Genetic diversity of nontuberculous mycobacteria among symptomatic tuberculosis negative patients in Kenya

Non-Tuberculous Mycobacteria (NTM) transmission to humans occurs through inhalation of dust particles or vaporized water containing NTM leading to pulmonary manifestations. NTM infections are often misdiagnosed for tuberculosis (TB) due to their similar clinical and radiological manifestations.

We, therefore, performed a species-level identification of NTM in symptomatic TB negative patients through sequencing of the hsp65 gene.

We conducted a cross-sectional study at the National Tuberculosis Reference Laboratory in the period between January to November 2020. One hundred and sixty-six mycobacterial culture-positive samples that tested negative for TB using capilia underwent Polymerase Chain Reaction targeting the hsp65 gene. Isolates showing a band with gel electrophoresis at 441 bp position were sequenced using Sanger technology. Geneious software was used to analyze the obtained sequences, and the National Center for Biotechnology Information gene database identified NTM species for each isolate. A phylogenetic tree was constructed from the DNA sequences and evolutionary distances computed using the general time-reversible method. Pearson chi-square was used to determine the association between NTM infection and participants' characteristics.

Our study identified 43 different NTM species. The dominant NTM belonged to Mycobacterium avium complex 37 (31%). Slow-growing NTM were the majority at 86 (71%) while rapid-growing NTM were 36 (29%). A significant association (P<0.05) was observed for regions and age, while patient type had a weak likelihood of NTM infection.

Our study characterized the diversity of NTM in Kenya for the first time and showed that species belonging to M. Avium Complex are the most prevalent in the country.