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Rapid identification of capsulated Acinetobacter baumannii using a density-dependent gradient test

BACKGROUND: Gram-negative bacterial capsules are associated with production of carbohydrates, frequently resulting in a mucoid phenotype. Infections caused by capsulated or mucoid A. baumannii are associated with increased clinical severity. Therefore, it is clinically and epidemiologically importan...

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Autores principales: Kon, Hadas, Schwartz, David, Temkin, Elizabeth, Carmeli, Yehuda, Lellouche, Jonathan
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7493399/
https://www.ncbi.nlm.nih.gov/pubmed/32938408
http://dx.doi.org/10.1186/s12866-020-01971-9
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author Kon, Hadas
Schwartz, David
Temkin, Elizabeth
Carmeli, Yehuda
Lellouche, Jonathan
author_facet Kon, Hadas
Schwartz, David
Temkin, Elizabeth
Carmeli, Yehuda
Lellouche, Jonathan
author_sort Kon, Hadas
collection PubMed
description BACKGROUND: Gram-negative bacterial capsules are associated with production of carbohydrates, frequently resulting in a mucoid phenotype. Infections caused by capsulated or mucoid A. baumannii are associated with increased clinical severity. Therefore, it is clinically and epidemiologically important to identify capsulated A. baumannii. Here, we describe a density-dependent gradient test to distinguish between capsulated and thin/non-capsulated A. baumannii. RESULTS: Thirty-one of 57 A. baumannii isolates displayed a mucoid phenotype. The density-dependent gradient test was comprised of two phases, with silica concentrations of 30% (top phase) and 50% (bottom phase). Twenty-three isolates migrated to the bottom phase, indicating thin or non-capsulated strains, and 34 migrated to the top phase, suggesting strains suspected to be capsulated. There was agreement between the mucoid and the non-mucoid phenotypes and the density-dependent gradient test for all but three isolates. Total carbohydrates extracted from strains suspected to be capsulated were significantly higher. Transmission electron microscopy confirmed the presence of a capsule in the six representative strains suspected to be capsulated. CONCLUSIONS: The density-dependent gradient test can be used to verify capsule presence in mucoid-appearing A. baumannii strains. Identifying capsulated strains can be useful for directing infection control measures to reduce the spread of hypervirulent strains.
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spelling pubmed-74933992020-09-16 Rapid identification of capsulated Acinetobacter baumannii using a density-dependent gradient test Kon, Hadas Schwartz, David Temkin, Elizabeth Carmeli, Yehuda Lellouche, Jonathan BMC Microbiol Methodology Article BACKGROUND: Gram-negative bacterial capsules are associated with production of carbohydrates, frequently resulting in a mucoid phenotype. Infections caused by capsulated or mucoid A. baumannii are associated with increased clinical severity. Therefore, it is clinically and epidemiologically important to identify capsulated A. baumannii. Here, we describe a density-dependent gradient test to distinguish between capsulated and thin/non-capsulated A. baumannii. RESULTS: Thirty-one of 57 A. baumannii isolates displayed a mucoid phenotype. The density-dependent gradient test was comprised of two phases, with silica concentrations of 30% (top phase) and 50% (bottom phase). Twenty-three isolates migrated to the bottom phase, indicating thin or non-capsulated strains, and 34 migrated to the top phase, suggesting strains suspected to be capsulated. There was agreement between the mucoid and the non-mucoid phenotypes and the density-dependent gradient test for all but three isolates. Total carbohydrates extracted from strains suspected to be capsulated were significantly higher. Transmission electron microscopy confirmed the presence of a capsule in the six representative strains suspected to be capsulated. CONCLUSIONS: The density-dependent gradient test can be used to verify capsule presence in mucoid-appearing A. baumannii strains. Identifying capsulated strains can be useful for directing infection control measures to reduce the spread of hypervirulent strains. BioMed Central 2020-09-16 /pmc/articles/PMC7493399/ /pubmed/32938408 http://dx.doi.org/10.1186/s12866-020-01971-9 Text en © The Author(s) 2020 Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
spellingShingle Methodology Article
Kon, Hadas
Schwartz, David
Temkin, Elizabeth
Carmeli, Yehuda
Lellouche, Jonathan
Rapid identification of capsulated Acinetobacter baumannii using a density-dependent gradient test
title Rapid identification of capsulated Acinetobacter baumannii using a density-dependent gradient test
title_full Rapid identification of capsulated Acinetobacter baumannii using a density-dependent gradient test
title_fullStr Rapid identification of capsulated Acinetobacter baumannii using a density-dependent gradient test
title_full_unstemmed Rapid identification of capsulated Acinetobacter baumannii using a density-dependent gradient test
title_short Rapid identification of capsulated Acinetobacter baumannii using a density-dependent gradient test
title_sort rapid identification of capsulated acinetobacter baumannii using a density-dependent gradient test
topic Methodology Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7493399/
https://www.ncbi.nlm.nih.gov/pubmed/32938408
http://dx.doi.org/10.1186/s12866-020-01971-9
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