Salmonella enterica serovar Typhimurium strains were isolated during a monitoring survey of the carpet shell clam (Ruditapes decussatus) collected from 23 stations along the Tunisian coast. The effect of starvation on Salmonella Typhimurium survival was investigated in vitro using microcosms composed of filtered (0.2 µm) marine water under dark and ambient temperature conditions (25C for 30 days). Eventual changes in physiological, biochemical properties, serotyping, biotyping and antimicrobial sensitivity for the environmentally adapted Salmonella Typhimurium were monitored. In response to stress conditions, the Salmonella Typhimurium strains progressively lost culturability in the absence of notable changes in the total cell count (during all the period of 30 days). Strains appeared to enter into a viable but noncultureable state as determined by epifluorescence method. We have also observed that the T90 value (time required for the reduction of 90% of cells) for the five different Salmonella strains ranged between 25 and 30 h; this indicated the survivability of Salmonella under stress conditions. This state was also characterized by biochemical and antimicrobial changes. PRACTICAL APPLICATION This research highlighted the acquisition of the viable but nonculturable state of bacteria. This form of adaptation of certain pathogens does not really reflect their presence or absence in the marine environment and thus in foods of marine origin. Hence the use of conventional methods of bacterial identification must be completed more advanced research tools before declaring a healthy product or environment.
This study investigated survival and virulence of Escherichia coli strains exposed to natural conditions in brackish water. Two E. coli strains (O126:B16 and O55:B5) were incubated in water microcosms in the Bizerte lagoon in Northern Tunisia and exposed for 12 days to natural sunlight in June (231 to 386 W/m2, 26 ± 1 °C, 30 g/L) and in April (227 to 330 W/m2, 17 ± 1 °C, 27 g/L) or maintained in darkness for 21 days (17 ± 1 °C, 27 g/L). The results revealed that sunlight was the most significant inactivating factor (decrease of 3 Ulog within 48 hours for the two strains) compared to salinity and temperature (in darkness). Survival time of the strains was prolonged as they were maintained in darkness. Local strain (E. coli O55:B5) showed better survival capacity (T90 = 52 hours) than E. coli O126:B16 (T90 = 11 h). For both, modifications were noted only for some metabolic activities of carbohydrates hydrolysis. Cytotoxicity of the two strains, tested on Vero cell, was maintained during the period of survival.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.