Influence of Staphylococcus aureus exosecretions isolated from bovine mastitis on leukocyte activity in vitro

Effects of Escherichia coli- and Staphylococcus aureus-induced mastitis in lactating cows on oocyte developmental competence

Mastitis is associated with decreased fertility in dairy cows. In the current study, we created an experimental model to simulate short-term mastitis by a single intramammary administration of Gram-negative endotoxin ofEscherichia coliorigin (G−), or Gram-positive toxin ofStaphylococcus aureusorigin (G+), to examine the effect of mastitis on oocyte developmental competence. Healthy Holstein cows were synchronized, and follicular fluid (FF) of cows treated with G+ or G− and of uninfected cows (controls) was aspirated from the preovulatory follicles by transvaginal ultrasound procedure. The aspirated FF was used as maturation medium forin vitroembryo production. The distribution of matured oocytes into different cortical granule classes and meiotic stages was affected by G− administration (P<0.05) but not by G+ administration. The proportion of oocytes that cleaved to two- and four-cell stage embryos (44 h postfertilization) was lower in both G+ and G− groups than in controls (P<0.05). Blastocyst formation rate (7–8 days postfertilization) was lower in the G− group (P<0.05) and numerically lower in the G+ group compared with their uninfected counterparts. The total cell number in blastocysts did not differ among groups; however, the apoptotic index was higher in the G+ group (P<0.05), but not in the G− group, relative to controls. Examining mRNA relative abundance in oocytes and early embryos revealed mastitis-induced alterations inPTGS2(COX2),POU5F1, andHSF1but not inSLC2A1(GLUT1) orGDF9. Results indicate a differential disruptive effect of mastitis induced by G− and G+ on oocyte developmental competence in association with alterations in maternal gene expression.

Superantigen gene profiles, genetic relatedness and biological activity of exosecretions of Staphylococcus aureus isolates obtained from milk of cows with clinical mastitis

This study evaluated the superantigen gene profiles, genetic relatedness and biological activity of exosecretions of 50 Staphylococcus aureus isolates obtained from milk of cows with clinical mastitis. Genomic relatedness of S. aureus was determined by pulsed field gel electrophoresis analysis of macro-restricted chromosomes. The presence of genes encoding superantigens was confirmed by multiplex PCR. To study the biological activity of S. aureus exosecretions, the supernatants from bacterial liquid cultures were classified into three groups: those with leukotoxin‐like properties, those with superantigen‐like properties and those with no particular activity on leukocytes cultured in vitro. It was shown that all analyzed bacterial isolates belonged to the same clonal type and harbored the same combination of superantigen genes, namely sed, selj and ser. However, 22% of all isolates produced factors with superantigen‐like and 48% of them with leukotoxin‐like activities. Finally, although there were no detectable genetic differences between the analyzed bacterial isolates, the virulence factors secreted by them differed considerably.

Influence of S. aureus exosecretions on cytokine profile in bovine leukocyte cultures in vitro

The aim of the research was to evaluate the in vitro effect of Staphylococcus aureus exosecretions on the expression of genes encoding IL-2 and IL-12 and secretion of IFN-γ and TNF-α, in bovine leukocyte cultures in vitro. The research was based on 30 S. aureus isolates collected from milk samples from cows with clinical mastitis. Supernatants prepared from the bacterial liquid cultures, which were used to treat leukocytes, were divided into three groups: one with superantigen-like properties, one with leukotoxic-like properties and the one without superantigen or leukotoxic-like properties. The MNC, PMN and MIX (consisted of MNC and PMN leukocytes) cultures were grown and treated with the supernatants. The work shows that the effect on the cytokine gene expression and cytokine secretion caused by S. aureus exosecretions is mainly due to the presence of virulence factors connected with superantigen-like activity and less with leukotoxic-like activity whereas exosecretions of other activity are not or only slightly involved in this process.

Secretory virulence factors produced by Staphylococcus aureus isolates obtained from mastitic bovine milk--effect on bovine polymorphonuclear neutrophils

The aim of the research was to test whether exogenic virulence factors secreted by Staphylococcus aureus isolates are involved in mechanisms that allow the bacteria to modulate and evade phagocytosis by bovine polymorphonuclear neutrophils. The research was based on the comparison of the effects of supernatants, prepared from cultures of 30 S. aureus isolates, on the functional properties of bovine neutrophils in vitro. S. aureus isolates were collected from milk samples from cows with clinical mastitis. Supernatants, which were used to treat leukocytes, were prepared from 18 h S. aureus cultures. Exogenic virulence factors secreted by S. aureus isolates significantly influenced the phagocytosis parameters evaluated. Depending on their leukotoxic or superantigenic properties, supernatants could affect the ingestion process, and also showed an influence on the digestion efficiency and phagocytosis carried out by bovine polymorphonuclear neutrophils in vitro.