Objective: Characterising clinical Mycobacterium tuberculosis isolates obtained from 1995 to 2006 in Bogotá , Colombia , using standardised IS6110-based RFLP typing for determining phylogenetic relationships. Calculating cases due to recent infection (grouped cases) cf endogenous reactivation (single patterns).
Methods: This retrospective study characterised 137 clinical Mycobacterium tuberculosis isolates obtained in Bogotá from 1995 to 2006. Study variables consisted of gender, age, HIV status, homelessness, Ziehl Neelsen smear result and date of culture. All isolates were freshly identified by phenotypic methods, confirmed by PRA and evaluated for susceptibility to antimicrobial agents according to the proportional method. Mycobacterium tuberculosis cultures were typed by standardised IS6110-based RFLP.
Results: All isolates were confirmed as being M. tuberculosis by phenotypic and genotypic methods. 9,4 % monoresistance and 2,9 % MDR (rifampicin- and isoniazid-resistant) were found. 129 M . tuberculosis isolates were genotyped; 96 (74 %) of them presented unique DNA fingerprints, whilst 35 (26 %) were grouped into 17 clusters consisting of two to four isolates. Direct epidemiological links between patients could not be established in most cases. Only HIV status was a significant predictor of clustering amongst the variables being studied (p<0.05).
Conclusion: The results of our study revealed a high proportion of unique DNA fingerprints, suggesting high genetic variability between M. tuberculosis strains in Bogotá , Colombia , meaning that most cases of TB in this study were attributed to endogenous reactivation.