In vitro bacterial probiotic selection from Nannostomus beckfordi, an Amazon ornamental fish

Abstract

This study aimed to isolate and select in vitro bacteria with probiotic potential for the Amazon ornamental fish Nannostomus beckfordi. For isolate, twelve fish underwent surgery procedure to remove their intestinal tract, macerate and then inoculate in the plate petri containing de Man Rugosa Sharped Agar (MRS). After bacterial growth (48 hours at 35ºC), selected strains were inoculated in MRS broth and submitted to resistance test with NaCl (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0%), pH (4, 5, 6, 8 and 9) and bile salts (5% w/v). Inhibition test against pathogenic bacteria Aeromonas hydrophila, Pseudomonas aeroginosa, Streptococcus agalactiae and Aeromonas Jandaei was also performed. Within the isolated strains group (23 strains), only six (S1, S2, S3, S4, S5 and S6) showed probiotic potential. Strains S1 and S6 showed the greater resistance for NaCl (0.5% and 1%) and pH (5 and 6), but only S1 obtained better results to resist the bile salts. Even against pathogenic bacteria, the S1 showed the best results with inhibition halos greater than 9 mm. In the end, this bacterial strain (S1) was identified as Enterococcus faecium 11037CHB. Thus, this is the first report regarding isolated autochthonous bacterium E. faecium with probiotic potential of N. beckfordi.

Selection and isolation of bacterium with probiotic potential from the Amazon ornamental fish Hypancistrus sp. (Siluriformes, Loricariidae)

“…In the present study, strains with probiotic potential grew at all concentrations of NaCl (0.5 to 3%), with emphasis on St5 (E. faecium). The same occurred in growth resistance of the E. genus as a probiotic, which was observed for the species Pterophyllum scalare and Nannostomus beckfordi (Dias et al, 2019;Lopes et al, 2022).…”

“…The importance of in-vitro tests is related to the select possibility strains with resistance to growth in the face of chemical barriers, allowing greater chances of colonizing the animal's intestine (Paixão et al, 2020a;Yamashita et al, 2020). For the selection of these strains with probiotic potential, the used culture medium provides guidance on the target group of bacteria to be educated and which are subsequently evaluated in in-vitro assays, such as the MRS medium, which is used for the selection of lactic acid bacteria (Dias et al, 2019;Lopes et al, 2022;Paixão et al, 2020a). In the present study, the bacterium E. faecium (St5) showed growth in the presence of NaCl, pH and bile salts, a promising characteristic for resistance to the physiological actions of the organism, allowing colonization of the intestinal tract and beneficial effects for the host.…”

“…In this study, the St5 strain (E. faecium) inhibited the growth of all tested pathogens, with the highest inhibition halo for A. hydrophila (16.89 ± 0.32 mm). The antagonistic activity of this bacterium is related to the release of enterocins (P and TJUQ1), lactic acids and hydrogen peroxide (Braiek et al, 2017;Yoswaty et al, 2020), which act by inhibiting A. hydrophila, E. durans, P. aeruginosa and S. agalactiae (Dias et al, 2019;Lopes et al, 2022).…”

“…For the in-vitro resistance tests, the experiments were carried out in a completely randomized design with different concentrations of pH (4, 5, 6, 8 and 9), NaCl (0; 0.5; 1; 1.5; 2; 2.5 and 3%), and the presence of bile salts (5% w/v), all assays with four replications. After bacterial growth (24 hours at 35°C), the percentage reduction in absorbance (630 nm) was analyzed by spectrophotometry (Paixão et al, 2020a;Lopes et al, 2022).…”

“…The strain with the best results in the tests was identified by the MALDI-TOF (mass spectrometry) technique. The procedure for removal, identification, cultivation, growth kinetics and in-vitro testing of the strains were established according to the procedure adapted from Lopes et al (2022) and Paixão et al (2020a).…”