Cross-protective effect of acid-adapted Salmonella enterica on resistance to lethal acid and cold stress conditions.

AIMS

To evaluate the cross-protected Salmonella enterica cells under acid and cold stress conditions.

METHODS AND RESULTS

The acid-adapted S. enterica cells were exposed to pH 4.0 at 4 and 20 degrees C. Recovery of sublethally injured cells was estimated by the difference between the counts obtained on trypticase soy agar (TSA) and xylose lysine desoxycholate (XLD) agar. The survival curves of nonadapted and acid-adapted S. enterica cells at pH 4.0 were fitted with Weibull distribution model. The recovery behaviour of injured S. enterica cells was estimated by the modified Gompertz parameters. Acid-adapted S. enterica were more resistant to subsequent acid shock than the nonadapted cells. The numbers of nonadapted S. enterica cells were decreased by 457 and 755 log CFU ml(-1) at 4 and 20 degrees C after 12-day acid challenge, respectively. The acid adaptation induced cross-protection and viable nonculturable (VBNC) state against low acid and cold stresses. The 7-h adaptation showed the least recovery of injured cells.

CONCLUSION

The results suggest that acid-adapted S. enterica cells induced acid tolerance response and VBNC state.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results provide useful information for understanding the induction of cross-protected and VBNC pathogens under various stresses, which might be needed in designing new food preservation strategies.