User Tools

Site Tools


glossary:corynebacterium

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

glossary:corynebacterium [2012/10/16 14:40] (current)
Line 1: Line 1:
 +====== Corynebacterium ======
 + /​Co·ry·ne·bac·te·ri·um/​ (-bak-ter´e-um) a genus of [[bacteria]] including C. ac´nes, a species present in acne lesions, C. diphthe´riae,​ the etiologic agent of diphtheria, C. minutis´simum,​ the etiologic agent of erythrasma, and C. pseudodiphtheri´ticum,​ a nonpathogenic species present in the respiratory tract.
  
 +===== Corynebacterium Clinical =====
 +
 +ORGANISM:
 +
 +Genus: Corynebacterium ​
 +Species: diphtheriae
 +
 +GENERAL CONCEPTS:
 +Corynebacteria belong in the family Mycobacteriaceae and are part of the CMN group (Corynebacteria,​ Mycobacteria and Nocardia).The family Mycobacteriaceae are [[Gram-positive bacteria]], nonmotile, catalase-positive and have a rodlike to filamentous morphology (Corynebacteria are often pleomorphic). As a group, they produce characteristic long chain fatty acids termed mycolic acids. In the image to the right, the R-groups represent these chains. For Corynebacteria,​ chains of 28-40 carbons are common; for Nocardia, chains of 40-56 carbons are produced; for Mycobacteria,​ the chains are 60-90 carbons in length.
 +
 +DISTINCTIVE PROPERTIES:
 +Corynebacterial cell walls contain thin spots which leads to some Gram variability and "​ballooning"​ that produces a "​club-shaped"​ cell. Old cells store inorganic phosphate, which can appear as metachromatic granules when stained.
 +
 +PATHOGENESIS:​
 +C. diphtheriae is the etiologic agent of diphtheria. ​
 +These organisms colonize the mucus membranes of the respiratory tract and produce the enzyme neuraminidase which splits N-acetylneuraminic acid (NAN) from [[cell]] surfaces to produce pyruvate which acts as a growth stimulant. ​
 +C. diphtheriae also produces diphthin, which is a protease that inactivates IgA.
 + 
 +Toxigenic strains carry the [[gene]] tox, which resides on certain bacteriophages;​ lysogenization leads to toxigenicity.
 + 
 +The toxin that is produced is a single polypeptide of 62,000 daltons and contains a single disulfide cross-link. Digestion with trypsin gives 2 fragments, A and B. The B (binding) fragment attaches to [[cell]] surfaces then proteases release the A (active) fragment to enter the cell. In the cell, the toxin acts as an ADP-ribosyltransferase,​ inactivating translation factor EF2.
 +
 +HOST DEFENSES:
 +Humoral immunity (antitoxin) is important in preventing [[disease]]. ​
 +
 +EPIDEMIOLOGY:​
 +Diphtheria exists throughout the world and occasional outbreaks occur almost yearly. ​
 +The Schick test can be used to ascertain population risk. This test involves the injection of a minute amount of the diphtheria toxin under the skin. The absence of a reaction indicates immunity. ​
 +
 +DIAGNOSIS:
 +Clinical: Muscle weakness, edema and a pseudomembranous material in the upper respiratory tract characterizes diphtheria.
 + 
 +Laboratory: Tellurite media is the agar of choice for isolation of Corynebacteria,​ which produce jet black colonies.
 +
 +CONTROL:
 +Sanitary: Reduce carrier rate by use of vaccine. ​
 +Immunological:​ A vaccine (DPT) prepared from an alkaline formaldehyde inactivated toxin (i.e. toxoid) is required. Passive immunization with antitoxin can be used for patients. ​
 +Chemotherapeutic:​ [[Penicillin]],​ [[erythromycin]] or [[gentamicin]] are drugs of choice.
 +
 +===== Types of Corynebacterium =====
 +
 +==== Corynebacterium bovis ====
 +A common inhabitant of the bovine udder but not considered to be a pathogen. May have importance in protecting the udder from more damaging pathogens.
 +
 +==== Corynebacterium ====
 +Corynebacterium (previously Eubacterium,​ now Actinobaculum) cystitidis
 +Causes contagious bovine pyelonephritis.
 +
 +==== Corynebacterium equi ====
 +now called rhodococcus equi.
 +
 +==== Corynebacterium kutscheri ====
 +Causes systemic abscessation in rodents similar to caseous lymphadenitis in sheep. Previously called C. murium.
 +
 +==== Corynebacterium minutissimum ====
 +Found in wound infections in lambs.
 +
 +==== Corynebacterium parvum ====
 +Now called Propionibacterium acnes.
 +
 +==== Corynebacterium pseudotuberculosis ====
 +Cause of caseous lymphadenitis of sheep and goats, ulcerative lymphangitis,​ and canadian horsepox and pectoral abscesses of horses. Previously called C. ovis.
 +
 +==== Corynebacterium pyogenes ====
 +(now called Arcanobacterium) pyogenes, previously Actinomyces pyogenes.
 +
 +==== Corynebacterium rathayi ====
 +See clavibacter toxicus.
 +
 +==== Corynebacterium renale ====
 +Previously classified as types I, II and III, but now allocated separate names of C. renale, C. pilosum and C. cystitidis, respectively. Causes contagious bovine pyelonephritis,​ and balanoposthitis of bulls, and plays a large part in causing enzootic balanoposthitis in sheep.
 +
 +==== Corynebacterium suis ====
 +Recently called Eubacterium suis; now called Actinobaculum suis.
 +
 +==== Corynebacterium ulcerans ====
 +A rare cause of subacute bovine mastitis, but a recognized risk for people who drink raw milk.  ​
glossary/corynebacterium.txt · Last modified: 2012/10/16 14:40 (external edit)