In Vitro Selection and Identification of Potential Probiotics Isolated from the Gastrointestinal Tract of Nile Tilapia, Oreochromis niloticus

Abstract

Fish gut bacteria can be used as probiotics for aquaculture. The aim of this study is to screen and identify beneficial probiotic bacteria from the gut of Nile tilapia, Oreochromis niloticus. Nine out of one hundred thirty-five isolates were non-pathogenic through intraperitoneal injection and had antibacterial activities with at least a strain from the five isolated fish pathogens, Aeromonas sobria, Aeromonas hydrophila, Pseudomonas aeruginosa, Pseudomonas putida, and Staphylococcus aureus. Further tests showed that such isolates can survive in the presence of high bile concentration (10%) and at different acidic pH values. A strains (14HT) was sensitive to all selected antibiotics, two strains were (9HT and 11HT) resistant to streptomycin and three strains (9HT, 11HT and 38HT) had resistance to two antibiotics. Four isolates (11HT, 33HT, 38HT and 41HT) had an amylase and a protease activities and one strain (47HT) showed only amylase activity. Based on 16S rRNA gene analysis, the isolated strains were identified as follows: Lactococcus lactis (8HT, 9HT, 11HT and 33HT); Enterococcus faecalis (14HT), Lysinibacillus sp. (38HT) and Citrobacter freundii (39HT, 41HT and 47HT).

Antimicrobial activity oftrans-cinnamic acid and commonly used antibiotics against important fish pathogens and nonpathogenic isolates

“…Furthermore, it was also reported that Lysinibacillus species could be used as probiotics in fish (Reda et al . ). However, there is no detailed information available about L. xylanilyticus species in the literature.…”

“…It was suggested that bacteriocin purified from Lysinibacillus JX416856 isolate could present an alternative therapeutic agent in the control of food pathogens (Ahmad et al 2014). Furthermore, it was also reported that Lysinibacillus species could be used as probiotics in fish (Reda et al 2017). However, there is no detailed information available about L. xylanilyticus species in the literature.…”

Establishment and characterization of a competitive exclusion bacterial culture derived from Nile tilapia (Oreochromis niloticus) gut microbiomes showing antibacterial activity against pathogenic Streptococcus agalactiae

“…agalactiae . It was maintained in TSB medium reported in the successful development of a competitive exclusion culture from different animals including fish culture [36,37]. This medium is relatively inexpensive, easily obtainable and easily reproducible from off-the-shelf-ingredients, also appropriate to support the growth of aerobic and anaerobic bacteria.…”

Quorum Quenching Properties and Probiotic Potentials of Intestinal Associated Bacteria in Asian Sea Bass Lates calcarifer

“…An opaque halo around the cultured bacteria due to crystals of the calcium salt of the fatty acids liberated by lipolysis was regarded as a positive lipase activity. The presence of amylolytic activity was determined by starch medium consisting of 12 g starch, 4 g peptone, and 12 g agar per liter [82]. The plates were then covered with a 1% Lugol's iodine solution for the detection of a clear halo in a dark field, representing a positive activity.…”