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Animal and human studies have provided compelling evidence that colonization of the intestine with Oxalobacter formigenes reduces urinary oxalate excretion and lowers the risk of forming calcium oxalate kidney stones. The mechanism providing protection appears to be related to the unique ability of O. formigenes to rely on oxalate as a major source of carbon and energy for growth. However, much is not known about the factors that influence colonization and host-bacterium interactions. We have colonized mice with O. formigenes OxCC13 and systematically investigated the impacts of diets with different levels of calcium and oxalate on O. formigenes intestinal densities and urinary and intestinal oxalate levels. Measurement of intestinal oxalate levels in mice colonized or not colonized with O. formigenes demonstrated the highly efficient degradation of soluble oxalate by O. formigenes relative to other microbiota. The ratio of calcium to oxalate in diets was important in determining colonization densities and conditions where urinary oxalate and fecal oxalate excretion were modified, and the results were consistent with those from studies we have performed with colonized and noncolonized humans. The use of low-oxalate purified diets showed that 80% of animals retained O. formigenes colonization after a 1-week dietary oxalate deprivation. Animals not colonized with O. formigenes excreted two times more oxalate in feces than they had ingested. This nondietary source of oxalate may play an important role in the survival of O. formigenes during periods of dietary oxalate deprivation. These studies suggest that the mouse will be a useful model to further characterize interactions between O. formigenes and the host and factors that impact colonization. Oxalobacter formigenes is a Gram-negative, obligate anaerobic bacterium that requires oxalate as a carbon source for energy and growth (1). O. formigenes is part of the microbiota in the large intestine of many humans and other mammalian species (1-6). A review of colonization frequencies conducted worldwide indicated that 38% to 77% of a normal population is colonized with O. formigenes (7). Recent evidence suggests that a lack of colonization with this oxalate-degrading specialist is a risk factor for idiopathic recurrent calcium oxalate kidney stone disease (8,9). Controlled diet studies in healthy human subjects have also indicated that O. formigenes-colonized individuals excrete significantly less oxalate in 24-hour urine collections when they consume diets containing moderate oxalate (250 mg) and low calcium (400 mg) levels (10).Little is known about how and when individuals become colonized or how O. formigenes persists over time. Studies to date suggest it occurs early in childhood (11), and if animal experiments provide any insight, it is obtained from the environment, not directly from the mother (12). Several studies have indicated that the intake of antibiotics can result in the loss of colonization (7,(13)(14)(15), and this is supported by decreased prevalence...

Colonization with Oxalobacter formigenes may reduce the risk of calcium oxalate kidney stone disease. To improve our limited understanding of host-O. formigenes and microbe-O. formigenes interactions, germfree mice and mice with altered Schaedler flora (ASF) were colonized with O. formigenes. Germfree mice were stably colonized with O. formigenes, which suggests that O. formigenes does not require other organisms to sustain its survival. Examination of intestinal material indicated no viable O. formigenes in the small intestine and ϳ4 ؋ 10 6 CFU O. formigenes per 100 mg contents in the cecum and proximal colon, with ϳ0.02% of total cecal O. formigenes cells being tightly associated with the mucosa. O. formigenes did not alter the overall microbial composition of ASF, and ASF did not affect the capacity of O. formigenes to degrade dietary oxalate in the cecum. Twentyfour-hour collections of urine and feces in metabolic cages in semirigid isolators demonstrated that the introduction of ASF into germfree mice significantly reduced urinary oxalate excretion. These experiments also showed that O. formigenes-monocolonized mice excreted significantly more urinary calcium than did germfree mice, which may be due to degradation of calcium oxalate crystals by O. formigenes and subsequent intestinal absorption of free calcium. In conclusion, the successful establishment of mouse models with defined flora and O. formigenes should improve our understanding of O. formigenes-host and O. formigenes-microbe interactions. These data support the use of O. formigenes as a probiotic that has limited impact on the composition of the resident microbiota but provides an efficient oxalate-degrading function. Oxalobacter formigenes is part of the bacterial flora in the large intestine of many humans and other mammalian species and is unique in that it is the only bacterium yet identified in the intestines of mammals that requires oxalate as both an energy source and a carbon source. Recent evidence suggests that a lack of colonization with this oxalate-degrading specialist is a risk factor for idiopathic recurrent calcium oxalate stone disease (1, 2). A review of worldwide data indicated that 38% to 77% of a normal population and only 17% of stone formers were colonized with O. formigenes (1). The ability to recolonize individuals lacking O. formigenes was previously addressed in a study in which two healthy adults not colonized with O. formigenes became colonized following the ingestion of cultured O. formigenes (3) and remained colonized for 9 months. However, studies in which O. formigenes was provided in either a lyophilized form in enteric coated capsules or as a frozen paste to patients suffering from primary hyperoxaluria resulted in only a minority of the patients remaining colonized posttreatment (4, 5). Therefore, although it seems quite possible that O. formigenes colonization of noncolonized stone formers may be an effective way to minimize the risk of recurrent calcium oxalate stone disease, a better understanding o...

OBJECTIVE 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. METHODS Probiotic supplements and pure cultures of O. formigenes were cultured in a number of media containing oxalate. 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 PCR. RESULTS Incubating probiotic supplements in different media did not result in growth of oxalate-degrading organisms. PCR indicated the absence of organisms harboring the oxc gene. Culture and 16S rRNA gene sequencing indicated the ™PRO Lab supplement contained viable Lactococcus lactis subsp. lactis (GenBank accession no. KJ095656.1), while Oxalo™ contained several Bacillus species and Lactobacillus plantarum. CONCLUSION 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.

Oxalobacter formigenes (O. formigenes) is a nonpathogenic, Gram-negative, obligate anaerobic bacterium that commonly inhabits the human gut and degrades oxalate as its major energy and carbon source. Results from a case-controlled study suggested that lack of O. formigenes colonization is a risk factor for recurrent calcium oxalate stone formation. Hence, O. formigenes colonization may prove to be an efficacious method for limiting calcium oxalate stone risk. However, challenges exist in the preparation of O. formigenes as a successful probiotic due to it being an anaerobe with fastidious growth requirements. Here we examine in vitro properties expected of a successful probiotic strain. The data show that the Group 1 O. formigenes strain OxCC13 is sensitive to pH < 5.0, persists in the absence of oxalate, is aerotolerant, and survives for long periods when freeze-dried or mixed with yogurt. These findings highlight the resilience of this O. formigenes strain to some processes and conditions associated with the manufacture, storage and distribution of probiotic strains.