[Novel gene sequence variants of pbp2b in penicillin-nonsusceptible Streptococcus pneumonia isolates].

OBJECTIVE: To investigate the alternations in gene/amino acid sequence of penicillin-binding protein (PBP)2b from clinical isolates of penicillin-nonsusceptible Streptococcus pneumonia (PNSP) in this region. METHODS: 24 strains of Streptococcus pneumonia were collected from January to December 2006. The antibiotics susceptibility of these strains was detected. PCR amplification and direct sequencing of pbp2b genes were performed. The sequence variations of PBP genes of the PNSP in this region were studied with sequence BLAST analysis. RESULTS: Three prominent substitutions were common to 13 PNSP isolates with minimal inhibitory concentration (MIC) at least 0.1 mg/L. These included the replacement of Thr(445)--> Ala following the conservative motif SSN, Glu(475)-->Gly and Thr(488)-->Ala/Ser. The exchange of Glu(332)-->Gly was identified in 12 PNSP isolates of which the MIC was at least 0. 25 mg/L. Seven penicillin resistant Streptococcus pneumonia (PRSP) isolates (MIC > or = 3 mg/L) shared the amino acid substitution Ala(618)-->Gly adjacent to third conserved (KTG) motif and the PBP2b sequences of seven PRSP isolates were classified within Baek's group II and were very similar to those of the Korean J77 isolate. Novel gene and amino acid sequence variants in isolate 14, 15, 8, 11 and 24 was identified in this study and these gene sequences have been deposited in the GenBank database and assigned accession no. EU035970, EU056919, EU056920, EU056921 and EU106886. CONCLUSION: Analysis of pbp2b genes revealed highly similar patterns of nucleotide and amino acid sequence variation among most resistant isolates, while penicillin intermediate Streptococcus pneumonia might be associated with novel gene sequence variants.