RESISTANCE OF COAGULASE-POSITIVE STAPHYLOCOCCI TO METHICILLIN AND OXACILLIN

Area of Science:

• Microbiology
• Bacteriology
• Antibiotic Resistance

Background:

• Coagulase-positive staphylococci are common pathogens.
• Methicillin and oxacillin are synthetic penicillin antibiotics used against Staphylococcus aureus.
• Emergence of antibiotic resistance in bacteria is a significant concern.

Purpose of the Study:

• To investigate the properties of methicillin-resistant Staphylococcus aureus strains.
• To compare clinical isolates with European strains of resistant staphylococci.
• To understand the mechanisms behind staphylococcal resistance to synthetic penicillins.

Main Methods:

• Isolation and characterization of Staphylococcus aureus strains from a clinical laboratory.
• Testing antibiotic susceptibility using large and small inocula.
• Assessing the enzymatic activity of resistant strains against methicillin and oxacillin.
• Comparing resistant strains with previously identified European isolates.

Main Results:

• Two methicillin-resistant Staphylococcus aureus strains were found among 541 isolates.
• Resistant strains were active penicillinase producers and showed cross-resistance to other antibiotics.
• Resistance was observed primarily with large inocula, with most cells being sensitive.
• Resistant strains slowly destroyed methicillin and oxacillin in vitro, likely due to high penicillinase concentrations.

Conclusions:

• The observed resistance mechanism in Staphylococcus aureus involves penicillinase production.
• Slow antibiotic hydrolysis by penicillinase explains the limited clinical significance of methicillin resistance.
• Further research into staphylococcal resistance mechanisms is warranted.