Activity of β-lactam antibiotics against certain microorganisms which cause mastitis in cows

Abstract

Abstract Introduction: The objective of this study was to determine the current profile of bacteria responsible for the infection of the mammary gland and to assess their sensitivity to selected β-lactam antibiotics. Material and Methods: The study was conducted on 119 (n = 119) dairy cows of the Polish Black-White breed aged 4 to 10 years with inflammation of the mammary gland. The cows came from different farms: smallholder farms and large dairy cattle farms in the Lublin and Bialystok Provinces. Before the process of collection of milk samples, the teats were cleaned and immersed in a liquid disinfectant. The first streams were collected into containers which were subsequently utilised. Afterwards, 2-4 mL of milk or secretions was milked into sterile disposable tubes. The milk samples were collected into plastic bottles and kept in a cooler with ice until transportation to the laboratory. Tests of resistance to β-lactam antibiotics were performed by disc diffusion. Results: Contagious and environmental bacteria were isolated from all dairy barns. In the group of contagious bacteria, the presence of typical pathogens responsible for the mammary gland infections, i.e. Staph. aureus, Str. agalactiae, and C. bovis, was detected. A relatively broad group of the isolates was formed by environmental bacteria responsible for inflammation of the mammary gland: Str. dysgalactiae, Str. uberis, Staph. chromogenes, Staph. hyicus, Staph. warneri, and E. coli. Among the environmental organisms, streptococci constituted the largest percentage (23%), followed by staphylococci (13.2%), and E. coli (8.8%). The largest group of infectious pathogens comprised Str. agalactiae (29.6%) and Staph. aureus (20.8%). Conclusion: Our investigation of the current profile of the isolates responsible for mastitis in the Lublin and Bialystok Provinces showed that environmental bacteria are the major cause of the disease. In view of the substantially varying degrees of sensitivity of the microorganisms isolated from cases of mastitis to β-lactam antibiotics, each therapeutic treatment should be preceded by susceptibility testing.