"In vitro" effect of Egyptian tannin-containing plants and their extracts on the survival of pathogenic bacteria.

This study was conducted on leaves from tannin containing plants which are widely spread in Upper Egypt. From two plants also fruits were investigated (A. nilotica and A. farnesiana). One of the objectives was to determine the total soluble polyphenols and the soluble condensed tannins of these plants. Furthermore the assumed antimicrobial effect of A. nilotica and A. farnesiana leaves and their extracts on C. perfringens, E. coli and S. typhimurium was studied "in-vitro" at dilutions of 0.5% and 0.05%. The tests were carried out in physiological saline solution and in rumen fluid medium (RFM). The results revealed that the total soluble polyphenols ranged from 10.27% to 35.46% and the condensed tannins from 0.5% to 8.28% on dry matter base. The antimicrobial effect of the plant material was only observed on C. perfringens but not on E. coli and S. typhimurium. A. nilotica leaves destroyed the suspension of C. perfringens immediately after being added. Leaves from A. farnesiana showed a delayed affect. Plant extracts were less effective than the raw plant material. In RFM A. nilotica leaves destroyed the bacterial suspension after 10 minutes only at the concentration of 0.5%, but not at 0.05%. With A. farnesiana at a concentration of 0.5% only a reduction was observed. The concentration of 0.05% had no influence. The presence of other proteins than bacterial suspension in rumen fluid (rumen bacteria, protozoa and plant proteins) inhibits the antimicrobial effect of the plant material in a concentration of 0.05%, but not at 0.5%.(ABSTRACT TRUNCATED AT 250 WORDS)