Human milk has an ability to protect against GI infections and supplies balanced and adequate nutrient contents to the infant for better functioning [26], [29]. Streptococcus and Staphylococcus are among the most common microflora found in the breast milk [24]. As probiotic, Streptococci strains must possess certain characteristics to exert their maximum probiotic effect. The properties include bacterial adhesion capacity, exclusion of intestinal pathogens and immunoregulatory effects [54]. The presence of probiotics could help restore the balance of the gut microbiota and thus improve the overall health and wellbeing [52]. Studies reported that for oral health S. thermophilus is the most relevant probiotic since its urease activity (hydrolysis of urea which usually increase the pH of oral environment to basic) is aciduric, which increases in acidic environments. This might allow S. thermophilus to replace other dental decay causing species (like mutans Streptococci (MS) and Lactobacilli) that performs well in basic environment, from oral biofilms, thus subsiding their cariogenicity (cause tooth decay) [14], [3]. Another Streptococcal species that is utilized as a commercial oral probiotic of certain significance is S. salivarius M18 strains. A study done by Burton et al. in 2013 demonstrated that plaque development could be decreased with a twice a day dose of Streptococcus salivarius M18 in children going to school. The outcomes of the study by [16] showed that the use of S. salivarius M18 increase the chance of preventing the growth of tooth decay causing microbes [52]. Numerous species including Streptococcus salivarius, are often found in the newborn’s oral cavity [10], [18]. The metabolic products from Streptococcus species, resulting from the nutritional oligosaccharides in breast milk potentially pave the way for the establishment the oral micro flora, therefore promoting growth and attachment of probiotic bacteria inside the oral cavity [1], [68], [46], [21]. Though, the longitudinal influence of Streptococcal initial colonizers on the oral environment and the effect of breastfeeding practices on babie’s oral and general health are broadly unidentified and be worthy of investigation [18].

The intestinal mucosa plays an active role in the reaction to systemic diseases and infection that follows in disease conditions such as inflammatory bowel disease (IBD), sepsis, lung injury, trauma, infectious diarrhea and burn and has been pointed as a “trigger” of inflammation in severe illness [22], [11], [17], [60], [40], [44]. Bacterial infection usually occurs by attachment of the pathogen to the intestinal epithelial cells (IEC) and usually cured by antibiotic treatment. Those antibiotic treatments have certain negative effects. Use of antibiotics as food additives or growth promoters is banned by European Union (EU), and the prevention of antibiotics was because of development of microbial resistance to those antibiotics that are used for treatment of poultry and animal diseases. Additionally, antibiotics possess some other glitches like killing of some advantageous bacteria in the GIT [58]. Furthermore, it has been observed that usage of antibiotics decreased rate of growth which may be because of growing occurrence of dysbacteriosis and subclinical necrotic enteritis [49]. Therefore, probiotics impart a vital role as the finest substitute to antibiotics due to valuable aspects and utilization as growth enhancers in humans and animals [74], [2]. Probiotic supplements are the emerging technology for the treatment of enteropathogenic infections [72]by creating a competitive environment against pathogens inside the gastrointestinal track and by hindering intestinal epithelial cells (IECs) attachment to pathogens [37], [19].

Many immune mediators are secreted by IECs in response to potentially pathogenic organisms, comprising antibacterial peptides like mucins [13], defensins [64], chemokines and cytokines such us interleukin IL‐8 [61]. IL‐8 (C‐X‐C chemokine) is transcriptionally regulated by nuclear factor NF‐κB [31]demonstrating neutrophil’s potent chemotactic activity. IL‐8 is secreted by IECs as result of pro‐inflammatory cytokines like tumor necrosis factor α (TNF‐α) and numerous pathogenic bacteria. However, some controversial findings have been reported [51], it was shown that some commensal non-pathogenic bacteria like Escherichia coli Nissle 1917 upsurge IL-8 production but Lactobacillus rhamnosus GG, Lactobacillus reuteri or VSL#3 (probiotic cocktail) reduced the secretion of IL‐8 by IECs [39], [48], [42]; O’Hara & Shanahan, 2006). TNF-α and pathogens mediate NF-κB activation by intestinal epithelial cells (IECs) causing the secretion of chemokine IL-8 [54], [38]. IL-8 could result in inflammatory cell movement into the mucosal lining of IECs, subsequently inflammatory bowel diseases [47]. Current studies propose that S. lactarius MB622 and S. salivarius MB620 provoke an anti-inflammatory response.

The aim of the present study is to examine S. lactarius MB622 and S. salivarius MB620 for their potential probiotic properties, such as acid and bile tolerance, adhesion capacity, antibacterial activity, hydrophobicity and their ability to inhibit the attachment of few intestinal pathogens. We also investigated their ability to modulate Caco-2 cells IL-8 secretion in presence of TNF-α by investigating their immunomodulatory properties. Therefore, it is need of the hour to explore the use of these potential probiotic strains in functional fermented foods, infant formula or use as an alternative to harsh non-steroidal anti-inflammatory drugs (NSAIDs).