Characterization of clinical isolates of Mycobacterium tuberculosis resistant to drugs and detection of RpoB mutation in multidrug-resistant tuberculosis in the Philippines.
METHODS
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.


METHODS
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.


CONCLUSIONS
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.
Laboratory, San Lazaro Hospital, Manila, Philippines. slh@compass.com.ph
D M D
DM
Agdamag
S
S
Kageyama
R
R
Solante
A S
AS
Espantaleon
J C E
JC
Sangco
Y
Y
Suzuki
D003062:Codon / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D004977:Ethambutol / Q000494:pharmacology; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D010641:Phenotype; D010679:Philippines; D012189:Retrospective Studies; D012293:Rifampin / Q000494:pharmacology; D016036:Seroepidemiologic Studies
D003062:Codon; D004977:Ethambutol; D012321:DNA-Directed RNA Polymerases; C105078:RNA polymerase beta subunit; D007538:Isoniazid; D012293:Rifampin