The Occurrence of Resistance to Antibiotics in the Causative Agents of Bovine Mastitis

Veterinarni Medicina 39, 1994, 503-509

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. As can be seen from our results, surveys of the resistance of bovine mastitis-inducing bacteria to antibiotics need to be assembled, and rational principles of treatment that would guarantee the rotation of antibiotics should be employed

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