Corynebacterium diphtheriae 1285803 220081661 2008-06-18T05:11:43Z Optigan13 3457187 Corynebacterium_diphtheriae-02.jpg (copyvio) -> Corynebacterium diphtheriae Gram stain.jpg (free) {{Taxobox | color = lightgrey | name = ''Corynebacterium diphtheriae'' | image = Corynebacterium diphtheriae Gram stain.jpg | image_width = 200px | image_caption = [[Gram stain]]ed ''Corynebacterium diphtheriae'' culture | regnum = [[Bacterium|Bacteria]] | phylum = [[Actinobacteria]] | class = [[Actionomycetales]] | ordo = [[Actinomycetales]] | familia = [[Corynebacteriaceae]] | genus = ''[[Corynebacterium]]'' | species = '''''C. diphtheriae''''' | binomial = ''Corynebacterium diphtheriae'' | binomial_authority = Kruse, 1886 }} '''''Corynebacterium diphtheriae''''' is a pathogenic [[bacterium]] that causes [[diphtheria]]. It is also known as the '''Klebs-Löffler bacillus''', because it was discovered in [[1884]] by [[Germany|German]] [[Bacteriology|bacteriologists]] [[Edwin Klebs]] (1834 &ndash; 1912) and [[Friedrich Löffler]] (1852 &ndash; 1915). ==Morphology and toxin production== ''C. diphtheriae'' is a [[Facultative aerobic organism|facultatively aerobic]] <ref>[http://www.phac-aspc.gc.ca/msds-ftss/msds42e.html Corynebacterium diphtheriae - Material Safety Data Sheets (MSDS)<!-- Bot generated title -->]</ref> [[Gram positive]] organism, characterized by non-encapsulated, non-sporulated, immobile, straight or curved rods with a length of 1 to 8 µm and width of 0.3 to 0.8 µm, which form [[ramified]] aggregations in culture (looking like "Chinese characters"). The bacterium may contain polymetaphosphate aggregates called Volutin granules. It is pathogenic only in humans. ''C. diphtheriae'' produce [[diphtheria toxin]], a [[protein|proteic]] [[exotoxin]], with a molecular weight of 62 [[Dalton (unit)|kilodaltons]] which ADP-ribosylates host [[Elongation factor|EF-2]], resulting in the inhibition of protein synthesis and thus is responsible for the signs of diphtheria. The inactivation of this toxin with an antitoxic serum ([[antitoxin]]) is the basis of the antidiphtheric therapeutic [[vaccination]]. However, not all strains are toxigenic; the ability to produce the exotoxin is conferred on the bacterium when it is infected by a [[bacteriophage]] (a mechanism termed "lysogenic activation"). A non-toxigenic strain can thus become toxigenic by the infection of such a bacteriophage. ==Classification== Four subspecies are recognized: ''C. diphtheriae mitischodis'', ''C. diphtheriae intermedius'', ''C. diphtheriae gravis'', and ''C. diphtheriae belfanti''. The four subspecies differ slightly in their colonial morphology and biochemical properties such as the ability to metabolize certain nutrients, but all may be toxigenic (and therefore cause diphtheria) or non-toxigenic. ==Diagnosis== In order to accurately identify ''C. diphtheriae'', a [[Gram stain]] is performed to show gram-positive, highly pleomorphic organisms with no particular arrangement (classically resembling [[Chinese character]]s). Then, culture the organism on an erichment medium, namely Löffler's serum, to allow it to overgrow any other organisms present in the specimen. After that, use a selective plate known as [[tellurite agar]] which allows all ''Corynebacteria'' (including ''C. diphtheriae'') to reduce tellurite to metallic tellurium producing brown colonies and, only in the case of ''C. diphtheriae'', a black halo around the colonies allowing for easy differentation of the organism. A low concentration of iron is required in the medium for toxin production. At high iron concentrations, iron molecules bind to an aporepressor on the beta [[bacteriophage]] which carries the genes for the Tox gene, converting it to a [[repressor]] which shuts down toxin production<ref>Microbiology: A Human Perspective. Fourth edition. McGraw Hill</ref>. This is most appreciated when performing [[Elek's test]] for toxogenecity, in order to know if the organism is able to produce the diphtheria toxin or not. ==Sensitivity== The bacterium is sensitive to the majority of [[antibiotics]], such as the [[penicillin]]s, [[ampicillin]], [[cephalosporin]]s, [[quinolone]]s, [[chloramphenicol]], [[tetracycline]]s, [[cefuroxime]] and [[trimethoprim]]. ==References== {{reflist}} ==External links== * [https://www.cebitec.uni-bielefeld.de/groups/gi/software/coryneregnet/ CoryneRegNet] - Database of Corynebacterial Transcription Factors and Regulatory Networks'' [[Category:Corynebacterineae]] [[de:Corynebacterium diphtheriae]] [[es:Corynebacterium diphtheriae]] [[fr:Corynebacterium diphtheriae]] [[id:Corynebacterium diphtheriae]] [[it:Corynebacterium diphtheriae]] [[nl:Corynebacterium diphtheriae]] [[pl:Maczugowiec błonicy]] [[ro:Corynebacterium diphtheriae]] [[fi:Corynebacterium diphtheriae]] [[tr:Corynebacterium diphtheriae]]