Clonal profile, virulence and resistance of Staphylococcus aureus isolated from sheep milk

Abstract

The objective of this study was to characterize the clonal profile, virulence factors and antimicrobial resistance, particularly oxacillin resistance, of Staphylococcus aureus isolated from sheep milk. Milk samples were collected from all teats for the California Mastitis Test (CMT), somatic cell count, identification of S. aureus, investigation in these strains of genes encoding toxins (sea, seb, sec, sed, tst), biofilm (icaA, icaC, icaD, bap), leukocidin (luk-PV) oxacillin resistance by mecA gene detection and susceptibility testing (12 antibiotics). Messenger RNA expression was evaluated by RT-PCR in isolates carrying toxin and biofilm genes. Biofilm formation was also evaluated phenotypically by adherence to polystyrene plates. The clonal profile of S. aureus was investigated by pulsed-field gel electrophoresis. A total of 473 milk samples were collected from 242 animals on three farms and 20 S. aureus strains were isolated and none carried the mecA gene. The two sec gene-positive isolates and the isolates carrying the tst and luk-PV genes were positive by RT-PCR. Staphylococcus aureus isolated from the three flocks studied showed high susceptibility to the drugs tested and none was biofilm producer, indicating that biofilm formation was not a virulence factor causing infection by these strains. The typing of 17 S. aureus isolates revealed the presence of a common clone on the three farms studied, and the presence and expression of the sec and tst genes in one strain of this clone suggest the possible acquisition of virulence genes by this clone, a fact that is important for animal health and food hygiene.

Phenotypic and Molecular Detection of Biofilm Formation in Staphylococcus aureus Isolated from Different Sources in Algeria

“…This result was in concordance with the study of Rodriguez-Lazaro et al [38]. Most of S. aureus isolates from sheep mastitis did not form biofilms (82.1%), which was in concordance with a previous report on S. aureus isolates from sheep milk [39]. In the present study, 52.6% of human isolates were biofilm-producing S. aureus.…”

“…In this study, presence of the bap gene was not found in any of the isolates. In general, the bap gene, which promotes inert surfaces and intracellular adhesion, is rarely observed in S. aureus [39,50] and its presence has only been reported in few S. aureus isolates from cases of bovine and sheep mastitis [39,51,52].…”

Occurrence of toxin genes in Staphylococcus pseudintermedius from diseased dogs and other domestic and wild species

“…In this study, all the isolates had at least one of the eight toxin genes which is, in contrast to another study that showed the presence of at least one toxin gene in only 35% of the S. aureus isolates examined [20]. To date, S. pseudintermedius has not been studied for simultaneous detection of the eight toxins particularly in diseased animals.…”

Isolation and identification of Yersinia enterocolitica in bovine milk samples of bulk tanks from dairy farms in São Paulo, Brazil

“…DNA extraction was performed with the Illustra Blood GenomicPrep Mini Spin Kit (GE Healthcare), with modifications when carried out directly from raw milk samples (MARTINS et al, 2015), and according to the manufacturer when carried out from cryopreserved colonized. After the extraction, all the milk samples were submitted to PCR testing for the detection of all species of the genus Yersinia, using the primers 227Fmod and 669R, which produced 428 to 465 bp fragments (STENKOVA et al, 2008).…”