The Kidney Stone Microbiome is Comprised of Antibiotic-Resistant, Biofilm-Forming Bacteria, Which Has Implications for the Etiology of Lithogenesis

Document Type

Conference Proceeding

Publication Date

9-22-2023

Publication Title

J Endourol

Abstract

Introduction: Evidence suggests that urinary stone disease (USD) is associated with the urinary tract microbiome, termed urobiome. We and others have shown a strong association between USD and past antibiotic use. Furthermore, there is increasing evidence that active biofilm formation is present in calcium- based stones. These data present the hypothesis that antibiotic resistant, biofilm-forming bacteria promote the lithogenesis of calcium-based stones. Methods: To test our hypothesis, we obtained calcium oxalate or calcium phosphate stones surgically extracted through percutaneous nephrolithotomy or ureteroscopy. Stone fragments were rinsed with sterile PBS to remove non-adherent surface bacteria, crushed aseptically, serially diluted, and inoculated onto five different culture media. Resulting colony-forming units were isolated for identification and plate-based assays to quantify biofilm formation and antibiotic resistance. Eleven antibiotics were chosen for testing, which included common surgical prophylaxes and colistin, considered an antibiotic of last resort. Results: From five calcium oxalate and five calcium phosphate stones, we obtained 75 bacterial isolates comprised of Kocuria, Escherichia, Micrococcus, Staphylococcus, Bacillus, Actinomyces, Brevibacterium, Rothia, and Dermacoccus genera. Out of 44 isolates tested, 42 exhibited strong biofilm formation, with one each exhibiting moderate or no biofilm formation. The strongest biofilms were from K. rhizophila, Bacillus spp. and M. luteus. Most isolates (38 out of 44) exhibited complete resistance at least one antibiotic. Thirteen isolates exhibited complete resistance to four different antibiotics. A total of 6 of the 11 antibiotics exhibited at least moderate effectiveness against all isolates, which included amoxycillin-clavulanic acid, ciprofloxacin, gentamicin, cefazolin, levofloxacin, and vancomycin. Colistin was the least effective, with only nine of 44 isolates exhibiting susceptibility. Conclusions: Our study presents strong evidence for biofilm formation in stone-associated bacteria and moderate evidence for antibiotic resistance. Unexpectedly, most isolates were resistant to colistin, which suggests that this antibiotic is not effective as a last resort. More work is needed to understand the mechanisms of how biofilm formation promotes lithogenesis. (Figure Presented).

Volume

37

First Page

A24

Last Page

A25

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