Genetic analysis of pbp2x in clinical Streptococcus pneumoniae isolates in Quebec, Canada

Abstract

Objectives: To investigate the nature of the amino acid motifs found in penicillin-binding protein (PBP) 2x of penicillin-resistant Streptococcus pneumoniae isolates across the province of Quebec (Canada), and to obtain preliminary information regarding the prevalence of these alterations. Methods: The pbp2x genomic region encompassing codons 178-703, which includes the entire region of the transpeptidase domain, was sequenced and compared for 52 clinical isolates comprising 20 penicillin-susceptible (PSSP), 20 penicillin-intermediate (PISP) and 12 penicillin-resistant (PRSP) pneumococci. Results: The degree of diversity within PBP2x correlated with increased resistance to β-lactam antibiotics. There were an average of 5.0 ± 1.8 mutations in PSSP, 37.9 ± 4.4 in PISP, and 63.0: ± 2.0 in PRSP isolates when compared with the control penicillin-susceptible strain R6. At least six distinct amino acid profiles were identified among PISP strains isolated in Quebec. In contrast, all PRSP isolates shared a similar pattern of altered amino acids compared with the sequence from susceptible strains. Conclusions: These data will be useful in future studies to monitor the genetic changes associated with the emergence and spread of β-lactam resistance in Quebec. © The Author 2005. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.