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Effects of antimicrobial photodynamic therapy on antibiotic-resistant Escherichia coli

Garcez, Aguinaldo S. and Kaplan, Mohammed and Jensen, Grant J. and Scheidt, Fábio R. and Oliveira, Eduardo M. and Suzuki, Selly S. (2020) Effects of antimicrobial photodynamic therapy on antibiotic-resistant Escherichia coli. Photodiagnosis and Photodynamic Therapy, 32 . Art. No. 102029. ISSN 1572-1000. PMCID PMC7744317. doi:10.1016/j.pdpdt.2020.102029.

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This study used Electron Cryo-tomography (ECT) and fluorescent images to evaluate antimicrobial photodynamic therapy (aPDT) on the envelope architecture of a Gram-negative bacteria and the effects of combined therapy of aPDT and antibiotics. Standard and clinical suspension of Escherichia coli were submitted to photodynamic treatment with methylene blue solution (100μM) and a 100 mW LED emitting at 660 nm with 3 and 18 J of energy. As a control group, a suspension of E. coli was submitted to penicillin V for 60 min at 30 °C, to compare the damage in cell wall structure. After treatment, ECT images were collected and E. coli biofilms were grown in glass-cover slides and stained with live/dead staining for fluorescence analysis before and after treatments. Bacteria were also submitted to disc diffusion and MIC50 tests with Ampicillin, Amoxicillin + Clavulanic acid, Clindamycin and Erythromycin. For in vivo experiment Galleria mellonella larvae were infected with E. coli and treated with antibiotics, aPDT or combined therapy. ECT images presented damage to cell walls and vesicles structures inside and outside the bacteria and fluorescent images showed dose dependent effect of aPDT. Antibiotic or aPDT alone did not improve the survival of caterpillars, but the combined therapy significantly increased survival curve. ECT and fluorescent images shows that aPDT seems to promote micro-damages to cell envelope and causes the production of membrane vesicles permeabilizing cell membranes. The results showed that pre-treating bacterial cells with a photosensitizer and light make them more susceptible to antibiotics and could be an alternative to local infection treatment by resistant bacteria.

Item Type:Article
Related URLs:
URLURL TypeDescription
Garcez, Aguinaldo S.0000-0003-2037-7211
Kaplan, Mohammed0000-0002-0759-0459
Jensen, Grant J.0000-0003-1556-4864
Additional Information:© 2020 Elsevier B.V. Received 5 May 2020, Revised 16 September 2020, Accepted 18 September 2020, Available online 24 September 2020. This work was supported in part by NIH grant R35 GM122588 (to G.J.J.). M.K. acknowledges a Rubicon postdoctoral fellowship from the Nederlandse Organisatie voor Wetenschappelijk Onderzoek. Cryo-ET work was performed in the Beckman Institute Resource Center for Transmission Electron Microscopy at the California Institute of Technology. Authors’ contribution: Garcez AS and Kaplan M – wrote the paper and participate in the experiments. Oliveira EM, Scheidt F R - participate in the experiments. Suzuki SS and Jensen G – Data interpretation and revision of the text. The authors report no declarations of interest.
Funding AgencyGrant Number
NIHR35 GM122588
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
Subject Keywords:Electron Cryo-tomography; methylene blue; PDT; antibiotics
PubMed Central ID:PMC7744317
Record Number:CaltechAUTHORS:20201005-131934069
Persistent URL:
Official Citation:Aguinaldo S. Garcez, Mohammed Kaplan, Grant J. Jensen, Fábio R. Scheidt, Eduardo M. Oliveira, Selly S. Suzuki, Effects of antimicrobial photodynamic therapy on antibiotic-resistant Escherichia coli, Photodiagnosis and Photodynamic Therapy, Volume 32, 2020, 102029, ISSN 1572-1000, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105806
Deposited By: Tony Diaz
Deposited On:05 Oct 2020 20:42
Last Modified:16 Nov 2021 18:46

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