This ADP-ribosylation involves the transfer of an ADP-ribose from NAD+ to a diphthamide (a modified histidine) residue within the EF-2 protein. Since EF-2 is needed for the moving of tRNA from the A-site to the P-site of the ribosome during protein translation, ADP-ribosylation of EF-2 prevents protein synthesis.ADP-ribosylation of EF-2 is reversed by giving high doses of nicotinamide (a form of vitamin B3), since this is one of the reactions end products, and high amounts drive the reaction in the opposite direction. Diagnosis
The current clinical case definition of diphtheria used by the United States Centers for Disease Control and Prevention  is based on both laboratory and clinical criteria. Laboratory criteria
Isolation of C. diphtheriae from a Gram stain or throat culture from a clinical specimen,
Histopathologic diagnosis of diphtheria by Alberts stain

Toxin demonstration
In vivo tests (guinea pig inoculation): Subcutaneous and intracutaneous tests
In vitro test: Eleks gel precipitation test, detection of tox gene by PCR, ELISA, ICA

Clinical criteria
Upper respiratory tract illness with sore throat
Low-grade fever (above 39 °C (102 °F) is rare)
An adherent, dense, grey pseudomembrane covering the posterior aspect of the pharynx: in severe cases, it can extend to cover the entire tracheobronchial tree. Case classification
Probable: a clinically compatible case that is not laboratory-confirmed and is not epidemiologically linked to a laboratory-confirmed case
Confirmed: a clinically compatible case that is either laboratory-confirmed or epidemiologically linked to a laboratory-confirmed caseEmpirical treatment should generally be started in a patient in whom suspicion of diphtheria is high.
Imiquimod may be used prior to surgery in order to reduce the size of the carcinoma. Some advocate the use of imiquimod prior to Mohs surgery to remove the superficial component of the cancer.Research suggests that treatment using Euphorbia peplus, a common garden weed, may be effective. Australian biopharmaceutical company Peplin is developing this as topical treatment for BCC. Radiation
Radiation therapy can be delivered either as external beam radiotherapy or as brachytherapy (mostly internal radiotherapy). Although radiotherapy is generally used in older patients who are not candidates for surgery, it is also used in cases where surgical excision will be disfiguring or difficult to reconstruct (especially on the tip of the nose, and the nostril rims). Radiation treatment with external radiation often takes as few as 5 visits to as many as 25 visits. Usually, the more visits scheduled for therapy, the less complication or damage is done to the normal tissue supporting the tumor. Radiotherapy can also be useful if surgical excision has been done incompletely or if the pathology report following surgery suggests a high risk of recurrence, for example if nerve involvement has been demonstrated. Cure rate can be as high as 95% for small tumor, or as low as 80% for large tumors. A variation of an external brachytherapy is the epidermal radioisotope therapy (e.g. with 188Re in form of the Rhenium-SCT). It is used in accordance to the general indications for brachytherapy and especially complex localisations or structures (e.g.