Effect of Streptococcus parvulus and Peptostreptococcus magnus on Cytotoxin Levels of Clostridium difficile in Anaerobic Continuous Flow Culture

Abstract

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 dcile. 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. dcile, 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. Clostridium difficile is regarded as the pathogen of antibiotic-associated diarrhea and pseudomembranous colitis (1, 2). C. difficile is, however, commonly isolated from healthy infants: Stark et al (15) reported that isolation rates were about 60% in babies less than 1 year of age. Furthermore, it was also reported that cytotoxin activity was detected from the fecal specimens of the babies in which C. difficile was isolated (7, 15). These findings seem to indicate that the etiological role of this organism for diarrhea has not been fully understood. Rolfe et al (13) reported that bacterial interference occurred between C. dcile and fecal bacterial flora. Malamou-Ladas et al (8) reported that the growth of C. difficile was inhibited by fecal streptococci. However, investigation on the effect of the bacterial flora on toxin production of C. difficile has not been reported. We had studied the fecal bacterial flora of patients with penicillin-derivatives-associated diarrhea from the ecological point of view. Both C. difficile and its cyto-toxin or enterotoxin were subsequently not detected from the fecal specimens but, 949

Growth inhibition of Clostridium difficile by intestinal flora of infant faeces in continuous flow culture

“…The limited growth of intestinal flora in the colonic ecosystem due to a lack of a carbon source has also been It is reported that intestinal strains compete for various nutrients in CF culture, resulting in inhibition of growth of C. dzficile as described previously.'. 24 Furthermore, the ecological mechanism of the suppressive effect of intestinal flora in cytotoxin production by C. dzficile has been Haslam et ~1 .~~ studied the ability of several strains of C. dzficile to grow in defined culture media and showed that proline, valine, leucine, iso-leucine and tryptophane were essential for growth of C. dzficile. In this study, aspartic acid, citrulline, iso-leucine, leucine, proline, serine and threonine were shown to be utilised well by C. dzficile strains.…”