Sensitivity of selected mastitis pathogens to antimicrobial agents

Abstract

Mastitis represents a big problem in modern cattle production, both in economic terms and in terms of diagnostic. Direct economic losses for the manufacturers occur due to reduction of milk production, changed composition of the milk, medical expenses, loss of one or more quarters of the udder, the withdrawal period and higher expenditure of labor. The greatest damages in dairy production are caused by subclinical (invisible) inflammation. The aim of this study was to determine the sensitivity of some bacterial mastitis pathogens to antimicrobial agents in the compositions for the treatment of mastitis that are used in the Republic of Croatia. Pathogens which causes mastitis were isolated on esculin blood agar culture medium and subjected to a sensitivity analysis on eight antimicrobials. Highest sensitivity of Staphylococcus aureus strains was determined to amoxicillin with clavulanic acid and cefoperazone, while the distinct resistance was observed to penicillin and ampicillin (almost 100 %). Also it has been determined a relatively high efficiency of ampicillin (96.1 %), amoxicillin with clavulanic acid (94.1 %) and penicillin (92.8 %) on the strains of Streptococcus uberis, while the lowest sensitivity, bacteria have had on streptomycin. According to results of the analysis, it is evident that a growing number of bacteria developed resistance to certain antimicrobial agents.