The distribution of mycobacterium tuberclosis complex species among PTB patients presenting at the National TB Treatment Center at Mulago Hospital, Kampala Uganda

Abstract

Tuberculosis (TB), caused by the bacterium Mycobacterium tuberculosis complex (MtbC) is one of the deadliest pathogens in human history. Tuberculosis control today relies on case identification, treatment (case holding) until cure and in certain instances prophylaxis with drugs such as in case of recent infection without clinical or radiological manifestation in non-BCG vaccinated children less than 5 years of age, living in close contact with patients and presenting with a strong positive reaction to tuberculin. The gold standard of TB diagnosis and speciation is based on the demonstration of AAF bacilli in clinical specimens, culture and setting biochemical tests. However classification based on physical and biochemical properties are tedious, interpretation subjective and therefore can give ambiguous results. Molecular typing techniques particularly based on amplification or lack of specific DNA sequences has been found to give superior results. Despite high prevalence of TB in Uganda species identification of MtbC is still a remote practice, particularly speciation based on molecular techniques, although there have been attempts to classify these organisms mainly on basis of biochemical tests. Strain typing allows the tracing of epidemiologically related cases including virulent or MDR strains, identification of nosocominal infections, differentiation of new cases from relapses and identification of laboratory contaminants. This study describes molecular typing of 300 M. tuberculosis complex isolates cultured from sputum of patients described in the literature based on genomic deletion sequences namely; RD9, TbD1, RD4, RD1, RD12. The distribution of the molecular type pattern suggests that the population of M .tuberculosis complex strains isolated from PTB patients attending National TB treatment centre at Mulago was predominantly M. tuberculosis constituting 89.3 % contrary to the previous study a decade ago which showed that M. africanum was the predominant species in Kampala constituting 67 %. This time M. africanum constituted only 2.7 % of the isolates, 22 (7.3 %) were identified as M. tuberculosis ancient strain, and 2 (0.7 %) were identified as M. canettii. The study concludes that M. tuberculosis is the predominant MtbC species causing TB among patients aged twelve years and above presenting at the National TB treatment center at Mulago hospital, Kampala, Uganda. M. africanum constitutes a small percentage of only 2.7 %, and M. canettii 0.7 %. From the above findings, the study safely recommends that there is urgent need to carry out similar speciation studies up-country. Such studies should in addition search for possible accentuating factors for TB infection such as HIV. The study further recommends that molecular methods of diagnosis and speciation be imported for routine use in all microbiology laboratories in this country, as this would promote good TB management and control.