Organic Poultry Farmers Reduce Antibiotic Resistant Bacteria

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A recent Washington Post article: Organic farming reduces resistance of bacteria to antibiotics, study finds (By Rob Stein) reported that “Poultry farmers who adopt organic practices and stop giving their birds antibiotics significantly reduce the resistance of bacteria to antibiotics in their flocks…”

The study cited in this article is available from the open access Journal: Environmental Health Perspectives at: https://ehp03.niehs.nih.gov/article/fetchObjectAttachment.action;jsessionid=F3814924DCF05734A7C45EF6D85CC0FD?uri=info%3Adoi%2F10.1289%2Fehp.1003350&representation=PDF and the abstract is posted below.

Citation: Sapkota AR, Hulet RM, Zhang G, McDermott P, Kinney E, Schwab K, et al. 2011. Lower Prevalence of Antibiotic-resistant Enterococci On U.S. Conventional Poultry Farms That Transitioned to Organic Practices. Environ Health Perspect :-. doi:10.1289/ehp.1003350

Article Abstract: Background: In U.S. conventional poultry production, antimicrobials are used for therapeutic, prophylactic and non-therapeutic purposes. Researchers have shown that this can select for antibiotic-resistant commensal and pathogenic bacteria on poultry farms and poultry-derived products. However, no U.S. studies have investigated on-farm changes in resistance as conventional poultry farms transition to organic practices and cease using antibiotics.

Objective: To evaluate the prevalence of antibiotic-resistant Enterococcus on U.S. conventional poultry farms that transitioned to organic practices.

Methods: Poultry litter, feed, and water samples were collected from 10 conventional and 10 newly organic poultry houses in 2008 and tested for Enterococcus. Enterococcus (n=259) was identified using the Vitek ®Compact 2 System, and tested for susceptibility to 17 antimicrobials using the Sensititre^™ microbroth dilution system. Data were analyzed using SAS v9.2 and statistical associations were derived based on generalized linear mixed models.

Results: Litter, feed and water samples were Enterococcus-positive. The percentages of resistant E. faecalis and resistant E. faecium were significantly lower (p<0.05) among isolates from newly organic versus conventional houses for two (erythromycin and tylosin) and five (ciprofloxacin, gentamicin, nitrofurantoin, penicillin and tetracycline) antimicrobials, respectively. Forty-two percent of E. faecalis isolates from conventional poultry houses were multi-drug resistant (MDR) (to≥3 antimicrobial classes) compared to 10% of isolates from newly organic houses (p=0.02), and 84% of E. faecium isolates from conventional houses were MDR compared to 17% of isolates from newly organic poultry houses (p<0.001).

Conclusions: Our findings suggest that the voluntary removal of antibiotics from large-scale U.S. poultry farms that transition to organic practices is associated with a lower prevalence of antibiotic-resistant and MDR Enterococcus.