Staphylococcus Research Today is a free monthly online journal that collates and summarizes the latest research about Staphylococcus, including details on mrsa, hospitals, infection, antibiotic resistance, superbugs.

Mannitol salt agar-cefoxitin combination as a screening medium for methicillin-resistant Staphylococcus aureus.

Smyth RW, Kahlmeter G

Department of Clinical Microbiology, Central Hospital, SE 351 85 Växjö, Sweden. robert.smyth@ltkronoberg.se

In disk diffusion tests, cefoxitin is now considered a better indicator than oxacillin for the presence of the mecA gene in Staphylococcus aureus. A logical extension of this work is the incorporation of cefoxitin into media selective for methicillin-resistant Staphylococcus aureus (MRSA). This paper describes the development and subsequent testing of mannitol salt agar containing 4 mg/liter cefoxitin with a unique collection of well-characterized MRSA strains, including low-level methicillin-resistant strains and an equal number of known mecA-negative S. aureus strains. The agar supported the growth of 96.6% of the mecA-positive strains in the collection and inhibited the growth of 100% of the mecA-negative strains. These results suggest that selective media based on cefoxitin are superior to those based on oxacillin for the detection of MRSA.

Published 5 August 2005 in J Clin Microbiol, 43(8): 3797-9.
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