AUTHOR=Manoharan Arthika , Farrell Jessica , Aldilla Vina R. , Whiteley Greg , Kriel Erik , Glasbey Trevor , Kumar Naresh , Moore Kate H. , Manos Jim , Das Theerthankar 

TITLE=N-acetylcysteine prevents catheter occlusion and inflammation in catheter associated-urinary tract infections by suppressing urease activity

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=13

YEAR=2023

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2023.1216798

DOI=10.3389/fcimb.2023.1216798

ISSN=2235-2988

ABSTRACT=<sec><title>Introduction</title><p><italic>Proteus mirabilis</italic> is a key pathobiont in catheter-associated urinary tract infections (CA-UTIs), which is well known to form crystalline biofilms that occlude catheters. Urease activity alkylates urine through the release of ammonia, consequentially resulting in higher levels of Mg<sup>2+</sup> and Ca<sup>2+</sup> and formation of crystals. In this study, we showed that <italic>N</italic>-acetyl cysteine (NAC), a thiol antioxidant, is a potent urease inhibitor that prevents crystalline biofilm formation.</p></sec><sec><title>Methods</title><p>To quantify urease activity, Berthelot’s method was done on bacterial extracts treated with NAC. We also used an <italic>in vitro</italic> catheterised glass bladder model to study the effect of NAC treatment on catheter occlusion and biofilm encrustation in <italic>P. mirabilis</italic> infections. Inductively-coupled plasma mass spectrometry (ICP-MS) was performed on catheter samples to decipher elemental profiles.</p></sec><sec><title>Results</title><p>NAC inhibits urease activity of clinical <italic>P. mirabilis</italic> isolates at concentrations as low as 1 mM, independent of bacterial killing. The study also showed that NAC is bacteriostatic on <italic>P. mirabilis</italic>, and inhibited biofilm formation and catheter occlusion in an <italic>in vitro</italic>. A significant 4-8<sub>log10</sub> reduction in viable bacteria was observed in catheters infected in this model. Additionally, biofilms in NAC treated catheters displayed a depletion of calcium, magnesium, or phosphates (&gt;10 fold reduction), thus confirming the absence of any urease activity in the presence of NAC. Interestingly, we also showed that not only is NAC anti-inflammatory in bladder epithelial cells (BECs), but that it mutes its inflammatory response to urease and <italic>P. mirabilis</italic> infection by reducing the production of IL-6, IL-8 and IL-1b.</p></sec><sec><title>Discussion</title><p>Using biochemical, microbiological and immunological techniques, this study displays the functionality of NAC in preventing catheter occlusion by inhibiting urease activity. The study also highlights NAC as a strong anti-inflammatory antibiofilm agent that can target both bacterial and host factors in the treatment of CA-UTIs.</p></sec>