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

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

doi:10.3389/fcimb.2023.1216798

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

Front Cell Infect Microbiol. 2023 Oct 26:13:1216798. doi: 10.3389/fcimb.2023.1216798. eCollection 2023.

Authors

Arthika Manoharan^{1

2}, Jessica Farrell^{1

3}, Vina R Aldilla⁴, Greg Whiteley^{1

3

5}, Erik Kriel³, Trevor Glasbey³, Naresh Kumar⁴, Kate H Moore⁶, Jim Manos^{1

2}, Theerthankar Das^{1

2}

Affiliations

¹ Infection, Immunity and Inflammation Theme, School of Medical Sciences, Charles Perkins Centre, The University of Sydney, Sydney, NSW, Australia.
² Sydney Institute of Infectious Disease, The University of Sydney, Sydney, NSW, Australia.
³ Whiteley Corporation, Tomago, NSW, Australia.
⁴ School of Chemistry, The University of New South Wales, Sydney, NSW, Australia.
⁵ School of Medicine, Western Sydney University, NSW, Australia.
⁶ Department of Urogynaecology, St George Hospital, University of New South Wales, Sydney, NSW, Australia.

Abstract

Introduction: Proteus mirabilis 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 Mg²⁺ and Ca²⁺ and formation of crystals. In this study, we showed that N-acetyl cysteine (NAC), a thiol antioxidant, is a potent urease inhibitor that prevents crystalline biofilm formation.

Methods: To quantify urease activity, Berthelot's method was done on bacterial extracts treated with NAC. We also used an in vitro catheterised glass bladder model to study the effect of NAC treatment on catheter occlusion and biofilm encrustation in P. mirabilis infections. Inductively-coupled plasma mass spectrometry (ICP-MS) was performed on catheter samples to decipher elemental profiles.

Results: NAC inhibits urease activity of clinical P. mirabilis isolates at concentrations as low as 1 mM, independent of bacterial killing. The study also showed that NAC is bacteriostatic on P. mirabilis, and inhibited biofilm formation and catheter occlusion in an in vitro. A significant 4-8_log10 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 (>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 P. mirabilis infection by reducing the production of IL-6, IL-8 and IL-1b.

Discussion: 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.

Keywords: N-acetyl cysteine (NAC); Proteus mirabilis; UTI; biofilms; catheter-associated urinary tract infections (CA-UTI); urease.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Acetylcysteine / pharmacology
Anti-Inflammatory Agents / pharmacology
Biofilms
Catheters
Humans
Inflammation / prevention & control
Proteus Infections* / drug therapy
Proteus Infections* / microbiology
Proteus Infections* / prevention & control
Proteus mirabilis
Urease
Urinary Catheterization
Urinary Tract Infections* / microbiology
Urinary Tract Infections* / prevention & control

Substances

Acetylcysteine
Urease
Anti-Inflammatory Agents

Grants and funding

This research was conducted under a research grant through the Innovative Manufacturing Cooperative Research Centre (IMCRC), a body constituted under the Commonwealth of Australia. This research grant was co-jointly funded by Whiteley Corporation. Whiteley Corporation has no direct financial or indirect financial gain through these research findings or this publication, which was all conducted under the reviews outlined in the Grant from the IMCRC (IMCRC/WLY/08052019.1). The funder was not involved in the study design, collection, analysis, data interpretation and writing of the article.