Oxalobacter formigenes and kidney stones

My interest in my microbiome piqued when I got my first kidney stone at age 52. I figured I didn't have a genetic disposition to kidney stones since I would have had them much earlier in my life. In terms of demographics; kidney stone prevalence increases with age until age 70, then declines and is higher in men than women and in whites than blacks [1]. So I met the demographic profile of a middle-aged white guy with kidney stones, but what in me changed to make me susceptible to kidney stones? My diet was consistent, perhaps something changed in my gut. So I searched on kidney stones and microbiome.

Up to 80% of kidney stones are predominantly composed of calcium oxalate (CaOx). - of which mine was. Kaufman et al. observed a strong inverse association between colonization with O. formigenes and recurrent CaOx renal stones, with a 70% reduction in overall risk [2]. They also go on to say that the prevalence of O. formigenes was related to the use of antibiotics, to which the bacterium has been previously reported to be sensitive. Interestingly, they reference an Ukrainian study detailing that the oxalate-degrading gut microbe is acquired by children at a young age (between ages 6 and 8) and declines to approximately 75% by age 12. Makes you wonder how this naturally occurring bacterium which uses dietary oxalate as a major energy source and degrades it in your colon instead of being peed out via your kidneys colonizes the human gut.

The lifetime incidence of kidney stones is nearly 13 percent in men and 7 percent in women. Duncan et al. states that this bacterium may be lost from the gut over time through antibiotic use and it is only detected in the feces of 60 to 80% of adults [3]. So what to do if you are that percentile of adults prone to kidney stones and no O. formigenes to speak of in your colon?

Well there is a company called OxThera developing an O. formigenes probiotic called Oxabact®. If you cannot wait for Oxabact® to hit the market, there is still hope. There are a few other generalist intestinal bacteria that are able to consume oxalates; including strains of Lactobacillus and Bifidobacterium which are commonly found in yogurt and kefir [2].

An article by Tasian et al. (2018) suggests that people who took five common types of oral antibiotics had a greater chance of developing kidney stones within a year [4].  They were:

• sulfas
• broad-spectrum penicillins
• fluoroquinolones
• cephalosporins
• nitrofurantoin/methenamine

Sources:
[1] Kidney Int. 1994 Sep;46(3):893-9.
[2 J Am Soc Nephrol. 2008 Jun; 19(6): 1197–1203. doi: 10.1681/ASN.2007101058
[3] Appl Environ Microbiol. 2002 Aug; 68(8): 3841–3847. doi: 10.1128/AEM.68.8.3841-3847.2002
[4] Journal of the American Society of Nephrology : JASN [10 May 2018, 29(6):1731-1740]