Serious streptococcal infections produced by isolates resistant to streptogramins (quinupristin/dalfopristin): case

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K C Kugler1, G A Denys, M L Wilson

  • 1Medical Microbiology Division, Department of Pathology, University of Iowa College of Medicine, Iowa City, IA, USA.

Diagnostic Microbiology and Infectious Disease
|April 15, 2000
PubMed

Insights

Antimicrobial resistance is a growing concern. Three Streptococcus strains showed resistance to quinupristin/dalfopristin, even before its clinical introduction, highlighting emerging resistance challenges.

Area of Science:

  • Microbiology
  • Antimicrobial Resistance

Background:

  • Gram-positive organisms exhibit increasing antimicrobial resistance.
  • Quinupristin/dalfopristin is a streptogramin antibiotic with reported activity against resistant Gram-positive bacteria.

Observation:

  • Three Streptococcus spp. isolates (S. mitis, S. pneumoniae) demonstrated resistance to quinupristin/dalfopristin.
  • Resistance was observed in routine isolates within the SENTRY Antimicrobial Surveillance Program.
  • Cross-resistance to other antibiotics like erythromycin, macrolides, lincosamides, and fluoroquinolones was noted in some strains.

Findings:

  • The Streptococcus strains exhibited minimum inhibitory concentrations (MICs) of 3, 8, and 12 microg/ml for quinupristin/dalfopristin.
  • One S. pneumoniae isolate was cross-resistant to erythromycin.
  • Two S. mitis isolates showed resistance to macrolides, lincosamides, and fluoroquinolones.
  • All isolates had elevated penicillin MICs (0.12 microg/ml).
  • The mechanism of resistance to quinupristin/dalfopristin was not identified (sat A-negative).

Implications:

  • These findings indicate the presence of streptogramin-resistant Streptococcus isolates prior to the widespread clinical use of quinupristin/dalfopristin.
  • This underscores the need for ongoing surveillance of antimicrobial resistance patterns.
  • Emergence of resistance necessitates careful monitoring and potential development of alternative therapeutic strategies.

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