Inhibitory effect of different chicken-derived lactic acid bacteria isolates on drug resistant Salmonella SE47 isolated from eggs

Bioprotective potential of lactic acid bacteria for Salmonella biocontrol in vitro

Lactic acid bacteria (LAB) are an important option for Salmonella control in animal production, resulting in lower antibiotic use. The objective of this research was to isolate LAB from meat products and from commercial probiotics sold as nutritional supplements for in vitro verification of their bioprotective potential. Eleven bacteria were identified as Pediococcus acidilactici, two as Lacticaseibacillus rhamnosus, one as Lacticaseibacillus paracasei paracasei, one as Limosilactobacillus fermentum, and one as a consortium of Lactobacillus delbrueckii bulgaricus and L. fermentum. All bacteria showed inhibitory activity against Salmonella, with emphasis on the inhibition of P. acidilactici PUCPR 011 against Salmonella Enteritidis 33SUSUP, S. Enteritidis 9SUSP, S. Enteritidis 56301, S. Enteritidis CRIFS 1016, Salmonella Typhimurium ATCC™ 14,028®, and Salmonella Gallinarum AL 1138, with inhibition halos of 7.3 ± 0.5 mm, 7.7 ± 1.0 mm, 9.0 ± 1.8 mm, 7.3 ± 0.5 mm, 7.7 ± 1.0 mm, and 7.3 ± 0.5, respectively. The isolates P. acidilactici PUCPR 011, P. acidilactici PUCPR 012, P. acidilactici PUCPR 014, L. fermentum PUCPR 005, L. paracasei paracasei PUCPR 013, and L. rhamnosus PUCPR 010 showed inhibition greater than 2 mm against at least 3 Salmonella and were used for encapsulation and in vitro digestion. The encapsulation efficiency ranged from 76.89 ± 1.54 to 116.48 ± 2.23%, and the population after 12 months of storage was from 5.31 ± 0.17 to 9.46 ± 0.09 log CFU/g. When simulating swine and chicken digestion, there was a large reduction in bacterial viability, stabilizing at concentrations close to 2.5 log CFU/mL after the analyses. The analyzed bacteria showed strong in vitro bioprotective potential; further analyses are required to determine in vivo effectiveness.

Probiotic Properties of Chicken-Derived Highly Adherent Lactic Acid Bacteria and Inhibition of Enteropathogenic Bacteria in Caco-2 Cells

Lactic acid bacteria (LAB) as probiotic candidates have various beneficial functions, such as regulating gut microbiota, inhibiting intestinal pathogens, and improving gut immunity. The colonization of the intestine is a prerequisite for probiotic function. Therefore, it is necessary to screen the highly adherent LAB. In this study, the cell surface properties, such as hydrophobicity, auto-aggregation, co-aggregation, and adhesion abilities of the six chicken-derived LAB to Caco-2 cells were investigated. All six strains showed different hydrophobicity (21.18-95.27%), auto-aggregation (13.61-30.17%), co-aggregation with Escherichia coli ATCC 25922 (10.23-36.23%), and Salmonella enterica subsp. enterica serovar Typhimurium ATCC 13311 (11.71-39.35%), and adhesion to Caco-2 cells (8.57-26.37%). Pediococcus pentosaceus 2-5 and Lactobacillus reuteri L-3 were identified as the strains with strong adhesion abilities (26.37% and 21.57%, respectively). Moreover, these strains could survive in a gastric acid environment at pH 2, 3, and 4 for 3 h and in a bile salt environment at 0.1%, 0.2%, and 0.3% (w/v) concentration for 6 h. Furthermore, the cell-free supernatant of P. pentosaceus 2-5 and L. reuteri L-3 inhibited the growth of enteropathogenic bacteria and the strains inhibited the adhesion of these pathogens to Caco-2 cells. In this study, these results suggested that P. pentosaceus 2-5 and L. reuteri L-3, isolated from chicken intestines might be good probiotic candidates to be used as feed additives or delivery vehicles of biologically active substances.

Characterization of Lactic Acid-Producing Bacteria Isolated from Rumen: Growth, Acid and Bile Salt Tolerance, and Antimicrobial Function

Lactic acid bacteria are some of the dominant bacteria in the rumen, and they have a high ability for lactic acid production. The present study aimed to screen and evaluate the performance of culturable rumen bacteria from Chinese Holstein dairy cows as a potential probiotic or inoculant for silage production, in order to isolate ruminal lactic acid bacteria and evaluate their potential as probiotics. Three strains of Enterococcus avium (E. avium, EA1-3); three strains of Streptococcus lutetiensis (S. lutetiensis, SL1-3); and six strains of Streptococcus equinus (S. equinus, SE1-6) were successfully identified from the rumen fluid using modified De Man Rogosa sharp medium supplemented with 0.325% lactic acid. E. avium, S. lutetiensis and S. equinus are clustered in the phylogenetic tree. All the 12 Gram-positive strains reached the plateau growth phase in 6–10 h, with an OD600 at about 1.8. Both gas and acid accumulation reached plateaus at about 10–12 h in all strains, and S. equinus showed the strongest capacity. The highest lactic acid accumulation was detected in S. equinus broth (up to 219.77 μmol/L). The growth of all isolates was inhibited at pH 4.0, and EA2, SL1, SL2, SL3 and SE2 were tolerant to 0.1%, 0.2% and 0.3% bile salt. In addition, the supernatants of the strains had inhibitory effects on Escherichia coli and Staphylococcus aureus. Specifically, the S. equinus strains exhibited the strongest inhibition of the pathogens. In conclusion, these 12 strains had good potential as silage inoculants or probiotics for edible animals, especially S. equinus.

Anti-inflammatory Effect of Probiotic Limosilactobacillus reuteri KUB-AC5 Against Salmonella Infection in a Mouse Colitis Model

Acute non-typhoidal salmonellosis (NTS) caused by Salmonella enterica Typhimurium (STM) is among the most prevalent of foodborne diseases. A global rising of antibiotic resistance strains of STM raises an urgent need for alternative methods to control this important pathogen. Major human food animals which harbor STM in their gut are cattle, swine, and poultry. Previous studies showed that the probiotic Limosilactobacillus (Lactobacillus) reuteri KUB-AC5 (AC5) exhibited anti-Salmonella activities in chicken by modulating gut microbiota and the immune response. However, the immunobiotic effect of AC5 in a mammalian host is still not known. Here, we investigated the anti-Salmonella and anti-inflammatory effects of AC5 on STM infection using a mouse colitis model. Three groups of C57BL/6 mice (prophylactic, therapeutic, and combined) were fed with 10⁹ colony-forming units (cfu) AC5 daily for 7, 4, and 11 days, respectively. Then, the mice were challenged with STM compared to the untreated group. By using a specific primer pair, we found that AC5 can transiently colonize mouse gut (colon, cecum, and ileum). Interestingly, AC5 reduced STM gut proliferation and invasion together with attenuated gut inflammation and systemic dissemination in mice. The decreased STM numbers in mouse gut lumen, gut tissues, and spleen possibly came from longer AC5 feeding duration and/or the combinatorial (direct and indirect inhibitory) effect of AC5 on STM. However, AC5 attenuated inflammation (both in the gut and in the spleen) with no difference between these three approaches. This study demonstrated that AC5 confers both direct and indirect inhibitory effects on STM in the inflamed gut.