Probability of detection of Salmonella using different analytical procedures, with emphasis on subspecies diarizonae serovar 61:k:1,5,(7) [S. IIIb 61:k:1,5,(7)]

A parameter for assessing qualitative methods is suggested: ‘The probability of detection’ has been used in this study to compare the efficiency of commonly used media for detecting Salmonella in mutton and faeces. Mutton and ovine faeces spiked with strains of Salmonella IIIb 61:k:1,5,(7) and Salmonella Typhimurium were analysed and the performance of each combination of media was estimated. Extensive variation between serovars and strains of identical serovars were recorded. In meat, an inoculum of up to 106/g was needed to detect salmonellae with 90% probability, while in faeces even 107/g was not enough for some strains of S. IIIb 61:k:1,5,(7). All method combinations thus had a rather low efficiency. Based on our experiments, we recommend using a combination of the XLD medium and any of the three selective broths for detection of S. IIIb 61:k:l,5,(7) from mutton, while we recommend using the SC broth with any of the three plating media for detection from ovine faeces.