Phenotypic and genotypic characterization of antimicrobial resistance in German Escherichia coli isolates from cattle, swine and poultry.
OBJECTIVE
Phenotypic and genotypic characterization of the antimicrobial resistance of German Escherichia coli strains isolated during 1999-2001 from cattle, swine and poultry.


METHODS
Three hundred and seventeen isolates were tested for their resistance to 17 antimicrobial agents by broth microdilution. Resistant strains were screened by molecular methods for resistance genes, integrons and mutations in quinolone-resistance determining regions.


RESULTS
Resistance was found in 40% and multiresistance in 32% of the strains. The resistance was significantly higher in isolates from poultry (61%) and swine (60%) than from cattle (25%) (P < 0.01). The most prevalent resistances were to sulfamethoxazole, tetracycline, streptomycin, ampicillin and spectinomycin (30-15%). For each antibiotic, the predominant resistance genes were: ampicillin, blaTEM1-like (92%); chloramphenicol, catA (68%) and cmlA1-like (36%); gentamicin, aac(3)-IV (60%); kanamycin, aphA1 (100%); streptomycin, aadA1-like (61%) and strA/B (59%); sulfamethoxazole, sul2 (66%), sul1 (42%) and sul3 (14%); tetracycline, tet(A) (66%) and tet(B) (42%); and trimethoprim, dfrA1-like (77%), dfrA17 (13%) and dfrA12 (7%). Class 1 integrons were found in 30% of the strains. They carried dfrA1-aadA1a (40%), aadA1a (29%), sat1-aadA1a (16%), dfrA17-aadA5 (11%), oxa1-aadA1a (5%) and dfrA12-aadA2 (3%). Eleven percent of the strains were resistant to nalidixic acid. Of these, 61% presented a reduced susceptibility to ciprofloxacin (MIC = 0.12-2 mg/L) and single mutations in gyrA or gyrA and parC genes, and 39%, full resistance to ciprofloxacin (MIC > or = 4 mg/L) and double and single mutations in gyrA and parC, respectively.


CONCLUSIONS
The study gives baseline information on the magnitude of the resistance problem and its genetic background in contemporary German E. coli from food-producing animals.
Guerra
Beatriz
B
National Salmonella Reference Laboratory (Berlin), Federal Institute for Risk Assessment (BfR), P.O. Box 480447, D-12254 Berlin, Germany.
Junker
Ernst
E
Schroeter
Andreas
A
Malorny
Burkhard
B
Lehmann
Simone
S
Helmuth
Reiner
R
D019943:Amino Acid Substitution; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000382:microbiology*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology* / Q000662:veterinary*; D005798:Genes, Bacterial / Q000235:genetics; D005838:Genotype; D005858:Germany / Q000453:epidemiology; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D011159:Population Surveillance; D011201:Poultry Diseases / Q000453:epidemiology / Q000382:microbiology*; D018570:Risk Assessment; D013553:Swine Diseases / Q000453:epidemiology / Q000382:microbiology*