[Point-of-care tests for the rapid diagnosis of shigellosis]

Worldwide, it is estimated that 140 million people suffer from shigellosis annually. The traditional identification of Shigella spp. by culture lacks sensitivity. Rapid diagnosis of shigellosis is important because it allows to engage appropriate antimicrobial treatment that shortens the duration and severity of the illness and reduces microbial carriage, thus the spread of infection in the community. Onestep immunochromatographic dipstick tests have been successfully developed at Institut Pasteur for Shigella spp., Shigella flexneri 2a, Shigella sonnei, and Shigella dysenteriae 1. The present work describes the evaluation of these four rapid diagnostic tests (RDT) that addressed the issue of rapid diagnosis of Shigella diarrhea and dysentery testing from bacterial cultures, stools, and rectal swabs which is usually how the specimen is often collected or received from the field or from remote settings. The evaluations have been performed in Chile, Democratic Republic of Congo, Senegal, Djibouti, Vietnam, India, and France, in dispensaries, in emergency room, on the field, in public health laboratories, and by the French Army. The dipstick method used requires minimal technical skill, and the test can be read between 5 and 15 minutes. Stool cultures and the immunochromatographic test showed concordant results in the comparative studies when RDT for S. sonnei was tested in Chile, Vietnam, India, and France; specificity (Sp) was 96% and sensitivity (Se) was 100%. When RDT for S. flexneri 2a was tested in Vietnam, Se was 91.5% and Sp was 99.2%. In Chile, Se was 83.3% and Sp was 100%. When RDT for S. dysenteriae 1 was tested in India, Vietnam, Senegal, and France by laboratory technicians and in Democratic Republic of Congo by a field technician, the Sp was 98.7% and the Se was 91.7%. In Chile, the initial finding for a simple RDT to diagnose Shigella spp. demonstrates its promising potential to become a powerful tool for case management and epidemiological surveys. Additionally, the dipsticks can be stored at room temperature in a humidity-proof plastic bag, making them easily transportable. Considering the potential impact these RDT have for the clinical management of the disease and for epidemiological studies, industrialization of these tests is in progress.