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Immunol Res. 2018 Aug;66(4):503-512. doi: 10.1007/s12026-018-9009-4.

Serodiagnostic evaluation of recombinant CdtB of S. Typhi as a potential candidate for acute typhoid.

Author information

1
Centre for Bio-design & Diagnostics, Translational Health Science and Technology Institute, Faridabad, Haryana, India.
2
Central Research Institute, Kasauli, Himachal Pradesh, India.
3
Department of Experimental Medicine & Biotechnology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
4
Paediatric Biology Centre, Translational Health Science and Technology Institute, Faridabad, Haryana, India.
5
International Centre for Genetic Engineering & Biotechnology, New Delhi, India.
6
Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
7
Regional Centre for Biotechnology, Faridabad, Haryana, India.
8
Centre for Bio-design & Diagnostics, Translational Health Science and Technology Institute, Faridabad, Haryana, India. ashutosht@hotmail.com.
9
Department of Experimental Medicine & Biotechnology, Postgraduate Institute of Medical Education and Research, Chandigarh, India. ashutosht@hotmail.com.

Abstract

Typhoid fever caused by human restricted Salmonella typhi presents a considerable health burden on developing South-Asian nations like India. The suboptimal sensitivity and specificity associated with culture-based isolation of etiological agent and the extensively used surface antigen-based serological assays often lead to misdiagnosis and inappropriate antimicrobial treatment. The increasing reports of the emergence of resistant strains and undefined disease burden signify the critical need for an inexpensive, reliable, easy-to-use, and highly sensitive diagnostic test for typhoid fever. Utilizing S. typhi-specific and immunogenic antigens in sero-diagnostic assays could lead to precise diagnosis of acute typhoid and prompt treatment. In this study, we report cloning, expression, and purification of recombinant Cytolethal distending toxin subunit B (CdtB) of S. typhi, which is reported to be highly specific, immunogenic, and expressed only upon S. typhi infection. We further evaluated the purified recombinant CdtB for its diagnostic potential in an IgM-based indirect ELISA format using 33 human samples. Twenty-one serum samples from blood culture confirmed cases (nā€‰=ā€‰21) of typhoid and 12 samples from healthy controls (nā€‰=ā€‰12) were tested. The assay showed sensitivity of 100% and specificity of 83.3% respectively with positive and negative predictive values of 91.3 and 100% respectively. Efficient detection of specific IgM antibodies indicates that CdtB could be highly valuable in sero-diagnosis of acute typhoid and rapid screening of clinical samples.

KEYWORDS:

CdtB; IgM; S. typhi; Sero-diagnosis; Typhoid diagnostics; Typhoid fever

PMID:
29931558
DOI:
10.1007/s12026-018-9009-4

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