PCR detection of Salmonella enterica serotype Montevideo in and on raw tomatoes using primers derived from hilA

Salmonellae have been some of the most frequently reported etiological agen ts in fresh-produce-associated outbreaks of human infections in recent year s. PCR assays using four innovative pairs of primers derived from hilA and sirA, positive regulators of Salmonella invasive genes, were developed to i dentify Salmonella enterica serotype Montevideo on and in tomatoes. Based o n examination of 83 Salmonella strains and 22 non-Salmonella strains, we co ncluded that a pair of hilA primers detects Salmonella specifically. The de tection limits of the PCR assay were 10(1) and 10(0) CFU/ml after enrichmen t at 37 degreesC for 6 and 9 h, respectively. When the assay was validated by detecting S. enterica serotype Montevideo in and on artificially inocula ted tomatoes, 10(2) and 10(1) CFU/g were detected, respectively, after enri chment for 6 h at 37 degreesC. Our results suggest that the hili-based PCR assay is sensitive and specific, and can be used for rapid detection of Sal monellae in or on fresh produce.