ARS | Publication request: "NATURAL" TETRACYCLINE RESISTANCE IN SWINE--ORGANIC AND FERAL PIG TALES

Submitted to: American Society for Microbiology Branch Meeting
Publication Type: Abstract Only
Publication Acceptance Date: October 16, 2003
Publication Date: October 16, 2003
Citation: STANTON, T.B., STOFFREGEN, W.C. "NATURAL" TETRACYCLINE RESISTANCE IN SWINE--ORGANIC AND FERAL PIG TALES. NORTH CENTRAL BRANCH OF THE AMERICAN SOCIETY FOR MICROBIOLOGY. 2003. ABSTRACT p. 7.

Technical Abstract: Important for assessing the success of programs to reduce antibiotic resistance in farm animals is knowing what levels of reduction are possible. The goal of this research was to determine baseline levels of tetracycline-resistant intestinal bacteria in swine not fed antibiotics. Fecal samples were obtained from ten organically-raised swine and from nineteen feral swine. Fecal bacteria were cultured aerobically on MacConkey agar (coliforms) and anaerobically on Me109M agar (Megasphaera elsdenii) or RTC agar (total anaerobes). The culture media contained 0, 16, or 64 mcg chlortetracycline (CTC)/ ml. Organic swine feces contained an estimated 6.7 x 10**6 coliforms/gm, with 27% insensitive to 64 mcg CTC/ml. Feral coliforms insensitive to CTC at 16 mcg/ml were undetectable (< 5,000 cfu/gm). From organic swine, 46% (264/540) of M. elsdenii isolates grew at 64 mcg CTC/ml, whereas none (0/91) from feral swine grew at 16 or 64 mcg/ml. At 64 mcg CTC/ml, 16% (9 x 10**9 cfu/gm) of the anaerobes from organic swine were insensitive to the antibiotic and 0.3% (3.2 x 10**6), from feral swine were insensitive. The tetracycline resistance determinants and the resistant bacterial species of organic swine were more diverse than those of feral swine. These findings indicate organically raised swine shed diverse tetracycline-resistant bacteria in high numbers. Tetracycline-resistant bacteria in feral swine feces are at least 1000-fold fewer.