Effect of environmental stress on Clostridium difficile toxin levels during continuous cultivation

A method for the continuous culture of C. difficile has been described. It has been shown that subjecting continuous cultures of this microorganism to environmental stress results in increased levels of toxin in culture medium. Factors found to cause this release include alteration of the Eh from -360 to +100 mV or increasing the temperature from 37 to 45°C. The increased toxin levels were not associated with a change in viable cell density or the numbers of spores present. Additional studies have shown that subinhibitory concentrations of vancomycin and penicillin, but not clindamycin, also cause an increase in toxin levels during continuous culture. The increase in supernatant toxin levels occurs concomitant with a decrease in sonicated cell extract toxin levels. The data suggest that a number of factors can cause a release of toxin from C. difficile into the surrounding medium.