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Clinical isolates of Streptococcus pneumoniae that exhibit tolerance of vancomycin

B Henriques Normark1, R Novak, A Ortqvist

  • 1Department of Bacteriology, Swedish Institute for Infectious Disease Control, Microbiology and Tumor Biology Center, Karolinska Institutet, Solna, Sweden. birgitta.henriques@smi.ki.se

Clinical Infectious Diseases : an Official Publication of the Infectious Diseases Society of America
|February 22, 2001
PubMed

Insights

Three percent of clinical Streptococcus pneumoniae isolates exhibit vancomycin tolerance, a trait that may increase treatment failure risks and facilitate further resistance development. This finding highlights the need for ongoing surveillance of this emerging public health concern.

Area of Science:

  • Microbiology
  • Antimicrobial Resistance
  • Infectious Diseases

Background:

  • Vancomycin tolerance in Streptococcus pneumoniae (pneumococci) is a recently identified phenomenon.
  • This tolerance, the ability to survive antibiotic-induced lysis, poses a potential public health risk in clinical settings.
  • Understanding the prevalence of this tolerance is crucial for assessing its impact on treatment outcomes.

Purpose of the Study:

  • To determine the prevalence of vancomycin and penicillin tolerance in clinical pneumococcal isolates.
  • To characterize the properties of vancomycin-tolerant strains.
  • To evaluate the potential health risks associated with vancomycin tolerance.

Main Methods:

  • 116 clinical isolates of Streptococcus pneumoniae were tested for vancomycin and penicillin tolerance.
  • Tolerance was assessed by monitoring bacterial lysis and viability after 4-hour antibiotic exposure.
  • Minimum bactericidal concentration (MBC) to minimum inhibitory concentration (MIC) ratios were determined for tolerant strains.

Main Results:

  • 3% of isolates were tolerant to vancomycin, and 8% were tolerant to penicillin.
  • Vancomycin-tolerant isolates exhibited high MBC/MIC ratios and were of serotype 9V with reduced penicillin susceptibility.
  • These strains maintained normal growth rates and lysis with deoxycholate, indicating functional autolysin production.

Conclusions:

  • Vancomycin tolerance is present in a small but significant proportion of clinical pneumococcal isolates.
  • This tolerance may contribute to treatment failures, especially in severe infections like meningitis.
  • Ongoing monitoring is necessary to gauge the evolving health risk posed by vancomycin-tolerant pneumococci and their potential for developing further resistance.

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