Oxalobacter formigenes is a bacterium residing in the human gut that consumes oxalate ingested through food or produced as a waste product by the body. High levels of oxalate, a compound found naturally in many plant foods, can be a health concern when absorbed into the bloodstream. Once in circulation, oxalate is filtered by the kidneys, where it combines with calcium to form calcium oxalate crystals, the main component of most kidney stones. The lack of this oxalate-degrading bacterium is associated with an increased risk of developing recurrent calcium oxalate kidney stones and hyperoxaluria.
The Role of Oxalobacter formigenes in Oxalate Metabolism
Oxalobacter formigenes is a Gram-negative, obligate anaerobic bacterium, meaning it cannot survive in the presence of oxygen. This organism uses oxalate as its sole source of energy and carbon for growth, employing a specialized enzyme system to break down oxalate into simpler compounds like carbon dioxide and formate.
Oxalate degradation occurs in the large intestine before the compound can be absorbed into the body. O. formigenes utilizes the protein OxlT to exchange external oxalate for internally produced formate, a mechanism that drives its energy production. By rapidly metabolizing oxalate in the gut, the bacterium significantly reduces the concentration available for absorption into the bloodstream.
This reduction in intestinal oxalate load decreases the amount of oxalate excreted by the kidneys, lowering the risk of calcium oxalate precipitation in the urinary tract. The presence of O. formigenes also promotes the active secretion of oxalate from the blood back into the colon, further reducing systemic levels. Colonization with this bacterium can be compromised by broad-spectrum antibiotics, as it is highly sensitive to many common antimicrobial agents.
Current Commercial Availability and Regulatory Status
Despite the scientific evidence supporting the health benefits of O. formigenes, a widely available, over-the-counter probiotic supplement containing viable bacteria is not currently on the market. The primary obstacle is the bacterium’s nature as a strict anaerobe with fastidious stability requirements. Maintaining the viability of O. formigenes in a shelf-stable capsule, particularly through the acidic stomach, presents a significant manufacturing challenge.
Any product intended to treat a specific medical condition, such as hyperoxaluria, must undergo rigorous testing and is classified as an investigational drug, not a dietary supplement. The product known as Oxabact (OC5), a highly concentrated, freeze-dried preparation of O. formigenes, has undergone extensive clinical trials. These trials focused primarily on patients with Primary Hyperoxaluria, a rare genetic disorder involving the overproduction of oxalate.
Although the Oxabact trials demonstrated that the bacterium could be successfully established in the gut, the large-scale Phase 3 study narrowly missed its primary endpoint of reducing urinary oxalate excretion compared to placebo. While the treatment was deemed safe and well-tolerated, it remains an investigational product not commercially available to the public. Furthermore, several commercial supplements claiming to contain O. formigenes have been analyzed and found not to contain detectable, viable organisms, raising concerns about product efficacy.
Therapeutic Alternatives for Oxalate Reduction
Since direct access to a proven O. formigenes probiotic is restricted to clinical trial settings, individuals concerned about oxalate levels must rely on alternative therapeutic strategies. Dietary management is a fundamental approach, focusing on two principles: limiting the intake of high-oxalate foods and ensuring proper hydration. Foods such as spinach, rhubarb, almonds, and chocolate contain high concentrations of oxalate, and reducing their consumption lowers the overall oxalate load.
Drinking sufficient water, often recommended at three to four liters daily for adults, helps dilute the urine, making it more difficult for calcium and oxalate to crystallize. A highly effective strategy involves consuming calcium-rich foods or a calcium supplement along with meals. The calcium binds to oxalate in the gut, forming an insoluble compound that is excreted in the stool, preventing its absorption.
Certain commercially available probiotics containing strains of Lactobacillus and Bifidobacterium possess some oxalate-degrading activity, although they are substantially less efficient than O. formigenes. For severe hyperoxaluria, newer pharmaceutical treatments like RNA interference therapies have been approved for specific genetic forms of the condition. These treatments reduce the body’s own production of oxalate.