Environmental

Oral

394794 - Assessment of seasonal variability, antibiotic resistance and the impact of storm event on streambed E. coli concentration in Skunk Creek, Big Sioux river, South Dakota

Tuesday, June 5
8:30 AM - 10:00 AM
Location: Lakeshore B
Co-Authors: Rachel McDaniel, Brookings, South Dakota – South Dakota State University; Bruce Bleakley, Brookings, SOuth Dakota – South Dakota State University

It has been observed that streambed sediment often contains more fecal indicator bacteria than water column as the sediment provides a more favorable environment for survival of bacteria. E. coli, a fecal indicator organism, is the number one cause for stream and river water quality impairments in South Dakota. Stream bottom sediments can be a major contributor of bacteria, including E. coli, to the water column. The objectives of this study are to evaluate the site variability of E. coli in stream bottom sediment as a source of bacteria to the water column, assess the antibiotic resistance (ABR) of selected E. coli isolates, and finally monitor E. coli concentration in the sediment to assess seasonal variability. The study area is Skunk Creek (Sk), a tributary to the Big Sioux River located in eastern South Dakota. Samples were collected from four monitoring sites, abbreviated Sk1, Sk2, Sk3 and Sk4. The results show the E. coli concentrations ranged from 20 cfu/g to 900 cfu/g. The lowest and highest E. coli counts observed in Sk4 and Sk3 monitoring sites, respectively. For evaluation of seasonal variability, three samples were collected from both edges and the middle of the stream for each monitoring site from May to October. In addition, samples were collected surrounding storm events to evaluate variability caused by flow changes. Results from this work are currently being analyzed. The modified Kirby Bauer method was used to assess ABR of selected E. coli isolates to penicillin (10 IU), ampicillin (10 µg), erythromycin (2 µg), tetracycline (30 µg) and sulfisoxazole (0.25 mg). The results indicate most isolates from Sk2 monitoring site were resistant to penicillin and erythromycin , 7/30 isolates were found to be susceptible to tetracycline, and most isolates were found to be susceptible to sulfisoxazole.

Sadia Salam

Graduate Research Assistant
South Dakota State University

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394794 - Assessment of seasonal variability, antibiotic resistance and the impact of storm event on streambed E. coli concentration in Skunk Creek, Big Sioux river, South Dakota



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