EVALUATION OF THE TOXICITY OF SALMONELLA SELECTIVE MEDIA FOR SHORTENING THE ENRICHMENT PERIOD

Five Salmonella serotypes recovering from heat injury exhibited different kinetics of resuscitation and growth. Exponential growth was reached before full resuscitation. Fully resuscitated cells and uninjured cells at low cell densities exhibited sensitivity when transferred from non-selective media to selective media, Rappaport-Vassiliadis (RV) and tetrathionate-brilliant green (TBG). The minimum number of cells required to survive in RV and TBG was determined and ranged from 10(2) to 10(5) CFU depending on the serotype. Salmonella grown in RV produced cell populations which exhibited no sensitivity when transferred to fresh RV even at low cell densities. Thus, toxic selective media enriched a resistant population. Selenite cystine exhibited no toxicity to resuscitated or uninjured Salmonella. The significance of these findings was discussed for the purpose of shortening the Salmonella enrichment period.