Effect of aquaponic water and substratum material on biofilm formation by Aeromonas hydrophila

Abstract

Aeromonas hydrophila is a zoonotic pathogen causing illness in fish and susceptible humans. This emerging pathogen has been isolated within aquaponic systems and could cause disease in fish and a hazard to humans consuming aquaponic produce. This study determined whether A. hydrophila from an aquaponic farm could form biofilms in aquaponic water and on materials used in these systems. A. hydrophila biofilm biomass and cell density in aquaponic water were evaluated by crystal violet staining and culture-based enumeration. Biofilm biomass and biofilm cell density were affected by the water source and A. hydrophila isolate (P < 0.05). A. hydrophila formed the most biomass from the beginning of deep-water culture (BDWC) water (OD570 0.202 ± 0.066) and the least from the end of deep-water culture (EDWC) water (OD570 0.140 ± 0.036; P < 0.05). Enumerated A. hydrophila from the biofilm varied among water sources; the fish tank water supported the greatest cell density (7.04 ± 0.71 log CFU/mL) while the EDWC supported the lowest cell density (6.76 ± 0.83 log CFU/mL). Biofilm formation was also evaluated on aquaponic materials such as nylon, polyvinyl chloride, polyethylene liner, bead filter, and foam. Biofilm formation on the liner had the greatest population (2.39 ± 0.022 log CFU/cm2), and the bead had the least (0.64 ± 0.039 log CFU/cm2; P < 0.05). Pathogenic organisms, such as A. hydrophila, may pose a greater risk to produce harvested from the BDWC and MDWC due to greater biofilm formation.