Foodborne pathogens in raw milk and cheese of sheep and goat origin: a meta-analysis approach

Raw milk cheeses from Beira Baixa, Portugal-A contributive study for the microbiological hygiene and safety assessment

Due to specific bacterial microbiota, raw milk cheeses have appreciated sensory properties. However, they may pose a threat to consumer safety due to potential pathogens presence. This study evaluated the microbiological contamination of 98 raw milk cheeses from Beira Baixa, Portugal. Presence and enumeration of Coagulase Positive Staphylococci (CPS), Listeria monocytogenes, Salmonella spp., pathogenic Escherichia coli, and indicator microorganisms (non-pathogenic E. coli and Listeria spp.) was attained. E. coli antimicrobial resistance (AMR) was also evaluated. PCR and/or Whole genome sequencing (WGS) was used to characterize E. coli, Salmonella spp. and L. monocytogenes isolates. Sixteen cheeses (16.3%) were classified as Satisfactory, 59 (60.2%) as Borderline and 23 (23.5%) as Unsatisfactory/Potential Injurious to Health. L. monocytogenes, CPS > 104 cfu g-1, Extraintestinal pathogenic E. coli (ExPEC) and Salmonella spp. were detected in 4.1%, 6.1%, 3.1% and 1.0% of the samples, respectively. Listeria innocua (4.1%) and E. coli > 104 cfu g-1 (16.3%) were also detected. AMR E. coli was detected in 23/98 (23.5%) of the cheese samples, of which two were multidrug resistant. WGS identified genotypes already associated to human disease and Listeria spp. cluster analysis indicated that cheese contamination might be related with noncompliance with Good Hygiene Practices during cheese production.

Distribution and prevalence of enterotoxigenic Staphylococcus aureus and staphylococcal enterotoxins in raw ruminants' milk: A systematic review

Enterotoxins produced by Staphylococcus aureus are a common cause of food poisoning, leading to significant gastrointestinal symptoms and even hospitalization. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched three electronic databases for studies on detection of staphylococcal enterotoxins or enterotoxigenic S. aureus in raw ruminant milk. The 128 studies included in this systematic review showed a worldwide distribution of studies on staphylococcal enterotoxins and enterotoxigenic S. aureus, with an increase in the number from 1980 to 2021, a shift in detection methods from enterotoxins to enterotoxin genes, and a preponderance of studies from Europe and South America. Most studies focused on milk from individual animals with mastitis, especially cattle. Based on 24 studies, the within-herd prevalence of enterotoxigenic S. aureus in raw milk samples was 11.6%. Many studies failed to report the health status of sampled animals, or the numerator and denominator data needed for prevalence calculation. Cultural and legislative differences, economic status, diagnostic capabilities, and public awareness are all likely factors contributing to the observed distribution of studies. Our review highlighted a significant gap in quality and completeness of data reporting, which limits full assessment of prevalence and distribution of hazards posed by raw milk.

Assessment of the Microbiological Safety and Hygiene of Raw and Thermally Treated Milk Cheeses Marketed in Central Italy between 2013 and 2020

A profile of the microbial safety and hygiene of cheese in central Italy was defined based on an analysis of 1373 cheeses sampled under the Italian National Control Plan for Food Safety spanning the years 2013 to 2020 and tested according to Commission Regulation (EC) No. 2073/2005 (as amended). A total of 97.4% of cheese samples were assessed as being satisfactory for food safety criteria and 80.5% for process hygiene criteria. Staphylococcal enterotoxin was found in 2/414 samples, while Salmonella spp. and Listeria monocytogenes were detected in 15 samples out of 373 and 437, respectively. Escherichia coli and coagulase-positive staphylococci counts were found unsatisfactory in 12/61 and 17/88 cheese samples, respectively. The impact of milking species, milk thermal treatment, and cheese hardness category was considered. A statistically significant association (p < 0.05) was found between milk thermal treatment and the prevalence of coagulase-positive staphylococci and Listeria monocytogenes and between hardness and unsatisfactory levels of Escherichia coli. The data depict a contained public health risk associated with these products and confirm, at the same time, the importance of strict compliance with good hygiene practices during milk and cheese production. These results can assist in bolstering risk analysis and providing insights for food safety decision making.

Antilisterial activity of raw sheep milk from two native Epirus breeds: Culture-dependent identification, bacteriocin gene detection and primary safety evaluation of the antagonistic LAB biota

Raw milk from native small ruminant breeds in Epirus, Greece, is a valuable natural source of autochthonous lactic acid bacteria (LAB) strains with superior biotechnological properties. In this study, two bulk milks (RM1, RM2) from two local sheep yards, intended for traditional Kefalotyri cheese production, were preselected for bacteriocin-like antilisterial activity by in vitro tests. Their antagonistic LAB biota was quantified followed by polyphasic (16S rRNA gene sequencing; IGS for Enterococcus; a multiplex-PCR for Leuconostoc) identification of 42 LAB (RM1/18; RM2/24) isolates further evaluated for bacteriocin encoding genes and primary safety traits. Representative isolates of the numerically dominant mesophilic LAB were Leuconostoc mesenteroides (10) in both RMs, Streptococcus parauberis (7) in RM2, and Lactococcus lactis (1) in RM1; the subdominant thermophilic LAB isolates were Enterococcus durans (8), E. faecium (6), E. faecalis (3), E. hirae (1), E. hermanniensis (1), Streptococcus lutetiensis (2), S. equinus (1) and S. gallolyticus (1). Based on their rpoB, araA, dsr and sorA profiles, six Ln. mesenteroides strains (8 isolates) were atypical lying between the subspecies mesenteroides and dextranicum, whereas two strains profiled with Ln. mesenteroides subsp. jonggajibkimchi that is first-time reported in Greek dairy food. Two RM1 E. faecium strain biotypes (3 isolates) showed strong, enterocin-mediated antilisterial activity due to entA/entB/entP possession. One E. durans from RM1 possessed entA and entP, while additional nine RM2 isolates of the E. faecium/durans group processed entA or entP singly. All showed direct (cell-associated) antilisterial activity only, as also both S. lutetiensis strains from RM2 did strongly. Desirably, no LAB isolate was β-hemolyrtic, or cytolysin-positive, or possessed vanA, vanB for vancomycin resistance, or agg, espA, hyl, and IS16 virulence genes. However, all three E. faecalis from RM2 possessed gelE and/or ace virulence genes. In conclusion, all Ln. mesenteroides strains, the two safe, enterocin A-B-P-producing E. faecium strains, and the two antilisterial S. lutetiensis strains should be validated further as potential costarter or adjunct cultures in Kefalotyri cheese. The prevalence of α-hemolytic pyogenic streptococci in raw milk, mainly S. parauberis in RM2, requires consideration in respect to subclinical mastitis in sheep and the farm hygiene overall.

Lactic acid bacteria from artisanal raw goat milk cheeses: technological properties and antimicrobial potential

In cheese-making, a starter culture composed of adequately chosen lactic acid bacteria (LAB) may be suitable to ensure the rapid acidification of milk, improve textural and sensory characteristics, and avoid pathogen proliferation. In this work, 232 LAB isolates collected from artisanal goat's raw milk cheeses produced in Portugal were evaluated for their antimicrobial capacity (at 10 and 37°C), as well as their acidifying and proteolytic properties. Among the 232 isolates, at least 98% of those isolated in De Man- Rogosa-Sharpe (MRS) agar presented antagonism against Listeria monocytogenes, Salmonella Typhimurium, or Staphylococcus aureus, whereas less than 28.1% of M17-isolated LAB showed antagonism against these pathogens. M17-isolated LAB displayed better results than MRS ones in terms of acidifying capacity. As for the proteolytic assay, only 2 MRS isolates showed casein hydrolysis capacity. Principal component analyses and molecular characterization of a subset of selected isolates were conducted to identify those with promising capacities and to correlate the identified LAB genera and species with their antimicrobial, acidifying, and/or proteolytic properties. Lactococcus strains were associated with the highest acidifying capacity, whereas Leuconostoc and Lacticaseibacillus strains were more related to antimicrobial capacities. Leuconostoc mesenteroides, Lactococcus lactis, and Lacticaseibacillus paracasei were the predominant organisms found. The results of this work highlight various strains with pathogen inhibition capacity and suitable technological properties to be included in a customized starter culture. In future work, it is necessary to appropriately define the starter culture and implement it in the cheese-making process to evaluate if the in-vitro capacities are observable in a real food system.

Mild Heat Treatment and Biopreservatives for Artisanal Raw Milk Cheeses: Reducing Microbial Spoilage and Extending Shelf-Life through Thermisation, Plant Extracts and Lactic Acid Bacteria

The microbial quality of raw milk artisanal cheeses is not always guaranteed due to the possible presence of pathogens in raw milk that can survive during manufacture and maturation. In this work, an overview of the existing information concerning lactic acid bacteria and plant extracts as antimicrobial agents is provided, as well as thermisation as a strategy to avoid pasteurisation and its negative impact on the sensory characteristics of artisanal cheeses. The mechanisms of antimicrobial action, advantages, limitations and, when applicable, relevant commercial applications are discussed. Plant extracts and lactic acid bacteria appear to be effective approaches to reduce microbial contamination in artisanal raw milk cheeses as a result of their constituents (for example, phenolic compounds in plant extracts), production of antimicrobial substances (such as organic acids and bacteriocins, in the case of lactic acid bacteria), or other mechanisms and their combinations. Thermisation was also confirmed as an effective heat inactivation strategy, causing the impairment of cellular structures and functions. This review also provides insight into the potential constraints of each of the approaches, hence pointing towards the direction of future research.

High multidrug resistance of Listeria monocytogenes and association with water sources in sheep and goat dairy flocks in Jordan

Listeria monocytogenes is a significant pathogen that causes listeriosis in humans and small ruminants. This study aimed to estimate the prevalence, antimicrobial resistance and risk factors of L. monocytogenes in small dairy ruminants in Jordan. A total of 948 milk samples were collected from 155 sheep and goat flocks across Jordan. L. monocytogenes was isolated from the samples, confirmed and tested for 13 clinically important antimicrobials. Data were also collected on the husbandry practices to identify risk factors for the presence of L. monocytogenes. The results showed that the flock-level prevalence of L. monocytogenes was 20.0% (95% CI; 14.46%-26.99%) and the prevalence in the individual milk samples was 6.43% (95% CI; 4.92%-8.36%). The univariable (UOR=2.65, p = 0.021) and multivariable (AOR=2.49, p = 0.028) analyses showed that using water from municipality pipelines as a water source in the flock reduced L. monocytogenes prevalence. All L. monocytogenes isolates were resistant to at least one antimicrobial. High percentages of the isolates were resistant to ampicillin (83.6%), streptomycin (79.3%), kanamycin (75.0%), quinupristin/dalfopristin (63.8%) and clindamycin (61.2%). About 83.6% of the isolates (94.2% and 75% of the sheep and goat isolates) exhibited multidrug resistance (resistance to ≥3 antimicrobial classes). In addition, the isolates exhibited fifty unique antimicrobial resistance profiles. Thus, it's recommended to restrict the misuse of clinically important antimicrobials and to chlorinate and monitor the water sources in sheep and goat flocks.

Antimicrobial Susceptibility Profile of Pathogenic and Commensal Bacteria Recovered from Cattle and Goat Farms

The use of antibiotics in food animals results to antimicrobial resistant bacteria that complicates the ability to treat infections. The purpose of this study was to investigate the prevalence of pathogenic and commensal bacteria in soil, water, manure, and milk from cattle and goat farms. A total of 285 environmental and 81 milk samples were analyzed for Enterobacteriaceae by using biochemical and PCR techniques. Susceptibility to antibiotics was determined by the Kirby-Bauer disk diffusion technique. A total of 15 different Enterobacteriaceae species were identified from goat and cattle farms. Manure had significantly higher (p < 0.05) Enterobacteriaceae (52.0%) than soil (37.2%), trough water (5.4%), and runoff water (5.4%). There was a significant difference (p < 0.05) in Enterobacteriaceae in goat milk (53.9%) and cow milk (46.2%). Enterobacteriaceae from environment showed 100% resistance to novobiocin, erythromycin, and vancomycin E. coli O157:H7, Salmonella spp., Enterococcus spp., and Listeria monocytogenes displayed three, five, six, and ten. AMR patterns, respectively. NOV-TET-ERY-VAN was the most common phenotype observed in all isolates. Our study suggest that cattle and goat farms are reservoirs of multidrug-resistant bacteria. Food animal producers should be informed on the prudent use of antimicrobials, good agricultural practices, and biosecurity measures.

Artisanal Household Milk Pasteurization Is Not a Determining Factor in Structuring the Microbial Communities of Labneh Ambaris: A Pilot Study

Labneh Ambaris is a traditional Lebanese dairy product traditionally made using raw goat's milk in earthenware jars, but recently the use of artisanally pasteurized milk was introduced for safety reasons. In this study, 12 samples of labneh Ambaris were studied, six made using raw goat's milk and six others using artisanally pasteurized goat's milk. These samples were collected during fermentation and their microbial compositions were analyzed. The 16S V3-V4 and the ITS2 regions of the rDNA were sequenced by DNA metabarcoding analyses for the identification and comparison of bacterial and fungal communities, respectively. The samples had high microbial diversity but differences in samples microbiota were unrelated to whether or not milk was pasteurized. The samples were consequently clustered on the basis of their dominant bacterial or fungal species, regardless of the milk used. Concerning bacterial communities, samples were clustered into 3 groups, one with a higher abundance of Lactobacillus helveticus, another with Lactobacillus kefiranofaciens as the dominant bacterial species, and the third with Lentilactobacillus sp. as the most abundant species. Species belonging to the Enterobacteriaceae family were detected in higher abundance in all raw milk samples than in artisanally pasteurized milk samples. As for fungal communities, the samples were clustered into two groups, one dominated by Geotrichum candidum and the other by Pichia kudriavzevii.

First Evidence of the Presence of the Causative Agent of Caseous Lymphadenitis-Corynebacterium pseudotuberculosis in Dairy Products Produced from the Milk of Small Ruminants

This study focused on the detection and quantification of selected bacteria and on the presence of enterotoxin genes in milk and dairy products from sheep and goat farms in the Czech Republic using quantitative real-time PCR (qPCR) and multiplex PCR (PCR). The presence of Corynebacterium pseudotuberculosis (CP), Mycobacterium avium subsp. paratuberculosis (MAP), Listeria monocytogenes, Staphylococcus aureus, S. aureus enterotoxin genes and methicillin-resistant Staphylococcus aureus (MRSA) was determined in 18 milk samples, 28 fresh cheeses, 20 ripened cheeses and 14 yoghurts. The serological status of the herds in relation to CP and MAP was taken into account. The most frequently detected bacterium was S. aureus (48.8%), and subsequent PCR revealed 11 MRSA positive samples. The S. aureus enterotoxin genes seg, sei and sec were detected in two goat cheeses. Cheese samples showed a statistically higher risk of SA and MRSA occurrence. CP (8.8%) and MAP (13.8%) were detected by qPCR on two different seropositive farms. Cultivation of qPCR positive CP samples on agar plates supplemented with potassium tellurite showed the presence of viable bacterium. The results obtained confirmed the necessity of monitoring the infectious status of dairy animals and rapid diagnosis of bacterial pathogens in milk and dairy products.

Nutritional Profile, Processing and Potential Products: A Comparative Review of Goat Milk

Goat milk contains an abundance of different macro and micro-nutrients. Compared with other milk, goat milk is a viable option due to its low allergy levels and is preferred for infants with cow milk allergies. A wide variety of goat milk-based products, including yoghurt, ice cream, fermented milk, and cheese, are available on the market. They are produced using effective processing technology and are known to exhibit numerous health benefits after consumption. However, goat milk consumption is limited in many nations (compared with cow, buffalo, camel, and sheep milk) due to a lack of awareness of its nutritional composition and the significance of its different byproducts. This review provides a detailed explanation of the various macronutrients that may be present, with special attention paid to each component, its purpose, and the health benefits it offers. It also compares goat milk with milk from other species in terms of its superiority and nutritional content, as well as the types, production methods, health advantages, and other beneficial properties of the various goat milk products that are currently available on the market.

Isolation of Listeria ivanovii from Bulk-Tank Milk of Sheep and Goat Farms-From Clinical Work to Bioinformatics Studies: Prevalence, Association with Milk Quality, Antibiotic Susceptibility, Predictors, Whole Genome Sequence and Phylogenetic Relationships

Simple Summary

An extensive countrywide study in Greece revealed that isolation of the zoonotic pathogens Listeria monocytogenes and Listeria ivanovii from the milk produced in sheep or goat farms was infrequent: 1.2% of farms sampled. The presence of pigs on the farms, low average relative humidity in the environment and a high number of animals on the farms were found to be associated with the isolations. Detailed assessment of the L. ivanovii strains, for which there is a paucity of information worldwide, revealed that the isolated strains belonged to the L. ivanovii subsp. ivanovii branch. All strains of the branch appeared to be very similar, with the distance between them being small, which suggests that global spread of this clonal branch is a recent evolutionary event or that the branch is characterized by a slow evolutionary rate.

Abstract

A cross-sectional study was performed in 325 sheep and 119 goat dairy farms in Greece. Samples of bulk-tank milk were examined by standard microbiological techniques for Listeria spp. Listeria monocytogenes was isolated from one (0.3%) and Listeria ivanovii from three (0.9%) sheep farms. No associations between the isolation of L. monocytogenes or L. ivanovii and milk quality were found. No resistance to antibiotics was identified. Three variables emerged as significant predictors of isolation of the organism: the presence of pigs, low average relative humidity and a high number of ewes on the farm. The three L. ivanovii isolates were assessed in silico for identification of plasmids, prophages, antibiotic resistance genes, virulence factors, CRISPRs and CAS genes. Phylogenetic analysis using the core genome revealed that the three strains belonged to the L. ivanovii subsp. ivanovii branch and were especially close to the PAM 55 strain. All strains of the branch appeared to be very similar, with the distance between them being small.

Prediction of storage time in different seafood based on color values with artificial neural network modeling

The determination of storage time in seafood could be performed by microbiological, chemical and sensory analysis. Among these mentioned methods color changes are one part of sensory analysis and are prior acceptance criteria from the point of consumers' view. In this study, a feedforward artificial neural network (ANN) model was developed to predict the storage time of seafood based on L*, a* and b* values. A total of 205 data set were compiled from the literature that represents the color changes of different seafood products to train and test the ANN model. Another set of data (n = 45) were used for the validation of developed ANN model. A multi-layer perceptron (MLP) was applied for the determination of agreements between input and output data. The most accurate topology were determined in accordance with the changes in the values of correlation coefficients (R²) and mean square errors (MSE) and found to be 30 neurons in the layer (R² = 0.81 and MSE = 0.2). The performance of ANN model was evaluated based on 6 criteria such as Mean Absolute Deviation (MAD), Mean Square Errors (MSE), Residual Mean Square Errors (RMSE), Correlation Coefficient (R²), Mean Absolute Error (MAE) and F-test statistics and found to be 0.2, 0.05, 0.002, 0.8, 0.71 and 1.06, respectively. Moreover, predicted and observed storage time values were fitted and regression coefficient was found to be 0.85. In accordance with the results of this study, the proposed ANN model is accurate, reliable, and proper for the estimation of storage time in seafood products.

Functional bacterial cultures for dairy applications: towards improving safety, quality, nutritional and health benefit aspects

Traditionally, fermentation was used to preserve the shelf life of food. Currently, in addition to favouring food preservation, well standardized and controlled industrial processes are also aimed at improving the functional characteristics of the final product. In this regard, starter cultures have become an essential cornerstone of food production. The selection of robust microorganisms, well adapted to the food environment, has been followed by the development of microbial consortia that provide some functional characteristics, beyond their acidifying capacity, achieving safer, high‐quality foods with improved nutritional and health‐promoting properties. In addition to starters, adjunct cultures and probiotics, which normally do not have a relevant role in fermentation, are added to the food in order to provide some beneficial characteristics. This review focuses on highlighting the functional characteristics of food starters, as well as adjunct and probiotic cultures (mainly lactic acid bacteria and bifidobacteria), with a specific focus on the synthesis of metabolites for preservation and safety aspects (e.g. bacteriocins), organoleptic properties (e.g. exopolysaccharides), nutritional (e.g. vitamins) and health improvement (e.g. neuroactive molecules). Literature reporting the application of these functional cultures in the manufacture of foods, mainly those related to dairy production, such as cheeses and fermented milks, has also been updated.

Detection of Coxiella burnetii DNA in sheep and goat milk and dairy products by droplet digital PCR in south Italy

Coxiella burnetii is a Gram-negative obligate intracellular bacterium that is responsible for Q fever, a common zoonosis which is present virtually worldwide. This microorganism infects a wide range of wild and domestic mammals, but the main reservoirs are cattle, goats and sheep, which also represent sources of human infection. A potential route of transmission of this pathogen to humans is the consumption of C. burnetii-contaminated raw milk or dairy products derived from contaminated raw milk, although the role of these foods as possible infection sources is controversial. The aims of this study were (i) to apply two ddPCR based assays targeting the C. burnetii IS1111 and icd genes for the detection and quantification of C. burnetii DNA, and (ii) to evaluate the occurrence of C. burnetii DNA in raw milk and raw milk products from sheep and goats in Apulia and Basilicata regions of Southern Italy. Of 413 milk and cheese samples tested, 78 were positive for the presence of C. burnetii DNA (18.9%), specifically, 68 of 285 milk samples (23.9%) and 10 of 128 cheese samples (7.8%) The presence of both IS1111 and icd genes was detected in only 2 (2.6%) of the 78 positive samples, while the remaining 76 (97.4%) were positive only for IS1111. C. burnetii DNA was specifically detected by the ddPCR method, whereas no cross-amplification was observed with the DNA of other foodborne bacterial pathogens. The sensitivity of the ddPCR method was determined as 0.35 and 0.56 copies/μL for IS1111 and icd genes, respectively. The findings of this study demonstrate the presence of C. burnetii DNA in a significant proportion of raw milk and dairy products. Although there is no conclusive epidemiological evidence that C. burnetii infection occurs via food, the presence of this organism in raw milk and dairy products made of raw milk should be considered a potential hazard. ddPCR is a useful tool to investigate the quality and safety of food products due to its sensitivity and precision, and could be applied to routine testing.

Prevalence, serovar distribution, and antibiotic resistance of Salmonella spp. isolated from pork in China: A systematic review and meta-analysis

The epidemiological characteristics of Salmonella spp. in pork have been widely studied in China, but the results remain inconsistent. This study aimed to summarize the epidemiological characteristics of Salmonella spp. isolated from pork, including its prevalence, serovar distribution, and antibiotic resistance rate. We systematically reviewed published studies on Salmonella spp. isolated from pork in China between 2000 and 2020 in two Chinese and three English databases and quantitatively summarized its prevalence, serovar distribution, and antibiotic resistance using meta-analysis methods. Furthermore, we conducted subgroup analysis and meta-regression to explore the source of the heterogeneity from historical changes and regional difference perspectives. Ninety-one eligible studies published between 2000 and 2020 were included. The meta-analysis showed that the pooled prevalence of Salmonella isolated from pork was 0.17 (95% CI: 0.14, 0.20), with a detected growing trend over time. For the proportions of serovars, Derby (0.32, 95% CI: 0.26, 0.38), Typhimurium (0.10, 95% CI: 0.07, 0.15) and London (0.05, 95% CI: 0.03, 0.08) were dominant in these studies. The antibiotic resistance rates were high for tetracycline (0.68, 95% CI: 0.59, 0.77), sulfisoxazole (0.65, 95% CI: 0.45, 0.83), ampicillin (0.43, 95% CI: 0.34, 0.53), streptomycin (0.42, 95% CI: 0.29, 0.56), and sulfamethoxazole (0.42, 95% CI: 0.25, 0.60). The results of this study revealed a high prevalence, the regional characteristics of serovar distribution, and the severe challenges of antibiotic resistance of Salmonella originating from pork in China, suggesting the potential increasing risk and disease burden. Therefore, it is necessary to improve the prevention and control strategies of Salmonella in pork.

A Strong Evidence Outbreak of Salmonella Enteritidis in Central Italy Linked to the Consumption of Contaminated Raw Sheep Milk Cheese

Salmonellosis is the second most commonly reported gastrointestinal infection in humans after campylobacteriosis, and an important cause of foodborne outbreaks in the EU/EEA. The vast majority (72.4%) of the salmonellosis foodborne outbreaks reported in EU in 2019 were caused by Salmonella Enteritidis, even if their total number due to this serovar decreased. In spring 2020, a foodborne outbreak of S. Enteritidis occurred in the Marche region (Central Italy), involving 85 people. The common exposure source was a cheese, pecorino “primo sale”, produced with raw sheep milk. The cheese batches were produced by two local dairies, with a livestock production facility, also including a sheep farm, being part of one dairy. Bacteriological analysis of samples collected allowed the detection of S. Enteritidis in animal faeces, environmental samples, raw-milk bulk tanks and milk taken from single animals. These data confirm that, despite the scarce scientific evidence, S. Enteritidis can infect sheep and be shed into the animals’ milk. Hence, this is a real risk for public health when unpasteurized milk is used in production of such cheese. The present paper describes the results of the investigations conducted to clarify this outbreak.

Monitoring by a Sensitive Liquid-Based Sampling Strategy Reveals a Considerable Reduction of Listeria monocytogenes in Smeared Cheese Production over 10 Years of Testing in Austria

Most Austrian dairies and cheese manufacturers participated in a Listeria monitoring program, which was established after the first reports of dairy product-associated listeriosis outbreaks more than thirty years ago. Within the Listeria monitoring program, up to 800 mL of product-associated liquids such as cheese smear or brine are processed in a semi-quantitative approach to increase epidemiological sensitivity. A sampling strategy within cheese production, which detects environmental contamination before it results in problematic food contamination, has benefits for food safety management. The liquid-based sampling strategy was implemented by both industrial cheese makers and small-scale dairies located in the mountainous region of Western Austria. This report considers more than 12,000 Listeria spp. examinations of liquid-based samples in the 2009 to 2018 timeframe. Overall, the occurrence of L. monocytogenes in smear liquid samples was 1.29% and 1.55% (n = 5043 and n = 7194 tested samples) for small and industrial cheese enterprises, respectively. The liquid-based sampling strategy for Listeria monitoring at the plant level appears to be superior to solid surface monitoring. Cheese smear liquids seem to have good utility as an index of the contamination of cheese up to that point in production. A modelling or validation process should be performed for the new semi-quantitative approach to estimate the true impact of the method in terms of reducing Listeria contamination at the cheese plant level.

Quality Characteristics and Consumer Acceptance of High-Moisture Mozzarella Obtained from Heat-Treated Goat Milk

High-moisture mozzarella is a pasta filata cheese manufactured from cow or buffalo milk that has spread all over the world. Its manufacturing from the milk of small ruminants (goat and sheep) has been recently proposed to innovate this ailing sector. Previously, a protocol was reported for making goat mozzarella from unpasteurized milk but, according to legislation, the microbiological safety of raw milk fresh cheeses is not guaranteed. In the present research, two new protocols were tested for producing mozzarella from pasteurized milk prepared by two different low-temperature long-time treatments (67 °C or 63 °C × 30 min). The obtained cheeses were subjected to physical–chemical and microbiological analyses and to consumer testing. The results showed that the heat treatments caused longer coagulation times than those reported in the literature, despite pre-acidification (at pH 5.93 or 6.35) having been performed to counterbalance the expected worsening of the coagulation aptitude. The obtained products showed differences in the chemical composition, texture, proteolysis, and lipolysis. Both pasteurization and pre-acidification played a role in determining these variations. Consumer testing indicated that mozzarella obtained from milk heated at the lower temperature and coagulated at a higher pH reached a good level of appreciation (62%).

Bacterial and fungal contaminants in caprine and ovine cheese: A meta-analysis assessment

The dairy industry is of great importance to the European economy contributing towards € 8.7 billion of the total trade surplus. Caprine and ovine milk amount to 3.1% of the 152 million tonnes of milk produced in Europe, 95% of which is transformed into dairy products such as cheese. This cheese is mostly produced in small holdings from untreated milk, making it a high-risk dairy product for human consumption. A total of 49 foodborne disease outbreaks caused by dairy products were registered in 2017 in Europe. Therefore, these products remain a serious health risk. This meta-analysis examined 30 studies assessing bacterial or fungal contamination of caprine or ovine milk cheeses. The significantly contaminating microbes were found to be Acremonium spp. (19%), Aspergillus spp. (23%), Bacillus spp. (2%), Brucella spp. (34%), Enterobactericae spp. (36%), Enterococcus spp. (28%), Escherichia spp. (15%), Fusarium spp. (21%), Geotrichum spp. (22%), Listeria spp. (11%), Mucor spp. (15%), Penicillium spp. (25%), Phoma spp. (20%), Rhizopus spp. (15%), Salmonella spp. (3%), Scopulariopsis spp. (19%) and Staphylococcus spp. (25%) in caprine and ovine cheese, indicating a variety of food pathogens as well as spoilers. Raw milk is nutritious hence prone to contamination. However, since traditional cheese is often made from untreated milk, it is important to educate cheesemakers of key safety measures and good manufacturing practice allowing for the safe production of these food items.

Zoonotic risks of pathogens from sheep and their milk borne transmission

Sheep were domesticated around 9000 BC in the Middle East, and since then milk from sheep gradually became very popular, not only for drinking but also for making cheeses and other dairy products. Nowadays, these dairy products are also important for people with an allergy to cow milk, and these products are an essential part of the local daily diet in regions of the world that are not suitable for cows and goats. Consumption of raw milk and raw milk products has a zoonotic risk, and with regard to sheep, the main pathogens associated with such dairy products are: Brucella melitensis, Campylobacter spp., Listeria spp., Salmonella spp., Shiga-toxin producing Escherichia coli, Staphylococcus aureus, tick borne encephalitis virus, and Toxoplasma gondii. Especially, young children, elderly people, pregnant women and immunocompromised (YOPI) persons, and those suffering from disease should be aware of the risk of consuming raw milk and raw milk products. This latter risk can be reduced by proper flock health management, prevention of contamination during milking, adequate milk processing, transport, and refrigerated storage. Only processes equaling pasteurization sufficiently reduce zoonotic risks from milk and milk products, but proper cooling is essential and recontamination must be prevented. Therefore, strict hygiene practices throughout the production process and supply chain especially for raw milk and raw dairy products, should be applied. Small scale production systems pose a greater risk compared to industrialized production systems because of a less protocolized and controlled production process. This manuscript describes zoonotic risks of pathogens from sheep and their milk borne transmission. Additionally, routes of contamination, possibilities for multiplication, and prevention measures thereof are described. We summarize some major human outbreaks caused by consumption of sheep milk and products made thereof, and finally discuss their implications.

Screening of Salmonella enterica Serovars, Typhi, Typhimurium, and Enteritidis in Raw Milk and Dairy Products in South-Khorasan, Iran: Conventional versus Molecular Method

Background and Objective:

Food-borne Salmonellosis has been reported as the second most common bacterial infection. Salmonella enterica subsp. enterica serotype enteritidis (S. Enteritidis) and S. enterica subsp. enterica serotype typhimurium (S. Typhimurium) are the most common serotypes worldwide as salmonellosis agents. Salmonella yyphi is the causative agent of typhoid fever worldwide. The purpose of the present study was to determine the contamination rate of raw milk and dairy products to Salmonella typhi, S. typhimurium and S. Enteritidis in South-Khorasan, Iran. It is very important in food safety risk assessment and human health.

Methods:

A total of 260 raw milk and 181 dairy products were obtained from South-Khorasan, Iran. Dairy samples were pre-enriched in buffered peptone water and enriched in Rappaport Vassiliadis (RV). Raw milk was enriched in RV. Plating of the enriched samples was carried out on Xylose Lysine Desoxycholate (XLD) agar and Brilliant Green agar (BGA). All of the enriched samples were also tested by M-PCR for detection of S. typhi, S. typhimurium and S. Enteritidis.

Results:

Among the 441 tested samples only 4 samples were contaminated with Salmonella spp. in culture method. PCR assay, didn’t find any positive sample regarding Salmonella spp. In chi-square test, the difference of two methods of isolation was significant (P< 0.05).

Conclusions:

In conclusion, the results of the present study showed a good hygienic state of raw milk and dairy products. Enrichment based PCR assay is more economical than time-consuming culture method for Salmonella detection.

Prevalence of Salmonella and Campylobacter spp. in Alternative and Conventionally Produced Chicken in the United States: A Systematic Review and Meta-Analysis

ABSTRACT

The burden of foodborne illness linked to the consumption of contaminated broiler meat is high in the United States. With the increase in popularity of alternative poultry rearing and production systems, it is important to identify the differences in food safety risks presented by alternative systems compared with conventional methods. Although many studies have been conducted that surveyed foodborne pathogen prevalence along the broiler supply chain, a systematic overview of all of the results is lacking. In the current study, a systematic review and meta-analysis were conducted to quantify the differences in prevalence of Salmonella and Campylobacter spp. in farm environment, rehang, prechill, postchill, and retail samples between conventional and alternative production systems. A systematic search of Web of Science and PubMed databases was conducted to identify eligible studies. Studies were then evaluated by inclusion criteria, and the included studies were qualitatively and quantitatively analyzed. In total, 137 trials from 72 studies were used in the final meta-analysis. Meta-analysis models were individually constructed for subgroups that were determined by sample type, pathogen, and production type. All subgroups possessed high amounts of heterogeneity (I2 > 75%). For environmental sample subgroups, Campylobacter prevalence was estimated to be 15.8 and 52.8% for conventional and alternative samples, respectively. Similar prevalence estimates for both production types were observed for Salmonella environmental samples and all retail samples. For conventional samples, Campylobacter and Salmonella prevalence was highest in prechill samples followed by rehang and postchill samples, respectively. The results herein will be useful in future quantitative microbial risk assessments for characterizing the differences in foodborne illness risks presented by different broiler production systems.

HIGHLIGHTS

Everybody loves cheese: crosslink between persistence and virulence of Shiga-toxin Escherichia coli

General cheese manufacturing involves high temperatures, fermentation and ripening steps that function as hurdles to microbial growth. On the other hand, the application of several different formulations and manufacturing techniques may create a bacterial protective environment. In cheese, the persistent behavior of Shiga toxin-producing Escherichia coli (STEC) relies on complex mechanisms that enable bacteria to respond to stressful conditions found in cheese matrix. In this review, we discuss how STEC manages to survive to high and low temperatures, hyperosmotic conditions, exposure to weak organic acids, and pH decreasing related to cheese manufacturing, the cheese matrix itself and storage. Moreover, we discuss how these stress responses interact with each other by enhancing adaptation and consequently, the persistence of STEC in cheese. Further, we show how virulence genes eae and tir are affected by stress response mechanisms, increasing either cell adherence or virulence factors production, which leads to a selection of more resistant and virulent pathogens in the cheese industry, leading to a public health issue.

Effects of Essential Oils on Escherichia coli Inactivation in Cheese as Described by Meta-Regression Modelling

The growing intention to replace chemical food preservatives with plant-based antimicrobials that pose lower risks to human health has produced numerous studies describing the bactericidal properties of biopreservatives such as essential oils (EOs) in a variety of products, including cheese. This study aimed to perform a meta-analysis of literature data that could summarize the inactivation of Escherichia coli in cheese achieved by added EOs; and compare its inhibitory effectiveness by application method, antimicrobial concentration, and specific antimicrobials. After a systematic review, 362 observations on log reduction data and study characteristics were extracted from 16 studies. The meta-regression model suggested that pathogenic E. coli is more resistant to EO action than the non-pathogenic type (p < 0.0001), although in both cases the higher the EO dose, the greater the mean log reduction achieved (p < 0.0001). It also showed that, among the factual application methods, EOs' incorporation in films render a steadier inactivation (p < 0.0001) than when directly applied to milk or smeared on cheese surface. Lemon balm, sage, shallot, and anise EOs showed the best inhibitory outcomes against the pathogen. The model also revealed the inadequacy of inoculating antimicrobials in cheese purposely grated for performing challenge studies, as this non-realistic application overestimates (p < 0.0001) the inhibitory effects of EOs.

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.

Chronic intramammary infection by Listeria monocytogenes in a clinically healthy goat - a case report

BACKGROUND

Listeria monocytogenes is a ubiquitous Gram-positive bacterium responsible for a severe foodborne disease in humans, and contaminated dairy products can be an important source of infection. Typically, infected dairy ruminants show clinical manifestations including encephalitis, septicemia, abortion, and diarrhea, but may also become asymptomatic carriers and shed L. monocytogenes in the feces acting as an important source of viable bacteria. Isolation from individual goat milk has been documented very rarely, and chronic, asymptomatic intramammary infection by L. monocytogenes with continuous milk shedding of viable bacteria has never been described in this dairy species.

CASE PRESENTATION

At the routine controls, cheese and bulk milk were positive for L. monocytogenes in a herd of 200 lactating Alpine goats, but none showed clinical signs of listeriosis. Individual milk was subjected to bacterial culture and a clinically healthy goat was identified as affected by a chronic intramammary infection (IMI) by L. monocytogenes. The goat had never shown clinical signs of mastitis or other diseases. Her right half-udder milk was positive to L. monocytogenes in two consecutive samples collected one week apart, as demonstrated by bacterial culture and molecular analysis. Mammary tissues collected after culling were also positive to L. monocytogenes by culture. Histological examination highlighted a chronic interstitial mastitis with leukocyte infiltration, atrophy of the alveoli and presence of corpora amylacea. Immunohistochemistry (IHC) and immunofluorescence (IF) confirmed the presence of high numbers of bacteria in the lumen of mammary alveoli, with intracellular bacteria mainly located in macrophages, but also present in neutrophils and epithelial cells. After culling of the positive goat, bulk tank milk tested negative to L. monocytogenes at the following controls.

CONCLUSION

This study demonstrates that L. monocytogenes can establish a chronic, subclinical IMI in goats with high numbers of bacteria shed in milk, representing a source of contamination for the herd and its dairy products. This underscores the importance of frequently monitoring all dairy herds that sell directly milk and/or fresh cheese and indicates that a chronic L. monocytogenes IMI should also be considered as source of bacteria when bulk tank milk contamination is detected in a dairy goat farm.