COMPARISON OF METHODS FOR THE ISOLATION OF METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS

The control of methicillin resistant Staphylococcus aureus (MRSA) reli es on the rapid and sensitive detection of carriage. The roles of an e nrichment broth, duration of incubation, and Baird-Parker medium conta ining ciprofloxacin (BPC) were evaluated in comparison with standard m edia in a centre where the prevalence of ciprofloxacin resistance amon g MRSA is over 98%. Screening swabs from 402 sites were plated onto BP C, mannitol salt agar (MSA), and MSA with methicillin (MMSA). The swab s were enriched in Tryptone-T broth with 6% salt for 24 hours and the broths subcultured onto BPC, MSA, and MMSA. MRSA was isolated from 134 swabs. Significantly more isolates were obtained by incubating cultur e plates for 42 hours rather than 18 hours, by the use of broth enrich ment, and by addition of methicillin or ciprofioxacin to media. BPC wa s the most sensitive medium (107 isolates (80%) by direct culture at 4 2 hours), grew the fewest contaminants, and allowed provisional report ing of 73% of isolates at 18 hours by colonial appearance and use of S taphaurex Plus rapid latex reagent. This may allow the introduction of infection control measures a day earlier than when other established methods are used.