Transfer Volume-Dependent Recovery of Salmonella from Minced Meat

Six hundred 25-g samples of ground beef were divided into 3 groups of 200 each and 1 drop of a Salmonella broth culture was added to each sample. After storage at -27°C for 3-4 months, the samples were defrosted and blended with 225 ml of buffered peptone water. Ten ml of each suspension was preenriched at 37°C for 20 h and 10-fold dilutions of the material were made. One ml each of the preenriched culture and dilutions of 10^-2, 10^-4, 10^-6, and 10^-8 were transferred to selective enrichment media, and subsequently streaked onto selective agar plates. The mean percentage of Salmonella -positives obtained from all combinations of the selective media in relation to undiluted preenriched material and its 10^-2, 10^-4, 10^-6, and 10^-8 dilutions were for Salmonella typhimurium 70, 81, 84, 37, and 2, for Salmonella choleraesuis 64, 78, 66, 30, and 2, and for Salmonella anatum 60, 84, 75, 40, and 1, respectively. Colonies originating from diluted samples, particularly 10^-4 and further dilutions, usually represented pure cultures of salmonellae, but from undiluted material were frequently accompanied or outgrown by concomitant bacteria.