Diphtheria laboratory findings
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A presumptive diagnosis of diphtheria is usually made based on an observation of clinical features. A definitive diagnosis is made by growing the specific Corynebacterium species on special cultures from the respiratory tract secretions or cutaneous lesions. Other tests include toxin detection via various methods.
A presumptive diagnosis of diphtheria is usually made based on clinical features. A definitive diagnosis can be made by growing the specific Corynebacterium species on special cultures from the respiratory tract secretions or cutaneous lesions. Other tests include toxin detection via various methods.
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:
- Gram stain: Gram positive rods in a distribution that is said to resemble Chinese characters
- Tellurite stain: Gray-black colonies
- Tindale: Black colonies with halos around it and an associated garlic odor
- Loffler medium: Metachromatic staining
Most species of Corynebacterium are catalase-positive, urea-negative, nitrate-positive, pyrazinamidase-negative and cystinase-positive.
The toxin for Corynebacterium diphtheria can be detected through a variety of methods, which include:
- 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 does rule it out.
- Enzyme immunoassay (EIA)
- ↑ 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.