Staphylococcus aureusreservoirs during traditional Austrian raw milk cheese production

Abstract

Sampling approaches following the dairy chain, including microbiological hygiene status of critical processing steps and physicochemical parameters, contribute to our understanding of how Staphylococcus aureus contamination risks can be minimised. Such a sampling approach was adopted in this study, together with rapid culture-independent quantification of Staph. aureus to supplement standard microbiological methods. A regional cheese production chain, involving 18 farms, was sampled on two separate occasions. Overall, 51·4% of bulk milk samples were found to be Staph. aureus positive, most of them (34·3%) at the limit of culture-based detection. Staph. aureus positive samples >100 cfu/ml were recorded in 17·1% of bulk milk samples collected mainly during the sampling in November. A higher number of Staph. aureus positive bulk milk samples (94·3%) were detected after applying the culture-independent approach. A concentration effect of Staph. aureus was observed during curd processing. Staph. aureus were not consistently detectable with cultural methods during the late ripening phase, but >100 Staph. aureus cell equivalents (CE)/ml or g were quantifiable by the culture-independent approach until the end of ripening. Enterotoxin gene PCR and pulsed-field gel electrophoresis (PFGE) typing provided evidence that livestock adapted strains of Staph. aureus mostly dominate the post processing level and substantiates the belief that animal hygiene plays a pivotal role in minimising the risk of Staph. aureus associated contamination in cheese making. Therefore, the actual data strongly support the need for additional sampling activities and recording of physicochemical parameters during semi-hard cheese-making and cheese ripening, to estimate the risk of Staph. aureus contamination before consumption.

Identification of the risk factors associated with cheese production to implement the hazard analysis and critical control points (HACCP) system on cheese farms

“…The other analyzed microorganism results are shown in Table 4. The high TVC in milk agreed with those indicated in other studies (Smigic et al, 2012;Belli et al, 2013;Walcher et al, 2014).…”

Sensitive and rapid detection of staphylococcus aureus in milk via cell binding domain of lysin

“…The number of S. aureus in raw milk or other dairy products needs to be less than 10 4 CFU/g according to the regulation of FDA in USA (http:// www.fda.gov/food/foodscienceresearch/safe practicesforfoodprocesses/ucm094156.htm). Similar limit is suggested for other countries, such as Australia (Walcher et al, 2014) and New Zealand (Hill et al, 2012). Therefore, sensitive and rapid detection of S. aureus is important for food quality and safety.…”

Detection of staphylococcal enterotoxin genes in raw milk samples by real-time PCR

“…Most studies on S. aureus in raw milk reported a prevalence ranging from 47.2% to 94.3% (Jørgensen et al 2005;D'amico and Donnelly. 2011;Jakobsen et al2011;Walcher et al 2014), by either a conventional or molecular method.Variations in toxin gene prevalence from 74% down to 16% in isolates from milk has been reported in several recent studies (Rosengren et al 2010;Hunt et al 2012;Hummerjohann et al 2014;Carfora et al 2015). The presence of staphylococcal enterotoxin genes in this study, was not different from previous studies.…”