ANTIBIOTIC RESISTANT BACTERIA MONITORING IN THE BLACK HAWK LAKE WATERSHED, IOWA

Manure produced by concentrated animal feeding operations (CAFOS) is commonly applied to surrounding agriculture fields as an agroeconomic practice to improve soil fertility and properly dispose of manure on-site. Antibiotics are used by many CAFOS to prevent or treat disease. Manure from antibiotic treated livestock contains low levels of undigested antibiotic metabolites that provide selective pressure and facilitate the spread of antibiotic resistance to the environment. This study aims to monitor total fecal indicator bacteria (FIB) (E. coli and enterococci) and tylosin and tetracycline resistant enterococci from drainage and runoff in a highly agriculturalized watershed. Samples will be collected at the catchment outlets with areas ranging from 547 acres to 1,988 acres. This is the scale which comparisons can be made between bacteria abundances from manured land with varying degrees of best management practices (BMPs). The eight sites encompass three surface runoff sites, two tile drainage outlets, two no-manure reference sites, and one public beach access site. Results of this study show elevated levels of E. coli and enterococcus in the watershed. Tetracycline resistant enterococcus was found to be more prevalent in the watershed than tylosin, though both were present at all monitoring sites. Surface and tile sites draining the sub-watershed with highest BMP implementation (87.5% of area) consistently show lower tylosin and tetracycline resistance fractions of enterococcus than the adjacent surface site draining a similarly sized sub-watershed with less BMP implementation (30% of area). Preliminary results indicate that BMPs may play a role in reducing total FIB and antibiotic resistance occurrences in agricultural runoff.