Antimicrobial susceptibility of intestinal bacteria from Swiss poultry flocks before the ban of antimicrobial growth promoters

From the crop and the caecum of Swiss broilers slaughtered between November 1997 and January 1998, Escherichia coli, enterococci, staphylococci, lactobacilli and Campylobacter species were isolated. After identification to the genus or species level, their minimal inhibitory concentrations (MIC's) for several clinically used antimicrobial agents were determined with the E-Test stripes and compared to those from studies in other European countries. All strains of Enterococcus faecalis (n = 38), E. faecium (27), staphylococci (n = 39) and lactobacilli (n = 14) showed a hundred percent resistance against bacitracin which was included in the feed of the mother animals, but not in the feed of the investigated animals. E.coli strains (n = 60) showed higher resistance incidences than in comparable studies from Finland and Denmark, but lower than those in studies from Italy and Germany. In staphylococci, low resistance rates were observed. A high susceptibility of the 13 Campylobacter jejuni strains was found against therapeutically used antimicrobials. These data can be used as a baseline to determine antibiotic resistance rates after implementation of the growth promotor ban in 1999 in Switzerland.