Abstract
Disease caused by antibiotic-resistant Salmonella is a serious clinical problem that poses a great threat to public health. The present study is aimed at assessing differences in bacterial kinetics with different antibiotic resistance profiles under environmental stress and at developing microbial tolerance models in lettuce during storage from 4 to 36°C. The drug-resistance phenotypes of 10 Salmonella Typhimurium (S. Typhimurium) isolates were examined using the broth microdilution method. The results of 10 S. Typhimurium isolates in the suspensions showed that a slow trend towards reduction of drug-sensitive (DS) isolates in relation to the others though without statistical difference. Compared to DS S. Typhimurium SA62, greater bacterial reduction was observed in multidrug-resistant (MDR) S. Typhimurium HZC3 during lettuce storage at 4°C (P < 0.05). It was likely that a cross-response between antibiotic resistance and food-associated stress tolerance. The greater growth in lettuce at 12°C was observed for DS S. Typhimurium SA62 compared to MDR S. Typhimurium HZC3 and was even statistically different (P < 0.05), while no significant difference was observed for bacterial growth between MDR S. Typhimurium HZC3 and DS S. Typhimurium SA62 strains in lettuce storage from 16 to 36°C (P > 0.05). The goodness-of-fit indices indicated the Log-linear primary model provided a satisfactory fit to describe the MDR S. Typhimurium HZC3 and DS S. Typhimurium SA62 survival at 4°C. A square root secondary model could be used to describe the effect of temperature (12, 16, 28, and 36°C) on the growth rates of S. Typhimurium HZC3 (adj − R2 = 0.91, RMSE = 0.06) and S. Typhimurium SA62 (adj − R2 = 0.99, RMSE = 0.01) derived from the Huang primary model. It was necessary to pay attention to the tolerance of antibiotic resistant bacteria under environmental stress, and the generated models could provide parts of the input data for microbial risk assessment of Salmonella with different antibiotic resistance profile in lettuce.
Highlights
Salmonella is a zoonotic bacterium and is among the most important pathogens causing bacterial foodborne diseases
The results showed that the ranges of reductions in DS, DR, and MDR Salmonella strains after storage at 4°C for 96 h were 0.02-0.07, 0.03-0.16, and 0.02-0.30 log CFU/mL, respectively (Figure 1(a))
There was a rapid trend towards reduction of MDR isolates to cold stress in broth, and significant greater bacterial reductions were observed for MDR S
Summary
Salmonella is a zoonotic bacterium and is among the most important pathogens causing bacterial foodborne diseases. About 70-80% of foodborne disease outbreaks are caused by Salmonella in China [1]. Salmonella contamination occurs during both production and preparation phases by exposure to contaminated water, soil, insect, or animal fecal matter and through cross-contamination [3]. Consumers have been known to prepare ready-to-eat salad fruits and vegetables with utensils previously used to prepare raw chicken for cooking. This has led to cross-contamination, growth, and exposure to and illness from Salmonella of chicken origin [5]. A systematic review of Salmonella contamination of lettuce indicated that
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
