Antagonistic impact of Lactobacilli on Escherichia coli in the gut of Labeo rohita fingerlings fed with bakery wastes

Abstract

The present study was designed to check the feed conversion ratio (FCR) and, changes in gut microbiota of Labeo rohita fingerlings fed with different bakery product diets. The beneficial growth promoting lactobacilli and pathogenic Escherichia coli bacteria were isolated from the gut of Labeo rohita fingerlings and evaluated the antagonistic impact of lactobacilli on E. coli. The study was conducted for three months using five circular tanks of 5 feet diameter in two replicates. The experimental tanks were named as D1, D2, D3, D4 and D5 based on different types of diets. Fingerlings of the D1 tank were fed with control feed of Oryza Organics containing 20% crude protein. The D2 tank was fed with an experimental diet containing 25% cream cake as a basic ingredient. The D3 tank was fed with an experimental diet with 35% cream cake as a basic ingredient, while the D4 tank fingerlings were fed with a diet with 25% biscuits as a basic ingredient, and D5 tank fingerlings with a diet with 35% biscuits as a basic ingredient. The feed was provided according to the body weight of the fish twice a day. By using the staining method and biochemical test, lactobacilli and E. coli were identified from the gut of the fingerlings. To confirm the diagnosis of identified bacteria, 16S rDNA gene sequencing was used. Highest growth was observed (FCR, 1.200 ± 0.028) in D4 followed by that in D1 (1.360 ± 0.014), D2 (1.450 ± 0.014), D5 (1.512 ± 0.002), and D3 (1.595 ± 0.007), respectively. The antagonistic activity of lactobacilli against E. coli was also recorded. In diet D4, the lactobacilli concentration was highly significant, i.e., 9.7 x 10⁷ ± 2.4 x 10⁷ cfu/g and that of E. coli was found as 1.1 x 10⁷ ± 1.4 x 10⁶ cfu/g followed by D5 having 6.6 x 10⁷  ± 1.6 x 10⁷ cfu/g lactobacilli and 1.9 x 10⁷ ± 2.5 x 10⁶ cfu/g  E. coli, D2 with 2.4 x 10⁷  ± 1.9  x 10⁶ cfu/g lactobacilli and E. coli 1.6 x 10⁷ ± 2.1 x 10⁶ cfu/g, D1 with 2.4 x 10⁷ ± 1.9 x 10⁶ cfu/g lactobacilli and E. coli 1.8 x 10⁷ ± 1.8 x 10⁶ cfu/g, and D3 with 9.1 x 10⁶  ± 1.8 x 10⁶ cfu/g lactobacilli and E. coli 1.4 x 10⁷ ± 1.4 x 10⁶ cfu/g.