Response of Bacterial Biofilms in Recirculating Aquaculture Systems to Various Sanitizers

ABSTRACT

Pathogenic microorganisms may be incorporated into biofilms found in aquaculture systems, causing recurring exposure to potential disease agents. Aerobic plate counts, the presence of Enterobacteriaceae, and the presence of Escherichia coli, modified to express a green fluorescent protein (GFP E. coli), was used to evaluate the effectiveness of various sanitizers in decreasing bacterial incorporation into newly generated biofilms in recirculating aquaculture systems. Disks of Buna-N rubber, polyvinyl chloride (PVC), chlorinated PVC, glass, fiberglass, and stainless steel were placed in aquariums stocked with Nile tilapia, Oreochromis niloticus. The effectiveness of water, an alkaline cleanser, sodium hypochlorite, a quaternary ammonium compound, or peracetic acid as a sanitizer was evaluated on each substrate by enumerating total plate counts, GFP E. coli, and Enterobacteriaceae. Sodium hypochlorite and peracetic acid were the most effective sanitizers, with an overall percentage reduction of GFP E. coli of approximately 2 logs₁₀. The quaternary ammonium compound was moderately effective, 1 log₁₀, against the target organisms. Water demonstrated a 2 log₁₀ reduction of the total plate count, suggesting that some mechanical cleaning was achieved. The type of material used as substrate for the biofilm had no significant (P > 0.05) effect on the effectiveness of the sanitizers.

KEYWORDS:

• Aquaculture
• bacteria
• biofilms
• E. coli
• green fluorescent protein
• pathogen
• fish

ACKNOWLEDGEMENTS

This project was funded by a scholarship from the National Fisheries Institute, Inc., Arlington, Virginia; Virginia Sea Grant College Program; the Commercial Fish and Shellfish Technologies (CFAST) Program of the Virginia Polytechnic Institute and State University; and NOAA (Grant Number NA96RG0025). The views expressed in this article are those of the author and do not reflect the official policy of the Department of the Army, Department of Defense, or U.S. government.

Notes

1. Use of trade or manufacturer's name does not imply endorsement.