In-vitro assessment of probiotic potential of bacteria isolated from chicken gastrointestinal tract.

Abstract

Broilers farming has been suffering from multiple challenges, including extensive application of antibiotics. Probiotics-supplemented feed might serve as an efficient alternative to these growth stimulants. We designed the present study to isolate bacteria from chickens' gut and analyze their probiotic characteristics. For isolation, the serial dilution method and De Man-Rogosa-Sharpe agar (MRS) medium were used. Isolates were characterized via biochemical and ribotyping analysis, growth study, antimicrobial and antibiotic sensitivity profiling, acid and bile salt tolerance, intestinal adhesion and cholesterol degradation assays. Four isolates were identified as Enterococcus durans strain PUPro5, Lactobacillus acidophilus strain PUPro6, Enterococcus durans strain PUPro7 and Ligilactobacillus salivarius strain PUPro8. The highest growth rate was observed in E. durans strain PUPro7 with OD₆₀₀ = 1.929 ± 0.001 and start of log phase after 3 h. All isolates showed maximum intestinal cell adhesion at 90 min, ranging between 423 and 588.67 CFUs/ml. All isolates demonstrated maximum tolerance potential at 2% concentration of NaCl with L. salivarius strain PUPro8 being the most efficient among all isolates. The highest resistance to bile salts was observed in L. acidophilus strain PUPro6 with an optimum OD₆₀₀ of 1.748 at log phase. All bacteria demonstrated antimicrobial resistance against Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis and B. proteus. Maximum tolerance was observed in L. acidophilus strain PUPro6 (OD₆₀₀ = 1.344 ± 0.017) against P. aeruginosa, L. salivarius strain PUPro8 (OD₆₀₀ = 1.304 ± 0.003) against B. subtilis, E. durans strain PUPro5 (OD₆₀₀ = 1.294 ± 0.066) against S. aureus and E. durans strain PUPro7 (OD₆₀₀ = 1.216 ± 0.002) against B. proteus. All isolates were sensitive against all the antibiotics, with maximum zone of inhibition against velosef and cefadroxil in the E. durans strain PUPro5. Cholesterol degradation efficiency of isolates ranged between 195.2 and 204.6 mg/dl. Bacteria characterized in the present study exhibit probiotic potential and can be recommended for testing their effect on chickens' growth and meat quality through broiler diet supplementation.