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Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

Internal Resources


Item Value
Available Stat? No
Test code THRC
Performed by? Microbiology (Bacteriology)
Sendout? no
Price range $$
In House Availability 7 days
Principle Smears will be stained with methylene blue and Gram stain and examined for palisading Gram positive rods with swollen ends and stained bands or granules.

Differential medium (Cystine Tellurite), Selective Strep Agar and blood agar will be inoculated and incubated for a minimum of 48 hours. Culture plates are examined daily for colonies typical of Corynebacterium diphtheriae.
Interpretation When there is clinical suspicion of diphtheria, treatment should not be delayed pending the result of culture.

Diphtheria is a toxin-mediated infectious disease caused by C. diphtheriae. The disease is an acute, contagious, febrile illness characterized by local oropharyngeal inflammation and pseudomembrane formation with possible airway obstruction. Exotoxin produced by the organism can cause damage to the heart and peripheral nerves.

The classic pseudomembrane of the pharynx may be lacking in mild cases, which usually mimic streptococcal pharyngitis. Antibiotics have little effect on the clinical outcome and laboratory confirmation of the presence of toxigenic C. diphtheriae requires days, yet diagnosis and antibiotic treatment are essential in limiting further spread.

Wounds, ulcers, and other lesions may become infected by C. diphtheriae. Lesions like pseudomembranes may be formed when the bacterium is toxigenic. Notify the laboratory if C. diphtheriae is suspected.
Collection Instructions For suspected cases of diphtheria, obtain two swabs from the base of the pseudomembrane. Put swabs in each of two transport medium tubes and the scrapings in a sterile tube.
Sample type Swab and scrapings
Special instructions Culture for Corynebacterium diphtheriae is not part of a routine culture request. Please write in a request for "diphtheria" in the "add to routine culture" portion of the Bacteriology Test Request Section of the Microbiology requisition.
Synonyms Diphtheria Culture;Throat Culture;
Stability Specimens should be transported to the laboratory immediately after collection or held at room temperature until delivery to the lab.
References 1. Clinical Microbiology Procedures Handbook, 2nd Ed., HD Isenberg, Ed. Amer. Soc. for Microbiol., Washington DC, 2004.

2. Forbes BA, et al. Bailey and Scott's Diagnostic Microbiology, 11th Ed. Mosby, St. Louis MO, 2002.

3. Murray PR, et al. Manual of Clinical Microbiology, 9th Ed., ASM Press, Washington DC, 2007.
CPT coding 87070
Last Updated 8/19/2009 1:19:10 PM
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