Growth of healthy and sanitizer-injured Salmonella cells on mung bean sprouts in different commercial enrichment broths

- Nine broths were evaluated for the enrichment of Salmonella on mung bean sprouts.
- BPW was effective in recovering injured Salmonella and also economically feasible.
- LB failed to recover Salmonella on sprouts at low inoculum levels.
- LAB produced acids during enrichment in LB, which might inhibit Salmonella growth.
- This finding may help improve the detection method for Salmonella on sprouts.

The ability of nine commercial broths to enrich healthy and 90% sanitizer-injured Salmonella Typhimurium and Salmonella cocktail on mung bean sprouts was evaluated to select an optimum broth for detection. Results showed that S. Typhimurium multiplied faster and reached a higher population in buffered peptone water (BPW), Salmonella AD media (AD) and ONE broth-Salmonella (OB), compared with other broths. Healthy and 90% sanitizer-injured Salmonella at low concentrations increased by 4.0 log CFU/ml in these three broths. However, no Salmonella growth was observed in lactose broth (LB). Further investigation showed that during incubation, pH of LB dropped from 6.7 to 4.2, due to production of lactic (66 mM) and acetic acids (62 mM) by lactic acid bacteria that were identified as dominant microbiota in bean sprouts. Though no cell membrane damage was detected by propidium monoazide combined with real-time PCR, it was found that LB inhibited Salmonella growth, especially from low inoculum levels. This study suggests that in consideration of effectiveness and cost, BPW would be a suitable enrichment broth to use for isolating and detecting Salmonella on mung bean sprouts, while using LB might cause false negative results in Salmonella detection by either PCR or standard cultural method.