Growth and adhesion inhibition of pathogenic bacteria by live and heat-killed food-origin Lactobacillus strains or their supernatants

Influence of dietary supplementation with new Lactobacillus strains on hematology, serum biochemistry, nutritional status, digestibility, enzyme activities, and immunity in dogs

Background and Aim

The use of antibiotics is associated with many side effects, with the development of bacterial resistance being particularly important. It has been found that dogs and their owners host similar resistant bacteria. This contributes to increased concurrent bacterial resistance and a possible trend of increased bacterial resistance in humans. Thus, using probiotics in dogs is an alternative option for preventing and reducing the transmission of bacterial resistance from dogs to humans. Probiotics are characterized by their potential to endure low pH levels and high concentrations of bile acids in the gastrointestinal tract. Lactobacilli are more acid-tolerant and resistant to bile acid, so they are ideal probiotics to be added to the canine diet. According to the previous studies, the benefits of Lactobacillus are a stable nutritional status and greater digestibility, along with improved fecal scores and reduced ammonia in dogs. However, no studies have been conducted with Lactobacillus plantarum CM20-8 (TISTR 2676), Lactobacillus acidophilus Im10 (TISTR 2734), Lactobacillus rhamnosus L12-2 (TISTR 2716), Lactobacillus paracasei KT-5 (TISTR 2688), and Lactobacillus fermentum CM14-8 (TISTR 2720), or their use in combination. Hence, the aim of this study was to examine the possible effects of the aforementioned Lactobacillus on hematological indices, nutritional status, digestibility, enzyme activities, and immunity in dogs. From the results, a new and safe strain of Lactobacillus may emerge for use as a probiotic in the future.

Materials and Methods

In this study, 35 dogs were allocated equally into seven groups: Group 1 received a basal diet (control), while Groups 2-7 received the same diet further supplemented with L. plantarum CM20-8 (TISTR 2676), L. acidophilus Im10 (TISTR 2734), L. rhamnosus L12-2 (TISTR 2716), L. paracasei KT-5 (TISTR 2688), L. fermentum CM14-8 (TISTR 2720), or a mixture of probiotics (L. plantarum, L. acidophilus, L. rhamnosus, L. paracasei, and L. fermentum), respectively. All probiotics were administered at a dose of 10⁹ colony-forming unit/dog for 28 days. Nutritional status, hematology, serum biochemistry, digestibility, enzyme activities, and immunity parameters were assessed.

Results

There were no differences among the groups in body weight, feed intake, body condition score, fecal score, and fecal dry matter on the different sampling days. The hematology and serum biochemical analyses showed a difference only in creatinine activity (p < 0.001), with higher values in group L. fermentum CM14-8 (TISTR 2720) and lower values in group L. paracasei KT-5 (TISTR 2688) than in controls. However, all measurements were within the normal laboratory reference ranges. Fecal characteristics (fecal ammonia and fecal pH), fecal digestive enzyme activities, serum immunoglobulin (IgG), and fecal IgA did not differ significantly among the groups (p > 0.05).

Conclusion

Lactobacillus plantarum CM20-8 (TISTR 2676), L. acidophilus Im10 (TISTR 2734), L. rhamnosus L12-2 (TISTR 2716), L. paracasei KT-5 (TISTR 2688), and L. fermentum CM14-8 (TISTR 2720), along with their mixture are safe and non-pathogenic additives for use as new probiotic strains of Lactobacillus in dogs. Although the new Lactobacillus strains had no effect on hematology, serum biochemistry, nutritional status, digestive enzyme activities, immunity, body weight, feed intake, or body condition scores in dogs, further studies should investigate the intestinal microbiota and the development of clinical treatments.

The Influence of the Degree of Thermal Inactivation of Probiotic Lactic Acid Bacteria and Their Postbiotics on Aggregation and Adhesion Inhibition of Selected Pathogens

The study aimed to evaluate the effect of thermal inactivation of potentially probiotic lactic acid bacteria (LAB) strains isolated from food on their ability to compete with pathogenic microorganisms. Five strains of LAB, previously isolated from food and characterized, one commercial reference strain of Lactiplantibacillus plantarum 299v, and two indicator strains of Staphylococcus aureus 25923 and Listeriamonocytogenes 15313 were used in the study. The experiment consisted in applying a stress factor (high temperature: 80 °C, at a different time: 5, 15, and 30 min) to the tested LAB cells to investigate the in vitro properties such as hydrophobicity abilities (against p-xylene and n-hexadecane), auto-aggregation, co-aggregation with pathogens, and inhibition of pathogens adhesion to the porcine gastric mucin. The bacterial strains showed various hydrophobicity to p-xylene (36-73%) and n-hexadecane (11-25%). The affinity for solvents expanded with increasing thermal inactivation time. All LAB isolates were able to auto-aggregate (ranging from 17 to 49%). Bacterial strains subjected to 5 and 15 min of thermal inactivation had the highest auto-aggregation ability in comparison to viable and heat-killed cells for 30 min. The LAB strains co-aggregated with pathogens to different degrees; among them, the highest scores of co-aggregation were observed for L. monocytogenes, reaching 27% (with 15 min of heat-killed LAB cells). All LAB strains reduced the adherence of pathogenic bacteria in the competition test, moreover, heat-killed cells (especially 15 min inactivated) were more efficient than viable cells. The properties of selected LAB strains as moderately heat-stressed forms analyzed in the study increased the prevention of colonization and elimination of pathogenic bacteria in the in vitro model of gastrointestinal tract. The thermal inactivation process may therefore preserve and modifies some characteristics of bacterial cells.

Characterization of potential probiotic bacteria Enterococcus faecium MC-5 isolated from the gut content of Cyprinus carpio specularis

The goal of this study was to determine the unique characteristics of Enterococcus faecium MC-5, a probiotic bacteria isolated from the intestine of a fish, Cyprinus carpio specularis, collected from Dal Lake in Srinagar, Kashmir, India. For this, the important valuable probiotic attributes, some functional properties, and safety assessments were analyzed in-vitro for the strain MC-5. The strain E. faecium MC-5 exhibited high resistance to low pH, high bile salt, lysozyme, and phenol. The strain MC-5 showed excellent auto- and co-aggregation properties and displayed remarkable hydrophobicity towards various tested hydrocarbons which suggested that the strain possesses venerable adhesion properties. Apart from these, the cell-free supernatant (CFS) of strain MC-5 exhibited phenomenal antimicrobial activity against the tested pathogens. A scanning electron microscope (SEM) image revealed strain MC-5 finely adhered to human colon adenocarcinoma cells (HCT-15 cells). The strain MC-5 showed high bile salt hydrolase activity and excellent cholesterol removal ability of 70.27%. The intact cells of strain MC-5 also showed strong DPPH scavenging activity. The EPS produced by E. faecium MC-5 inhibited the adhesion of Listeria monocytogenes, Staphylococcus aureus, and Salmonella enterica on HCT-15 cells with maximum inhibition rates of 41.82, 40.34, and 55.51%, respectively for displacement assay, which was higher as compared to exclusion (26.06, 26.11, and 39.23%) and competition assays (30.06, 26.7, and 41.20%). Strain MC-5 did not exhibit hemolysis and was also found susceptible to vancomycin and other clinically important antibiotics. When evaluating all the results from the present study, it is propounded that strain MC-5 has enviable probiotic characteristics and thus can be used as bio-protective cultures and/or bio-shield in food and pharmaceutical industries.

The Influence of Environmental Conditions on the Antagonistic Activity of Lactic Acid Bacteria Isolated from Fermented Meat Products

The aim of this study was to determine the impact of environmental conditions on the antimicrobial properties of 21 lactic acid bacteria strains in the selected indicator bacteria. To assess the antimicrobial activity of the whole bacteria culture (WBC), the agar well diffusion method was used. The interference of LAB strains with the growth of the selected indicator bacteria was evaluated by incubating co-cultures in the food matrix. Based on the conducted research, it was found that environmental conditions have a significant impact on the antimicrobial activity of lactic acid bacteria strains. The highest antimicrobial activity was recorded under optimal conditions for the development of LAB, the incubation time being different depending on the indicator strain used. The tested LAB strains were characterized by a high ability to inhibit indicator strains, especially in the food matrix. These results led us to further characterize and purify the antimicrobial compound produced by lactic acid bacteria taking into account changing environmental conditions.