Sandbox:Corynebacterium diphtheriae
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];
| Corynebacterium diphtheriae | ||||||||||||
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 Gram stained Corynebacterium diphtheriae culture
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| Corynebacterium diphtheriae Kruse, 1886 |
Overview
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 bacteriologists Edwin Klebs (1834 – 1912) and Friedrich Löffler (1852 – 1915).
Morphology and Structure
- C. diphtheriae is a facultatively anaerobic, Gram positive organism, characterized by non-encapsulated, non-sporulated, immobile, straight or curved rods.[1]
- Cell wall sugars of C. diphtheriae include arabinose, galactose, and mannose.
- Gram-stain will result in a blue-purple coloration due to containing polymetaphosphate granules.
- Many strains of C. diphtheriae produce diphtheria toxin, a protein exotoxin, with a molecular weight of 62 kilodaltons which ADP-ribosylates host EF-2, which results in the inhibition of protein synthesis and is responsible for the signs of diphtheria.[2]
- The inactivation of this toxin with an antitoxic serum (antitoxin) is the basis of the antidiphtheric vaccination.
- Not all strains are toxigenic; the ability to produce the exotoxin is conferred on the bacterium when it is infected by a bacteriophage through a mechanism termed lysogenic activation.
- A non-toxigenic strain can become toxigenic by the infection of such a bacteriophage.
- The inactivation of this toxin with an antitoxic serum (antitoxin) is the basis of the antidiphtheric vaccination.
Classification
C. diphtheriea can be classified into the following three subspecies:[1][3]
- C. diphtheriae mitis
- C. diphtheriae intermedius
- C. diphtheriae gravis
- C. diphtheriea belfanti[4]
Diagnosis
- Diagnosis ofC. diphtheriae includes a Gram stain procedure.
- Results will indicate gram-positive, pleomorphic bacteria that will dye violet-blue, club-shaped resembling Chinese characters.[4]
Then, culture the organism on an erichment medium, namely , 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.
It's worth noting that a low concentration of iron is required in the medium for toxin production; as at high iron concentrations, iron molecules bind to a repressor which shuts down toxin production[5]. 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 penicillins, ampicillin, cephalosporins, quinolones, chloramphenicol, tetracyclines, cefuroxime and trimethoprim.
Genetics
The genome of C. diphtheriae consists of a single circular chromosome of 2,5 Mbp, with no plasmids.[6][7]
References
- ↑ 1.0 1.1 Baron S, Murphy JR. PMID 21413281. Missing or empty
|title=(help) - ↑ Nester, Eugene W.; et al. (2004). Microbiology: A Human Perspective (Fourth ed.). Boston: McGraw-Hill. ISBN 0-07-247382-7.
- ↑ Chang DN, Laughren GS, Chalvardjian NE (1978). "Three variants of Corynebacterium diphtheriae subsp. mitis (Belfanti) isolated from a throat specimen". J. Clin. Microbiol. 8 (6): 767–8. PMC 275340. PMID 106070.
- ↑ 4.0 4.1 "Pinkbook | Diphtheria | Epidemiology of Vaccine Preventable Diseases | CDC".
- ↑ Microbiology: A Human Perspective. Fourth edition. McGraw Hill
- ↑ Cerdeño-Tárraga AM, Efstratiou A, Dover LG, Holden MT, Pallen M, Bentley SD; et al. (2003). "The complete genome sequence and analysis of Corynebacterium diphtheriae NCTC13129". Nucleic Acids Res. 31 (22): 6516–23. PMC 275568. PMID 14602910.
- ↑ Sangal V, Tucker NP, Burkovski A, Hoskisson PA (2012). "The draft genome sequence of Corynebacterium diphtheriae bv. mitis NCTC 3529 reveals significant diversity between the primary disease-causing biovars". J Bacteriol. 194 (12): 3269. doi:10.1128/JB.00503-12. PMC 3370853. PMID 22628502.
External links
- CoryneRegNet - Database of Corynebacterial Transcription Factors and Regulatory Networks