Probiotics have been used for over a century to prevent and treat diseases. They can reduce the effects of gastroenteritis and are now used to treat acute diarrhea. This study aimed to evaluate the co-aggregative effects of probiotics bacteria against diarrheal causative bacteria. For this purpose, 11 isolates of probiotic bacteria were used in the current study, including three Lactobacillus plantarum, one Lactobacillus gasseri, two Lactobacillus fermentum, three Lactobacillus acidophilus, and two Lactococcus garvieae isolates. All isolates were tested for antibiotic susceptibility, autoaggregation ability, adhesion ability, antibacterial activity, acid tolerance, and bile salts tolerance. The results showed that most of them had the ability to autoaggregate after 4 h, with the highest percentage of 57.14% for L. fermentum. For the antibiotic susceptibility test, all the isolates showed resistance against trimethoprim/sulfamethoxazole, except one isolate. Moreover, all the isolates, except one, were susceptible to both vancomycin and tetracycline. All tested isolates had adhesion ability with different survival rates, which reached 34.57% for L. plantarum in acidic conditions. Besides, the highest survival rate was 85.17%, which belonged to L. garvieae, for bile salt tolerance. Probiotic isolates had an antibacterial effect against diarrhea-causative bacteria with an inhibition diameter of 17-49 mm for different Lactobacillus spp. and Lactococcus spp. isolates. Furthermore, the co-aggregation ability of probiotic isolates against diarrhea-causative bacteria was studied, and results showed that probiotic isolates had a co-aggregative effect against diarrhea-causative bacteria, Escherichia coli, Shigella sonnei, and Providencia alcalifaciens, after 24 h of incubation. The highest co-aggregative effect of probiotics isolates belonged to L. fermentum and L. acidophilus against P. alcalifaciens with a co-aggregation percentage of 100%, while the lowest co-aggregation rate was 14.29% against E. coli.  The findings revealed the probiotic properties and co-aggregative effects of probiotic bacteria against diarrhea-causative bacteria.

Mucosal surfaces of the body provide a universal entry portal for all known and emerging infectious pathogenic microbes. Therefore, it seems that special vaccination strategies are needed for vaccines that can hinder the entry capability of pathogenic microbes through the mucosal surfaces. Lactic acid bacteria are widely used in the food industry and are presently applied as delivery vehicles in many biological investigations. Among these bacteria, Lactococcus lactis is considered as a promising candidate for mucosal live vaccines to be used as an antigen delivery vector. This is an attractive alternative and a safer vaccination strategy against the pathogens, compared to other conventional methods. In this review, we summarized the applications of L. lactis as a mucosal vector of vaccine delivery for heterologous expression of proteins and its applications in biotechnology.

Needle free vaccines have a several advantages and very attractive way for vaccination. In a body, mucosal surfaces provide a universal entry portal for all the known and emerging infectious pathogenic microbes. Therefore, it seems, vaccination strategies need to be reorganized for vaccines that are hindering the entry capability of pathogenic microbes through mucosal surfaces. Lactic acid Bacteria (LAB) are widely used in the food industry and at the present, used as delivery vehicles for biological investigations. In this review, we summarized the Results of several studies which Lactococcus lactis (L. lactis) used as a live vector for vaccines. These bacteria are considered as promising candidates for heterologous expression of proteins and biotechnological usage. LAB are considered as promising candidates for heterologous expression of proteins and biotechnological usage. The results showed that these bacteria have an ability to deliver antigen to immune system. Therefore, developing mucosal live vaccines using lactic acid bacterium, L. lactis, as an antigen delivery vector, is an attractive alternative choice and a safer vaccination strategy against pathogens.