engleski

Prevalence And Resistance Trends Of Causative Agents Of Bovine Subclinical Mastitis Over A 10-Year Period In Northwestern Croatia

Objectives: The aim of this study was to determine causative agents of bovine subclinical mastitis (BSM) over a 10-year period (2001-2010), their prevalence and in vitro resistance to antibiotics. Additionally, we monitored the influence of farm size and management system changes during the observation period on the incidence of BSM and effectiveness of antibiotic therapy. Materials and Methods: Milk samples for microbiological examination were taken from udder quarters of cows without clinical symptoms of mastitis kept at dairy farms in northwestern Croatia that were positive to California or Zagreb mastitis reagents. Prior to sampling, the first milk steams were discarded and the next were examined with the mastitis reagent. When positive reactions where obtained with either mastitis reagent (colour or density change), teat ends were disinfected with cotton swabs soaked in 70% alcohol and new milk samples were collected. The samples were transported in cooled refrigerators to the laboratory as soon as possible. Microbiological agents and antibiograms were performed at the Croatian Veterinary Institute, Krizevci, Croatia according to common standard protocols. A total of 426 milk samples from dairy cows were examined for the presence of BSM causative agents. Results: From the total collected samples (n=426), the prevalence of causative agents of BSM was recorded as follows: 44.70% Staphylococcus aureus, 24.70% Staphylococcus sp., 9.64% Streptococcus dysgalactiae, 4.47% Streptococcus agalactiae, 3.76% Streptococcus sp., 6.82% Escherichia coli, 1.88% Enterobacter sp., 0.70% Pseudomonas aeruginosa, 2.35% Bacillus sp., 0.47% Candida sp. and 0.23% yeasts. The prevalence of streptococcal BSM decreased from 30.77% to 10.77% during the 10- year observation period, while BSM caused by Staphylococcus spp. increased from 42.31% to 80.00%. Commercial discs were used to perform the antibiogram with the following antibiotics and chemotherapeutics: amoxicillin/klavulanic acid, ampicillin, cefoperazone, cephalexin, cefquinom, enrofloxacin, kloxacillin, lincomycin, neomycin, novobiocin, penicillin, streptomycin, sulphonamide/trimethoprim and tetracycline. After prolonged use of some of these antibiotics for intramammary treatment of BSM, bacterial resistance developed. Namely, only 7.69% of all bacteria isolated were resistant to amoxicillin and klavulanic acid in the first year of the study (2001), while this increased to 38.46% after10 years. Resistance to some antibiotics increased from 2001 to 2010 was as follows: cefaperazone (0% vs. 15.38%), cephalexin (0% vs. 40.00%), cefquinom (0% vs. 21.53%) and penicillin (19.23% vs. 49.23%). Conclusions: It could be concluded that during the 10-year observation period, the incidence of BSM caused by Staphylococci spp. was significantly increased, as was the resistance of bacteria to certain antibiotics, as a consequence of their frequent use at larger dairy farms (more than 50 cows per farm) and the easier spread of bacteria within and between larger herds in comparison to the beginning of the study when dairy farms in northwestern Croatia were predominately smaller (1-10 cows per farm).

Prevalence And Resistance Trends Of Causative Agents Of Bovine Subclinical Mastitis Over A 10-Year Period In Northwestern Croatia

nije evidentirano