Humans are often affected by Mycobacterium infections. In developing countries, non-tuberculous mycobacterial (NTM) infections have been overshadowed by high incidences of tuberculosis. This trend is, however, fast-changing. The number of new infections is increasing due to the growing number of immune-deficient patients ( Ferreira et al., 2002) and nonsterile endoscopic medical devices ( Duarte et al., 2009). Pulmonary diseases caused by NTM have been on the increase worldwide ( Hoefsloot et al., 2013). In 2014 estimated prevalence of pulmonary tuberculosis caused by NTM was estimated to be 33–65 per 100,000 persons ( Morimoto et al., 2014).

Globally, positive acid-fast bacilli (AFB) specimens are assumed to develop Mycobacterium tuberculosis (MTBC) and are therefore managed by anti-tuberculosis agents whereas some are put under speculated areas ( Mertaniasih et al., 2017). The high prevalence of AFB leads to isolation of mycobacterial illness, meaning that more patients with AFB-positive samples have been administered unsuitable and, more so, unnecessary empirical anti-tuberculosis treatment ( Ngayo et al., 2015). As a result of this incorrect treatment and high treatment letdown, the mortality of patients with lung infections is increasing. Therefore, appropriate diagnosis and regular monitoring are crucial in monitoring and treating patients ( Aksamit et al., 2014).

In Kenya, data regarding the burden of pulmonary illness is scanty, partly due to constraints in surveillance and diagnosis of mycobacterial species. Distribution of these species (NTM) contributes to the difficulties in interpreting positive culture results. Furthermore, it is not mandatory to report cases of disease to the database at the Ministry of Health; thus, data regarding the epidemiology and distribution of pulmonary disease’s causation is inadequate in Kenya ( Jacqueline et al., 2015). The decision to initiate treatment should be influenced by the severity of disease, the risk of progressive NTM-pulmonary disease, the presence of comorbidity and the goals of treatment. Decision to treat remains individualized with consultations and individuals may require a period of longitudinal assessment (symptoms, radiological change and mycobacterial culture results) to inform NTM treatment decisions. To determine the clinical relevance of NTM positive cultures, it is essential to distinguish transient or persistent colonization (which is usually not treated) from true infection ( Daley et al., 2020). It’s against this that the current study was undertaken to characterize the NTM

A total 24,549 records were reviewed. Of these, 167 (0.7%) NTMs were isolated ( Kamau, 2023). The highest isolation was among individual aged 35-44 years, (46/167, 27.5%). Males comprised 74.2% (124). The mean age (SD) was 42(16) years. The NTM were isolated in 65% (31/47) of the counties; Most samples came from Nairobi County at 12.6% (21/167), then Mombasa 10.8% (18/167), and Kilifi and Meru counties at 7.8% (13/167). HIV positivity rate of 27.5%(46/167). Most NTM were isolated from previously treated patients 63.5%(106/167), drug-resistant follow-up patients 26.9% (45/167) and New patients 9.6%(16/167) [ Table 1]. Coinfection with NTM and HIV was at 27.5% (46/167).

A total of eleven NTM species were identified, with frequent ones being Mycobacterium intracellulare at 35.3% (59/167), M. fortuitum at 26.3% (44/167), and M. scrofulaceum at 10.2% (17/167). Majority of NTM had a Smear outcome of No AFB seen [59.3%(99)], Smear 1+ [11.4%(19)], and smear 2+ [10.2%(17)] [ Table 2].

Our study found that the prevalence of NTM was low AT [0.7%(167/24,549)] and most of the cases were males which was similar to study done by ( Fatima & Nm, 2019) on prevalence of Nontuberculous Mycobacterial infection in Non-HIV subjects. The MAC complex is considered to be the most prevalent globally accounting for 86% ( Nishiuchi et al., 2017). These findings are consistent with our study that isolated MAC species M.intracellulare [35.3 % (59/167), M.fortuitum 26.3% (44/167) M. scrofulaceum 10.2% (17/167), M.kansasii 9.6% (16/167)] [ Table 2]. MAC species are frequently isolated in different environmental sources like water and soil and there is frequent contact with this sources thus increasing its infection to human ( van Ingen et al., 2009). Similar findings from other countries have described isolation of MAC species ( Namkoong et al., 2016; Nishiuchi et al., 2017). Similar finding found out that M. intracellulare was most prevalent ( Epola Dibamba Ndanga et al., 2022). However, MAC was not reported as predominant in other settings i.e. South Pacifica where M.fortuitum complex fewer cases were isolated; in India M.fortuitum was predominant and MAC was not detected. The high infectivity rate of MAC species may be linked to their apparent abundance and distribution in many environmental sources such as water and soil, which increases the ease of dissemination and infection to people. MAC has been strongly linked to NTM Pulmonary Disease (NTMPD); nevertheless, it is unknown how its infectivity connects to NTMPD ( Mwangi et al., 2021, 2022).

In our findings persons within the age group (35-44 years) were most affected. More males were affected suggesting that women could be having a protective effect due to the hormonal variation which triggers a response and clears the bacterial infection ( Namkoong et al., 2016; Ji et al., 2020).

Pulmonary NTM were mostly found in patients who were previously treated for TB Most of the cases were HIV negative which was inconsistent with what has been reported previously ( Stepanyan et al., 2019). In people with HIV/AIDS, NTM infections can occur in various parts of the body, including the lungs, lymph nodes, and skin. These infections can be severe and difficult to treat, especially if the immune system is severely compromised.

Most NTM were isolated from of counties, leading county being Nairobi County with [12.6 %(21/167)], followed by Mombasa County and Kilifi and Meru County. These findings may be inconclusive on factors influencing the geographical distribution of NTM in the different geographical landscapes in Kenya, a more comprehensive study capturing both human and environmental particulars is required for a better understanding of environmental NTM species distribution. Differences in specific NTM species predominance in various environments may in part influence the frequency of pulmonary NTM disease in each geographical location.

The presence of NTM among the presumptive cases poses a public health challenge and which potentially complicates TB diagnosis and management. The Division of National TB, Leprosy and Lung Diseases Program (DNTLD-P) should put NTM in planning the prevention and management of tuberculosis control, these findings are similar to a study done in Gabon ( Epola Dibamba Ndanga et al., 2022).

MAC was the most prevalent followed by M.fortuitum and M.scrofulaceum. Previously treated patients should have an additional screening of NTMS, and drug susceptibility testing should be done before initiation of treatment, additional screening of NTM’s in should be done in males especially withiinthe age group of (35-44) years.