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Staphylococcus aureus: characters associated with its pathogenicity and sensitivity to antibiotics
Abstract:
A hundred staphylococcus strains recently isolated from hospital specimens of various kinds were first divided into two groups: mannitol-positive (90 strains) and mannitol-negative (10 strains). Their ability to produce protein A was then correlated with the presence of other metabolic and enzymatic characters typical of S.aureus. The results showed that satisfactory identification of S. aureus in clinical practice requires assessment of other more species-specific characters in addition to the mannitol fermentation, though this is useful as a preliminary screening measure. Evaluation of protein A production would seem as good or even better than evaluation of coagulase for this purpose. It was also found that the strains examined displayed an increased resistance to methicillin, particularly the part of non-aureus (mainly S.epidermidis) strains. Nearly all strains displayed resistance to the penicillins through the production of penicillinase.
Insights
Accurate identification of Staphylococcus aureus requires more than just mannitol fermentation. Protein A production is a reliable indicator, and many strains show resistance to methicillin and penicillin.
Area of Science:
- Clinical microbiology
- Bacterial identification
- Antimicrobial resistance
Background:
- Staphylococcus aureus is a significant hospital-acquired pathogen.
- Accurate identification of S. aureus is crucial for effective treatment.
- Mannitol fermentation is a common, but not definitive, identification test.
Purpose of the Study:
- To evaluate the reliability of mannitol fermentation for S. aureus identification.
- To assess the utility of Protein A production as an identification marker.
- To investigate antimicrobial resistance patterns in clinical Staphylococcus isolates.
Main Methods:
- Isolation and characterization of 100 Staphylococcus strains from hospital specimens.
- Categorization into mannitol-positive and mannitol-negative groups.
- Correlation of metabolic/enzymatic characters, Protein A production, and coagulase activity.
Main Results:
- Mannitol fermentation alone is insufficient for definitive S. aureus identification.
- Protein A production is a highly effective marker for S. aureus identification, potentially superior to coagulase.
- Increased resistance to methicillin was observed, especially in non-aureus strains (e.g., S. epidermidis).
- Most strains exhibited penicillin resistance via penicillinase production.
Conclusions:
- Clinical identification of S. aureus necessitates evaluating multiple species-specific characteristics beyond mannitol fermentation.
- Protein A assessment offers a robust alternative or adjunct to coagulase testing.
- Rising antimicrobial resistance, including methicillin and penicillin resistance, is a concern in clinical Staphylococcus isolates.