Antibiotic susceptibility profiles of ropy slime-producing Leuconostoc mesenteroides isolated from cooked meat products

The transfer of antibiotic resistance via the food chain is a global concern. Nevertheless, more attention is required to non-pathogenic strains, such as spoilage bacteria, which could transmit genes to pathogens. Although Lactic Acid Bacteria are microorganisms generally recognized as safe, Leuconostoc mesenteroides may reach and maintain high concentration levels on the surface of cooked products and ready-to-eat products throughout the entire shelf life. It is therefore important to consider the possibility for this species to carry antibiotic- resistance genes. The present research deals with the antibiotic susceptibility profile of strains of L. mesenteroides, isolated from vacuum packaged cooked meat products. In this study, the antimicrobial susceptibility of L.mesenteroides, previously isolated from cooked ham, was investigated through disk diffusion assay according to CLSI standards. Isolated strains from ready-to-eat food show high levels of resistance to ampicillin and methicillin and, according to a settled panel of 21 antibiotics, the antibiotic resistance was demonstrated for the 50% of the tested molecules

Enterotoxin production by Staphylococcus aureus isolated from mastitic cows.

Staphylococcus aureus is an important cause of mastitis in cows. The ability of S. aureus strains to produce one or more enterotoxins in milk and dairy products is linked to staphylococcal food poisoning. To determine whether staphylococci causing bovine mastitis could cause human foodborne intoxication, the production of staphylococcal enterotoxins A through D (SEA, SEB, SEC, and SED) by 160 S. aureus isolates was evaluated with the use of a reverse passive latex agglutination enterotoxin kit. All S. aureus strains were isolated over a 9-month period from 2,343 routine submissions of a composite quarter collection of individual mastitic cows at 18 dairy farms in the San Joaquin Valley in California. Prior to enterotoxin detection, isolates were grown by a method that enhances the in vitro synthesis of enterotoxin. Twenty-two of 160 S. aureus isolates produced enterotoxin. Seven produced SEC, 12 produced SED, and 3 produced both SEC and SED. None of the isolates produced SEA or SEB

Is EU regulation on the use of antioxidants in meat preparation and in meat products still cutting edge?

The use of antioxidants in meat preparation and meat products is highly debated. Regulations define the use of antioxidants mostly in terms of the age-old subdivision between meat preparations and meat products. Best practices are not well represented in regulations. Antioxidants for foodstuffs during processing or before packing protect colour, aroma and nutrient content. As regards food safety regulations, long-term efforts have been made in terms of food standards, food control systems, food legislation and regulatory approaches. These have, however, generated several questions on how to apply the law to diverse food businesses. To answer these questions, a thorough examination of the EU legislator’s choices for food additives and definitions is provided and discussed in relation to factors affecting microbial growth. The paper highlights the regulatory aspects along with the correct application and interpretation of the norms.https://link.springer.com/journal/2172021-01-07hj2020Paraclinical Science

Seroepidemiological study of Johne's-disease in diary cattle in Umbria, Italy

A total of 788 serum samples from dairy cattle in Umbria, Italy, were tested for the presence of antibodies to Mycobacterium avium subspecies paratuberculosis (Map) using a commercial enzyme-linked immunosorbent assay (ELISA) kit. The sampled animals came from 19 herds representative of the central area of the Umbria county (Perugia and Assisi districts). Using the manufacturer suggested cut-off for a positive test, 44 animals (5.6%) were positive. Using the sensitivity and specificity claimed by the manufacturer of the ELISA kit, the true prevalence in Umbria dairy cattle overall was calculated as 9.7% (99% CI, 7.0%, 12.4%).Grants from the Ministry of Foreign Affairs (MAE), Directorate General for Cultural Promotion and Cooperation, Italy, Executive programme of scientific and technological co-operation between the Italian Republic and the Republic of South Africa 2007-2010.http://www.aspajournal.it/index.php/ijas/indexam201

Effects of UV irradiation in a continuous turbulent flow UV reactor on microbiological and sensory characteristics of cow's milk.

The dairy industry under current pasteurization conditions (15 s at 72°C) and sanitary standards achieves a safe product with excellent quality. In an ever-competitive market there is still a need to improve product quality and extend shelf life of dairy products to increase competitiveness and open up new markets. In an attempt to test the effect of UV irradiation on microbiota of fluid milk, a continuous flow UV system at 254 nm was used to treat 3.5 and 2% fat milk at two UV doses (880 and 1,760 J liter(-1)). Milk was obtained from three processors, and two lots from each processor were assessed. To assess the impact on the most descriptive native microbiota in pasteurized milk after UV illumination, the product was held at two storage temperatures (4 and 7°C) and tested weekly for 5 weeks for aerobic plate counts (psychrotrophic and mesophilic bacteria), laboratory pasteurization counts, aerobic sporeformers, coliform organisms, and titratable acidity. Microbial counts for all tested microorganisms were lower in UV-treated milk when compared with control throughout storage at 4 and 7°C in both 3.5 and 2% fat milk. Sensory analysis indicated that there is a sensory defect associated with UV treatment at the wavelength used

Determining food stability to achieve food security

Food security, as part as public health protection, constitutes one of the main objectives for countries aiming to ensure the health of all their citizens. However, food security is compromised worldwide by conflict, political instability, or economic crises, both in developed and developing countries. Conversely, because of the importance of agriculture to the economies of rural areas both in developed and developing countries, this sector can contribute to improving food stability, as well as to furthering food security. Thus, livestock and traditional meat products represent a key factor in ensuring food availability. Overall, biosecurity measures improve animal welfare by decreasing the occurrence of diseases that compromise the stability by causing fluctuations in the availability of meat and animal-derived food products such as milk, eggs, or traditional fermented products. As a consequence, an absence of biosecurity measures affects food security (in its quantitative definition, as described above) as well as the productive, sanitary, and environmental sustainability of the rural environment. Products of animal origin support local trade and the regional economy, while contributing to the availability of foods without great external dependence. The manufacture of foods of animal origin aims to create products that are durable and that maintain food availability for long periods of time, even during seasons with scarce resources. Thus, dry-cured or fermented meat products play an important role in food availability. Food security also refers to food access under healthy economic conditions; therefore, knowledge of the main tools that guarantee the safety of these kinds of food products is essential to achieving food stability and further food securityThe Fundação para a Ciência e Tecnologia (FCT)https://www.mdpi.com/journal/sustainabilitydm2022Paraclinical Science

Evolution under different storage conditions of anomalous blue coloration of Mozzarella cheese intentionally contaminated with a pigment-producing strain of Pseudomonas fluorescens

Several widespread occurrences of anomalous blue coloration of Mozzarella cheese have been recorded in the United States and some European countries. Official laboratory analysis and health authorities have linked the occurrences to contamination of the processing water with strains of Pseudomonas fluorescens, although several experts questioned how to unequivocally link the blue color to the presence of the microorganism. To establish a method to determine whether a given Pseudomonas spp. strain is responsible for the defect and study the evolution of the coloration under different storage conditions, we developed an in vitro system for the evaluation of blue coloration of Mozzarella cheese intentionally contaminated with strains of P. fluorescens. The purpose of the system was to determine whether P.fluorescens strains, isolated from Mozzarella cheese with anomalous blue coloration, were able to reproduce the blue coloration under controlled experimental conditions. Thirty-six trials of experimental inoculation of Mozzarella cheese in different preservation liquids were conducted using various suspensions of P.fluorescens (P. fluorescens ATCC 13525, P.fluorescens CFBP 3150, and P. fluorescens 349 field strain isolated from blue-colored Mozzarella cheese) at different concentrations and incubated at different temperatures. Growth curves of all tested P.fluorescens strains demonstrated that after 3 d of incubation the concentration was generally >106 cfu/g of Mozzarella cheese incubated in either tryptic soy broth (control) or conditioning brine. Prolonged incubation for 5 d at either 20°C or 8°C led to concentrations up to 109 cfu/g of Mozzarella cheese incubated in tryptic soy broth and up to 108 cfu/g of Mozzarella cheese incubated in preservation liquid. All Mozzarella cheeses inoculated with the field strain of P. fluorescens, except those opened 1 h after packaging and stored at 8°C, showed the characteristic anomalous blue coloration, which appeared from 1 to 72 h after opening the packaging, and was proportional to colony count, duration of storage, and storage temperature. With the proposed system, which enabled a larger number of samples to be analyzed under controlled experimental conditions and a large amount of data to be generated in a short time, we described precisely how and under which conditions the presence of P. fluorescens in Mozzarella cheese is responsible for the anomalous blue coloration. The system will help producers intercept contaminated batches and help consumers avoid the conditions under which the defect can appear.Grants from Fondazione Cassa di Risparmio di Perugia (Italy) and from the Ministero degli Affari Esteri, Direzione Generale per la Promozione e Cooperazione Culturale (Rome, Italy),http://www.journals.elsevier.com/journal-of-dairy-sciencehb2017Paraclinical Science

Effect of culling management practices on the seroprevalence of Johne’s disease in Holstein dairy cattle in central Italy

A study was performed in Umbria, central Italy, to find out whether different culling strategies adopted by farms to control Johne’s disease (JD) infection exerted effects on the seroprevalence in dairy cattle. Fifty Fresian dairy herds in the Perugia and Assisi districts were visited and an audit of herd management was conducted. Among the 50 herds, 20 were selected for the consistency of management practices and, according to the culling strategy, two groups were created: group A (aggressive culling protocol, with average herd productive life <1100 days) and group B (lower culling rate, with productive life greater than 1500 days). The presence of antibodies to Mycobacterium avium subspecies paratuberculosis (Map) in the serum was determined using a commercial enzyme-linked immunosorbent assay (ELISA) kit. It was found that 3.3% (n = 14) of the cows of group B (n = 422, from 17 herds) were positive for Map antibodies, in comparison with 5.7% (n = 21) of the cows from group A (n = 366, from three herds). The odds ratio from multiple logistic regression (adjusted odds ratio 2.446, 95% confidence interval 0.412 to 14.525) showed that Johne’s disease prevalence in herds with a greater productive life was not higher than in herds with typical modern management characterized by more aggressive culling. This is a significant finding, indicating that aggressive culling may not be necessary. Current JD control recommendations are derived from data obtained in high-prevalence paratuberculosis areas (northern Europe, including northern Italy), while methods of information transfer to dairy farms in low-prevalence areas should be reassessed to ensure that the correct measures, including basic calving management and calf-rearing practices, are thoroughly implemented. Using the manufacturer’s suggested cut-off for a positive ELISA test and the sensitivity and specificity claimed, the overall true prevalence in Umbria dairy cattle was calculated as 7% (95% confidence interval 5.2% to 8.8%).European Food Safety Authority (EFSA)https://www.mdpi.com/journal/vetsciam2023Paraclinical Science

An in vitro system for the comparison of excision and wet-dry swabbing for microbiological sampling of beef carcasses.

An in vitro system for the comparison of wet-dry swabbing and surface tissue excision was developed to ascertain whether the commonly accepted statement of the advantage (in terms of bacterial recovery) of the tissue excision method is also legitimate when different kinds of bacteria are used. A total of 1,770 sections (2.5 by 10 cm) of bovine skin were individually inoculated on the subcutaneous fat side by spreading various suspensions of marker organisms (nalidixic acid-resistant Escherichia coli, vancomycin-resistant Enterococcus faecalis, and methicillin-resistant Staphylococcus aureus) at different concentrations and sampled by two standard methods: cotton wet-dry swabbing and excision. Most counts from cuts sampled by excision were significantly (P < 0.05) higher than the wet-dry swabs; however, no differences were observed between the control and the sampling method when sections were inoculated with bacterial solutions at a concentration of 10(3) CFU/ml and sampled by excision. For sections inoculated with bacterial solutions at a concentration of 10(3) CFU/ml, counts given as log CFU/25 cm2 ranged from 1.97 (S. aureus sampled by wet-dry swab) to 3.06 (S. aureus sampled by excision). For sections inoculated at a concentration of 10(4), counts given as log CFU/25 cm(2) ranged from 2.15 (E. faecalis sampled by wet-dry swab) to 3.19 (S. aureus sampled by excision). For sections inoculated at 10(5), counts given as log CFU/25 cm(2) ranged from 2.94 (E. faecalis, wet-dry swab) to 3.98 (S. aureus, excision), and for sections inoculated at 106, counts given as log CFU/25 cm(2) ranged from 3.53 (E. coli, wet-dry swab) to 4.69 (S. aureus, excision). The proposed system, which enabled a considerable amount of samples to be analyzed under controlled experimental conditions and a large number of data to be generated in a short time, demonstrated among the tested microorganisms that whereas the excision method recovered the highest number of bacteria, control means were always (with the exception of an inoculum of 10(3)/ml) significantly higher than means from either of the sampling methods. Our results indicate that particular attention should be paid to the diverse microflora that can contaminate carcasses in a given slaughterhouse and that it is not appropriate to generalize by saying that the destructive method is the reference technique for the bacteriological sampling of carcasses in slaughterhouses, especially when the contamination is higher than 10(3) CFU/25 cm(2)