The Evolving Role of Coliforms As Indicators of Unhygienic Processing Conditions in Dairy Foods

Anise essential oil immobilized in chitosan microparticles: a novel bactericidal material for food protection

Foodborne infections in humans are one of the major concerns of the food industries, especially for minimally processed foods (MPF). Thereby, the packaging industry applies free chlorine in the sanitization process, ensuring the elimination of any fecal coliforms or pathogenic microorganisms. However, free chlorine's propensity to react with organic matter, forming toxic compounds such as trihalomethanes and haloacetic acid. Therefore, the present work aimed to synthesize a novel organic biomaterial as an alternative to free chlorine. Chitosan microparticles were produced, with Pimpinella anisum (anise) essential oil immobilized in the biopolymer matrix (MPsQTO). The characterization of this biomaterial was done through GC-MS/MS, FT-IR, and SEM. Antimicrobial assays proved that the MPsQTO presented antibacterial activity for Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, and Bacillus subtilis at 300 µL mL-1 of concentration. The fluorescence microscope also showed the MPsQTO targets the cytoplasmatic membrane, which is responsible for cell death in the first minutes of contact. Studies with the mutant B. subtilis (amy::pspac-ftsZ-gfpmut1) and the Saccharomyces cerevisiae D7 also proved that the biomaterial did not affect the genetic material and did not have any mutagenic/carcinogenic effect on the cells. The sanitization assays with pumpkin MPF proved that the MPsQTO is more effective than free chlorine, increasing the shelf-life of the MPF. Consequently, the novel biomaterial proposed in this work is a promising alternative to traditional chemical sanitizers.

Alpine grazing management, breed and diet effects on coagulation properties, composition, and microbiota of dairy cow milk by commercial mountain based herds

Cow milk microbiota has received increased attention in recent years, not only because of its importance for human health but also because of its effect on the quality and technological properties of milk. Several studies, therefore, have investigated the effect of various production factors on the microbial composition of milk. However, most of the previous studies considered a limited number of animals from experimental or single farm, which could have biased the results. Therefore, this study aimed to understand the effect of different alpine production systems on the compositional and microbiological quality of milk, considering commercial herds with different feeding intensities and cattle breeds. The results obtained in this work indicated that the month/season of sampling (July for summer or February for winter) more than farm, breed and cow diet exerted significant effects on cow milk parameters and microbiota. In particular, significant differences were observed for urea content in milk between sampling seasons. Differences in milk fat were mainly related to breed specific effects. From a microbiological point of view, statistically significant differences were found in presumptive lactic acid bacteria counts. Based on a culture-independent method, milk obtained in February harbored the highest number of Firmicutes (e.g., Lactobacillus) and the lowest number of Actinobacteria (e.g., Corynebacterium). Moreover, bacterial richness and diversity were higher in July/summer during alpine pasture season indicating a significant effect of pasture feed on the growth of bacterial communities. The results of this study highlighted the effect of month/season mainly related to differences in feeding management (e.g., access to pasture during vegetation period, concentrates supplementation) on composition and microbiota in milk.

Dynamics of microbiota and antimicrobial resistance in on-farm dairy processing plants using metagenomic and culture-dependent approaches

On-farm dairy processing plants, which are situated close to farms and larger dairy processing facilities, face unique challenges in maintaining environmental hygiene. This can impact various stages of dairy processing. These plants operate on smaller scales and use Low-Temperature-Long-Time (LTLT) pasteurization, making them more susceptible to microbial contamination through direct and indirect contact. Antimicrobial-resistant bacteria found on dairy farms pose risks to human health by potentially transferring resistance via dairy products. Our study aimed to investigate microbial distribution and antimicrobial resistance at four key stages: the farm, pre-pasteurization, post-pasteurization, and processing environments. We assessed microbial distribution by quantifying indicator bacteria and conducting metagenomic analysis. Antimicrobial resistance was examined by identifying resistance phenotypes and detecting resistance genes in bacterial isolates and metagenomes. Our results showed that the indicator bacteria were detected at all stages of on-farm dairy processing. We observed a significant reduction in aerobic microbes and coliforms post-pasteurization. However, contamination of the final dairy products increased, suggesting potential cross-contamination during post-pasteurization. Metagenomic analysis revealed that Pseudomonas, a representative psychrotrophic bacterium, was predominant in both the farm (24.1 %) and pre-pasteurization (65.9 %) stages, indicating microbial transfer from the farms to the processing plants. Post-pasteurization, Pseudomonas and other psychrotrophs like Acinetobacter and Enterobacteriaceae remained dominant. Core microbiota analysis identified 74 genera in total, including 13 psychrotrophic bacteria, across all stages. Of the 59 strains isolated from these plants, 49 were psychrotrophic. Antimicrobial resistance analysis showed that 74.6 % (44/59) of isolates were resistant to at least one antibiotic, with cefoxitin-, ampicillin-, amoxicillin-, and ticarcillin-resistant bacteria present at all stages. Identical antimicrobial resistance patterns were observed in isolates from serial stages of the same farm and season, suggesting bacterial transmission across stages. Additionally, 27.1 % (16/59) of isolates carried plasmid-mediated resistance genes, which were also detected in the metagenomes of non-isolated samples, indicating potential antimicrobial resistance gene transmission and their presence in uncultured bacteria. These findings reveal the persistence of antimicrobial-resistant psychrotrophic bacteria in on-farm dairy processing plants, which pose potential health risks via dairy consumption. Our study underscores the importance of both culture-dependent and culture-independent methods to fully understand their distribution and impact.

Different electrolytic treatments for food sanitation and conservation simulating a wash process at the packinghouse

Microorganisms are predominantly responsible for food deterioration, necessitating the sanitization and removal of these entities from food surfaces. The packinghouse employs free chlorine in the sanitization process; however, free chlorine's propensity to react with organic matter, forming potentially toxic compounds, has led to its restriction or outright prohibition in several European countries. Therefore, this study aims to assess various washing methods, emulating packinghouse conditions, utilizing diverse forms of electrolyzed water to impede microbial proliferation and significantly enhance the food's shelf life. The subject of investigation was cherry tomatoes. The findings revealed that electrolyzed water containing NaCl exhibited superior efficacy compared to electrolysis with Na2SO4. Both forms of electrolyzed water demonstrated noteworthy effectiveness in inhibiting microorganisms, resulting in a reduction of 2.0 Log CFU mL-1 for bacteria and 1.5 Log CFU mL-1 for fungi. The electrolyzed water also exhibited a comparable capability to free chlorine in removing fecal coliforms from the tomato surfaces. Notably, both electrolyzed water treatments extended the shelf life of cherry tomatoes by at least three days, accompanied by minimal or negligible residues of free chlorine. Consequently, the electrolyzed water formulations proposed in this study present themselves as promising alternatives to traditional packinghouse sanitizers.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05882-1.

Antibiotic residues and microbial contamination in pasteurized whole milk intended for human consumption

Background and Aim

Milk contamination for human consumption is one of the biggest concerns worldwide. To prevent milk contamination, it is important to implement sustainable production practices that ensure animal health and guarantee veterinary drugs have been used properly. This study aimed to detect antibiotic residues and microbial contamination in commercially available pasteurized whole milk intended for human consumption.

Materials and Methods

We conducted a cross-sectional study on all brands of pasteurized milk (n = 17) for human consumption in Medellín, Colombia, from February 30 to April 30, 2022. Six milk samples of each brand were collected every 15 days, resulting in 102 samples. IDEXX SNAPduo™ ST Plus test (IDEXX Laboratories Inc, Maine, USA) was used to detect cephalosporins residues to detect beta-lactam and tetracyclines. We detected mesophilic aerobic bacteria and coliforms using Chromocult Coliform Agar® (Merck KGaA, Darmstadt, Germany) and Plate-Count Agar® (Merck KGaA), respectively.

Results

Beta-lactam residues were found in 24.4% of the brands. No tetracyclines or cephalosporins were detected. Mesophilic aerobic bacteria and coliform contamination were detected in 42.6% and 12.8% of the brands, respectively. No fecal coliform contamination was detected.

Conclusion

This study demonstrated the presence of antibiotic residues and microbial contamination in commercially available pasteurized whole milk intended for human consumption in the study area, highlighting its potential public health implications.

Hygienic Practices of Vendors and Their Contribution to Coliform, Salmonella, and Shigella Bacteria of Raw Milk at Asella Town, Oromia, Ethiopia

Background

Coliform, Salmonella, and Shigella are among the most encountered bacteria in raw milk. This study is aimed at determining the extent of coliform, Salmonella, and Shigella bacteria in raw milk and vendor hygiene practices at Asella town, Oromia Regional State, Ethiopia, from March 1 to 30, 2022.

Methods

In this study, 210 milk vendors were included; each vendor provided a 50 ml sample of raw milk. Bacteria were isolated and identified using standard bacteriological techniques. Data were entered and analyzed using EPI info version 7 and SPSS version 22, respectively. A binary logistic regression model was applied to determine the factors associated with bacterial contamination of raw milk.

Results

The total contamination percentage of raw milk was 50 (23.8%) (95% CI: 18.1-29.5%). The predominant bacteria identified were coliform 43 (20.5%) followed by Salmonella species 7 (3.3%). Among coliforms, the predominant bacteria were Citrobacter species 15 (34.9%) followed by Enterobacter species 11 (25.6%), Escherichia coli and Serratia species each 6 (14%), and Klebsiella species 5 (11.6%). However, no Shigella was isolated in this study. Not having the habit of washing cow teats (p < 0.0001), the habit of washing teats with tap water (p < 0.0001), not having separate cloth during milking (p < 0.0001), not having a practice of testing milk for bacterial contamination (p = 0.027), and not having separate vending environment (p = 0.039) were significantly associated with bacterial contamination of raw milk.

Conclusions

The percentage of bacterial contamination of milk was found to be high. Participants without a habit of washing cow teats, a habit of washing milk utensils with only tap water, and not having separate vending environments were associated factors for bacterial contamination of raw milk. Milk vendors are advised to develop the habit of washing teats before milking, avoid washing teat/milk utensils only with tap water, and have a separate vending environment.

Decarboxylase activity of the non-starter lactic acid bacterium Loigolactobacillus rennini gives crack defects in Gouda cheese through the production of γ-aminobutyric acid

Ten Gouda cheese wheels with an age of 31 weeks from six different batch productions were affected by a crack defect and displayed an unpleasant off-flavor. To unravel the causes of these defects, the concentrations of free amino acids, other organic acids, volatile organic compounds, and biogenic amines were quantified in zones around the cracks and in zones without cracks, and compared with those of similar Gouda cheeses without crack defect. The Gouda cheeses with cracks had a significantly different metabolome. The production of the non-proteinogenic amino acid γ-aminobutyric acid (GABA) could be unraveled as the key mechanism leading to crack formation, although the production of the biogenic amines cadaverine and putrescine contributed as well. High-throughput amplicon sequencing of the full-length 16S rRNA gene based on whole-community DNA revealed the presence of Loigolactobacillus rennini and Tetragenococcus halophilus as most abundant non-starter lactic acid bacteria in the zones with cracks. Shotgun metagenomic sequencing allowed to obtain a metagenome-assembled genome of both Loil. rennini and T. halophilus. However, only Loil. rennini contained genes necessary for the production of GABA, cadaverine, and putrescine. Metagenetics further revealed the brine and the rennet used during cheese manufacturing as the most plausible inoculation sources of both Loil. rennini and T. halophilus.IMPORTANCECrack defects in Gouda cheeses are still poorly understood, although they can lead to major economic losses in cheese companies. In this study, the bacterial cause of a crack defect in Gouda cheeses was identified, and the pathways involved in the crack formation were unraveled. Moreover, possible contamination sources were identified. The brine bath might be a major source of bacteria with the potential to deteriorate cheese quality, which suggests that cheese producers should regularly investigate the quality and microbial composition of their brines. This study illustrated how a multiphasic approach can understand and mitigate problems in a cheese company.

Deep Impact: Shifts of Native Cultivable Microbial Communities on Fresh Lettuce after Treatment with Plasma-Treated Water

Foods consumed raw, such as lettuce, can host food-borne human-pathogenic bacteria. In the worst-case, these diseases cause to death. To limit illness and industrial losses, one innovative sanitation method is non-thermal plasma, which offers an extremely efficient reduction of living microbial biomass. Unfortunately, the total viable count (TVC), one of the most common methods for quantifying antimicrobial effects, provides no detailed insights into the composition of the surviving microbial community after treatment. To address this information gap, different special agars were used to investigate the reduction efficiency of plasma-treated water (PTW) on different native cultivable microorganisms. All tested cultivable microbial groups were reduced using PTW. Gram-negative bacteria showed a reduction of 3.81 log10, and Gram-positive bacteria showed a reduction of 3.49 log10. Fungi were reduced by 3.89 log10. These results were further validated using a live/dead assay. MALDI-ToF (matrix-assisted laser-desorption-ionization time-of-flight)-based determination was used for a diversified overview. The results demonstrated that Gram-negative bacteria were strongly reduced. Interestingly, Gram-positive bacteria and fungi were reduced by nearly equal amounts, but could still recover from PTW treatment. MALDI-ToF mainly identified Pseudomonas spp. and groups of Bacillus on the tested lettuce. These results indicate that the PTW treatment could efficiently achieve a ubiquitous, spectrum-wide reduction of microbial life.

Seasonal Comparison of Microbial Hygiene Indicators in Raw and Pasteurized Milk and Cottage Cheese Collected across Dairy Value Chain in Three Regions of Ethiopia

A longitudinal design with a simple random sampling method was used to collect and compare microbial hygiene levels between the dry season (January to April) and wet season (June to August). A total of 456 milk and cottage cheese samples were collected from each site along the dairy value chain from three regions. Enumeration of total aerobic mesophilic bacteria (APC), total coliforms (TCC), and Escherichia coli (EC) was performed according to standard methods. Independent t-tests were employed to assess the significant variation at (p < 0.05) between the two seasons. The cumulative result of APC of 7.61 log cfu/mL and g and TCC of 3.50 log cfu/mL in the dry season were significantly higher than the wet season of 7.15 log cfu/mL and 2.49 log cfu/mL, respectively, whereas generic E. coli count (EC) was significantly higher in the wet season (0.70 log cfu/mL and g) than that in the dry season (0.40 log cfu/mL and g). The results of hygienic indicator microbial load significantly varied with season. Hence, hygienic milk production and handling practices that comprehend seasonal influence should be implemented to improve the safety of milk.

Microbiological Survey and Antimicrobial Resistance of Foodborne Bacteria in Select Meat Products and Ethnic Food Products Procured from Food Desert Retail Outlets in Central Virginia, USA

In food desert areas, low-income households without convenient transportation often shop at small, independently owned corner markets and convenience stores (SIOMs). Studies indicate a higher potential for reduced product quality and safety of foods sold at SIOMs, with more critical and non-critical code violations in the region. This study aimed to assess the difference in market scale on the microbiological quality in select food products procured from food deserts in Central Virginia. A total of 326 samples consisting of meat products (i.e., ground beef, chicken, and sausage), ethnic food products (i.e., ox tail, stock fish bite, egusi ground, and saffron powder), and food packaging surfaces procured from ten registered SIOMs and nine large chain supermarkets (LCSMs) between August 2018 and March 2020 were evaluated. Higher levels of aerobic mesophile and coliform counts were found in SIOMs-acquired samples than in LCSMs-acquired samples, as demonstrated by the lower food safety compliance rate of SIOMs. Regardless of SIOMs or LCSMs, Campylobacter, E. coli, Listeria, and Salmonella were detected in 3.6%, 20.9%, 5.5%, and 2.7% of samples, respectively. The majorities of Campylobacter (75%, 6/8) and Salmonella (83.3%, 5/6) detected were from SIOMs-acquired samples including ethnic food products. Among the tested antimicrobials, AMP (100%) and TOB (100%) showed the highest frequency of resistance among Campylobacter, TCY (69.9%) among E. coli, NAL (100%) among Listeria, and TCY (50%) among Salmonella, respectively. The prevalence of multi-drug resistance (MDR) and non-susceptibility in Campylobacter and non-susceptibility in Listeria isolated from SIOMs-acquired food products were lower than those isolated from LCSMs-acquired samples. A higher price of the same brand name commodity sold at SIOMs than those sold at LCSMs was also observed, indicating an increased financial burden to economically challenged residents in food desert areas, in addition to food safety concerns. Elaborated and in-depth research on a larger-scale sample size with a greater diversity of products is needed to determine and intervene in the cause(s) of the observed differences in the prevalence of the pathogens and AMR profiles.

Pre-Weaned Calf Rearing on Northern Irish Dairy Farms-Part 2: The Impact of Hygiene Practice on Bacterial Levels in Dairy Calf Rearing Environments

Pre-weaned dairy calves are very susceptible to disease in the first months of life due to having a naïve immune system and because of the numerous physiological stressors they face. Hygiene management is a key element in minimizing enteric disease risk in calves by reducing their exposure to pathogens. Samples of milk, concentrate feed and drinking water, boot swabs of bedding and swabs of feed equipment were collected from 66 dairy farms as part of a survey of calf rearing practice and housing design. All the samples were cultured to determine total viable counts (TVC), total coliforms (TCC) and Escherichia coli as indicators of hygiene. Target ranges for levels of TVC, TCC and E. coli were defined from the literature and the sample results compared against them. The TVC targets in milk, MR and water were <4.0 log₁₀ CFU/mL. TCC and E. coli targets of <1.1 log₁₀ CFU/mL (the detection limit) were used for milk, MR, concentrate feed and feeding equipment. For water, the TCC and E. coli targets were <1.0 log₁₀ CFU/100 mL. The targets used for bedding boot swabs were <6.3 log₁₀ TVC CFU/mL and <5.7 log₁₀ TCC or E. coli CFU/mL. Farm management factors were included as fixed effects in a generalized linear mixed model to determine the probability of samples being within each hygiene indicator target range. Milk replacer samples obtained from automatic feeders were more likely to be within the TVC target range (0.63 probability) than those prepared manually (0.34) or milk samples taken from the bulk tank (0.23). Concentrate feed samples taken from buckets in single-calf pens were more likely to have E. coli detected (0.89) than samples taken from group pen troughs (0.97). A very small proportion of water samples were within the indicator targets (TVC 9.8%, TCC 6.0%, E. coli 10.2%). Water from self-fill drinkers had a lower likelihood of being within the TVC target (0.03) than manually filled buckets (0.14), and water samples from single pens were more likely to be within TCC target ranges (0.12) than those from group pens (0.03). However, all self-fill drinkers were located in group pens so these results are likely confounded. Where milk feeders were cleaned after every feed, there was a greater likelihood of being within the TVC target range (0.47, compared with 0.23 when not cleaned after every feed). Detection of coliforms in milk replacer mixing utensils was linked with reduced probability of TVC (0.17, compared with 0.43 when coliforms were not detected) and TCC (0.38, compared with 0.62), which was within target in feeders. Key factors related to increased probability of bedding samples being within TCC target range were use of group calf pens (0.96) rather than single-calf pens (0.80), use of solid floors (0.96, compared with 0.76 for permeable floors) and increased space allowance of calves (0.94 for pens with ≥2 m²/calf, compared with 0.79 for pens with <2 m²/calf). Bedding TVC was more likely to be within the target range in group (0.84) rather than in single pens (0.66). The results show that hygiene levels in the calf rearing environment vary across farms and that management and housing design impact hygiene.

Microbial Contamination and Antibiotic Resistance in Marketed Food in Bangladesh: Current Situation and Possible Improvements

Antimicrobial resistance (AMR) is a public health problem worldwide. Bangladesh, like its neighboring countries, faces many public health challenges, including access to safe food, inadequate food surveillance, as well as increasing AMR. This study investigated bacterial contamination and the AMR profile of pathogens in marketed food in Bangladesh and explored barriers to reducing AMR in the country. We collected 366 tomatoes, 359 chicken and 249 fish samples from 732 vendors in traditional markets in urban, peri-urban and rural areas in Bangladesh, as well as from 121 modern retails in Dhaka capital to analyse Vibrio cholerae and Escherichia coli in fish, Salmonella in chicken, and Salmonella and E. coli in tomatoes. Antibiotic susceptibility against 11 antibiotics was tested using a disc diffusion test and interpreted by an automated zone inhibition reader. In addition, a qualitative study using key informant interviews was conducted to explore antimicrobial use and AMR reduction potential in Bangladesh. We found E. coli in 14.21% of tomatoes and 26.91% of fish samples, while 7.38% of tomatoes and 17.27% of chicken were positive for Salmonella, and 44.98% of fish were positive for Vibrio cholerae. In total 231/319 (72.4%) of all pathogens isolated were multidrug-resistant (MDR) (resistant to three or more antibiotic groups). Qualitative interviews revealed an inadequate surveillance system for antibiotic use and AMR in Bangladesh, especially in the agriculture sector. To be able to fully understand the human health risks from bacterial hazards in the food and the AMR situation in Bangladesh, a nationwide study with a one health approach should be conducted, within all sectors, including AMR testing as well as assessment of the antimicrobial use and its drivers.

Factors affecting the microbiological quality and contamination of farm bulk milk by Staphylococcus aureus in dairy farms in Asella, Ethiopia

BACKGROUND

The determination of the microbiological quality and safety of raw milk and the associated influencing factors at the farm level is very critical given that the quality or safety of subsequent products that are further produced depends on this. Therefore, this study aimed to determine the microbiological quality and safety of bulk milk and identify associated risk factors, and assess the presence/absence of S. aureus in bulk milk with potential contaminating sources in dairy farms in Asella, Ethiopia.

RESULTS

The geometric means of bacterial counts in farm bulk milk were 5.25 log cfu/ml, 3.1 log cfu/ml and 2.97 log cfu/ml for total bacterial count (TBC), coliform count (CC) and coagulase-positive staphylococci count (CPS), respectively. Of the 50 dairy farms, 66, 88, and 32% had TBC, CC and CPS counts, respectively, that exceeded the standard international limits for raw cow's milk intended for direct human consumption. TBC tended to increase as CC increased in bulk milk (r = 0.5). In the final regression model, increased TBC, CC and the contamination of farm bulk milk by S. aureus were significantly associated with dirty barns, dirty cows and soiled udder and teats. TBC was higher during the rainy season than during the dry season. The reported practice of washing teats with warm water significantly decreased CC and CPS. The occurrence of S. aureus was significantly (p < 0.05) higher in bulk farm milk (42%) than in pooled udder milk (37.3%), teat swabs (22.5%), milkers' hand swabs (18%), bulking bucket swabs (16.7%), milking container swabs (14%), and water for cleaning of udder and milkers' hands (10%). The questionnaire survey result showed widespred raw milk consumption habits, low level of training and poor hygienic milking practices.

CONCLUSIONS

This study revealed low-quality bulk farm milk with high bacterial counts and a high occurrence of S. aureus. This indicates the potential food safety risks due to consumption of raw milk or its products. This study suggests awareness creation to dairy farmers and the public on hygienic milk production and heat treatment of milk before consumption.

Invited review: Redefining raw milk quality-Evaluation of raw milk microbiological parameters to ensure high-quality processed dairy products

Raw milk typically has little bacterial contamination as it leaves the udder of the animal; however, through a variety of pathways, it can become contaminated with bacteria originating from environmental sources, the cow herself, and contact with contaminated equipment. Although the types of bacteria found in raw milk are very diverse, select groups are particularly important from the perspective of finished product quality. In particular, psychrophilic and psychrotolerant bacteria that grow quickly at low temperatures (e.g., species in the genus Pseudomonas and the family Enterobacteriaceae) and produce heat-stable enzymes, and sporeforming bacteria that survive processing hurdles in spore form, are the 2 primary groups of bacteria related to effects on processed dairy products. Understanding factors leading to the presence of these important bacterial groups in raw milk is key to reducing their influence on processed dairy product quality. Here we examine the raw milk microbiological parameters used in the contemporary dairy industry for their utility in identifying raw milk supplies that will perform well in processed dairy products. We further recommend the use of a single microbiological indicator of raw milk quality, namely the total bacteria count, and call for the development of a whole-farm approach to raw milk quality that will use data-driven, risk-based tools integrated across the continuum from production to processing and shelf-life to ensure continuous improvement in dairy product quality.

Pasteurized milk quality in Brazil: a cross-sectional study over five years

This research communication delineates the quality of pasteurized cow milk sold in Brazil from 2015 to 2020. A cross-sectional study was performed gathering 1749 samples, which were evaluated for microbiological and physicochemical parameters, including Salmonella spp., total and thermotolerant coliforms, freezing point, alkaline phosphatase and lactoperoxidase. The proportion of compliant and non-compliant samples was compared through the years and jurisdiction of the inspection services. Interactions between the design and response variables were assessed by log-linear analysis. Overall, a considerable non-conformity rate (12%) was found for at least one microbiological or physicochemical parameter. Post-pasteurization contamination by coliforms was the major challenge for dairy industries. Notably, the non-compliance rate for freezing point increased during the SARS-CoV-2 pandemic. In addition, the ability to comply was linked to the type of inspection service. Thus, it is suggested that the SARS-CoV-2 pandemic is affecting the dairy industries in Brazil, and we strengthen the need for more studies monitoring the quality of milk over the years, which could assist industries and regulatory agencies to ensure the compliance of pasteurized milk.

Synthesis of active packaging films from Lepidium sativum gum/polyvinyl alcohol composites and their application in preserving cheddar cheese

The interest in active packaging for extending food shelf life has increased lately. Moreover, the negative impact of synthetic plastic wastes on the environmental motivated the researchers to seek for bio-based alternatives. In this context, active packaging film made of a composite composed of Lepidium sativum extract (LSE), polyvinyl alcohol (PVA), and a fixed amount of hyperbranched polyamide amine (PAMAM) were prepared. The chemical, thermal, and mechanical properties of the film were investigated. Moreover, we examined the extract's constituents and antioxidant properties. Cheddar cheese samples were coated with films of different compositions. The samples coated with active packaging films showed a longer preservation time of up to 4 weeks compared to other samples, which noticeably deteriorated. The films showed potent antimicrobial activity against five food-borne bacteria: three gram-negative bacteria including Escherichia coli O157.H7, Pseudomonas aeruginosa, and Salmonella Typhimurium, and two gram-positive bacteria, Listeria monocytogenes, and Staphylococcus aureus. Applying PVA films containing LSE improved the microbiological quality and delayed the visible decay of cheddar cheese. The oxidizability of the fat extracted from different cheese samples was 0.40-0.98, confirming oxidation resistance. Finally, cheese samples coated with treated films were protected from forming trans fats compared to other samples, demonstrating the effectiveness of modified films as antioxidant, antimicrobial, and food-preserving packaging.

Criteria and methodologies for determining the causes of swelling of canned tomatoes in tinplate containers

This review provides the current laboratory criteria for the detection and evaluation of the possible causes of alteration of non-concentrated industrial derivatives of tomatoes (peeled tomatoes, pulps, purees, sauces, and fillets), packaged in coated or uncoated tinplate cans. We discuss how the product alterations are typically the consequence of technological errors either in the can production, or in the storage process, or in the product sterilization. The described procedures include the quantitative determination of the distribution of gases (H₂ , CO₂ , N₂ , and O₂ ) present in the headspace of the container. The gas composition and ratios can be used as markers to allow easy diagnosis of the causes of microbiologic and/or physical-chemical alterations of the tomatoes, which are usually made evident by swelling of the containers. These tests should be integrated by microbiological analyses aimed at a restricted group of microorganisms, with the chemical analysis of the container and the chemical analysis of the altered product. By way of example, we report the assessment of the causes of alteration in four different case-studies.

Microbiological Quality and Safety of Traditional Raw Milk Cheeses Manufactured on a Small Scale by Polish Dairy Farms

Polish raw milk artisanal cheese may pose a threat to consumer safety due to pathogen presence. The aim of this study was to assess the microbiological safety, quality and physicochemical composition of cow’s and goat’s milk fresh cheeses produced by farmers on a small scale. A total of 62 samples of six cheese types were analyzed for Listeria monocytogenes, Salmonella spp., lactic acid bacteria and coliform presence and concentration levels. The physicochemical analysis estimated energy, water, protein, fat, carbohydrate, ash and salt content. The cheeses were also tested for heavy metal contamination. Listeria monocytogenes and Salmonella spp. were not detected in any of the samples. Coliforms were present in all the goat’s milk cheeses and only in two of the cow’s milk cheeses. Low levels of cadmium, below 0.008 ppm, were detected in three of the cows’ milk samples. The raw milk cheeses studied were free of the pathogens examined and were of high nutritional value.

Microbial Communities of Artisanal Fermented Milk Products from Russia

Fermented milk products (FMPs) have numerous health properties, making them an important part of our nutrient budget. Based on traditions, history and geography, there are different preferences and recipes for FMP preparation in distinct regions of the world and Russia in particular. A number of dairy products, both widely occurring and region-specific, were sampled in the households and local markets of the Caucasus republics, Buryatia, Altai, and the Far East and European regions of Russia. The examined FMPs were produced from cow, camel, mare’s or mixed milk, in the traditional way, without adding commercial starter cultures. Lactate and acetate were the major volatile fatty acids (VFA) of the studied FMPs, while succinate, formate, propionate and n-butyrate were present in lower concentrations. Bacterial communities analyzed by 16S rRNA gene V4 fragment amplicon sequencing showed that Firmicutes (Lactococcus, Lactobacillus, Streptococcus, Lentilactobacillus and Leuconostoc) was the predominant phylum in all analyzed FMPs, followed by Proteobacteria (Acetobacter, Klebsiella, Pseudomonas and Citrobacter). Lactobacillus (mainly in beverages) or Lactococcus (mainly in creamy and solid products) were the most abundant community-forming genera in FMPs where raw milk was used and fermentation took place at (or below) room temperature. In turn, representatives of Streptococcus genus dominated the FMPs made from melted or pasteurized milk and fermented at elevated temperatures (such as ryazhenka, cottage cheese and matsoni-like products). It was revealed that the microbial diversity of koumiss, shubat, ryazhenka, matsoni-like products, chegen, sour cream and bryndza varied slightly within each type and correlated well with the same products from other regions and countries. On the other hand, the microbiomes of kefir, prostokvasha, ayran, cottage cheese and suluguni-like cheese were more variable and were shaped by the influence of particular factors linked with regional differences and traditions expressed in specificities in the production process. The microbial diversity of aarts, khurunga, khuruud, tan, ayran and suluguni-like cheese was studied here, to our knowledge, for the first time. The results of this study emphasize the overall similarity of the microbial communities of various FMPs on the one hand, and specificities of regional products on the other. The latter are of particular value in the age of globalization when people have begun searching for new and unusual products and properties. Speaking more specifically, these novel products, with their characteristic communities, might be used for the development of novel microbial associations (i.e., starters) to produce novel products with improved or unique properties.

Occurrence of antibiotic resistance among Enterobacterales isolated from raw and ready-to-eat food - phenotypic and genotypic characteristics

The aim of this study was phenotypic and genotypic characterization of antibiotic-resistant food-borne Enterobacterales. The largest number of isolates was identified as Enterobacter cloacae (42.4%) followed by Escherichia coli (9.8%), Proteus mirabilis, Salmonella enterica, Proteus penneri, Citrobacter freundii (7.6% each), Citrobacter braakii (6.6%), Klebsiella pneumoniae and Klebsiella oxytoca (5.4% each). More than half of isolates (52.2%) were resistant to at least one antibiotic. The majority were resistant to amoxicillin-clavulanate (28.3%) and ampicillin (19.5%). ESBL(+) phenotype was showed by 26 isolates and AmpC(+) phenotype by 32 isolates. The bla_CTX-M gene was carried by 53.8% of ESBL-positive isolates, gene from CIT family by 43.8% of AmpC-positive isolates. Our results suggest that more attention should be paid to antibiotic resistance of food-borne Enterobacterales. The presence of transmissible antibiotic resistance markers is an important criterion in the evaluation of food safety.

Exploring the microbial composition of Holstein Friesian and Belgian Blue colostrum in relation to the transfer of passive immunity

For centuries, multicellular organisms have lived in symbiosis with microorganisms. The interaction with microorganisms has been shown to be very beneficial for humans and animals. During a natural birth, the initial inoculation with bacteria occurs when the neonate passes through the birth canal. Colostrum and milk intake are associated with the acquisition of a healthy gut flora. However, little is known about the microbial composition of bovine colostrum and the possible beneficial effects for the neonatal calf. In this prospective cohort study, the microbial composition of first-milking colostrum was analyzed in 62 Holstein Friesian (HF) and 46 Belgian Blue (BB) cows by performing amplicon sequencing of the bacterial V3-V4 region of the 16S rRNA gene. Calves received, 3 times, 2 L of their dam's colostrum within 24 h after birth. Associations between colostral microbial composition and its IgG concentration, as well as each calf's serum IgG levels, were analyzed. Colostrum samples were dominated by the phyla Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria. The 10 most abundant genera in the complete data set were Acinetobacter (16.2%), Pseudomonas (15.1%), a genus belonging to the Enterobacteriaceae family (4.9%), Lactococcus (4.0%), Chryseobacterium (3.9%), Staphylococcus (3.6%), Proteus (1.9%), Streptococcus (1.8%), Enterococcus (1.7%), and Enhydrobacter (1.5%). The remaining genera (other than these top 10) accounted for 36.5% of the counts, and another 8.7% were unidentified. Bacterial diversity differed significantly between HF and BB samples. Within each breed, several genera were found to be differentially abundant between colostrum of different quality. Moreover, in HF, the bacterial composition of colostrum leading to low serum IgG levels in the calf differed from that of colostrum leading to high serum IgG levels. Results of the present study indicate that the microbes present in colostrum are associated with transfer of passive immunity in neonatal calves.

Experimental study on total coliform violations in the complied NH2CL, O3, and UV treated municipal water supply system

Water quality has become a severe concern on a global scale, owing mostly to the rapid increase of the nation's development. According to Malaysia's Natural Resources and Environment Ministry, poor water management is the primary cause of the country's water quality problems. Many river systems are polluted by home and industrial pollutants, according to the findings of research in Malaysia and comparable difficulties in a few other nations. Hence, the following are the research's goals: (1) To look into what is causing the infractions. (2) To undertake the inquiry, develop a thorough hypothesis. (3) To detect dangerous germs by sampling the most usually infected regions. (4) To develop a test for Total Coliform violations in chlorine-treated water at the water treatment plant and in water distribution systems. As a result, the most major barrier to ensuring the safe delivery of treated water to consumers and protecting human health from water-related diseases is the drinking water treatment process. As a result, practically all water treatment systems around the world, including those in the USA, use a chlorine-based procedure to disinfect the water system during treatment. According to studies, the ideal way of disinfecting treated water is both safe and beneficial. Any sort of pandemic or biologically caused disease has no societal implications. Many countries began to suffer in 2009 as a result of e-coli and total coliform contamination in their water systems, leading to ambiguity in disinfection methods. Some water from UNMC's coolers was within the guidelines, while some exceed them. Water coolers at Block E (614 m) and Block B (605 m), for example, measured 12 CFU/100 ml and 11 CFU/100 ml, respectively. Water coolers should be cleaned regularly to ensure that they perform correctly. Further, the microbial population was found to be higher at water storage tanks than that is at the water cooler. This demonstrates how a water cooler fulfils its purpose of filtering and trapping germs to provide clean drinking water.

Microbial Profile and Safety of Chicken Eggs from a Poultry Farm and Small-Scale Vendors in Hawassa, Southern Ethiopia

A freshly laid hen’s egg is devoid of microorganism, but soon after oviposition, it is contaminated by various spoilage and pathogenic microorganisms. The aim of this study was to assess the microbial profile and safety of chicken eggs in Hawassa City. A total of 60 egg samples were collected from Hawassa University Poultry Farm (HUPF) and small-scale vendors in Hawassa. The samples were analyzed for aerobic mesophilic bacterial count (AMBC), Staphylococcal count (SC), Enterobacteriaceae count (EC), total coliform count (TCC), fecal coliform count (FCC), and yeast and mold count (YMC). Moreover, the dominant mesophilic aerobic bacterial genera and common bacterial pathogens were identified by phenotypic methods. Accordingly, the mean aerobic mesophilic bacterial load of the shell surface rinsate of the egg samples ranged from 1.22 log10 CFU/ml to 9.7 log10 CFU/ml, while that of the internal contents ranged from 1.52 log CFU/ml to 9.36 log CFU/ml. The microbial load values of the egg contents were beyond the international recommended acceptable limits and suggested incipient spoilage. The mesophilic aerobic bacterial genera of the shell and internal contents of the egg samples were similarly dominated by Pseudomonas, Micrococcus, and Staphylococcus. The incidence of E. coli in shell rinsate and egg content was 10% (6 of 60) and 1.67% (1 of 60), respectively. Salmonellae were detected in shell rinsate of six egg samples (10%) and in the contents of eight samples (13.33%), all from small-scale vendors. These findings call for vigilant exercise of good agricultural and hygienic practices by primary producers and retailers.

Microbial Quality and Growth Dynamics in Shameta: A Traditional Ethiopian Cereal-Based Fermented Porridge

Shameta is a traditional, Ethiopian, cereal-based fermented porridge exclusively prepared for lactating mothers. The aim of this study was to determine the microbial quality of Shameta samples collected from households of lactating mothers and to determine microbial dynamics and physicochemical changes during laboratory fermentation of Shameta. Isolation and characterization of the dominant microbes and analysis of the physicochemical properties of samples were done following standard microbiological methods and analytical techniques. Results of this study showed that the highest mean count of lactic acid bacteria (8.33 log cfu/g) was recorded in a sample from laboratory-fermented barley-based Shameta, and the lowest (5.88 log cfu/g) in Shameta made from a mixture of barley and maize (BMS). In both barley-based and maize-based laboratory-prepared Shameta, the microflora were dominated by LAB, followed by yeasts. The dominant LAB were the genus Lactobacillus (74.85%), followed by Enterococcus (15.79%). It could be concluded that Shameta collected from households of lactating mothers are fairly safe for consumption, as the stringent physicochemical conditions of the final product could inhibit the growth of pathogens. However, as Shameta is a traditional fermented porridge fed to lactating mothers, we call for a further improvement to the fermentation process by using defined starter cultures.

Loads of Coliforms and Fecal Coliforms and Characterization of Thermotolerant Escherichia coli in Fresh Raw Milk Cheese

The aim of this study was to assess the hygienic status of raw milk cheese and determine the trends of virulence and antimicrobial resistance in thermotolerant Escherichia coli. Two hundred samples of karish, a popular Egyptian fresh raw milk cheese, were analyzed for coliforms and fecal coliforms using a standard most probable number (MPN) technique. Overall, 85% of samples were unsuitable for consumption, as they exceeded Egyptian standards for coliforms (10 MPN/g), and 65% of samples exhibited coliforms at 44.5 °C. Of 150 recovered thermotolerant strains, 140 (93.3%) were identified as E. coli. Importantly, one Shiga toxin-producing E. coli (STEC) strain carrying a striking virulence pattern, stx1−, stx2+, eae−, was detected. Eleven strains (7.8%, 11/140) showed resistance to third-generation cephalosporins. Antibiotic resistance genes included bla_SHV, bla_CTX-M, qnrS, tet(A), and tet(B), which were present in 4.3%, 2.8%, 0.71%, 2.1%, and 0.71% of isolates, respectively. In conclusion, this study indicated that hygienic-sanitary failures occurred throughout the production process of most retail karish cheese. Furthermore, our findings emphasize the need for adopting third-generation cephalosporin-resistant E. coli as an indicator for monitoring antimicrobial resistance in raw milk cheese to identify the potential public health burden associated with its consumption.

Decoding the roles of extremophilic microbes in the anaerobic environments: Past, Present, and Future

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The inaccessible extreme environments harbor a large majority of anaerobic microbes which remain unknown.

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Anaerobic microbes are used in a variety of industrial applications.

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In the future, metagenomic-assisted techniques can be used to identify novel anaerobic microbes from the unexplored extreme environments.

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Genetic engineering can be used to enhance the efficiency of anaerobic microbes for various processes.

The genome of an organism is directly or indirectly correlated with its environment. Consequently, different microbes have evolved to survive and sustain themselves in a variety of environments, including unusual anaerobic environments. It is believed that their genetic material could have played an important role in the early evolution of their existence in the past. Presently, out of the uncountable number of microbes found in different ecosystems we have been able to discover only one percent of the total communities. A large majority of the microbial populations exists in the most unusual and extreme environments. For instance, many anaerobic bacteria are found in the gastrointestinal tract of humans, soil, and hydrothermal vents. The recent advancements in Metagenomics and Next Generation Sequencing technologies have improved the understanding of their roles in these environments. Presently, anaerobic bacteria are used in various industries associated with biofuels, fermentation, production of enzymes, vaccines, vitamins, and dairy products. This broad applicability brings focus to the significant contribution of their genomes in these functions. Although the anaerobic microbes have become an irreplaceable component of our lives, a major and important section of such anaerobic microbes still remain unexplored. Therefore, it can be said that unlocking the role of the microbial genomes of the anaerobes can be a noteworthy discovery not just for mankind but for the entire biosystem as well.

Why the importance of geo-origin tracing of edible bird nests is arising?

Edible bird's nest (EBN) swiftlet existed naturally 48,000 years ago in caves as their natural dwellings. Nowadays, edible bird's nest has become a very important industry due to its high nutritional, medicinal and economic value. Additionally, edible bird's nest has a long quality guarantee period. Obviously, the nutritional components and medicinal functions vary depending on geographical origins. Recently, the global demand for edible bird's nest has markedly increased, accompanied by the increasing attention of all key players of the global food trade system, i.e., producers, consumers, traders and the authorities to obtain safe and high-quality edible bird's nest. Hence, this target can be accomplished via the enforcement of an efficient and universal geo-tracing technique. Current methods of the geo-tracking of edible bird's nest, i.e., automation, physical and analytical techniques have several limitations and all of them fail to discriminate different quality grades of edible bird's nest. Meanwhile, in many studies and applications, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) has proven to be a "cutting edge" technique for greatly enhance food traceability from field to fork through its ability in distinguishing the food products in terms of their quality and safety. This article provides an overview of (1) edible bird's nest as a multiuse strategic food product, (2) quality issues associated with edible bird's nest including implications that the site of acquisition of the edible bird's nest has food safety implications, (3) current regulations and geo-tracking approaches to ensure the safety and quality of edible bird's nest with the special focus on polymerase chain reaction-denaturing gradient gel electrophoresis technique as a vigorous and universal geo-tracing tool to be suggested for edible bird's nest geo-traceability.

Assessing hygiene indicators in two dairies in Algeria in producing pasteurized milk

Background and Aim:

There is a worldwide controversy about the choice of microbial flora for use as process hygiene indicators. This study aimed to evaluate the pertinence of using either coliforms or Enterobacteriaceae (EB) as process hygiene indicators in the pasteurized milk production line. Two flora families and total flora were used as bacterial indicators in some stages of pasteurized milk production line to identify the origin of post-pasteurization contamination and compare the results obtained for each flora. In addition, the bacteriological profile of isolated coliforms and EB was developed.

Materials and Methods:

One thousand and two hundred samples of pasteurized cow milk and surfaces (pipes and tank) at various processing stages were taken from two dairies in the northern region of Algeria. The total microbial flora (TF), total coliforms (TC), thermotolerant coliforms, and EB were enumerated, following the recommendations of ISO 4833:2006, ISO 4832:2006, and ISO 21528-2:2017 methods, respectively. The bacteriological profile was determined using the API 20E and 10S tests (bioMérieux, France). Furthermore, the cleaning efficiency and disinfection protocol of surfaces were evaluated using contact agar slides 1 (Liofilchem™, Italy).

Results:

Enumeration of the different indicators shows that the highest contamination rate is recorded by the total flora in the two units, 3.28 and 3.78 log CFU/mL, respectively. EB (−0.60 log CFU/mL) at post-pasteurization stage in Unit 1 and coliforms (0.44 log CFU/mL) at the pasteurized packaged milk stage in Unit 2 are the least significant germ families. The lowest compliance rates of bacterial contamination were reported for total flora (82-85%) at the three sampled sites in Unit 2. In comparison, the highest was reported in Unit 1 (99.8%) and 2 (98%) by the EB indicator. Assessing the surface cleaning and disinfection protocol compliance shows that the tank records the highest non-compliance rates for EB and TF (4% and 3%) in Unit 2. EB are represented in both units by various species. Acinetobacter baumannii in Unit 1 and Enterobacter cloacae in Unit 2 are the common species of the three indicator families. Acinetobacter and Enterobacter in Unit 1, Escherichia, Citrobacter, Enterobacter, Klebsiella, and Hafnia in Unit 2 are the most time persistent bacterial genera along the production line. Stenotrophomonas, Serratia, Salmonella, Enterobacter, and Escherichia are common genera in both units.

Conclusion:

The results obtained show no difference in the use of EB or TC as hygiene indicators. However, if the objective is to identify the species of bacterial populations, using EBs are the most appropriate.

Characterization of Bacterial Microbiota of P.D.O. Feta Cheese by 16S Metagenomic Analysis

Background: The identification of bacterial species in fermented PDO (protected designation of origin) cheese is important since they contribute significantly to the final organoleptic properties, the ripening process, the shelf life, the safety and the overall quality of cheese. Methods: Ten commercial PDO feta cheeses from two geographic regions of Greece, Epirus and Thessaly, were analyzed by 16S metagenomic analysis. Results: The biodiversity of all the tested feta cheese samples consisted of five phyla, 17 families, 38 genera and 59 bacterial species. The dominant phylum identified was Firmicutes (49% of the species), followed by Proteobacteria (39% of the species), Bacteroidetes (7% of the species), Actinobacteria (4% of the species) and Tenericutes (1% of the species). Streptococcaceae and Lactobacillaceae were the most abundant families, in which starter cultures of lactic acid bacteria (LAB) belonged, but also 21 nonstarter lactic acid bacteria (NSLAB) were identified. Both geographical areas showed a distinctive microbiota fingerprint, which was ultimately overlapped by the application of starter cultures. In the rare biosphere of the feta cheese, Zobellella taiwanensis and Vibrio diazotrophicus, two Gram-negative bacteria which were not previously reported in dairy samples, were identified. Conclusions: The application of high-throughput DNA sequencing may provide a detailed microbial profile of commercial feta cheese produced with pasteurized milk.

Biological Indicators for Fecal Pollution Detection and Source Tracking: A Review

Fecal pollution, commonly detected in untreated or less treated sewage, is associated with health risks (e.g., waterborne diseases and antibiotic resistance dissemination), ecological issues (e.g., release of harmful gases in fecal sludge composting, proliferative bacterial/algal growth due to high nutrient loads) and economy losses (e.g., reduced aqua farm harvesting). Therefore, the discharge of untreated domestic sewage to the environment and its agricultural reuse are growing concerns. The goals of fecal pollution detection include fecal waste source tracking and identifying the presence of pathogens, therefore assessing potential health risks. This review summarizes available biological fecal indicators focusing on host specificity, degree of association with fecal pollution, environmental persistence, and quantification methods in fecal pollution assessment. The development of practical tools is a crucial requirement for the implementation of mitigation strategies that may help confine the types of host-specific pathogens and determine the source control point, such as sourcing fecal wastes from point sources and nonpoint sources. Emerging multidisciplinary bacterial enumeration platforms are also discussed, including individual working mechanisms, applications, advantages, and limitations.

Probabilistic modelling of Escherichia coli concentration in raw milk under hot weather conditions

Climate change is one of the threats to the dairy supply chain as it may affect the microbiological quality of raw milk. In this context, a probabilistic model was developed to quantify the concentration of Escherichia coli in raw milk and explore what may happen to France under climate change conditions. It included four modules: initial contamination, packaging, retailing, and consumer refrigeration. The model was built in R using the 2nd order Monte Carlo mc2d package to propagate the uncertainty and analysed its impact independently of the variability. The initial microbial counts were obtained from a dairy farm located in Saudi Arabia to reflect the impact of hot weather conditions. This country was taken as representative of what might happen in Europe and therefore in France in the future due to climate change. A large dataset containing 622 data points was analysed. They were fitted by a Normal probability distribution using the fitdistrplus package. The microbial growth was determined across various scenarios of time and temperature storage reflecting the raw milk supply-chain in France. Existing growth rate data from literature and ComBase were analysed by the Ratkowsky secondary model. Results were interpreted using the nlstools package. The mean E. coli initial concentration in raw milk was estimated to be 1.31 [1.27; 1.35] log CFU/ mL and was found to increase at the end of the supply chain as a function of various time and temperature conditions. The estimations varied from 1.73 [1.42; 2.28] log CFU/mL after 12 h, 2.11 [1.46; 3.22] log CFU/mL after 36 h, and 2.41 [1.69;3.86] log CFU/mL after 60 h of consumer storage. The number of milk packages exceeding the 2-log French hygiene criterion for E. coli increased from 10% [8;12%] to 53% [27;77%] during consumer storage. In addition, the most significant factors contributing to the uncertainty of the model outputs were identified by running a sensitivity analysis. The results showed that the uncertainty around the Ratkowsky model parameters contributed the most to the uncertainty of E. coli concentration estimates. Overall, the model and its outputs provide an insight on the possible microbial raw milk quality in the future in France due to higher temperatures conditions driven by climate change.

Antibiotic resistance profile and detection of degradative enzymes by Enterobacteriaceae isolated from raw goat milk

Introduction

Enterobacteriaceae are often reported as a typical bacterial population in raw milk from any mammalian origin. The frequent concern with bacteria, especially those related to this group of microorganisms, is their increasing resistance to antibiotics and the emergence of enzymes that degrade them. This study aimed to characterize isolates of Enterobacteriaceae from raw goat milk to expose associated safety problems and possible technological challenges.

Methods

Isolates from 21 raw goat milk samples purchased in the State of Rio de Janeiro, Brazil, were identified by mass spectrometry, after isolation on Violet Red Bile Glucose agar. The isolates were subjected to evaluation of proteolytic, lipolytic, hemolytic, and biofilm producing activities. Furthermore, resistance profiles and production capacity of enzymes that degrade antimicrobials were evaluated.

Results

Almost half of the 59 isolates (48%) belonged to the Enterobacter genus, with a significant prevalence of the Serratia (20%) and Klebsiella (11%) genera. The majority showed biofilm-producing activity (90%), while the activity of degradative enzymes was observed in approximately 20%. Few isolates were found with a profile of resistance to antimicrobials, with only one isolate of Klebsiella variicola being classified as multidrug-resistant. However, chromogenic culture media showed high production of extended-spectrum beta-lactamases and carbapenemases (54% and 46%, respectively), as a presumptive identification.

Conclusions

A considerable degree of virulence was observed in the Enterobacteriaceae isolates, as well as the potential for undesirable technological damage. The characterization and identification of the isolates contributes to the improvement of the risk monitoring process of goat's milk.

A Food-Grade Resin with LDH–Salicylate to Extend Mozzarella Cheese Shelf Life

Mozzarella cheese can be considered by far the world’s most popular Italian dairy product. Extending the shelf life of mozzarella cheese is an important issue in the dairy industry due to the high risk of contamination by several bacteria species, including spoilage pseudomonads. In this work, active packaging was prepared by coating traditional polyethylene terephthalate (PET) containers of “ovoline” mozzarella cheese with a food-grade resin mixed with a layered double hydroxide (LDH) in which salicylate anion was intercalatedby ionic exchange.. This antimicrobial molecule is listed in EC-Directive 10/2011/EC of 14 January 2011. Morphological arrangement of the molecule into the LDH layers was evaluated by X-ray diffraction (XRD) and controlled release followed by UV spectroscopy. Then, active trays were used to pack the mozzarella cheeses stored for 20 days at 4 °C and under thermal abuse (15 °C). Samples from both conditions showed coliform reduction (by ca. 2 log CFU/g) throughout the storage period. Depending on temperature, total mesophilic aerobic bacteria, Pseudomonas spp., yeasts, and mold loads were reduced in the first 3 days; at 4 °C. Slower acidification and lower proteolysis were also found in treated samples in comparison to control ones. The fitting of the Gompertz function to coliforms and spoilage pseudomonads highlighted an increase in the shelf life of mozzarella cheese of ca. 2 days at 4 °C. These results suggest that salicylate–LDH-coated PET may be applied to extend the shelf-life of mozzarella cheese and also counteract its spoilage if accidental interruptions to refrigeration occur.

Population dynamics of coliforms in a commercial Cheddar cheese production facility

The detection of coliforms in young cheese is a potential indication of undesirable microbial growth within the processing environment. The aim of this study was to investigate sources and conditions that lead to the intermittent detection of coliforms (1-3 log cfu/g) in young Cheddar cheese at a single commercial facility. Analysis of historical production data, in combination with iterative investigative sampling events, was performed to determine coliform levels in milk, whey, curd, and surfaces at the beginning, middle, and end of the production day. After sanitation, conveyor belt pieces from the draining and matting conveyor (DMC) were collected and evaluated for bacterial survivors using culture-based methods and scanning electron microscopy. Production data analysis indicated that cheese produced later in the production day (≥16 h) was significantly more likely to test positive for coliforms than cheese made earlier in the production day (<12 h). Enumeration of coliforms in raw and heat-treated milk demonstrated that the subpasteurization thermal treatment (67-70°C, 26-28 s) was effective at reducing, but not eliminating, coliforms. Repeated sampling identified the DMC, particularly the drain belt and belt 1, as a critical area that supported coliform growth during the production day. Coliform levels in whey entering the weir maintained a level of <1 cfu/mL throughout production; however, coliform levels in whey below the drain belt increased from <1 cfu/mL at midday (8 h) to 5.04 log cfu/mL by the end of the production day (~18 h). Routine sanitation inside the DMC resulted in undetectable coliform levels on easily accessible surfaces. However, enrichment and scanning electron microscopy of belt sections revealed pockets of viable coliforms and other bacteria in cracks and defects in conveyor belts, indicating that sanitation did not eliminate all viable bacteria. Low levels of coliforms are present in heat-treated milk and survive sanitation in the DMC and could serve as the initial seed for high levels of coliforms at the end of the production day.

Potential Residual Contaminants in Edible Bird's Nest

Edible bird’s nest (EBN) is recognized as a nourishing food among Chinese people. The efficacy of EBN was stated in the records of traditional Chinese medicine and its activities have been reported in many researches. Malaysia is the second largest exporter of EBNs in the world, after Indonesia. For many years, EBN trade to China was not regulated until August 2011, when a safety alert was triggered for the consumption of EBNs. China banned the import of EBNs from Malaysia and Indonesia due to high level of nitrite. Since then, the Malaysia government has formulated Malaysia Standards for swiftlet farming (MS 2273:2012), edible bird’s nest processing plant design and management (MS 2333:2010), and edible bird’s nest product quality (MS 2334:2011) to enable the industry to meet the specified standards for the export to China. On the other hand, Indonesia's EBN industry formulated a standard operating procedure (SOP) for exportation to China. Both countries can export EBNs to China by complying with the standards and SOPs. EBN contaminants may include but not limited to nitrite, heavy metals, excessive minerals, fungi, bacteria, and mites. The possible source of contaminants may come from the swiftlet farms and the swiftlets or introduced during processing, storage, and transportation of EBNs, or adulterants. Swiftlet house design and management, and EBN processing affect the bird’s nest color. Degradation of its optical quality has an impact on the selling price, and color changes are tied together with nitrite level. In this review, the current and future prospects of EBNs in Malaysia and Indonesia in terms of their quality, and the research on the contaminants and their effects on EBN color changes are discussed.

Microbial ecology of alfalfa, radish, and rapeseed sprouts based on culture methods and 16S rRNA microbiome sequencing

Sprouts harbor high populations of bacteria and cause numerous foodborne disease outbreaks, yet little is known about their microbial composition. The present study aimed to define the microbiological ecology of sprouts using 16S rRNA microbiome sequencing and culture-dependent methods. Different types (radish, alfalfa, and rapeseed), brands (A, B, and C), and distribution routes (online and offline) of sprouts (n = 70) were considered for microbiome analysis, as well as quantitative (aerobic plate count and coliforms) and qualitative analyses (Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium). The aerobic plate count ranged from 7 to 8 CFU/g, and the coliforms ranged from 6 to 7 log CFU/g. Microbiome analysis revealed that Proteobacteria was the dominant phylum, accounting for 79.0% in alfalfa sprouts, 68.5% in rapeseed sprouts, and 61.9% in radish sprouts. Enterobacteriaceae was the dominant family in alfalfa sprouts (33.9%) and rapeseed sprouts (14.6%), while Moraxellaceae (11.9%) were prevalent on radish sprouts. The majority of the dominant genera were common in the environment, such as soil or water. Alfalfa sprouts yielded the lowest aerobic plate count but the highest relative abundance of Enterobacteriaceae compared to the other sprouts. These results could explain why alfalfa sprouts are a leading cause of sprout-related foodborne disease outbreaks. Alpha-diversity results (Chao1 and Shannon indices) suggested that species richness was greater on radish sprouts than the other sprout types. Beta-diversity results showed samples were clustered by types, indicating dissimilarity in microbial communities. However, the distribution route had a limited influence on microbial composition. The present study provides a comparative examination of the microbial profiles of sprouts. Microbiome analyses contribute to an in-depth understanding of the microbial ecology of sprouts, leading to potential control measures for ensuring food safety.

The Cheese Production Facility Microbiome Exhibits Temporal and Spatial Variability

A primary goal of modern cheese manufacturing is consistent product quality. One aspect of product quality that remains poorly understood is the variability of microbial subpopulations due to temporal or facility changes within cheese production environments. Therefore, our aim was to quantify this variability by measuring day-day and facility-facility changes in the cheese facility microbiome. In-process product (i.e., milk and cheese) and food-contact surfaces were sampled over the course of three production days at three cheese manufacturing facilities. Microbial communities were characterized using 16S rRNA metabarcoding and by plating on selective growth media. Each facility produced near-identical Cheddar cheese recipes on near-identical processing equipment during the time of sampling. Each facility also used a common pool of Lactococcus starter cultures which were rotated daily as groups of 4-5 strains and selected independently at each facility. Diversity analysis revealed significant facility-facility and day-day differences at each sample location. Facility differences were greatest on the food contact surfaces (i.e., draining-matting conveyor belts), explaining between 25 and 41% of the variance. Conversely, daily differences within each facility explained a greater proportion of the variance in the milk (20% vs. 12%) and cheese (29% vs. 20%). Further investigation into the sources of these differences revealed the involvement of several industrially relevant bacteria, including lactobacilli, which play a central role in flavor and texture development during Cheddar cheese ripening. Additionally, Streptococcus was found to contribute notably to differences observed in milk samples, whereas Acinetobacter, Streptococcus, Lactococcus, Exiguobacterium, and Enterobacteriaceae contributed notably to differences on the food contact surfaces. Facility differences in the cheese were overwhelmingly attributed to the rotation of Lactococcus starter cultures, thus highlighting circumstances where daily microbial shifts could be misinterpreted and emphasizing the importance of repeated sampling over time. The outcomes of this work highlight the complexity of the cheese facility microbiome and demonstrate daily and facility-facility microbial variations which might impact cheese product quality.

Use of Starter Cultures in Foods from Animal Origin to Improve Their Safety

Starter cultures can be defined as preparations with a large number of cells that include a single type or a mixture of two or more microorganisms that are added to foods in order to take advantage of the compounds or products derived from their metabolism or enzymatic activity. In foods from animal origin, starter cultures are widely used in the dairy industry for cheese, yogurt and other fermented dairy products, in the meat industry, mainly for sausage manufacture, and in the fishery industry for fermented fish products. Usually, microorganisms selected as starter culture are isolated from the native microbiota of traditional products since they are well adapted to the environmental conditions of food processing and are responsible to confer specific appearance, texture, aroma and flavour characteristics. The main function of starter cultures used in food from animal origin, mainly represented by lactic acid bacteria, consists in the rapid production of lactic acid, which causes a reduction in pH, inhibiting the growth of pathogenic and spoilage microorganisms, increasing the shelf-life of fermented foods. Also, production of other metabolites (e.g., lactic acid, acetic acid, propionic acid, benzoic acid, hydrogen peroxide or bacteriocins) improves the safety of foods. Since starter cultures have become the predominant microbiota, it allows food processors to control the fermentation processes, excluding the undesirable flora and decreasing hygienic and manufacturing risks due to deficiencies of microbial origin. Also, stater cultures play an important role in the chemical safety of fermented foods by reduction of biogenic amine and polycyclic aromatic hydrocarbons contents. The present review discusses how starter cultures contribute to improve the microbiological and chemical safety in products of animal origin, namely meat, dairy and fishery products.

Cluster analysis of resistance combinations in Escherichia coli from different human and animal populations in Germany 2014-2017

Recent findings on Antibiotic Resistance (AR) have brought renewed attention to the comparison of data on AR from human and animal sectors. This is however a major challenge since the data is not harmonized. This study performs a comparative analysis of data on resistance combinations in Escherichia coli (E. coli) from different routine surveillance and monitoring systems for human and different animal populations in Germany. Data on E. coli isolates were collected between 2014 and 2017 from human clinical isolates, non-clinical animal isolates from food-producing animals and food, and clinical animal isolates from food-producing and companion animals from national routine surveillance and monitoring for AR in Germany. Sixteen possible resistance combinations to four antibiotics—ampicillin, cefotaxime, ciprofloxacin and gentamicin–for these populations were used for hierarchical clustering (Euclidian and average distance). All analyses were performed with the software R 3.5.1 (Rstudio 1.1.442). Data of 333,496 E. coli isolates and forty-one different human and animal populations were included in the cluster analysis. Three main clusters were detected. Within these three clusters, all human populations (intensive care unit (ICU), general ward and outpatient care) showed similar relative frequencies of the resistance combinations and clustered together. They demonstrated similarities with clinical isolates from different animal populations and most isolates from pigs from both non-clinical and clinical isolates. Isolates from healthy poultry demonstrated similarities in relative frequencies of resistance combinations and clustered together. However, they clustered separately from the human isolates. All isolates from different animal populations with low relative frequencies of resistance combinations clustered together. They also clustered separately from the human populations. Cluster analysis has been able to demonstrate the linkage among human isolates and isolates from various animal populations based on the resistance combinations. Further analyses based on these findings might support a better one-health approach for AR in Germany.

Microbiological quality and safety of Brazilian artisanal cheeses

The establishment of norms that regulates the production and trade of Brazilian Artisanal Cheeses (BAC) has been stimulating many small farmers for this activity. The predominance of lactic acid bacteria (LAB) is a typical characteristic of BAC, which confers desirable attributes to artisanal cheeses. However, these products can be contaminated by other microbial groups, including those that indicate hygienic failures during production and may cause spoilage, or even microorganisms that pose risks to consumers' health. A systematic review of the literature published from January 1996 to November 2020 was carried out to identify scientific data about production characteristics and microbiological aspects of BAC, with a major focus on quality and safety status of these traditional products. Studies that fulfilled the inclusion criteria indicated that artisanal chesses produced in Brazil still do not satisfactorily meet the microbiological criteria established by the national laws, mainly due to the high counts of coagulase-positive Staphylococcus and coliforms. Despite low prevalence, pathogens such as Salmonella and Listeria monocytogenes were isolated in some BAC. This review contributed to better understanding microbiological aspects of BAC, the data compiled by the authors highlight the need to improve hygiene practices along the production chain of these traditional cheeses.

Spoilage potential of Bacillus subtilis in a neutral-pH dairy dessert

The objective of this study was the characterization of the microbiota associated with spoilage of vanilla cream pudding during storage at different temperatures. Commercial cream samples were stored aerobically at 4, 8, 12 and 15 °C for a maximum time period of 40 days. At appropriate time intervals, cream samples were subjected to: (i) microbiological analyses, and (ii) high-performance liquid chromatography (HPLC). Furthermore, the spoilage microbiota was identified through repetitive extragenic palindrome-PCR, while selected isolates were further characterized based on sequencing of the V1-V3 region of the 16S rRNA gene. Microbial growth was observed only during storage of cream samples at 12 and 15 °C, with the applied genotypic analysis demonstrating that Bacillus subtilis subsp. subtilis was the dominant spoilage microorganism of this product. Based on the HPLC analysis results, citric acid and sucrose were the most abundant organic acid and sugar, respectively throughout storage of cream pudding, whereas notable changes mainly included: (i) increase in the concentration of lactic acid and to a lesser extent of formic and acetic acids, and (ii) increase in the concentration of glucose and fructose at the expense of sucrose and lactose. The results of this study should be useful for the dairy industry in detecting and controlling microbiological spoilage in cream pudding and other chilled, neutral-pH dairy desserts.

An updated review on bacterial community composition of traditional fermented milk products: what next-generation sequencing has revealed so far?

The emergence of next-generation sequencing (NGS) technologies has revolutionized the way to investigate the microbial diversity in traditional fermentations. In the field of food microbial ecology, different NGS platforms have been used for community analysis, including 454 pyrosequencing from Roche, Illumina's instruments and Thermo Fisher's SOLiD/Ion Torrent sequencers. These recent platforms generate information about millions of rDNA amplicons in a single running, enabling accurate phylogenetic resolution of microbial taxa. This review provides a comprehensive overview of the application of NGS for microbiome analysis of traditional fermented milk products worldwide. Fermented milk products covered in this review include kefir, buttermilk, koumiss, dahi, kurut, airag, tarag, khoormog, lait caillé, and suero costeño. Lactobacillus-mainly represented by Lb. helveticus, Lb. kefiranofaciens, and Lb. delbrueckii-is the most important and frequent genus with 51 reported species. In general, dominant species detected by culturing were also identified by NGS. However, NGS studies have revealed a more complex bacterial diversity, with estimated 400-600 operational taxonomic units, comprising uncultivable microorganisms, sub-dominant populations, and late-growing species. This review explores the importance of these discoveries and address related topics on workflow, NGS platforms, and knowledge bioinformatics devoted to fermented milk products. The knowledge that has been gained is vital in improving the monitoring, manipulation, and safety of these traditional fermented foods.

Utility of rapid tests to assess the prevalence of indicator organisms (Aerobic plate count, Enterobacteriaceae, coliforms, Escherichia coli, and Listeria spp.) in apple packinghouses

The 2014 listeriosis outbreak caused by caramel-coated apples was linked to apples cross-contaminated within an apple packing facility. This outbreak has increased the focus on effective cleaning and sanitation methods that must be validated and monitored during apple packing. Thus, rapid and reliable testing methods are necessary for assessing cleanliness in the apple packing industry. The objectives of this study were to assess the prevalence of common indicator organisms [Aerobic plate count (APC), Enterobacteriaceae, coliforms, Escherichia coli, and Listeria spp.] on food contact surfaces (zone 1) in apple packinghouses and to evaluate the utility and accuracy of currently used rapid tests (ATP and glucose/lactose residue swabs). Food contact surfaces were sampled over a 100 cm² area in five commercial apple packinghouses to evaluate populations of indicator organisms APC, Enterobacteriaceae, coliforms, E. coli (n = 741), and rapid test readings (n = 659). Petrifilm plates were used for the quantification of APC, Enterobacteriaceae, and coliform/E. coli. Rapid tests [ATP swabs (UltraSnap) and glucose/lactose residue swabs (SpotCheck Plus)] were processed on-site. A larger area (0.93 m²) was sampled for the detection of Listeria spp. (n = 747), following a modified protocol of the FDA's Bacteriological Analytical Manual method, and confirmed with PCR and gel electrophoresis via the iap gene. No significant association was found between either rapid test and populations of APC, Enterobacteriaceae, coliforms, E. coli, and Listeria spp. detection. However, recovery of APC (log CFU/100 cm²) was higher with a failed glucose/lactose residue swab surface hygiene result (3.1) than a passed result (2.9) (p = 0.03). Populations of APC, Enterobacteriaceae, and coliforms were significantly different at each unit operation during the packing process (p ≤ 0.05). This study concluded that ATP and glucose/lactose residue rapid tests were poorly suited for determining microbial load since they were not related to populations of any common indicator organisms or the detection of Listeria spp. These findings emphasize the need to utilize a rapid test, which can be a good indicator of residual matter on a surface, along with traditional microbiological methods to assess cleaning and sanitation practices in apple packinghouses.

Isolation of enterotoxigenic Staphylococcus aureus harboring seb gene and enteropathogenic Escherichia coli (serogroups O18, O114, and O125) from soft and hard artisanal cheeses in Egypt

Background:

Soft and hard artisanal cheeses are regularly consumed in Egypt. These products are usually processed from raw milk which may harbor many pathogenic and spoilage microorganisms.

Aim:

To evaluate the safety of some artisanal cheeses in Egypt, such as Ras, Domiati, and Mish, through chemical and microbiological examination.

Methods:

One hundred and fifty random samples of traditional Ras, Domiati, and Mish cheeses (50 each) were microbiologically and chemically analyzed. Counts of total bacteria, presumptive coliform, staphylococci, yeast, and mold were estimated. Furthermore, isolation of Escherichia coli and Staphylococcus aureus was performed, followed by PCR confirmation; isolates of E. coli were examined for the presence of virulence genes; on the other hand, the detection of the five classical enterotoxin genes of S. aureus was performed using multiplex PCR. Regarding chemical analysis, moisture, salt, and acidity content were measured. Correlations between chemical and microbial findings were investigated.

Results:

Mean counts of total bacteria, presumptive coliform, staphylococci, yeast, and mold were (2 × 10⁸, 3 × 10⁶ and 1 × 10⁷ ), (3 × 10⁵, 5 × 10 and 5 × 10²), (1 × 10⁶, 4 × 10⁵and 1 × 10⁵), (3 × 10⁵, 1 × 10⁵ and 5 × 10⁵), and (7 × 10³, 4 × 10³ and 3 × 10⁴) for Ras, Domiati and Mish cheeses, respectively. Serological identification of suspected E. coli revealed that E. coli O125 was isolated from Ras and Domiati samples, E. coli O18 was recovered from Ras samples, while E. coli O114 was isolated from Mish samples. PCR results revealed that all detected isolates of E. coli were positive for both iss (increased serum survival) and fimH (type 1 fimbriae) genes. Concerning isolated S. aureus, all examined products were harboring S. aureus enterotoxigenic strains, with seb and sed genes being the most common. The mean values of moisture, salt, and acidity were (30.03, 56.44, and 58.70), (3.30, 6.63, and 7.56) and (0.65, 0.68, and 0.50) for Ras, Domiati, and Mish cheeses, respectively.

Conclusion:

Enterotoxigenic S. aureus harboring seb gene and enteropathogenic E. coli (serogroups O18, O114, and O125) were frequently isolated from soft and hard artisanal cheeses in Egypt. Therefore, strict hygienic measures should be applied during their manufacture, handing, and distribution.