Pathogenesis and Spectrum of Disease for Listeria, Corynebacterium, and Similar Organisms
المؤلف:
Patricia M. Tille, PhD, MLS(ASCP)
المصدر:
Bailey & Scotts Diagnostic Microbiology
الجزء والصفحة:
13th Edition , p273-277
2025-06-03
529
L. monocytogenes, by virtue of its ability to survive within phagocytes, and C. diphtheriae, by production of an extremely potent cytotoxic exotoxin, are the most virulent species listed in Table 1. Not all strains of C. diphtheriae are toxin-producing strains. The toxin gene is present in strains that have acquired the gene by viral transduction. The result is the incorporation of the toxin gene into the organisms’ genome. C. diphtheriae occurs in four biotypes: gravis, intermedius, belfanti, and mitis; C. gravis causes the most severe form of disease. The biotypes can be differentiated based on colonial morphology, biochemical reactions, and hemolytic patterns on blood agar.
Table1. Pathogenesis and Spectrum of Diseases
Table1. Pathogenesis and Spectrum of Diseases—cont’d
L. monocytogenes is ingested through contaminated food. Once the organism has been phagocytized by white blood cells, it produces listeriolysin O, the major virulence factor. Listeriolysin O in combination with phospholipases enables the organism to escape from the white blood cells and spread to the bloodstream, eventually reaching the central nervous system and the placenta.
Most of the remaining organisms in Table 1 are opportunistic, and infections are associated with immunocompromised patients. For this reason, whenever Corynebacterium spp. or the other genera of gram-positive rods are encountered, careful consideration must be given to their role as infectious agents or contaminants. Coryne bacterium urealyticum is an up-and-coming cause of cystitis in hospitalized patients, in those who have undergone urologic manipulation, and in the elderly.
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