Diversity of faecal oxalate-degrading bacteria in black and white South African study groups: insights into understanding the rarity of urolithiasis in the black group

Abstract

Aim: To examine whether enhanced diversity or numbers of oxalate-degrading bacteria in the gastrointestinal tracts of black South Africans play a role in determining the rarity of urolithiasis in this group. Methods and Results: Fresh faecal samples collected from healthy black and white South African male volunteers were analysed in terms of bacterial oxalate-degrading activity, bacterial diversity and relative species abundance. Varied bacterial populations prepared from samples from the low-risk black group showed a significantly higher level of oxalate degradation. Denaturing gradient gel electrophoresis analyses of Lactobacillus and related spp. and Bifidobacterium spp. 16S rRNA PCR products revealed a significantly higher faecal Lactobacillus diversity for the low-risk black group relative to the higherrisk white group. Quantitative real-time PCR experiments did not show any significant differences between the study groups for Lactobacillus and related spp.. However, Bifidobacterium spp. were present at a significantly higher relative abundance in the black group. Oxalobacter formigenes was present only at very low levels in either group. Conclusions: The low abundance of O. formigenes and increased diversity and abundance of oxalate-degrading Lactobacillus and Bifidobacterium spp. in the black South African population suggest that these strains rather than O. formigenes may protect this group against calcium oxalate kidney stone disease. Significance and Impact of the Study: The South African black population harbours a pool of potential oxalate-degrading lactic acid bacteria, which is more abundant and diverse than that of white South Africans. This may be useful in developing probiotics for calcium oxalate kidney stone prophylaxis.

Dietary hyperoxaluria is not reduced by treatment with lactic acid bacteria

“…Magwira et al suggested that Lactobacillus and Bifidobacterium spp. rather than Oxalobacter formigenes may protect black South Africans against calcium oxalate stone disease due to the increased diversity and abundance of these oxalate-degrading strains and low abundance of Oxalobacter formigenes in this group [23]. …”

Compositional and Functional Features of the Gastrointestinal Microbiome and Their Effects on Human Health

“…GI bacteria such as Oxalobacter formigenes, Lactobacillus spp., and Bifidobacterium spp. can metabolize oxalate in the intestine and might reduce risk for kidney stones (58, 59). O formigenes is a strict colonic anaerobe that provides one of the few clearly demonstrated health benefits of the intestinal microbiome.…”

The role of the microbiome in kidney stone formation

“…Recently, Hatch et al demonstrated that Bifidobacterium lacti s colonization decreases urinary oxalate by degrading dietary oxalate and reducing its intestinal absorption in a mouse model [8]. In a study of South African men, Lactobacillus species with high oxalate degrading capacity have been identified and associated with a lower prevalence of calcium oxalate kidney stones [9]. …”