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In vitro activity of 10 antimicrobial agents against bacteria isolated from cows with clinical mastitis
  1. V. Guérin-Faublée, DVM, PhD1,
  2. G. Carret, PhD2 and
  3. P. Houffschmitt, DVM3
  1. 1 Département de Santé Publique Vétérinaire, Ecole Nationale Vé té rinaire de Lyon, BP 83, 69280 Marcy l'étoile, France
  2. 2 Faculté de Médecine Lyon sud, UMR CNRS 5558, BP 12, 69921 Oullins cedex, France
  3. 3 Intervet SA, rue Olivier de Serres, Angers Technopole, BP 17144, 49071 Angers cedex, France


The susceptibility of 495 strains of bacteria, recently isolated in France from cows with clinical mastitis, to 10 antimicrobial agents - penicillin G, cloxacillin, oxacillin, cephalexin, cefazolin, cephapirin, cefquinome, neomycin, ampicillin and colistin - was determined by measuring their minimum inhibitory concentrations (MICs). Overall, the levels of resistance were very low except for staphylococci and penicillin G. The 167 streptococcal strains were susceptible to all of the β-lactams tested, but six (3.6 per cent) were highly resistant to neomycin. Of the 171 staphylococcal isolates, 36.2 per cent were resistant to penicillin G, one strain of Staphylococcus sciuri was classified as methicillin-resistant, but they were all susceptible to neomycin. None of the 122 strains of Escherichia coli was resistant to colistin, but 12 had high MIC values for one or more of the cephalosporins.

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