Enhancement of Clostridium difficile toxin production in biotin-limited conditions

Abstract

The effect of biotin on toxin production by Clostridium diffile was examined in a defined medium. When toxin production by strain KZ 1647, which was isolated from a healthy adult, was examined in relation to its biotin requirement, it was found that with decreasing concentrations of biotin, bacterial growth was decreased, but production of both toxins A and B were remarkably increased, particularly with 0.05 nM biotin. The time course of production of both toxins in biotin-limited conditions was similar to that in biotin-enriched conditions. The biotin effect on toxin production was also observed in 15 other strains, suggesting that the effect occurs frequently amongst toxigenic C. difficile strains. The biotin effect is discussed in relation to the pathogenesis of C. diffile colitis.

Inhibition of enhanced toxin production by Clostridium difficile in biotin-limited conditions

“…This strain showed a typical response of enhanced toxin production in a biotin-limited defined medium [6].…”

“…Bacterial growth was determined by measuring the optical density of cultures at 560 nm as described previously [6]. Levels of toxins A and B in culture supernates and in sonicated cell extracts were determined by an enzyme-linked immunosorbent assay and by a conventional cytotoxicity assay with baby hamster kidney cells, respectively, as reported previously [6].…”

“…A biotin-limited defined medium [6] containing biotin (0.05 nM) and the following amino acids, tryptophan, methionine, valine, is0 leucine, proline, leucine, cysteine, glycine and threonine, was used. The medium was inoculated for toxin production as described previously [6] and incubated anaerobically at 37°C for 5 days.…”

“…The medium was inoculated for toxin production as described previously [6] and incubated anaerobically at 37°C for 5 days. To evaluate the effect of a test compound 0.2 ml of the concentrated solution (pH 7.4) was added to a culture medium (10 ml) while flushing with oxygen-free gas.…”

“…The bacterium produces toxins A and B [l-51. An earlier study showed that the production of these toxins by C. d$cile is enhanced in a biotin-limited defined medium (biotin effect) and it was hypothesised that administration of excess biotin to a patient with C. dfjcile colitis may have a therapeutic effect [6].…”