Phototoxicity of phenothiazinium dyes against methicillin-resistant Staphylococcus aureus and multi-drug resistant Escherichia coli.

Abstract

BACKGROUND:

Photodynamic inactivation (PDI) has been investigated to cope with the increasing incidence of multidrug-resistant (MDR) pathogens. Here we studied the PDI mediated by methylene blue (MB) and toluidine blue O (TBO) in clinical methicillin-resistant Staphylococcus aureus and MDR Escherichia coli, together with their corresponding American Type Culture Collection (ATCC) strains.

METHODS:

Effect of photosensitizer concentration (12.5, 25, 50 μg/ml) and laser irradiation time (10, 20 and 30 min) on lethal photosensitization was investigated.

RESULTS:

TBO was more effective. TBO at 50 μg/ml, 46.8 J cm⁻², exhibited 0.7 log killing for MDR E. coli and 1.7 log killing for E. coli (ATCC 25922); 3.1 log killing for MRSA, and 4.2 log killing for S. aureus (ATCC 25923). MB at 50 μg/ml, 163.8 J cm⁻², only exhibited 2.2 log killing in MRSA and 3.1 log killing in S. aureus (ATCC 25923). MB (50 μg/ml, 163.8 J cm⁻²) induced 0.2 log killing for MDR E. coli and 0.3 log killing for E. coli (ATCC 25922). After TBO-PDI, MDR isolates were more susceptible to some antibiotics than control groups.

CONCLUSION:

Our studied clinical isolates were more resistant to PDI-mediated killing than their ATCC reference strains. Thus, TBO/MB-mediated PDI in other MDR isolates deserves further investigation.

• Authors: Nasim Kashef, Gita Ravaei Sharif Abadi, Gholamreza Esmaeeli Djavid
• Journal: Photodiagnosis and photodynamic therapy (Photodiagnosis Photodyn Ther) Vol. 9 Issue 1 Pg. 11-5 (Mar 2012) ISSN: 1873-1597 [Electronic] Netherlands
• PMID: 22369724 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2011 Elsevier B.V. All rights reserved.

Chemical References

• Anti-Bacterial Agents
• Coloring Agents
• Photosensitizing Agents
• Tolonium Chloride
• Methylene Blue

Topics

• Anti-Bacterial Agents (administration & dosage, pharmacology)
• Bacteriological Techniques
• Coloring Agents (administration & dosage, pharmacology)
• Drug Resistance, Multiple, Bacterial (drug effects)
• Escherichia coli (drug effects)
• Humans
• Methicillin-Resistant Staphylococcus aureus (drug effects)
• Methylene Blue (administration & dosage, pharmacology)
• Photochemotherapy (methods)
• Photosensitizing Agents (administration & dosage, pharmacology)
• Tolonium Chloride (administration & dosage, pharmacology)