Enterotoxin gene profiles among Staphylococcus aureus isolated from raw milk

Area of Science:

• Food Microbiology
• Bacterial Pathogenesis
• Public Health

Background:

• Raw milk is a nutritious food but can harbor pathogenic bacteria like Staphylococcus aureus.
• Staphylococcus aureus produces Staphylococcal enterotoxins (SEs), which are a major cause of foodborne illness.
• Understanding the prevalence of enterotoxin genes in milk-borne S. aureus is crucial for food safety.

Purpose of the Study:

• To determine the frequency and profiles of genes encoding nine Staphylococcal enterotoxins (SEs) in S. aureus isolates from raw bovine milk.
• To assess the potential public health risk associated with enterotoxigenic S. aureus in the dairy supply chain.

Main Methods:

• Isolation and identification of S. aureus from 246 raw bovine milk samples using cultural, biochemical, and molecular (23S rRNA gene amplification) methods.
• Detection of genes encoding nine different Staphylococcal enterotoxins (sea, seb, sec, sed, see, seg, seh, sei, sej) using molecular techniques.
• Analysis of enterotoxin gene profiles and identification of different genotypes.

Main Results:

• 52 S. aureus isolates were identified from 246 milk samples.
• 80.7% of the S. aureus isolates carried one or more enterotoxin genes, with 12 distinct genotypes identified.
• The most prevalent enterotoxin genes were sea (30.7%), seb (26.9%), sed (15.37%), seg (15.38%), and seh (15.38%).

Conclusions:

• A high proportion of S. aureus isolates from raw bovine milk in Qom, Iran, are enterotoxigenic.
• The presence of these enterotoxin genes indicates a significant potential risk to consumer health through raw milk consumption.
• Increased identification of new SEs suggests a growing pathogenic potential in Staphylococci, necessitating enhanced food safety monitoring.