Lateral flow immunoassay-based laboratory algorithm for rapid diagnosis of diphtheria

Vyacheslav G Melnikov; Anja Berger; Alexandra Dangel; Andreas Sing

doi:10.12688/openreseurope.15038.1

Lateral flow immunoassay-based laboratory algorithm for rapid diagnosis of diphtheria

Open Res Eur. 2023 Apr 25:3:62. doi: 10.12688/openreseurope.15038.1. eCollection 2023.

Authors

Vyacheslav G Melnikov¹, Anja Berger², Alexandra Dangel², Andreas Sing²

Affiliations

¹ National Conciliary Laboratory on Diphtheria, Bavarian Health and Food Safety Authority, Oberschleißheim, 85764, Germany.
² Public Health Microbiology, National Conciliary Laboratory on Diphtheria, Bavarian Health and Food Safety Authority, Oberschleißheim, 85764, Germany.

Abstract

Background: In industrialised countries diphtheria is a rare but still life-threatening disease with a recent increase in cases due to migration and zoonotic aspects. Due to the rarity of the disease, laboratory diagnosis of diphtheria is often carried out in central reference laboratories and involves the use of sophisticated equipment and specially trained personnel. The result of the diphtheria agent detection can usually be obtained after 5-6 days or more. Authors suggest a Lateral Flow Immunoassay (LFIA)-based laboratory algorithm for the diagnosis of diphtheria, which may render less time in issuing a result and could promote the testing be performed in laboratories closer to the patient. Methods: LFIA for diphtheria toxin (DT) detection was designed using a pair of monoclonal antibodies to receptor-binding subunit B of the DT, and validated with 322 corynebacterial cultures as well as 360 simulated diphtheria specimens. Simulated diphtheria specimens were obtained by spiking of human pharyngeal samples with test strains of corynebacteria. The simulated specimens were plated on selective tellurite agar and after 18-24 hours of incubation, grey/black colonies characteristic of the diphtheria corynebacteria were examined for the DT using LFIA. Results: The diagnostic sensitivity of the LFIA for DT detection on bacterial cultures was 99.35%, and the specificity was 100%. Also, the LFIA was positive for all pharyngeal samples with toxigenic strains and negative for all samples with non-toxigenic strains. For setting LFIA, a 6-hour culture on Elek broth was used; thus, under routine conditions, the causative agent of diphtheria could be detected within two working days after plating of the clinical specimen on the tellurite medium of primary inoculation. Conclusions: The availability of such a simple and reliable methodology will speed up and increase the accuracy of diphtheria diagnosis globally.

Keywords: Corynebacterium diphtheriae; Corynebacterium ulcerans; LFIA; simulated diphtheria specimens; diphtheria laboratory diagnosis.

Grants and funding

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 843405.