The Occurrence of Staphylococcus aureus on a Farm with Small-Scale Production of Raw Milk Cheese

Abstract

In recent years, the small-scale production of raw milk products has increased in Norway, and there is some concern that such foods may pose a risk of staphylococcal food poisoning to consumers. The aim of the study was to evaluate potential sources of contamination of raw milk cheese with Staphylococcus aureus on a bovine dairy farm with small-scale production. Samples for bacteriological analyses (n = 144) were collected from the animals, the environment, processing equipments, from humans, and from cheeses at various stages of production. Staphylococcus aureus was isolated from 10 of 11 cows, the farmer, equipment, the environment, and the cheese. Seventy-five Staph. aureus isolates were genotyped by pulsed-field gel electrophoresis, tested for enterotoxin (SE) production by reversed passive latex agglutination, for SE genes by multiplex polymerase chain reaction, and for penicillin resistance by the cloverleaf method. Five different pulsotypes were identified and SE gene fragments were identified in 11 isolates, but no isolates produced SE or were penicillin resistant. Staphylococcus aureus was found throughout the farm, and appeared to be spread with the milk to the environment, equipment, and to products. One pulsotype dominated and was identified from most sample sites on the farm. Raw milk products are vulnerable to contamination with Staph. aureus. Strategies to reduce the occurrence of Staph. aureus in bulk milk are of particular importance on farms where milk is used for raw milk products.

Study on the Prevalence and Distribution of Staphylococcus aureus in Raw Cow Milk Originated from Alage Atvet College Dairy Farm, Ethiopia

“…75% of contamination found in Norway [20]. In this study the result showed a high rate of contamination at the milk collection centre than the farm.…”

“…Mastitis presence will also be the factor as Asperger and Zangeri said about 40% of the cases would be associated with the presence of mastitis. Environmental contamination during raw milk handling also results S. aureus to get a chance contaminating the milk [19][20][21].…”

Characterization of Staphylococcus aureus strains isolated from bovine milk in Hungary

“…Unlike the producer organism, SEs are remarkably heat resistant, showing D-values of 3 min to 8 min at 121°C (Asperger and Zangerl, 2003). As a result, they may be present in foods even when viable S. aureus are absent (Jørgensen et al, 2005c). Traditionally, five classical antigenic SE types (SEA, SEB, SEC, SED, and SEE) were recognized.…”

“…The organism is responsible for approximately 30% to 40% of all mastitis cases (Asperger and Zangerl, 2003). S. aureus can gain access to milk either by direct excretion from udders with clinical or subclinical staphylococcal mastitis or by contamination from the environment during handling and processing of raw milk (Scherrer et al, 2004;Jørgensen et al, 2005c). When the udder is infected, S. aureus is excreted in the milk with large fluctuations in counts ranging from zero to 10 8 CFU/ml (Asperger and Zangerl, 2003).…”

Safety Evaluation Of Sjenica Cheese With Regard To Coagulase-Positive Staphylococci And Antibiotic Resistance Of Lactic Acid Bacteria And Staphylococci

“…It was found that the number of CoPS decreased from day 3 to day 7 and was only present in low numbers (10 2 cfu/g) by day 90 (results not shown). The similar dynamic of CoPS population in raw milk cheese matrix was reported by other authors [24][25][26] who pointed out that inhibitory effects of natural LAB microbiota, reduced water activity (a w ) resulting from whey drainage, increased salt concentration during brining and temperature profi le of the ripening process generate a hostile environment suboptimal for staphylococcal growth [27].…”