Backyard poultry farming: the cause of antimicrobial resistance in developing countries

Small-scale broiler chicken farms certainly provide income and access to animal proteins for poor rural populations, but they also have a negative impact on human health—a direct consequence of the development of antimicrobial resistance, which was previously extremely rare in isolated regions. For example, a study conducted in Ecuador by the University of Michigan revealed high levels of resistance to cefotaxime, a bactericidal antibiotic in the third-generation cephalosporin class, which belongs to the beta-lactam family.   The researchers studied populations of Escherichia coli with antibiotic resistance in broiler chickens, free-range backyard chickens, and children living in rural areas of northwestern Esmeraldas, in Ecuador, where levels of antibiotic resistance to third-generation antibiotics clinically significant for humans and animals—such as cefotaxime—had historically been very low. They discovered that a resistance gene—previously isolated in broiler chickens—was also present in backyard chickens and in children. Historically, resistance to cefotaxime in humans has been very rare in this region of the world. The authors therefore suggest that the gene in question originates from broiler chickens. For the study, the researchers collected bacterial samples from farm-raised broiler chickens from 10 families—fed antibiotics and raised in a cooperative—as well as from backyard chickens roaming freely both inside and outside homes. They also sampled backyard chickens from 10 households that did not raise broiler chickens. Two years later, the researchers collected samples from children in the various farming communities. The study, published in the journal of the American Society of Tropical Medicine and Hygiene, revealed high levels of resistance to cefotaxime among farm-raised broiler chickens: 66% were resistant to this critically important antibiotic for both poultry and humans. It also showed an increase in resistance to cefotaxime over time in backyard chickens raised without antibiotics (rising from about 2% to nearly 18%), and finally, the production of extended-spectrum beta-lactamases (CTX-M) by human and avian bacteria, suggesting the emergence of transmission from chickens to humans. Small-scale poultry farming accounts for the majority of global chicken production. In many developing countries, this farming method is essential for ensuring food safety and economic security for rural populations. However, the authors argue that greater attention must be paid to the health aspects of this local poultry production, particularly to counter the transmission of pathogens responsible for diarrheal diseases within communities, as well as the development of antimicrobial resistance. The results of this study highlight a recurring issue in research on meat production in developing countries: while family-based chicken farming helps reduce poverty and food insecurity among populations, it has direct adverse consequences for public health through the spread and selection of antibiotic resistance in a rural and underdeveloped environment.