Isolation and evaluation of susceptibility to sulphasalazine of Desulfovibrio desulfuricans strains from the human digestive tract.

Various genera of sulphate reducing bacteria (SRB) have been found in the human digestive tract. It is suggested that some of SRB species may be responsible for the development of the clinical symptoms of ulcerative colitis and other disease of large intestine. Sulphasalazine (salicyl-azo-sulphapyridine, SAS) is commonly used to treat patients with ulcerative colitis and Crohn disease. Above 30 samples of faeces or biopsy specimens from 25 patients (age 45 +/- 14 years; M/F, 13/12) suffering from gastrointestinal disorders were used for isolation of Desulfovibrio desulfuricans species. The morphological, physiological and biochemical characteristics of isolated strains and also their susceptibility to SAS was determined. D. desulfuricans isolates were obtained from 5 amongst all patients assayed. Some abnormal, cigar-shaped cells were detected as accompanying the cells represented by rods, curved rods and vibrios. After strains purification, two types of colonies were present on the solid Postgate's medium B (containing lactate as a carbon source and sulphate for energy conservation): the black colonies growing in bulk of agar medium and the transparent, surface-growing mucous colonies. These two types of D. desulfuricans colonies may be a result of different iron availability for bacterial cells. High metabolic activity of strain was not always accompanied by the presence of H2S gas lock in the test tube, although the H2S odor was perceptible. All tested strains multiplied inconsiderably slowly in the presence of SAS at concentrations 10, 20, 40 and 60 mg/cm3. The growing concentrations of SAS did not cause a proportional decrease of the bacterial cells number. Taking into account the positive results of using SAS to treat patients with some colonic diseases and the indicated resistance to SAS of intestinal D. desulfuricans strains, it appears probable, that this SRB species isn't responsible for the development of mentioned diseases.