الفهرس 
Study on Bacteria Producing Antimicrobial Agents against Clostridium difficile Isolated from Human Stool
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Abstract
Clostridium difficile infection (CDI) is a common cause of morbidity and mortality in hospitalized patients worldwide due to the widespread use of antibiotics. The major problem facing current treatment is multiple recurrences, prompting the need for alternative therapies. In this study, six bacterial species were isolated from Egyptian individuals{u2019} stool, with antimicrobial activity against clinical isolates of C. difficile and the stability of the produced antimicrobials was investigated. In vitro antibacterial activity against C. difficile was initially screened in 123 fecal selected consortia using an agar overlay method. The isolates with antimicrobial activity against C. difficile in addition to Clostridium isolates were identified using partial 16S rDNA gene sequencing. The isolates acting against C. difficile belonged to Lactobacillus, Enterococcus and Clostridium genera. The concentrated cell-free supernatants (CFSs) from these bacterial isolates were examined for antimicrobial activity against C. difficile growth by broth dilution method. The 10x concentrated CFSs of five isolates showed inhibition for C. difficile growth which was significantly different (p < 0.001) from control. Lactobacillus agilis T99A and Clostridium butyricum T58A isolates were selected for further evaluation of the produced antimicrobials. The antimicrobial activity of 10x CFSs of the two isolates was sustained after enzymatic treatment with proteinase K or heating treatments up to 90 {u00BA}C or neutralizing pH. The spectrum of activity of the two isolates was evaluated using different gram-positive and gram- negative bacterial species and did not show antimicrobial activity against any of them. Our results showed two unconventional bacterial isolates: L. agilis T99A and C. butyricum T58A producing extracellular thermostable antimicrobial agents against C. difficile clinical isolates