Antibiotic-resistant Bacteria from Feces of Livestock, Farmyard Manure, and Farmland in Japan—case report—

Abstract

We examined the distribution of antibiotic-resistant bacteria by analyzing 19 samples of feces of livestock, solid farmyard manure (FYM), soil from arable fields and orchards treated with FYM or not, and forest soils. Bacteria resistant to ampicillin, vancomycin, kanamycin, chloramphenicol, rifampicin, and tetracycline were enumerated by the dilution plate method at a rate of 50 mg l-1. The total numbers of antibiotic-resistant bacteria in swine or poultry feces were the same as or up to eight orders of magnitude lower than the total numbers of culturable bacteria. The occurrence of antibiotic-resistant bacteria in the poultry feces increased with the use of antibiotics as feed additives. The occurrence of antibiotic-resistant bacteria was much lower in FYM samples than fecal samples with some exceptions. Of the soil samples, only that to which solid swine FYM at 40 t ha-1 had been applied yearly for more than 10 years had significantly higher numbers of total and antibiotic-resistant bacteria than the upland soil that had not been treated with FYM. Resistant isolates from fecal samples showed a broad range of multi-drug resistance (MDR), but those from forest soil had a narrow-range MDR, suggesting that the use of antibiotics as feed additives influences the occurrence of broad-range MDR.