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Photodiagnosis Photodyn Ther. 2013 Dec;10(4):664-71. doi: 10.1016/j.pdpdt.2013.07.003. Epub 2013 Aug 9.

Repetitive methylene blue-mediated photoantimicrobial chemotherapy changes the susceptibility and expression of the outer membrane proteins of Pseudomonas aeruginosa.

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  • 1Department of Ophthalmology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan, ROC.

Abstract

BACKGROUND:

Since bacterial multidrug efflux pumps mediate intracellular photosensitizer methylene blue, a change in the expression alters the susceptibility to photoantimicrobial chemotherapy (PACT) of Pseudomonas aeruginosa, which may occur following repetitive sublethal challenges.

MATERIALS AND METHODS:

We performed 10 consecutive, methylene blue-mediated PACT on one antibiotic-sensitive strain and three antibiotic-resistant strains of P. aeruginosa. Following each therapy, the surviving bacteria were collected for subsequent PACT. The susceptibility was compared for the pre- and the post-treated strains following repetitive PACT. To explore the existence of efflux pumps, one of the inhibitors, namely Phe-Arg β-naphthylamide dihydrochloride (PAβN 25 μg/ml), was added. Profiles of outer membrane proteins were obtained for the pre-treated and the post-treated strains.

RESULTS:

The susceptibility of PACT did not correlate with the antibiotic sensitivity. Following ten PACT, there was no significant change in susceptibility for three tested strains, except for one antibiotic-resistant strain, for which the 10th generation became less susceptible than the original one. With 2-D electrophoresis, a change in the expression of outer membrane proteins was observed. PAβN successfully increased the phototoxicity in all tested strains, especially the less PACT-susceptible 10th generation of the antibiotic-resistant strain.

CONCLUSIONS:

Following repetitive challenges, PACT had a consistent antimicrobial effect on three strains; however, one antibiotic-resistant strain, which was the most vulnerable to PACT, became more resistant after consecutive challenges. In addition, the post-PACT strain had different expression of outer membrane proteins, providing further evidence view that repetitive PACT with methylene blue could change the expression of efflux pumps.

Copyright © 2013 Elsevier B.V. All rights reserved.

KEYWORDS:

CFU; Efflux pump; MB; MEP; Methylene blue; OMP; Outer membrane protein; PACT; PAβN; Phe-Arg β-naphthylamide dihydrochloride; Phenothiazinium; Photoantimicrobial chemotherapy; Pseudomonas aeruginosa; colony-forming unit; methylene blue; multidrug efflux pump; outer membrane protein; photoantimicrobial chemotherapy

PMID:
24284125
[PubMed - indexed for MEDLINE]
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