Environmental Non-tuberculous Mycobacteria (NTMs)

The ubiquitous and opportunistic nature of some mycobacterial species in the Ugandan environment has further complicated the diagnostic and therapeutic picture of Mycobacterium as a genus.

The common assumption in Uganda is that most individuals presenting with pulmonary symptoms are infected with M. tuberculosis. Therefore, NTMs are not identified during routine TB diagnosis. This is mainly attributed to the limited diagnostic capacities of rural health centers and the lack of awareness along the diagnostic pipeline (Muwonge et al. 2012a, b). In the presence of HIV infections, zoonotic and infections with NTMs continue to present challenges to case manage­ment of immune-compromised individuals. This is specifically so because of the following reasons:

• A positive smear result for NTM can easily be mistaken for TB infection.

• The majority of NTMs are naturally resistant to most anti-mycobacterial drugs.

• The extrapulmonary nature of M. bovis infection further undermines the diagnos­tic value of sputum specimens.

• Differentiating a true NTM lung infection from contamination and/or coloniza­tion is difficult.

All these attributes make the treatment of TB cases increasingly challenging in Uganda, especially in rural settings.

Recent studies in Uganda have identified the M. avium complex (29.0%; n = 48), M. intracellulare (18.8%; n = 48), the M. fortuitum peregrinum complex (25.0%; n = 48), M. gordonae (10.4%; n = 48), M. nonchromogenicum (10.4%; n = 48), M. engbaekii (4.2%; n = 48), and M. kubicae (4.2%; n = 48) as the most commonly isolated mycobacterial species in human-animal ecosys­tems. The isolation of NTMs in the cattle corridor ecosystem of the Mubende and Nakasongola areas showed seasonal variations, with the highest number of isolates originating from the water sources in November and December (Kankya et al. 2011). The isolation of NTMs in the ecosystem was also directly linked to cattle-keeping activities, open or natural water sources such as valley dams, and the presence of wildlife, especially antelopes. Studies further confirmed that these organisms were not only found in the environment but were also infecting communities and their cattle (Table 22.2) (Oloya et al. 2006, 2008). In the Karamoja District, the NTMs recovered from human and cattle shared identical profiles; i.e., M. avium complex (41.7%), M. bovis (12.5%), M. intracellulare (8.3%), and unidentified species of mycobacteria (4.7%) were isolated from humans, whereas M. avium sub. sp. hominissuis (8.1%; n = 37), M. intracellulare (2.7%; n = 37), and M. avium (2.7%; n = 37) were isolated from slaughtered cattle. Incidentally, multi-species infections (5.4%; n = 37) were also observed in the region. This means that both tuberculous and non-tuberculous mycobacterial species were recovered from the same tuberculous lesion (Oloya et al. 2007a).

Table 22.2 Non-tuberculous mycobacterial species commonly isolated in Uganda

Insufficient surveillance data of zoonotic TB in Uganda are attributed mainly to inadequate resource allocation and the minor attempts to identify such patients. To patch these holes, there is a need to review the current protocol of sputum smear mycobacteriology and chest x-ray as diagnostic criteria for TB in rural communities that keep livestock and use open water sources. There is a further need for additional diagnostic protocols for pulmonary NTM and BTB and increasing the awareness of the health workers about the appropriate diagnostic tools and managing NTM and M. bovis infections in rural health centers.

22.2