Antimicrobial and cytotoxic synergism of biocides and quorum-sensing inhibitors against uropathogenic Escherichia coli.

CAPPER-PARKIN, K.L., NICHOL, T., SMITH, T.J., LACEY, M.M. and FORBES, S. (2023). Antimicrobial and cytotoxic synergism of biocides and quorum-sensing inhibitors against uropathogenic Escherichia coli. The Journal of hospital infection, 134, 138-146.

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Uropathogenic Escherichia coli (UPEC) are a primary cause of catheter-associated urinary tract infections (CAUTIs), often forming mature recalcitrant biofilms on the catheter surface. Anti-infective catheter coatings containing single biocides have been developed but display limited antimicrobial activity due to the selection of biocide-resistant bacterial populations. Furthermore, biocides often display cytotoxicity at concentrations required to eradicate biofilms, limiting their antiseptic potential. Quorum-sensing inhibitors (QSIs) provide a novel anti-infective approach to disrupt biofilm formation on the catheter surface and help prevent CAUTIs.


To evaluate the combinatorial impact of biocides and QSIs at bacteriostatic, bactericidal and biofilm eradication concentrations in parallel to assessing cytotoxicity in a bladder smooth muscle (BSM) cell line.


Checkerboard assays were performed to determine fractional inhibitory, bactericidal, and biofilm eradication concentrations of test combinations in UPEC and combined cytotoxic effects in BSM cells.


Synergistic antimicrobial activity was observed between polyhexamethylene biguanide, benzalkonium chloride or silver nitrate in combination with either cinnamaldehyde or furanone-C30 against UPEC biofilms. However, furanone-C30 was cytotoxic at concentrations below those required for even bacteriostatic activity. A dose-dependent cytotoxicity profile was observed for cinnamaldehyde when in combination with BAC, PHMB or silver nitrate. Both PHMB and silver nitrate displayed combined bacteriostatic and bactericidal activity below the half-maximum inhibitory concentration (IC50). Triclosan in combination with both QSIs displayed antagonistic activity in both UPEC and BSM cells.


PHMB and silver in combination with cinnamaldehyde display synergistic antimicrobial activity in UPEC at non-cytotoxic concentrations, suggesting potential as anti-infective catheter-coating agents.

Item Type: Article
Uncontrolled Keywords: Biocides; Catheter-associated urinary tract infections; Combinatorial therapies; Quorum-sensing inhibitors; Urinary tract infections; Uropathogenic Escherichia coli; 1103 Clinical Sciences; 1117 Public Health and Health Services; Epidemiology; 3202 Clinical sciences; 4202 Epidemiology; 4206 Public health
Identification Number:
Page Range: 138-146
SWORD Depositor: Symplectic Elements
Depositing User: Symplectic Elements
Date Deposited: 06 Mar 2023 10:57
Last Modified: 11 Oct 2023 16:31

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