In vitro effects of sulphasalazine, azodisal sodium, and their metabolites on Clostridium difficile and some other faecal bacteria.

The effects of sulphasalazine (SASP), azodisal sodium (ADS), and their metabolites were tested in vitro on aerobic and anaerobic faecal bacterial strains. Sulphapyridine (SP) had a mild to moderate effect on Escherichia coli and Streptococcus faecalis. SASP also had a growth-inhibitory effect on Strep. faecalis. The other substances had no effect on the aerobic strains. SASP, SP, 5-aminosalicylic acid, and, to a certain extent, N-acetyl-5-aminosalicylic acid exerted a growth-inhibitory effect on the anaerobic strains. Of special interest was the inhibitory effect on Clostridium difficile strains. In recent years the possibility that overgrowth of Cl. difficile could cause flare-ups of inflammatory bowel disease has been discussed. Some studies suggested that SASP treatment could predispose to Cl. difficile superinfection, whereas others found SASP more probable to exert a prophylactic effect. Our findings support the theory that SASP treatment reduces rather than promotes the risk of Cl. difficile superinfection.