Some antibiotics important for humans are fed to nonorganic chickens to speed growth or prevent or treat illness. But bacteria may evolve to become immune to antibiotics, at which point the drugs become less effective in treating people. We took 53 salmonella samples and 103 campylobacter samples from chickens and determined what percentage of samples resisted antibiotics that usually work against those pathogens. "Resistant" indicates the percentage of bacteria that could survive a normal dose of the drug. Each color represents a class of antibiotics. Within classes, drugs are in alphabetical order.