Modelling inactivation of wild‐type and clinicalEscherichia coliO26 strains using UV‐C and thermal treatment and subsequent persistence in simulated gastric fluid

Abstract

Aims: First, two inactivation models were compared for different phenotypic profiles of Escherichia coli O26 using ultraviolet-C light (UV-C) and thermal treatment (T), by means of Central Composite Rotatable Design of Experiment (CCRD). Second, we aimed to evaluate the subsequent survival and persistence of cells in simulated gastric fluid (SGF). Methods and Results: Two strains of E. coli O26, a wild-type strain and a clinical ATCC strain were used in both steps. A CCRD was used in a 2 2 arrangement in random order. The goodness-of-fit of the models was determined. The lack of fit, and the normality of residual data were checked with the Shapiro-Wilk test, and the model accuracy factor, bias factor and the model mean square error (MSE) were measured. Subsequently, the resistance capacity of the strains was evaluated after exposure to simulated gastric acid. The CCRD results obtained indicate that the mild heat (<70°C) has a recovery effect. In addition, for the clinical strain, the UV-C and heat (above 70°C) has an additive inactivation effect. Moreover, temperature (65°C) induced SGF resistance by the wild-type and clinical strain. For the clinical strain, cells exposed to UV-C were more sensitive to SGF. In contrast to clinical strain, exposing cells of the wild-type strain to UV-C increased the survival capacity in the SGF. Conclusion: Response surface analyses showed that the wild-type O26 strain has higher persistence under unfavourable conditions than the clinical strain, and the stresses caused by applied microbial control technologies can increase the survival capacity in the SGF. Significance and Impact of the Study: The present study shed light on different phenotypic responses in the same bacterium serogroup. Moreover, the impact of the study was that strain selection criteria must be adequate to develop effective models of inactivation.

Inactivation of Multi-Drug Resistant Non-Typhoidal Salmonella and Wild-Type Escherichia coli STEC Using Organic Acids: A Potential Alternative to the Food Industry

“…Our hypothesis for the inactivation tail is based on the saturation of efficacy of the sodium hypochlorite due to the lower availability of free-chlorine or volatilization of this compound. Furthermore, the wild genetic profiles can have an influence because metabolic transcriptions are generally more active [ 3 ].…”

“…The wild-type strains showed higher resistance to organic acids when compared to the ATCC strains, and E. coli was more resistant than Salmonella in lactic and acetic acids ( Figure 1 ). A hypothesis is related to the mechanism of the acid tolerance response (ATR) that remains more active in wild strains subjected to abiotic stresses than in clinical strains stored for long periods [ 3 ]. The extensive presence of bacteria resistant to several drugs has been related to Brazilian meat and poultry production [ 5 , 50 , 51 ].…”

“…Salmonella and Escherichia coli present in food are a direct risk to human health [ 1 , 2 , 3 ]. Studies related to food contamination by these pathogens are frequent in the literature [ 4 , 5 ].…”

“…The pathogenesis of E. coli STEC relates to its capacity of causing hemolytic uremic syndrome (HUS) and bloody diarrhea, while non-typhoidal Salmonella can cause gastroenteritis (inflammatory condition of the gastrointestinal tract), vomiting, and non-bloody diarrhea [ 4 , 10 ]. For this reason, studies have been made in recent years to inactivate these bacteria at all stages of production [ 3 , 11 , 12 , 13 ].…”

Modeling Salmonella Typhimurium Inactivation in Dry-Fermented Sausages: Previous Habituation in the Food Matrix Undermines UV-C Decontamination Efficacy

“…However, this is not a drawback for the decontamination of sliced readyto-eat products, since post-processing contamination occurs mostly at the product surface, during handling, slicing, and packing, and UV-C may be applied on both sides of the slices to guarantee efficient sanitization (Ganan et al, 2013). Recently, several food matrix characteristics that may impact the efficacy of UV-C microorganism inactivation have been emphasized (Gayán et al, 2011;Geveke et al, 2011;Canto et al, 2018;Monteiro et al, 2018;Castro et al, 2019). However, matrix habituation effects exerted on foodborne pathogens is a novel aspect which has not yet been adequately addressed.…”