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Genetic heterogeneity in pbp genes among clinically isolated group B Streptococci with reduced penicillin

Noriyuki Nagano1, Yukiko Nagano, Kouji Kimura

  • 1Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashi-Murayama, Tokyo 208-0011, Japan. yarakawa@nih.go.jp.

Antimicrobial Agents and Chemotherapy
|September 24, 2008
PubMed

Insights

Group B Streptococcus strains show increasing penicillin resistance due to mutations in penicillin-binding proteins (PBPs), particularly PBP 2X. These genetic changes suggest independent emergence rather than epidemic spread of resistant strains.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Group B Streptococcus (GBS) is a significant cause of neonatal infections.
  • Emergence of GBS isolates with increased penicillin minimum inhibitory concentrations (MICs) has been observed.
  • Penicillin-binding proteins (PBPs) are crucial targets for beta-lactam antibiotics.

Purpose of the Study:

  • To comparatively analyze penicillin-binding proteins (PBPs) in penicillin-susceptible and resistant Group B Streptococcus strains.
  • To investigate the genetic basis of reduced penicillin susceptibility in GBS.

Main Methods:

  • Comparative analysis of PBP sequences from susceptible and resistant GBS isolates.
  • Identification of amino acid substitutions in PBPs, especially PBP 2X and PBP 2B.
  • Assessment of Bocillin FL binding to PBPs.
  • Analysis of pbp2x gene transcription levels.

Main Results:

  • Penicillin-susceptible GBS strains showed highly conserved PBP sequences.
  • Resistant strains exhibited unique sets of amino acid substitutions in PBP 2X and PBP 2B.
  • Reduced Bocillin FL binding was observed in PBPs of some resistant strains, notably PBP 2X.
  • No significant reduction in pbp2x transcription was detected in resistant strains.

Conclusions:

  • Multiple, independent genetic lineages of penicillin-resistant GBS are emerging.
  • Accumulation of mutations in PBP genes, particularly pbp2x, drives penicillin resistance.
  • The findings suggest an absence of epidemic penicillin-resistant GBS strains.

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