Thesis (M.Sc.) - Cairo University - Faculty of Agriculture - Department of Microbiology

This study is the first one to isolate Enterococcus mediterraneensis in Egypt and to characterize it as new species of probiotics globally. Fourteen LAB isolates, from different dairy and meat products, were identified as Enterococcus mediterraneensis, Lactobacillus fermentum and Streptococcus lutetiensis by 16S rRNA gene sequencing, and in vitro characterized for their actual probiotic potential. All Ent. mediterraneensis isolates were resistant to clindamycin, whereas Lb. fermentum isolates were resistant to ampicillin, clindamycin and vancomycin. The Ent. mediterraneensis and Lb. fermentum isolates displayed high overall digestive survival ranged from 1.35±0.06 to 32.73±0.84% and from 2.01±0.01 to 23.9±1.85%, respectively. All isolates displayed cell surface hydrophobicity ranged between 15.44±6.72 and 39.79±2.87%. The strongest auto-aggregation capability, higher than 40% after 24h, was observed for most Ent. mediterraneensis and Lb. fermentum isolates. The Ent. mediterraneensis isolates (L12 and L15), Lb. fermentum (L8, L9 and L10) and S. lutetiensis (L14) exhibited the greatest co-aggregation with Sal. typhimurium, E. coli O157:H7, Lis. monocytogenes, Staph. aureus and B. cereus. The results of antimicrobial assay confirmed that, 57.14% of Ent. mediterraneensis isolates could be considered bacteriocinogenic against E. coli O157: H7, B. cereus and Staph. aureus. For Lb. fermentum, 60% were bacteriocinogenic isolates against Sal. typhimurium and Staph. aureus. For Lis. monocytogenes, 42.86 and 40% of Ent. mediterraneensis and Lb. fermentum isolates, respectively were bacteriocinogenic. According to the results, Ent. mediterraneensis (L2, L12 and L15), Lb. fermentum (L8, L9 and L10) and S. lutetiensis (L14) are the most promising in vitro probiotic candidates, and require in vivo assessment

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