The persistence of Salmonella following desiccation under feed processing environmental conditions: a subject of relevance.

UNLABELLED: Although Salmonella persistence has been predominantly linked to biofilm formation, the physiological state of Salmonella should also be considered as a possible pathway for persistence and survival in the feed industry. Hence, the purpose of this study was to assess the extent of viability of Salmonella cells through long-term desiccation periods under conditions typically found in feed processing environments, and whether these same cells could resuscitate and cause salmonellosis in vivo. We showed that upon desiccation, Salmonella Agona, a representative feed industry isolate and Salmonella Typhimurium ATCC 14028, a laboratory strain, were induced into a nonculturable state at 35 and 85% relative humidity conditions, at defined temperatures of 30 and 12°C, respectively. Although the reduction in culturable cells was more than 6 log10 , metabolic activity was found in more than 1% of the population. Desiccation-induced nonculturable Salm. Typhimurium could not be revived and were nonvirulent in a mouse model following infection through oral gavage. These results suggest that the specific conditions for reviving nonculturable Salmonella after long periods of desiccation are yet to be fully identified. The need for mapping key factors involved in the persistence of Salmonella would help better detect it and improve feed safety measures. SIGNIFICANCE AND IMPACT OF THE STUDY: While Salmonella has been shown to persist for years in feed processing environments, it is still unknown how temperature and humidity affect the persistence of Salmonella cells over time in terms of their metabolic states and cultivability. Here, we show that long-term exposure to feed processing environmental conditions induces Salmonella into a nonculturable state even though about 1% of the population remains metabolically active. This has significant implications when monitoring Salmonella from the environment which could yield false-negative results using conventional pre-enrichment detection methods.

Synthetic brominated furanone F202 prevents biofilm formation by potentially human pathogenic Escherichia coli O103:H2 and Salmonella ser. Agona on abiotic surfaces.

AIMS: Investigate the use of a synthetic brominated furanone (F202) against the establishment of biofilm by Salmonella ser. Agona and E. coli O103:H2 under temperature conditions relevant for the food and feed industry as well as under temperature conditions optimum for growth. METHODS AND RESULTS: Effect of F202 on biofilm formation by Salmonella ser. Agona and E. coli O103:H2 was evaluated using a microtiter plate assay and confocal microscopy. Effect of F202 on bacterial motility was investigated using swimming and swarming assays. Influence on flagellar synthesis by F202 was examined by flagellar staining. Results showed that F202 inhibited biofilm formation without being bactericidal. F202 was found to affect both swimming and swarming motility without, however, affecting the expression of flagella. CONCLUSIONS: F202 showed its potential as a biofilm inhibitor of Salmonella ser. Agona and E. coli O103:H2 under temperature conditions relevant for the feed and food industry as well as temperatures optimum for growth. One potential mode of action of F202 was found to be by targeting flagellar function. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study gives valuable new knowledge to the potential use of furanones as a tool in biofilm management in the food and feed industry.

A synthetic furanone potentiates the effect of disinfectants on Salmonella in biofilm.

AIMS: To study a possible effect of a synthetic brominated furanone on biofilm formation and biofilm resistance to disinfectants in Salmonella enterica. METHODS AND RESULTS: The effect of a synthetic furanone on biofilm formation of Salm. enterica serovar Agona and Salm. enterica serovar Typhimurium (11 strains of different origins) was evaluated in a microtiterplate assay. A significant reduction in biofilm build-up in microtiterplates by the furanone was observed for seven of the strains tested. Biofilms by two Salm. Agona feed factory strains and the effects on survival after exposures to disinfectants (hypochlorite and benzalkonium chloride) were assessed for both strains. Pretreatment with furanone significantly potentiated the effect of the two disinfectants for both strains. CONCLUSIONS: The effect of disinfectants on Salmonella in biofilm was significantly enhanced when the biofilm was grown in the presence of furanone. This was probably because of an effect on biofilm architecture, composition and in some cases also biofilm build-up. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study gives valuable new knowledge in the fight against Salmonella biofilm in the environment because of the potentiated effect of conventional disinfectants.

Evaluation of efficacy of disinfectants against Salmonella from the feed industry.

AIMS: To evaluate disinfectants against Salmonella under conditions relevant for the feed industry. MATERIALS AND RESULTS: A survey on the use of disinfectants in feed industry showed that a range of different types was used. Nine disinfectants, reflecting the most commonly used active ingredients, were tested for bactericidal activity on Salmonella isolated from the feed industry. All disinfectants were efficient against Salmonella in suspension. The bactericidal effect varied considerably between different types of active compounds on bacteria dried on surfaces or grown as biofilm. Tenside-based disinfectants and hypochlorite were found to have low bactericidal activity and the efficiency was significantly reduced when the ratio of amount disinfectant per cell decreased. It was shown that concentrations of 70-80% ethanol were effective against Salmonella. Among the disinfectants tested a product containing 70% ethanol was most efficient followed by Virkon S. CONCLUSIONS: Many disinfectants had low bactericidal activity against Salmonella at surfaces while Virkon S and a product containing 70% ethanol were most effective. Another advantage of ethanol-based disinfectants is evaporation of ethanol, resulting in low residual water after use. SIGNIFICANCE AND IMPACT OF THE STUDY: Use of the disinfectants found to be efficient against surface associated Salmonella, may assist the industry in combating Salmonella.