Isolation and characterisation of intestinal spirochaetes

Faeces or rectal swabs from 1527 subjects were examined for the presence of intestinal spirochaetes by anaerobic culture on blood agar incorporating spectinomycin (400 mg/l). Twenty three specimens (1.5%) were positive, and only one of these came from a patient with diarrhoea. All positive specimens came from either Asians or known homosexuals. Comparative tests showed a close phenotypic similarity between the human isolates and non-pathogenic porcine intestinal spirochaetes. These organisms differ from Brachyspira aalborgi, a spirochaete isolated from subjects with histologically confirmed intestinal spirochaetosis.