Q-250. Impact of Enrichment on the Recovery of Enteric Bacteria from Sediment Samples Collected from the North River

A. K. Graves, L. Liwimbi, D. Lindbo, B. Robinson, R. Coburn, C. Cahoon, D. Vaal, J. Lubbers;
North Carolina State Univ., Raleigh, NC.

The objective of this project was to determine the role sample enrichment on recovery of enteric bacteria from sediment samples collected from the North River. The North River runs parallel to the North River Community, Carteret County, North Carolina. The Community lies in the 100-year flood plain bordering shellfish sensitive waters and stuggles with septic system performance due to soil and site limitations. As a result septic systems, in addition to wildlife, may contribute to enteric bacteria load in the North River. Sediment samples (n=29) were collected from the North River and from drainage ditches adjacent to the North River. All samples were enriched for 24 hours at 37°C using Gram Negative Broth (GN), Luria-Bertani Broth (LB), Brain Heart Infusion Broth (BHI) and Pre-enrichment Broth (PEB). Salmonella isolates were recovered after enrichment by plating on Salmonella Shigella Agar (SSA), Xylose Lysine Deoxycholate Agar (XLD), and Brilliant Green Agar (BG). Escherichia coli isolates were recovered by plating on m-TEC Agar (TEC), fecal coliforms by m-FC Agar and Enterococcus isolates were recovered by plating on m-Enterococcus Agar (ENT). No bacteria were recovered from sediment samples plated on agar types prior to enrichment. GN Broth-enriched sediment samples had a statistically greater recovery rates per 1 gram of sediment at P<0.05 for all of the gram negative bacteria, regardless of the type of agar the samples were plated on. GN enrichment in combination with plating on BG produced the greatest recovery rate for Salmonella. Salmonella recoveries were 2.53 x 10-5, 5.30 x 10-4, and 3.32 x 10-5 for SSA, XLD, and BG respectively. Escherichia coli and fecal coliforms were recovered at 2.42 x 10-5 and 3.91 x 10-5 respectively. The Enterococcus recovery rate was greatest with the use of BHI (1.45 x 10-5) and LB (9.01 x 10-4) and were statistically greater at P<0.05 than recovery rates with the other enrichment broths. These results indicate recoveries of enteric bacteria from sediment samples are more efficient after enrichment.