Question Bank 4 -YEAST

A) Candida1. Yeasts are single-celled budding organisms, do not produce mycelia.2. Colonies of yeast are usually visible on the plates in 24-48 hours. Their soft,

moist colonies resemble bacterial cultures.

3. Candida is divided into two broad categories; albicans and non-albicans

species.

4. There are several species of the genus Candida that cause diseases, infections

caused by all species of Candida are called Candidiasis.

5. Candida albicans is an endogenous organism, found in 40-80% of normal

human beings.

6. Candida albicans is present in the mouth, gut, and vagina ,as a commensal or a pathogenic organism.

7. The establishment of candidial infection appears to be a property of the host - not the organism, more debilitated the host, the more invasive the disease.

8. Candidial Infections usually occur when a patient has some alteration in

cellular immunity, normal flora or normal physiology.

9. Prolonged antibiotic or steroid therapy destroys the balance of normal flora in

the intestine allowing the endogenous Candida to overcome the host.

10. Although Candida most frequently infects the skin and mucosae and can cause

pneumonia, septicemia, endocarditis, esophagitis, etc. in the compromised

patient.

11.The clinical material that is sent to the laboratory for Candidiasis depends on the

presentation of the disease: blood cultures, vaginal discharge, urine, feces, nail clippings or material from cutaneous or mucocutaneous lesions.

12.Candida is polymorphic yeast, i.e., yeast cells and pseudohyphae are

produced.

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Question Bank 4 -YEAST

13.

14.The yeast form is 10-12 microns in diameter, gram positive, and it grows in 2 or 3 days on most bacterial and fungal media.

Candida colony

Candida albicans

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Question Bank 4 -YEAST

15.Spores (chlamydospores) may be formed on the pseudomycelium which can

be used to identify different species of Candida.

16. chlamydospores of Candida17.Candida albicans (specifically) also produces germ tubes which serve as a key

to speciation.

18. Germ tube of Candida albicans

19.The drug of choice for vaginitis and cutaneous infections is nystatin (topical) and

those for systemic infections are itraconazole and fluconazole.

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Question Bank 4 -YEAST

B. CRYPTOCOCCOSIS (Cryptococcus neoformans) 1) Cryptococcosis manifests itself most commonly as meningitis but in recent

years pulmonary infections have been recognized.

2) Cryptococcosis Infections may be subacute or chronic,death usually occurs

due to cerebral edema and increased intracranial pressure.

3) .Capsule of Cryptococcus neoformans

4) C. neoformans is very distinctive yeast. The cells, which are spherical, and 5-

10 microns in diameter, produce buds that characteristically are narrow-based

and a polysaccharide capsule surrounds the organism.

5) Capsule of Cryptococccus neoformes

6) The polysaccharide capsule may suppress T-cell function and can be

considered a virulence factor. 7) C. neoformans also produces an enzyme called phenoloxidase (melanin)

which appears to be another virulence factor.

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Question Bank 4 -YEAST

8) The ecological niche of C. neoformans is pigeon and chicken droppings.

9) Infection and disease production is probably a property of the host--not the

organism.

10)The portal of entry of C. neoformans is the respiratory system,in addition to

causing meningitis, C. neoformans may occasionally infect lungs and skin.

11)The disease in the lungs and skin is characterized by the formation of a

granulomatous reaction with giant cells.

12)C.neoformans in lungs

13)In culture the C. neoformans grows as creamy, white, mucoid (because of the

capsule) colonies.

14)

15)C. neoformans growth in culture is usually visible in 24-48 hours, as the culture

ages, it turns brown due to a melanin produced by the phenoloxidase.

16)C. neoformans is a round, single cell, yeast surrounded by a capsule,species

identification is based on physiological reactions.

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Question Bank 4 -YEAST

17)Pathologists use a mucicarmine stain, which tints the capsule, to identify the

organism in tissue sections.

18)

19)

20)The Direct Fluorescent Antibody test identifies the organism in culture or tissue

section specifically, by causing the yeast cell wall to fluoresce green.

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Cryptococcosis ,mucramine stain

Cryptococcosis of lung in patient Methenamine silver stain.

Question Bank 4 -YEAST

21)To test the patient's serum for the presence of C. neoformans there are 3

serologic tests:

The Indirect Fluorescent Antibody test, The Tube Agglutination test for antibody, Latex Agglutination test for antigen.

22).The drugs of choice to treat cryptococcus infection are amphotericin B plus 5-

flucytosine (5-FC) or amphotericin plus fluconazole.

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