engleski

Antimicrobial susceptibility of milk bacteria from healthy and drug-treated cow udder

The aim of this study was to evaluate antimicrobial susceptibility of milk microbiota, considering udder health status and drug treatment history. Composite milk samples were taken aseptically from healthy cows without any signs of mastitis (n=17) and drug- treated cows with cured mastitis (n=19). Antimicrobial susceptibility testing was performed in 56 enterococci, 30 Escherichia coli, 24 enterobacteria and 94 staphylococci. Depending on bacterial group or species, the following antibiotic disks were used – ampicillin, rifampin, chloramphenicol, linezolid, tetracycline, erythromycin, nitrofurantoin, vancomycin, penicillin, trimethoprim, cefoperazone, kanamycin, trimethoprim/sulfamethoxazole, nalidixic acid, ciprofloxacin, gentamicin, teicoplanin, sulfonamides, levofloxacin, clindamycin and amoxicillin/clavulanic acid. The occurrence of multiresistant E. coli and staphylococci was significantly higher (P<0.05) in milk of drug- treated cows. The percentage ratio (drug- treated: healthy udders) of multiresistant E. coli was 56.3:0, enterobacteria 57.14:30 and staphylococci 56.5: 4.8. There was no significant difference (P>0.05) between the prevalence of multiresistant enterococci in the milk of healthy cows and cows with cured mastitis (87.2:73.7). High prevalence of resistance in enterococci isolated from milk samples of healthy cows could be result of animal cohabitation and cross-contamination.

antimicrobial resistance; milk; enterococci; udder health

This research was supported by University of Zagreb, Program Contract 2, project “Antimicrobial resistance of pathogens from food of animal origin”.