Formation of viable but nonculturable Salmonella during starvation in chemically defined solutions

Salmonella enteritidis enters a viable-but-nonculturable state when exposed to starvation in aquatic environments. This study determined starvation survival of this pathogen in chemically defined solutions and tested the ability of nonselective enrichment to detect viable-but-nonculturable cells. Starvation of Salm. enteritidis at 7 degrees C in 7.35 mmol l-1 potassium phosphate buffer resulted in complete loss of culturability after 5 weeks with maintenance of a substrate-responsive population of over 10,000 cell ml-1. Starvation at 21 degrees C and starvation in saline solutions or lower concentrations of phosphate buffer resulted in prolonged survival of a culturable population although this population was lower than the total viable population. Enrichment using lactose broth did not allow resuscitation of viable-but-nonculturable cells even after 5 d of incubation at 35 degrees C.