Corynebacterium diphtheriae: Difference between revisions
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==Pathophysiology== | ==Pathophysiology== | ||
*''C.diphtheriae'' causes [[diphtheria]] disease in non-immunized human hosts via secreted toxins.<ref name="pmid21413281">{{cite journal |vauthors=Baron S, Murphy JR |title=Medical Microbiology |journal= |volume=4 |issue= |pages= |year=1996 |pmid=21413281 |doi= |url=}}</ref><ref name="pmid106070"> | *''C.diphtheriae'' causes [[diphtheria]] disease in non-immunized human hosts via secreted toxins.<ref name="pmid21413281">{{cite journal |vauthors=Baron S, Murphy JR |title=Medical Microbiology |journal= |volume=4 |issue= |pages= |year=1996 |pmid=21413281 |doi= |url=}}</ref><ref name="pmid106070"></ref> | ||
**Toxigenic strains of the [[bacterium]] will secrete toxins in [[nasopharyngeal]] or skin [[lesions]]; it is common for hosts to carry ''C. diphtheriae'' in the [[nasopharyngeal]] region without displaying symptoms. | **Toxigenic strains of the [[bacterium]] will secrete toxins in [[nasopharyngeal]] or skin [[lesions]]; it is common for hosts to carry ''C. diphtheriae'' in the [[nasopharyngeal]] region without displaying symptoms. | ||
**A low concentration of iron is required in the medium for toxin production; at high iron concentrations, iron molecules bind to a [[repressor]] which shuts down toxin production<ref>{{cite book |last=Nester |first=Eugene W. |year=2004 |title=Microbiology: A Human Perspective |edition=Fourth |location=Boston |publisher=McGraw-Hill |isbn=0-07-247382-7 |display-authors=etal}}</ref> | **A low concentration of iron is required in the medium for toxin production; at high iron concentrations, iron molecules bind to a [[repressor]] which shuts down toxin production<ref>{{cite book |last=Nester |first=Eugene W. |year=2004 |title=Microbiology: A Human Perspective |edition=Fourth |location=Boston |publisher=McGraw-Hill |isbn=0-07-247382-7 |display-authors=etal}}</ref> | ||
Revision as of 15:56, 13 October 2016
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Luke Rusowicz-Orazem, B.S.
| 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 a facultatively anaerobic, Gram positive organism, characterized by non-encapsulated, non-sporulated, immobile, straight or curved rods. The genome of C. diphtheriae contains 2,488,635 nucleotides, 2,389 genes, and 69 structural RNA genes. 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, resulting in the inhibition of protein synthesis and producing signs of diphtheria. C. diptheriae is exclusively pathogenic in humans. C. diphtheriae can be classified into following four subspecies: mitis, intermedius, gravis, and belfanti. Diagnosis ofC. diphtheriae includes a Gram stain procedure; results will indicate gram-positive, pleomorphic bacteria that will dye violet-blue and resemble clubs. C.diphtheriae causes diphtheria disease in non-immunized human hosts via secreted toxins. Toxigenic strains of the bacterium will secrete toxins in nasopharyngeal or skin lesions; it is common for hosts to carry C. diphtheriae in the nasopharyngeal region without displaying symptoms. Lysogenic conversion of nontoxigenic-toxigenic phenotypes of the bacterium can occur following transmission, allowing non-human/affected hosts to transmit diphtheria to humans. C. diphtheriae is sensitive to antibiotic therapy.
Morphology and Structure
- C. diphtheriae is a facultatively anaerobic, Gram positive organism, characterized by non-encapsulated, non-sporulated, immobile, straight or curved rods.[1][2]
- The genome of C. diphtheriae contains 2,488,635 nucleotides, 2,389 genes, and 69 structural RNA genes.[3]
- As a gram-positive bacteria, C. diphtheriae contains a cell membrane and a lipid-rich murein layer outside.
- 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, resulting in the inhibition of protein synthesis and producing signs of diphtheria.[4]
- 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.
- C. diptheriae is exclusively pathogenic in humans.[5]
Classification
C. diphtheriae can be classified into the following four subspecies:[1][2]
- C. diphtheriae mitis
- C. diphtheriae intermedius
- C. diphtheriae gravis
- C. diphtheriea belfanti[6]
Diagnosis
- Diagnosis ofC. diphtheriae includes a Gram stain procedure.
- Results will indicate gram-positive, pleomorphic bacteria that will dye violet-blue and resemble clubs.[6]
- Additional tests include Albert's stain and Loeffler's stain.
- C. diphtheriae should be cultured on an erichment medium, namely to allow it to overgrow any other organisms present in the specimen.[7]
- A selective plate tellurite agar which allows all Corynebacteria (including C. diphtheriae) to reduce tellurite to metallic tellurium and produce brown colonies
- C. diphtheriae is the only corynebacterium that will produce a black halo around the colonies.
- A selective plate tellurite agar which allows all Corynebacteria (including C. diphtheriae) to reduce tellurite to metallic tellurium and produce brown colonies
Pathophysiology
- C.diphtheriae causes diphtheria disease in non-immunized human hosts via secreted toxins.[1][2]
- Toxigenic strains of the bacterium will secrete toxins in nasopharyngeal or skin lesions; it is common for hosts to carry C. diphtheriae in the nasopharyngeal region without displaying symptoms.
- A low concentration of iron is required in the medium for toxin production; at high iron concentrations, iron molecules bind to a repressor which shuts down toxin production[8]
- C.diphtheriae is transmitted through respiratory droplets, secretions, or direct contact.
- Lysogenic conversion of nontoxigenic-toxigenic phenotypes of the bacterium can occur following transmission, allowing non-human/affected hosts to transmit diphtheria to humans.
Sensitivity
C. diphtheriae is sensitive to the following antibiotics:[9]
- Benzylpenicillin
- Ampicillin
- Oxytetracycline
- Erythromycin
- Cephaloradine
- Lincomycin
- Clindamycin
- Neomycin
External links
- CoryneRegNet - Database of Corynebacterial Transcription Factors and Regulatory Networks
References
- ↑ 1.0 1.1 1.2 Baron S, Murphy JR (1996). "Medical Microbiology". 4. PMID 21413281.
- ↑ 2.0 2.1 2.2 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.
- ↑ Cerdeno-Tarraga, A. M. (2003). "The complete genome sequence and analysis of Corynebacterium diphtheriae NCTC13129". Nucleic Acids Research. 31 (22): 6516–6523. doi:10.1093/nar/gkg874. ISSN 1362-4962.
- ↑ Nester, Eugene W.; et al. (2004). Microbiology: A Human Perspective (Fourth ed.). Boston: McGraw-Hill. ISBN 0-07-247382-7.
- ↑ von Behring E, Kitasato S (1991). "[The mechanism of diphtheria immunity and tetanus immunity in animals. 1890]". Mol. Immunol. (in German). 28 (12): 1317, 1319–20. PMID 1749380.
- ↑ 6.0 6.1 "Pinkbook | Diphtheria | Epidemiology of Vaccine Preventable Diseases | CDC".
- ↑ Nester, Eugene W.; et al. (2004). Microbiology: A Human Perspective (Fourth ed.). Boston: McGraw-Hill. ISBN 0-07-247382-7.
- ↑ Nester, Eugene W.; et al. (2004). Microbiology: A Human Perspective (Fourth ed.). Boston: McGraw-Hill. ISBN 0-07-247382-7.
- ↑ Zamiri I, McEntegart MG (1972). "The sensitivity of diphtheria bacilli to eight antibiotics". J. Clin. Pathol. 25 (8): 716–7. PMC 477485. PMID 4627747.