Survivability of Pathogens under Different Growth Conditions in Seawater

Abstract

There is need to assess the effects of variability in temperature as well as salinity on the fate of pathogens in marine foods and environments due to the links between climate change and disease epidemiology. Here, the survivability of four pathogenic bacteria (Escherichia coli O157:H7, E. coli ST2747, Salmonella sp., and Salmonella enterica subsp. Enterica Typhimurium) under various temperature regimes (4, 10, 25 and 50^oC in natural and artificial seawaters for 10 days) and salt concentrations (0.5×, 1× and 2× for 14 days) was evaluated. Antibiotic susceptibility profiling of the bacteria was also carried out using disk diffusion method. In general, temperature affected survival of the pathogens in both natural and artificial seawaters. Growth was mostly lowest at 4^oC, but not significantly different from that at 10^oC, for all organisms. However, significantly higher bacterial growth was observed, particularly in the first 5 days, at 25 and 50^oC, for most of the organisms. Survival of all organisms in natural seawater was higher at 50 than at 25^oC in the later stage of incubation, indicating greater bacterial persistence at higher temperature. In comparison, persistence of all organisms, except E. coli ST2747, was lowest in the 0.5× than in both 1× and 2× salt concentrations, though not significant (P>0.05). All organisms demonstrated high sensitivity to ofloxacin but showed varied multiple resistance to cefuroxime, ampicillin, nitrofurantoin and amoxicillin/clavulanate. These findings imply that in the future, if negative impacts of climate change are not mitigated, pathogenic organisms which pose serious health risks persist longer in seawater environments.