ABSTRACT
SETTING: Retrospective study of Mycobacterium tuberculosis isolates at the STD/AIDS Cooperative Central Laboratory, Philippines. OBJECTIVE: To describe patterns of M. tuberculosis resistance against first-line anti-tuberculosis drugs, and to analyze the rpoB gene codon mutation of rifampicin (RMP) resistant isolates and correlate genotypic and phenotypic patterns. DESIGN: One hundred and sixty-four M. tuberculosis complex isolates were retrieved for phenotypic analysis; 89 were resistant to any anti-tuberculosis drug and 50 were RMP-resistant, whereas 48 were multidrug-resistant (MDR). Of these 48, only 33 were available for genotypic analysis of the rpoB gene. RESULTS: Most drug-resistant isolates were phenotypically resistant to isoniazid (INH) (93%), and the probability of an RMP-resistant isolate becoming MDR was 96%. In 33 MDR isolates, 13 types of mutations in nine independent codons were identified; the most frequently mutated codons were S531L (61%) and G510H (15%), which were present in 76% (25/33) of the isolates. S531L was noted in 85.7% of the RMP + INH + SM resistant isolates, while only 80% of the isolates with INH + RMP, EMB + SM resistance showed this mutation. CONCLUSION: The high probability of RMP isolates being MDR suggests that genetic analysis of RMP resistance is useful in detecting MDR-TB. Worldwide accumulation of findings on circulating MDR-TB strains provides indispensable information about the re-emergence of TB.
