Search

The Beijing genotype of Mycobacterium tuberculosis has frequently been found to be associated with drug resistance. Mutation analysis of the genes encoding 16S rRNA ( rrs ) and ribosomal protein S12 ( rpsL ) revealed a high frequency (97/102; 95.1%) of alterations in streptomycin-resistant M. tuberculosis isolates from Singapore, with rpsL K43R being the most common rpsL mutation (82/92; 89%), which was significantly associated with Beijing strains compared to non-Beijing strains (odds ratio=10.88, 95% confidence interval=3.48–34.1). This is the first study to report the association of Beijing strains with the rpsL K43R mutation in STR-resistant M. tuberculosis isolates with de novo resistance, as determined by clustering analysis.

The distribution of hepatitis C viral (HCV) genotypes in Singapore has not been previously determined. We studied the sera of 40 Singapore patients which were PCR-positive for HCV. The HCV genotypes were determined by direct sequencing of amplified sequences of the 5′ non-coding region, after reverse transcription. Of the 40 samples, 35/40 (87.5%) were of HCV type 1, 2/40 (5.0%) were of type 2 and 3/40 (7.5%) were of type 3. The most common HCV genotype in this study was the type 1 genotype. Our results confirm the wide geographical distribution of HCV genotypes.

Previous studies have suggested that Mycobacterium tuberculosis kasA G312S and G269S gene mutations may represent sequence polymorphisms of the M. tuberculosis East-African-Indian (EAI) and T families, respectively, rather than relating to isoniazid resistance. The present study examined polymorphisms of these two codons in 98 drug-susceptible M. tuberculosis isolates (68 EAI and 30 T isolates). Twenty-eight isolates belonging to a sub-lineage of the EAI family had the kasA G312S mutation, but none of the 30 T isolates had the G269S mutation. The data suggest that the kasA G312S mutation is not related to isoniazid resistance, but represents a sequence polymorphism in a sub-lineage of the EAI family.