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Oxalobacter formigenes is an oxalate-degrading anaerobic bacterium that colonizes the large intestine of numerous vertebrates, including humans. O. formigenes and humans share a beneficial symbiosis.
Quinolone, a broad-spectrum antibiotic, kills O. formigenes. If a person's gastrointestinal tract lacks this bacterium, and therefore lacks the primary source for the Oxalyl-CoA decarboxylase enzyme, then the GI tract cannot degrade calcium oxalate. Such an imbalance may facilitate the formation of calcium oxalate-based kidney stones.