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Multiple antibiotic resistance in Staphylococcus aureus and Staphylococcus epidermidis: plasmids in strains
Abstract:
The plasmid DNA profiles were compared to phenotypically-similar, antibiotic-resistant strains of Staphylococcus aureus and Staphylococcus epidermidis associated with nosocomial infections in a Melbourne hospital. Whereas resistance to gentamicin, tobramycin and kanamycin was encoded by one of 3 plasmids [pSK1, 18 megadalton (Md); pSK4, 22 Md; pSK9, 17 Md] in S. aureus, no similar plasmids were detected in S. epidermidis. Mediated exclusively by the chromosome in S. aureus, tetracycline resistance was encoded either by the chromosome or by a 2.8 Md plasmid in strains of S. epidermidis. The inability to detect common resistance plasmids in strains of S. aureus and S. epidermidis recovered from this outbreak is in contrast to recent observations with staphylococci from other geographic areas; nevertheless, on the basis of restriction endonuclease analyses of 3 Md chloramphenicol resistance plasmids, it is suggested that a common gene pool does exist within isolates of S. aureus and S. epidermidis from Melbourne hospitals.
Insights
Antibiotic resistance in hospital-acquired Staphylococcus strains was investigated. While some resistance genes were plasmid-borne in Staphylococcus aureus, they were chromosomal or plasmid-borne in Staphylococcus epidermidis, suggesting a shared gene pool.
Area of Science:
- Clinical Microbiology
- Molecular Biology
- Infectious Diseases
Background:
- Nosocomial infections caused by antibiotic-resistant Staphylococcus aureus and Staphylococcus epidermidis pose significant healthcare challenges.
- Understanding the genetic basis of antibiotic resistance in these pathogens is crucial for effective treatment and control strategies.
- Previous studies have indicated the role of plasmids in mediating antibiotic resistance in staphylococci.
Purpose of the Study:
- To compare plasmid DNA profiles of antibiotic-resistant Staphylococcus aureus and Staphylococcus epidermidis strains from a Melbourne hospital outbreak.
- To identify the genetic elements responsible for resistance to specific antibiotics, including gentamicin, tobramycin, kanamycin, and tetracycline.
- To investigate the potential for a common gene pool of resistance determinants between Staphylococcus aureus and Staphylococcus epidermidis.
Main Methods:
- Plasmid DNA profiling was performed on antibiotic-resistant strains of Staphylococcus aureus and Staphylococcus epidermidis.
- Restriction endonuclease analysis was used to characterize chloramphenicol resistance plasmids.
- Antibiotic resistance genes were analyzed in relation to both plasmid and chromosomal DNA.
Main Results:
- In Staphylococcus aureus, resistance to gentamicin, tobramycin, and kanamycin was encoded by plasmids ranging from 17 to 22 megadaltons (Md).
- No similar plasmids were detected in Staphylococcus epidermidis strains; tetracycline resistance was chromosomal or plasmid-mediated (2.8 Md).
- Restriction endonuclease analysis of 3 Md chloramphenicol resistance plasmids suggested a common gene pool between Staphylococcus aureus and Staphylococcus epidermidis isolates.
Conclusions:
- The genetic basis of antibiotic resistance differs between Staphylococcus aureus and Staphylococcus epidermidis in this Melbourne hospital outbreak.
- Despite differences in plasmid-borne resistance, evidence suggests a shared gene pool for resistance determinants, particularly for chloramphenicol resistance.
- Further investigation into interspecies gene transfer mechanisms is warranted to understand the evolution of antibiotic resistance in staphylococci.