Enterotoxigenic Staphylococcus aureus in bulk milk in Norway

Area of Science:

• Food Microbiology
• Bacterial Pathogenesis
• Public Health

Background:

• Staphylococcus aureus is a common cause of foodborne illness.
• Enterotoxin production by S. aureus is a significant public health concern.
• Raw milk products can be a vehicle for pathogen transmission.

Purpose of the Study:

• To determine the prevalence of enterotoxigenic Staphylococcus aureus in Norwegian bulk milk (bovine and caprine) and raw milk products.
• To characterize the presence of staphylococcal enterotoxin (SE) genes in S. aureus isolates.
• To assess the potential risk of staphylococcal food poisoning associated with raw milk consumption.

Main Methods:

• Analysis of 220 bovine and 213 caprine bulk milk samples and 82 raw milk products for S. aureus.
• Detection of staphylococcal enterotoxins (SEA-SED) using reversed passive latex agglutination.
• Identification of SE genes (sea-see, seg-sej) via multiplex PCR.

Main Results:

• Staphylococcus aureus was detected in 75% of bovine and 96.2% of caprine bulk milk, and 37.8% of raw milk products.
• Enterotoxin production was observed in 22.1% (bovine) and 57.3% (caprine) of S. aureus isolates.
• SE genes were present in 52.5% (bovine) and 55.8% (caprine) of isolates, with SEC and sec being most common.

Conclusions:

• Staphylococcus aureus is highly prevalent in Norwegian bulk milk, with frequent enterotoxin production and gene presence.
• Enterotoxigenic S. aureus strains were also identified in raw milk products.
• The presence of enterotoxigenic S. aureus in Norwegian milk poses a risk for staphylococcal food poisoning from raw milk products.