The Prevalence and Antibiotic-Resistant of Listeria monocytogenes in Livestock and Poultry Meat in China and the EU from 2001 to 2022: A Systematic Review and Meta-Analysis.

To compare the prevalence and antibiotic resistance rate of Listeria monocytogenes in livestock and poultry (beef, pork and chicken) meat between China and the European Union (EU), a meta-analysis was conducted. Ninety-one out of 2156 articles in Chinese and English published between January 2001 and February 2022 were selected from four databases. The prevalence of L. monocytogenes in livestock and poultry (beef, pork and chicken) meat in China and Europe was 7.1% (3152/56,511, 95% CI: 5.8-8.6%) and 8.3% (2264/889,309, 95% CI: 5.9-11.0%), respectively. Moreover, a decreasing trend was observed in both regions over time. Regarding antibiotic resistance, for the resistance to 15 antibiotics, the pooled prevalence was 5.8% (95% CI: 3.1-9.1%). In both regions, the highest prevalence was found in oxacillin, ceftriaxone and tetracycline, and a large difference was reported between China and the EU in ceftriaxone (52.6% vs. 17.3%) and cefotaxime (7.0% vs. 0.0%). Based on the above, it remains a significant challenge to enforce good control measures against the meat-sourced L. monocytogenes both in China and in the EU.

The magnitude of heterogeneity in individual-cell growth dynamics is an inherent characteristic of Salmonella enterica ser. Typhimurium strains.

Individual-cell heterogeneity is a major source of variability in biological systems affecting importantly, among others, microbial behavior. Characterization of cell populations of pathogenic bacterial strains in their entirety, ignoring the phenotypic variability of single cells, may result in erroneous safety risk estimates. The objective of the present study was the evaluation and comparison of the heterogeneity in the individual-cell growth dynamics of different strains of Salmonella enterica. The stochasticity in the growth of single cells of five S. enterica ser. Typhimurium strains was quantitatively described using time-lapse microscopy, and the existence of a strain effect was statistically assessed. In total, 831 growing microcolonies originating from single cells were monitored and analyzed, and the growth kinetic parameters of lag time (λ) and maximum specific growth rate (µmax) for each one of them were estimated. An extensive heterogeneity in individual-cell growth kinetics was recorded, while significant inter-strain differences in their heterogeneity were evident based on simultaneous Bonferroni confidence intervals and Levene's tests. The Logistic and LogLogistic probability distribution provided the best fitting for µmax and λ data, respectively for all the tested strains. The strain effect on the above distributions was also demonstrated with pairwise comparisons of the decile differences. The impact of strain-dependent heterogeneity on microbial growth was visualized by comparing stochastic growth curves of different strains using Monte Carlo simulation. In conclusion, the individual-cell growth dynamics of S. enterica are heterogeneous, with the magnitude of the observed heterogeneity appearing to be an inherent characteristic of bacterial strains.

The Prevalence and Epidemiology of Salmonella in Retail Raw Poultry Meat in China: A Systematic Review and Meta-Analysis.

Foodborne disease caused by Salmonella is an important public health concern worldwide. Animal-based food, especially poultry meat, is the main source of human salmonellosis. The objective of this study was to evaluate the prevalence and epidemiology of Salmonella contamination in raw poultry meat commercialized in China. Following the principle of systematic review, 98 sets of prevalence data were extracted from 74 publications conducted in 21 Chinese provincial regions. The random-effect model was constructed for subgrouping analysis by meat category, preservation type, and geographical location. The prevalence levels differed from high to low among raw poultry meat, including chicken, 26.4% (95% CI: 22.4-30.8%); pigeon, 22.6% (95% CI: 18.2-27.8%); duck, 10.1% (95% CI: 5.3-18.2%); and other poultry meat, 15.4% (95% CI: 12.0-19.5%). Prevalence data on the preservation type revealed that chilled poultry meat might be more likely to experience cross-contamination than non-chilled poultry meat in China. The distribution map of Salmonella for raw poultry meat showed that a higher prevalence level was found in the Shaanxi, Henan, Sichuan, and Beijing regions. All subgroups possessed high amounts of heterogeneity (I2 > 75%). The scientific data regarding the differences in prevalence levels between meat category, preservation method, and geographical region sources might be useful to improve specific interventions to effectively control the incidence of Salmonella in poultry meat.

Dynamic modelling of Legionella pneumophila thermal inactivation in water.

A predictive mathematical model describing the effect of temperature on the inactivation of Legionella pneumophila in water was developed. Thermal inactivation of L. pneumophila was monitored under isothermal conditions (51 - 61°C). A primary log-linear model was fitted to the inactivation data and the estimated D values ranged from 0.23 to 25.31 min for water temperatures from 61 to 51°C, respectively. The effect of temperature on L. pneumophila inactivation was described using a secondary model, and the model parameters z value and Dref (D-value at 55°C) were estimated at 5.54°C and 3.47 min, respectively. The developed model was further validated under dynamic temperature conditions mimicking various conditions of water thermal disinfection in plumbing systems. The results indicated that the model can satisfactorily predict thermal inactivation of the pathogen at dynamic temperature environments and effectively translate water temperature profiles to cell number reduction. The application of the model in combination with effective temperature monitoring could provide the basis of an integrated preventive approach for the effective control of L. pneumophila in plumbing systems.

Effect of chlorine stress on the subsequent growth behavior of individual Salmonella cells.

The present work investigates the effect of chlorine stress on the subsequent growth behavior of individual Salmonella cells. A time-lapse microscopy method was used which allowed to evaluate the effect of chlorine on the division times of Salmonella individual cells and the percentage of cells able to divide after the treatment. The results showed that the percentage of cells able to divide after the chlorine treatment decreased from 92.7% for untreated cells to 43.12% and 22% for cell exposed to 127 and 150 mg/l chlorine for 3 min, respectively. The first division time of Salmonella cells was not affected by the chlorine stress at the lower tested concentration of 11 mg/l. Exposure at higher chlorine concentrations however, resulted in significantly longer and more variable division times. The mean first division times were 1.46 ±â€¯0.61, 1.41 ±â€¯0.53, 1.69 ±â€¯0.59, 5.34 ±â€¯4.03 and 19.2 ±â€¯8.71 h after 3 min treatments with 0, 11, 61, 127 and 150 mg/l chlorine, respectively. The effect of chlorine on the second division time of the cells was milder compared to the first division. Exposure of cells to chlorine concentrations up to 61 mg/l did not affect the second division. These results indicate that the daughter cells have no "memory" of the chlorine treatment at these concentrations. For cells exposed to the highest tested chlorine concentration of 150 mg/l the mean second division time was almost 3.5 times longer compared to untreated cells indicating that potential damages of the cells caused by the chlorine treatment are not fully repaired in the second generation. The quantitative data provided by this study at the level of individual cell may lead to a better understanding of microbial resistance to chlorine and improve sanitation and decontamination procedures in the food industry.

Heterogeneity of single cell inactivation: Assessment of the individual cell time to death and implications in population behavior.

A direct microscopic time-lapse method, using appropriate staining for cell viability in a confocal scanning laser microscope, was used for the direct assessment of Salmonella Agona individual cell inactivation in small two-dimensional colonies exposed to osmotic stress. Individual cell inactivation times were fitted to a variety of continuous distributions using @Risk software. The best fitted distribution (LogLogistic) was further used to predict the inactivation of Salmonella populations of various initial levels using Monte Carlo simulation. The simulation results showed that the variability in inactivation kinetics is negligible for concentrations down to 100 cells and the population behavior can be described with a deterministic model. As the concentration decreases below 100 cells, however, the variability increases significantly indicating that the traditional D-value used in deterministic first order kinetic models is not valid. At a second stage, single cell behavior was monitored in larger three dimensional colonies. The results showed that colony size can affect the inactivation pattern. The effect of colony size on microbial inactivation was confirmed with validation experiments which showed a higher inactivation rate for populations consisting of single cells or small colonies compared to those consisting of cells organized in larger colonies.