Evaluation of Semisolid Rappaport Medium for Detection of Salmonellae in Meat Products

Abstract

The efficiency of semisolid Rappaport medium, brilliant green agar, and bismuth sulfite agar was compared for the recovery of Salmonella from 104 naturally contaminated meat products that had been pre-enriched and subsequently enriched in Rappaport-Vassiliadis broth, Müller-Kauffmann tetrathionate broth, and selenite-F broth. The semisolid Rappaport incubated at 35°C was the most sensitive of the plating media (p<0.01), detecting 90.2% of the 41 samples that were positive with any medium. Incubation of this medium at 43°C increased the specificity to 100%, but clearly lowered sensitivity compared to incubation at 35°C. The best sensitivity-specificity ratio of all the plating media used was obtained with the semisolid Rappaport incubated at 35°C. Its use gave an increase of 36.6% in the number of positive samples, with it also having a bias toward the isolation of the enteritidis serotype of Salmonella.