Corynebacterium diphtheriae (Diptheria)

Causative agent of diphtheria. Club-shaped, and often arranged in "L" or "V"- shaped formations. Pathogenic C. diphtheriae contain granules with volutin, aka, polyphosphate, which provide intracellular energy storage and stain metachromatically. Non-motile Airborne transmission, human-human is typical. Bacteria colonize the oropharynx and skin of asymptomatic carriers, which maintains their presence within populations. Four subtypes of C. diphtheriae; the mitis biotype is most often responsible for human disease. Lysogenic bacteriophages introduce the Diphtheria toxin gene into the bacteria. The A subunit acts via ADP-ribosylation of elongation-factor 2 to inactivate host cell protein synthesis. The B subunit has two regions: Binding region binds heparin-binding EGF-like growth factor, which is anchored to the membranes of many host cells, particularly heart and nerve cells. Translocation region facilitates movement of diphtheria toxin into the host cell. Sudden onset of fever, sore throat, and adenopathy. Pharyngeal exudate forms a pseudomembrane that can extend to the larynx. Comprises immune cells, bacteria, and fibrin, and, unique to diphtheria. It is firmly adhered to the underlying tissue. Complications: Obstructed airways. Neurotoxicity, which tends to manifest as cranial nerve weakness beginning in the pharynx. Myocarditis is common in diphtheria, and tends to appear a week or two after illness onset. Edema with inflammation in the myocardium. Arrhythmia, heart failure, and death. Occurs after skin contact with an infected person. Characterized by chronic ulcers, which may be covered by gray membranes. Typically, in the U.S, children are given a series of injections with a combined preparation of diphtheria, pertussis, and tetanus antigens. Booster immunizations should be given every 10 years after the last childhood injection. Antitoxin should be given immediately because the toxins bind irreversibly and cause cell death. – Test for hypersensitivity because serum sickness can occur. Antibiotics such as Penicillin G or erythromycin should be prescribed. Vaccinate after recovery. Many people do not develop protective antibodies in response to natural diphtheria infections.