Identification, toxin determination and characterization of Corynebacterium diphtheriae and other toxinogenic Corynebacteria

Identification by MALDI-TOF mass spectrometry. Biochemical tests are necessary for the determination of the C. diphtheria subspecies.

• qPCR for the tox gene can be performed immediately on a pure culture of suspected corynebacteria. In case of a positive result, toxin production will be confirmed at a later point (some strains possess a mutated gene with a stop codon that blocks protein synthesis).
• qPCR for the detection of DNA of C. diphtheriae, C. ulcerans, and C. pseudotuberculosis, as well as the presence of the tox gene, can be performed immediately on clinical samples.
• Typing of isolates by means of whole genome sequencing (WGS).
• Antibiotic resistance by means of E-test on isolates.

Purpose of the test

Confirmation of diagnosis and outbreak investigation.

Criteria for performing this test in the context of reference activities

All suspect isolates are accepted. For qPCR on clinical sample, respiratory and cutaneous swabs are accepted, in case of high suspicion and after contact with the NRC. Upon confirmation of identification and tox gene presence, antibiotic susceptibility testing and further typing, as well as toxin production confirmation, shall be performed, if an isolate is available.

Instructions for samples

• Sample collection: pure culture or respiratory swab or skin lesion swab.
• Storage conditions: transport the sample to the reference laboratory as soon as possible.

Instructions for transport

• Transport conditions: room temperature, < 24 hours.
• Transport specifications: swab in Amies transport medium or eSwab, or pure culture.

Unacceptable requests

Not applicable.

Turnaround time (and frequency of analysis)

Depending on clinical need and impact on public health.

Reporting of test results

• By telephone, secured electronic mail and postal services in case of a positive result.
• By postal services in case of a negative result.