SMYTH RW, KAHLMETER G; Interscience Conference on Antimicrobial Agents and Chemotherapy (43rd: 2003: Chicago, Ill.).

Abstr Intersci Conf Antimicrob Agents Chemother Intersci Conf Antimicrob Agents Chemother. 2003 Sep 14-17; 43: abstract no. D-1683.

Central Hospital, Vaxjo, Sweden.

BACKGROUND: The predictive value of a cefoxitin disk diffusion test for detection of low-level methicillin resistance in Staphylococcus aureus has recently found to be high. There are as yet no published reports of the performance of cefoxitin in a selective medium for the detection of methicillin resistant S. aureus in screen samples. METHODS: A collection of 79 mecA-positive S. aureus (MRSA) and 89 mecA-negative S. aureus strains (MSSA) was tested on Mannitol Salt Agar (Mast, UK) containing a cefoxitin (Sigma-Aldrich) concentration of 4 mg/L. The collection contained more than 22 different PFGE types (e.g. Berlin IV, Finland E7, France A and B, S German II, UK E1, E15, and E16, Spain E1). RESULTS: The medium supported the growth of 52 MRSA after 24 hours and of all MRSA after 48 hours incubation with an inoculum size of 10[2] CFU. Furthermore, the growth of all MSSA strains, including 14 BORSA strains, was suppressed at an inoculum size of both 10[2] and 10[5] CFU. The sensitivity and specificity of Mannitol Salt Agar with 1mg/L oxacillin for this collection of MRSA strains had been previously established as 90.7% and 96.0% respectively. CONCLUSION: Mannitol Salt cefoxitin medium would therefore seem to be superior both in terms of sensitivity and specificity, to screening media containing oxacillin. An additional advantage over oxacillin-containing media is that the shelf-life of this medium is a full 30 days. However, an incubation of 48 hours is still required in order to exclude MRSA.

Publication Types:

• Meeting Abstracts

Keywords:

• Agar
• Berlin
• Cefoxitin
• Finland
• France
• Mannitol
• Methicillin Resistance
• Oxacillin
• Sodium Chloride
• Sodium Chloride, Dietary
• Spain
• Staphylococcal Infections
• Staphylococcus aureus

Other ID:

• GWAIDS0025521

UI: 102265145

From Meeting Abstracts