Genetic relatedness and virulence factors of bovine Staphylococcus aureus isolated from teat skin and milk.

The objective of this study was to assess the role of teat skin colonization in Staphylococcus aureus intramammary infections (IMI) by evaluating genetic relatedness of Staph. aureus isolates from milk and teat skin of dairy cows using pulsed-field gel electrophoresis and characterizing the isolates based on the carriage of virulence genes. Cows in 4 known Staph. aureus-positive herds were sampled and Staph. aureus was detected in 43 quarters of 20 cows, with 10 quarters positive in both milk and skin (20 isolates), 18 positive only in milk, and 15 only on teat skin. Quarters with teat skin colonized with Staph. aureus were 4.5 times more likely to be diagnosed with Staph. aureus IMI than quarters not colonized on teat skin. Three main clusters were identified by pulsed-field gel electrophoresis using a cutoff of 80% similarity. All 3 clusters included both milk and skin isolates. The majority of isolates (72%) belonged to one predominant cluster (B), with 60% of isolates in the cluster originating from milk and 40% from teat skin. Genotypic variability was observed within 10 pairs (formed by isolates originating from milk and teat skin of the same quarter), where isolates in 5 out of the 10 pairs belonged to the same cluster. Forty-two virulence factors were screened using PCR. Some virulence factors were carried more frequently by teat skin isolates than by milk isolates or isolates from quarters with high somatic cell counts. Isolates in the predominant cluster B carried virulence factors clfA and clfB significantly more often than isolates in the minor clusters, which may have assisted them in becoming predominant in the herds. The present findings suggest that teat skin colonization with Staph. aureus can be an important factor involved in Staph. aureus IMI.

[The state of anticoagulant system of animals following injections of purified thrombin and N-acetyl-thrombin]. / Sostoianie protivosvertyvaiushchei sistemy zhivotnykh posle in"ektsii preparatov ochishchennogo trombina i N-atsetil-trombina

I. v. administration of N-acetyl-thrombin, similar to thrombin, increases the fermentative fibrinolytic potency of the plasma, although to a lesser extent. This is also expressed in the increased esterase activity of the plasma and euglobulin fraction. When blocking the forming plasmin, esterase activity is observed in kallekreine. (The inhibitory effect of plasma after N-acetyl-thrombin administration tells also on the nonfermentative fibrinolytic activity of the Fibrinogen-Heparin complex, activity of the latter dropping practically to the zero level. Warming up at 60 degrees C decreases the nonfermentative fibrinolytic activity of the complex N-acetyl-thrombin (thrombin-esterase) does not provoke the activation of the second anticoagulang system, while the native thrombin does it.