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High-level vancomycin-resistant enterococci causing hospital infections
A H Uttley1, R C George, J Naidoo
1Public Health Laboratory, Dulwich Hospital, London.
Abstract:
Nosocomial infection or colonization due to enterococci with high-level resistance to vancomycin (minimal inhibitory concentrations [MICs] between 64 and greater than 2000 mg/L) has occurred in 41 patients with renal disease. These vancomycin-resistant enterococci were cultured from many sources including blood. All but one strain contained one or more plasmids ranging in molecular weight from 1.0 to 40 Megadaltons (MDa). Vancomycin resistance was transferable by conjugation to a susceptible recipient strain of Enterococcus faecalis but this was not always associated with plasmid DNA. The emergence of transferable high-level vancomycin resistance in enterococci causing significant clinical infections is of particular importance since vancomycin is widely regarded as a reserve drug for the management of infections with multi-resistant Gram-positive organisms.
Insights
High-level vancomycin resistance in enterococci has emerged in patients with renal disease. This transferable resistance, often plasmid-mediated, poses a significant threat as vancomycin is a crucial reserve antibiotic.
Area of Science:
- Infectious Diseases
- Microbiology
- Clinical Medicine
Background:
- Nosocomial infections and colonization by vancomycin-resistant enterococci (VRE) are significant healthcare concerns.
- Enterococci exhibiting high-level vancomycin resistance (minimal inhibitory concentrations [MICs] 64–>2000 mg/L) have been identified.
- Patients with renal disease represent a vulnerable population for these infections.
Purpose of the Study:
- To investigate the occurrence and characteristics of high-level vancomycin-resistant enterococci in patients with renal disease.
- To determine the role of plasmids and conjugation in the transferability of vancomycin resistance.
- To highlight the clinical importance of transferable VRE due to vancomycin's role as a last-resort antibiotic.
Main Methods:
- Culturing and characterization of enterococcal strains from various patient samples, including blood.
- Plasmid profiling to identify extrachromosomal DNA elements.
- Conjugation experiments to assess the transferability of vancomycin resistance to susceptible strains.
Main Results:
- Forty-one patients with renal disease were found to have nosocomial infection or colonization with high-level vancomycin-resistant enterococci.
- Most VRE strains harbored plasmids ranging from 1.0 to 40 Megadaltons (MDa).
- Vancomycin resistance was transferable via conjugation, though not consistently linked to plasmid presence.
Conclusions:
- The emergence of transferable high-level vancomycin resistance in enterococci is a critical clinical development.
- These resistant strains, particularly in immunocompromised patients like those with renal disease, pose a substantial therapeutic challenge.
- The findings underscore the need for vigilant surveillance and infection control measures against VRE.