Unique variations of pbp2x sequences in clinical Streptococcus pneumoniae isolates and penicillin and cefotaxime resistance / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the alternations in gene/amino acid sequence of penicillin-binding protein (PBP)2x from clinical isolates of Streptococcus pneumoniae, and to find the reasons for the rapid surge of penicillin and cefotaxime nonsusceptibility among pneumococcal isolates from Shenyang. Methods Thirty-four strains of Streptococcus pneumoniae were collected from January 2006 to February 2007. The antibiotics susceptibility of these strains was detected. PCR amplification and direct sequencing of pbp2x genes were performed. The sequence variations of PBP genes of the penicillin nonsusceptible Streptococcus pneumoniae(PNSP) in this region were studied by BLAST analysis. Results Two prominent substitutions were common to 12 PNSP isolates for which the MIC of penicillin resistance and cefotaxime were at least 0.5 mg/L, which included the replacement of Thr338→Ala in the first conservative motif STMK and Leu546→Val adjacent to third conservative motif KSG. The importance of the exchange of His394→Leu was identified in one PNSP isolate 15. The remarkable finding in this study was Met342→Ile following the first conservative motif STMK. pbp2x sequences of eight PRSP isolates shared Lys501-Glu505-Thr507 substitutions which might be served as a unique marker for PRSP in this region. Novel gene and amino acid sequence variants in 17 isolate were identified in this study, and these sequences have been deposited in the GenBank database and assigned accession No. EU044831, EU089706-EU089709, EU106881-EU106884 and EU124672. Conclusion It is likely that the emergence of penicillin and cefotaxime nonsusceptible Streptococcus pneumoniae in Shenyang might be associated with novel gene sequence variants.