Resuscitation of Injured Salmonella spp. and Coliforms from Foods

Abstract

Because damaged cells may account for a substantial proportion of the bacterial population in processed foods, the food microbiologist must choose the most appropriate methods for detecting damaged as well as noninjured cells. Any method intended to recover damaged organisms should include a resuscitative, or repair, process that will restore the injured cells to a sound physiological condition before subjecting them to the severity of selective enrichment media. It should also provide a reliable indication of the microbiological safety and quality of any particular food. This paper reviews various factors that affect the recovery of Salmonella spp., which include: (a) sample rehydration, (b) period of preenrichment, (c) incubation in both aerobic and anaerobic environments, (d) media composition and (e) the relative merits of preenrichment and direct selective enrichment. Because resuscitation of injured Salmonella cells does not occur during the selective enrichment step and beyond, the effect and interaction of these factors are considered primarily for the preenrichment step of the isolation procedure for Salmonella. This paper also reviews five methods recently developed for recovery of coliforms, which include: (a) hydrophobic grid membrane filtration, (b) radiometry, (c) electrical impedance, (d) fluorogenic assay and (e) the Petrifilm system. Each of these methods may incorporate a step for resuscitation of injured organisms.