A Survey of Antibiotic Resistance Among Coliform Bacteria Isolated from the Missouri River

The prevalence of antibiotic resistant microorganisms in the environment is not well known but could represent a challenge to maintaining public health in the future. Fecal waste from livestock facilities, where antibiotics are routinely used, is recognized as a significant source of pollution to surface waters in the United States. We collected water from the Missouri River across a winter to spring seasonal change in order to survey the density of coliform bacteria. We tested bacterial isolates for resistance to penicillin, tetracycline, ampicillin, erythromycin, and ciprofloxacin. Coliform density in Missouri River water generally was high throughout the study (0-405 cfu 100 ml·1). The highest values corresponded to a precipitation event that likely enhanced surface runoff. The lowest coliform densities corresponded to an increase in river flow volume caused by the release of reservoir water upstream. Of the isolates tested, none were sensitive to penicillin or erythromycin, both anti-microbial drugs that are normally ineffective against Gram negative bacteria such as coliforms. No isolates were resistant to ampicillin or ciprofloxacin. 12.5% percent of the isolates were resistant to tetracycline, however. All isolates were identified through biochemical testing as Escherichia coli. Our results demonstrate that antibiotic resistant coliforms were present in the Missouri River at the time of our study. Whether the source of these microorganisms is an environmental reservoir or livestock source needs to be determined.