In 1924, Gaston Ramon working at the Pasteur Institute in France developed the diphtheria toxoid by inactivating the diphtheria toxin using formalin and heat. The inactivated toxin was no longer able to cause toxicity and necrosis but could still elicit an antibody response from the body. This later proved to be the most effective means to prevent and treat diphtheria.
One of the more well-known diphtheria outbreaks occurred in January 1925 in Nome, Alaska.6,7 Since the 1890s, antitoxin produced in horses was widely used to treat diphtheria. Nome had no antitoxin available that was not expired so antitoxin had to be shipped by train from Anchorage to the town of Nenana. From Nenana 20 different sled dog crews took a portion of the journey to rush it the 674 miles to Nome. This amazing race captured the nation and the antitoxin arrived safely in Nome to treat the children sick with diphtheria.
According to the World Health Organization (WHO), cases of diphtheria in the United States numbered 2 in 2020, n=1 in 2021, and n= 0 reported in 2022. (The low number of US cases is due to a successful vaccination program.) In 2019, WHO reported that the largest number of diphtheria cases occurred in India with 9,622 cases, followed by Ethiopia with 7,184, and Nigeria with 2,289 cases; since that time, global cases have dropped significantly, possibly due to the use of Covid-19 pandemic isolation precautions.8
Primary isolation
For primary isolation of C. diphtheriae, Loeffler agar, Mueller-Miller tellurite agar, or Tinsdale tellurite agar may be used: sterile cotton-tipped applicators are used to swab the pharyngeal tonsil area. (Refer to the image; this bacteria produces blackish colonies in the presence of tellurite.) Routine media is not helpful in the isolation of C. diphtheria, either because of the overgrowth of normal flora which may occur (as on blood or chocolate agar), or because it is inappropriate (as with MacConkey agar, useful for gram-negative enterics).
