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Emergence of a pneumococcal clone with cephalosporin resistance and penicillin susceptibility

A M Smith1, R F Botha, H J Koornhof

  • 1MRC/SAIMR/WITS Pneumococcal Diseases Research Unit, Department of Clinical Microbiology and Infectious Diseases, South African Institute for Medical Research, Johannesburg, South Africa. anthonys@mail.saimr.wits.ac.za

Antimicrobial Agents and Chemotherapy
|August 15, 2001
PubMed

Insights

Two South African pneumococcal isolates show cephalosporin resistance but remain penicillin-susceptible. This resistance is linked to specific gene alterations, while an unaltered gene explains continued penicillin susceptibility in these clonal bacteria.

Area of Science:

  • Microbiology
  • Genetics
  • Antimicrobial Resistance

Background:

  • Streptococcus pneumoniae is a major cause of bacterial infections worldwide.
  • Antibiotic resistance in pneumococci poses a significant public health threat.
  • Understanding resistance mechanisms is crucial for effective treatment strategies.

Purpose of the Study:

  • To characterize two South African isolates of Streptococcus pneumoniae serotype 6B exhibiting unusual antibiotic resistance patterns.
  • To investigate the genetic basis for cephalosporin resistance and penicillin susceptibility in these isolates.

Main Methods:

  • DNA fingerprinting was employed to determine the clonal origin of the isolates.
  • Analysis of penicillin-binding protein (PBP) genes, specifically pbp2X, pbp1A, and pbp2B, was conducted.
  • Phenotypic antibiotic susceptibility testing was performed.

Main Results:

  • Two South African serotype 6B pneumococcal isolates were identified.
  • These isolates displayed resistance to cephalosporins but remained susceptible to penicillin.
  • DNA fingerprinting confirmed the isolates were clonal.
  • Mutations were observed in the pbp2X and pbp1A genes, consistent with cephalosporin resistance.
  • The pbp2B gene showed no alterations, correlating with penicillin susceptibility.

Conclusions:

  • The identified gene alterations in pbp2X and pbp1A are associated with cephalosporin resistance in Streptococcus pneumoniae.
  • The unaltered pbp2B gene is responsible for maintaining penicillin susceptibility in these specific isolates.
  • These findings highlight the complex genetic mechanisms underlying antibiotic resistance and susceptibility in pneumococci.

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