The objective of this study was to isolate, identify, and characterize some lactic acid bacterial strains from human milk, infant feces, and fermented grapes and dates, as potential probiotics with antimicrobial activity against some human pathogenic strains. One hundred and forty bacterial strains were isolated and, after initial identification and a preliminary screening for acid and bile tolerance, nine of the best isolates were selected and further identified using 16 S rRNA gene sequences. The nine selected isolates were then characterizedin vitrofor their probiotic characteristics and their antimicrobial activities against some human pathogens. Results showed that all nine isolates belonged to the genusLactobacillus. They were able to tolerate pH 3 for 3 h, 0.3% bile salts for 4 h, and 1.9 mg/mL pancreatic enzymes for 3 h. They exhibited good ability to attach to intestinal epithelial cells and were not resistant to the tested antibiotics. They also showed good antimicrobial activities against the tested pathogenic strains of humans, and most of them exhibited stronger antimicrobial activity than the reference strainL. caseiShirota. Thus, the nineLactobacillusstrains could be considered as potential antimicrobial probiotic strains against human pathogens and should be further studied for their human health benefits.

Probiotics have become highly recognized as supplements for humans and animals because of their beneficial effects on health and well-being. The present review aims to provide an overview of different steps through which microbial strains become applicable probiotics in food and/or feed industries. Isolation of potential probiotic strains is the first step. Lactic acid bacteria are the most frequently used microorganisms as probiotics, which can be isolated from human, animal, plant, and environment. The next steps are identification of the isolates and characterization of them based on the main selection criteria for any potential probiotic microorganism, including resistance to gastric acidity and bile salt, adherence to mucus and/or intestinal epithelial cells and cell lines, and antimicrobial and antagonism activity against potentially pathogenic microbes. There are additional probiotic properties that may be considered for selection of probiotic strains with specific effects, such as cholesterol reduction ability, antioxidant activity, or cytotoxic effect against cancer cells. However, a potential probiotic does not need to fulfill all such selection criteria. As the last step, safety status of probiotics for humans is verified by taxonomy clarification, in vitro and in vivo tests, human trials, and genome sequencing.

Selenium (Se) and vitamin E (Vit E) can act synergistically and affect biological processes, mainly antioxidant and immunity. The use of excess dietary Vit E and Se in animals’ feed could enhance immune response and induce disease resistance. Moreover, different Se sources may provide different alterations in the immune system. Accordingly, the aim of the current study was to assess the impact of dietary supplementation of Vit E, inorganic Se (sodium selenite, SS), bacterial organic Se of ADS18, and their different combinations on the plasma immunoglobulins, ceacum microbial population, and splenic cytokines gene expression in broiler chickens. Present results showed that, Se and Vit E synergistic effect was clear in plasma IgM level at day 42 and in splenic cytokines expression (TNF-α, IFN-γ, IL-2, IL-10). The combination of 0.3 mg/kg ADS18-Se with 100 mg/kg Vit E showed the highest IgM level compared to Vit E- SS complex. The combination of either SS or ADS18-Se with Vit E had no significant effect on IFN- γ and IL-10 compared to Vit E alone, while Vit E alone showed the significantly lowest TNF-α compared to the Se combinations. Supplementation of 100 mg/kg Vit E had no effect on microbial population except a slight reduction in Salmonella spp. The main effect of Se sources was that both sources increased the day 42 IgA and IgG level compared to NS group. ADS18-Se modulate the caecum microbial population via enhancing beneficial bacteria and suppressing the E-coli and Salmonella spp. while both Se and Vit E factors had no effect on lymphoid organ weights. The inclusion of 100 mg/kg Vit E with 0.3 mg/kg ADS18-Se, effectively could support the immune system through regulation of some cytokines expression and immunoglobulin levels more than using ADS18-Se alone, while no difference was observed between using SS alone or combined with Vit E.

The applications of conventional culture-dependent assays to quantify bacteria populations are limited by their dependence on the inconsistent success of the different culture-steps involved. In addition, some bacteria can be pathogenic or a source of endotoxins and pose a health risk to the researchers. Bacterial quantification based on the real-time PCR method can overcome the above-mentioned problems. However, the quantification of bacteria using this approach is commonly expressed as absolute quantities even though the composition of samples (like those of digesta) can vary widely; thus, the final results may be affected if the samples are not properly homogenized, especially when multiple samples are to be pooled together before DNA extraction. The objective of this study was to determine the correlation coefficients between four different methods of expressing the output data of real-time PCR-based bacterial quantification. The four methods were: (i) the common absolute method expressed as the cell number of specific bacteria per gram of digesta; (ii) the Livak and Schmittgen, ΔΔCt method; (iii) the Pfaffl equation; and (iv) a simple relative method based on the ratio of cell number of specific bacteria to the total bacterial cells. Because of the effect on total bacteria population in the results obtained using ΔCt-based methods (ΔΔCt and Pfaffl), these methods lack the acceptable consistency to be used as valid and reliable methods in real-time PCR-based bacterial quantification studies. On the other hand, because of the variable compositions of digesta samples, a simple ratio of cell number of specific bacteria to the corresponding total bacterial cells of the same sample can be a more accurate method to quantify the population.