what media does corynebacterium diphtheriae grow on

Full Answer

What is the best culture medium for Corynebacterium diphtheriae?

An enrichment medium, such as Löffler's medium, is used to preferentially grow C. diphtheriae. After that, a differential plate known as tellurite agar, allows all Corynebacteria (including C. diphtheriae) to reduce tellurite to metallic tellurium.

Which Corynebacterium causes diphtheria?

In addition to C. diphtheriae, two other corynebacteria species can produce diphtheria toxin and thus also cause diphtheria: C. ulcerans and very rarely C. pseudotuberculosis . There are two types of clinical diphtheria: nasopharyngeal (respiratory) and cutaneous.

What are the portals of entry for Corynebacterium diphtheriae?

The portals of entry for Corynebacterium diphtheriae are the nose, tonsils, and throat. Diseased individuals may experience a sore throat, overall weakness, fever, and swollen glands. Diphtheria is transmitted from human contact through respiratory droplets, such as coughing or sneezing.

Does Corynebacterium diphtheriae grow on MacConkey Agar?

The presence of coryneform organisms in smears is diagnostic. Culture on blood agar, selective blood agar and MacConkey agar are also diagnostic, they do not grow on MacConkey.

What media does Corynebacterium grow?

The best method for isolating and cultivating Corynebacteria is to use sheep blood agar plus one selective medium as the primary plating media. Selective media commonly used are Cystine-Tellurite blood agar or Tinsdale medium.

Which cultivation media is used for cultivation of Corynebacterium diphtheriae?

For primary isolation, a variety of media may be used: Loeffler agar, Mueller-Miller tellurite agar, or Tinsdale tellurite agar.

What Agar does Corynebacterium grow on?

Serum Tellurite Agar is a selective and differential medium primarily used for the isolation and detection of Corynebacterium diphtheriae.

Is Corynebacterium diphtheriae Gram-positive?

C. diphtheriae is a pleomorphic, club-shaped, Gram positive bacillus that is catalase positive, non-motile, non-spore forming, and non-acid fast. On Gram stain, the organisms are typically described as having a “picket fence” or “Chinese character” morphology (image 3).

What are the recommended specimens for the laboratory diagnosis of diphtheria?

Doctors usually decide if a person has diphtheria by looking for common signs and symptoms. They can swab the back of the throat or nose and test it for the bacteria that cause diphtheria. A doctor can also take a sample from an open sore or ulcer and try and grow the bacteria.

Which selective medium is used for isolation of Corynebacterium diphtheriae?

If diphtheria is suspected, Loeffler's serum slope and Potassium tellurite agar, Blood tellurite agar (Hoyle's agar/McLeod's agar) or Tinsdale agar should be used. The culture plates should be inoculated at 37oC for 24-48 hours. Selective media may be incubated for 48 hours.

What grows on Loeffler media?

History. In 1887, Friedrich Loeffler devised a culture medium containing horse serum, meat infusion, and dextrose for use in the cultivation of corynebacteria and for differentiating them from other organisms. Perry and Petran suggested modification of the original formulation.

What is tinsdale agar used for?

Tinsdale Agar is used for selective isolation and differentiation of Corynebacterium diphtheriae and it is Gram-positive, facultatively anaerobic, non-motile bacteria that exhibit a fermentative metabolism (carbohydrates to lactic acid) under certain conditions.

Which medium offers a better growth for Corynebacterium diphtheriae?

diphtheriae grows well on blood agar, but tellurite blood agar (Hoyle's medium) is recommended as this inhibits other respiratory flora and allows the characteristic colonial morphology of the three biotypes (gravis, intermedius and mitis) to develop.

What is tellurite medium?

Tellurite Blood Agar is a selective medium used for isolation and cultivation of Corynebacterium species (1, 2). It is selective due to the presence of inhibitor and differential by means of ability of organism to reduce potassium tellurite. Biopeptone provides nitrogenous compounds.

What is differential medium?

Differential media contain compounds that allow groups of microorganisms to be visually distinguished by the appearance of the colony or the surrounding media, usually on the basis of some biochemical difference between the two groups.

What did Roux and Yersin show about diphtheria?

By 1888, Roux and Yersin showed that animals injected with sterile filtrates of C diphtheriae developed organ pathology indistinguishable from that of human diphtheria; this demonstrated that a potent exotoxin was the major virulence factor. Diphtheria is a paradigm of the toxigenic infectious diseases.

What was the name of the organism that was discovered in 1883?

In 1883, Klebs demonstrated that Corynebacterium diphtheriae was the agent of diphtheria. One year later, Loeffler found that the organism could only be cultured from the nasopharyngeal cavity, and postulated that the damage to internal organs resulted from a soluble toxin.

What is the name of the parasite that is a paradigm of the toxigenic infectious diseases?

Corynebacterium Diphtheriae - Medical Microbiology - NCBI Bookshelf. Diph theria is a paradigm of the toxigenic infectious diseases. In 1883, Klebs demonstrated that Corynebacterium diphtheriae was the agent of diphtheria.

What is the cause of Corynebacterium diphtheriae?

Corynebacterium diphtheriae causes several forms of clinical disease, including membran ous nasopharyngitis, obstructive laryngotracheitis, and cutaneous infection. Complications can include airway obstruction from membrane formation and toxin-mediated central nervous system (CNS) disease or myocarditis. The overall incidence of diphtheria has declined even though immunization does not prevent infection but does prevent severe disease from toxin production. Fewer than five cases are reported annually in the United States.

What is the biotype of C. diphtheriae?

Corynebacterium diphtheriae is the etiologic agent of human respiratory and cutaneous diphtheria. There are 3 biotypes (mitis, gravis, and intermedius) of C. diphtheriae, each differentiated by hemolysis, colonial morphology, and fermentative reactions. Diagnosis is made by identifying the microorganism in cultures from swabs of the nasopharynx or skin lesions. The specimens can be plated on Löeffler's or cysteine tellurite agar media. Isolates are tested for toxin production by the Elek test, cell culture neutralization assay or inoculation into guinea pigs. In general, rodents are not susceptible since they do not have cell membrane receptors for diphtheria toxin. On rare occasions other Corynebacterium species may cause diseases, mainly nosocomial (hospital-acquired) infections ( Knox and Holmes, 2002 ).

What is a diphtheriae?

Corynebacterium diphtheriae is a slender, Gram-positive bacillus, usually with one end being wider, thus giving the often-described club-shaped appearance. On culture, particularly under suboptimal conditions, characteristic bands or granules appear. On smear, the organisms often have a “pick-up sticks” relationship, assuming parallel (palisade-like), or V- or L-type patterns. The organisms are resistant to environmental changes, such as freezing and drying. There are four biotypes of C. diphtheriae (gravis, mitis, belfanti, and intermedius), which historically were identified by colonial morphology and biochemical differences; however, in practice, only the intermedius biotype can be distinguished reliably by colonial morphology. 39 No consistent differences are found in severity of disease caused by different biotypes. Biotype differentiation is not supported by phylogenetic analyses.40

How are isolates tested for toxin production?

Isolates are tested for toxin production by the Elek test, cell culture neutralization assay or inoculation into guinea pigs. In general, rodents are not susceptible since they do not have cell membrane receptors for diphtheria toxin.

How long does it take to cure C. diphtheriae?

Treatment consists of cleansing the affected skin and administering systemic antibiotic therapy with penicillin or erythromycin for 10 to 14 days. 41,71 The use of antitoxin in addition to systemic antibiotics is controversial 41,69 because cutaneous lesions are nontoxigenic or produce only small amounts of toxin. 71 To document eradication of the organism, two negative culture results should be obtained after treatment concludes. 41

Which bacterium secretes a toxin that inhibits translation during protein synthesis by human cells?

Diphtheria. Corynebacterium diphtheriae is an aerobic gram-positive bacterium which secretes a toxin that inactivates human elongation factor eEF-2, thus inhibiting translation during protein synthesis by human cells. The site of infection, generally the throat, becomes sore and swollen.

Which bacteria produces cholera toxin?

Corynebacterium diphtheriae produces diphtheria toxin, which is responsible for the systemic pathology associated with diphtheria, whereas Vibrio cholerae produces cholera toxin, which is responsible for the diarrheal pathology associated with cholera.

What is the laboratory diagnosis of Corynebacterium diphtheriae?

Laboratory diagnosis of Corynebacterium diphtheriae involves isolation of the organism and subsequent demonstration of toxin production.

What medium stimulates C. diphtheriae?

on a selective and differential medium such as cystine-tellurite blood agar and modified Tinsdale’s medium. In addition, Loeffler’s medium , containing serum and eggs, stimulates the growth of C. diphtheriae and stimulates the production of metachromatic granules within the cells.

What is the color of a swab of throat?

Smears of the throat swab should be stained with both Gram stain and methylene blue or Albert stain. Appearance of many tapered, irregularly stained, pleomorphic (typically arranged in Chinese letter or cuneiform arrangements) gram-positive rods is suggestive of Corynebacterium diptheriae. Typical metachromatic granules are seen in methylene blue stain or in Albert stain. C. diphtheriae appears as green bacilli with bluish-black metachromatic granules in Albert stain.

How to identify C. diphtheriae?

Definitive identification of C. diphtheriae isolates as a true pathogen requires a demonstration of toxin production. The toxigenicity of C. diphtheriae strains is determined by a variety of in vitro and in vivo tests: 1 Elek immunodiffusion test: It is the most common in vitro assay for determining toxigenicity of C. diphtheriae. This test is based on the double diffusion of diphtheria toxin and antitoxin in an agar medium. A sterile, antitoxin-saturated filter paper strip is embedded in the culture medium, and C diphtheriae isolates are streak-inoculated at a 90° angle to the filter paper. The production of diphtheria toxin can be detected within 18 to 48 hours by the formation of a toxin-antitoxin precipitin band in the agar. 2 Detection of toxin gene by polymerase chain reaction (PCR). 3 Guinea pig lethality test

How long does it take for a C. diphtheriae colony to appear?

After 48-72 hours, colonies of C. diphtheriae appear as small, grey, or black with a raised center. Biotypes (gravis, intermedius, mitis, and belfanti) can be differentiated on the basis of colony morphology on tellurite blood agar and biochemical tests such as; Urease. Nitrate reduction. Esculin hydrolysis.

What is the Gram positive bacillus that causes diphtheria?

Last updated on June 21st, 2021. Characteristics Psuedomembrane of C. diphtheriae. Corynebacterium diphtheriae also known as Klebs-Löffler bacillus is a Gram-positive bacillus responsible for causing diphtheria. Once a major cause of illness and death among children, diphtheria became a rare disease after the administration of vaccination.

How long does it take for Tinsdale's agar to incubate?

Tinsdale’s Agar: After incubation for at least 48 hours, colonies of Corynebacterium diphtheriae appear black with dark brown halos.

Where does the term "diphtheria" come from?

The term “diphtheria“ is derived from the Greek word ‘diphtheria’ which means ‘hide or leather,’ owing to characteristics of pseudomembrane produced by the organism itself over the site of colonization.[1] .

How do bacteria get into the body?

The mode of transmission is via respiratory droplets or contact transmission from an infected host or their carrier. It can also be transmitted by direct contact with the objects or secretions previously in touch with the infected person and or its carrier. After gaining access to the host, the bacteria usually colonize in the upper respiratory tract. They typically do not invade tissue to cause disseminated bacteremia.

Why is pharyngitis contagious?

Viral etiology is the most common cause of pharyngitis due to its contagious origin. Diphtheria is one of the essential reasons for pharyngitis in non immunized and immunocompromised individuals, which can cause significant mortality and morbidity if remained untreated.

Where is necrotic membrane formation?

The most common location is usually in the tonsillar and the posterior pharyngeal wall. The extent of the layer can be co-related with morbidity and mortality as extensive membrane formation can compromise the airway leading to asphyxia and death.[10] Aspiration of this necrotic material can lead to aspiration pneumonia, which can further complicate the disease process. There is also sore throat and cervical lymphadenopathy (due to enlargement of the draining lymph node giving it an appearance of bull’s neck). [5]

Which gene encodes the synthesis of toxins?

The gene responsible for the synthesis of the toxin is encoded by corynebacteriophage, which, when integrated into the bacterial genome, can potentially transform the non-toxigenic strain into a virulent toxigenic strain.

Which gene is responsible for the production of toxins?

Although the bacteria get a toxin-producing gene from bacteriophage, however, its regulation is controlled by the bacteria. The diphtheria toxin repressor gene (DtxR) is present on the bacterial chromosome, and toxin production depends upon the expression of tox and bacterial iron metabolism.

Is the burden of disease worse than what is seen on paper?

It is to be noted that these are only the number of cases that were reported. Still, in general, the epidemiological burden of disease is far worse than what is seen on paper, mainly owing to a vast number of cases that remain under-reported, mostly in Asia, Africa, and Eastern Mediterranean countries.

What are the three strains of Corynebacterium diphtheriae?

Three strains of Corynebacterium diphtheriae are known, gravis , intermedius and mitis. They are listed here as the severity of the disease they produce in humans in decreasing order. The same toxin is produced by all strains and is capable of colonizing the throat.

Where does C. diphtheriae occur?

C. diphtheriae is preserved in the population as the asymptomatic carriage occurs in the oropharynx or on the skin of immune people.

What is the use of tellurite blood agar?

The introduction of potassium tellurite (0.03-0.04%) helps to make the medium selective for corynebacteria by suppressing most other pathogenic and commensal bacteria. C. diphtheriae exhibit gray/black, shiny or dull black colonies.

How many units of diphtheriae antibiotics are given?

The dosage suggested is 20,000 units intramuscularly for moderate cases and 50,000 to 100,000 units for severe cases, half the dose being given intravenously. Diphtheriae is susceptible to most antibiotics, including penicillin and erythromycin, and is used in both carriers and patients.

What is the disease caused by C. diphtheriae?

The main disease caused by C. diphtheriae is diphtheria. The Greek meaning of diphtheria refers to the leathery skin referring to the pseudo-membrane that is formed on the pharynx initially.

What is the most widely studied species of diphtheria?

Corynebacterium diphtheriae, the causal agent of the disease diphtheria, is the best known and most widely studied species. The diphtheria bacillus is also termed as Klebs-Loffler bacillus as it was first observed and explained by Klebs in 1883 and was first cultivated by Loffler in 1884.

What is the genus of corynebacteria?

A diverse community of bacteria, including animal and plant pathogens, as well as saprophytes, make up the genus Corynebacterium. Some of the corynebacteria are part of the normal human flora, particularly the skin and nares, that tends to find an appropriate niche in almost every anatomical location.

Overview

Classification

Four subspecies are recognized: C. d. mitis, C. d. intermedius, C. d. gravis, and C. d. 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 not toxigenic. C. diphtheriae produces diphtheria toxin which alters protein function in the host by inactivating the elongation factor EF-2. This causes pharyngitis and 'pseudomembrane' in the thr…

Pathogen and disease

Pathogenesis

Sensitivity

Genetics

See also

External links