Since the 1980s, Tauxe says, outbreaks of resistant pathogens have been linked to livestock. In some cases, resistant bacteria transmitted through the food chain or from contact with animals cause an increase in morbidity and mortality among humans. Other “silent infections” occur when a patient taking an antibiotic for another reason are exposed to pathogens resistant to that antibiotic, leading to disease that otherwise might not occur.
Tauxe offered several examples of resistance linked to antibiotic use in livestock, such as resistant strains of Campylobacter jejuni appearing soon after poultry producers began using the antibiotic ciprofloxacin.
In another example, poultry producers in Quebec voluntarily stopped injecting eggs with Ceftiofur when resistant strains of Salmonella Heidelberg became common in poultry meat. After they stopped using the product, the incidence of resistant pathogens dropped significantly.
In human medicine, Tauxe says it had been routine to treat all cases of shigella with ciprofloxacin, and to use the drug in prophylaxis to prevent the disease among family members or classmates of infected children. Recently, physicians have moved away from antibiotic use for prevention of shigella infections, stressing sanitation instead, and limited prescriptions to severe cases, and the incidence of resistant pathogens has declined.
Antibiotic resistance presents a substantial challenge, Tauxe says, but it is possible to reverse the trend in many cases if physicians and veterinarians engage in efforts to assure judicious use.
The CDC provides more information on their drug-resistance website.