Isolement des souches de Bacillus sp. à partir du tube digestif des poulets de chair

Abstract

Concerns about the misuse of antibiotics and the emergence of multidrug-resistant bacteria have led to a reduction in the use of these antibiotics as growth promoters. Probiotics are one of the alternatives that are of great interest. Bacteria of the genus Bacillus have been the subject of numerous studies because of their extraordinary ability to form endospores highly resistant to hostile environments, to produce different extracellular enzymes, as well as to synthesize antimicrobial compounds. The objective of our study was to isolate and select Bacillus strains from the digestive tract of broilers, based on their ability to produce extracellular enzymes, to inhibit the growth of Escherichia coli, and to resist the hostile conditions of the gastrointestinal tract. Thirty-two isolates were selected for their ability to produce different enzymes (amylase, protease, cellulase, lecithenase, and lipase) using selective media for each enzyme. This study allowed us to select four isolates, with high enzymatic potential, which were subjected to another test to determine their susceptibility to antibiotics. These isolates selected isolates were also studied to evaluate their ability to inhibit the growth of E.coli. Five strains show antimicrobial activity against E.coli. The five isolates were then evaluated for their ability to tolerate digestive tract conditions. Normal growth was recorded at different bile salt concentrations and at pH values up to 3.5. However, at pH 2, only four isolates were shown to have low growth. In the end, the five probbiotic isolates were characterized by morphological and biochemical studies.