Total Coliform and Generic E. coli Levels, and Salmonella Presence in Eight Experimental Aquaponics and Hydroponics Systems: A Brief Report Highlighting Exploratory Data

Dosing Salmonella into poultryponics: Fate of Salmonella during treatment of poultry processing wastewater and irrigation of hydroponic lettuce

"Poultryponics" is a bioponics system that treats poultry processing wastewater (PPW) for hydroponic irrigation. Effective pathogen removal is an under-studied barrier to advancing bioponics technology. This study evaluated the system's capacity to manage high exogenous doses of three Salmonella serotypes commonly associated with poultry. The poultryponics treatment train, operating at ∼115 liters d-1, consisted of bioreactors (algal vs. bacterial), clarifiers, membrane filters, UV disinfection, water storage reservoir, and hydroponic grow beds. The fate of Salmonella spp. in the system was evaluated by analyzing water and lettuce samples for Salmonella contamination across three experimental stages: pre-inoculation (days 0-10), inoculation (days 11-20), and recovery (days 21-30). During the inoculation phase, bioreactors were spiked daily at levels significantly higher than those typically detected in PPW (<1 log10 CFU mL -1Salmonella). When challenged at 3 log10 CFU mL -1, the Salmonella levels observed in the algal and bacterial bioreactors were 0.6 and 1.4 log10 CFU mL -1, representing a 99.6% and 97.5% reduction, respectively (p = 0.03). UV disinfection eliminated Salmonella from water samples, with no Salmonella detection in lettuce. At the 5 log10 CFU mL -1 dosage, Salmonella counts in bioreactor effluent were reduced to approximately 3 log10 CFU mL -1 by day 15 of inoculation (99% reduction). However, as Salmonella dosage continued, removal efficiency decreased, with Salmonella detection after UV treatment but not in grow beds or lettuce. This study confirms the effectiveness of the poultryponics system in managing Salmonella under extreme contamination scenarios.

Longitudinal Survey of Aeromonas hydrophila and Foodborne Pathogens in a Commercial Aquaponics System

Aquaponic production of fresh produce is a sustainable agricultural method becoming widely adopted, though few studies have investigated potential food safety hazards within commercial systems. A longitudinal study was conducted to isolate and quantify several foodborne pathogens from a commercial, aquaponic farm, and to elucidate their distribution throughout. The survey was conducted over 2 years on a controlled-environment farm containing Nile tilapia (Oreochromis niloticus) and lettuce (Lactuca sativa). Samples (N = 1,047) were collected bimonthly from three identical, independent systems, and included lettuce leaves, roots, fingerlings (7-126 d old), feces from mature fish (>126 d old), water, and sponge swabs collected from the tank interior surface. Most probable number of generic Escherichia coli were determined using IDEXX Colilert Quanti-Tray. Enumeration and enrichment were used to detect Shiga toxin-producing E. coli (STEC), Salmonella enterica, Listeria monocytogenes, Aeromonas spp., Aeromonas hydrophilia, and Pseudomonas aeruginosa. Generic E. coli, STEC, L. monocytogenes, and S. enterica were not detected in collected samples. P. aeruginosa was isolated from water (7/351; 1.99%), swabs (3/351; 0.85%), feces (2/108; 1.85%), and lettuce leaves (2/99; 2.02%). A. hydrophila was isolated from all sample types (623/1047; 59.50%). The incidence of A. hydrophila in water (X2 = 23.234, p < 0.001) and sponge samples (X2 = 21.352, p < 0.001) increased over time.

Microbial Pathogens in Aquaponics Potentially Hazardous for Human Health

The union of aquaculture and hydroponics is named aquaponics-a system where microorganisms, fish and plants coexist in a water environment. Bacteria are essential in processes which are fundamental for the functioning and equilibrium of aquaponic systems. Such processes are nitrification, extraction of various macro- and micronutrients from the feed leftovers and feces, etc. However, in aquaponics there are not only beneficial, but also potentially hazardous microorganisms of fish, human, and plant origin. It is important to establish the presence of human pathogens, their way of entering the aforementioned systems, and their control in order to assess the risk to human health when consuming plants and fish grown in aquaponics. Literature analysis shows that aquaponic bacteria and yeasts are mainly pathogenic to fish and humans but rarely to plants, while most of the molds are pathogenic to humans, plants, and fish. Since the various human pathogenic bacteria and fungi found in aquaponics enter the water when proper hygiene practices are not applied and followed, if these requirements are met, aquaponic systems are a good choice for growing healthy fish and plants safe for human consumption. However, many of the aquaponic pathogens are listed in the WHO list of drug-resistant bacteria for which new antibiotics are urgently needed, making disease control by antibiotics a real challenge. Because pathogen control by conventional physical methods, chemical methods, and antibiotic treatment is potentially harmful to humans, fish, plants, and beneficial microorganisms, a biological control with antagonistic microorganisms, phytotherapy, bacteriophage therapy, and nanomedicine are potential alternatives to these methods.

Determination of Phylloplane Associated Bacteria of Lettuce from a Small-Scale Aquaponic System via 16S rRNA Gene Amplicon Sequence Analysis

Fresh vegetables harbour diverse bacterial populations on their surfaces which are important for plant health and growth. Information on epiphytic bacteria is limited to only a few types of vegetables and it is unknown how the lettuce epiphytic bacterial community structure may respond when a probiotic product is added to an aquaponic system. In this study, we evaluated lettuce growth and analysed epiphytic bacterial communities of lettuce based on metabarcoding analysis of the V3-V4 region of the 16S rRNA gene obtained from paired-end Illumina MiSeq reads. The addition of Bacillus probiotics resulted in a significant increase of nitrate and phosphate in the deep-water culture solution, as well as increased vegetative growth of lettuce. Metabarcoding analysis revealed that the most abundant phyla on lettuce leaf surfaces were Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. The in-depth bacterial composition analysis indicated that genera Chryseobacterium, Bacillus, Pantoea, Pseudoduganella, Flavobacterium, Paludibacter, and Cloacibacterium were dominant in leaf samples obtained from Bacillus-treated systems. Analysis of lettuce epiphytic bacterial communities of the fresh lettuce leaf surfaces also indicated the presence of food-borne pathogens belonging to the Shigella and Aeromonas genera, which were less abundant in the probiotic treated systems. This study provides the first characterization of the epiphytic bacterial community structure and how it can be modulated by the addition of a probiotic mixture to the nutrient solution of aquaponic systems.