Isolation, identification and associated risk factors of non-tuberculous mycobacteria infection in humans and dromedary camels in Samburu County, Kenya.

Non-tuberculous mycobacteria are of public health significance, and zoonotic infection is attributed to the sociocultural practice of consumption of raw milk and the close human-livestock contact in pastoral communities. This study aimed at isolation, identification of mycobacteria from human sputum and camel milk and risk factors assessment in Samburu East, Kenya. Six hundred and twelve camels and 48 people presumed to have tuberculosis (TB) from 86 households in Wamba and Waso regions were screened. Camels were categorized into Somali, Turkana and Rendile breeds. Single intradermal comparative tuberculin test (SICTT) was used as a herd-screening test on lactating camels and a milk sample collected from reactive camels. Sputum samples were collected from eligible members of participating households. A standard questionnaire on possible risk factors for both humans and camels was administered to respective household heads or their representatives. Total camel skin test reactors were 238/612 (38.9%). Milk and sputum samples were analysed at KEMRI/TB research laboratory for microscopy, GeneXpert® , culture and identification. Isolates were identified using 16S rRNA gene sequencing at Inqaba biotec in South Africa. Sixty-four isolates were acid-fast bacilli (AFB) positive of which M. fortuitum (3), M. szulgai (20), M. monacense (5), M. lehmanni (4), M. litorale (4), M. elephantis (3), M. duvalii (3), M. brasiliensis (1), M. arcueilense (1) and M. lentiflavum (1) were from milk; M. fortuitum (1), M. szulgai (2) and M. litorale (1) were from humans. Risk factors included the following: Turkana breed (OR = 3.4; 95% CI: 1.2-9.3), replacements from outside the County (OR = 2.1; 95% CI: 0.3-12.3), presence of other domestic species (small stock; OR = 4.6) and replacement from within the herd (OR = 3.2; 95% CI: 0.7-14.7). Zoonotic risk practices included raw milk consumption, shared housing and handling camels. Monitoring of zoonotic NTM through surveillance and notification systems is required.

A cross-sectional epidemiological investigation of nontuberculous mycobacteria of public health importance in slaughter camels in Samburu County, Kenya.

The diagnosis of tuberculosis (TB) in camels at slaughter houses heavily relies on post mortem (PM) meat inspection to detect granulomatous lesions; however, the sensitivity of this technique is not perfect. The objective of this study was to isolate and characterize mycobacteria associated with suspect TB pathological lesions at PM. At PM, 1600 camels were examined in two county slaughterhouses. One hundred and thirty two, 8.25% (132/1600) (Binomial CI 95% 6.95-9.71%), suspect granulomatous lesions were found. Twenty seven, 1.69% (27/1600) (Binomial CI 95% 1.11-2.45%), were confirmed as acid-fast bacilli (AFB) using Ziehl-Neelsen (ZN) staining after culture. Speciation using the GenoType® Mycobacterium assay (Hain Lifesciences, Nehren, Germany) found a majority isolates to be Mycobacterium fortuitum (17), the other species identified included M. szulgai (2), M. scrofulaceum (3), M. marinum (1), M. intracellulare (1), M. gordonae (1), and 2 unidentified mycobacteria species. The types of lesions observed were nodular, caseous masses involving whole organs or cavities, and purulent masses. The highest proportion of suspect lesions were observed in the right, left bronchial lymph nodes, and the mediastinal lymph nodes (59.54%), followed by the retropharyngeal lymph nodes (12.21%), the medial lobe (10.67%), and the left lateral and quadrate lobes of the lungs (17.58%). The 6-7 age category had higher odds (OR = 2.5) of culture positivity. It was concluded that a variety of NTM species of medical importance were associated with TB lesions in the thoracic lymph nodes and lungs. There is need to unravel the public health significance of these mycobacteria.