Thermal inactivation of Salmonella Enteritidis on chicken skin previously exposed to acidified Sodium chlorite or tri-sodium phosphate

Modeling Salmonella spp. inactivation in chicken meat subjected to isothermal and non-isothermal temperature profiles

Salmonella genus has foodborne pathogen species commonly involved in many outbreaks related to the consumption of chicken meat. Many studies have aimed to model bacterial inactivation as a function of the temperature. Due to the large heterogeneity of the results, a unified description of Salmonella spp. inactivation behavior is hard to establish. In the current study, by evaluating the root mean square errors, mean absolute deviation, and Akaike and Bayesian information criteria, the double Weibull model was considered the most accurate primary model to fit 61 datasets of Salmonella inactivation in chicken meat. Results can be interpreted as if the bacterial population is divided into two subpopulations consisting of one more resistant (2.3% of the total population) and one more sensitive to thermal stress (97.7% of the total population). The thermal sensitivity of the bacteria depends on the fat content of the chicken meat. From an adapted version of the Bigelow secondary model including both temperature and fat content, 90% of the Salmonella population can be inactivated after heating at 60 °C of chicken breast, thigh muscles, wings, and skin during approximately 2.5, 5.0, 9.5, and 57.4 min, respectively. The resulting model was applied to four different non-isothermal temperature profiles regarding Salmonella growth in chicken meat. Model performance for the non-isothermal profiles was evaluated by the acceptable prediction zone concept. Results showed that >80% of the predictions fell in the acceptable prediction zone when the temperature changes smoothly at temperature rates lower than 20 °C/min. Results obtained can be used in risk assessment models regarding contamination with Salmonella spp. in chicken parts with different fat contents.

Effect of some chemical decontaminants on the survival of Listeria monocytogenes and Salmonella Typhimurium with different attachment times on chicken drumstick and breast meat

The aim of this study was to investigate the efficacy of some decontaminant agents on the survival of Salmonella Typhimurium and Listeria monocytogenes with different attachment periods to chicken drumstick with skin and skinless breast meat. For this purpose, S. Typhimurium and L. monocytogenes were given periods of 0.5 (30 s), 20 and 210 min to attach to the chicken drumstick and breast meat. At the end of the each attachment period, the meat samples were treated with lactic acid, (2 and 4%), cetylpyridinium chloride (0.5%) and acidified sodium chlorite (1200 ppm). In the drumstick sample treated with cetylpyridinium chloride, the reduction level of L. monocytogenes with 30 s attachment period was 3.2 log10 CFU/ml while the reduction level was found to be 2.2 log10 CFU/ml with 20 min attachment period. Decontamination with acidified sodium chlorite resulted in reduction of 1.8 log10 CFU/ml in S. Typhimurium attached to the chicken drumstick for 30 s while the reduction levels of S. Typhimurium with 20 and 210 min attachment periods were 1.2 and 1.3 log10 CFU/ml, respectively. The results indicated that some antimicrobial agents have more strong effect on L. monocytogenes and S. Typhimurium on the chicken meat parts in the first 30 s of attachment. However, there were no changes in the efficacy of the decontaminants on the survival of L. monocytogenes and S. Typhimurium on chicken meat when the attachment time of these bacteria were extended from 20 min to 210 min.

Organ-on-a-chip for assessing environmental toxicants

Man-made xenobiotics, whose potential toxicological effects are not fully understood, are oversaturating the already-contaminated environment. Due to the rate of toxicant accumulation, unmanaged disposal, and unknown adverse effects to the environment and the human population, there is a crucial need to screen for environmental toxicants. Animal models and in vitro models are ineffective models in predicting in vivo responses due to inter-species difference and/or lack of physiologically-relevant 3D tissue environment. Such conventional screening assays possess limitations that prevent dynamic understanding of toxicants and their metabolites produced in the human body. Organ-on-a-chip systems can recapitulate in vivo like environment and subsequently in vivo like responses generating a realistic mock-up of human organs of interest, which can potentially provide human physiology-relevant models for studying environmental toxicology. Feasibility, tunability, and low-maintenance features of organ-on-chips can also make possible to construct an interconnected network of multiple-organs-on-chip toward a realistic human-on-a-chip system. Such interconnected organ-on-a-chip network can be efficiently utilized for toxicological studies by enabling the study of metabolism, collective response, and fate of toxicants through its journey in the human body. Further advancements can address the challenges of this technology, which potentiates high predictive power for environmental toxicology studies.

Sodium chlorite increases production of reactive oxygen species that impair the antioxidant system and cause morphological changes in human erythrocytes

Sodium chlorite (NaClO₂ ) is used in the production of chlorine dioxide for bleaching and stripping of textiles, pulp, and paper. It is also used as disinfectant in municipal water treatment and as a component in therapeutic rinses and gels. The effect of NaClO₂ on human erythrocytes has been studied under in vitro conditions. Incubation of 5% suspension of erythrocytes with NaClO₂ (0.1-2.0 mM) at 37°C for 30 min resulted in marked cell lysis (1.2-3.8 fold) and increased their osmotic fragility. Several parameters were assayed in cell lysates prepared from NaClO₂ -treated and -untreated (control) erythrocytes. Compared to controls, exposure to NaClO₂ caused significant increase in protein oxidation (1.1-8.07 fold), lipid peroxidation (1.08-4.95 fold) with decrease in total sulfhydryl (-5 to -61%), and glutathione levels (-7 to -86%). Methemoglobin content was tremendously increased, by 5-52 fold when compared to control, while methemoglobin reductase activity decreased (-17 to -93%) upon NaClO₂ treatment. NaClO₂ enhanced the generation of reactive oxygen species by 3-21 fold and lowered the metal reducing and free radical quenching ability of erythrocytes. It also caused an increase in nitric oxide levels (2.7-15.4 fold) showing generation of nitrosative stress too. The activities of major antioxidant and membrane bound enzymes were significantly altered. Gross morphological changes, from discocytes to echinocytes, were seen in NaClO₂ -treated erythrocytes under electron microscope. These results show that NaClO₂ induces oxidative stress in human erythrocytes, damages the membrane, and impairs the cellular antioxidant defence system. This oxidative damage can shorten the life span of erythrocytes in blood resulting in red cell senescence. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1343-1353, 2017.