Enterotoxin-encoding genes in Staphylococcus spp. from bulk goat milk

Foodborne Pathog Dis. 2013 Feb;10(2):126-30. doi: 10.1089/fpd.2012.1256.

Abstract

Although Staphylococcus aureus has been implicated as the main Staphylococcus species causing human food poisoning, recent studies have shown that coagulase-negative Staphylococcus could also harbor enterotoxin-encoding genes. Such organisms are often present in goat milk and are the most important mastitis-causing agents. Therefore, this study aimed to investigate the occurrence of enterotoxin-encoding genes among coagulase-positive (CoPS) and coagulase-negative (CoNS) staphylococci isolated from raw goat milk produced in the semi-arid region of Paraiba, the most important region for goat milk production in Brazil. Enterotoxin-encoding genes were screened in 74 staphylococci isolates (30 CoPS and 44 CoNS) by polymerase chain reaction targeting the genes sea, seb, sec, sed, see, seg, seh, and sei. Enterotoxin-encoding genes were found in nine (12.2%) isolates, and four different genes (sea, sec, seg, and sei) were identified amongst the isolates. The most frequent genes were seg and sei, which were often found simultaneously in 44.5% of the isolates. The gene sec was the most frequent among the classical genes, and sea was found only in one isolate. All CoPS isolates (n=7) harboring enterotoxigenic genes were identified as S. aureus. The two coagulase-negative isolates were S. haemolyticus and S. hominis subsp. hominis and they harbored sei and sec genes, respectively. A higher frequency of enterotoxin-encoding genes was observed amongst CoPS (23.3%) than CoNS (4.5%) isolates (p<0.05), reinforcing the importance of S. aureus as a potential foodborne agent. However, the potential risk posed by CoNS in goat milk should not be ignored because it has a higher occurrence in goat milk and enterotoxin-encoding genes were detected in some isolates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brazil
  • Coagulase / analysis
  • DNA, Bacterial / isolation & purification*
  • Enterotoxins / genetics*
  • Enterotoxins / isolation & purification
  • Food Contamination / analysis
  • Food Microbiology
  • Genes, Bacterial*
  • Goats
  • Milk / microbiology*
  • Polymerase Chain Reaction
  • Sequence Analysis, DNA
  • Staphylococcus / classification*
  • Staphylococcus / genetics*
  • Staphylococcus / isolation & purification

Substances

  • Coagulase
  • DNA, Bacterial
  • Enterotoxins