Cryptococcus neoformans

Cryptococcus neoformans

Q. 1

Which of the following is only yeast ‑

 A

Candida

 B

Mucor

 C

Rhizopus

 D

Cryptococcus

Q. 1

Which of the following is only yeast ‑

 A

Candida

 B

Mucor

 C

Rhizopus

 D

Cryptococcus

Ans. D

Explanation:

Ans. is d i.e., Cryptococcus


Q. 2

Which is false regarding cryptococcus neoformans‑

 A

Grows at 5°C and 37°C

 B

It has 4 serotypes

 C

Urease negative

 D

Causes superficial skin infection

Q. 2

Which is false regarding cryptococcus neoformans‑

 A

Grows at 5°C and 37°C

 B

It has 4 serotypes

 C

Urease negative

 D

Causes superficial skin infection

Ans. C

Explanation:

Ans. is ‘c’ i e., Urease negative

Cryptococcus neoformans is distinguished from other non-pathogenic crvptococci by ‑

– Ability to grow at 37°C

Lack of fermentative ability

–   Ability to hydrolyze urease (urease positive)

–   Formation of brown pigment on niger seed agar

–   Ability to assimilate inositol

Ability to produce phenole oxidase.


Q. 3

Phagocytosis of C.neoformans is inhibited by ‑

 A

Cryptococcal capsular material

 B

The size of the yeast cells

 C

The cells walls

 D

Toxins produced by the organism

Q. 3

Phagocytosis of C.neoformans is inhibited by ‑

 A

Cryptococcal capsular material

 B

The size of the yeast cells

 C

The cells walls

 D

Toxins produced by the organism

Ans. A

Explanation:

Ans. is ‘a’ i.e., Cryptococcal Capsular material

Virulence factor of cryptococcus neoformans

  1. Polysaccharide capsule             –>          Inhibits phagocytosis by WBC
  2. Melanin production                    —>         Due to enzyme phenolic oxidase

Q. 4

Cryptococcus has predilection for –

 A

Lungs

 B

Meninges

 C

Liver

 D

a and b

Q. 4

Cryptococcus has predilection for –

 A

Lungs

 B

Meninges

 C

Liver

 D

a and b

Ans. D

Explanation:

Ans. is ‘a’ i.e., Lungs; ‘b’ i.e., Meninges

  • Self limiting pulmonary infection is most common form of cryptococcosis.
  • Most patients present with meningoencephalitis.

Q. 5

Eucalyptus camaldulensis is associated with the transmission of –

 A

Blastomyces dematitidis

 B

Histoplasma

 C

Cryptococcus

 D

Coccidioides immitis

Q. 5

Eucalyptus camaldulensis is associated with the transmission of –

 A

Blastomyces dematitidis

 B

Histoplasma

 C

Cryptococcus

 D

Coccidioides immitis

Ans. C

Explanation:

Ans. is ‘c’ i.e., Cryptococcus

  • C. neoformans has been isolated from the litter around trees of the species Eucalyptus camaldulensis and E. tereticornis.
  • Eucalyptus isolates belong to serotype B.

Q. 6

Cryptococcus-neoformans is a –

 A

Protozoa

 B

Fungus

 C

Parasite

 D

Mycoplasma

Q. 6

Cryptococcus-neoformans is a –

 A

Protozoa

 B

Fungus

 C

Parasite

 D

Mycoplasma

Ans. B

Explanation:

Ans. is ‘b’ i.e., Fungus


Q. 7

All are true about cryptococcus except

 A

Polysaccharide capsule

 B

Reproduces by budding

 C

Pseudohyphae

 D

All

Q. 7

All are true about cryptococcus except

 A

Polysaccharide capsule

 B

Reproduces by budding

 C

Pseudohyphae

 D

All

Ans. C

Explanation:

Ans. is ‘c’ i.e., Pseudohyphae;

  • Cryptococcus is a yeast, it does not form mycelium or pseudomycelium.
  • Pseudomycelium is formed by yeast like fungi eg, candida.
  • True mycelia are formed by moulds or filamentous fungi eg : dermatophytes.

About other options

  • Cryptococcus has polysaccharide capsule.
  • It reproduces by simple budding.

Q. 8

All of the following are true regarding Cryptococcus neoformans except: 

September 2008

 A

Affects immuocompromised patients

 B

Grown on sabouraud’s agar

 C

Capsular antigen can be detected in the CSF

 D

Anticapsular antibody is protective

Q. 8

All of the following are true regarding Cryptococcus neoformans except: 

September 2008

 A

Affects immuocompromised patients

 B

Grown on sabouraud’s agar

 C

Capsular antigen can be detected in the CSF

 D

Anticapsular antibody is protective

Ans. D

Explanation:

Ans. D: Anticapsular antibody is protective

C neoformans reproduces by budding and forms round yeast like cells that are 3-6 um in diameter.

Within the host and in certain culture media, a large polysaccharide capsule surrounds each cell.

C neoformans forms smooth, convex, yellow or tan colonies on solid media at 20-37°C (68-98.6°F).

This fungus is identified based on its microscopic appearance, biochemical test results, and ability to grow at 37°C (98.6°F); most nonpathogenic Cryptococcus strains do not grow at this temperature.

In addition, C. neoformans does not assimilate lactose and nitrates or produce pseudomycelia on cornmeal or rice-Tween agar.

Most infections with C. neoformans consist of a lung infection.However, fungal meningitis, especially as a secondary infection for AIDS patients, is often caused by C. neoformans making it a particularly dangerous fungus. Infections with this fungus are rare in those with fully functioning immune systems

Blood and CSF should be cultured for fungi and submitted for cryptococcal antigen testing whenever CNS infection is suspected.

Colonies on Sabouraud dextrose agar at 25°C are cream to beige and mucoid due to the capsule surrounding the yeast cells.


Q. 9

True about Cryptococcus neoformans are all except:

September 2005

 A

Possess a prominent polysaccharide capsule

 B

Abundant in pigeon droppings

 C

Dimorphic fungi

 D

Causes meningitis in the immunocompromised

Q. 9

True about Cryptococcus neoformans are all except:

September 2005

 A

Possess a prominent polysaccharide capsule

 B

Abundant in pigeon droppings

 C

Dimorphic fungi

 D

Causes meningitis in the immunocompromised

Ans. C

Explanation:

Ans. C: Dimorphic fungi

Cryptococcus is yeast/unicellular fungi.

C neoformans is distributed worldwide. C neoformans, which is recovered from aged pigeon feces, bird nests, and guano, is invariably serotype A or D. Although serotypes A and D exist in high concentrations in the pigeon feces, the fungus does not infect the birds.

In moist or desiccated pigeon excreta, C neoformans may remain viable for 2 years or longer.

In saprobic environments, C neoformans grows unencapsulated; however, unencapsulated strains regain their virulence following reacquisition of their polysaccharide capsule.

Cryptococcal meningitis is the most serious type of infection and can resemble tuberculous or other chronic type of meningitis. It is often seen in AIDS.



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