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

• Published in: Foodborne pathogens and disease Vol. 10; no. 2; p. 126
• Main Authors: Lyra, Daniele G, Sousa, Francisca G C, Borges, Maria F, Givisiez, Patrícia E N, Queiroga, Rita C R E, Souza, Evandro L, Gebreyes, Wondwossen A, Oliveira, Celso J B
• Format: Journal Article
• Language: English
• Published: United States 01.02.2013
• Subjects: 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; Brazil
• ISSN: 1556-7125
• DOI: 10.1089/fpd.2012.1256

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.