Fragment A is so potent that a single molecule gaining entry into the cytoplasm can cause cell death within hours. Antitoxin antibody can neutralize toxin adsorbed to cells or the extracellular fluid. However, once the toxin penetrates cells, its toxic effects are irreversible. In the host, the cytotoxic effects of the toxin are most marked in regions where bacterial growth is heavy and toxin concentrations are highest. The incubation period for respiratory diphtheria is generally two to four days but can be up to seven days.
Symptoms depend on the location and duration of the infection before treatment.
Concentrations of bacteria increase over time, resulting in the release of increasing amounts of the cytotoxic exotoxin. Early recognition and treatment are therefore critical for reducing the complications associated with toxin dissemination. Respiratory Tract Infection Pharyngeal infection, the most common form of diphtheria, presents as a sore throat and malaise. Symptoms may be mild in vaccinated patients, whereas unvaccinated patients tend to have more severe disease. A streptococcal or viral pharyngitis.