Journal Article

<i>Staphylococcus aureus</i> small colony variants are resistant to the antimicrobial peptide lactoferricin B

Ørjan Samuelsen, Hanne Husom Haukland, Barbara C. Kahl, Christof von Eiff, Richard A. Proctor, Hilde Ulvatne, Kjersti Sandvik and Lars H. Vorland

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 56, issue 6, pages 1126-1129
Published in print December 2005 | ISSN: 0305-7453
Published online December 2005 | e-ISSN: 1460-2091 | DOI: http://dx.doi.org/10.1093/jac/dki385
Staphylococcus aureus small colony variants are resistant to the antimicrobial peptide lactoferricin B

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  • Medical Oncology
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Objectives: To determine whether Staphylococcus aureus small colony variants (SCVs) are resistant to the antimicrobial peptide lactoferricin B. To assess if deficiency in transmembrane potential, a common characteristic of SCVs that are haemin- or menadione-auxotrophs, affects the uptake of the peptide into the bacterial cytoplasm.

Methods: A broth microdilution technique was used for susceptibility testing to determine the MIC of lactoferricin B for SCVs with three different auxotrophisms (haemin, menadione or thymidine) and their isogenic parent strains. Both clinical isolates and genetically defined mutants were used. The internalization of lactoferricin B in a hemB mutant and the respective parent strain was studied using transmission electron microscopy and immunogold labelling.

Results: All SCVs showed reduced susceptibility to lactoferricin B irrespective of their auxotrophy compared with their isogenic parent strains. The MIC for all SCVs was >256 mg/L, whereas the MICs for the parent strains ranged from 16–256 mg/L. Surprisingly, the hemB mutant contained significantly more lactoferricin B intracellularly than the respective parent strain.

Conclusions: The resistance mechanism of SCVs towards the antimicrobial peptide lactoferricin B is presumably caused by the metabolic changes present in SCVs rather than by a changed transmembrane potential of SCVs or reduced uptake of the peptide.

Keywords: cellular uptake; electron microscopy; immunolabelling; transmembrane potential; metabolic resistance; antimicrobial resistance; resistance mechanism

Journal Article.  1874 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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