EVALUATION OF NEW CULTURE MEDIA FOR RAPID DETECTION AND ISOLATION OF SALMONELLAE IN FOODS

Conventional methods for Salmonella detection in foods can require up to 6 and at least 4 days, We have observed that the total analysis tim e can be reduced to 48 h by using Salmosyst broth as a liquid medium f or both preenrichment and selective enrichment and Rambach agar (RA), a new selective plate medium, In samples of artificially contaminated ground beef Salmonella enteritidis was detected at a concentration of 0.4 CFU/g (10 CFU/25 g) by both a conventional method and the new meth od, Of 519 samples of foods for sale, 38 were Salmonella positive by b oth methods while 471 were negative, Nine samples which were negative by the conventional method were positive by the Salmosyst-RA method, w hile one sample positive by the first method was negative by the last. Therefore, the Salmosyst-RA method showed 97.9% sensitivity compared with the 81.2% sensitivity of the conventional method, The new method was also highly specific (98% specificity) in presumptive identificati on of Salmonella colonies. Furthermore, a 6-h preenrichment in Salmosy st broth has been proved sufficient for the repair of heat-injured Sal monella cells and for subsequent recovery by selective enrichment, In conclusion, the Salmosyst-RA method shows several advantages over both conventional acid rapid noncultural methods: (i) only two media are r equired instead of the five media for conventional methods; (ii) in re al time it is comparable to other rapid noncultural methods, which req uire 30 to 31 h; (iii) it is highly sensitive and specific; and (iv) i t allows the isolation of Salmonella strains which can be characterize d by appropriate phenotypic and genotypic typing methods for epidemiol ogical investigations.