During routine microbiological examination of milk samples from dairy cows without clinical signs of mastitis, samples of 231 dairy cows from 12 herds were investigated for the presence of coagulase-negative staphylococci (CNS). The predominant species, Staph. chromogenes and Staph. haemolyticus, were further characterized by antibiotic susceptibility testing and by pulsed-field gel electrophoresis (PFGE). Considerable resistance to ampicillin and penicillin was observed in both species. Isolates with identical or highly similar PFGE profiles were detected at the herd level despite a marked heterogeneity seen for both species. On the basis of somatic cell count, absence of clinical signs of inflammation and heterogeneity of genotypes, we assume that CNS isolated in this study could not be considered as important causative agents of the bovine mammary gland inflammation.
A review of the prevalence and mechanisms of the multiple antimicrobial resistance of Campylobacter in the food chain is given, with the emphasis on non-specific efflux pumps which are involved in bacterial reduced susceptibility and/or resistance against antibiotics and other unrelated antimicrobials, e.g. bile salts. For the first time the synergistic antimicrobial activity of some plant compounds (e.g. EGCG) which acts as an inhibitor of the efflux pump CmeB is presented as a challenge to develop efficient protection against antibiotic and/or bile salt resistant Campylobacter strains.