INFLUENCE OF MARINE WATER CONDITIONS ON SALMONELLA ENTERICA SEROVAR TYPHIMURIUM SURVIVAL

Abstract

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.

The Effect of Previous Life Cycle Phase on the Growth Kinetics, Morphology, and Antibiotic Resistance of Salmonella Typhimurium DT104 in Brain Heart Infusion and Ground Chicken Extract

“…DT104 in the EDP phase may have exhibited less resistance to antibiotics due to the loss of plasmids after prolong incubation time and depletion of nutrients. Various studies have reported a modification of the plasmid pattern after long periods of incubation in marine water (Mejri et al., 2012). It is possible that as the cultures continue to grow in the media the oxygen and nutrients become progressively more limited resulting in rendering the EDP cells more sensitive to antibiotics compared to early cells.…”

What’s the risk? Identifying potential human pathogens within grey-headed flying foxes faeces

“…However, unlike Haemophilus spp., Salmonella spp. represent a much greater risk to public health, as extended survival in environmental settings, including estuaries such as the Yarra River, has been previously documented [ 66 ] [ 67 , 68 ]. Thus, the risk of infection includes not only those who contact bat faeces directly, but also those who engage in recreational use of the affected waterway.…”

The Effect of Previous Life Cycle Phase on the Growth Kinetics, Morphology and Antibiotic Resistance ofSalmonellaTyphimurium DT104 in Brain Heart Infusion and Ground Chicken Extract

“…DT104 in the EDP phase may have exhibited less resistance to antibiotics due to the loss of plasmids after prolong incubation time and depletion of nutrients. Various studies have reported a modification of the plasmid pattern after long periods of incubation in marine water (46). It is possible that as the cultures continue to grow in the media the oxygen and nutrients become progressively more limited resulting in rendering the EDP cells more sensitive to antibiotics compared to early cells.…”