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Emergence of a pneumococcal clone with cephalosporin resistance and penicillin susceptibility.

ABSTRACT: We report two South African serotype 6B pneumococcal isolates with cephalosporin resistance, yet with susceptibility to penicillin. DNA fingerprinting revealed that they were clonal in origin. pbp 2X and 1A genes showed major alterations typical of cephalosporin-resistant pneumococci. The pbp 2B gene was completely unaltered, explaining the penicillin susceptibility of the isolates.

SUBMITTER: Smith AM

PROVIDER: S-EPMC90708 | biostudies-literature | 2001 Sep

REPOSITORIES: biostudies-literature

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Emergence of a pneumococcal clone with cephalosporin resistance and penicillin susceptibility.

Smith A M AM Botha R F RF Koornhof H J HJ Klugman K P KP

Antimicrobial agents and chemotherapy 20010901 9

We report two South African serotype 6B pneumococcal isolates with cephalosporin resistance, yet with susceptibility to penicillin. DNA fingerprinting revealed that they were clonal in origin. pbp 2X and 1A genes showed major alterations typical of cephalosporin-resistant pneumococci. The pbp 2B gene was completely unaltered, explaining the penicillin susceptibility of the isolates. ...[more]

PMID: 11502545

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Project description:UnlabelledThe intrinsic resistance of Enterococcus faecium to ceftriaxone and cefepime (here referred to as "cephalosporins") is reliant on the presence of class A penicillin-binding proteins (Pbps) PbpF and PonA. Mutants lacking these Pbps exhibit cephalosporin susceptibility that is reversible by exposure to penicillin and by selection on cephalosporin-containing medium. We selected two cephalosporin-resistant mutants (Cro1 and Cro2) of class A Pbp-deficient E. faecium CV598. Genome analysis revealed changes in the serine-threonine kinase Stk in Cro1 and a truncation in the associated phosphatase StpA in Cro2 whose respective involvements in resistance were confirmed in separate complementation experiments. In an additional effort to identify proteins linked to cephalosporin resistance, we performed tandem affinity purification using Pbp5 as bait in penicillin-exposed E. faecium; these experiments yielded a protein designated Pbp5-associated protein (P5AP). Transcription of the P5AP gene was increased after exposure to penicillin in wild-type strains and in Cro2 and suppressed in Cro2 complemented with the wild-type stpA Transformation of class A Pbp-deficient strains with the plasmid-carried P5AP gene conferred cephalosporin resistance. These data suggest that Pbp5-associated cephalosporin resistance in E. faecium devoid of typical class A Pbps is related to the presence of P5AP, whose expression is influenced by the activity of the serine-threonine phosphatase/kinase system.Importanceβ-Lactam antibiotics remain our most effective therapies against susceptible Gram-positive bacteria. The intrinsic resistance of Enterococcus faecium to β-lactams, particularly to cephalosporins, therefore represents a major limitation of therapy. Although the primary mechanism of resistance to β-lactams in E. faecium is the presence of low-affinity monofunctional transpeptidase (class B) penicillin-binding protein Pbp5, the interaction of Pbp5 with other proteins is fundamental to maintain a resistant phenotype. The present work identifies a novel, previously uncharacterized, protein that interacts with Pbp5, whose expression increases in conjunction with stimuli that increase resistance to cephalosporins, and that confers increased resistance to cephalosporins when overexpressed. P5AP may represent a promising new target, inhibition of which could restore cephalosporin susceptibility to E. faecium.

Dataset Information

Emergence of a pneumococcal clone with cephalosporin resistance and penicillin susceptibility.

Publications

Emergence of a pneumococcal clone with cephalosporin resistance and penicillin susceptibility.

Similar Datasets

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