Pulsed-field gel electrophoresis shows that Staphylococcus aureus isolates from bulk milk has different subgenotypes than those found in humans. These results support the hypothesis that there is no epidemiological association between isolates from humans and those from bulk milk. Additionally, one and two dominant genotypes were found in methicillin-resistant human and bulk milk isolates, respectively. Isolates belonging to the dominant genotypes showed specific characteristics, including the coagulase serotype, the capsule serotype, exotoxin genes and antimicrobial susceptibility. Isolates from bulk milk did not show the penicillin-binding protein 2a gene, and most isolates belonging to the two dominant genotypes of bulk milk were susceptible to ampicillin, cefazolin, erythromycin, chloramphenicol, oxacillin, and vancomycin. Moreover, the LukM/LukF'-PV leukocidin gene was detected in only 233 isolates belonging to the dominant genotypes in bulk milk isolates. These results support the hypothesis that certain factors play a role in the adaptation of S. aureus isolates to specific hosts.
(Research Team for Bacterial/Parasitic Diseases, TEL +81-29-838-7708)
Reference:
Hata et al. (2008) J. Dairy Sci. 91 : 564-569.
