concerning worldwide public health matter with high levels of morbidity and mortality, particularly in critically ill patients. This study aims to assess the prevalence, risk factors, and clinical outcomes of ABI in the pediatric intensive care unit (PICU) setting.

 Methods

A retrospective review was performed on pediatric patients admitted to the PICU over an 8-year period. Demographic characteristics, infection risk factors, and clinical outcomes were compared and analyzed between patients with ABI, determined to be the case group, and patients without ABI, determined to be the control group. The study also assessed the prevalence of ABI and its antimicrobial resistance profile.

 Results

Between June 2014 and May 2022, a total of 82 cases of ABI were identified, resulting in an overall prevalence of 5.02%. After applying the exclusion criteria, 12 cases were excluded. Consequently, 70 ABI cases in total and 140 cases in a control group were included in the study. Multivariable conditional logistic regression analysis identified chronic respiratory disease, mechanical ventilation lasting 5 days or more, and the use of piperacillin/tazobactam within the last 2 weeks as independent risk factors associated with ABI. The rate of carbapenem-resistant A. baumannii (CRAB) was notably high at 94.26%. Cases of ABI were associated with higher mortality rates and prolonged hospitalization compared to non-ABI cases.

 Conclusion

ABI remains a critical pathogen in the PICU. The presence of chronic respiratory disease, use of mechanical ventilation for at least five days, and a history of receiving piperacillin/tazobactam within the last 2 weeks are significant risk factors for ABI. The high level of antibiotic resistance, especially to carbapenems, highlights the emphasis for more stringent infection control practices and the creation of novel antimicrobial therapies.

 Acinetobacter baumannii infection (ABI) pediatric intensive care unit (PICU) carbapenem-resistant Acinetobacter baumannii (CRAB) The author(s) declared that no grants were involved in supporting this work. Amendments from Version 2

Revisions have been made in some parts of the article. The methodology for interpreting tigecycline susceptibility was added, and the data collection process for the non-ABI (control) group was clarified by specifying a defined time frame to ensure appropriate comparison with the ABI (case) group, as described in the Methods section. Furthermore, terminology in Table 1 was revised to accurately reflect the nature of the data presented.

 Introduction

Acinetobacter baumannii causes significant problematic issues in healthcare-associated infections (HAIs). A. baumannii usually causes various infections, including sepsis, pneumonia, meningitis, urinary tract infection, skin and soft tissue infection. 1– 3 The critical factors contributing to the global challenge of A. baumannii in healthcare settings include the pathogen’s capacity to rapidly evolve mechanisms of drug resistance, its ability to persist in the environment, leading to widespread transmission, and the high morbidity and mortality rates of infections. 4– 7 The emergence of pan-antibiotic-resistant A. baumannii and the lack of effective treatments have led to its classification as a serious public health concern. A. baumannii has been designated as an urgent threat, necessitating the development of enhanced therapeutic strategies. 8, 9

Previous studies demonstrated the emergence of A. baumannii infections (ABI) with extremely high rates of carbapenem resistance among adults in Thailand, ranging between 70% to 80%, and mortality rates exceeding 60%. 10– 12 Consequently , ABI is estimated to result in over 15,000 deaths each year. 13 However, there is limited research on A. baumannii in pediatric populations, particularly within intensive care unit (ICU) settings.

Identifying risk factors for ABI are essential for developing targeted prevention strategies. Previous studies, predominantly in adult populations and with limited data from pediatric populations, identified several potential risk factors, including invasive procedures, parenteral nutrition, prior exposure to broad-spectrum antibiotics, age, comorbidities, and ICU length of stay, with reported odds ratios ranging from 1.42 to 10.01. 14 – 22 Nevertheless, many of these studies lacked clarity regarding the duration of exposure to these risk factors, leading to inconsistent findings. Therefore, this study aimed to identify the prevalence and potential risk factors for ABI, focusing on defining the duration of exposure to these risk factors. This aspect remains underexplored, particularly in the pediatric population.

 Methods Ethic statement

This research study received approval from the Human Research Ethics Committee of Thammasat University (Medicine), in accordance with international guidelines, including the Declaration of Helsinki, The Belmont Report, CIOMS Guidelines, and the International Conference on Harmonization-Good Clinical Practice (ICH-GCP). The approval number was MTU-EC-PE-0-125/65 on September 2, 2022. Data collection commenced following the Ethics Committee’s authorization. Informed consent was waived due to the retrospective nature of the study. Data was then collected through the review of patient medical records without any direct participant contact or intervention.

 Study design

The study was a retrospective case-control study of pediatric patients under the age of 15 years at Thammasat University Hospital, a tertiary care facility with an 8-bed pediatric intensive care unit (PICU), from June 2014 and May 2022. All strains of A. baumannii were classified as causative agents of HAIs based on identification in the microbiology laboratory database, meeting the established criteria for significant pathogens.

To identify cases of A. baumannii from PICU, we reviewed culture results from specimens obtained throughout the patients’ hospitalizations. Cases were defined as patients who acquired ABI 48 hours or more following admission to the PICU. Controls were defined as patients admitted to the PICU without ABI. Seventy cases and 140 controls were randomly matched in a 1: 2 ratio. Controls were randomly selected from the same month as cases admitted to the PICU. Patients with A. baumannii identified within the first 48 hours of PICU admission, a PICU stay of less than 5 days, the Pediatric Logistic Organ Dysfunction-2 (PELOD-2) score on the first day at PICU less than 10, 23, 24 or incomplete records were excluded.

A. baumannii was identified and confirmed from the sample using standard microbiological techniques. The susceptibility of the isolates was assessed by determining the minimum inhibitory concentrations following the Clinical and Laboratory Standards Institute (CLSI) guidelines, 25 using the VITEK2 compact system (bioMérieux, France). Colistin susceptibility was assessed using broth microdilution in accordance with CLSI 25 and The European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. 26 Due to the absence of established CLSI interpretive criteria for tigecycline susceptibility in A. baumannii, susceptibility results were interpreted using the CLSI breakpoints for Enterobacteriaceae as an alternative for interpretation. Multidrug-resistant A. baumannii (MDRAB) is defined as isolates exhibiting resistance to at least one agent from three or more antimicrobial classes. Extensively drug-resistant A. baumannii (XDRAB) refers to isolates that demonstrate susceptibility exclusively to tigecycline and colistin, while exhibiting resistance to all other antibiotic classes. Carbapenem-resistant A. baumannii (CRAB) is characterized by nonsusceptibility involving at least one of three agents within the carbapenem class. 27

For procedures potentially associated with ABI, a two-week period prior to discharge from the PICU was defined for the control group. All procedures performed during this timeframe were recorded and analyzed in parallel with those documented in the case group to allow for consistent comparison. Similarly, to compare the duration of PICU stay prior to the development of ABI between groups, the total length of PICU stay was used as a surrogate in the control group, reflecting the corresponding period prior to ABI onset in the case group.

Data collection

This study utilized a systemic computer-assisted database search to obtain retrospective data on patients discharged from the PICU. Information on demographics, clinical outcomes, and microbiological data were gathered from medical and laboratory records.

Data analysis

Categorical variables were presented as frequencies and percentages, whereas continuous variables were given as mean and standard deviation. Non-normally distributed data was expressed as median and interquartile range (IQR). The Rank-Sum test was utilized for non-normally distributed continuous variables and the t-test was applied for comparing normally distributed continuous variable. Chi-square or Fisher’s exact test was utilized to compare categorical data as appropriate. The identification of independent factors associated with ABI was analyzed using univariable and multivariable conditional logistic regression, with statistical significance set at p < 0.05. Statistical analysis was done using STATA version 17.0.

 Results

Throughout the 8-year duration of the study, a total of 1,635 PICU admission were recorded. Eighty-two cases of ABI were identified giving the overall prevalence of 5.02%. Twelve cases were excluded (7 cases with A. baumannii identified within the first 48 hours, 3 cases had a PICU stay of less than 5 days, and 2 cases had incomplete medical data). The remaining ABI were 70 cases. Among them, the percentage of CRAB reached 94.26%. One hundred forty patients with negative A. baumannii specimens who met the matching criteria were included as controls.

Upon analyzing the annual prevalence of ABI in the PICU, the rate exhibited a fluctuating pattern from 2014 to 2022. From 2014 to 2016, the rate remained stable at 3.00, followed by a noticeable increase in 2017 to 4.14. The prevalence peaked in 2018 at 5.94, before slightly declining to 5.22 in 2019. A more significant decrease was observed in 2020 and 2021, with rates dropping to 3.97 and 3.78, respectively. However, in 2022, the prevalence rebounded to 5.4, approaching the 2018 peak. This overall trend suggests periodic fluctuations in ABI, with notable peaks occurring in 2018 and 2022 ( Figure 1).

Prevalence of <italic toggle="yes">Acinetobacter baumannii</italic> infection (ABI) in PICU.

Patients’ clinical characteristics in each group are shown in Table 1. The ABI cases exhibited a younger age, a greater frequency of chronic respiratory disease, and prior mechanical ventilation. Additionally, the use of piperacillin/tazobactam and lengthy hospitalization prior to the onset of ABI tended to be more frequent in this group. Patients with ABI experienced prolonged hospitalization after the onset of infection and demonstrated an increasing mortality rate compared to patients without ABI.

Baseline characteristics of children in pediatric intensive care unit, 2014-2022.
Characteristics ABI case (n=70) Non-ABI case (n=140) p-value
Male, n (%) 42 (60.00) 75 (53.57) 0.658
Age, months, median (IQR) 9.2 (4, 45) 13.5 (8.5, 60) 0.248
Age ≤12 months, n (%) 38 (54.29) 60 (42.86) 0.043 *
Comorbidities, n (%) 43 (61.43) 72 (51.43) 0.557
 Neuromuscular disease 4 (5.71) 18 (12.86) 0.310
 Chronic respiratory disease a 25 (35.71) 20 (14.29) <0.001 *
 Congenital heart disease 34 (48.57) 56 (40.00) 0.324
 Genetic disease 22 (31.43) 40 (28.57) 0.580
 Immunodeficiency b 10 (14.29) 25 (17.86) 0.712
Referral from another hospital (%) 15 (21.43) 31 (22.14) 0.987
Prior hospitalization within 3 months (%) 34 (48.57) 56 (40.00) 0.224
Prior antibiotic use within 3 months (%) 24 (34.29) 35 (25.00) 0.085
The day-1 PELOD-2 score, mean ± SD 13.03 ± 1.59 12.50 ± 1.80 0.781
Broad-spectrum antibiotic c use within the last 2 weeks prior to development ABI, n (%) 70 (100) 126 (90.00) 0.358
 3 rd generation cephalosporin, n (%) 47 (67.14) 100 (71.43) 0.623
 Piperacillin/tazobactam, n (%) 28 (40.00) 29 (20.71) <0.001 *
 Aminoglycoside, n (%) 10 (14.29) 20 (14.29) 1.0
 Carbapenems, n (%) 30 (42.86) 49 (35.00) 0.380
Procedures within 2 weeks prior to development ABI
 Mechanical ventilation n (%) 63 (90.00) 95 (67.86) 0.006 *
 Duration of mechanical ventilation ≥ 5 days, n (%) 38 (60.32) 20 (21.05) <0.001 *
 Central line or arterial line placement, n (%) 64 (91.43) 114 (81.43) 0.430
 Chest drain/Abdominal drain/Pericardial drain, n (%) 20 (28.57) 54 (38.57) 0.091
 HD/ECMO, n (%) 6 (8.57) 16 (11.43) 0.829
Duration of PICU days prior to development of ABI, day (median, IQR) 10 (5, 17) 6 (5, 10) 0.340
Patients with PICU stay > 7 days prior to development of ABI, n (%) 43 (61.43) 62 (44.29) 0.026 *
Outcome
 In hospital mortality, n (%) 11 (15.71) 8 (5.71) 0.009 *
 Total length of hospital stays days (IQR) 40.5 (24, 92) 24 (15, 61) <0.035 *

Abbreviations: PICU, pediatric intensive care unit; ABI, Acinetobacter baumannii infection; non-ABI, non- Acinetobacter baumannii infection; IQR, interquartile range; HD, hemodialysis; ECMO, extracorporeal membrane oxygenation

Statistically significant.

Bronchopulmonary dysplasia (BPD), and asthma.

Hematologic malignancy, on immunosuppressive drug, primary immunodeficiency.

Third-generation cephalosporins, beta-lactam/beta-lactamase inhibitors, aminoglycosides, and carbapenems.

Among patients with ABI, there were 30 cases (42.85%) identified as ventilator-associated pneumonia, 8 cases (11.43%) as bloodstream infections, 6 cases (8.57%) as catheter-related bloodstream infections, 5 cases (7.15%) as skin and soft tissue infections, 2 cases (2.86%) as catheter-associated urinary tract infections, 2 cases (2.86%) as ventricular shunt infections, and 17 cases (24.28%) were identified as having a combination of multiple infection types.

In our study, ABI was associated with a mortality rate of 15.71%. All fatal cases involved patients with at least one comorbidity or a history of major surgical intervention. Of these, two patients had acute leukemia, two had chronic respiratory disease, two had an underlying genetic disorder with airway anomalies, two had congenital heart disease, two had a recent car accident and had undergone major surgery in the past 10 days, and one had a brain tumor with craniotomy in the past two weeks. All cases were complicated by septic shock and multiorgan failure, resulting in fatal outcomes.

Cultures were obtained from 70 cases of ABI. Of these 185 isolates, 142 were from respiratory samples (76.76%), 34 were from blood (18.38%), 5 were from pus (2.70%), and 4 were from urine (2.16%). High co-resistance rates were observed for meropenem (94.26%), imipenem (91.78%), piperacillin-tazobactam (89.46%), ciprofloxacin (88.59%), ceftazidime (88.72%), amikacin (83.45%), and cefoperazone-sulbactam (82.71%). In contrast, low resistance rates were observed for tigecycline (3.48%). All the isolates were susceptible to colistin according to the EUCAST guidelines, 26 while exhibiting intermediate susceptibility to colistin based on the CLSI guidelines. 25 According to the criteria established by Magiorakos et al, 27 most of the isolates were classified as MDRAB (n = 174, 94.05%) and 84.32% were classified as XDRAB (n = 156).

Factors associated with ABI, as determined by both univariable and multivariable conditional logistic regression analysis, are presented in Table 2. In the univariable analysis, the risk factors associated with ABI included being under 12 months of age, chronic respiratory disease, and PICU stay longer than 7 days were significantly associated with ABI. Furthermore, within the last 2 weeks prior to the onset of ABI, mechanical ventilation lasting 5 days or more, and using piperacillin/tazobactam significantly increased the risk of ABI.

Univariable and multivariable conditional logistic regression analysis of risk factors associated with <italic toggle="yes">Acinetobacter baumannii</italic> infection.
Characteristics Univariable analysis Multivariable analysis
Odds ratio 95% CI p-value Odds ratio 95% CI p-value
Age under 12 months 2.06 1.12, 6.17 0.039 *
Chronic respiratory disease a 3.08 2.07, 10.12 0.003 * 2.84 1.12, 16.85 0.036 *
Piperacillin/tazobactam use within 2 weeks prior to development ABI 3.54 1.89, 11.78 0.002 * 2.91 1.05, 12.46 0.048 *
Mechanical ventilation at least 5 days within 2 weeks prior to development ABI 9.86 3.82, 19.42 <0.001 * 6.54 1.98, 20.58 0.002 *
PICU stay longer than 7 days 2.38 1.13, 3.95 0.021 *

Abbreviations: ABI, Acinetobacter baumannii infection; 95% CI, 95% confident interval; PICU, pediatric intensive care unit.

Statistically significant.

Bronchopulmonary dysplasia (BPD), and asthma.

The final multivariable conditional logistic regression analysis identified chronic respiratory disease, mechanical ventilation for 5 days or more within the preceding 2 weeks, and the use of piperacillin/tazobactam within the last 2 weeks as independent factors associated with ABI.

 Discussion

A. baumannii species are emerging as a significant public health threat, frequently exhibiting multidrug resistance and being associated with high mortality rates. An analysis of data collected over eight consecutive years revealed that the overall prevalence of ABI in the PICU was approximately 5.02%. This prevalence is lower than previous studies, which ranged from 8.30% to 15.30%. 28– 30

The prevalence of ABI significantly declined between 2020 and 2021, a period coinciding with the global COVID-19 pandemic. Several studies have reported reductions in ABI rates during this time, with decreases ranging from 1.00% to 3.00%. 31– 34 This reduction is likely associated with widespread lifestyle changes and the emphasis for more stringent practices of infection control aimed at timing the transmission of SARS-CoV-2. These measures contributed to a decline in respiratory infections among children, reduced ICU admissions for non-COVID-19 cases, a reduction in hospitalization rates, and fewer pediatric patients with severe SARS-CoV-2 infections who required PICU admission.

Similar to adults, the major factors related to the emergence and spread of ABI in children, as demonstrated in previous studies, included misguided antimicrobial treatment and prior invasive procedure such as mechanical ventilation, central venous catheterization, and urinary catheters. 1, 35– 37 Our study found that the use of piperacillin-tazobactam, prolonged mechanical ventilation for a minimum of 5 days within the last 2 weeks, and chronic respiratory disease were significantly associated with an increased risk of ABI.

Nowadays, where carbapenems are frequently administered, particularly for the treatment of severe cases, the selective pressure may encourage the emergence and spread of CRAB. As a result, the widespread administration of carbapenems is a potential risk factor of ABI. 6, 38– 40 Differing from previous studies, our study identified piperacillin-tazobactam as a significant risk factor. This difference was attributed to the antibiotic prescribing practices at Thammasat University Hospital.

Piperacillin-tazobactam was widely available and could be prescribed by physicians across various specialties without restriction. Conversely, the use of carbapenem was tightly regulated, requiring authorization from a pediatric infectious disease specialist prior to prescription. As a result, physicians commonly chose piperacillin-tazobactam, a broad-spectrum antibiotic with a similar efficacy profile to carbapenems, particularly for critically ill patients in the PICU. This prescribing pattern likely contributed to the observed association between piperacillin-tazobactam and an increased risk of ABI, which was statistically significant in this study.

Our study is the first to identify chronic respiratory disease, including bronchopulmonary dysplasia (BPD) and asthma, as significant risk factors for ABI. In these patients, the compromised pulmonary architecture and function facilitated bacterial colonization and subsequent infection. Furthermore, these patients often had a history of recurrent hospitalizations and a potential need for mechanical ventilation, both of which contribute to an increased risk of hospital-acquired ABI. Research data in adults demonstrated that chronic obstructive pulmonary disease (COPD) was a significant risk factor for acquiring ABI. 41– 44 These findings underscore the significance of chronic lung conditions in predisposing individuals to ABI across different age groups.

Our study demonstrated that mechanical ventilation lasting 5 days or more within the last 2 weeks was an independent factor associated with ABI. Encouraging non-invasive mechanical ventilation and gradually weaning respiratory support while assessing the necessity for endotracheal intubation, 45 combined with the implementation of targeted antibiotic stewardship program and the reinforcement of rigorous infection control protocols within healthcare setting, 5 can reduce the hospital-acquired pneumonia/ventilator-associated pneumonia (HAP/VAP) and substantially mitigate the risk of ABI.

The rise of CRAB poses a significant challenge to treatment, as therapeutic options become markedly constrained. These resistant strains are associated with higher morbidity and mortality rates and are increasingly recognized as among the most problematic bacterial pathogens. 1, 3, 6, 7, 40, 46 In our study, the prevalence of CRAB reached 94.26%. The presence of CRAB strains is frequently associated with outbreaks in hospital ICU and presents significant challenges to infection control within healthcare settings. 5, 47, 48 To minimize the risk, carbapenems should be used judiciously, and infection control measures should be strictly implemented.

The high mortality rate associated with ABI may be related to the extent of antimicrobial resistance, the efficacy of empirical therapy, and the availability of targeted therapeutic options. The overall mortality rate in our study was 15.71%, consistent with finding from previous studies. 3, 39, 49 However, other studies reported higher mortality rate, ranging from 28.3% to 48.65%. This variation is likely attributable to the inclusion of patients with A. baumannii sepsis, with or without septic shock, and delayed in initiating appropriate antibiotic regimens effective against A. baumannii once the infection was established. 1, 4, 6, 40, 50

A. baumannii is an important threat to patients of all ages, including children. Therefore, ongoing surveillance of ABI in pediatric populations and continuous assessment of effective prevention strategies for at-risk children are essential. The widespread prevalence of antibiotic-resistant A. baumannii strains, combined with the scarcity of new antimicrobial agents, restricts the available therapeutic options. Prioritizing vaccine development against A. baumannii may be regarded as a potential strategy to combat the challenge of antimicrobial resistance in this pathogen moving forward, which is currently under investigation in research studies. 51– 54

Strengths and limitations

The study demonstrates several notable strengths. The extended study period of eight years enables a comprehensive analysis of trends in ABI over time. Focusing on the critically ill pediatric population addresses a significant knowledge gap in understanding the risk factors associated with ABI through multivariable conditional logistic regression analysis and highlights the patterns of antibiotic resistance.

The study had some limitations that should be considered. The retrospective design introduces potential biases. Additionally, being a single-center study limits the generalizability of the findings to other healthcare settings with differing patient demographics and hospital practices. Furthermore, the study lacks detailed genetic analysis, thereby limiting the depth of understanding regarding the genetic mechanisms behind antibiotic resistance.

 Conclusion

This study highlights the significant burden of ABI, particularly carbapenem-resistant strains, in the PICU setting. Prolonged mechanical ventilation for at least 5 days, underlying chronic respiratory disease, and the administration of piperacillin/tazobactam contribute to a higher risk of developing ABI. The findings of our study underscore the importance of the stringent practices of infection control and antibiotic stewardship measures, alongside advocating the use of non-invasive mechanical ventilation in lieu of endotracheal intubation, which can substantially mitigate the risk of ABI. Although the study identifies key risk factors and provides valuable insights into the epidemiology of A. baumannii in the PICU, further research and enhanced infection prevention strategies are necessary to reduce morbidity and mortality related to ABI in critically ill pediatric populations.

 Data availability Underlying data

Zenodo: Prevalence and risk factors of Acinetobacter baumannii infection in Pediatric Intensive Care Unit at Thammasat University Hospital.

The anonymized data sets of this project are available in the Zenado: https://doi.org/10.5281/zenodo.15205332. 55

The project contains the following underlying data:

Data patient case 13042025.xlsx

Data patient control 13042025.xlsx

Data are available under the term of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).

 Reporting guidelines

Zenodo: Prevalence and risk factors of Acinetobacter baumannii infection in Pediatric Intensive Care Unit at Thammasat University Hospital: DOI: https://doi.org/10.5281/zenodo.15205332. 55

The project contains the following checklist:

STROBE checklist for prevalence and risk factors of Acinetobacter baumannii infection in pediatric intensive care unit at Thammasat university hospital

Data are available under the term of the Creative Commons Attribution 4.0 International license (CC-BY 4.0)

 Acknowledgements

The authors thank the Research Group of Pediatrics, the Faculty of Medicine, Thammasat University, for their contributions to the conceptualization and execution of the study. Appreciation is also extended to Ms. Sam Ormond for her meticulous review and editing of the manuscript’s English language.

 References Punpanich W Nithitamsakun N Treeratweeraphong V : Risk factors for carbapenem non-susceptibility and mortality in Acinetobacter baumannii bacteremia in children. Int. J. Infect. Dis. 2012;16(11):e811–e815. 10.1016/j.ijid.2012.07.006 Konca C Tekin M Geyik M : Susceptibility Patterns of Multidrug-Resistant Acinetobacter baumannii. Indian J. Pediatr. 2021;88(2):120–126. 32500488 10.1007/s12098-020-03346-4 PMC7271137 Zhu Y Zhang X Wang Y : Insight into carbapenem resistance and virulence of Acinetobacter baumannii from a children’s medical centre in eastern China. Ann. Clin. Microbiol. Antimicrob. 2022;21(1):47. 36335338 10.1186/s12941-022-00536-0 PMC9637306 Hong Y Lin X Zhang C : Initial indicators for the prognosis of Acinetobacter Baumannii bacteremia in children. BMC Infect. Dis. 2023;23(1):640. 37775747 10.1186/s12879-023-08639-5 PMC10542241 Byun JH Park SE Seo M : Controlling an Outbreak of Multidrug-resistant Acinetobacter baumannii in a Pediatric Intensive Care Unit: a Retrospective Analysis. J. Korean Med. Sci. 2021;36(46):e307. 34845873 10.3346/jkms.2021.36.e307 PMC8629720 Zhang Y Xu G Miao F : Insights into the epidemiology, risk factors, and clinical outcomes of carbapenem-resistant Acinetobacter baumannii infections in critically ill children. Front. Public Health. 2023;11:1282413. 38098829 10.3389/fpubh.2023.1282413 PMC10720883 Castillo Bejarano JI Llaca Díaz J ElOC ME : Carbapenem-Resistant Acinetobacter baumannii Infection in Children From a Third-Level Hospital in Mexico: Clinical Characteristics and Molecular Epidemiology. J. Pediatric Infect. Dis. Soc. 2023;12(7):431–435. 10.1093/jpids/piad046 Talebi Bezmin Abadi A Rizvanov AA Haertlé T : World Health Organization Report: Current Crisis of Antibiotic Resistance. BioNanoScience. 2019;9(4):778–788. 10.1007/s12668-019-00658-4 Centers for Disease Control and Prevention: Carbapenem-resistant Acinetobacter baumannii (CRAB): An urgent public health threat in United States healthcare facilities. Centers for Disease Control and Prevention;2021 [cited 31 Aug 2024]. Hsu LY Apisarnthanarak A Khan E : Carbapenem-Resistant Acinetobacter baumannii and Enterobacteriaceae in South and Southeast Asia. Clin. Microbiol. Rev. 2017;30(1):1–22. 27795305 10.1128/CMR.00042-16 PMC5217790 Suwantarat N Carroll KC : Epidemiology and molecular characterization of multidrug-resistant Gram-negative bacteria in Southeast Asia. Antimicrob. Resist. Infect. Control. 2016;5:15. 27148448 10.1186/s13756-016-0115-6 PMC4855802 Sirijatuphat R Sripanidkulchai K Boonyasiri A : Implementation of global antimicrobial resistance surveillance system (GLASS) in patients with bacteremia. PLoS One. 2018;13(1):e0190132. 29298323 10.1371/journal.pone.0190132 PMC5752004 Lim C Takahashi E Hongsuwan M : Epidemiology and burden of multidrug-resistant bacterial infection in a developing country. elife. 2016;5:e18082. 27599374 10.7554/eLife.18082 PMC5030096 Gandra S Rodrigues C Moser S : The burden of Acinetobacter baumannii infections in an intensive care unit: A single-center study in India. Infect. Control Hosp. Epidemiol. 2021;42(4):448–453. Soltani S Nasiri MJ Fadaei R : Risk factors for infection with Acinetobacter baumannii in intensive care units: A systematic review and meta-analysis. Infect. Dis. 2019;51(9):694–702. Zong Z Lee Y Yoon E : Risk factors for Acinetobacter baumannii infections in patients with mechanical ventilation: A retrospective study in a Korean ICU. Infect. Chemother. 2020;52(4):362–368. Tagliabue C Bonfanti C Gatti M : Parenteral nutrition as a risk factor for Acinetobacter baumannii infections in the ICU: A multicenter observational study. Infect. Control Hosp. Epidemiol. 2020;41(9):1025–1032. Shokouhi S Khosravi A Asgari F : Epidemiology and risk factors for multidrug-resistant Acinetobacter baumannii infection in a tertiary care hospital: A retrospective cohort study. J. Hosp. Infect. 2021;107:101–107. Bassetti M Righi E Tumietto F : Clinical outcomes and risk factors associated with Acinetobacter baumannii infections in a tertiary-care hospital in Italy. J. Infect. Chemother. 2015;21(6):408–413. Goyal R Kaur R Kaur A : Risk factors for Acinetobacter baumannii infection and its association with clinical outcomes in critically ill patients. Microb. Drug Resist. 2016;22(6):488–493. 10.1089/mdr.2015.0233 Sung JY Lee H Lee SY : Insights into the epidemiology, risk factors, and clinical outcomes of carbapenem-resistant Acinetobacter baumannii infections in critically ill children. Pediatr. Infect. Dis. J. 2023;11:1–14. Kim J Lee Y Ryu H : Risk factors for mortality in children with Acinetobacter baumannii bacteremia in South Korea: The role of carbapenem resistance. Microb. Drug Resist. 2019 Oct;25(8):1210–1218. 10.1089/mdr.2018.0465 Leteurtre S Duhamel A Salleron J : PELOD-2: An Update of the PEdiatric Logistic Organ Dysfunction Score. Crit. Care Med. 2013;41(7):1761–1773. 10.1097/CCM.0b013e31828a2bbd López MPA Prata-Barbosa A Lima-Setta F : Severity of illness scores in the pediatric intensive care unit: a practical guide. Crit. Care Sci. 2024;36:e20240205en. 10.62675/2965-2774.20240205-en Clinical and Laboratory Standards Institute (CLSI): Performance Standards for Antimicrobial Susceptibility Testing. 32nd ed. CLSI supplement M100. Clinical and Laboratory Standards Institute;2022. The European Committee on Antimicrobial Susceptibility Testing (EUCAST): Breakpoint tables and dosages v 12.0. 2022. published. Reference Source Magiorakos AP Srinivasan A Carey RB : Multidrug-resistant, extensively drug-resistant and pandrug-resistant bacteria: an international expert proposal for interim standard definitions for acquired resistance. Clin. Microbiol. Infect. 2012;18(3):268–281. 10.1111/j.1469-0691.2011.03570.x Katragkou A Kotsiou M Antachopoulos C : Acquisition of imipenem-resistant Acinetobacter baumannii in a pediatric intensive care unit: A case-control study. Intensive Care Med. 2006;32(9):1384–1391. 10.1007/s00134-006-0239-x Le NK Hf W Vu PD : High prevalence of hospital-acquired infections caused by gram-negative carbapenem resistant strains in Vietnamese pediatric ICUs: A multi-centre point prevalence survey. Medicine (Baltimore). 2016;95(27):e4099. 27399106 10.1097/MD.0000000000004099 PMC5058835 Asanathong NW Rongrungreung Y Assanasen S : Epidemiology and trends of important pediatric healthcare-associated infections at siriraj hospital, Thailand. Southeast Asian J. Trop. Med. Public Health. 2017;48:641–654. Ripa M Galli L Poli A : Secondary infections in patients hospitalized with COVID-19: incidence and predictive factors. Clin. Microbiol. Infect. 2021;27(3):451–457. 33223114 10.1016/j.cmi.2020.10.021 PMC7584496 Chen N Zhou M Dong X : Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study. Lancet. 2020;395(10223):507–513. 32007143 10.1016/S0140-6736(20)30211-7 PMC7135076 Contou D Claudinon A Pajot O : Bacterial and viral co-infections in patients with severe SARS-CoV-2 pneumonia admitted to a French ICU. Ann. Intensive Care. 2020;10(1):119. 32894364 10.1186/s13613-020-00736-x PMC7475952 Yang S Hua M Liu X : Bacterial and fungal co-infections among COVID-19 patients in intensive care unit. Microbes Infect. 2021;23(4):104806. 33684520 10.1016/j.micinf.2021.104806 PMC7933791 Kim B Kim K Yoon JS : Nosocomial Acinetobacter baumannii infection in children in adult versus pediatric intensive care units. Pediatr. Int. 2020;62(4):451–458. 10.1111/ped.14133 Prashanth K Badrinath S : Nosocomial infections due to Acinetobacter species: Clinical findings, risk and prognostic factors. Indian J. Med. Microbiol. 2006;24(1):39–44. 10.1016/S0255-0857(21)02469-5 Liu C Chen K Wu Y : Epidemiological and genetic characteristics of clinical carbapenem-resistant Acinetobacter baumannii strains collected countrywide from hospital intensive care units (ICUs) in China. Emerg. Microbes Infect. 2022;11(1):1730–1741. 35730377 10.1080/22221751.2022.2093134 PMC9258068 Logan LK Gandra S Trett A : Acinetobacter baumannii Resistance Trends in Children in the United States, 1999-2012. J. Pediatric Infect. Dis. Soc. 2019;8(2):136–142. 29579216 10.1093/jpids/piy018 PMC6510944 Elvan Tüz A Tekin D Ekemen Keleş Y : Clinical Reflections of Acinetobacter Infections in Children in a Quaternary-Care Hospital: A Five-Year Single-Center Experience. Turk. Arch. Pediatr. 2024;59(1):38–42. 38454258 10.5152/TurkArchPediatr.2024.23153 PMC10837592 Kim D Lee H Choi JS : The Changes in Epidemiology of Imipenem-Resistant Acinetobacter baumannii Bacteremia in a Pediatric Intensive Care Unit for 17 Years. J. Korean Med. Sci. 2022;37(24):e196. 35726147 10.3346/jkms.2022.37.e196 PMC9247723 Chang KY Wu PC Lee CH : Clinical Features and Antimicrobial Susceptibility of Pseudomonas aeruginosa and Acinetobacter baumannii Complex Isolates in Intensive Care Patients with Chronic Obstructive Pulmonary Disease and Community-Acquired Pneumonia in Taiwan. Int. J. Chron. Obstruct. Pulmon. Dis. 2021;16:1801–1811. 34168441 10.2147/COPD.S311714 PMC8216665 Grochowalska A Kozioł-Montewka M Sobieszczańska A : Analysis of Acinetobacter baumannii resistance patterns in patients with chronic obstructive pulmonary disease (COPD) in terms of choice of effective empiric antibiotic therapy. Ann. Agric. Environ. Med. 2017;24(2):307–311. 10.26444/aaem/74710 Chen L He X Li T : Pathogenic bacteria for exacerbation of Chronic Obstructive Pulmonary Disease. Eur. Respir. J. 2018;52(suppl 62):PA4099. Khilnani GC Dubey D Hadda V : Predictors and microbiology of ventilator-associated pneumonia among patients with exacerbation of chronic obstructive pulmonary disease. Lung India. 2019;36(6):506. 10.4103/lungindia.lungindia_13_19 Klompas M Branson R Cawcutt K : Strategies to prevent ventilator-associated pneumonia, ventilator-associated events, and nonventilator hospital-acquired pneumonia in acute-care hospitals: 2022 Update. Infect. Control Hosp. Epidemiol. 2022;43(6):687–713. 35589091 10.1017/ice.2022.88 PMC10903147 Hasan B Perveen K Olsen B : Emergence of carbapenem-resistant Acinetobacter baumannii in hospitals in Pakistan. J. Med. Microbiol. 2014;63(Pt 1):50–55. 10.1099/jmm.0.063925-0 Risser C Pottecher J Launoy A : Management of a Major Carbapenem-Resistant Acinetobacter baumannii Outbreak in a French Intensive Care Unit While Maintaining Its Capacity Unaltered. Microorganisms. 2022;10(4):720. 35456771 10.3390/microorganisms10040720 PMC9031073 Doughty EL Liu H Moran RA : Endemicity and diversification of carbapenem-resistant Acinetobacter baumannii in an intensive care unit. Lancet Reg. Health West Pac. 2023;37:100780. 10.1016/j.lanwpc.2023.100780 Vandepitte WP Berge J Andersson R : Clinical outcomes of children with carbapenem-resistant Acinetobacter baumannii bacteremia. J. Med. Assoc. Thail. 2014;97 Suppl 11:S129–S139. Taşkın E : Acinetobacter infections in pediatric intensive care unit: A single-center experience. Ümraniye Pediatri Dergisi - Journal of Umraniye Pediatrics. 2024;4(1):39–46. 10.14744/upd.2024.13008 Elbehiry A Marzouk E Moussa I : The Prevalence of Multidrug-Resistant Acinetobacter baumannii and Its Vaccination Status among Healthcare Providers. Vaccines (Basel). 2023;11(7). 10.3390/vaccines11071171 Tan YC Lahiri C : Promising Acinetobacter baumannii Vaccine Candidates and Drug Targets in Recent Years. Front. Immunol. 2022;13:900509. 35720310 10.3389/fimmu.2022.900509 PMC9204607 Yang N Jin X Zhu C : Subunit vaccines for Acinetobacter baumannii. Front. Immunol. 2022;13:1088130. Piri-Gharaghie T Doosti A Mirzaei SA : Novel adjuvant nano-vaccine induced immune response against Acinetobacter baumannii. AMB Express. 2023;13(1):31. 36905472 10.1186/s13568-023-01531-0 PMC10008545 Bunjoungmanee P Tangsathapornpong A Kulalert P : Prevalence and risk factors of Acinetobacter baumannii infection in Pediatric Intensive Care Unit at Thammasat University Hospital. Zenodo. 2024. 10.5281/zenodo.15205332 10.5256/f1000research.182195.r386111 Reviewer response for version 3 Wacharachaisurapol Noppadol 1 Referee https://orcid.org/0000-0002-1499-6940 Chulalongkorn University, Bangkok, Thailand

Competing interests: No competing interests were disclosed.

 30 5 2025 Copyright: © 2025 Wacharachaisurapol N 2025 This is an open access peer review report distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. recommendation approve

Thank you for the revised manuscript and detailed responses. I am satisfied with the authors' clarifications and revisions. I have no further comments or suggestions.

Is the work clearly and accurately presented and does it cite the current literature?

Partly

If applicable, is the statistical analysis and its interpretation appropriate?

I cannot comment. A qualified statistician is required.

Are all the source data underlying the results available to ensure full reproducibility?

Yes

Is the study design appropriate and is the work technically sound?

Yes

Are the conclusions drawn adequately supported by the results?

Yes

Are sufficient details of methods and analysis provided to allow replication by others?

Partly

Reviewer Expertise:

Pediatric infectious diseases; antimicrobial pharmacokinetics

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

 10.5256/f1000research.181112.r381841 Reviewer response for version 2 Wacharachaisurapol Noppadol 1 Referee https://orcid.org/0000-0002-1499-6940 Chulalongkorn University, Bangkok, Thailand

Competing interests: No competing interests were disclosed.

 13 5 2025 Copyright: © 2025 Wacharachaisurapol N 2025 This is an open access peer review report distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. recommendation approve-with-reservations

Article: “Prevalence and risk factors of Acinetobacter baumannii infection in Pediatric Intensive Care Unit at Thammasat University Hospital”

Thank you for the revised manuscript and your detailed responses. I have a few additional comments and suggestions for your consideration:

Methods

Please clarify how tigecycline susceptibility was evaluated, given that there are no established MIC breakpoints for A. baumannii from either CLSI or EUCAST.

Results

Table 1

It remains unclear how data were obtained for the non-ABI group, considering that no ABI events occurred in this group. Kindly clarify in the Methods section how the following characteristics were defined or collected:

Broad-spectrum antibiotic use within the last 2 weeks prior to the development of ABI

Procedures within 2 weeks prior to the development of ABI

Duration of PICU days prior to the development of ABI

Duration of PICU days > 7 days prior to development of ABI, n (%)

Additionally, please reconsider the use of the term “duration” here, as the result is presented as n (%). If you are referring to the proportion of patients who had PICU stays longer than 7 days before developing ABI, please revise the wording accordingly.

Length of hospital stays after A. baumannii isolated

The results were 40.5 days (ABI group) and 24 days (non-ABI group). Please clarify whether these results represent the total length of hospital stay, which I believe they do, or only the duration following A. baumannii isolation.

Is the work clearly and accurately presented and does it cite the current literature?

Partly

If applicable, is the statistical analysis and its interpretation appropriate?

I cannot comment. A qualified statistician is required.

Are all the source data underlying the results available to ensure full reproducibility?

Yes

Is the study design appropriate and is the work technically sound?

Yes

Are the conclusions drawn adequately supported by the results?

Yes

Are sufficient details of methods and analysis provided to allow replication by others?

Partly

Reviewer Expertise:

Pediatric infectious diseases; antimicrobial pharmacokinetics

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

Bunjoungmanee Pornumpa pediatric, Thammasat University, Pathum Thani, Thailand

Competing interests: No competing interests were disclosed.

 16 5 2025

We are grateful for your appreciation of the work and constructive comments/ suggestions to improve the quality of the manuscript. We have pasted your comments below, in bold, with responses in turn.

: Please clarify how tigecycline susceptibility was evaluated, given that there are no established MIC breakpoints for A. baumannii from either CLSI or EUCAST.

Ans.  Due to the lack of established guidelines for interpreting tigecycline susceptibility against Acinetobacter baumannii, the laboratory currently utilizes the CLSI criteria for Enterobacteriaceae as an alternative for interpretation. This information has been included in the Methods section.

: It remains unclear how data were obtained for the non-ABI group, considering that no ABI events occurred in this group. Kindly clarify in the Methods section how the following characteristics were defined or collected:

Broad-spectrum antibiotic use within the last 2 weeks prior to the development of ABI

Procedures within 2 weeks prior to the development of ABI

Duration of PICU days prior to the development of ABI

Duration of PICU days > 7 days prior to development of ABI, n (%)

Ans .  Additional information regarding data collection for the control group, intended for comparison with the case group, was provided, with definitions specified in the Methods section (page 3).

: Additionally, please reconsider the use of the term “duration” here, as the result is presented as n (%). If you are referring to the proportion of patients who had PICU stays longer than 7 days before developing ABI, please revise the wording accordingly.

Ans. The terms have been revised to align with the recommendations, as shown in Table 1.

: Length of hospital stays after A. baumannii isolated

The results were 40.5 days (ABI group) and 24 days (non-ABI group). Please clarify whether these results represent the total length of hospital stay, which I believe they do, or only the duration following A. baumannii isolation.

Ans  The terms have been revised to align with the recommendations, as shown in Table 1.

10.5256/f1000research.181112.r381842 Reviewer response for version 2 Moolasart Visal 1 Referee https://orcid.org/0000-0002-1151-4790 Department of Disease Control, Bamrasnaradura Infectious Diseases Institute, Ministry of Public Health, Nonthaburi, Thailand

Competing interests: No competing interests were disclosed.

 5 5 2025 Copyright: © 2025 Moolasart V 2025 This is an open access peer review report distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. recommendation approve

I am satisfied with the revised version of the manuscript and acknowledge the limitations of this study, including its retrospective design, single-center setting, and small sample size.

Is the work clearly and accurately presented and does it cite the current literature?

Partly

If applicable, is the statistical analysis and its interpretation appropriate?

Partly

Are all the source data underlying the results available to ensure full reproducibility?

Yes

Is the study design appropriate and is the work technically sound?

Partly

Are the conclusions drawn adequately supported by the results?

Partly

Are sufficient details of methods and analysis provided to allow replication by others?

Partly

Reviewer Expertise:

infectious, HIV EID IPC and children

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

 10.5256/f1000research.173078.r365254 Reviewer response for version 1 Wacharachaisurapol Noppadol 1 Referee https://orcid.org/0000-0002-1499-6940 Chulalongkorn University, Bangkok, Thailand

Competing interests: No competing interests were disclosed.

 18 2 2025 Copyright: © 2025 Wacharachaisurapol N 2025 This is an open access peer review report distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. recommendation approve-with-reservations

Article: "Prevalence and risk factors of Acinetobacter baumannii infection in Pediatric Intensive Care Unit at Thammasat University Hospital"

This work provides valuable information on the prevalence, risk factors, and clinical outcomes of ABI in the PICU setting. The paper is well organized; however, some clarifications may improve it.

SPECIFIC RECOMMENDATIONS

Introduction

Page 3:

The authors mention limited research on A. baumannii infections in pediatric ICUs, but some studies exist. For context, it would be helpful to summarize previously reported risk factors and clinical outcomes in adults and/or in PICU settings.

Methods

Page 3:

Controls were defined as patients admitted to the PICU without ABI.

Please describe any matching criteria used for controls.

Please clarify the indications for PICU admission in controls to ensure comparability with cases. For instance, whether controls had other MDRO infections or were admitted for non-infectious conditions, as patients admitted solely for postoperative monitoring may have a lower mortality risk.

Results

Page 4-5: Table 1

Several characteristics (e.g., broad-spectrum antibiotic use within the last 2 weeks) are described as occurring "prior to ABI development." For controls, prior to what event were these characteristics assessed regarding no ABI in this group?

Please clarify in the methods the rationale for selecting a 2-week cutoff for characteristics like antibiotic use and procedures.

Please include the total number (%) of patients with comorbidities to provide an overall perspective before listing specific conditions.

The denominators for mechanical ventilation ≥ 3 days appear to be 70 and 140, though they likely represent subgroups of ventilated patients. If so, the denominators should be 63 and 75 (only those on mechanical ventilation) to ensure accurate proportions.

 Page 5:

The study states that tigecycline resistance was low (3.21%), but CLSI and EUCAST do not provide breakpoints for this drug. Please clarify how resistance was determined or which breakpoint was used.

Is the work clearly and accurately presented and does it cite the current literature?

Partly

If applicable, is the statistical analysis and its interpretation appropriate?

I cannot comment. A qualified statistician is required.

Are all the source data underlying the results available to ensure full reproducibility?

Yes

Is the study design appropriate and is the work technically sound?

Yes

Are the conclusions drawn adequately supported by the results?

Yes

Are sufficient details of methods and analysis provided to allow replication by others?

Partly

Reviewer Expertise:

Pediatric infectious diseases; antimicrobial pharmacokinetics

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

Bunjoungmanee Pornumpa pediatric, Thammasat University, Pathum Thani, Thailand

Competing interests: No competing interests were disclosed.

 24 4 2025

 Thank you Dr. Noppadol Wacharachaisurapol for your valuable time and interest for reviewing

this work and for the detailed feedback and recommendations for improving this manuscript.

We have pasted your comments below, in bold, with responses in turn.

 

The authors mention limited research on A. baumannii infections in pediatric ICUs, but some studies exist. For context, it would be helpful to summarize previously reported risk factors and clinical outcomes in adults and/or in PICU settings.

     Ans

          A comprehensive overview of the risk factors for Acinetobacter baumannii infection in both adult and pediatric populations has been provided in the background section.

      2. Page 3

          : Please describe any matching criteria used for controls.

          Ans

          In the initial version of the article, cases and controls were selected from patients admitted to the pediatric intensive care unit (PICU) during the same period, with a minimum stay of 48 hours. Random matching was conducted in a 1:2 ratio. The exclusion criteria included pediatric patients whose culture reported grew Acinetobacter baumannii within 48 hours of PICU admission or those with incomplete medical records. However, this approach posed a risk of potential confounding.

          To address this issue, additional exclusion criteria were included: a minimum Pediatric Logistic Organ Dysfunction-2 (PELOD-2) score of 10 and an extended minimum PICU stay of 120 hours. These modifications were implemented to reduce confounding in the selection of case and control groups. A PELOD-2 score of ≥10 is considered a medium score, and is associated with an estimated mortality risk of approximately 10%. 1-2 The researchers consider this threshold appropriate for identifying patients eligible to participate in the study.

     Reference

Leteurtre S, Duhamel A, Salleron J, et al. PELOD-2: An Update of the PEdiatric Logistic Organ Dysfunction Score. Crit Care Med. 2013;41(7):1761-73.

López MPA, Prata-Barbosa A, Lima-Setta F. Severity of illness scores in the pediatric intensive care unit: a practical guide. Crit Care Sci. 2024 Oct 11;36:e20240205en.

           : Please clarify the indications for PICU admission in controls to ensure comparability with cases. For instance, whether controls had other MDRO infections or were admitted for non-infectious conditions, as patients admitted solely for postoperative monitoring may have a lower mortality risk.

   

           Ans

          The exclusion criteria were modified to mitigate confounding factors resulting from the selection of an inappropriate control group. As a result, an additional criterion was implemented: all study participants must have a PELOD score of 10 or higher upon admission to the intensive care unit and a minimum PICU admission duration of 120 hours.

     3. Table 1

          : Several characteristics (e.g., broad-spectrum antibiotic use within the last 2 weeks) are described as occurring "prior to ABI development." For controls, prior to what event were these characteristics assessed regarding no ABI in this group?

          Ans

          In the control group, the researchers collected data on antibiotic administration throughout the patient's hospitalization in the intensive care unit during the 2 weeks of the patient's admission to the PICU. If the patient’s stay exceeded 2 weeks, antibiotic data was recorded based on the antibiotics received within 2 weeks prior to transfer out of the ICU.

            : Please clarify in the methods the rationale for selecting a 2-week cutoff for characteristics like antibiotic use and procedures.

            Ans

            Previous studies have mostly not specified the duration of antibiotic administration or procedures prior to the acquisition of Acinetobacter baumannii infection or its correlation. They generally only mention a history of receiving broad-spectrum antibiotics or undergoing procedures. Therefore, the researchers aim to investigate and compare the duration of broad-spectrum antibiotic use or procedures performed before the risk of Acinetobacter baumannii infection increases. A 2-week cutoff is based on previous studies indicating that the use of broad-spectrum antibiotics or procedures performed for approximately 1-2 weeks is associated with an increased risk of Acinetobacter baumannii infection.

Reference

Xu, N. N., Wang, H., and Zhou, M. (2019a). Analysis of risk factors and prevention strategies of extensive drug- resistant Acinetobacter baumannii infection and colonization in patients with mechanical ventilation.  J. Hosp. Infect. 92, 47–53.

Shihan Zhang, et al. An integrative review on the risk factors, prevention, and control strategies for carbapenem-resistant Acinetobacter baumannii colonization in critically ill patients. Front Microbiol 2023.10:15:1519906.

Beavers SF, et al. Comparison of risk factors for recovery of Acinetobacter baumannii during outbreaks at two Kentucky hospitals, 2006. Public Health Rep. 2009 Nov-Dec;124(6):868-74.

Hong Y, et al. Initial indicators for the prognosis of Acinetobacter baumannii bacteremia in children. BMC Infect Dis. 2023 Sep 29;23(1):640. 

            : Please include the total number (%) of patients with comorbidities to provide an overall perspective before listing specific conditions.

            Ans

            The information has been updated following the recommendations

            : The denominators for mechanical ventilation ≥ 3 days appear to be 70 and 140, though they likely represent subgroups of ventilated patients. If so, the denominators should be 63 and 75 (only those on mechanical ventilation) to ensure accurate proportions.

             Ans

            The information has been updated following the recommendations.

          4. Page 5

             : The study states that tigecycline resistance was low (3.21%), but CLSI and EUCAST do not provide breakpoints for this drug. Please clarify how resistance was determined or which breakpoint was used.

             Ans

             Due to the lack of established guidelines for interpreting tigecycline susceptibility against Acinetobacter baumannii, the laboratory currently utilizes the CLSI criteria for Enterobacteriaceae as an alternative for interpretation same as the previous studies.

Reference

Kim D, et al. The Changes in Epidemiology of Imipenem-Resistant Acinetobacter baumannii Bacteremia in a Pediatric Intensive Care Unit for 17 Years. J Korean Med Sci. 2022 Jun 8;37(24):e196.

Bejarano JIC, et al. Carbapenem-Resistant Acinetobacter baumannii Infection in Children From a Third-Level Hospital in Mexico: Clinical Characteristics and Molecular Epidemiology. J Pediatric Infect Dis Soc. 2023 Jul 31;12(7):431-435

Zhu Y, et al. Insight into carbapenem resistance and virulence of Acinetobacter baumannii from a children's medical centre in eastern China. Ann Clin Microbiol Antimicrob. 2022 Nov 5;21(1):47.

Fang C, er al. Epidemiology and Cytokine Levels among Children with Nosocomial Multidrug-Resistant Acinetobacter baumannii Complex in a Tertiary Hospital of Eastern China. PLoS One. 2016 Aug 31;11(8):e0161690.

10.5256/f1000research.173078.r342361 Reviewer response for version 1 Moolasart Visal 1 Referee https://orcid.org/0000-0002-1151-4790 Department of Disease Control, Bamrasnaradura Infectious Diseases Institute, Ministry of Public Health, Nonthaburi, Thailand

Competing interests: No competing interests were disclosed.

 22 11 2024 Copyright: © 2024 Moolasart V 2024 This is an open access peer review report distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. recommendation approve-with-reservations

This manuscript presents a compelling message and provides valuable insights into the "Prevalence and Risk Factors of Acinetobacter baumannii Infection in the Pediatric Intensive Care Unit at Thammasat University Hospital." However, there are several issues that merit further consideration.

1. This case-control study compares the risk factors for Acinetobacter baumannii infections with those for non- Acinetobacter baumannii infections (control group). While the information provided is valuable, further consideration of several issues is necessary, such as the selection criteria and characteristics of the control group, potential confounding factors, and the robustness of the data analysis.

        -A study by Uwingabiye J et al reported that Acinetobacter baumannii accounted for 22.6% of infections in the ICU. In several study, the mortality rate associated with A. baumannii infections ranges from 26.5% to 91%, reaching as high as 70% for infections caused by resistant strains. These findings highlight the severity of cases involving A. baumannii.

      - The selection of a control group is a critical aspect of case-control study design . In this study, the control group was defined as patients with non- Acinetobacter baumannii infections, representing less severe cases with fewer underlying conditions. To address this issue, the authors might consider selecting a more appropriate control group for comparison. For example, other studies have compared children with carbapenem-resistant A. baumannii (CRAB) infections to those with carbapenem-susceptible A. baumannii (CSAB) infections, which could provide a more balanced and clinically relevant comparison.

       The authors may consider matching the control group by adding specific conditions to ensure appropriate integration and analysis. This approach could help create a more balanced comparison and improve the validity of the findings.

 2. Case group : The Acinetobacter baumannii group is divided into two subgroups: resistant and non-resistant strains. Please consider this distinction, as several factors may differ between these subgroups and could influence the analysis and outcomes.

3. If the authors intend to compare two groups for factor analysis, they should consider the sample size in each group to ensure sufficient statistical power and reliable results.

4. This information demonstrated” Upon analyzing the annual prevalence of ABI in the PICU, the rate exhibited a fluctuating pattern from 2014 to 2022. From 2014 to 2016, the rate remained stable at 3.00, followed by a noticeable increase in 2017 to 4.14. The prevalence peaked in 2018 at 5.94, before slightly declining to 5.22 in 2019. A more significant decrease was observed in 2020 and 2021, with rates dropping to 3.97 and 3.78, respectively. However, in 2022, the prevalence rebounded to 5.4, approaching the 2018 peak. This overall trend suggests periodic fluctuations in ABI, with notable peaks occurring in 2018 and 2022.”

      This data is interesting and valuable for integration and analysis in this study. To further enhance the manuscript, consider incorporating graphs or illustrations to better visualize the findings, along with a more in-depth discussion to provide additional context and insights.  

5. Please include additional information in the background section, focusing on key risk factors and reviewing relevant statistics. This will help readers better understand the context and significance of the findings.

6. A discussion on drug resistance should also be included as part of the result and analysis. Lastly, ensure that a section on the limitations of the study is added to provide a more comprehensive view of the research.

Is the work clearly and accurately presented and does it cite the current literature?

Partly

If applicable, is the statistical analysis and its interpretation appropriate?

Partly

Are all the source data underlying the results available to ensure full reproducibility?

Yes

Is the study design appropriate and is the work technically sound?

Partly

Are the conclusions drawn adequately supported by the results?

Partly

Are sufficient details of methods and analysis provided to allow replication by others?

Partly

Reviewer Expertise:

infectious, HIV EID IPC and children

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

Bunjoungmanee Pornumpa pediatric, Thammasat University, Pathum Thani, Thailand

Competing interests: No competing interests were disclosed.

 24 4 2025

Thank you very much for your thoughtful review and valuable suggestions, which have significantly contributed to improving the quality of our manuscript. For clarity, we have included your original comments below, followed by our point-by-point responses in bold.

1. This case-control study compares the risk factors for Acinetobacter baumannii infections with those for non- Acinetobacter baumannii infections (control group). While the information provided is valuable, further consideration of several issues is necessary, such as the selection criteria and characteristics of the control group, potential confounding factors, and the robustness of the data analysis.

        -A study by Uwingabiye J et al reported that Acinetobacter baumannii accounted for 22.6% of infections in the ICU. In several study, the mortality rate associated with A. baumannii infections ranges from 26.5% to 91%, reaching as high as 70% for infections caused by resistant strains. These findings highlight the severity of cases involving A. baumannii.

      - The selection of a control group is a critical aspect of case-control study design. In this study, the control group was defined as patients with non- Acinetobacter baumannii infections, representing less severe cases with fewer underlying conditions. To address this issue, the authors might consider selecting a more appropriate control group for comparison. For example, other studies have compared children with carbapenem-resistant A. baumannii (CRAB) infections to those with carbapenem-susceptible A. baumannii (CSAB) infections, which could provide a more balanced and clinically relevant comparison.

       The authors may consider matching the control group by adding specific conditions to ensure appropriate integration and analysis. This approach could help create a more balanced comparison and improve the validity of the findings.

Ans:

     In the initial version of the article, cases and controls were selected from patients admitted to the pediatric intensive care unit (PICU) during the same period, with a minimum stay of 48 hours. Random matching was conducted in a 1:2 ratio. The exclusion criteria included pediatric patients whose culture reported grew Acinetobacter baumannii within 48 hours of PICU admission or those with incomplete medical records. However, this approach posed a risk of potential confounding.

To address this issue, additional exclusion criteria were included: a minimum Pediatric Logistic Organ Dysfunction-2 (PELOD-2) score of 10 and an extended minimum PICU stay of 120 hours. These modifications were implemented to reduce confounding in the selection of case and control groups. A PELOD-2 score of ≥10 is considered a medium score, and is associated with an estimated mortality risk of approximately 10%. 1-2 The researchers consider this threshold appropriate for identifying patients eligible to participate in the study.

Reference

Leteurtre S, Duhamel A, Salleron J, et al. PELOD-2: An Update of the PEdiatric Logistic Organ Dysfunction Score. Crit Care Med. 2013;41(7):1761-73.

López MPA, Prata-Barbosa A, Lima-Setta F. Severity of illness scores in the pediatric intensive care unit: a practical guide. Crit Care Sci. 2024 Oct 11;36:e20240205en.

2. Case group: The Acinetobacter baumannii group is divided into two subgroups: resistant and non-resistant strains. Please consider this distinction, as several factors may differ between these subgroups and could influence the analysis and outcomes.

Ans

     In this study, Acinetobacter baumannii exhibited a carbapenem resistance rate of 94.26%, whereas the non-resistant group accounted for only 6.78%. As a result, the sample sizes for comparison were insufficient, limiting the ability to perform a valid comparative analysis.

3. If the authors intend to compare two groups for factor analysis, they should consider the sample size in each group to ensure sufficient statistical power and reliable results.

Ans

    Previous studies investigating Acinetobacter baumannii infections in the pediatric intensive care unit (PICU) have reported prevalence rates ranging from 10% to 20%. Notable studies include:

     Katragkou A. et al., who conducted a study in the pediatric ICU in Greece from July 2001 to December 2003, reporting a prevalence of A. baumannii infection at 10.20%.

     Reddy D. et al., who studied the pediatric ICU in South Africa in 2010 and found a prevalence of A. baumannii infection at 15.30%.

     In this study, the estimated prevalence of A. baumannii infection in the pediatric ICU is consistent with prior reports, ranging from approximately 10% to 20%.

     The sample size calculation was performed using the one-sample comparison of proportions formula in STATA version 14. The study was designed with a power of 90%, an alpha value of 0.05, and a two-sided test. A p-value of less than 0.05 was considered statistically significant. Based on the calculation in STATA, a minimum of 169 patients were required for inclusion. Given that a potential data collection deviation of approximately 20% might occur, the total number of participants included in the study was 210 individuals. The sample was selected using concurrent control sampling at a case-to-control ratio of 1:2, with randomization conducted via computer. Accordingly, the study included 70 cases and 140 controls.

4. This information demonstrated” Upon analyzing the annual prevalence of ABI in the PICU, the rate exhibited a fluctuating pattern from 2014 to 2022. From 2014 to 2016, the rate remained stable at 3.00, followed by a noticeable increase in 2017 to 4.14. The prevalence peaked in 2018 at 5.94, before slightly declining to 5.22 in 2019. A more significant decrease was observed in 2020 and 2021, with rates dropping to 3.97 and 3.78, respectively. However, in 2022, the prevalence rebounded to 5.4, approaching the 2018 peak. This overall trend suggests periodic fluctuations in ABI, with notable peaks occurring in 2018 and 2022.”

      This data is interesting and valuable for integration and analysis in this study. To further enhance the manuscript, consider incorporating graphs or illustrations to better visualize the findings, along with a more in-depth discussion to provide additional context and insights. 

Ans

     A graph  has been incorporated into the study as per the recommendations. A detailed discussion of the changes in prevalence over the years has been included in the Discussion section.

5. Please include additional information in the background section, focusing on key risk factors and reviewing relevant statistics. This will help readers better understand the context and significance of the findings.

Ans

     A comprehensive overview of the risk factors for Acinetobacter baumannii infection in both adult and pediatric populations has been provided in the background section of the manuscript.

6. A discussion on drug resistance should also be included as part of the result and analysis. Lastly, ensure that a section on the limitations of the study is added to provide a more comprehensive view of the research.

Ans

      The antimicrobial resistance profile of Acinetobacter baumannii was presented in the results section, and the reasons for the resistance were discussed in the discussion section. Additionally, the limitations of the study were addressed in the strengths and limitations section.