Rapid detection of brucellosis using a quantum dot-based immunochromatographic test strip.

Novel diagnostic tools are a major challenge for brucellosis research, especially in developing countries. Herein, we established a handheld quantum dot (QD) immunochromatographic device for the fast detection of brucellosis antibodies in the field. Total bacterial protein extracted from Brucella 104M served as labelling and coating antigen. QD labelling and immunochromatography methods were used to optimise reaction conditions, labelling conditions, reaction temperature and storage temperature. QD test strips were employed to test brucellosis serum to determine their sensitivity, specificity and stability. Test strips were compared with Rose Bengal test, standard agglutination test and colloidal gold immunochromatographic assay. Labelled Brucella total protein displayed good specificity and no cross-reactivity. The concentration of labelled total bacterial protein was 3.9 mg/ml, the coating concentration was 2.0 mg/ ml, and the serum titre with the lowest detection sensitivity was 1:25. The optimal reaction time for the test strip was 25−30°C. The test strip was stable after storage at room temperature and the repeatability was high, with a coefficient of variation of 4.0%. After testing 199 serum samples, the sensitivity of the QD test strip was 98.53%, the specificity was 93.57%, and the coincidence rate with the standard agglutination test was 96.98%. The developed QD immunochromatographic method can be used for rapid detection and preliminary screening of brucellosis in the field. Author summary: Brucellosis is a neglected infection that has a widespread geographic distribution. Based on an evaluation from the World Health Organization (WHO), brucellosis cases have been reported in more than 170 countries with about 500,000 new cases being reported each year. However, the actual number of brucellosis patients is much higher, and it is believed to be approximately 10–25 times the number of reported cases. This big discrepancy between the reported rate and the actual incidence rate is largely due to misdiagnosis and underdiagnosis, especially in endemic areas. In recent years, considerable effort has been mobilized toward the development of rapid, reliable field diagnostic assays and molecular diagnostic approaches. In this study, we established a handheld quantum dot (QD) immunochromatographic device for the fast detection of brucellosis antibodies in the field. This QD test strip does not require extensive laboratory infrastructure or technical expertise, and has high sensitivity (98.53%) and specificity (93.57%), as well as a high coincidence rate (96.98%) with SAT. This new tool is expected to provide fast and simple point-of-care testing at county-level clinics and CDC labs. [ABSTRACT FROM AUTHOR]