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 German bacteriologists Edwin Klebs (1834 – 1912) and Friedrich Löffler (1852 – 1915). Image File history File links A photomicrograph of Corynebacterium diphtheriae bacteria using a Gram stain technique. ... Gram staining is a method for staining samples of bacteria that differentiates between the two main types of bacterial cell wall. ... For other uses, see Scientific classification (disambiguation). ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Subclasses Acidimicrobidae Actinobacteridae Coriobacteridae Rubrobacteridae Sphaerobacteridae The Actinobacteria or Actinomycetes are a group of Gram-positive bacteria. ... Suborders Actinomycineae Corynebacterineae Frankineae Glycomycineae Micrococcineae Micromonosporineae Propionibacterineae Pseudonocardineae Streptomycineae Streptosporangineae Actinomycetales is an order of Actinobacteria. ... Binomial name Corynebacterium diphtheriae Corynebacterium diphtheriae is a pathogenic bacterium that causes diphtheria. ... Species See text. ... This article does not cite any references or sources. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Year 1884 (MDCCCLXXXIV) was a leap year starting on Tuesday (link will display the full calendar) of the Gregorian calendar (or a leap year starting on Sunday of the 12-day-slower Julian calendar). ... Microbiology (in Greek micron = small and biologia = studying life) is the study of microorganisms, including unicellular (single-celled) eukaryotes and prokaryotes, fungi, and viruses. ... Edwin Klebs (1834–1913) was a German pathologist. ... Friedrich August Johannes Löffler (1852 - 1915) was a German bacteriologist and Nobel laureate at the Ernst Moritz Arndt University of Greifswald. ...

Morphology and toxin production

C. diphtheriae is a facultatively anaerobic ^[1] 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. A facultative anaerobic organism is an organism, usually a bacterium, that makes ATP by aerobic respiration if oxygen is present but is also capable of switching to fermentation under anaerobic conditions. ... Gram-positive Bacillus anthracis bacteria (purple rods) in cerebrospinal fluid sample. ... In mathematics, ramification is a geometric term used for branching out, in the way that the square root function, for complex numbers, can be seen to have two branches differing in sign. ...

Many strains of C. diphtheriae produce diphtheria toxin, a proteic exotoxin, with a molecular weight of 62 kilodaltons which ADP-ribosylates host EF-2, which results 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 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. Diphtheria toxin is an exotoxin secreted by Corynebacterium diphtheriae, the pathogen bacterium that causes diphtheria. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... An exotoxin is a soluble chemical excreted by a microorganism, including bacteria, fungi, algae, and protozoa. ... The unified atomic mass unit (u), or dalton (Da), is a small unit of mass used to express atomic masses and molecular masses. ... Elongation factors are a set of proteins that facilitate the events of translational elongation, the steps in protein synthesis from the formation of the first peptide bond to the formation of the last one. ... An antitoxin is an antibody with the ability to neutralize a specific toxin. ... A vial of the vaccine against influenza. ... An artists rendering of an Enterobacteria phage T4. ...

Classification

Three subspecies are recognized: C. diphtheriae mitis, C. diphtheriae intermedius, and C. diphtheriae gravis. The three subspecies differ slightly in their 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 characters). 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. Gram staining is a method for staining samples of bacteria that differentiates between the two main types of bacterial cell wall. ... Japanese name Kanji: Hiragana: Korean name Hangul: Hanja: Vietnamese name Quốc ngữ: Hán tá»±: A Chinese character or Han character (simplified Chinese: ; traditional Chinese: ; pinyin: ) is a logogram used in writing Chinese, Japanese, sometimes Korean, and formerly Vietnamese. ...

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^[2]. 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. A repressor is a DNA-binding protein that regulates the expression of one or more genes by decreasing the rate of transcription. ...

Sensitivity

The bacterium is sensitive to the majority of antibiotics, such as the penicillins, ampicillin, cephalosporins, quinolones, chloramphenicol, tetracyclines, cefuroxime and trimethoprim. An antibiotic is a drug that kills or slows the growth of bacteria. ... For the Japanese rock band, see Penicillin (band). ... Ampicillin is a beta-lactam antibiotic that has been used extensively to treat bacterial infections since 1961. ... The cephalosporins, are a class of β-lactam antibiotics. ... Nalidixic acid Ciprofloxacin Levofloxacin Trovafloxacin The quinolones are a family of broad-spectrum antibiotics. ... Chloramphenicol is a bacteriostatic antibiotic originally derived from the bacterium Streptomyces venezuelae, isolated by David Gottlieb, and introduced into clinical practice in 1949. ... Tetracycline (INN) (IPA: ) is a broad-spectrum antibiotic produced by the streptomyces bacterium, indicated for use against many bacterial infections. ... Cefuroxime is a second-generation cephalosporin antibiotic that has been widely available in the USA since 1977. ... Trimethoprim is a bacteriostatic antibiotic mainly used in the prophylaxis and treatment of urinary tract infections (cystitis). ...

References

1. ^ http://www.phac-aspc.gc.ca/msds-ftss/msds42e.html
2. ^ Microbiology: A Human Perspective. Fourth edition. McGraw Hill

External links

• CoryneRegNet - Database of Corynebacterial Transcription Factors and Regulatory Networks