The microbiological safety of ready-to-eat specialty meats from markets and specialty food shops: a UK wide study with a focus on Salmonella and Listeria monocytogenes

High pressure processing at the early stages of ripening enhances the safety and quality of dry fermented sausages elaborated with or without starter culture

To study the quality of chorizo de León dry fermented sausages (DFS), high pressure processing (HPP) applied at the early stages of ripening and the use of a functional starter culture were evaluated as additional safety measures. Furthermore, the ability to control the populations of artificially inoculated Listeria monocytogenes and Salmonella Typhimurium was investigated and the evolution of microbial communities was assessed by amplicon 16S rRNA metataxonomics. The use of HPP and the starter culture, independently or combined, induced a reduction of Listeria monocytogenes of 1.5, 4.3 and > 4.8 log CFU/g respectively, as compared to control. Salmonella Typhimurium counts were under the detection limit (<1 log) in all treated end-product samples. Both additional measures reduced the activity of undesirable microbiota, such as Serratia and Brochothrix, during the production of DFS. Moreover, the starter culture highly influencedthe taxonomic profile of samples.No adverse sensory effects were observed, and panelists showed preference for HPP treated DFS. In conclusion, this new approach of applying HPP at the early stages of ripening of DFS in combination with the use of a defined starter culture improved the safety and quality of the meat product.

Prevalence of Listeria monocytogenes and Salmonella spp. in Different Ready to Eat Foods from Large Retailers and Canteens over a 2-Year Period in Northern Italy

This study aims to give an overview of the prevalence of Listeria monocytogenes and Salmonella spp. in 9727 samples (2996 for L. monocytogenes and 6731 for Salmonella spp.) from different categories of ready-to-eat (RTE) foods, collected over 2 years from 28 large retailers and 148 canteens in the regions of northern Italy. The RTE samples were classified into two groups according to the preparation methods: (i) multi-ingredient preparations consisting of fully cooked food ready for immediate consumption, or with minimal further handling before consumption (Group A), and (ii) multi-ingredient preparations consisting of cooked and uncooked food, or preparations consisting of only raw ingredients (Group B). L. monocytogenes and Salmonella spp. were investigated in both of these categories. The overall prevalence of L. monocytogenes and Salmonella spp. was 0.13% and 0.07%, respectively. More specifically, L. monocytogenes was found in 0.04% of 2442 analysed RTE food samples belonging to group A and in 0.54% of 554 samples belonging to group B. Furthermore, 0.03% of 5367 RTE food samples from group A and 0.21% of 1364 samples from group B tested positive for Salmonella spp. In conclusion, the results obtained in this study can provide a significant contribution to L. monocytogenes and Salmonella spp. risk analysis in RTE foods.

Behavior of Listeria monocytogenes and Other Microorganisms in Sliced Riojano Chorizo (Spanish Dry-Cured Sausage) during Storage under Modified Atmospheres

Sliced ready-to-eat meat products packaged under modified atmospheres are often marketed since they cover consumer demands. The slicing process could be a potential risk for consumers since contamination with Listeria monocytogenes could occur during this stage. The current study evaluated the behavior of L. monocytogenes and other microorganisms in commercial sliced Riojano chorizo. This meat product was sliced and inoculated with L. monocytogenes (3.5 log CFU/g) before packaging under different atmospheres (air, vacuum, 100% N2, 20% CO2/80% N2 and 40% CO2/60% N2) and stored at 4 °C for up to 60 days. Samples were taken on days 0, 7, 21, 28 and 60 of storage. L. monocytogenes, mesophiles, Enterobacteriaceae, lactic acid bacteria, Micrococcaceae, molds and yeast counts were evaluated. Additionally, water activity, humidity and pH were determined. L. monocytogenes counts decreased in inoculated sliced chorizo during storage. Packaging conditions and day of storage influenced microbial counts. After 60 days, a significant reduction (p ≤ 0.05) in the initial Listeria contamination levels (3.5. log CFU/g) between 1.1 and 1.46 logarithmic units was achieved in the sausages packaged in modified atmosphere. The highest reductions were observed in slices packaged in 40% CO2/60% N2 after 60 days of storage at 4 °C.

Assessment of Hygienic Practices in Beef Cattle Slaughterhouses and Retail Shops in Bishoftu, Ethiopia: Implications for Public Health

Understanding the potential drivers of microbial meat contamination along the entire meat supply chain is needed to identify targets for interventions to reduce the number of meatborne bacterial outbreaks. We assessed the hygienic practices in cattle slaughterhouses (28 employees) and retail shops (127 employees) through face-to-face interviews and direct personal observations. At the slaughterhouses, stunning, de-hiding and evisceration in vertical position, carcass washing and separate storage of offal were the identified good practices. Lack of hot water baths, absence of a chilling room, infrequent hand washing, insufficiently trained staff and irregular medical check-up were practices that lead to unhygienic handling of carcasses. At the retail shops, cleaning equipment using soap and hot water (81%), storing unsold meat in refrigerators (92%), concrete floors and white painted walls and ceilings were good practices. Adjacently displaying offal and meat (39%), lack of a cold chain, wrapping meat with plastic bags and newspapers, using a plastic or wooden cutting board (57%), infrequent washing of equipment and floors, and inadequately trained employees were practices that could result in unhygienic handling of beef. Our study identified unhygienic practices both at the slaughterhouses and retail shops that can predispose the public to meatborne infections, which could be improved through training and implementation of quality control systems.

Mapping the dominant microbial species diversity at expiration date of raw meat and processed meats from equine origin, an underexplored meat ecosystem, in the Belgian retail

Although equine meats and their derived smoked or fermented products are popular in some regions of the world, they only form a minor fraction of the global meat consumption. The latter may explain why their associated bacterial communities have not received much attention. In the present study, 69 different samples of equine meats and meat products were investigated. The samples consisted of raw meat from horses (17 samples) and zebra (7), as well as non-fermented but smoked (24) and fermented (21) horse meat products. After purchase, all samples were stored at 4 °C and analysed at expiration date. Besides an estimation of the total microbial counts, specific attention was paid to the identification of lactic acid bacteria (LAB) and catalase-positive cocci, in particular the group of coagulase-negative staphylococci (CNS), involved, due to their technological relevance in view of the elaboration of meat products. Samples that were loosely wrapped in butcher paper instead of vacuum- or modified-atmosphere packages were also screened for pseudomonads and enterobacterial species. In total, 1567 bacterial isolates were collected, subjected to (GTG)₅-PCR fingerprinting of genomic DNA, and identified by multiple gene sequencing (based on the 16S rRNA, pheS, rpoA, rpoB, and/or tuf genes). Overall, the bacterial species diversity consisted mostly of LAB but was contingent on the type of product. Raw meat was dominated by Carnobacterium divergens, Lactobacillus sakei, Lactococcus piscium, and Leuconostoc gelidum, with zebra meat being particularly rich in lactococci. Smoked and fermented horse meat products contained mostly Lb. sakei and, to a lesser degree, Lactobacillus curvatus. In addition, several catalase-positive cocci (mostly Staphylococcus equorum), Anoxybacillus sp., Brevibacterium sp., Brochothrix thermosphacta, and the enterobacterial species Hafnia alvei were found.

Antimicrobial resistance and genetic diversity in ceftazidime non-susceptible bacterial pathogens from ready-to-eat street foods in three Taiwanese cities

Bacterial contamination of ready-to-eat (RTE) street foods is a major concern worldwide. Dissemination of antibiotic resistant pathogens from food is an emerging public-health threat. To investigate the prevalence of antibiotic resistance genes and ceftazidime resistance-associated efflux pumps in foodborne pathogens, 270 RTE street foods samples were collected in three densely populated Taiwanese cities. Among 70 ceftazidime non-susceptible isolates, 21 Stenotrophomonas maltophilia, 12 Pseudomonas spp., 22 Acinetobacter spp., and 15 Enterobacteriaceae isolates were identified. Phylogenetic analyses revealed high levels of genetic diversity between all of the different strains. Multi-drug resistance was observed in 86.4% (19/22) of Acinetobacter spp., 100% (12/12) of Pseudomonas spp., 71.4% (15/21) of S. maltophilia, and 93.3% (14/15) of Enterobacteriaceae. Of 70 ceftazidime non-susceptible isolates, 13 contained ESBLs or plasmid-mediated ampC genes and 23 contained ceftazidime resistance-associated efflux pumps, with Acinetobacter spp. identified as predominant isolate (69.6%; 16/23). AdeIJK pump RNA expression in Acinetobacter isolates was 1.9- to 2-fold higher in active efflux strains. Nine clinically resistant genes were detected: catIII and cmlA (chloramphenicol); aacC1, aacC2, aacC3, and aacC4 (gentamicin); tet(A), tet(C), and tet(D) (tetracycline). The scope and abundance of multidrug-resistant bacteria described in this report underscores the need for ongoing and/or expanded RTE monitoring and control measures.

Microbiological Survey of Packaged Ready-to-Eat Red Meats at Retail in New Zealand

A microbiological survey was undertaken on packaged ready-to-eat red meats available at retail in New Zealand. A total of 1,485 samples (297 lots of five samples each) were collected according to a sampling plan based on market share and regulatory regimes (Animal Products Act 1999 and Food Act 1981) and were tested against the microbiological limits specified in Food Standards Code (FSC) 1.6.1 applicable at the time of sampling. Each lot was tested as a composite for the presence or absence of Salmonella spp., coagulase-producing staphylococci, Listeria monocytogenes, and other Listeria spp. at the end of the manufacturer's stated shelf life. Individual samples within a positive lot were subsequently enumerated for L. monocytogenes. None of the samples contained Salmonella spp. or had coagulase-producing staphylococci counts above the acceptable level specified in FSC 1.6.1 (>100 CFU/g). Data showed that 93.6% (278 of 297 lots) of ready-to-eat red meat complied with the FSC 1.6.1 criteria applicable at the time of the survey. The failure of 19 lots (6.4%) was due to the presence of L. monocytogenes from product obtained from 8 of 33 producers tested. Thirteen samples of 95 positive samples were found to contain between 50 and 500 CFU/g L. monocytogenes, but all of these samples were manufactured by the same operator. Pulsed-field gel electrophoresis typing of all of the L. monocytogenes isolates obtained from the survey identified 12 different pulsotypes. Different pulsotypes were often identified in samples from the same operator sampled on separate occasions. A total of 46 lots (15.5%) contained Listeria spp. (including L. monocytogenes). The detection of Listeria in samples may highlight the existence of problems in operator processing and/or packaging processes and suggests that improvements in good hygienic practice and implementation of more effective risk mitigation strategies are needed.

Microbiological quality of pastrami and associated surfaces at the point of sale in Kayseri, Turkey

OBJECTIVE

The aim of this study is to trace the possible relations between the hygienic status of slicing utensils and the microbiological quality of pastrami.

STUDY DESIGN

A total of 75 pastrami retail markets were visited in Kayseri, Turkey, where the pastrami (a ready-to-eat meat product) is commonly produced and consumed. Sliced pastrami, the cutting board and knife surface swabs were collected from each pastrami retail point to trace possible sources of contamination.

METHODS

Samples were analysed for the presence of total viable counts (TVC), total coliforms, Escherichia coli, members of Enterobacteriaceae, Staphylococcus aureus and Listeria spp. In addition, pastrami samples were analysed for sulphite-reducing Clostridium spp. and Toxoplasma gondii.

RESULTS

When compared with the target values of related literatures, a total of 6 (8%) pastrami samples were found unsatisfactory as a result of TVC (5.3%), Enterobacteriaceae (5.3%), E. coli (2.6%), S. aureus (2.6%), Listeria spp. (2.6%) and Listeria monocytogenes (1.3%) contaminations. No T. gondii positivity was observed among the pastrami samples. None of the cutting board and knife surface swabs were found to harbour TVC level >10³ cfu/cm², E. coli and L. monocytogenes. For the total coliforms, 7 (9.3%) and 5 (6.6%) of cutting board and knife surface swabs were found to exceed the target value (<2.5 cfu/cm²), respectively. No statistically significant correlation was detected between the organisms on pastrami and slicing utensils indicating that pastrami were not cross-contaminated by the contact surfaces.

CONCLUSION

More emphasis needs to be placed for training of food handlers and to apply good hygienic practices at the point of pastrami sale. The conditions at retail points must be monitored and inspections should be tightened to protect public health.

An outbreak of an unusual strain of Listeria monocytogenes infection in North-East Scotland

Listeria monocytogenes infection is an important cause of illness and hospitalization in vulnerable individuals. In the present study, we describe a community outbreak of Listeria monocytogenes in the North-East region of Scotland, which was epidemiologically, environmentally and microbiologically linked to a local meat product and ready-to-eat product manufacturer. Infected individuals were interviewed, and an environmental investigation was conducted. Clinical and environmental samples were tested by culture, and isolates were typed by fluorescent amplified fragment length polymorphism (fAFLP). Three cases of Listeria monocytogenes were linked geographically, had the same serotype (1/2a) and were indistinguishable by fAFLP type XII.6. The human, food and environmental isolates were of the same serotype and were indistinguishable by molecular typing. This is the first community outbreak of L. monocytogenes reported in Scotland since the current outbreak surveillance was established in 1996. Epidemiological and laboratory evidence indicated poor hand hygiene, unhygienic practices and cross-contamination throughout the manufacturing process of ready-to-eat foods as a possible cause of the outbreak. More stringent control of commercial food establishments that provide ready-to-eat food and the need to advise specifically vulnerable groups, e.g., pregnant women, of the risk of L. monocytogenes in ready-to-eat food is urgently needed.

Predictive model for the growth kinetics of Staphylococcus aureus in raw pork developed using Integrated Pathogen Modeling Program (IPMP) 2013

A predictive model was performed to describe the growth of Staphylococcus aureus in raw pork by using Integrated Pathogen Modeling Program 2013 and a polynomial model as a secondary predictive model. S. aureus requires approximately 180 h to reach 5-6 log CFU/g at 10 °C. At 15 °C and 25 °C, approximately 48 and 20 h, respectively, are required to cause food poisoning. Predicted data using the Gompertz model was the most accurate in this study. For lag time (LT) model, bias factor (Bf) and accuracy factor (Af) values were both 1.014, showing that the predictions were within a reliable range. For specific growth rate (SGR) model, Bf and Af were 1.188 and 1.190, respectively. Additionally, both Bf and Af values of the LT and SGR models were close to 1, indicating that IPMP Gompertz model is more adequate for predicting the growth of S. aureus on raw pork than other models.

Odor fingerprinting of Listeria monocytogenes recognized by SPME-GC-MS and E-nose

Microorganisms can produce species-specific microbial volatile organic compounds (MVOCs), or odor compounds, which can be characterized by odor fingerprinting. The objective of this study was to characterize the odor fingerprint of Listeria monocytogenes. Solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and electronic nose (E-nose) were used to recognize the MVOCs of L. monocytogenes in pure culture medium. The main MVOCs of L. monocytogenes were identified by SPME-GC-MS analysis as alcohols, aldehydes, ketones, alkanes, and heterocyclics, among which the relative peak area of one compound, 3-hydroxy-2-butanone, increased along with the growth of L. monocytogenes. The odor fingerprint of L. monocytogenes at different growth stages could be clearly discriminated by E-nose. In addition, E-nose signals had a very good linear relationship with the concentration of this bacterium (R(2) = 0.9937). Our study may help to establish the analysis of the odor fingerprint of microorganisms as a potential routine method in microbiology.

Designing a risk communication strategy for health hazards posed by traditional slaughter of goats in Tshwane, South Africa

In African societies, traditional slaughter is linked to celebrations like weddings or births, as well as funerals and ancestor veneration. Participants in traditional slaughter of goats are at risk of exposure to hazards during slaughter, food preparation and consumption of goat meat. For risk mitigation strategies to be implemented, identification of the population at risk is required. This study is based on the premise that the demographic profile of people involved in traditional slaughter of goats is important for risk communication. Both structured and informal interviews were recorded and analysed using a thematic analysis. A total of 105 people were interviewed at taxi ranks in Tshwane, Gauteng. Of these, 48 were women and 57 men. The median age of women and men was 40.6 years and 44.3 years, respectively. The majority of respondents (61.9%, n = 65) interviewed were from the Gauteng Province. Sixty percent (n = 63) of respondents had a secondary education, whilst less than 4.81% (n = 5) of respondents had no formal education. This study demonstrated that interviewing commuters at taxi ranks gave access to a cross section of gender, age, language and origin. It was found that both genders were involved in traditional slaughter of goats. Risk communication strategies should thus target women as well as men. Communication strategies to mitigate the risks of traditional slaughter of goats should take into consideration the dynamic nature of demographic and cultural norms. In light of the wide demographic profile of the respondents, it was concluded that it should be possible to use taxi ranks for successful dissemination of food safety and occupational health risk mitigation messages.

Real-time PCR assay to differentiate Listeriolysin S-positive and -negative strains of Listeria monocytogenes

Due to the severity of the food-borne infection listeriosis, strict legislation governs the detectable and permissible limits at which Listeria monocytogenes is permitted in foods. These requirements, coupled with the ubiquitous nature of L. monocytogenes strains and the potential for epidemic outbreaks, mean that the pathogen can devastate affected sectors of the food industry. Although almost all L. monocytogenes strains have the potential to cause listeriosis, those implicated in the vast majority of epidemics belong to a subset of strains belonging to evolutionary lineage I. It has been established that a significant proportion of these strains, including those implicated in the majority of outbreaks, produce an additional hemolysin, designated listeriolysin S (LLS), which may be responsible for the enhanced virulence of these strains. In order to ultimately establish this definitively, it is important to first be able to rapidly discriminate between LLS-positive and -negative strains. Here, after essential genes within the LLS-encoding cluster, Listeria pathogenicity island 3, were identified by deletion mutagenesis, a real-time PCR assay which targets one such gene, llsX, was developed as a means of identifying LLS-positive L. monocytogenes. The specificity of the assay was validated against a panel of 40 L. monocytogenes strains (20 of which were LLS positive) and 25 strains representative of other Listeria species. Furthermore, 1 CFU of an LLS-positive strain per 25 g/ml of spiked foods was detected in less than 30 h when the assay was coupled with culture enrichment. The detection limit of this assay was 10 genome equivalents.