2.2 Antibiotics
APEC strains are resistant to most antibiotics, with only a few carbapenems still effective—although resistance to imipenem has started appearing. These strains often withstand drugs like ampicillin, tetracycline, trimethoprim, sulfamethoxazole, and streptomycin. The high resistance to critical antibiotics, especially β-lactams and colistin, raises serious concerns about spreading these resistant bacteria and genes to humans through the food chain.8 The US and EU restrict non-therapeutic antibiotic use for growth and limit critical antibiotics in animal farming to help reduce antibiotic resistance risks.9 A study showed chickens treated with enrofloxacin showed better feed efficiency, lower death rates, healthier organs, and less bacterial presence than those given oxytetracycline. Oral enrofloxacin was especially effective, providing strong protection within 2 hours and lasting all day.10 Colistin, a last-resort antibiotic for Gram-negative infections, becomes more effective and less prone to resistance in E. coli when combined with small molecule adjuvants that target the pmrAB system.11