THE PERSISTENCE OF FECAL-BORNE ANTIBIOTICS IN SOIL

One aspect of the use of antibiotics in animal agriculture, which to d ate has received modest attention, concerns the effects of antibiotics excreted by animals upon the environment. The persistence of 7 antibi otics that are commonly used in feeds was studied in a typical agricul tural soil. The antibiotics studied were bacitracin (BAC), penicillin (PEN), streptomycin (STR), tylosin (TYL), bambermycins (BAM), erythrom ycin (ERY), and chlortetracycline (CTC). The level incorporated into t he soil with feces was 5.6 mu g antibiotic/g sail. After incubation in soil for 30 days at 30 degrees C, 44% of CTC and 23% of BAC remained; however, no detectable amounts of NL, ERY, BAM, STR, and PEN remained . At 20 degrees C, 88% of CTC, 33% of BAC, and 25% of ERY remained aft er 30 days; however, no STR, BAM, TYL, and PEN could be found. At 4 de grees C, essentially ail of the CTC, ERY, and BAM; 23% of BAC; and 40% of TYL remained after 30 days; however, PEN and STR were undetectable .