Corynebacterium diphtheriae Isolate Identification

Laboratory Fee Schedule
Procedure Number: MAA0054A, MAA0033A

Synonym(s): diphtheria, Gram positive rod identification
Requisition Form G-2B
Test Description Identification confirmation of Corynebacterium diphtheriae from pure isolate specimens by MALDI-TOF or conventional biochemicals, with reflex toxin testing at CDC if isolate is C. diphtheriae    
Pre-Approval Needed N/A
Supplemental Information Required

If C. diphtheria is suspected, please include date of onset of symptoms and antibiotic history, if available.

Supplemental Form(s) N/A
Performed on Specimens from (sources) Human
Sample/Specimen Type for Testing Pure isolate from throat, nose, or wound
Minimum Volume/Size Required At least one viable colony of pure isolate per plate/slant)
Storage/Preservation Prior to Shipping Maintain isolate on any agar or transport medium that supports the growth of Corynebacterium spp. 
Store refrigerated at 2–8°C until shipment.   

Transport Medium

Any agar or transport medium that supports the growth of Corynebacterium spp., such as blood, chocolate, trypticase soy, nutrient, brain heart infusion, heart infusion, Aimes clear gel, etc.
Specimen Labeling
  • At least two patient identifiers required on specimen (e.g., patient full name, date of birth, medical record number). 
  • Three patient identifiers are preferred. 
  • Patient identifiers on specimen label must exactly match identifiers on submission form. (e.g., abbreviated name on label and full name on form is not acceptable.)
  • Additional DSHS Laboratory specimen labeling guidelines available online here.
Shipping and Specimen Handling Requirements
  • Ship refrigerated at 2–8°C on cold packs for overnight delivery
  • Ship according to Dangerous Goods Regulations, IATA, and/or CFR 49.
  • Category B Biological Substance, UN3373 shipping requirements apply.
  • Handle as infectious agent using universal precautions. 
  • Triple-contain in accordance with federal shipping regulations. 
  • Submitters are responsible for packaging and shipping specimens according to regulatory requirements. 
  • Laboratory does not supply collection kits or shipping materials.
  • Additional DSHS Laboratory specimen shipping guidelines online here
Method MALDI-TOF (mass spectrometry), Culture
Turn-around Time 3–5 days 
  • Specimen should be taken from patient prior to antimicrobial therapy.  
  • Organism must be viable for culture studies.  
  • Improper storage or shipping temperatures limit organism recovery.
Common Causes for Rejection
  • Incorrect specimen collection methods 
  • Mismatch(es) between patient identifiers on G-2B submission form and specimen label 
  • Insufficient specimen growth
  • Non-viable isolates
  • Mixed culture/contamination
  • Incorrect storage conditions 
  • Expired reagents/media/collection container
  • Missing/incomplete/illegible submission form
Additional Information
  • If C. diphtheriae is confirmed, it will be submitted (reflexed) to CDC for toxin testing. 
  • Diphtheria is a notifiable condition and C. diphtheriae isolates are REQUIRED to be submitted to DSH Laboratory per Texas Administrative Code (TAC) chapter 97.  
  • Mark the “IDEAS” box for the payor source on the G-2B submission form.