title: Screening of different probiotic strains for their in vitro ability to metabolise oxalates: any prospective use in humans?
abstract: BACKGROUND
  Oxalate is the salt-forming ion of oxalic acid and can generate oxalate salts combining with various cations, such as sodium, potassium, magnesium, and calcium. Approximately 75% of all kidney stones are composed primarily of calcium oxalate (CaOx) and hyperoxaluria, a condition involving high urinary oxalate concentration, is considered a primary risk factor for kidney stone formation, known as nephrolithiasis. Current therapeutic strategies often fail in their compliance or effectiveness, and CaOx stone recurrence is still common. After an initial stone, there is a 50% chance of forming a second stone within 7 years if the condition is left untreated. The potential therapeutic application of some probiotics, mainly lactobacilli and bifidobacteria, in reducing hyperoxaluria in vivo through intestinal oxalate degrading activity is compelling and initial reports are promising. This study was undertaken to screen different Lactobacillus and Bifidobacterium strains for their capacity to degrade oxalate in vitro using reverse-phase high-performance liquid chromatography (HPLC).
  
  
  METHODS
  The oxalate-degrading activity of 13 lactobacilli and 5 bifidobacteria was tested using a novel HPLC method after growth in a broth culture added with 10 mM ammonium oxalate. Experiments were repeated 3 times. Oxalobacter formigenes (DSM 4420) was used as positive reference to validate HPLC oxalate-degrading capability assays.
  
  
  RESULTS
  Lactobacillus strains were more efficient than bifidobacteria in degrading oxalates. L. paracasei LPC09 (DSM 24243) gave the best result, as 68.5% of ammonium oxalate was converted at the end of incubation, whereas the following best converters belong to the L. gasseri and L. acidophilus species. The relatively low conversion rate observed for most bifidobacteria can probably be attributed to intrinsic oxalate toxicity toward this genus.
  
  
  CONCLUSIONS
  Humans lack the enzymes needed to directly metabolise oxalate, and this potentially toxic compound is, therefore, managed using alternative pathways. As oxalate-degrading bacteria are present in the endogenous microbiota of the human intestine, although with significant individual differences, it is possible to hypothesise that the administration of selected oxalate-degrading probiotics could be an alternative and innovative approach to reducing the intestinal absorption of oxalate and the resulting urinary excretion.
authors.affiliation: Biolab Research Ltd, Novara, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Mogna
authors.forename: Marco
authors.initials: M
authors.lastname: Pane
authors.forename: Stefania
authors.initials: S
authors.lastname: Nicola
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Raiteri
mesh_terms: D001644:Bifidobacterium / Q000145:classification / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D056148:Chromatography, Reverse-Phase; D006801:Humans; D007422:Intestines / Q000382:microbiology*; D007700:Kinetics; D007778:Lactobacillus / Q000145:classification / Q000378:metabolism*; D020347:Lithiasis / Q000175:diagnosis / Q000382:microbiology / Q000628:therapy*; D019815:Oxalic Acid / Q000378:metabolism*; D019936:Probiotics / Q000627:therapeutic use*
chemical_list: D019815:Oxalic Acid