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Conjugative R plasmids in antimicrobial resistance of Staphylococcus aureus causing nosocomial infections
Abstract:
Increasing resistance to aminoglycoside antimicrobial agents in clinical isolates of Staphylococcus aureus was encountered in one hospital over a three-year period. Eleven of 16 isolates, selected to represent different time periods, transferred gentamicin resistance on filter membranes with transfer properties and restriction-enzyme analyses that were similar to pAM899-1, a self-transferable gentamicin plasmid previously isolated from Staphylococcus epidermidis within the same hospital. Self-transferable gentamicin R plasmids were demonstrated in isolates from six other nosocomial environments as early as 1974 and, though showing different restriction-enzyme digests, were highly related to pAM899-1 on the basis of Southern hybridization. These recently recognized, self-transferable plasmids seem to share a common evolutionary background and are important contributors to the increased resistance encountered in nosocomial staphylococci.
Insights
Gentamicin resistance in Staphylococcus aureus is increasing due to self-transferable plasmids. These plasmids, similar to pAM899-1, are spreading in hospitals and share a common evolutionary origin, contributing to antimicrobial resistance.
Area of Science:
- Microbiology
- Molecular Biology
- Infectious Diseases
Background:
- Increasing antimicrobial resistance in Staphylococcus aureus poses a significant public health threat.
- Aminoglycoside resistance, particularly to gentamicin, is a growing concern in clinical settings.
- Nosocomial infections caused by resistant staphylococci necessitate understanding resistance mechanisms.
Purpose of the Study:
- To investigate the emergence and characteristics of gentamicin resistance in clinical isolates of Staphylococcus aureus.
- To identify the genetic elements responsible for gentamicin resistance transfer.
- To explore the evolutionary relationship of resistance plasmids in nosocomial staphylococci.
Main Methods:
- Plasmid analysis including filter membrane transfer experiments.
- Restriction enzyme digestion and Southern hybridization techniques.
- Comparative analysis of gentamicin resistance plasmids from various clinical isolates.
Main Results:
- Eleven of 16 Staphylococcus aureus isolates exhibited gentamicin resistance transferable via plasmids similar to pAM899-1.
- Self-transferable gentamicin resistance plasmids were detected in isolates from six other nosocomial environments.
- Southern hybridization indicated a high degree of relatedness between these plasmids and pAM899-1, despite differing restriction patterns.
Conclusions:
- Self-transferable gentamicin resistance plasmids are prevalent in nosocomial staphylococci.
- These plasmids appear to share a common evolutionary background.
- The spread of these plasmids is a key factor in the increasing aminoglycoside resistance observed in hospital-acquired staphylococcal infections.