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Concomitant high-level vancomycin and penicillin resistance in clinical isolates of enterococci
S Handwerger1, D C Perlman, D Altarac
1Department of Medicine, Beth Israel Medical Center, Mount Sinai School of Medicine, New York, New York 10003.
Abstract:
Enterococci are important nosocomial pathogens among which resistance to multiple antibiotics is being recognized with increasing frequency. We characterized three clinical isolates from three New York City hospitals that demonstrated concomitant resistance to vancomycin (one VanA, two VanB phenotypes) and high-level resistance to penicillin. Two Enterococcus faecium strains were intrinsically highly resistant to penicillin and showed very low affinity for penicillin of penicillin-binding protein 5. Unlike previously described glycopeptide-resistant enterococci, these strains were not hypersusceptible to beta-lactam agents after vancomycin induction, and combinations of penicillin and vancomycin were not synergistic against them. A third isolate, Enterococcus faecalis, produced beta-lactamase. Two of the three strains were also highly resistant to all aminoglycosides. Emergence of concomitant high-level resistance to multiple antibiotic classes among enterococci considerably narrows the therapeutic options for treatment of infections due to these opportunistic pathogens.
Insights
This study highlights emerging multidrug-resistant enterococci, including strains resistant to vancomycin and penicillin. These resistant enterococci (Enterococcus) present significant challenges for treating hospital-acquired infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Enterococci are significant causes of hospital-acquired infections.
- Increasing antibiotic resistance in enterococci necessitates understanding novel resistance mechanisms.
Observation:
- Three clinical enterococcal isolates from New York City hospitals exhibited co-resistance to vancomycin (VanA and VanB phenotypes) and high-level penicillin resistance.
- Two Enterococcus faecium strains showed intrinsic penicillin resistance and low penicillin-binding protein 5 affinity.
- One Enterococcus faecalis isolate produced beta-lactamase.
Findings:
- Unlike other vancomycin-resistant enterococci, these strains did not show increased susceptibility to beta-lactams after vancomycin induction.
- Penicillin and vancomycin combinations were not synergistic against these isolates.
- Two strains demonstrated high-level resistance to all aminoglycosides.
Implications:
- The emergence of enterococci with resistance to multiple antibiotic classes, including vancomycin and penicillin, severely limits treatment options.
- These findings underscore the urgent need for surveillance and development of new therapeutic strategies against multidrug-resistant enterococci.