| Abstrakt: |
Safe dairy food production starts at the farm level, with the presence of pathogens on farms potentially impacting the downstream food supply. Studies often commence with looking for pathogens in fecal material of farm animals, predominantly cows; however, pathogens may arise from other on-farm sources. In Australia, few studies have looked at the broader farm environment, particularly in relation to Escherichia coliand Salmonella. The present study characterized the genetic similarity of these pathogens from bovine, ovine, and caprine dairy farm environments and related this to the stx1, stx2, eae,or ehxvirulence markers in E. coliand antibiotic resistance in Salmonella. E. coliisolates with indistinguishable genetic profiles and at least one of the virulence factors were found in multiple samples on the farms, although profiles were unique to each farm. E. coliO26 with stx1from one bovine farm had a different fingerprint type than all of the other E. coliO26 isolates, which lacked the Shiga toxin genes. They were from a separate bovine farm and were themselves closely related. No antibiotic resistance was detected among Salmonellaisolates to the 17 antibiotics tested. Three Salmonellaserotypes were identified: Orion, Infantis, and Zanzibar. The published PCR serotyping method used misidentified SalmonellaZanzibar as SalmonellaJaviana, which was revealed after conventional antisera-based serotyping; this illustrates the need for caution when using PCR techniques for Salmonellaserotype identification. Of the three serotypes, SalmonellaOrion was most prevalent and was potentially resident on the farm. This article describes the previously unreported genetic diversity of potentially pathogenic E. coliand Salmonellaserotypes from the farm environments of three dairy animal species in Victoria, Australia. |
