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