To examine the levels of Oxalobacter formigenes in probiotic supplements marketed by PRO-LAB, Ltd, Toronto, Canada, and capsules of Oxalo purchased from Sanzyme Ltd, Hyderabad, India, and to measure the ability of these preparations to degrade oxalate in vitro.

Probiotic supplements and pure cultures of O. formigenes were cultured in a number of media containing oxalate. Optical density at 595 nm (OD₅₉₅) was used to measure bacterial growth, and ion chromatography was used to measure loss of oxalate in culture media. O. formigenes–specific and degenerate Lactobacillus primers to the oxalate decarboxylase gene (oxc) were used in polymerase chain reaction (PCR).

Incubating probiotic supplements in different media did not result in the growth of oxalate-degrading organisms. PCR indicated the absence of organisms harboring the oxc gene. Culture and 16S ribosomal ribonucleic acid gene sequencing indicated the PRO-LAB supplement contained viable Lactococcus lactis subsp. lactis (GenBank accession no. KJ095656.1), whereas Oxalo contained several Bacillus species and Lactobacillus plantarum.

The probiotic supplement sold over the Internet by PRO-LAB Ltd and Sanzyme Ltd did not contain identifiable O. formigenes or viable oxalate-degrading organisms, and they are unlikely to be of benefit to calcium oxalate kidney stone patients.