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Notes from the Field: Respiratory Diphtheria-Like Illness Caused by Toxigenic Corynebacterium ulcerans --- Idaho, 2010

On September 12, 2010, the Idaho Department of Health and Welfare was notified of a case of respiratory diphtheria-like illness in an Idaho man aged 80 years whose pharyngeal specimens yielded Corynebacterium ulcerans. Although C. ulcerans is zoonotic, the patient reported no animal contact or consumption of an unpasteurized dairy product. His vaccination history was unknown. Respiratory diphtheria-like illness from C. ulcerans is uncommon but has been reported in industrialized countries where respiratory diphtheria is rare. The last case of diphtheria-like illness caused by C. ulcerans in the United States was reported in 2005 (1).

On September 5, the patient had sought medical attention for nasal congestion and voice changes; treatment for allergic rhinitis did not improve his condition. On September 9, the patient was hospitalized for a surgical procedure to alleviate bilateral obstruction of the nasal passages, during which a pseudomembrane was observed. On September 11, he experienced stridor, required intubation, and became febrile with signs of sepsis. Throughout the next day, severe neck swelling developed, and a computed tomography scan revealed pronounced hypopharyngeal mucosal thickening. On suspicion of respiratory diphtheria, the patient was treated with azithromycin. On September 12, C. ulcerans was isolated from pharyngeal tissue surgically removed on September 9, and a 100,000 international-unit dose of diphtheria antitoxin (DAT) was requested and received from CDC. After DAT administration on September 12, the patient had a complicated recovery and was discharged on October 6. On September 20, CDC reported that the C. ulcerans isolates were toxigenic by the Elek agar virulence test.

Respiratory diphtheria-like illness caused by toxigenic C. ulcerans infections can be clinically indistinguishable from toxigenic Corynebacterium diphtheriae infections. Both organisms can produce diphtheria toxin and lead to life-threatening disease that requires urgent treatment with DAT and antibiotics. Although the hallmark of respiratory diphtheria is the presence of a pseudomembrane in the pharynx (1), the pseudomembrane in this patient was only visible during a surgical procedure. Clinicians should consider respiratory diphtheria among patients who have low-grade fever and pseudomembranous pharyngitis. If diphtheria is suspected, patients should receive urgent treatment with DAT without waiting for laboratory confirmation. Health-care providers can obtain DAT by contacting CDC's Emergency Operations Center at 770-488-7100.

Antibiotic treatment of diphtheria-like illness caused by C. ulcerans should follow clinical guidelines for patients infected with C. diphtheriae (2). Unlike C. diphtheriae infections, human-to-human transmission of C. ulcerans infections has not been documented (3); therefore, postexposure antibiotic prophylaxis was not administered to close contacts of the Idaho patient. However, because studies on the transmission of C. ulcerans are limited, vaccination status of contacts should be assessed and brought up-to-date, if necessary, with an age-appropriate diphtheria-toxoid--containing vaccine, which prevents disease from toxigenic strains of C. diphtheriae and C. ulcerans. CDC recommends that adults receive a diphtheria-toxoid--containing vaccine every 10 years after completing a primary childhood vaccination series (4).

Reported by

SR Blue, MD, Sawtooth Epidemiology and Infectious Diseases, Boise; C Hahn, MD, Idaho Dept of Health and Welfare. P Cassiday, MS, T Tiwari, MD, Div of Bacterial Diseases, National Center for Immunization and Respiratory Diseases; K Carter, DVM, Office of Public Health Preparedness and Response; JM Colborn, PhD, EIS Officer, CDC.


  1. Tiwari TS, Golaz A, Yu DT, et al. Investigations of 2 cases of diphtheria-like illness due to toxigenic Corynebacterium ulcerans. Clin Infect Dis 2008;46:395--401.
  2. American Academy of Pediatrics. Diphtheria. In: Pickering LK, Baker CJ, Kimberlin DW, Long SS, eds. Red book: 2009 report of the Committee on Infectious Diseases. 28th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2009:280--3.
  3. Lartigue MF, Monnet X, Le Flèche A, et al. Corynebacterium ulcerans in an immunocompromised patient with diphtheria and her dog. J Clin Microbiol 2005;43:999--1001.
  4. CDC. Recommended adult immunization schedule---United States, 2010. MMWR 2010;59(1).

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