Investigation of Bacteria and Fish Pathogenic Bacteria Found in Freshwater Aquaponic System

Abstract

Bacteria are very vital organisms in aquaponic system decomposing and converting the toxic components of the fish waste into usable vegetable nutrients; however, some unwanted bacteria could cause fish diseases. The purposes of this research were to compare the amount of bacteria in water from aquaponic catfish cultured in different stocking densities and Denaturing Gradient Gel Electrophoresis (DGGE) of Polymerase Chain Reaction (PCR)-amplified 16S rDNA was applied to characterise the bacterial populations. Three different stocking densities; 80, 100 and 120 fish/m 2 of hybrid catfish were cultured in aquaponic system. Each treatment contained 3 replications; Treatment 1, 360 catfish (80 fish/m 2 , without lettuce); Treatment 2, 360 catfish (80 fish/m 2 , without lettuce); Treatment 3, 450 catfish (100 fish/m 2 ); and treatment 4, 540 catfish (120 fish/m 2 ). This research was conducted for 4 months. Water was sampled two times before fish stocking, it was found that the number of bacteria in the first week were higher than the third week. The average number of bacteria in water from treatment 1, 2, 3 and 4 were (2.49 ± 0.40) ×10 7 , (2.43 ± 0.23) ×10 Colonies forming unit (CFU)/ml respectively. According to four-time samplings after catfish were stocked, the average number of bacteria in water from treatment 1, 2, 3 and 4 were (1.85 ± 0.53) ×10 7 CFU/ml respectively. There were no differences in bacterial counts among treatments (p > 0.05). In addition, no significant difference was observed in the number of bacteria in filter tanks (p > 0.05) and the number were quite similar to the ones in catfish tanks. Aeromonas hydrophila and Flavobacterium columnare infected catfish at the beginning of the experiment; however, it got better and no more death found after acclimation. The DGGE analysis of PCR-amplified 16S rDNA fragments revealed that bacterial populations in water were dominated by Aeromonas spp., Pseudomonas spp. and Staphylococcus spp. Antibiotic sensitivity test indicated that enrofloxacin might be the best option for bacterial infection treatment. The results indicate that aquaponic system could reduce the wastewater from catfish culture; however, maintaining a good water quality environment for fish culture should take into account.

Microbial Pathogens in Aquaponics Potentially Hazardous for Human Health

“…The genus Staphylococcus, also found in aquaponics by Chitmanat et al [37], consists of a number of species, of which S. aureus, S. epidermidis, and S. saprophyticus are the most frequently associated with human infection [58]. S. aureus is both a commensal bacterium and a human pathogen causing bacteremia and infective endocarditis as well as osteoarticular, skin and soft tissue, pleuropulmonary, and device-related infections [59].…”

“…and Listeria monocytogenes in aquaponic water and the contaminated water did not lead to internalization of Shiga toxin-producing E. coli into the roots, leaves, and fruit of the lettuce, basil, and tomato plants studied. Also, while some authors reported the presence of E. coli and Salmonella in aquaponic systems [19,37], others did not find them [6,21]. Several investigations did not find one or more of the dangerous human pathogens E. coli O157:H7, Salmonella spp., and L. monocytogenes in aquaponic systems [6,22,38].…”

“…P. aeruginosa is carbapenem-resistant [25]. Pseudomonas fluorescens, found in aquaponics by Chitmanat et al [37], could be a rare cause of invasive hospital-acquired infections, with the usual site of infection being the bloodstream [53]. This bacterium, however, is commonly known for its strong food spoilage ability in ordinary and refrigerated food items (including milk and milk products, meat products, and vegetables) via its enzymes and pigment production [54].…”

“…E. coliRainbow trout(Oncorhynchus mykiss); hybrid catfish (Clarias macrocephalus × C. gariepinus); Nile tilapia (Oreochromis niloticus); Duckweed (Lemna minuta); lettuce (Lactuca sativa)[4,6,19,21,22,37,89,92] …”

The complex microbiome in aquaponics: significance of the bacterial ecosystem

“…in the aquaponics lettuce samples (Elumalai et al 2017;Fox et al 2012;Moriarty et al 2018;Sirsat and Neal 2013). Chitmanat et al (2015) reported the presence of Aeromonas hydrophila, a bacterial fish pathogen and a suspected human pathogen causing diarrhoea (Daskalov 2006), in aquaponics systems containing catfish, but the authors did not investigate pathogen transmission or its effects on the crops. In addition, Schmautz et al (2017) reported a low occurrence of Aeromonas (0.25% of the total bacterial community) in the faecal samples of tilapia reared in an aquaponics system that included lettuce growing on a floating raft.…”