ATLANTA – Seven cases of imported Corynebacterium diphtheriae in Minnesota highlight the importance of maintaining suspicion that cutaneous lesions in individuals with recent travel to endemic countries might be associated with C. diphtheriae infection.
The cases also underscore the importance of referring C. diphtheriae isolates to state health departments for confirmatory testing,of the Minnesota Department of Health, and her colleagues reported in a poster at the International on Emerging Infectious Diseases.
“C. diphtheriae infections was not clinically suspected in any of these case-patients. All infections were initially identified solely by [matrix-assisted laser desorption/ionization time-of-flight spectrometry] testing performed at the clinical institutions,” the investigators wrote. “Confirmation and further toxigenicity testing allowed for prompt case investigation and public health response, preventing disease spread.”
Infections caused by toxigenic C. diphtheriae are rare in the United States because of widespread vaccination, but remain endemic in countries with suboptimal vaccine coverage. For this reason, infection is a concern for unvaccinated individuals traveling to diphtheria-endemic countries as well as for those who have contact with people from these areas. The investigators noted that “infections are primarily respiratory or cutaneous; respiratory infections can be life-threatening and cutaneous wounds may serve as a reservoir from which bacteria can be transmitted to susceptible contacts.”
The Minnesota cases involved patients who presented with cutaneous ulcers between 2014 and 2017. The Minnesota Department of Health confirmed C. diphtheriae status by culture after the initial identification at private institutions or providers using matrix-assisted laser desorption/ionization time-of-flight spectrometry. Isolates were sent to the Centers for Disease Control and Prevention Pertussis and Diphtheria Laboratory for biotyping and confirmation of toxigenicity.
The CDC confirmed that isolates from two patients were toxigenic C. diphtheriae biotype mitis. The remaining cases were nontoxigenic diphtheria, including C. diphtheriae mitis (three case-patients, including one who also had Staphylococcus aureus, and another who also had methicillin-resistant S. aureus) and two case-patients with C. diphtheriae belfanti.
The patients with toxigenic infection included a 35-year-old woman who developed an abdominal boil after spending months in Somalia, and a 48-year-old man who cut his leg while in Ethiopia.
The patients with nontoxigenic infection included four foreign-born individuals ranging in age from 7 to 66 years and one 24-year-old man from the United States. One of the foreign-born individuals had immigrated from a diphtheria-endemic country 3 months prior to his diagnosis, but none of the remaining four had traveled outside the United States in the 6 months prior to infection onset. One, however, lived in a home with family members who traveled frequently to eastern Africa. The vaccination status of these patients was unknown.
Contact tracing was conducted and prophylactic antibiotics were recommended as appropriate. Vaccination was recommended when a case-patient and/or contact was inadequately immunized.
Both patients with toxigenic infection experienced wound healing after appropriate antibiotic therapy.
Ms. Griffith reported having no disclosures.