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Accuracies of Leuconostoc phenotypic identification: a comparison of API systems and conventional phenotypic assays

BACKGROUND: Commercial diagnostics are commonly used to identify gram-positive bacteria. Errors have been reported mostly at the species level. We have found certain phenotypic criteria used in API systems which significantly misidentify Leuconostoc, an emerging human pathogen, at the genus level. W...

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Autores principales: Kulwichit, Wanla, Nilgate, Sumanee, Chatsuwan, Tanittha, Krajiw, Sunisa, Unhasuta, Chudaachhara, Chongthaleong, Anan
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2007
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1947989/
https://www.ncbi.nlm.nih.gov/pubmed/17605772
http://dx.doi.org/10.1186/1471-2334-7-69
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author Kulwichit, Wanla
Nilgate, Sumanee
Chatsuwan, Tanittha
Krajiw, Sunisa
Unhasuta, Chudaachhara
Chongthaleong, Anan
author_facet Kulwichit, Wanla
Nilgate, Sumanee
Chatsuwan, Tanittha
Krajiw, Sunisa
Unhasuta, Chudaachhara
Chongthaleong, Anan
author_sort Kulwichit, Wanla
collection PubMed
description BACKGROUND: Commercial diagnostics are commonly used to identify gram-positive bacteria. Errors have been reported mostly at the species level. We have found certain phenotypic criteria used in API systems which significantly misidentify Leuconostoc, an emerging human pathogen, at the genus level. We also attempt to find practical, conventional phenotypic assays for accurate identification of this group of bacteria. METHODS: Clinical isolates of catalase-negative, gram-positive coccoid or coccobacillary bacteria with non-β hemolysis in our institute during 1997–2004 were subject to an identification aid by API 20 STREP, following the instruction manual, as an aid to conventional phenotypic tests. Those identified as Leuconostoc by API 20 STREP were re-examined by the same kit and also by API 50 CHL according to the instruction manuals, by our Leuconostoc conventional phenotypic assays, by Leuconostoc- and Lactobacillus-specific PCR's, and, where possible, by 16S rDNA sequence analysis. In addition, catalase-negative gram-positive isolates during 2005–2006 which were resistant to vancomycin at high levels were also evaluated by the same phenotypic and genotypic assays. RESULTS: Out of several thousands of clinical gram-positive isolates, 26 catalase negative gram-positive isolates initially identified as Leuconostoc by API 20 STREP and 7 vancomycin-resistant gram-positive catalase-negative bacteria entered the study. 11 out of the 26 isolates and all the 7 isolates were identified as Leuconostoc by API 20 STREP. Only 5 isolates, however, were confirmed by both genotypic and all defined conventional phenotypic criteria. API 50 CHL also failed to reliably provide accurate identification of Leuconostoc. We have identified key problem tests in API 20 STREP leading to misidentification of the bacteria. A simple, conventional set of phenotypic tests for Leuconostoc identification is proposed. CONCLUSION: The current API systems cannot accurately identify Leuconostoc. Identification of vancomycin-resistant, catalase-negative gram-positive bacteria should be performed by a few practical phenotypic assays, with assistance of genotypic assays where available.
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spelling pubmed-19479892007-08-14 Accuracies of Leuconostoc phenotypic identification: a comparison of API systems and conventional phenotypic assays Kulwichit, Wanla Nilgate, Sumanee Chatsuwan, Tanittha Krajiw, Sunisa Unhasuta, Chudaachhara Chongthaleong, Anan BMC Infect Dis Research Article BACKGROUND: Commercial diagnostics are commonly used to identify gram-positive bacteria. Errors have been reported mostly at the species level. We have found certain phenotypic criteria used in API systems which significantly misidentify Leuconostoc, an emerging human pathogen, at the genus level. We also attempt to find practical, conventional phenotypic assays for accurate identification of this group of bacteria. METHODS: Clinical isolates of catalase-negative, gram-positive coccoid or coccobacillary bacteria with non-β hemolysis in our institute during 1997–2004 were subject to an identification aid by API 20 STREP, following the instruction manual, as an aid to conventional phenotypic tests. Those identified as Leuconostoc by API 20 STREP were re-examined by the same kit and also by API 50 CHL according to the instruction manuals, by our Leuconostoc conventional phenotypic assays, by Leuconostoc- and Lactobacillus-specific PCR's, and, where possible, by 16S rDNA sequence analysis. In addition, catalase-negative gram-positive isolates during 2005–2006 which were resistant to vancomycin at high levels were also evaluated by the same phenotypic and genotypic assays. RESULTS: Out of several thousands of clinical gram-positive isolates, 26 catalase negative gram-positive isolates initially identified as Leuconostoc by API 20 STREP and 7 vancomycin-resistant gram-positive catalase-negative bacteria entered the study. 11 out of the 26 isolates and all the 7 isolates were identified as Leuconostoc by API 20 STREP. Only 5 isolates, however, were confirmed by both genotypic and all defined conventional phenotypic criteria. API 50 CHL also failed to reliably provide accurate identification of Leuconostoc. We have identified key problem tests in API 20 STREP leading to misidentification of the bacteria. A simple, conventional set of phenotypic tests for Leuconostoc identification is proposed. CONCLUSION: The current API systems cannot accurately identify Leuconostoc. Identification of vancomycin-resistant, catalase-negative gram-positive bacteria should be performed by a few practical phenotypic assays, with assistance of genotypic assays where available. BioMed Central 2007-07-02 /pmc/articles/PMC1947989/ /pubmed/17605772 http://dx.doi.org/10.1186/1471-2334-7-69 Text en Copyright © 2007 Kulwichit et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Kulwichit, Wanla
Nilgate, Sumanee
Chatsuwan, Tanittha
Krajiw, Sunisa
Unhasuta, Chudaachhara
Chongthaleong, Anan
Accuracies of Leuconostoc phenotypic identification: a comparison of API systems and conventional phenotypic assays
title Accuracies of Leuconostoc phenotypic identification: a comparison of API systems and conventional phenotypic assays
title_full Accuracies of Leuconostoc phenotypic identification: a comparison of API systems and conventional phenotypic assays
title_fullStr Accuracies of Leuconostoc phenotypic identification: a comparison of API systems and conventional phenotypic assays
title_full_unstemmed Accuracies of Leuconostoc phenotypic identification: a comparison of API systems and conventional phenotypic assays
title_short Accuracies of Leuconostoc phenotypic identification: a comparison of API systems and conventional phenotypic assays
title_sort accuracies of leuconostoc phenotypic identification: a comparison of api systems and conventional phenotypic assays
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1947989/
https://www.ncbi.nlm.nih.gov/pubmed/17605772
http://dx.doi.org/10.1186/1471-2334-7-69
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