Almost all of the E.coli isolates found by researchers in samples of runoff and sediment from California’s Santa Ana River Watershed are resistant to antibiotics. U.S. Department of Agriculture (USDA) researchers studying the origin of pathogenic contamination in waterways set out to discover what type of land use accounts for the largest level of contamination. They found that in some parts of California, runoff from urban areas contributes more pathogenic contamination to waterways than agricultural runoff does. But they also found a lot of antibiotic resistance.
Mark Ibekwe, led a team of scientists from the USDA’s Agricultural Research Service Salinity Laboratory in Riverside, Calif. who collected 450 water and sediment samples from 20 sites throughout the mid-section of the Santa Ana River Watershed. The sites included urban areas, livestock feeding areas, parks, National Forests, and three wastewater treatment plants.
The team extracted E. coli from each of the samples identifying 600 isolates of the bacteria. They found that the greatest variety of isolates in runoff came from urban areas or human activities, not livestock.
The scientists also found that most of the 600 isolates were resistant to antibiotics. Between 88 and 95 percent of the isolates were resistant to rifampicin, and roughly 75 percent were resistant to tetracycline. Almost a quarter of the isolates tested showed resistance to as many as seven antibiotics.
Antibiotic resistance is a major problem in treating bacterial infections including foodborne illnesses. It contributes to longer hospital stays and higher mortality rates, according to the Centers for Disease Control and Prevention (CDC).
