Quantitative analyses of the bacterial microbiota of rearing environment, tilapia and common carp cultured in earthen ponds and inhibitory activity of its lactic acid bacteria on fish spoilage and pathogenic bacteria

Abstract

The present study aimed to evaluate the bacterial load of water, Nile Tilapia and common Carp intestines from earthen ponds, isolate lactic acid bacteria (LAB) and assess their antimicrobial activity against fish spoilage and pathogenic bacteria. Following enumeration and isolation of microorganisms the antimicrobial activity of the LAB isolates was evaluated. Taxonomic identification of selected antagonistic LAB strains was assessed, followed by partial characterisation of their antimicrobial metabolites. Results showed that high counts (>4 log c.f.u ml or 8 log c.f.u g) of total aerobic bacteria were recorded in pond waters and fish intestines. The microbiota were also found to be dominated by Salmonella spp., Vibrio spp., Staphylococcus spp. and Escherichia coli. LAB isolates (5.60%) exhibited potent direct and extracellular antimicrobial activity against the host-derived and non host-derived spoilage and pathogenic bacteria. These antagonistic isolates were identified and Lactococcus lactis subsp. lactis was found as the predominant (42.85%) specie. The strains displayed the ability to produce lactic, acetic, butyric, propionic and valeric acids. Bacteriocin-like inhibitory substances with activity against Gram-positive and Gram-negative (Vibrio spp. and Pseudomonas aeruginosa) bacteria were produced by three L. lactis subsp. lactis strains. In this study, the LAB from the microbiota of fish and pond water showed potent antimicrobial activity against fish spoilage or pathogenic bacteria from the same host or ecological niche. The studied Cameroonian aquatic niche is an ideal source of antagonistic LAB that could be appropriate as new fish biopreservatives or disease control agents in aquaculture under tropical conditions in particular or worldwide in general.

Changes in sensory, physicochemical, and microbiological properties of fresh captured tropical pink shrimps (Penaeus duorarum notialis) inoculated with Lactobacillusplantarum Lp6SH, Lactobacillus rhamnosus Yoba, and their cell‐free culture supernatants during storage at 4°C

“…From fishermen, wet whole shrimps are sold to wholesale fishmongers and subsequently marketed chilled in the other parts of the country and in Nigeria. Thus, the shrimps could become unfit for consumption following bacterial contamination due to hot climatic conditions (temperature over 30 C), lack of modern preservation infrastructures (for refrigeration and freezing), poor hygienic handling conditions as well as the long periods of time elapsed during transportation (Kaktcham et al, 2017). In addition, blackspots (melanosis) appear on tropical shrimps despite instant freezing.…”

Bile salt hydrolase and antimicrobial activities of three bile resistant probiotics Lactobacillus plantarum strains isolated from Cameroonian artisanal fermented milk

“…Then probiotics should inhibit the growth of pathogenic microorganisms. This inhibition by Lactobacillus probiotics is made possible by the production of metabolites such as hydrogen peroxide (33), organic acids (acetic, formic, caproic, propionic, butyric, valeric, phenyllactic and 4-hydroxyl-phenyl-lactic acids) (7), carbon dioxide, reuterin or even bacteriocins (34,8 …”

“…Antimicrobial activity was determined using the agar-spot test as described by Kaktcham et al (8). Succinctly, 2μl of each 6 h old culture was spotted onto MRS agar and incubated at 37°C for 24h.…”

“…The BSH enzyme catalyzes the hydrolysis of conjugated bile salts into amino acid residue and bile acid. Concerning the antimicrobial activities, the mechanism through which probiotics may antagonize pathogens involves the production of antimicrobial compounds such as lactic acid, acetic acid, hydrogen peroxide and bacteriocins (7,8).…”

Microbial Communities of Culture Water and African Catfish Reared in Different Aquaculture Systems in Nigeria Analyzed Using Culture Dependent Techniques

“…The culture systems water and environments harbor different microbial communities which affects the microbiota of the fish and gastro intestinal tract (GIT). Fish are associated with the microorganisms in their environment [6,7,8]. The health status of cultured fish and its safety for human consumption is culture system dependent.…”