CHARACTERIZATION OF RPOB MUTATIONS IN RIFAMPIN-RESISTANT CLINICAL MYCOBACTERIUM-TUBERCULOSIS ISOLATES FROM GREECE

There is a geographic distribution of Mycobacterium tuberculosis strai ns with various rpoB gene mutations that account for rifampin resistan ce, We studied 17 rifampin-resistant clinical isolates from patients i n Greece to identify rpoB mutations, The aim of our study was the eval uation of a commercially available line probe assay kit (INNO-LiPA Rif , TB) to detect rpoB mutations and rifampin resistance, The results ob tained with the commercially available assay were compared to those ob tained by automated DNA sequence analysis of amplified PCR products, R andomly amplified polymorphic DNA (RAPD) analyses of the isolates were also performed, The overall concordance of the line probe assay with phenotypic rifampin susceptibility test was 94%, Three distinct rpoB m utations in codons Ser(531), His(526), and Asp(516) were correctly ide ntified with the kit, but mutations in external regions and insertions were detected only by automated DNA sequence analysis, The changes in codons Ser(531) and His(526) accounted for the majority of rifampin r esistance, as previously described for isolates from other geographic areas, The results obtained by RAPD analyses of the isolates suggested that clonally related M. tuberculosis strains can have subclones bear ing distinct mutant rpoB alleles, We conclude that this line probe ass ay kit, which is fast and with which tests are easy to perform, can be used for the rapid detection of rifampin resistance in M, tuberculosi s before the availability of results by conventional methods and for e pidemiological studies but that negative results obtained by this meth od do not rule out rifampin resistance.