Raw Goat Cheese Research Articles

Development of a cell culture-based method for detecting infectious tick-borne encephalitis virus (TBEV) in milk products

Tick-borne encephalitis outbreaks have been reported in Europe after consumption of raw milk products from infected animals. While molecular methods are commonly used in viral foodborne outbreak investigations due to their sensitivity, specificity and rapidity, there are very few methods to detect infectious tick-borne encephalitis virus (TBEV) in milk products for routine use/analyses. To address this gap, we developed a cell culture-based method to detect infectious TBEV in artificially contaminated raw goat milk and raw goat cheese, and evaluated the sensitivity of TBEV infectivity assays. Raw goat milk samples were spiked with TBEV to achieve inoculation levels ranging from 106 to 100 TCID50/mL, and Faisselle and Tomme cheese samples were spiked so their TBEV concentrations ranged from 9.28 × 105 to 9.28 × 101 TCID50 per 2.5g. To detect infectious TBEV, Vero cells were infected by raw goat milk. For cheese samples, after homogenisation and membrane filtration, Vero cells were infected with samples adsorbed on the filter (method A) or with samples eluted from the filter (method B). After 5 days, cytopathic effects (CPEs) were observed and TBEV replication in Vero cells was confirmed by an increase in the number of genome copies/mL that were detected in cell supernatant. Infected Vero cells exhibited CPEs for both milk and cheese samples. Infectious TBEV was detected to 103 TCID50/mL in raw milk samples and to 9.28 × 101 TCID50 from Faisselle samples using both methods A and B. For Tomme samples, method A was able to detect TBEV to 9.28 × 102 TCID50/2.5g and method B to 9.28 × 103 TCID50/2.5g. The number of positive samples detected was slightly higher with method A than with method B. To conclude, this qualitative cell culture-based method can detect infectious TBEV artificially inoculated into raw milk and cheese; it should be further evaluated during foodborne outbreak investigations to detect infectious TBEV from naturally contaminated milk and cheese.

A One-Health Approach to Investigating an Outbreak of Alimentary Tick-Borne Encephalitis in a Non-endemic Area in France (Ain, Eastern France): A Longitudinal Serological Study in Livestock, Detection in Ticks, and the First Tick-Borne Encephalitis Virus Isolation and Molecular Characterisation.

Tick-borne encephalitis virus’ (TBEV) geographic range and the human incidence are increasing throughout Europe, putting a number of non-endemic regions and countries at risk of outbreaks. In spring 2020, there was an outbreak of tick-born encephalitis (TBE) in Ain, Eastern France, where the virus had never been detected before. All patients but one had consumed traditional unpasteurised raw goat cheese from a local producer. We conducted an investigation in the suspected farm using an integrative One Health approach. Our methodology included (i) the detection of virus in cheese and milk products, (ii) serological testing of all animals in the suspected farm and surrounding farms, (iii) an analysis of the landscape and localisation of wooded area, (iv) the capture of questing ticks and small mammals for virus detection and estimating enzootic hazard, and (v) virus isolation and genome sequencing. This approach allowed us to confirm the alimentary origin of the TBE outbreak and witness in real-time the seroconversion of recently exposed individuals and excretion of virus in goat milk. In addition, we identified a wooded focus area where and around which there is a risk of TBEV exposure. We provide the first TBEV isolate responsible for the first alimentary-transmitted TBE in France, obtained its full-length genome sequence, and found that it belongs to the European subtype of TBEV. TBEV is now a notifiable human disease in France, which should facilitate surveillance of its incidence and distribution throughout France.

Pequi (Caryocar brasiliense) Waste Extract as a Synergistic Agent in the Microbial and Physicochemical Preservation of Low-Sodium Raw Goat Cheese.

The growth of spoilage and pathogenic bacteria during storage represents significant losses in marketing raw milk cheeses. Thus, reducing NaCl in these products is challenging, as sodium has a critical antimicrobial role. Despite advances in non-thermal technologies, the short shelf life still limits the availability of raw goat cheese. Thus, combined preservation methods can be promising because their synergies can extend shelf life more effectively. In this context, Principal Component Analysis (PCA) was applied to variables to investigate the effect of pequi waste extract (PWE), a native Brazilian fruit, combined with UV-C radiation (CEU) and vacuum packaging (CEV) on the preservation of low-sodium raw goat cheese. CEV samples had lower loadings for Staphylococcus subsp. and Enterobacteriaceae than other treatments in PC2, having a count’s reduction up to 3-fold (P < 0.05) compared to vacuum alone. In contrast, CEU showed an increase of up to 1.2-fold on staphylococcal count compared to UV-C alone. Still, the addition of PWE to UV-C-treated cheeses resulted in 8.5% protein loss. Furthermore, PWE, especially in CEV, delayed post-acidification during storage. It made CEV up to 4.5 and 1.6-fold more stable for color and texture, respectively than vacuum alone. These data strongly suggest that PWE may be a novel and promising synergistic agent in the microbial and physicochemical preservation of low-sodium raw milk cheese when combined with the vacuum.

Effects of the number of days and the filling sequence of animal skin-bags used for the traditional production of Algerian Bouhezza raw goat cheese on physicochemical composition, α-tocopherol, cholesterol content and stability

Traditional Algerian Bouhezza cheese is produced inside animal skin-bags with a fermented, buttermilk-like product, Lben. Two Bouhezza cheeses were simultaneously made in two skin-bags in each of two sequential years. Bags had a defined filling sequence (first or second) with Lben for the same batch. Samples from each bag were collected at days 7, 30 and 60 to obtain 6 samples per year and a total of 12 samples. The effects of number of days and filling sequence on gross composition, α-tocopherol, cholesterol content and stability were evaluated. With more days, dry matter, protein, fat, cholesterol and α-tocopherol contents increased and pH decreased (P < 0.01). At 60 d 100 g of Bouhezza contained 39.2 ± 7.04 mg of cholesterol. Cholesterol was never protected and oxidation was evident. Oxidation was highest in cheeses from the second-filled bags during the first 30 d of production (P < 0.05).

Further evidence for staphylococcal food poisoning outbreaks caused by egc-encoded enterotoxins.

Staphylococcal food poisoning represents the most prevalent foodborne intoxication worldwide. It is caused by oral intake of enterotoxins preformed by Staphylococcus aureus in food. The relevance of newly described enterotoxins in outbreaks of staphylococcal food poisoning is controversially discussed. Although the staphylococcal enterotoxins SEG, SEI, SEM, SEN, and SEO elicit emesis in a monkey feeding assay, there has been no conclusive proof of their emetic activity in humans. In this study, we provide further evidence suggesting that one of these enterotoxins or a combination of SEG, SEI, SEM, SEN, and SEO cause staphylococcal food poisoning. We investigated two outbreaks registered with the Swiss Federal Office of Public Health, in which only Staphylococcus aureus strains harboring the egc cluster, including seg, sei, sem, sen, and seo linked to typical signs of staphylococcal food poisoning were isolated. The outbreaks were caused by consumption of raw goat cheese and semi-hard goat cheese, and were linked to strains assigned to CC45 (agr type I) and CC9 (agr type II), respectively. These outbreaks provide further evidence that newly-described staphylococcal enterotoxins are likely to cause staphylococcal food poisoning in humans.

Behaviour of Escherichia Coli O157:H7 During the Manufacture and Ripening of an Italian Traditional Raw Goat Milk Cheese.

Formagelle di capra is a raw goat cheese produced from whole chilled goat milk; traditional technology involving unpasteurised milk and indigenous lactic starter cultures is employed for its production in Italy. The purpose of this study was to assess the behaviour of Escherichia coli O157:H7 during the manufacturing and ripening of this raw goat milk cheese. Raw milk was experimentally inoculated with E. coli O157:H7 in a laboratory scale plant and the count was monitored during production and 30 days of ripening required for this cheese. Results showed that E. coli O157:H7 count increased to more than 1.5 Log cfu g–1 during cheese production and remained constant until the end of ripening. The evidence that E. coli O157:H7 is able to survive during the manufacturing and ripening process suggests that the 30-day ripening period alone is insufficient to eliminate levels of viable E. coli O157:H7 in Formaggelle di capra cheese and that the presence of low numbers of E. coli O157:H7 in milk destined for the production of raw goat milk cheeses could represent a potential source of infection for humans and a threat for consumers.

Brucellosis outbreak due to unpasteurized raw goat cheese in Andalucia (Spain), January - March 2002.

Eleven brucellosis cases were identified in three municipalities of Cordoba (Andalucia, Spain). A case-control study was conducted, selecting three cases per control. Persons having eaten unpasteurized raw goat cheese produced in a farmhouse located in the epidemic territory, were at higher risk for presenting brucellosis (OR=21.6, IC95%=1.6-639.8). Brucella melitensis serovar 3 was identified in clinical specimens and in goat tissue and milk samples from the herd's farmhouse. Preventive measures were implemented and the outbreak was stopped after the withdrawal of all suspicious cheeses from the market, additional sanitation of the farmhouse and health promotion activities.

Brucellosis Outbreak Attributed to Ingestion of Unpasteurized Goat Cheese

In six cases of Brucella melitensis infection the common etiologic factor was the ingestion of raw goat cheese. Presenting complaints were variable, but a constant feature was persistent fevers that frequently were present for months. Evidence of liver cell dysfunction was present in each case, and in two, biopsy disclosed diffuse hepatitis with focal necrosis. The diagnoses were initially based on high titers of Brucella agglutinins and later confirmed by positive blood cultures. A good clinical response was induced by antibiotic therapy (tetracycline plus streptomycin sulfate), but in two cases a Jarish-Herxheimer reaction occurred during the first 24 hours of treatment.

Brucellosis outbreak attributed to ingestion of umpasteurized goat cheese

In six cases of Brucella melitensis infections the common etiologic factor was the ingestion of raw goat cheese. Presenting complaints were variable, but a constant feature was persistent fevers that frequently were present for months. Evidence of liver cell dysfunction was present in each case, and in two, biopsy disclosed diffuse hepatitis with focal necrosis. The diagnoses were initially based on high titers of Brucella agglutinins and later confirmed by positive blood cultures. A good clinical response was induced by antibiotic therapy ( tetracycline plus streptomycin sulfate), but in two cases a Jarish-Herxheimer reaction occurred during the first 24 hours of treatment.