Aquaponics is a sustainable agricultural method for the propagation of fish, microorganisms, and produce by harnessing the byproducts of one component as a nutrient source for the other. Recently, aquaponic farms have undergone increased scrutiny regarding the food safety of their products. This is due to limited research on the association of foodborne pathogens from fish and aquaponic water and the potential for produce contamination. The purpose of this study was to perform an initial evaluation of a commercial aquaponics farm to determine potential food safety hazards present within the system.
Over 2 years, a microbial evaluation was performed on a controlled environment aquaponics farm containing 3 recirculating systems. The fish tank contained Nile tilapia (Oreochromis niloticus) and lettuce (Lactuca sativa) was grown hydroponically in a deep water culture (DWC) grow bed. Samples (n = 1,044) were collected bimonthly from each system, including lettuce, roots, fingerlings (0-3 mo), fish (>3 mo), water, and sponge samples from the tank interior. Total plate count (TPC) was enumerated on Tryptic Soy Agar, while total coliform and generic Escherichia coli most probable number (MPN) were determined using IDEXX Colilert Quanti-Tray. Enumeration and enrichment were used to detect Shiga-toxigenic E. coli (STEC), Salmonella enterica, Listeria monocytogenes, Aeromonas hydrophilia, and Pseudomonas aeruginosa.
The average TPC in water (n = 351) and sponge (n = 351) samples were 4.59 and 6.06 log CFU/ mL, respectively. Generic E. coli, STEC, and L. monocytogenes were not detected from any of the collected samples. P. aeruginosa was isolated from water (4/351; 1.14%), sponge (3/351; 0.85%), fish gut (1/108; 0.93%), lettuce (2/99; 2.02%), and root (1/99; 1.01%) samples. Sponge (9/351; 2.56%) and water (7/351; 1.99%) samples collected from the fish tank and DWC were positive for S. enterica. A. hydrophila was isolated from all sample types (544/1044; 52.1%; Table 1). These results indicate that although common produce associated foodborne pathogens were not identified or had low presence in the aquaponics system, A. hydrophila was identified as a hazard in the system and may pose a risk for fish disease and produce associated foodborne illness.