Enterotoxin-Encoding Genes inStaphylococcusspp. from Bulk Goat Milk

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.

Occurrence and antibiotic resistance of enterotoxigenic Staphylococcus aureus in raw ovine and caprine milk in Greece

“…In agreement with previous studies, we found that enterotoxigenic CM isolates mainly harbored the sec gene (Akineden et al 2008;Lyra et al 2013;Scherrer et al 2004). None of our CM isolates carried the seb gene.…”

“…The frequent combination of seg and sei genes in toxigenic S. aureus strains in our study is consistent with previous reports (Lyra et al 2013;Rosec and Gigaud 2002;Scherrer et al 2004). Some authors reported a predominant and systematic co-detection of seg and sei genes (Rosec and Gigaud 2002) whereas others have reported their presence individually or in different combinations with other se genes (Arcuri et al 2010;Cremonesi et al 2007;Zouharova and Rysanek 2008).…”

“…None of our CM isolates carried the seb gene. Similarly, several studies reported that none of the strains isolated from bovine and CM and dairy products harbored the seb gene (Akineden et al 2001;Lyra et al 2013). In other studies, however, the seb gene was detected in S. aureus isolates from milk and dairy products at various frequencies (Jørgensen et al 2005;Zouharova and Rysanek 2008).…”

Occurrence of enterotoxin-encoding genes in Staphylococcus aureus causing mastitis in lactating goats

“…Information about enterotoxin-encoding genes in Staphylococci from goat milk is scarce in Brazil. However, the frequency of positive isolates found in the present study is very similar to 23.3% of coagulase-positive staphylococci from bulk tank goat milk in Cariri region harboring at least one enterotoxin-encoding gene (Lyra et al 2013).…”

“…This has also been reported as the most frequent gene in staphylococcus from goat milk by Scherrer et al (2004) and Lyra et al (2013), who observed secin 42% and 55.6% of positive staphylococci, respectively. The gene sec was also reported by Loncarevic et al (2005) as the most frequent classical enterotoxin-encoding gene amongst Staphylococcus from goat milk.…”