DETECTION OF RIFAMPIN RESISTANCE AMONG ISOLATES OF MYCOBACTERIUM-TUBERCULOSIS FROM MOZAMBIQUE

Rifampin resistance in respiratory isolates of Mycobacterium tuberculo sis from Mozambique was detected by screening for point mutations usin g polymerase chain reaction (PCR) and DNA sequence analysis. The targe t template was a 350-bp fragment of rpoB encoding the beta-subunit of the RNA polymerase. Of the 66 strains studied, 38 mere rifampin resist ant by susceptibility testing with the radiometric method, 3 were inte rmediately resistant, and 25 were susceptible to rifampin, In 39 of th e 41 rifampin-resistant strains, base-substitutions in the rpoB fragme nt were detected, and a total of 13 distinct mutations affecting 6 ami no acids were observed. One of these mutations (His --> Thr in amino a cid 526) was not previously described, The isolates were also investig ated by restriction fragment length polymorphism (RFLP) analysis using the insertion element IS6110 as a hybridization probe, A total of 47 RFLP patterns were identified, with np to 9 isolates having the same R FLP pattern, Strains with the same RFLP pattern harbored different mut ations in rpoB, suggesting that acquisition of rifampin resistance fol lowed the spread of a rifampin-susceptible clone. The data showed that rifampin resistance can be detected with a high sensitivity by DNA se quence analysis of this fragment of rpoB, However, a few strains with rifampin resistance due to factors other than base substitutions in rp oB could be missed.