Fig. 3

Antibiotic resistance prevalence among E. coli isolates contaminating retail brands of chicken meat. Each bar represents a unique brand of chicken, bars are color coded by production category, i.e., conventionally raised (CON), organically raised (ORG), or “raised without antibiotics” (RWA). The horizontal red line indicates the average resistance prevalence across all brands and categories for each antibiotic. Each isolate was tested against: ampicillin (AMP), ampicillin-sulbactam (SAM), cefazolin (CFZ), cefoxitin (FOX), ceftriaxone (CRO), ciprofloxacin (CIP), nalidixic acid (NAL), gentamicin (GEN), tetracycline (TET), trimethoprim-sulfamethoxazole (SXT), amikacin (AMK), and imipenem (IPM). Multidrug resistance (MDR) was defined as resistance to three or more classes of antibiotics. None of the isolates tested were resistant to amikacin (AMK) or imipenem (IPM), which are excluded from the figure. The prevalence of antibiotic resistance, and MDR, was compared across all brands within each production category using the two-tailed Fisher’s exact test. All brands were included in the statistical analysis (Additional file 1: Table S1); however, only brands with more than 20 isolates are included in the figure. (*** P < 0.001, **P < 0.01, * P < 0.05)