Fundamental Studies on the Growth of Clostridium difficile

The Effect of Medium pH on the Germination & Proliferation of Spores

Abstract

The present study was undertaken to investigate the inhibitory factors against the outbreak of antibiotic associated colitis caused by Clostridium difficile using two in vitro procedures.
Although the growth of C. difficile No.202 vegetative cells was scarcely influenced in the mixed culture with Bifidobacterium adolescentis No.16, the yield of spores was significantly decreased, as compared with that in monoculture of C. difficile No.202.
When inoculated alone, C. difficile No.202 spores began to germinate and proliferate after incubation for 12 hrs with culture pH and O-R potential being 6.9 and-360 mV, respectively. In the mixed culture with B. adolescentis No.16, which lowered pH of the culture to 5.3 with O-R potential being-300 mV after incubation for 12 hrs, the proliferation of C. difficile No.202 spores was inhibited for 48 hrs.
The effect of the initial pH of medium against germination and proliferation of C. difficile No.202 spores was examined using BHI broth as a basal meidum and acetic acid as a pH determinant. The drop in initial pH displayed an extensive impact on the time-course growth of C. difficile No.202 showing delay of germination of spores in proportion to lowering of pH and the proliferation of spores was completely inhibited at pH 5.72.
These results indicate that acidic pH due to short-chain fatty acids produced by normal bacterial flora plays an important role to prevent the germination and proliferation of C. difficile spores in the gastrointestinal tract.