Abstract :
Antibiograms of selected mastitis pathogens, performed during the decade 1995–2004, were retrospectively analysed in order to
evaluate antimicrobial resistance and determine whether resistance changed over time. Results of 2763 strains of Staphylococcus
aureus, coagulase negative staphylococci, Streptococcus uberis and Escherichia coli, against penicillin, ampicillin, oxytetracycline,
kanamycin and streptomycin are discussed. Strains were isolated in clinical milk samples from sheep suspected of mastitis. The
evolution over time of resistance was evaluated by means of logistic regression analysis. The resistance of staphylococci to penicillin
appeared to be lower than those usually reported (4.1% of resistant strains in S. aureus; 15.3% for CNS). Higher rates of resistance
were observed for aminoglycosides, relevant for S. uberis (84.5% for kanamycin and 92.5% for streptomycin) and S. aureus (14.6%
for kanamycin and 63.3% for streptomycin). Overall resistance appeared to confirm the lower resistance in ovine pathogens than in
bovine ones. Logistic regression highlighted no trends to increase for resistance over time.
© 2007 Elsevier B.V. All rights reserved.
