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Research Article

Identification of predictive factors for surgical site infections in gastrointestinal surgeries: A retrospective cross-sectional study in a resource-limited setting

[version 1; peer review: 1 approved with reservations]
PUBLISHED 23 Jun 2023
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Abstract

Background: Surgical site infection (SSI), albeit infrequent, drastically impact the quality of care. This article endeavors to investigate the predictive factors of SSIs following surgical interventions that involve the gastrointestinal (GI) tract within a single institution in a resource-limited setting.
Methods: Over seven years from June 2015 to Oct 2022, patients who underwent GI surgery and developed SSI were retrospectively matched with an unaffected case-control cohort of patients. Standardized techniques for wound culture, laboratory evaluation of bacterial isolates, and antibiotic susceptibility tests were employed. Logistic regression analysis was utilized to investigate the predictive factors associated with 30-day postoperative SSI.
Results: A total of 525 patients who underwent GI surgical procedures were included, among whom, 79 (15%) developed SSI. The majority of SSIs were superficial (67.10%), Escherichia coli was the most commonly isolated bacterium (54.4%), and a high percentage of multidrug-resistant organisms were observed (63.8%). In multivariate Cox regression analysis, illiteracy (Odds ratio [OR]:40.31; 95% confidence interval [CI]: 9.54-170.26), smoking (OR: 21.15; 95% CI: 4.63-96.67), diabetes (OR: 5.07; 95% CI: 2.27-11.35), leukocytosis (OR: 2.62; 95% CI: 1.24-5.53), hypoalbuminemia (OR: 3.70; 95% CI: 1.35-10.16), contaminated and dirty wounds (OR: 6.51; 95% CI:1.62-26.09),  longer operative time (OR: 1.02; 95% CI: 1.01-1.03), emergency operations (OR: 12.58; 95% CI: 2.91-54.30), and extending antibiotic prophylaxis duration (OR: 3.01; 95% CI: 1.28-7.10) were the independent risk factors for SSI (all p < 0.05).
Conclusions: This study highlights significant predictors of SSI, including illiteracy, smoking, diabetes, leukocytosis, hypoalbuminemia, contaminated and dirty wounds, longer operative time, emergency operations, and extending antibiotic prophylaxis duration. Identifying these risk factors can help surgeons adopt appropriate measures to reduce postoperative SSI and improve the quality of surgical care, especially in a resource-limited setting with no obvious and strict policy for reducing SSI.

Keywords

Surgical site infection, gastrointestinal surgery, predictors

Introduction

A surgical site infection (SSI) is a frequently encountered nosocomial infection that typically develops within 30 days of surgery. In cases where an implant is used, the timeframe for SSI occurrence can extend up to one year.1 The estimated incidence of SSI is 0.5% to 3% worldwide, with a higher incidence reported in low-income countries, where SSI is estimated to be the most common healthcare-associated infection.2,3 In addition to the socioeconomic status, surgeries that involve the gastrointestinal (GI) appear to have a higher SSI incidence, with reports indicating a 12%-30% incidence rate of such cases. The associated expenditure of increased hospitalization (7-11 folds), mortality, and morbidity (2-11 folds) force a higher emphasis on detecting such patients earlier in the course of their illness and identifying patients with a higher risk of developing SSI to improve the quality of care and minimize the cost.4,5

Various factors have been studied concerning SSI, which can extend from socioeconomic status to the preoperative settings and surgical approaches.6 Certain non-modifiable risk factors include age, gender, immunosuppression, diabetes mellitus, obesity, or active smoking. Additionally, the pre-operative preparation, operative time, and intra-operative techniques may impact the development of SSI, which is seen at a higher rate in emergent and septic surgeries.35 SSI can be attributed to microorganisms that are derived from the patient’s skin flora or from the surrounding environment.1 In either scenario, the adherence of microorganisms to the surgical instruments can contaminate the incision. Contaminated surgical procedures pose an increased risk, particularly when multidrug-resistant microorganisms are involved.6

Previous monocentric and retrospective studies in Yemen reported SSI rates of 2.2% and 31.7%.7,8 However, there is limited information available about the extent of SSI and its predictive factors in low-income countries, such as Yemen.7,8 This study aimed to investigate the SSI rate and its predictive factors among Yemeni patients who underwent GI surgeries in a resource-limited setting.

Methods

Study design

A retrospective cross-sectional study was conducted to investigate the SSI rate in patients who underwent gastrointestinal surgery at Al-Thora Hospital, Ibb University, IBB, Yemen, between June 2015 and October 2022. We included 525 patients, from whom written informed consent was obtained. The study was approved by the Ethics Research Committees of Ibb University [ID: IBBUNI.AC.YEM.2023.75, on 03/03/2023].

Inclusion criteria

Adult patients (≥18 years old), who had undergone either elective or emergency GI surgery at general surgery wards were included.

Exclusion criteria

Exclusion criteria were pregnancy, anticoagulation, incomplete or concealing data, non-bowel-related surgeries (e.g., hernia), postoperative complications within more than 30 days of surgery, or admission to another hospital.

Data collection

The study enrolled all eligible patients in consecutive order and utilized organized questionnaires to gather applicable information. This included demographics, including age, gender, educational level, body mass index (BMI), and place of residence, as well as health habits such as cigarette smoking and Khat chewing. In addition, comorbid conditions such as diabetes mellitus (DM), hypertension, chronic kidney, lung, and liver disease, history of malignancy, and preoperative blood transfusions were also documented. The American Society of Anesthesiologists (ASA) categorization system was used to measure preoperative physical state. Other information collected included the admission time, date, duration, wound nature, type, duration, anesthesia type, using the safety checklists, the urgency of surgery, readmission, reoperation, shaving time, and details of preoperative antimicrobial administration. Laboratory-collected data were white blood cell (WBC) counts, neutrophile percentage, and albumin levels.

The study documented surgery-related complications (e.g., SSI, fistula) in addition to non-surgical complications such as pneumonia, urinary tract infection (UTI), sepsis, and myocardial infarction (MI). Culture results and antibiotic sensitivities were also recorded, with wound swabs and pus specimens collected using standard microbiological techniques and transported to the laboratory for sensitivity analysis. Additionally, we collected the National Nosocomial Infections Surveillance (NNIS) index for each patient.

Definitions

Based on the depth of infection, these SSIs were subsequently categorized into superficial (affecting the skin and subcutaneous tissue), deep (involving muscle and fascia), and organ space infections.6 Wounds were classified into four categories depending on their level of contamination: clean, clean-contaminated, contaminated, or dirty-infected. The ASA score, which reflects the patient’s physical condition before the surgery, was determined through evaluation by the anesthesiologist using the ASA classification system.9 The NNIS index considers three risk variables, each of which is worth one point: contaminated or dirty-infected surgical wound, ASA scores greater than 2, and operation length greater than T (where T is defined as the 75th percentile of the normal time for a surgical procedure).9 The gastrointestinal cases were sorted into four categories (small bowel, large bowel, biliary, and pancreatic).10 Leukocytosis was defined as a WBC count greater than 100 × 109/L and hypoalbuminemia was defined as an albumin <3.5 g/dL.

Study outcomes

The prevalence of SSI was determined by assessing culture-positive results and/or physician diagnosis, according to the criteria set forth by the United States Center for Disease Control (CDC). This definition included infections affecting the superficial, deep, and organ space tissues of the surgical incision. The incidence of SSI was determined by evaluating and following up on all patients for 30 days following their surgery, starting from the date of the operation.9 It is important to note that medical complications such as pneumonia, MI, and UTI were separately documented and reported, and were not included in the definition of SSI or postoperative surgical complications.

Variables and measures

The outcome variable was SSI expressed as a binary variable: yes and no. Independent variables included Age (<60 years and ≥60 years), Sex (male and female), ASA score (Low [1 or 2] and High [3 or 4] NNIS index (No risk, Low risk, Moderate risk, High risk), Surgical sites (Small bowel and Other sites), Hospital stays (<5 days and ≥5 days), BMI (<30 kg/m2 and ≥30 kg/m2), Residency (Urban and Rural), Educational level (Educated and Illiterate), the Antibiotic time before surgery and shaving time (<1 h and ≥1 h), WBC (<10×109/L and ≥10×109/L), Albumin (≥3.5 mg/dL and <3.5 mg/dL), Operative type (Elective and Emergency), Blood loss (<200 mL and ≥200 mL), Anesthesia type (Spinal and General), Wound class (I and II and III and IV), Temperature (<38°C and ≥38°C), and Operative time (min). Additionally, Khat chewing, Smoking, History of hypertension, History of diabetes, History of chronic renal failure, History of chronic liver disease, History of lung disease, Perioperative blood transfusion, History of malignancy, Safety checklist used, and Drain insertion were presented as “yes” and “no”.

Statistical analysis

IBM SPSS version 22 software (IBM Corp., Armonk, New York) was used for statistical analyses. Quantitative variables were presented as means and standard deviations, while qualitative variables were reported as frequencies and percentages. The normality of the data was confirmed using the Kolmogorov-Smirnov test. Statistical tests were used to compare qualitative and quantitative variables, including the independent samples t-test or Mann-Whitney test for quantitative variables, and the Chi-square or Fisher’s exact test for qualitative variables.

Univariate analysis was conducted to identify the statistically significant variables associated with the development of SSIs and those variables with a p-value of less than 0.20 were subsequently fitted for binary logistic regression. The links between each risk factor and SSI are presented as an odds ratio (OR) and confidence interval (CI). A p-value of less than 0.05 was judged statistically significant. The ROC curve (receiver operating characteristic curve) was utilized to evaluate the risk adjustment prediction performance of the previous NNIS risk index and the Author’s model for post-gastrointestinal SSI, which contains the significant factors in multivariate analysis.9

Results

Characteristics and presentation of patients

This study included a total of 525 patients, comprising 295 (56%) male patients and 230 (44%) female patients, with a mean age of 52.9±16.9. Table 1 provides a summary of the patients’ characteristics and presentation. The postoperative 30-day SSI occurred in 86 (16.4%) patients. A total of 193 (36.8%) of patients had ASA Class One. The operative case distribution was 206 (39.2%) in the small bowel, 182 (34.7%) in the large bowel, 124 (23.6%) in the biliary system, and 13 (2.5%) in the pancreatic system. The mean operative time was 76.4±28.2 minutes. General complications were UTI and pneumonia in 5.5%, high-grade fever in 5.1%, and MI in 1% of patients. Laboratory and operative characteristics of patients are mentioned in Table 2.

Table 1. Patient characteristics of 525 patients who underwent gastrointestinal procedures.

VariablesN (%)
Age (year), Mean (SD)52.2 (15.7)
Sex
Male295 (56.2)
Female230 (43.8)
Education level
Illiterate200 (38.1)
Primary school203 (38.7)
High school122 (23.2)
Residency
Urban94 (17.9)
Rural431 (82.1)
Body mass index (kg/m2)
18.5-24.99178 (33.9)
25-29.99250 (47.6)
>3097 (18.5)
American society of anesthesiologists class
1193 (36.8)
2178 (33.9)
3123 (23.4)
431 (5.9)
Fever (Temperature ≥38°C)251 (47.8)
Current smoking status281 (53.5)
History of Hypertension158 (30.1)
History of Diabetes108 (20.6)
History of chronic renal disease76 (14.5)
History of chronic liver disease48 (9.1)
Shaving time ≥30 min of surgery306 (58.3)
History of lung disease26 (5.0)
History of malignancy39 (7.4)
History of Khat chewing425 (81.0)
Surgical status
Elective202 (38.5)
Emergency323 (61.5)
Time of prophylaxis antibiotic injection
During 1 house of operation346 (65.9)
More than one hour of operation179 (34.1)
Operative case
Small bowel206 (39.2)
Large bowel182 (34.7)
Biliary124 (23.6)
Pancreatic13 (2.5)

Table 2. laboratory and operative characteristics of 525 patients who underwent gastrointestinal procedures.

VariablesN (%)
Hypoalbuminemia (albumin <3.5)69 (13.1)
Leukocytosis, Mean (SD)24479 (48)
Neutrophil ≥85%283 (53.9)
Anesthesia type
Spinal131 (25.0)
General394 (75.0)
Safety checklists Used471 (89.7)
Wound calcification
Clean197 (37.5)
Clean-contaminated168 (32.0)
Contaminated123 (23.4)
Dirty37 (7.0)
Blood loss
≥200 ml102 (19.4)
<200 ml423 (80.6)
Drain insertion508 (96.8)
Operative time (min), Mean (SD)76.4 (28.2)
Hospital stays, (day), Mean (SD)5.4 (1.7)
30-day postoperative surgical site infection86(16.4)
General complication
Urinary tract infections29 (5.5)
Pneumonia29 (5.5)
High-grade fever27 (5.1)
Myocardial infarction5 (1.0)

Causative pathogens

Pathogens linked with SSI were identified from all SSI patient wounds. Escherichia coli (51.2%), Enterococcus spp. (17.4%), Bacteroides species (9.3%), and Clostridium perfringens (8.1%) were the most commonly isolated micro-organisms, with more than half of pathogenicity (63.8%) being multidrug-resistant organisms and the majority (70.1%) being extended-spectrum β-lactam producers (Table 3).

Table 3. Distribution of pathogens identified in surgical site infections.

Culture resultN (%)
Escherichia coli44 (51.2)
Enterococcus15 (17.4)
Bacteroides species8 (9.3)
Clostridium perfringens7 (8.1)
Pseudomonas aerugisa5 (5.8)
Klebsiella4 (4.7)
Anaerococcus prevotii3 (3.5)

The relationship between variables and SSI occurrences

The relationship between the independent factors and the dependent variable was explored using univariate and multivariate Cox regression analysis. On univariate analysis, Khat chowing, ASA class 4, smoking, hypertension, diabetes, hypoalbuminemia, illiterate, contaminated and dirty wounds, higher temperatures ≥38°C, leukocytosis, neutrophile ≥85%, longer operative time, blood loss more than 200 mL, biliary and pancreatic cases, longer hospital stay, shaving before one hour of operation, NNIS risk index, and emergency surgery were statistically significant associations with SSI occurrence (all p<0.05) (Table 4).

Table 4. Univariate analysis of risk factors associated with surgical site infection.

FactorsSubgroupNo SSI (n = 439)SSI (n = 86)OR (95%CI)P value
SexMale249 (84.4)46 (15.6)Reference group0.581
Female190 (82.6)40 (17.4)1.14 (0.71-1.81)
Age groups<60 years299 (84.5)55 (15.5)Reference group0.452
≥60 years140 (81.9)31 (18.1)1.20 (0.74-1.94)
BMI (kg/m2)<30359 (83.9)69 (16.1)Reference group0.736
≥3080 (82.5)17 (17.5)1.11 (0.60-1.94)
ResidencyUrban80 (85.1)14 (14.9)Reference group0.667
Rural359 (83.3)72 (16.7)1.15 (0.63-2.21)
Educational levelEducated296 (91.1)29 (8.9)Reference group<0.001
Illiterate143 (71.5)57 (28.5)4.07 (2.51-6.71)
Khat chewingNo94 (94.0)6 (6.0)Reference group0.003
Yes345 (81.2)80 (18.8)3.63 (1.66-9.57)
SmokingNo240 (98.4)4 (1.6)Reference group<0.001
Yes199 (70.8)82 (29.2)24.72 (10.08-82.01)
History of hypertensionNo286 (77.9)81 (22.1)Reference group<0.001
Yes153 (96.8)5 (3.2)0.12 (0.04-0.26)
History of diabetesNo373 (89.4)44 (10.6)Reference group<0.001
Yes66 (61.1)42 (38.9)5.39 (3.28-8.89)
History of chronic renal failureNo379 (84.4)70 (15.6)Reference group0.236
Yes60 (78.9)16 (21.1)1.44 (0.77-2.60)
History of chronic liver diseaseNo399 (83.6)78 (16.4)Reference group0.955
Yes40 (83.3)8 (16.7)1.02 (0.43-2.16)
History of lung diseaseNo417 (83.6)82 (16.4)Reference group0.888
Yes22 (84.6)4 (15.4)0.92 (0.27-2.49)
Antibiotic time before surgery<1 h292 (84.4)54 (15.6)Reference group0.506
≥1 h147 (82.1)32 (17.9)1.18 (0.72-1.89)
Perioperative blood transfusionNo408 (83.4)81 (16.6)Reference group0.676
Yes31 (86.1)5 (13.9)0.81 (0.27-1.98)
Shaving time before surgery<1 h199 (90.9)20 (9.1)Reference group<0.001
≥1 h240 (78.4)66 (21.6)2.74 (1.63-4.77)
History of malignancyNo405 (83.3)81 (16.7)Reference group0.534
Yes34 (87.2)5 (12.8)0.74 (0.25-1.78)
Temperature<38°C248 (90.5)26 (9.5)Reference group<0.001
≥38°C191 (76.1)60 (23.9)3.00 (1.84-5.00)
WBC (109/L)<10×103221 (90.6)23 (9.4)Reference group<0.001
≥10×103218 (77.6)63 (22.4)2.78 (1.69-4.72)
Albumin≥3.5mg/dL397 (87.1)59 (12.9)Reference group<0.001
<3.5mg/dL42 (60.9)27 (39.1)4.33 (2.47-7.52)
Operative typeElective172 (85.1)30 (14.9)Reference group0.454
Emergency267 (82.7)56 (17.3)1.20 (0.75-1.97)
Wound classI and II329 (90.1)36 (9.9)Reference group<0.001
III and IV110 (68.8)50 (31.2)4.15 (2.58-6.75)
Anesthesia typeSpinal110 (84.0)21 (16.0)Reference group0.900
General329 (83.5)65 (16.5)1.03 (0.61-1.81)
Safety checklist usedYes395 (83.9)76 (16.1)Reference group0.654
No44 (81.5)10 (18.5)1.18 (0.54-2.36)
Blood loss<200 ml96 (94.1)6 (5.9)Reference group0.003
≥200 ml343 (81.1)80 (18.9)3.73 (1.71-9.83)
Operative time (min)Mean (SD)72.5 (25.9)96.5 (30.7)1.03 (1.02-1.04)<0.001
Drain insertionNo15 (88.2)2 (11.8)Reference group0.603
Yes424 (83.5)84 (16.5)1.49 (0.41-9.54)
Hospital stays<5 days177 (92.2)15 (7.8)Reference group<0.001
≥5 days262 (78.7)71 (21.3)3.20 (1.82-5.96)
Surgical siteOther sites263 (82.4)56 (17.6)Reference group0.366
Small bowel176 (85.4)30 (14.6)0.80 (0.49-1.29)
NNIS indexNo risk240 (96.0)10 (4.0)Reference group
Low risk86 (76.8)26 (23.2)7.26 (3.46-16.37)<0.001
Moderate risk87 (68.0)41 (32.0)11.31 (5.64-24.79)<0.001
High risk26 (74.3)9 (25.7)8.31 (3.05-22.51)<0.001
ASA scoreLow (1 or 2)322 (86.8)49 (13.2)Reference group0.003
High (3 or 4)117 (76.0)37 (24.0)2.08 (1.29-3.34)

Multivariate logistic regression revealed the following independent risk factors

Illiteracy (OR:40.31; 95% CI: 9.54-170.26), current smoking (OR: 21.15; 95% CI: 4.63-96.67), diabetes (OR: 5.07; 95% CI: 2.27-11.35), leukocytosis (OR: 2.62; 95% CI: 1.24-5.53), hypoalbuminemia (OR: 3.70; 95% CI: 1.35-10.16), contaminated and dirty wounds (OR: 6.51; 95% CI: 1.62-26.09), longer operative duration (OR: 1.02; 95% CI: 1.01-1.03), emergency operations (OR: 12.58; 95% CI: 2.91-54.30), and administering antibiotics before 1 h of operation (OR: 3.01; 95% CI: 1.28-7.10) were independent factors for SSI (all p-value<0.05, Table 5). The prediction model’s total ROC curve was 0.946, which was much higher than the NNIS score (0.660) (Figure 1).

Table 5. Multivariate analysis of risk factors associated with surgical site infection.

PredictorEstimateSEZP valueOR95%CI
LowerUpper
Education level3.69660.735085.0288<0.00140.319.54351170.26
Khat chowing0.68762.976570.23100.8171.990.00582679.66
Smoking3.05180.775273.9365<0.00121.154.6290396.67
Hypertension-0.80140.84596-0.94730.3430.450.085482.36
Diabetes1.62400.410733.9539<0.0015.072.2681611.35
Shaving time0.53500.417891.28020.2001.700.752723.87
Temperature0.25830.393580.65630.5121.290.598642.80
WBC (109/L)0.96430.380892.53160.0112.621.243275.53
Hospital stays0.29630.473400.62600.5311.340.531803.40
Albumin1.30940.514942.54290.0113.701.3500710.16
Wound class1.87350.708272.64510.0086.511.6246126.09
Blood loss0.65882.991940.22020.8261.930.00549680.54
Operative time0.02140.006443.3313<0.0011.021.008861.03
ASA-0.22910.58612-0.39090.6960.790.252122.51
NNIS score-0.07050.85520-0.08250.9340.930.174354.98
Operative type2.53230.746013.3944<0.00112.582.9157554.30
Antibiotic time1.10320.436872.52530.0123.011.280137.10
Accuracy: 0.905; Specificity: 0.966; Sensitivity: 0.593; AUC: 0.946.
Nagelkerke R square: 0.648
Significance of the model <0.001
77c944b8-3957-4e3e-bb23-9a2670cd1669_figure1.gif

Figure 1. The receiver operating characteristic curve of the prediction model compared with the National Nosocomial Infections Surveillance risk index in the validation cohort.

Abbreviations: AUROC: Area under the receiver operating characteristic curve; NNIS: National Nosocomial Infections Surveillance.

Discussion

The improved access to healthcare, increased population age, and increased complexity of surgical interventions and patients’ conditions shed light on the importance of managing post-operative complications. Despite the precautions and the hygienic approach implemented to limit the incidence of SSI, it still represents one of the most common post-operative complications. Such infections result in an increased healthcare expenditure, and worsened mortality and morbidity.10 This predicament can be especially disadvantageous for low-income nations, where providing healthcare is already a daunting task due to constrained resources, indigent communities, and elevated levels of antimicrobial resistance.11

Among the 525 enrolled patients, the incidence of SSI within 30 days after surgery was 16.4%, which is in line with previous reports from developing countries, such as Saudi Arabia, with a rate of 16.3%.14 However, earlier studies showed much higher rates of SSI affecting up to one-third of the patients in Yemen.8 In contrast, more recent reports from Yemen have demonstrated a lower incidence of SSI, with a rate of 12.7% among patients who underwent gastrointestinal procedures.8 Our findings, which showed a slightly higher rate of SSI, could be partially attributed to the larger number of complicated cases or complex oncological procedures performed at our tertiary teaching hospital.

Several studies have been conducted to evaluate the link between putative risk variables and SSI in GI surgical operations. However, there is a large range of variation in the variables analyzed and the proportional effect of these factors on individual outcomes. To address this issue, we comprehensively studied the preoperative and operational risk variables in GI operations associated with the development of postoperative SSI. Hamza et al. and Lakoh et al. carried out similar investigations.6,12 This study found that illiteracy, current smoking status, DM, leukocytosis, hypoalbuminemia, contaminated and dirty wounds, longer operative time, emergency operations, and longer time between administering antibiotics and operation were predictors for the development of SSI. Most of the potential predictive factors included have been previously reported as risk factors in other studies with a variety of reports and different levels.6,12

The relationship between age and SSI risk is complex and not well understood. While some studies have reported an increased rate of infection in older patients, others have observed a favorable trend with increasing age. For instance, Kaye et al. demonstrated a 1.2% decrease in SSI risk for each additional year after 65 years of age.13 Nevertheless, these findings were demonstrated consistently, as a higher rate of SSI was observed in the older population.14,15 Typically, with increasing age, there is an accumulated risk of developing comorbidities and immune dysfunction, which may lead to an increased likelihood of SSI. However, our study’s findings revealed no association between age and the development of SSI. This divergence may be attributed to variations in age categorization, as the majority of patients (67%) in this study were younger than 65 years.

The present study reveals a significant association between the level of literacy and the incidence of SSI. Specifically, illiterate patients were 40 times more susceptible to SSIs than educated patients. These results are in accordance with previous research conducted by Mezemir et al. and Baker et al.16,17 Notably, a high prevalence of limited health literacy among adults in our country may adversely impact health outcomes. For example, patients with limited health literacy may experience difficulty in comprehending complex health information, may exhibit non-compliance with postoperative instructions, and may not adequately prepare for surgery. These factors may increase the risk of SSIs and other adverse outcomes, highlighting the potential health inequality in providing care and education for illiterate patients. Therefore, it is critical to improve health literacy among patients, particularly those with limited education, to potentially reduce the incidence of SSIs and enhance surgical outcomes.

This study did not find a significant association between unmodifiable risk factors, such as gender, BMI, residency, number of comorbidities (hypertension, history of malignancy, CRF, liver and lung diseases), perioperative blood transfusion, and SSIs in multivariate analysis. Although these social determinants are important factors that may contribute to patient outcomes, there is a lack of consensus on their association with SSI occurrence in the literature. For example, Deng et al. found that male sex and a greater number of comorbidities were associated with SSI occurrence.18 Additionally, Li et al. reported that ascites, bleeding diathesis, history of lung disease, radiotherapy, chemotherapy, chronic steroid use, and weight loss were associated with SSI occurrence.19 In contrast, Mezemir et al. did not find an association between gender, BMI, and SSI occurrence, which was similar to our study.16 These discrepancies may be attributed to sample size and demographics variation across studies, as well as variations in the documentation and management of patient comorbidities. The use of more objective measures, such as preoperative laboratory and radiologic values, may provide a better understanding of the association between comorbidities and SSI occurrence. Distinctly, in this study, DM and hypoalbuminemia had 5- and 3.7 times higher chances of developing SSIs, respectively. This association was observed in prior studies,11,20 as hyperglycemia has been shown to impair WBC functions, leading to decreased immunity.21 On the other hand, reduced serum albumin levels are often associated with malnutrition or chronic wasting diseases.11

Our study revealed that smoking was strongly associated with a 21-fold increased risk of developing SSIs compared to non-smokers. The vasoconstrictive and toxic effects of smoking are known to impede tissue oxygen delivery and hinder the healing process, thus contributing to the development of SSIs. These findings align with previous reports by Mawalla et al. and Billoro et al.22,23

Regarding Khat (Catha edulis) chewing, its role in SSI occurrence remains uncertain. Our study observed a 1.99-fold increase in SSI occurrence among Khat chewers, although this association was not statistically significant. Currently, there is a lack of published studies specifically investigating the relationship between SSI and Khat chewing. However, Misha et al. found no association between Khat chewing and SSI occurrence in their regression analysis.3 Nevertheless, Khat chewing has been linked to various gastric issues (e.g., intestinal obstruction, and gastritis).24 Furthermore, long-term Khat consumption poses a risk of developing severe complications including hepatitis, hepatic fibrosis, and cirrhosis in advanced stages.25 Future prospective and more inclusive studies are recommended to investigate this issue, particularly in our country where the traditional use of these plants is widespread.

The settings of operation can significantly impact the development of SSI. Prior research has suggested that the degree of intraoperative wound contamination is indicative of SSI occurrence.26,27 We found that contaminated and dirty wounds were 6.51 times more likely to develop SSI, which is consistent with other studies.2628 Furthermore, our study revealed that the prevalence of SSI in large, pancreatic, and biliary surgeries was lower than in intestinal procedures; although this association was not statistically significant. Similarly, other studies have also reported a higher incidence of SSI in the intestinal tract.11,29 However, our findings were inconsistent with the literature documenting pancreatic and biliary leaks as independent risk factors for SSI occurrence.27 This discrepancy could be attributed to the low number of cases involving biliary and pancreatic procedures, with most of them undergoing simple operations. Therefore, further prospective studies with a larger number of cases are necessary to clarify this issue.

Our study also found that emergency operations were 12.58 times more likely to result in SSI, consistent with other studies.6,11 In addition, leukocytosis was found to be a predictor for the development of SSI, which aligns with previous research.30 Additionally, prolonged operative time was recognized as an independent factor for SSI development in other studies, as it increases the risk of infection due to extensive surgical procedures and incisions, prolonged anesthesia, blood loss, and weaning antimicrobial prophylaxis concentration.6,31 Furthermore, administering antibiotics one hour before operation has been reported as a predictor for SSI in previous studies.23,31 In this study, it was observed that longer operation durations and administration of antibiotics more than one hour before the operation increased the likelihood of SSI by 1.02 times and 3.01 times, respectively. These findings are consistent with previous studies.23,31

In this study, we investigated the microorganisms responsible for SSIs and their susceptibility to commonly prescribed prophylactic antibiotics. We found that the most common organisms isolated from infected wounds were Gram-negative bacteria, with extended-spectrum β-lactamase-producing E. coli being the most prevalent. Mawalla et al. reported a different outcome compared to this finding, as their studies indicated a higher presence of Gram-positive bacteria, including Staphylococcus aureus.22 In contrast, studies have reported similar findings to ours, demonstrating a higher occurrence of Gram-negative bacteria in infected abdominal wounds.26,32 Furthermore, our findings revealed a high prevalence of multi-resistant pathogens in relation to commonly prescribed prophylactic antibiotics, which may serve as an explanation for the elevated rate of deep SSI observed in our study. Hence, there is a need to consider appropriate prophylactic antibiotics, especially for high-risk patients.

The NNIS risk index is a widely recognized framework for assessing and predicting the likelihood of SSI.9 Within our study, two elements of the NNIS exhibited statistical significance (operative time and wound class). However, upon conducting multivariate analysis, the overall NNIS model did not yield statistical significance. Moreover, when comparing the predictive accuracy, our developed model outperformed the NNIS model. Acutely, the performance of the NNIS model in this study showed poor predictive performance for the SSI occurrence as determined by the ROC curve. These results align with previous findings reported by Zhang et al.11

Study limitations

There are several limitations to consider in this study. First, the retrospective nature of the study may introduce an unintended bias to the study. In addition, it was conducted at a single tertiary teaching hospital, which may limit the generalizability of the findings to other healthcare settings. Furthermore, the study relied on clinical documentation to identify SSI, which could lead to underreporting or misclassification of cases. Moreover, the study focused on a specific geographic region, and the findings may not apply to other populations with different demographics or healthcare systems. Although the study took into account certain potential confounding variables (e.g., the use of prophylactic antibiotics), other potential confounding variables are difficult to assess with the retrospective nature of the study (e.g., surgical techniques and intra-operative maintenance of sterile technique, among others). Finally, the study did not explore long-term outcomes or evaluate the impact of interventions aimed at reducing surgical site infections.

Conclusions

This study highlights significant predictors of SSI, including illiteracy, active smoking, DM, leukocytosis, hypoalbuminemia, contaminated and dirty wounds, longer operative time, emergency operations, and extending antibiotic prophylaxis duration. Escherichia coli was the most common pathogen and had a high rate of multidrug-resistant strains. Identifying these risk factors can help surgeons adopt appropriate measures to reduce SSI and improve the quality of surgical care, especially in a resource-limited setting with no obvious and strict policy for reducing SSI.

Ethical considerations

Ethical approval was granted by the Ethics Research Committees of Ibb University [ID: IBBUNI.AC.YEM.2023.75, on 03/03/2023].

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Al-hajri A, Ghabisha S, Ahmed F et al. Identification of predictive factors for surgical site infections in gastrointestinal surgeries: A retrospective cross-sectional study in a resource-limited setting [version 1; peer review: 1 approved with reservations]. F1000Research 2023, 12:733 (https://doi.org/10.12688/f1000research.135681.1)
NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article.
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ApprovedThe paper is scientifically sound in its current form and only minor, if any, improvements are suggested
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Reviewer Report 25 Aug 2023
Nicolas Troillet, Department for Infectious Diseases, Central Institution, Valais Hospital, Sion, Switzerland 
Approved with Reservations
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This is an interesting and well written study aiming at determining a prediction rule for surgical site infection after digestive surgery in a developing country. It gathered a substantial number of parameters for univariate and multivariable analysis in order to ... Continue reading
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Troillet N. Reviewer Report For: Identification of predictive factors for surgical site infections in gastrointestinal surgeries: A retrospective cross-sectional study in a resource-limited setting [version 1; peer review: 1 approved with reservations]. F1000Research 2023, 12:733 (https://doi.org/10.5256/f1000research.148812.r192612)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
  • Author Response 23 May 2024
    Faisal Ahmed, Urology Research Center, Al-Thora General Hospital, Department of Urology, School of Medicine, Ibb University of Medical Sciences, Ibb, Yemen
    23 May 2024
    Author Response
    Dear reviewer
    Thank you very much for reading and reviewing my manuscript.
    This is an interesting and well-written study aiming at determining a prediction rule for surgical site infection after ... Continue reading
COMMENTS ON THIS REPORT
  • Author Response 23 May 2024
    Faisal Ahmed, Urology Research Center, Al-Thora General Hospital, Department of Urology, School of Medicine, Ibb University of Medical Sciences, Ibb, Yemen
    23 May 2024
    Author Response
    Dear reviewer
    Thank you very much for reading and reviewing my manuscript.
    This is an interesting and well-written study aiming at determining a prediction rule for surgical site infection after ... Continue reading

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Alongside their report, reviewers assign a status to the article:
Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions
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