Potential probiotic properties of lactic acid bacteria isolated from gastrointestinal tracts of broiler chickens

Abstract

In poultry farming, antibiotics have been widely utilized as growth enhancers to promote intestinal health and reduce mortality in livestock from pathogenic microorganisms. Many countries have implemented bans on the excessive use of antibiotics because of increasing concerns regarding the resistance of bacteria to antibiotics and the presence of antibiotic residues in poultry products. To counteract this problem, probiotics could be used as adjuncts or as substitutes for preserving a diverse and balanced microflora to prevent the colonization and multiplication of pathogenic bacteria in the gastrointestinal (GI) tract, while also improving poultry performance. The functional properties of lactic acid bacteria (LAB) and their potential as poultry probiotics have been extensively recorded. Hence, this study aimed to assess the potential probiotic properties of LAB for the development of poultry probiotics by isolating lactic acid bacteria from the digestive tracts of broiler chickens. To achieve this aim, a total of 66 LAB isolates were isolated from the crops and small intestines of broiler chickens, which were screened and evaluated for their probiotic properties, among which 11 strains exhibited excellent probiotic traits and were identified by 16S rDNA sequencing as Enterococcus faecalis strain ATCC 19433 (isolates C4 and C5), Pediococcus pentosaceus strain DSM 20336 (isolates C7, C13 C24, SI23 and SI38), Streptococcus salivarius strain ATCC 7073 (isolate SI4) and Levilactobacillus brevis ATCC 14869 (isolates SI6, SI8 and SI9). The selected strains inhibited tested pathogenic bacterial growth Listeria monocytogenes (ATCC 7644), Salmonella enterica (ATCC 13314), Pseudomonas aeruginosa (ATCC 27853) and Staphylococcus aureus (ATCC 29213) with zones of inhibition ranging from 9.00 ±5.66 to 30.00 ±0 mm and survived in simulated gastric juice with a cell viability count greater than 7.0 CFU/ml. Furthermore, the isolates demonstrated remarkable auto aggregation and coaggregation capabilities, along with α-glucosidase inhibitory activity ranging from 25.84 ± 3.08% to 61.77 ± 6.16%. Principal component analysis results indicated that L. brevis NKFS9, P. pentosaceus NKFS3, P. pentosaceus NKFS11 and E. faecalis NKFS1 are the most promising LAB candidates that can be utilized for the development of a multi probiotic strain for broiler chickens. In conclusion, the lactic acid bacteria (LAB) strains isolated from the crops and small intestines of broiler chickens present a valuable prospect for the development of effective probiotics. These probiotics can be utilized as a supplementary inclusion in poultry feed, reducing or obviating the need for antibiotics as growth promoters. Nevertheless, additional in vivo studies are essential to closely monitor and assess the beneficial effects of probiotics on the GI tract of chickens.