Diphtheria laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Dima Nimri, M.D. [2]
Overview
Laboratory Findings
A presumptive diagnosis of diphtheria is usually based on clinical features. A definitive diagnosis is made by growing the specific Corynebacterium species on special cultures from the respiratory tract secretions or cutaneous lesions.[1][2][3]
Culture and Staining
The diagnosis of diphtheria is made by culture and special staining for the different Corynebacterium species from respiratory tract secretions or cutaneous lesions:[1][2][3][4]
- Gram stain: Gram positive rods in a "Chinese character" distribution
- Tellurite stain: Gray-black colonies
- Tindale: Black colonies with halos around it and an associated garlic odor
- Loffler medium: Metachromatic staining
Biochemical Tests
Most species of Corynebacterium are catalase positive, urea negative, nitrate positive, pyrazinamidase negative and cystinase positive.[1]
Toxin Detection
The toxin for Corynebacterium diphtheria can be detected in a variety of methods, which include:[1][2]
- Elek's test
- PCR: a positive assay for the diphtheria toxin gene is not confirmatory, but rather suggests that Corynebacterium diphtheria is the causative agent. However, a negative assay rules it out.
- Enzyme immunoassay (EIA)
References
- ↑ 1.0 1.1 1.2 1.3 Efstratiou A, Engler KH, Mazurova IK, Glushkevich T, Vuopio-Varkila J, Popovic T (2000). "Current approaches to the laboratory diagnosis of diphtheria". J. Infect. Dis. 181 Suppl 1: S138–45. doi:10.1086/315552. PMID 10657205.
- ↑ 2.0 2.1 2.2 Colman G, Weaver E, Efstratiou A (1992). "Screening tests for pathogenic corynebacteria". J. Clin. Pathol. 45 (1): 46–8. PMC 495813. PMID 1740514.
- ↑ 3.0 3.1 Widelock D (1951). "Laboratory Diagnosis of Diphtheria". Am J Public Health Nations Health. 41 (1): 120. PMC 1525936. PMID 18017268.
- ↑ Mandell, Gerald L. (1985). Principles and Practice of Infectious Disease. USA: John Wiley & Sons. p. 1171. ISBN 0471876437.