The aim of the research was an examination of potential impact of milk yield on the intercompartmental clearance – distribution clearance as well as determination of the variability of obtained pharmacokinetic parameters by the population approach using a two-compartmental structural model. Blood perfusion has a considerable impact on physiology of the udder and kinetics of drugs that are distributed in this organ. The research was performed on healthy Holstein- Friesian and Polish Black-White cows at the age of 4-10 years. Determination of antibiotics (ampicillin, amoxicillin, cefoperazone, penicillin G prokaine, cloxacillin, cefacetril) concentration was carried out after their every intramammary administration to one quarter of the udder. A population pharmacokinetic model was created to fit milk concentration data. General milk yield of a single cow was used as a variable. A population analysis was conducted using non-linear mixed-effect modeling. The impact of milk productivity was set solely by reference to intercompartmental clearance only in case of penicillin G, cloxacillin and ampicillin. It, has been found that milk yield, depending on a drug, influenced the distribution clearance of the drug to varying degrees. It means indirectly that increased perfusion of the udder has a different impact on drug distribution from the udder to the bloodstream.

The objectives of this study were to determine the genetic relatedness, antibiogram and virulence factors of Staphylococcus aureus (S. aureus) isolated from bovine mastitis, associated farm workers, dairy cow farm veterinarians (private veterinarians), veterinary students, and non-veterinary university students. A total of 84 S. aureus isolates (27 from mastitis, 11 from farm workers, 9 from private veterinarians, 22 from veterinary students, and 16 from non-veterinary university students) were used to determine antimicrobial sensitivity patterns using disk diffusion test, virulence factors using PCR technique and phylogenic analysis using pulsed field gel electrophoresis. All S. aureus isolates were resistant to 2 or more commonly used antibiotics. All isolates from mastitis, farm workers, and veterinary students carried the genes encoding coagulase and thermonuclease factors while isolates from non-veterinary university students carried the genes encoding coagulase, clumping, and thermonuclease factors. The mecA gene was detected in 22.2%, 81.8%, 100%, 95.5% and 100% of isolates from mastitis, farm workers, private veterinarians, veterinary students, and non-veterinary university students, respectively. In the phylogenic analysis, 10 (45.5%), 6 (66.7%) and 8 (72.7%) isolates from veterinary students, private veterinarians and farm workers, respectively were more than 80% similar to isolates from mastitis. Results of this study indicate that S. aureus isolates from mastitis milk and those from related dairy cow personnel and veterinarians share similar antimicrobial sensitivity patterns and virulence factors, therefore a common source of bacteria may exist. Furthermore, possible transmission of S. aureus between cows and cow-related personnel and vice versa could also exist.