AUTHOR=Merz Axel , Stephan Roger , Johler Sophia 

TITLE=Staphylococcus aureus Isolates from Goat and Sheep Milk Seem to Be Closely Related and Differ from Isolates Detected from Bovine Milk

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00319

DOI=10.3389/fmicb.2016.00319

ISSN=1664-302X

ABSTRACT=<p>Dairy goat and sheep farms suffer severe economic losses due to intramammary infections, with <italic>Staphylococcus aureus</italic> representing the main cause of clinical mastitis in small ruminants. In addition, <italic>S. aureus</italic> contamination of goat and sheep milk may cause staphylococcal food poisoning, as many traditional caprine and ovine milk products are not subjected to pasteurization. Data on virulence and antimicrobial resistance genes, as well as on the clonality of <italic>S. aureus</italic> detected in goat and sheep milk is scarce. Therefore, it was the aim of this study to determine (i) <italic>spa</italic> types and clonal complexes (CC) and (ii) virulence and resistance gene profiles of <italic>S. aureus</italic> isolated from goat and sheep milk. A total of 162 milk samples from sheep and goats presenting signs of an intramammary infection and 104 bulk milk samples were collected. While low prevalence rates of <italic>S. aureus</italic> was detected on single animal level, 46% of the bulk tank milk samples from small ruminants were positive for <italic>S. aureus.</italic> All isolates were <italic>spa</italic> typed and CC and virulence and resistance gene patterns were determined using a DNA microarray. Data from 49 <italic>S. aureus</italic> isolates was included in the statistical analysis and the construction of a SplitsTree. The analyzed isolates could be assigned to eleven CC, with the large majority of goat and sheep isolates being assigned to CC130 and CC133. The findings of this study suggest that <italic>S. aureus</italic> shows pronounced adaptation to small ruminants in general, but not to sheep or goats in particular. Although some common characteristics among <italic>S. aureus</italic> from caprine, ovine, and bovine milk samples were observed, <italic>S. aureus</italic> from small ruminants seem to form a distinct population. As 67% of the detected <italic>S. aureus</italic> strains exhibited at least one enterotoxin gene, many caprine, or ovine raw milk products may be contaminated with low levels of enterotoxigenic <italic>S. aureus</italic>, stressing the importance of strict maintenance of the cold chain.</p>