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Formation of Pseudomonas aeruginosa inhibition zone during tobramycin disk diffusion is due to transition from planktonic to biofilm mode of growth

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@article{894755d17a4a42fe8b775c2b2b78c9ca,
title = "Formation of Pseudomonas aeruginosa inhibition zone during tobramycin disk diffusion is due to transition from planktonic to biofilm mode of growth",
abstract = "Pseudomonas aeruginosa PAO1 (tobramycin MIC = 0.064 µg/mL) was used to perform agar diffusion tests employing tobramycin-containing tablets. Bacterial growth and formation of inhibition zones were studied by stereomicroscopy and by blotting with microscope slides and staining with methylene blue, Alcian blue and a fluorescent lectin for the P. aeruginosa PSL, which was studied by confocal laser scanning microscopy. Diffusion of tobramycin from the deposit was modelled using a 3D geometric version of Fick's second law of diffusion. The time-dependent gradual increase in the minimum biofilm eradication concentration (MBEC) was studied using a Calgary Biofilm Device. The early inhibition zone was visible after 5 h of incubation. The corresponding calculated tobramycin concentration at the border was 1.9 µg/mL, which increased to 3.2 µg/mL and 6.3 µg/mL after 7 h and 24 h, respectively. The inhibition zone increased to the stable final zone after 7 h of incubation. Bacterial growth and small aggregate formation (young biofilms) took place inside the inhibition zone until the small aggregates contained less than ca. 64 cells and production of polysaccharide matrix including PSL had begun; thereafter, the small bacterial aggregates were killed by tobramycin. Bacteria at the border of the stable inhibition zone and beyond continued to grow to a mature biofilm and produced large amount of polysaccharide-containing matrix. Formation of the inhibition zone during agar diffusion antimicrobial susceptibility testing is due to a switch from a planktonic to biofilm mode of growth and gives clinically important information about the increased antimicrobial tolerance of biofilms.",
keywords = "Anti-Bacterial Agents/pharmacology, Biofilms/growth & development, Disk Diffusion Antimicrobial Tests, Microscopy, Microscopy, Confocal, Pseudomonas aeruginosa/drug effects, Staining and Labeling, Time Factors, Tobramycin/pharmacology",
author = "Niels H{\o}iby and Kaj-{\AA}ge Henneberg and Hengshuang Wang and Camilla Stavnsbjerg and Thomas Bjarnsholt and Oana Ciofu and Johansen, {Ulla Rydal} and Thomas Sams",
note = "Copyright {\textcopyright} 2019 The Authors. Published by Elsevier B.V. All rights reserved.",
year = "2019",
month = may,
doi = "10.1016/j.ijantimicag.2018.12.015",
language = "English",
volume = "53",
pages = "564--573",
journal = "International Journal of Antimicrobial Agents",
issn = "0924-8579",
publisher = "Elsevier BV",
number = "5",

}

RIS

TY - JOUR

T1 - Formation of Pseudomonas aeruginosa inhibition zone during tobramycin disk diffusion is due to transition from planktonic to biofilm mode of growth

AU - Høiby, Niels

AU - Henneberg, Kaj-Åge

AU - Wang, Hengshuang

AU - Stavnsbjerg, Camilla

AU - Bjarnsholt, Thomas

AU - Ciofu, Oana

AU - Johansen, Ulla Rydal

AU - Sams, Thomas

N1 - Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.

PY - 2019/5

Y1 - 2019/5

N2 - Pseudomonas aeruginosa PAO1 (tobramycin MIC = 0.064 µg/mL) was used to perform agar diffusion tests employing tobramycin-containing tablets. Bacterial growth and formation of inhibition zones were studied by stereomicroscopy and by blotting with microscope slides and staining with methylene blue, Alcian blue and a fluorescent lectin for the P. aeruginosa PSL, which was studied by confocal laser scanning microscopy. Diffusion of tobramycin from the deposit was modelled using a 3D geometric version of Fick's second law of diffusion. The time-dependent gradual increase in the minimum biofilm eradication concentration (MBEC) was studied using a Calgary Biofilm Device. The early inhibition zone was visible after 5 h of incubation. The corresponding calculated tobramycin concentration at the border was 1.9 µg/mL, which increased to 3.2 µg/mL and 6.3 µg/mL after 7 h and 24 h, respectively. The inhibition zone increased to the stable final zone after 7 h of incubation. Bacterial growth and small aggregate formation (young biofilms) took place inside the inhibition zone until the small aggregates contained less than ca. 64 cells and production of polysaccharide matrix including PSL had begun; thereafter, the small bacterial aggregates were killed by tobramycin. Bacteria at the border of the stable inhibition zone and beyond continued to grow to a mature biofilm and produced large amount of polysaccharide-containing matrix. Formation of the inhibition zone during agar diffusion antimicrobial susceptibility testing is due to a switch from a planktonic to biofilm mode of growth and gives clinically important information about the increased antimicrobial tolerance of biofilms.

AB - Pseudomonas aeruginosa PAO1 (tobramycin MIC = 0.064 µg/mL) was used to perform agar diffusion tests employing tobramycin-containing tablets. Bacterial growth and formation of inhibition zones were studied by stereomicroscopy and by blotting with microscope slides and staining with methylene blue, Alcian blue and a fluorescent lectin for the P. aeruginosa PSL, which was studied by confocal laser scanning microscopy. Diffusion of tobramycin from the deposit was modelled using a 3D geometric version of Fick's second law of diffusion. The time-dependent gradual increase in the minimum biofilm eradication concentration (MBEC) was studied using a Calgary Biofilm Device. The early inhibition zone was visible after 5 h of incubation. The corresponding calculated tobramycin concentration at the border was 1.9 µg/mL, which increased to 3.2 µg/mL and 6.3 µg/mL after 7 h and 24 h, respectively. The inhibition zone increased to the stable final zone after 7 h of incubation. Bacterial growth and small aggregate formation (young biofilms) took place inside the inhibition zone until the small aggregates contained less than ca. 64 cells and production of polysaccharide matrix including PSL had begun; thereafter, the small bacterial aggregates were killed by tobramycin. Bacteria at the border of the stable inhibition zone and beyond continued to grow to a mature biofilm and produced large amount of polysaccharide-containing matrix. Formation of the inhibition zone during agar diffusion antimicrobial susceptibility testing is due to a switch from a planktonic to biofilm mode of growth and gives clinically important information about the increased antimicrobial tolerance of biofilms.

KW - Anti-Bacterial Agents/pharmacology

KW - Biofilms/growth & development

KW - Disk Diffusion Antimicrobial Tests

KW - Microscopy

KW - Microscopy, Confocal

KW - Pseudomonas aeruginosa/drug effects

KW - Staining and Labeling

KW - Time Factors

KW - Tobramycin/pharmacology

U2 - 10.1016/j.ijantimicag.2018.12.015

DO - 10.1016/j.ijantimicag.2018.12.015

M3 - Journal article

C2 - 30615928

VL - 53

SP - 564

EP - 573

JO - International Journal of Antimicrobial Agents

JF - International Journal of Antimicrobial Agents

SN - 0924-8579

IS - 5

ER -

ID: 58995281