Frontiers in Biomedical Sciences
Articles Information
Frontiers in Biomedical Sciences, Vol.2, No.1, Jan. 2017, Pub. Date: Feb. 28, 2017
Use of Mannitol Salt Agar (MSA) and Cefoxitin as a Selective Culture Medium for Growing MRSA Strains
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[01] Abdulhadi Sale Kumurya, Department of Medical Laboratory Science, Faculty of Allied Health Sciences, Bayero University, Kano, Nigeria.
Where laboratories are performing antimicrobial susceptibility testing using cefoxitin, Staphylococcus aureus will likely be correctly identified as methicillin-resistant Staphylococcus aureus (MRSA). Importantly, cefoxitin has been found to be more reliable than oxacillin in disc diffusion, broth microdilution, and agar dilution assays. A balanced opening out of this attempt is the inclusion of cefoxitin into media which is selective for MRSA. This work illustrates the testing of mannitol salt agar containing 4 mg/liter cefoxitin with a unique set of well-characterized MRSA strains and an equal number of known methicillin susceptible Staphylococcus aureus (MSSA) strains. The agar supported the growth of 96.6% of the MRSA strains in the set and inhibited the growth of 100% of the MSSA strains. The study indicates that selective media based on cefoxitin are better to those based on oxacillin for the detection of MRSA. The findings of this study demonstrate that cefoxitin is far superior to oxacillin when it is used in mannitol salt medium. By the use of a 48-h incubation and a 102-CFU/ml inoculum, the sensitivity and specificity of the cefoxitin MSA plate method were 100% (compared to 90.7% with oxacillin) and 100% (compared to 96.0% for oxacillin), respectively, when the comparison was made for the strains used in both studies.
MRSA, MSA, Cefoxitin, Selective Media, Growth, Staphylococcus aureus
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