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Diverse and abundant antibiotic resistance genes in Chinese swine farms

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  • Diverse and abundant antibiotic resistance genes in Chinese swine farms

    Diverse and abundant antibiotic resistance genes in Chinese swine farms

    December 31, 2012


    Antibiotic resistance genes (ARGs) are emerging contaminants posing a potential worldwide human health risk. Intensive animal husbandry is believed to be a major contributor to the increased environmental burden of ARGs. Despite the volume of antibiotics used in China, little information is available regarding the corresponding ARGs associated with animal farms.

    We assessed type and concentrations of ARGs at three stages of manure processing to land disposal at three large-scale (10,000 animals per year) commercial swine farms in China. In-feed or therapeutic antibiotics used on these farms include all major classes of antibiotics except vancomycins.

    High-capacity quantitative PCR arrays detected 149 unique resistance genes among all of the farm samples, the top 63 ARGs being enriched 192-fold (median) up to 28,000-fold (maximum) compared with their respective antibiotic-free manure or soil controls.

    Antibiotics and heavy metals used as feed supplements were elevated in the manures, suggesting the potential for coselection of resistance traits.

    The potential for horizontal transfer of ARGs because of transposon-specific ARGs is implicated by the enrichment of transposases—the top six alleles being enriched 189-fold (median) up to 90,000-fold in manure—as well as the high correlation (r2 = 0.96) between ARG and transposase abundance.

    In addition, abundance of ARGs correlated directly with antibiotic and metal concentrations, indicating their importance in selection of resistance genes. Diverse, abundant, and potentially mobile ARGs in farm samples suggest that unmonitored use of antibiotics and metals is causing the emergence and release of ARGs to the environment.

    More: PNAS

    This article contains supporting information online at

    The antibiotics come from all the major classes of antibiotics except vancomycin.

    Antibiotic Class - Antibiotic Used

    Tetracycline - Chlortetracycline
    Cephalosporin - Cefotaxime
    Aminoglycoside - Streptomycin
    Beta-Lactam - Penicillin
    Amphenicol - Florfenicol
    Tetracycline - Doxycycline
    Tetracycline - Oxycycline
    Other - Polymyxin E
    Macrolides - Kitasamycin tartrate
    Sulfonamides - Sulfamonomethoxine
    Beta-Lactam - Amoxycillin
    Quinolone - Enrofloxacin
    Macrolides - Ivermectin
    ?Addressing chronic disease is an issue of human rights ? that must be our call to arms"
    Richard Horton, Editor-in-Chief The Lancet

    ~~~~ Twitter:@GertvanderHoek ~~~ ~~~