Evaluation of a new serological test for the detection of anti-Coxiella and anti-Rickettsia antibodies

Alain Bizzini; Olivier Péter; David Baud; Sophie Edouard; Pascal Meylan; Gilbert Greub

doi:10.1016/j.micinf.2015.09.015

Evaluation of a new serological test for the detection of anti-Coxiella and anti-Rickettsia antibodies

Microbes Infect. 2015 Nov-Dec;17(11-12):811-6. doi: 10.1016/j.micinf.2015.09.015. Epub 2015 Sep 30.

Authors

Alain Bizzini¹, Olivier Péter², David Baud³, Sophie Edouard⁴, Pascal Meylan¹, Gilbert Greub⁵

Affiliations

¹ Institute of Microbiology, University of Lausanne, University Hospital Center, Lausanne, Switzerland.
² Department of Infectious Diseases, Central Institute of Valais, Sion, Switzerland.
³ Institute of Microbiology, University of Lausanne, University Hospital Center, Lausanne, Switzerland; Department of Obstetrics and Gynaecology, University Hospital of Lausanne, Lausanne, Switzerland.
⁴ URMITE UMR 6236, Faculté de Médecine et de Pharmacie, Marseille, France.
⁵ Institute of Microbiology, University of Lausanne, University Hospital Center, Lausanne, Switzerland. Electronic address: gilbert.greub@chuv.ch.

PMID: 26432518
DOI: 10.1016/j.micinf.2015.09.015

Abstract

Coxiella burnetii and members of the genus Rickettsia are obligate intracellular bacteria. Since cultivation of these organisms requires dedicated techniques, their diagnosis usually relies on serological or molecular biology methods. Immunofluorescence is considered the gold standard to detect antibody-reactivity towards these organisms. Here, we assessed the performance of a new automated epifluorescence immunoassay (InoDiag) to detect IgM and IgG against C. burnetii, Rickettsia typhi and Rickettsia conorii. Samples were tested with the InoDiag assay. A total of 213 sera were tested, of which 63 samples from Q fever, 20 from spotted fever rickettsiosis, 6 from murine typhus and 124 controls. InoDiag results were compared to micro-immunofluorescence. For acute Q fever, the sensitivity of phase 2 IgG was only of 30% with a cutoff of 1 arbitrary unit (AU). In patients with acute Q fever with positive IF IgM, sensitivity reached 83% with the same cutoff. Sensitivity for chronic Q fever was 100% whereas sensitivity for past Q fever was 65%. Sensitivity for spotted Mediterranean fever and murine typhus were 91% and 100%, respectively. Both assays exhibited a good specificity in control groups, ranging from 79% in sera from patients with unrelated diseases or EBV positivity to 100% in sera from healthy patients. In conclusion, the InoDiag assay exhibits an excellent performance for the diagnosis of chronic Q fever but a very low IgG sensitivity for acute Q fever likely due to low reactivity of phase 2 antigens present on the glass slide. This defect is partially compensated by the detection of IgM. Because it exhibits a good negative predictive value, the InoDiag assay is valuable to rule out a chronic Q fever. For the diagnosis of rickettsial diseases, the sensitivity of the InoDiag method is similar to conventional immunofluorescence.

Keywords: Coxiella burnetii; Immunofluorescence; Multiplexed serology; Rickettsia conorii; Rickettsia typhi.

Publication types

Evaluation Study

MeSH terms

Animals
Antibodies, Bacterial / blood*
Antibodies, Bacterial / immunology
Boutonneuse Fever / diagnosis*
Boutonneuse Fever / immunology
Boutonneuse Fever / microbiology
Coxiella burnetii / immunology
Humans
Immunoassay / methods*
Immunoglobulin G / blood*
Immunoglobulin G / immunology
Immunoglobulin M / blood*
Immunoglobulin M / immunology
Mice
Q Fever / diagnosis*
Q Fever / immunology
Q Fever / microbiology
Rickettsia conorii / immunology
Rickettsia typhi / immunology
Serologic Tests / methods
Typhus, Endemic Flea-Borne / diagnosis*
Typhus, Endemic Flea-Borne / immunology
Typhus, Endemic Flea-Borne / microbiology

Substances

Antibodies, Bacterial
Immunoglobulin G
Immunoglobulin M