AUA 2023: Antimicrobial and Antibiofilm Properties of Chitosan: An Ex-Vivo Study on Kidney Stones

(UroToday.com) At the 2023 American Urological Association (AUA) Annual Meeting, a poster session on Stone Disease: Basic Science Research & Physiology included a presentation by Grace Holton covering Antimicrobial and Antibiofilm Properties of Chitosan. Grace Holton described how prior research has shown that up to 40 % of the kidney stone surface are a habitat of microbes’ biofilms. During stone removal procedures such as ureteroscopy (URS) laser lithotripsy or percutaneous nephrolithotomy (PCNL), stones are fragmented which may lead to the dispersion of these surface microbes’ colonies into the urinary tract, and increase the risk of post operative surgical infection, urosepsis, and stone recurrence rate. The team led by Grace Holton at the Department of Urology in Stanford School of Medicine hypothesized that the inclusion of Chitosan, a chemical agent renowned for its ability to minimize microbiome and biofilm formation, could potentially eliminate uropathogens and bacterial biofilms commonly linked to kidney stones.

After obtaining appropriate IRB approval of the study and with the consent of included patients, patients undergoing URS and PCNL stone treatment were prospectively consented in an ethical manner, and pre-operative urine and intra-operative stone fragments were collected (n=57). In vitro biofilm and bacteria were assessed and quantified using scanning electron microscopy. Common uropathogens found on collected Kidney stones were cultured on an agar plate, and optical density was utilized to measure the bactericidal effects of chitosan. Study arms were divided into two groups: stones treated with normal saline for 90 minutes and an experimental group with Chitosan solution in saline.

Figure 1 Chitosan chemical Structure

The team discovered, through studying the in vitro culture, that even an incredibly low concentration (0.0001%) of the agent chitosan was able to inhibit the growth of certain microbes including E Coli., Proteus Mirabilis, Klebsiella Pneumoniae, and Staph Aureus. These particular pathogens are of interest because they are microbes typically found in the urine of recurrent nephrolithiasis patients.

Figure 2 Chitosan % (w/v) effect on Viable cells CFU/g stone

Figure 3 Scanning electron microscope image of an E. coli biofilm on a calcium oxalate stone before and after 90 minutes of Chitosan exposure

Grace concluded her presentation by exclaiming that the agent chitosan has the potential to inhibit the growth of multiple gram negative and gram-positive pathogens, identified through in vitro studies. At the end of the talk, she was asked by an audience member if there is any role for chitosan to be applied to urological devices such as stents or catheters, and Grace noted that studies incorporating chitosan into indwelling stents through a surrounding coating are currently underway. Finally, another member inquired if chitosan is currently used for any other medical applications outside the realm of urology and Grace exclaimed that it is FDA approved for wound healing and is sometimes used to aid in hemostatic therapies.