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Properties of methicillin-resistant staphylococci now endemic in Australia
Abstract:
Seventy-eight cultures of multiresistant Staphylococcus aureus (MRSA), obtained from Australian hospitals in 1981, were studied to see whether they possessed novel properties responsible for their epidemic spread. In general, these strains resembled MRSA from other countries and were probably derived from them; in particular, they did not survive desiccation better than other staphylococci. The majority of MRSA produced lipases, which might be responsible for their invasiveness, and all produced high amounts of beta-lactamase which hydrolysed each of the isoxazolyl penicillins. This may account for therapeutic failure with cloxacillin of flucloxacillin. Control of this epidemic should rely principally on general measures against the hospital staphylococcus.
Insights
Australian hospital strains of Methicillin-resistant Staphylococcus aureus (MRSA) showed no novel properties for epidemic spread. Most produced lipases and all produced beta-lactamase, potentially explaining treatment failures with certain penicillins.
Area of Science:
- Microbiology
- Infectious Diseases
- Hospital Epidemiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) strains were isolated from Australian hospitals in 1981.
- The study investigated potential novel properties contributing to the epidemic spread of these MRSA strains.
Purpose of the Study:
- To determine if Australian MRSA strains possessed unique characteristics driving their epidemic spread.
- To understand the enzymatic and survival properties of these MRSA isolates.
Main Methods:
- Analysis of 78 MRSA cultures from Australian hospitals.
- Assessment of desiccation survival compared to other staphylococci.
- Detection of lipase production.
- Quantification of beta-lactamase activity against isoxazolyl penicillins.
Main Results:
- Australian MRSA strains were similar to international counterparts and did not exhibit enhanced survival against desiccation.
- The majority of MRSA strains produced lipases, suggesting a role in invasiveness.
- All isolates produced high levels of beta-lactamase, capable of hydrolyzing isoxazolyl penicillins like cloxacillin and flucloxacillin.
Conclusions:
- The epidemic spread of MRSA in Australian hospitals was not attributed to novel properties like enhanced desiccation survival.
- Lipase production may contribute to MRSA invasiveness.
- High beta-lactamase activity explains therapeutic failures with cloxacillin and flucloxacillin, necessitating general infection control measures against hospital staphylococci.