Staphylococcus aureus: characters associated with its pathogenicity and sensitivity to antibiotics.

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.