Development and evaluation of a selective enrichment broth for simultaneous growth of Salmonella enterica serovar Enteritidis, Shigella dysenteriae and Staphylococcus aureus

Abstract

Salmonella enterica, Staphylococcus aureus, and Shigella dysenteriae are the major water-borne and food-borne pathogens, and usually co-exist in very low numbers. Thus, a selective enrichment process is required for their simultaneous detection. Here, we report on the formulation of a selective enrichment broth, namely SSS broth, for the concurrent growth of Salmonella enterica serovar Enteritidis, Shigella dysenteriae, and Staphylococcus aureus. Bacterial growth rates were monitored using a multiplex quantitative real-time PCR system specific to these target pathogens. Bacterial growth kinetics in the SSS broth, individually and collectively, were compared with bacterial counts and kinetics using enrichment broths tailored to each bacterial type. Data showed that the SSS broth had little inhibitory effect on growth of these target pathogens. The concentrations of target bacteria increased from an initial level of 10–103 CFU/ml to 106 CFU/ml after 24 h of culture in both individual and collective cultures. The growth of the non-target bacteria tested in a SSS broth was considerably suppressed. In conclusion, this study has indicated that SSS broth is a selective enrichment broth suitable for the growth of multiple pathogens, which permits simultaneous detection of these pathogens using nucleic-acid- based methods.