Comparative studies on the isolation of "sublethally injured" salmonellae in nine European laboratories.

Artificially or naturally contaminated minced meat samples were distributed to nine laboratories and the isolation rates obtained using standardized pre-enrichment and direct enrichment methods were compared. In all laboratories the pre-enrichment method gave higher isolation rates but the difference was less marked with the naturally contaminated samples. Extending the duration of incubation of the liquid enrichment medium to 48 h and making a second subculture improved the isolation rates. The results obtained with selective plates of the laboratories' own choice were unexpectedly poor in comparison with the standard method.