Effect of Streptococcus parvulus and Peptostreptococcus magnus on cytotoxin levels of Clostridium difficile in anaerobic continuous flow culture

An anaerobic continuous flow (CF) culture method was used in order to study the effect of Peptostreptococcus magnus and Streptococcus parvulus, anaerobic gram-positive cocci which are members of intestinal bacterial flora, on growth and cytotoxin-activity of Clostridium difficile. The growth- and the cytotoxin activity-patterns of C. difficile in an established CF culture of P. magnus were similar to those of C. difficile alone. On the other hand, in the mixed culture system of C. difficile and S. parvulus, the cytotoxin levels were significantly lower as compared with C. difficile alone in spite of the fact that no differences existed between growth of C. difficile in mixed and single culture systems. The culture filtrate of P. magnus did not influence the growth and cytotoxin production of C. difficile, nor did that of S. parvulus have any effect on growth of C. difficile in static culture. The cytotoxin activity of C. difficile was, however, suppressed by the culture filtrate of S. parvulus. Furthermore, when P. magnus or S. parvulus was statically cultured in a medium containing cytotoxic culture filtrate of C. difficile, the toxin in the medium was not inactivated.