Diphtheria Toxin Testing Service

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Requisition Forms

Reference Details

Description:

This service consists of the molecular detection of the Diphtheria Toxin (DT) tox gene by real-time PCR and, phenotypic detection of expressed diphtheria toxin by the modified Elek test.

Test Category:
Reference Service
Pathogen:
Corynebacterium pseudotuberculosis
Illnesses and Diseases:
  • Lymphadenitis
  • Cutaneous infections
Specimen:

Pure cultures of Corynebacterium pseudotuberculosis.

Collection Method:

Slants or plates of any suitable media and swabs in transport media are all acceptable. Slants preferred.

Specimen Processing, Storage and Shipping:

Store samples between room temperature and 37oC until shipped for testing. Ship at room temperature.

Transportation of Dangerous Goods:

Shipping of specimens shall be done by a TDG certified individual in accordance with TDG regulations. For additional information regarding classification of specimens for the purposes of shipping, consult either Part 2 Appendix 3 of the TDG Regulations or section 3.6.2 of the IATA Dangerous Goods Regulations as applicable.

For additional guidance on the transport of infectious substances in other languages, please click on the link below.

http://www.who.int/ihr/capacity-strengthening/infectious-substances/en/

Patient Criteria:

Suspected diphtheria case with symptoms for respiratory diphtheria, throat diphtheria, cutaneous diphtheria, endocarditis, pharyngitis, and lymphadenitis.

Accompanying Documentation:

Completed Special Bacteriology requisition form detailing all patient information and relevant clinical information. If possible, attach lab results that have already been done at local or provincial laboratories.

 

Comments:

All patient and strain history must be included.  For urgent samples, prior contact with the laboratory is required.

Methods and Interpretation of Results:

A multiplex real-time PCR is used to detect 2 targets within the fragment A of the DT tox gene, as well as a Corynebacterium diphtheriae species specific sequence of the rpoB gene. The phenotypic detection for the gene expression using the modified Elek test is ONLY performed on samples that are PCR positive for the tox gene. Strains with a positive PCR result but Elek negative (gene present but not expressed) are considered non-toxigenic (1).  C. ulcerans and C. pseudotuberculosis are identified using sequence analysis of the rpoB gene.

Turnaround Time:

9 calendar days.  For urgent samples, testing may be expedited if there is prior contact with the laboratory.   In cases where staff or resources are limited final report may be delayed and status of request will be forwarded in a preliminary report.  Final report will be sent once all results from the molecular and phenotypic detection of diphtheria toxin as well as all other relevant tests are complete.

Contact:
Phone: (204) 789-2137
Fax: (204) 784-7509
References:
  1. Bernard, K. A.. 2019. Coryneform Gram-Positive Rods. In Manual of Clinical Microbiology. 12th ed. ASM publications, Washington DC. Pg 488-524.
  2. Efstratiou, A., KH Engler, CS Dawes, and D Sesardic. 1998. Comparision of Phenotypic and Genotypic Methods for Detection of Diphtheria Toxin among Isolates of Pathogenic Corynebacteria. J Clin Microbiol. 36(11): 3173-3177.
  3. Efstratiou, A, and RC George. 1999. Laboratory guidelines for the diagnosis of infections caused by Corynebacterium diphtheriae and C. ulcerans. Communicable Disease and Public Health 2(4):250-257.
  4. Public Health Agency of Canada.  2009.  Case description for Communicable Diseases under National Surveillance-Diphtheria. CCDR supple. Vol 35S2. Pg 63-64.
  5. CDC Atlanta. Insert brochure for catalogue no. BS0629 C. diphtheriae reference antitoxin for use in toxigenicity test.  NOTE that description is consistent with the classic, not Modified ELEK test.
  6.  Engler, K. H., T. Glushkevick, I. K. Mazurova et al. 1997. A modified ELEK test for detection of toxigenic Corynebacteria in the diagnostic laboratory. J. Clin. Microbiol. 35:495-498.
  7. Khamis, A, Raoult, D, La Scola, B. 2004. rpoB Gene Sequencing for Identification of Corynebacterium Species. JCM 42: 3925-3931
  8. Schuhegger, R., Lindermayer, M., Kugler, R., Heesemann, J., Busch, U., & Sing, A. (2008). Detection of Toxigenic Corynebacterium diphtheriae and Corynebacterium ulcerans Strains by a Novel Real-Time PCR. J. Clin. Microbiol. 46(8), 2822-2823. doi:10.1128/jcm.01010-08.
  9. Zoysa, A. D., Efstratiou, A., Mann, G., Harrison, T. G., & Fry, N. K. (2016). Development, validation and implementation of a quadruplex real-time PCR assay for identification of potentially toxigenic corynebacteria. J. Med. Microbiol. 65(12), 1521-1527. doi:10.1099/jmm.0.000382.
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