2. Academic Validation
  3. Restoring Colistin Sensitivity and Combating Biofilm Formation: Synergistic Effects of Colistin and Usnic Acid against Colistin-Resistant Enterobacteriaceae

Restoring Colistin Sensitivity and Combating Biofilm Formation: Synergistic Effects of Colistin and Usnic Acid against Colistin-Resistant Enterobacteriaceae

  • ACS Infect Dis. 2023 Nov 9. doi: 10.1021/acsinfecdis.3c00315.
Yi Zhang 1 2,  Yijia Han 2,  Zeyu Huang 1,  Yali Huang 1,  Jingchun Kong 2,  Yao Sun 1,  Jianming Cao 2,  Tieli Zhou 1
Affiliations

Affiliations

  • 1 Department of Clinical Laboratory, The First Affiliated Hospital of Wenzhou Medical University; Key Laboratory of Clinical Laboratory Diagnosis and Translational Research of Zhejiang Province, Wenzhou, Zhejiang Province 325000, China.
  • 2 Department of Medical Lab Science, School of Laboratory Medicine and Life Science, Wenzhou Medical University, Wenzhou, Zhejiang Province 32500, China.
PMID: 37944020 DOI: 10.1021/acsinfecdis.3c00315
Abstract

Colistin (COL), the last line of defense in clinical medicine, is an important therapeutic option against multidrug-resistant Gram-negative bacteria. In this context, the emergence of colistin-resistant (COL-R) bacteria mediated by broad-spectrum efflux pumps, mobile genetic elements, and biofilm formation poses a significant public health concern. In response to this challenge, a novel approach of combining COL with usnic acid (UA) has been proposed in this study. UA is a secondary metabolite derived from lichens and is well-known for its anti-inflammatory properties. This study aimed to investigate the synergistic effects of UA and COL against COL-R Enterobacteriaceae both in vitro and in vivo. The exceptional synergistic Antibacterial activity exhibited by the combination of COL and UA was demonstrated by performing a comprehensive set of assays, including the checkerboard assay, time-dependent killing assay, and Live/Dead Bacterial cell viability assay. Furthermore, crystal violet staining and scanning electron microscopy assays revealed the inhibitory effect of this combination on the biofilm formation. Mechanistically, the combination of UA and COL exacerbated cell membrane rupture, induced DNA damage, and generated a significant amount of Reactive Oxygen Species, which ultimately resulted in Bacterial cell death. In addition, erythrocyte hemolysis and cell viability tests confirmed the biocompatibility of the combination. The evaluation of the COL/UA combination in vivo using Galleria mellonella larvae and a mouse Infection model showed a significant improvement in the survival rate of the infected larvae as well as a reduction in the Bacterial load in the mouse thigh muscle. These findings, for the first time, provide strong evidence for the potential application of COL/UA as an effective alternative therapeutic option to combat infections caused by COL-R Enterobacteriaceae strains.

Keywords

Enterobacteriaceae; antibacterial; antibiofilm; colistin-resistance; synergistic effect; usnic acid.

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