Corynebacteria and related species

Diagnosis The diagnosis of diphtheria is based on clinical signs and symptoms plus laboratory confirmation. Respiratory diphtheria should be considered in patients with sore throat, pharyngeal exudates, and fever. Other symptoms may include hoarseness, stridor, or palatal paralysis. The presence of a pseudomembrane should prompt consideration of diphtheria. Once a clinical diagnosis of diphtheria is made, diphtheria antitoxin should be administered as soon as possible. Laboratory diagnosis is based either on cultivation of C. diphtheriae or toxigenic C.

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Management Patients in whom diphtheria is suspected should be hospitalized in respiratory isolation rooms, with close monitoring of cardiac and respiratory function. A cardiac workup is recommended to assess the possibility of myocarditis. In patients with extensive pseudomembranes, consultation with an anesthesiologist or an ear, nose, and throat specialist is recommended because of the possibility that tracheostomy or intubation will be required. In some settings, pseudomembranes can be removed surgically.

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Clinical Manifestations Respiratory Diphtheria The clinical diagnosis of diphtheria is based on the constellation of sore throat; adherent tonsillar, pharyngeal, or nasal pseudomembranous lesions; and low-grade fever. In addition, diagnosis requires the isolation of C. diphtheriae or the histopathologic isolation of compatible gram-positive organisms.

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Harrison's Internal Medicine Chapter 131. Diphtheria and Other Infections Caused by Corynebacteria and Related Species Diphtheria Diphtheria is a nasopharyngeal and skin infection caused by Corynebacterium diphtheriae. Toxigenic strains of C. diphtheriae produce a protein toxin that causes systemic toxicity, myocarditis, and polyneuropathy. The toxin is associated with the formation of pseudomembranes in the pharynx during respiratory diphtheria. While toxigenic strains most frequently cause pharyngeal diphtheria, nontoxigenic strains commonly cause cutaneous disease.

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Pathogenesis and Immunology Diphtheria toxin, produced by toxigenic strains of C. diphtheriae, is the primary virulence factor in clinical disease. The toxin is synthesized in precursor form; is released as a 535-amino-acid, single-chain protein; and has an LD50 of ~100 ng/kg of body weight. The toxin is produced in the pseudomembranous lesion and is taken up into the bloodstream, through which it is distributed to all organ systems.

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Other Nondiphtherial Corynebacteria C. xerosis is a human commensal found in the conjunctiva, nasopharynx, and skin. This nontoxigenic organism is occasionally identified as a source of invasive infection in immunocompromised or postoperative patients and prosthetic joint recipients. C. striatum is found in the anterior nares and on the skin, face, and upper torso of normal individuals. Also nontoxigenic, this organism has been associated with invasive opportunistic infections in severely ill or immunocompromised patients. C.

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Microbiology and Laboratory Diagnosis These organisms are non-acid-fast, catalase-positive, aerobic or facultatively anaerobic bacilli. Their colonial morphologies vary widely; some species are small and α-hemolytic (similar to lactobacilli), whereas others form large white colonies (similar to yeasts). Many nondiphtherial coryneforms require special medium (e.g., Löffler's, Tinsdale's, or telluride medium) for growth. Epidemiology Humans are the natural reservoirs for several nondiphtherial coryneforms, including C. xerosis, C. pseudodiphtheriticum, C. striatum, C.

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