Prevalence of Extensively Drug Resistant Tuberculosis among Archived Multidrug Resistant Tuberculosis Isolates in Zimbabwe

Abstract EN

We conducted a cross-sectional study of second line drug resistance patterns and genetic diversity of MDR-TB isolates archived at the BRTI-TB Laboratory, Harare, between January 2007 and December 2011.

DSTs were performed for second line antituberculosis drugs.

XDR-TB strains were defined as MDR-TB strains with resistance to either kanamycin and ofloxacin or capreomycin and ofloxacin.

Strain types were identified by spoligotyping.

No resistance to any second line drugs was shown in 73% of the isolates, with 23% resistant to one or two drugs but not meeting the definition of XDR-TB.

A total of 26 shared types were identified, and 18 (69%) matched preexisting shared types in the current published spoligotype databases.

Of the 11 out of 18 clustered SITs, 4 predominant (>6 isolates per shared type) were identified.

The most and least abundant types were SIT 1468 (LAM 11-ZWE) with 12 (18%) isolates and SIT 53 (T1) with 6 (9%) isolates, respectively.

XDR-TB strains are rare in Zimbabwe, but the high proportion of “pre-XDR-TB” strains and treatment failure cases is of concern.

The genetic diversity of the MDR-TB strains showed no significant association between SITs and drug resistance.