Mechanisms of survival, responses and sources of Salmonella in low-moisture environments

Abstract

Some Enterobacteriaceae possess the ability to survive in low-moisture environments for extended periods of time. Many of the reported food-borne outbreaks associated with low-moisture foods involve Salmonella contamination. The control of Salmonella in low-moisture foods and their production environments represents a significant challenge for all food manufacturers. This review summarizes the current state of knowledge with respect to Salmonella survival in intermediate- and low-moisture food matrices and their production environments. The mechanisms utilized by this bacterium to ensure their survival in these dry conditions remain to be fully elucidated, however, in depth transcriptomic data is now beginning to emerge regarding this observation. Earlier research work described the effect(s) that low-moisture can exert on the long-term persistence and heat tolerance of Salmonella, however, data are also now available highlighting the potential cross-tolerance to other stressors including commonly used microbicidal agents. Sources and potential control measures to reduce the risk of contamination will be explored. By extending our understanding of these geno- and phenotypes, we may be able to exploit them to improve food safety and protect public health.

Microbial Safety of Low Water Activity Foods: Study of Simulated and Durban Household Samples

“…According to Finn et al [5], bacteria have osmoprotectants which aid in bacterial survival in low environments. The function of osmoprotectants is to balance the osmolarity within the bacterial cell to that of the external environment to avoid any loss of water.…”

“…However, many studies done by researchers in literature have found that microorganisms have the capability of surviving in low foods [1,5]. The increased number of food-borne related illness outbreaks recently, associated with low foods, has portrayed that even though microorganisms cannot proliferate in such foods, there is a likelihood for them to be persistent for extended periods of time [1,5,6]. Depending on the type of microorganism, they can cause illness even with their low infectious dose or subsequent temperature abuse that permits the growth of these microorganisms [5].…”

Detection and isolation of Shiga-Toxin producing Escherichia coli in flour in Germany between 2014 and 2017

“…Future systematic studies over periods of time should analyze the factor ''flourmill'' in a systematic way, together with the hygienic and technological conditions. Food business operators producing foodstuff containing uncooked flour should be aware of the possibility of the presence of STEC and should consider the higher thermal stability of STEC in products with low water activity (Finn et al 2013;Liu et al 2014;Knödler et al 2016).…”

“…Pathogenic Enterobacteriaceae may occur in products with low water activity (a w ) and that exhibits higher heat tolerance (Gilbert et al 2010;Finn et al 2013;Beuchat et al 2013). Thermal inactivation of STEC in low moisture foods requires higher temperatures and is strain dependent (Liu et al 2014).…”

“…At temperatures of 70°C, Escherichia coli O157:H7 that was originally isolated from cookie dough was detectable in flour after 30 min (Greene 2012). Under stress, numerous pathogenic bacteria can enter the viable but non culturable stage (VBNC); bacteria enter a metabolically dormant state and consequently are not culturable using conventional laboratory protocols (Finn et al 2013;Knödler et al 2016).…”