In severe cases, when other measures fail, a tracheostomy may be necessary to restore breathing. The diphtheria bacillus also produces a toxin that spreads throughout the body and may damage the heart and nerves permanently. Diagnosis of the disease can be verified by identifying the causative organisms from throat cultures. Susceptibility to diphtheria is determined by the Schick test. A positive skin test indicates the absence of circulating antibodies to the diphtheria toxin, but a pseudoreaction can also occur.
Diphtheria antitoxin is administered to counteract the toxic reaction from the bacillus.
Prognosis depends on the severity of the infection and especially on how soon the antitoxin is given. Bed rest, antibiotics, and general hygienic measures are used to combat the infection. Oxygen is administered as necessary to relieve dyspnea and cyanosis. The Centers for Disease Control and Prevention recommend strict isolation with special respiratory precautions for cases of pharyngeal diphtheria. The precautions are continued until two cultures from both the nose and throat, taken 24 hours apart after cessation of antimicrobial therapy, are negative for Corynebacterium diphtheriae.