[Occurrence of antibiotic resistance in bacteria causing mastitis in dairy cows]

In 1986-1992 the susceptibility to antibiotics was investigated in 799 strains of causative agents of bovine mastitis. Of these, Streptococci, Staphylococcus aureus, coagulase-negative Staphylococci and other bacteria presented 43.5%, 22.2%, 17.9% and 16.6%, respectively. The strains examined were obtained from herds in which mastitis had been treated. Within the period of investigation, the resistance of S. aureus to antibiotics reached the following values: penicillin (PNC) 33.0-20.3%, chloramphenicol (CHF) 7.8-4.1%, oxacillin (OXAC) 6.8-4.1%, erythromycin (ERYT) 1.4-1.9% and oxytetracycline (OTTE) 4.1-3.9%. Beta-haemolytical Streptococci were PNC-, CHF-, OXAC-, OTTE- and ERY-resistant in 3.3-5.8, 1.9-2.5, 2.5-5.8, 1.7-1.9 and 1.7-5.8 percent of the cases, respectively. PNC, CHF, OXAC, ERYT and OTTE resistance was found in 5.7-2.3, 2.9-1.2, 5.2-2.7, 17.1-2.3 and 5.7-2.3% of Streptococcus uberis strains, respectively. In Streptococcus dysgalactiae the following values of resistance to antibiotics were found: PNC--5.3-2.8%, CHF and OXAC--5.3-2.8%, ERYT--15.8-2.8% and OTTE--10.5-2.3%. Resistance to PNC, CHF, OXAC, ERYT and OXYT was observed in 16.7-10.0, 25.0-20.0, 8.3-3.3, 16.7-20.0 and 16.7-6.7% of Corynebacterium spp. strains. Coagulase-negative Staphylococci were resistant as follows: PNC--34.3-31.5%, CHF--5.7-5.6%, OXAC--14.9-7.2%, ERYT--8.9-2.8% and OTTE--17.1-4.6%. Escherichia coli strains were CHF-resistant in 18.2-5.4% and OTTE-resistant in 27.8-28.1% of the cases. In Pseudomonas aeruginosa, CHF- and OTTE-resistance was recorded in 36.4-34.1 and 45.5-31.3% of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)