Abstract
Oxalobacter formigenes, an anaerobic bacterium that degrades oxalate to CO2 and formate, colonises the intestinal tracts of man and other animals. In this study, the large intestines of laboratory rats were experimentally colonised with a strain of O. formigenes to examine effects of these bacteria on the fate of dietary oxalate. When rats (n = 6) were fed a standard rat diet plus 2 per cent sodium oxalate, urinary oxalate excretion was not significantly changed following inoculation and colonisation with O. formigenes. There was a consistent trend towards less oxalate excretion in faeces of rats after they became colonised with O. formigenes, but differences between colonised and non-colonised states were not significant. In an isotope recovery study, when rats were orally dosed with [14C]oxalate, the percentage of 14C in expired CO2 from three colonised rats was 10-fold greater than from three non-colonised rats. Although 14C excretion in faeces was decreased three-fold in the group of colonised rats, 14C activity in the urine of colonised and non-colonised rats was not significantly different. Thus, although O. formigenes colonised and degraded oxalate in the rat intestinal tract, under conditions of these experiments, this colonisation did not markedly influence urinary oxalate excretion.