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Open Access Research article

OmpU as a biomarker for rapid discrimination between toxigenic and epidemic Vibrio cholerae O1/O139 and non-epidemic Vibrio cholerae in a modified MALDI-TOF MS assay

Armand Paauw1*, Hein Trip1, Marcin Niemcewicz2, Ricela Sellek34, Jonathan ME Heng1, Roos H Mars-Groenendijk1, Ad L de Jong1, Joanna A Majchrzykiewicz-Koehorst1, Jaran S Olsen5 and Evgeni Tsivtsivadze1

Author Affiliations

1 Department of CBRN Protection, TNO, P.O. Box 45, Rijswijk 2280 AA, The Netherlands

2 Military Institute of Hygiene and Epidemiology, 24-100 Pulawy, Lubelska 2, Poland

3 Instituto Tecnológico La Marañosa, Spanish Ministry of Defence, San Martín de la Vega, Madrid, Spain

4 Radiological Environmental Recovery Program, Department of Environment, Centro de Investigaciones Energ eticas, Medioambientales y Tecnologicas (CIEMAT, Madrid, Spain

5 Norwegian Defence Research Establishment, P. O. Box 25, Kjeller N-2027, Norway

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BMC Microbiology 2014, 14:158  doi:10.1186/1471-2180-14-158

Published: 18 June 2014

Abstract

Background

Cholera is an acute diarrheal disease caused by Vibrio cholerae. Outbreaks are caused by a genetically homogenous group of strains from serogroup O1 or O139 that are able to produce the cholera toxin. Rapid detection and identification of these epidemic strains is essential for an effective response to cholera outbreaks.

Results

The use of ferulic acid as a matrix in a new MALDI-TOF MS assay increased the measurable mass range of existing MALDI-TOF MS protocols for bacterial identification. The assay enabled rapid discrimination between epidemic V. cholerae O1/O139 strains and other less pathogenic V. cholerae strains. OmpU, an outer membrane protein whose amino acid sequence is highly conserved among epidemic strains of V. cholerae, appeared as a discriminatory marker in the novel MALDI-TOF MS assay.

Conclusions

The extended mass range of MALDI-TOF MS measurements obtained by using ferulic acid improved the screening for biomarkers in complex protein mixtures. Differences in the mass of abundant homologous proteins due to variation in amino acid sequences can rapidly be examined in multiple samples. Here, a rapid MALDI-TOF MS assay was developed that could discriminate between epidemic O1/O139 strains and other less pathogenic V. cholerae strains based on differences in mass of the OmpU protein. It appeared that the amino acid sequence of OmpU from epidemic V. cholerae O1/O139 strains is unique and highly conserved.