We made 11 probes that had wild or mutated sequences containing codons 306, 406, or 497 within embB gene respectively. These probes were reverse-hybridized with PCR products amplified from embB gene which were isolated from 149 ethambutol resistant strains and 50 pan-susceptible strains.
RESULTS:
Out of 149 ethambutol resistant strains, one hundred (67.1%) had mutation at least one base at codon 306, 406, or 497 in embB gene. Mutation at codon 306, 406, 497 were demonstrated in 75 (50.3%), 16 (10.7%), and 13 strains (8.7%) respectively. There were four strains that showed multi-mutation at codon 306 and codon 406 simultaneously. A high proportion (8.1%) had single mutation at codon 406. There was no mutation observed in embB gene among 50 pan-susceptible strains.