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Molecular characterization of Staphylococcus sciuri strains isolated from humans
I Couto1, I S Sanches, R Sá-Leão
1Molecular Genetics Unit, Instituto de Tecnologia Química e Biológica da Universidade Nova de Lisboa (ITQB/UNL), 2781-156 Oeiras, Portugal.
Journal of Clinical Microbiology
|March 4, 2000
Summary
Staphylococcus sciuri commonly carries a unique mecA gene. Some strains also possess the methicillin-resistant Staphylococcus aureus (MRSA) mecA gene, leading to beta-lactam resistance, even in healthy individuals.
Area of Science:
- Microbiology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Staphylococcus sciuri isolates, primarily from animals, were previously found to carry a unique mecA gene (S. sciuri mecA).
- A subset of these isolates also harbored a second copy of the mecA gene identical to that found in methicillin-resistant Staphylococcus aureus (MRSA).
Purpose of the Study:
- To analyze a collection of 28 S. sciuri strains from diverse sources (healthy and hospitalized individuals).
- To investigate the prevalence and implications of both S. sciuri mecA and MRSA mecA gene copies in these strains.
- To confirm the role of S. sciuri in the evolution of methicillin resistance within staphylococci.
Main Methods:
- Analysis of 28 S. sciuri strains isolated from various human sources.
- Pulsed-field gel electrophoresis (PFGE) to assess strain heterogeneity.
- Detection and characterization of mecA gene copies (S. sciuri mecA and MRSA mecA).
- Phenotypic antibiotic susceptibility testing (beta-lactams, clindamycin, tetracycline, erythromycin, gentamicin).
Main Results:
- All 28 S. sciuri strains possessed the S. sciuri mecA gene, supporting its status as part of the species' genetic background.
- 46% of the strains also carried the MRSA mecA copy, and these were the only strains exhibiting significant beta-lactam resistance.
- Strains with the additional MRSA mecA copy were predominantly isolated from healthy individuals, often from antibiotic-free environments.
- Most strains were resistant to penicillin, with intermediate resistance to clindamycin and susceptibility to tetracycline, erythromycin, and gentamicin.
Conclusions:
- Staphylococcus sciuri plays a significant role in the evolutionary pathway of methicillin resistance in staphylococci.
- The presence of the MRSA mecA gene in S. sciuri contributes to beta-lactam resistance.
- S. sciuri strains, similar to pathogenic staphylococci, can acquire and accumulate multiple antibiotic resistance markers.