Background The present study aimed (i) to evaluate whether ceftriaxone treatment could affect not only intestinal oxalate-degrading bacteria number but their total activity to degrade oxalate and in uence oxalate homeostasis in rats, (ii) to test the effect of commercially available probiotics and a synbiotic on total fecal oxalate-degrading activity, (iii) and to estimate the ability of synbiotic to restore fecal oxalatedegrading activity and ceftriaxone-induced disruption of oxalate homeostasis in rats.Methods Twenty-eight female Wistar rats (200-300 g) were randomly divided into 4 groups (n = 7). Group 1 was treated with vehicle sterile water (0.1 ml, i.m., 14 days); Group 2 received synbiotic (30 mg/kg, per os, 14 days); Group 3 was treated with ceftriaxone (300 mg/kg, i.m., 7 days); Group 4 was supplemented with ceftriaxone and synbiotic. Oxalate-degrading bacteria number and their total activity, urinary and plasma oxalate concentrations were measured on days 1 and 57 after the treatment withdrawal.Results Ceftriaxone treatment reduced total fecal oxalate-degrading activity independently on oxalatedegrading bacteria number and increased urinary and plasma oxalate concentrations. The synbiotic had a high oxalate-degrading activity vs probiotics and was able to restore fecal oxalate-degrading activity and signi cantly decrease urinary oxalate excretion in antibiotic-treated rats.Conclusion Total fecal oxalate-degrading activity but not oxalate-degrading bacteria number should be thoroughly examined in the future to develop predictive diagnostics methods, targeted prevention and personalized treatment in kidney stone disease. Synbiotic supplementation had a bene cial effect on the total oxalate-degrading activity of gut microbiota, which resulted in decreased UOx excretion in rats.

Introduction: End-stage renal disease (ESRD) patients have significant differences in plasma oxalic acid (POx) concentration under the same treatment conditions. Objectives: In the present study, we adopted the method of redoximetric titration with a KMnO4 solution to evaluate the effect of total fecal oxalate-degrading activity (ODA) on oxalate homeostasis in ESRD patients which has never been reported before. Patients and Methods: A total of 56 participants were enrolled in this cross-sectional pilot study, including 24 healthy volunteers (a control reference group) and 32 ESRD patients. Among the ESRD patients, there were 21 hemodialysis (HD) and 11 peritoneal dialysis (PD) patients. Total ODA in fecal samples as well as POx concentration, daily urinary oxalate (UOx) and PD effluent oxalate excretion were determined. Cohen’s d was computed to calculate the effect size using post-hoc analysis. Results: Total ODA in fecal microbiota ranged from -23 to 24%/0.01 g of feces and was statistically higher in healthy volunteers compared with the ESRD patients. The ESRD patients with positive total fecal ODA status had higher UOx excretion level and lower POx concentration compared with the patients with negative total fecal ODA status. Cohen’s d effect size was 1.99 and 1.05, respectively. Total fecal ODA was an independent risk factor associated with POx elevation in the ESRD patients. Conclusion: Our pilot study firstly demonstrated a potential role of total fecal ODA in oxalate homeostasis in ESRD patients. The results might be useful for determining sample size considerations and providing groundwork for future research projects.

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Background The present study aimed (i) to evaluate whether ceftriaxone treatment could affect not only intestinal oxalate-degrading bacteria number but their total activity to degrade oxalate and influence oxalate homeostasis in rats, (ii) to test the effect of commercially available probiotics and a synbiotic on total fecal oxalate-degrading activity, (iii) and to estimate the ability of synbiotic to restore fecal oxalate-degrading activity and ceftriaxone-induced disruption of oxalate homeostasis in rats. Methods Twenty-eight female Wistar rats (200-300 g) were randomly divided into 4 groups (n = 7). Group 1 was treated with vehicle sterile water (0.1 ml, i.m., 14 days); Group 2 received synbiotic (30 mg/kg, per os, 14 days); Group 3 was treated with ceftriaxone (300 mg/kg, i.m., 7 days); Group 4 was supplemented with ceftriaxone and synbiotic. Oxalate-degrading bacteria number and their total activity, urinary and plasma oxalate concentrations were measured on days 1 and 57 after the treatment withdrawal. Results Ceftriaxone treatment reduced total fecal oxalate-degrading activity independently on oxalate-degrading bacteria number and increased urinary and plasma oxalate concentrations. The synbiotic had a high oxalate-degrading activity vs probiotics and was able to restore fecal oxalate-degrading activity and significantly decrease urinary oxalate excretion in antibiotic-treated rats. Conclusion Total fecal oxalate-degrading activity but not oxalate-degrading bacteria number should be thoroughly examined in the future to develop predictive diagnostics methods, targeted prevention and personalized treatment in kidney stone disease. Synbiotic supplementation had a beneficial effect on the total oxalate-degrading activity of gut microbiota, which resulted in decreased UOx excretion in rats.

Background and Aims Despite evidence suggesting that a lack of fecal oxalate-degrading bacteria colonization is a risk factor for calcium oxalate stone formation, little is known about the oxalate-degrading activity (ODA) in fecal microbiota in end-stage renal disease (ESRD) patients. In addition, to date, there has been a general lack of research on the effect of fecal ODA on oxalate homeostasis in dialysis patients. The present pilot cross-sectional study was performed to compare the oxalate homeostasis profiles depending on ODA in fecal microbiota in ESRD patients. Method The data of a cross-sectional pilot study examining ODA in fecal microbiota, plasma oxalate concentration (POx) and urinary oxalate excretion (UOx) in 32 ESRD patients were represented in this study. Among the patients, there were 21 hemodialysis (HD) patients and 11 peritoneal dialysis (PD) patients. The average age of the patients was 52.5 [39; 65] years. The redoximetric titration with KMnO4 was adopted to evaluate total ODA in fecal microbiota. The results were expressed in % oxalate degradation per 0.01 g of feces. POx concentration and UOx excretion were measured spectrophotometrically using a commercially available kit (MAK-315, Sigma, Spain) and an oxalate oxidase/peroxidase reagent (BioSystems, Spain), respectively. Predialysis plasma samples were collected from HD patients. For further analysis, the patients were allocated to 2 groups according to ODA in feces. Group 1 included the patients with ≥ 1 % oxalate degradation per 0.01 g of feces. Group 2 included the patients with negative ODA (≤ 0 % /0.01 g). For the statistical analysis, we used the nonparametric Kruskal-Wallis test. The median (Me) and interquartile ranges [Q25; Q75] were calculated. The Spearman test was used for the correlation analysis. Univariate logistic regression analysis was used for predicting hyperoxalemia. All statistical analyses were performed using MedCalc. Results ODA in fecal microbiota ranged from -23 to 24 %/0.01 g of feces in ESRD patients and was statistically higher in HD patients compared with PD patients (3.2 [-0.5; 16] vs -4 [-6.5; 6.2], p=0.05). Negative ODA in fecal microbiota (≤ 0 % /0.01 g) was observed in 5/21 (23.8%) HD patients and 7/11 (63.6%) PD patients (χ2=3.9, p=0.04). Consequently, it might be associated with the negative effects of peritoneal dialysis solution. High POx concentration and low UOx excretion were diagnosed in patients with negative ODA in fecal microbiota (Group 2): 30.7 [25.5; 41.5] vs 50 [43.3; 75.5] μmol/L, p=0.01 and 60.9 [51; 65] vs 34.2 [24.4; 39] mg/d, p=0.0002, respectively (Fig. 1). Fecal ODA was directly associated with daily UOx excretion (r=0.85; p<0.0001) (Fig. 2) and had an inverse correlation with POx concentration (r=-0.36; p=0.04) (Fig. 3). In univariate logistic regression analysis, negative fecal ODA was determined as an independent risk factor for high POx concentration (OR: 40; 95% CI: 4.8-331, p<0.0001). Conclusion Our pilot cross-sectional study firstly demonstrated a close association between ODA in fecal microbiota and oxalate homeostasis in ESRD patients: less ODA in fecal microbiota was, higher POx concentration and lower UOx excretion occurred. We suppose that the potential significance of our findings provides preliminary information on the feasibility and necessity of further research in this area.

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Abstract. There is a general lack of research on the long-term effects of acute kidney injury (AKI) on oxalate-degrading bacteria (ODB) and their total oxalate-degrading activity (ODA) in fecal microbiota. In the present pilot study, we separately evaluated the changes in the ODB number and their total ODA in fecal microbiota at 3-time points after glycerol-induced AKI. In addition, we assessed the interactions between AKI-induced renal histopathological changes and ODB, total fecal ODA, and plasma and urine oxalate concentrations in rats. Methods. The male Wistar rats (200-300 g, n = 20) on oxalate-free diet were randomly divided into 2 groups. After 24-h of water deprivation, experimental group 1 (n = 10) received an intramuscular injection of 50% glycerol (10 ml/kg of body weight), and group 2 (n = 10) served as a control. The numbers of ODB (incubated in a highly selective Oxalate Medium and determined using the culture method), total fecal ODA and urinary oxalate (UOx) excretion were measured after injection on days 8, 22 and 70. The method of redoximetric titration with a KMnO4 solution was adopted to evaluate total ODA in fecal microbiota. Renal injury was assessed by histopathology examination, serum creatinine plasma oxalic acid (POx) concentration and daily proteinuria levels after removing the animals from the experiment on day 70. Results. After glycerol injection on days 8 and 22, no differences were found in the numbers of ODB, their total fecal ODA, and UOx excretion level between the experimental and control groups. However, after AKI initiation on day 70, the numbers of ODB, total fecal ODA, and daily UOx excretion were significantly lower in the experimental group as compared with the control group. In addition, in 10 weeks following AKI, the number of ODB had a direct correlation with UOx excretion and an inverse correlation with POx and serum creatinine concentrations and daily proteinuria. Total ODA in fecal microbiota was directly associated with the percentage of renal interstitial fibrosis and the average glomerular volumes in the experimental rats. Conclusions: AKI had long-term negative effects on the quantitative and qualitative characteristics of ODB in fecal microbiota in rats. Moreover, the results of our study confirmed an increasing trend in total fecal ODA according to the aggravation of renal interstitial fibrosis and glomerular volume in rats’ kidneys. Further studies are warranted to gain more insight into the mechanism of oxalate homeostasis impairment in AKI.