Methicillin-resistant Staphylococcus aureus detection using chromogenic media: the Sheffield experience

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) continues to cause major problems, both in hospitals and the community. Microbiology departments need to review their methodology regularly to ensure that they are contributing in the most appropriate manner to the battle against MRSA. Media employing chromogenic enzymes to aid the isolation and identification of MRSA is a relatively new approach. In this study, 192 swabs from 112 different patients were inoculated on two chromogen-containing media and four other commonly used solid MRSA media to determine which gave the appropriate combination of sensititivity, specificity and speed of result. Methicillin-resistant S. aureus was isolated on at least one of the six media from 102 of the 192 swabs. Both chromogenic media proved to be statistically significantly more sensitive than the other media after overnight incubation and had a sensitivity of 96% after 48 hours’ incubation. The recent introduction of chromogen-containing MRSA media offers microbiology laboratories the opportunity to isolate and confirm the majority of MRSA infections/colonisations in 24 hours, which should result in better patient care. The possible slight increase in costs should not provide a valid excuse for using inferior methodologies.