Clinical use
Investigation for the identification of C. diptheriae.
Background
Diphtheria is an acute infectious disease of the upper respiratory tract and occasionally the skin. It is caused by toxigenic strains of Corynebacterium diphtheriae (of which there are 4 biotypes – gravis, mitis, intermedius and belfanti) and some toxigenic strains of Corynebacterium ulcerans and pseudotuberculosis. All can carry the phage-borne diphtheria toxin gene. In a fully developed case of diphtheria, this toxin damages the pharyngeal epithelium to produce a leathery membrane, giving the disease its name. This membrane may occlude the airway, sometimes causing death by respiratory obstruction. Systemic absorption by the host of the toxin from the primary site of replication may damage a wide range of cells, including those of the heart and nervous system. Myocarditis and neurological dysfunction may cause or contribute to disability or death.
Mild cases of the disease resemble streptococcal pharyngitis and the classic pseudo membrane of the pharynx may be lacking. It is thought that C. diphtheriae has additional virulence factors because invasive disease caused by non-toxigenic strains has been reported.
In the 1990s there was an increase in the incidence of diphtheria in Russia and other former Soviet states, although the situation is now improving. Diphtheria cases have continued to be reported from every WHO Region, especially the higher risk regions e.g., Africa, Southeast Asia and South America. In a susceptible population the introduction of a toxigenic strain can result in direct spread by droplet infection. Mass immunisation has resulted in the virtual disappearance of toxigenic C. diphtheriae from the United Kingdom, but it might not have affected the carriage of non-toxigenic strains.
There are specific clinical associations and exposures which, if reported on request forms, should trigger examination of specimens for C. diphtheriae or C. ulcerans.
Patient preparation
Throat swabs should be taken from the tonsilar area and/or posterior pharynx. Swabs should be transported in Copan E swab orange top.
Please see Bacteriology e-Swab user guide.
Specimen requirements
Orange capped e-Swab from the Throat or nose from a patient with one or more of the following risk factors reported:
- Membranous or pseudomembranous pharyngitis/tonsillitis
- Contact with a confirmed case within the last 10 days
- Travel overseas (especially Russia and Former Soviet States, Africa, South America and South-East Asia) within the last 10 days
- Recent contact with someone who has travelled overseas recently (especially Russia and Former Soviet States, Africa, South America and South-East Asia)
- Recent consumption of raw milk products (C. ulcerans)
- Recent contact with farms/farm animals or domestic animals (C. ulcerans)
- The patient works in a clinical microbiology laboratory, or similar, where Corynebacterium species may be handled
Limitations and restrictions
If processing is delayed, refrigeration is preferable to storage at ambient temperature.
Turnaround time
4 days
Analysing laboratory
Microbiology Lab, James Cook University Hospital, Marton Road, TS4 3BW
Additional information
Please see Bacteriology e-Swab user guide.