Isolate-level prevalence of resistance among E. coli isolates. The percentage of resistant isolates is depicted for each antibiotic tested. Resistance is grouped by classes, separated by lines, in the order of: aminoglycosides, β-lactam/β-lactam inhibitors, cephems, folate synthesis inhibitors, macrolides, penicillins, phenicols, quinolones and tetracyclines. GEN, gentamicin; KAN, kanamycin; STR, streptomycin; AMC, amoxicillin/clavulanic acid; CRO, ceftriaxone; FOX, cefoxitin; TIO, ceftiofur; SXT, trimethoprim/sulfamethoxazole; FIS, sulfisoxazole; AZM, azithromycin; AMP, ampicillin; CHL, chloramphenicol; CIP, ciprofloxacin; NAL, nalidixic acid; TET, tetracycline.