Sacral neuromodulation device biofilm differs in the absence and presence of infection, harbors antibiotic resistance genes, and is reproducible in vitro.

INTRODUCTION/PURPOSE: Sacral neuromodulation (SNM) is effective therapy for overactive bladder refractory to oral therapies, and non-obstructive urinary retention. A subset of SNM devices is associated with infection requiring surgical removal. We sought to compare microbial compositions of explanted devices in the presence and absence of infection, by testing phase, and other clinical factors, and to investigate antibiotic resistance genes present in the biofilms. We analyzed resistance genes to antibiotics used in commercially-available anti-infective device coating/pouch formulations. We further sought to assess biofilm reconstitution by material type and microbial strain in vitro using a continuous-flow stir tank bioreactor, which mimics human tissue with an indwelling device. We hypothesized that SNM device biofilms would differ in composition by infection status, and genes encoding resistance to rifampin and minocycline would be frequently detected. MATERIALS/METHODS: Patients scheduled to undergo removal or revision of SNM devices were consented per IRB-approved protocol (IRB 20-415). Devices were swabbed intraoperatively upon exposure, with controls and precautions to reduce contamination of the surrounding field. Samples and controls were analyzed with next-generation sequencing and RT-PCR, metabolomics, and culture-based approaches. Associations between microbial diversity or microbial abundance, and clinical variables were then analyzed using t-tests and ANOVA. Reconstituted biofilm deposition in vitro using the bioreactor was compared by microbial strain and material type using plate-based assays and scanning electron microscopy. RESULTS: Thirty seven devices were analyzed, all of which harbored detectable microbiota. Proteobacteria, Firmicutes and Actinobacteriota were the most common phyla present overall. Beta-diversity differed in the presence versus absence of infection (p = 0.014). Total abundance, based on normalized microbial counts, differed by testing phase (p < 0.001), indication for placement (p = 0.02), diabetes mellitus (p < 0.001), cardiac disease (p = 0.008) and history of UTI (p = 0.008). Significant microbe-metabolite interaction networks were identified overall and in the absence of infection. 24% of biofilms harbored the tetA tetracycline/minocycline resistance gene and 53% harbored the rpoB rifampin resistance gene. Biofilm was reconstituted across tested strains and material types. Ceramic and titanium did not differ in biofilm deposition for any tested strain. CONCLUSIONS: All analyzed SNM devices harbored microbiota. Device biofilm composition differed in the presence and absence of infection and by testing phase. Antibiotic resistance genes including to rifampin and tetracycline/minocycline, which are used in commercially-available anti-infective pouches, were frequently detected. Isolated organisms from SNM devices demonstrated the ability to reconstitute biofilm formation in vitro. Biofilm deposition was similar between ceramic and titanium, materials used in commercially-available SNM device casings. The findings and techniques used in this study together provide the basis for the investigation of the next generation of device materials and coatings, which may employ novel alternatives to traditional antibiotics. Such alternatives might include bacterial competition, quorum-sensing modulation, or antiseptic application, which could reduce infection risk without significantly selecting for antibiotic resistance.

Deficient butyrate metabolism in the intestinal microbiome is a potential risk factor for recurrent kidney stone disease.

Intestinal microbiome dysbiosis is a known risk factor for recurrent kidney stone disease (KSD) with prior data suggesting a role for dysfunctional metabolic pathways other than those directly utilizing oxalate. To identify alternative mechanisms, the current study analyzed differences in the metabolic potential of intestinal microbiomes of patients (n = 17) and live-in controls (n = 17) and determined their relevance to increased risk for KSD using shotgun metagenomic sequencing. We found no differences in the abundance of genes associated with known oxalate degradation pathways, supporting the notion that dysfunction in other metabolic pathways plays a role in KSD. Further analysis showed decreased abundance of key enzymes involved in butyrate biosynthesis in patient intestinal microbiomes. Furthermore, de novo construction of microbial genomes showed that the majority of genes significantly enriched in non-stone formers are affiliated with Faecalibacterium prausnitzii, a major butyrate producer. Specifically pertaining to butyrate metabolism, the majority of abundant genes mapped back to F. prausnitzii, Alistipes spp., and Akkermansia muciniphila. No differences were observed in ascorbate or glyoxylate metabolic pathways. Collectively, these data suggest that impaired bacterial-associated butyrate metabolism may be an oxalate-independent mechanism that contributes to an increased risk for recurrent KSD. This indicates that the role of the intestinal microbiome in recurrent KSD is multi-factorial, which is representative of the highly intertwined metabolic nature of this complex environment. Future bacteria-based treatments must not be restricted to targeting only oxalate metabolism.

An exploratory study investigating the impact of the bladder tumor microbiome on Bacillus Calmette Guerin (BCG) response in non-muscle invasive bladder cancer.

PURPOSE: Intravesical Bacillus Calmette-Guerin (BCG) is standard of care for intermediate- and high-risk non-muscle invasive bladder cancer (NMIBC). The effect of the bladder microbiome on response to BCG is unclear. We sought to characterize the microbiome of bladder tumors in BCG-responders and non-responders and identify potential mechanisms that drive treatment response. MATERIALS AND METHODS: Patients with archival pre-treatment biopsy samples (2012-2018) were identified retrospectively. Prospectively, urine and fresh tumor samples were collected from individuals with high-risk NMIBC (2020-2023). BCG response was defined as tumor-free 2 years from induction therapy. Extracted DNA was sequenced for 16S rRNA and shotgun metagenomics. Primary outcomes were species richness (α-diversity) and microbial composition (ß-diversity). Paired t-tests were performed for α-diversity (Observed species/Margalef). Statistical analysis for ß-diversity (weighted and unweighted UniFrac distances, weighted Bray-Curtis dissimilarity) were conducted through Permanova, with 999 permutations. RESULTS: Microbial species richness (P < 0.001) and composition (P = 0.001) differed between BCG responders and non-responders. Lactobacillus spp. were significantly enriched in BCG-responders. Shotgun metagenomics identified possible mechanistic pathways such as assimilatory sulfate reduction. CONCLUSION: A compositional difference exists in the tumor microbiome of BCG responders and non-responders with Lactobacillus having increased abundance in BCG responders.