Models of microbial cross-contamination dynamics

Surface inoculation method impacts microbial reduction and transfer of Salmonella Enteritidis PT 30 and potential surrogates during dry sanitation

Dry sanitation methods are often limited to physical removal strategies such as brushing or wiping with sanitary cleaning tools. However, the relative efficacy of these approaches to remove microbiota on surfaces, and the risk of transferring cells to other surfaces via the cleaning tool, is unclear. The effect of dry wiping with a single-use towel on the removal of four different bacteria (Salmonella Enteritidis, Enterococcus faecium, Listeria innocua, Escherichia coli) was investigated. We also quantified the number of cells transferred to the towel itself during dry cleaning. Three different surface inoculation methods (spot, glass bead, contaminated milk powder) were assessed and significantly impacted initial surface microbial load. Higher initial counts corresponded to lower transfer coefficients (e.g., proportion of transferred cells). The effect of bacterial identity was significant on reduction after dry wiping for all three inoculation methods. Moreover, both bacterial identity and inoculation method had significant effects on the number of cells transferred to the towel. In most scenarios, dry wiping resulted in a reduction <1.0 log CFU/coupon. Although, on surfaces inoculated via contaminated milk powder, reductions of up to 1.6 ± 0.3 log CFU/coupon were obtained. Overall, E. faecium transferred more readily to the towel. These results may help guide experimental design for future research on dry sanitation.

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.

Quantitative risk assessment of salmonellosis in Cambodian consumers through chicken and pork salad consumption

Salmonella is a globally important foodborne bacterial pathogen that poses a high risk to human health. This study aimed to estimate the risk to Cambodian consumers from acquiring salmonellosis after consuming chicken and pork salad, using a quantitative microbial risk assessment (QMRA). Chicken and pork salads are typical Cambodian dishes containing raw vegetables and boiled chicken meat or pork. As previously described, chicken meat and pork samples (n = 204 of each) were collected from traditional markets in 25 Cambodian provinces to generate data on Salmonella contamination. Salad preparation and consumption practices were surveyed in 93 Cambodian households and this information was used to design an experiment to assess Salmonella cross-contamination from raw meat to ready-to-eat salad. In the part of the study reported here, data on consumption, Salmonella in salad, dose-response, and predicted salmonellosis were modeled using Monte Carlo simulations at 10,000 iterations. The prevalence of Salmonella in chicken meat and pork were set to 42.6 and 45.1%, respectively, with average most probable number (MPN) per gram of Salmonella in chicken meat was 10.6 and in pork 11.1 MPN/g, based on an earlier study. Half of the interviewed households cooked meat for the salad directly after purchase. The QMRA model showed that the modeled annual risk of salmonellosis from consuming chicken salad, pork salad and both chicken and pork salad were 11.1% probability of illness per person per year (90% CI 0.0–35.1), 4.0% (90% CI 0.0–21.3), and 14.5% (90% CI 0.0–33.5), respectively. The factors most influencing the estimate were cross-contamination while preparing the salad, followed by the prevalence of Salmonella in chicken meat and pork at the market. The wide confidence interval for the incidence was mainly due to the variability in reducing bacteria concentration by cooking and salad consumption. The predicted risk of salmonellosis due to chicken and pork salad consumption is high, and the study provides evidence supporting control measures of improving the safety of retailed chicken and pork obtained from markets to households and improving food preparation methods in the household.

The prevalence of Listeria monocytogenes in meat products in Brazil: A systematic literature review and meta-analysis

Listeria monocytogenes, a foodborne pathogen that causes human listeriosis, is commonly found in meat products. This study aimed to estimate the prevalence of L. monocytogenes in a variety of Brazilian meat products, using a meta-analysis of data from the literature. A total of 29 publications from five databases, published between January 1, 2009, and December 31, 2019, were included in the study. Estimated by the random-effects model, the combined prevalence of L. monocytogenes was 13%, ranging from 0 to 59%. The combined prevalence of L. monocytogenes was 14% and 11% for raw meat and ready-to-eat (RTE) meat, respectively. The prevalence of L. monocytogenes was higher in the swine species' meat products and the Southeast region of Brazil. Regarding the type of establishment, it was the retail market that presented the highest combined prevalence rate (19%). The most prevalent serotypes of L. monocytogenes were 4b, 1/2a, 1/2b, and 1/2c. The knowledge of differences in the prevalence levels of L. monocytogenes in different meat products can guide in its efficient control by the competent authorities and by industry.

Distribution, virulence, genotypic characteristics and antibiotic resistance of Listeria monocytogenes isolated over one-year monitoring from two pig slaughterhouses and processing plants and their fresh hams

Listeria monocytogenes contamination in raw pork and ready to eat foods is an important food safety concern, also for the increasing detection of antimicrobial-resistant isolates. Data on L. monocytogenes occurrence, persistence, distribution and genetic characterization in two different plants, namely in continuum from slaughtered pigs, environment and unfinished products (fresh hams) were observed by one-year monitoring and were integrated with their antimicrobial resistance patterns. A total of 98 samples out of the overall 1131 (8.7%) were positive for L. monocytogenes, respectively 2.6% and 13.2% in plants A and B: only three serotypes were identified, 1/2c (50%), 1/2b (36.7%) and 1/2a (13.27%), and strains were classified in 35 pulsotypes and 16 clusters by PFGE; a unique P-type was highlighted according to the detection of virulence genes. The contamination flow of L. monocytogenes has a low occurrence in slaughterhouse (Plant A = 1.1%, Plant B: 3.1%; p > 0.05) and increased throughout the processing chain with trimming area as the most contaminated (Plant A: 25%, Plant B: 57%; (p < 0.05)), both in the environment and in unfinished products (80% in hams before trimming in plant B). The dominant role of environmental contamination in post-slaughter processing is confirmed to be a significant cause of meat contamination by L. monocytogenes. Very high levels of resistance were observed for clindamycin (57%) and high resistance levels (>20-50%) to ciprofloxacin, oxacillin, levofloxacin and daptomycin, confirming the L. monocytogenes resistance trend to a wide range of antimicrobial agents. A total of 11 L. monocytogenes isolates were multidrug resistant and 7 out of them were isolated from slaughtered pigs. An interesting significant (p < 0.05) statistical correlation has been found between resistance to some antimicrobial agents and lineage/serotypes. Microbiological sampling of food and environments after sanitization are commonly used as verification procedure for the absence of L. monocytogenes in food plants and to give assurance of food safety, but strains characterization is necessary for industries to target specific control measures, like the enforcement of the hygiene program and of the control of operator activities, at least for permanent strains. The only presence of L. monocytogenes could not be considered as the conclusive assessment of a potential risk for public health, also in terms of emerging and emerged antimicrobial resistances.

Probabilistic model for the estimation of the consumer exposure to methicillin-resistant Staphylococcus aureus due to cross-contamination and recontamination

The presence of multidrug-resistant bacteria like methicillin-resistant Staphylococcus aureus (MRSA) in retail meat is one of the current concerns of the public health authorities. Bacterial cross-contamination and recontamination during household food preparation could play an important role in the dissemination of such bacteria, and therefore could contribute to a serious health problem, more specifically for immunocompromised people. In order to evaluate the importance of such events, a probabilistic model was developed to estimate the likelihood and extent of cross-contamination and recontamination and the burden of MRSA from contaminated raw chicken meat via hands and kitchen utensils in a serving (consisting on a slice of bread and a piece of grilled chicken meat) during a household barbecue in Germany. A modular design was used, taking into account the chronological order of the routines during the barbecue event, and Monte Carlo simulations were applied. Available data on the prevalence and burden of MRSA in chicken meat at retail in Germany were used as starting point and were incorporated in the model as probability distributions. The probabilities and extent of bacterial transfer between food items and kitchen utensils (referred to as "Objects") and the routines performed during food preparation (referred to as "Actions") specified by their probabilities of occurrence were incorporated as the main input parameters. The model was set up in R 3.5.0 and converted to a standardized format (FSKX file). Therefore, the code can be easily accessed, evaluated, modified, and reused for different purposes. The present study contributes to the quantification of consumer exposure to MRSA through food consumption once contaminated food has entered the household kitchen. Even when the MRSA prevalence and bacterial load in retail chicken meat in Germany are low, resistant bacteria can reach the consumer due to cross-contamination and recontamination events. The results show that the probability of one CFU to be transferred from the contaminated raw chicken meat to the final serving and the number of MRSA bacteria transferred due to cross-contamination and recontamination events are in general low, being the contamination of the final serving more likely to occur via bread, rather than via grilled chicken. The results show that the prevalence of MRSA at retail highly influences the probability of the final serving to be contaminated. However, this study also highlights the importance of keeping good hygiene practices during the household food manipulation for reducing the spread of MRSA. The provision of the model in a standardized data format will allow an easy incorporation of the developed model into a complete quantitative microbial risk assessment model that will greatly help to estimate the risk of consumer exposure to MRSA through the consumption of contaminated food.

The prevalence of Listeria monocytogenes in meat products in China: A systematic literature review and novel meta-analysis approach

Meat products are commonly regarded as one of the main sources of human listeriosis caused by Listeria monocytogenes. The objective of this study was to estimate the prevalence of L. monocytogenes in a range of meat products from 24 different Chinese regions by using meta-analysis of literature data and a novel sensitivity analysis approach. A total of 112 publications from five databases, published between 1 January 2007 and 31 December 2017, were systematically selected for relevance and covered meat products sampled between 2000 and 2016. Estimated by the random-effects model, the pooled prevalence of L. monocytogenes was 8.5% (95% CI: 7.1%-10.3%) in raw meats and 3.2% (95% CI: 2.7%-3.9%) in ready-to-eat (RTE) meats. The prevalence differed from high to low among raw meats including prefabricated raw meats 12.6% (95% CI: 6.9%-21.7%), fresh pork 11.4% (95% CI: 8.6%-14.9%), fresh beef 9.1% (95% CI: 6.3%-13.0%), fresh poultry 7.2% (95% CI:4.9%-10.4%), frozen raw meats 7.2% (95% CI: 5.7%-9.0%), and fresh mutton 5.4% (95% CI: 2.5%-11.0%). A higher L. monocytogenes prevalence level was shown in the meat products from central and northeastern China provincial regions. The entropy-based sensitivity analysis utilized in the meta-analysis indicated that the sampling period and location were two critical factors influencing the prevalence level of L. monocytogenes in meat products. A better understanding of differences in prevalence levels per geographic region and between meat product sources may allow the competent authorities, industry, and other relevant stakeholders to tailor their interventions to control the occurrence of L. monocytogenes in meat products effectively.

Occurrence of Foodborne Agents at Food Service Facilities in the Czech Republic

HIGHLIGHTS

Contamination of food service facilities in the Czech Republic by foodborne agents was determined. Bacillus cereus, Staphylococcus aureus, and Escherichia coli were detected in almost 50% of samples. The occurrence of B. cereus, S. aureus, and E. coli depended on the season of the year. Regular monitoring of food service facilities for agents of foodborne disease is necessary.