Association of a Thr-371 Substitution in a Conserved Amino Acid Motif of Penicillin-Binding Protein 1A with Penicillin Resistance of Streptococcus pneumoniae

Abstract

We determined the nucleotide sequence between 1,903 and 3,097 bp ofpbp1a, which encodes the transpeptidase domain of PBP 1A, from clinical isolates of penicillin-resistant Streptococcus pneumoniae (PRSP) serotypes 19 (n = 8), 6 (n = 9), 23 (n = 6), and 14 (n = 2) and two penicillin-susceptible S. pneumoniae (PSSP) isolates. These serotyped PRSP strains were isolated predominantly in Japan from 1993 through 1997. The 25 resistant strains were classified into five groups on the basis of the extent of sequence differences. Strains in groups I (n= 5; serotype 6), II (n = 3; serotype 19), and III (n = 12; different serotypes) had sequences highly homologous to the sequence of pbp1a of PRSP strains from South Africa, Spain, and the United States. The group IV strain (n = 1; serotype 14) had unique deletions from or insertions in the sequences. The sequences of group V strains (n = 4; serotypes 6 and 23) had relatively few differences from the sequences of the PSSP strains. For strains (n = 18) for which the threonine at codon 371 (Thr-371) in a conserved STMK motif of PBP 1A was substituted with an alanine or a serine (in addition to having altered pbp2xand pbp2b genes), penicillin MICs were ≧1.0 μg/ml. The PBPs 1A of these strains showed decreased affinities for [3H]benzylpenicillin and slightly faster mobilities on sodium dodecyl sulfate-polyacrylamide gels. In contrast, for strains (n = 4) without a substitution at Thr-371 in PBP 1A but with mutations in both pbp2x and pbp2b, penicillin MICs were 0.125 to 0.25 μg/ml, and the affinities of their PBPs 1A were similar to that of PSSP PBPs 1A. Furthermore, for the Thr-371-substituted strains (n = 3) with alteredpbp2x genes but native pbp2b genes, penicillin MICs were 0.125 to 0.25 μg/ml. These results suggest that amino acid substitution of Thr-371 contributes to the development of penicillin resistance in PRSP strains with altered pbp2x andpbp2b genes.

Crystal Structure of Penicillin-binding Protein 1a (PBP1a) Reveals a Mutational Hotspot Implicated in β-Lactam Resistance in Streptococcus pneumoniae

“…Sequence alignment of PBP1a from wild-type and mutant S. pneumoniae strains. Sequences from drug-sensitive R6 laboratory strain (MIC pen Z0.03 mg/ml), 56 S. African isolate 8303 (MIC pen Z4 mg/ml), 16 Japanese isolate 5/H31 (MIC pen Z2 mg/ml), 57 and French isolate 73311 (MIC pen Z8 mg/ml) 30 are shown. Dashes represent regions of the sequences that were not available in SwissProt.…”

Problems associated with high prevalence of multidrug-resistant bacteria in patients with community-acquired infections

“…Resistance to -lactams in these pathogens involves alterations of penicillin-binding proteins (PBPs) encoded by PBP genes. [6][7][8][9][10][11][12][13] Macrolide resistance in S. pneumoniae is mediated by the efflux membrane protein encoded by the mefA gene, [14][15][16][17] methylation of the ribosomal protein encoded by the ermB gene, 18 and 23S rRNA mutation. 19 Resistance of S. pneumoniae to the newer quinolones is mediated by mutations involving DNA gyrase encoded by the gyrA gene, 20 topoisomerase IV encoded by the parC and parE genes, 21 and efflux membrane protein encoded by the pmrA gene.…”

In vitro activities of new ketolide, telithromycin, and eight other macrolide antibiotics against Streptococcus pneumoniae having mefA and ermB genes that mediate macrolide resistance

“…The nucleotide sequences were determined according to previously described methods. 21 The data will appear in the DDBJ, EMBL, and Gene Bank nucleotide sequence databases with the accession numbers AB011258 and AB011259.…”