Mycology III- Opportunistic Fungi III

Question 1

1. Identify the ecological niches, environmental and pathogenic tissue forms and discuss epidemiology, diagnosis and treatment for Candida albicans.

Answer 1

commensual part of the normal microbiota, particularly of moist areas

pathologic skin, nail and mucosal infection

dimorphic; yeast commensal; hyphal forms invade (includes hyphae, pseudohyphae and germ tubes)
C. glabrata shows only yeast form

Question 2

1. Identify the ecological niches, environmental and pathogenic tissue forms and discuss treatment for Aspergillus species.

Answer 2

ubiquitous in the environment worldwide; airborne exposure is very common

mold only (no yeast) causing

tx. high-dose amphotericin B, voriconazol DOC in combo with echinocandin

Question 3

1. Identify the ecological niches, environmental and pathogenic tissue forms of Pneumocystis jiroveci.

Answer 3

trophozoites in hosts (may resemble cell debris) and cysts (larger and highly refractive) that meiotic division within cyst wall

presumed environmental exposure is common and that the route of of infection is respiratory, the most common manifestation is pneumonia (PCP- diffuse interstitial pneumonia), dissemination is possible

Question 4

2. Describe the common clinical situation in which Candida albicans can cause disease due to localized decrease in host defenses in an otherwise immunocompetent host.

Answer 4

epidemiology: most severe mucosal infections and invasive/disseminated disease occur in more seriously immunocompromised patients (tx, AIDS**, cancer patients or transplant patents)

treatment with broad spectrum antibiotics can cause overgrowth to yeast in immunocompetent host

Question 5

3. Identify oropharyhgeal candidiasis (thrush) as a common and relatively early clinical manifestation in immunocompromised individuals and discuss the significance of candidiasis in these groups

Answer 5

C. albicans most common infecting AIDS, although (early) invasion and dissemination, even in AIDS patients is rare

Question 6

4. Discuss the clinical syndromes of Aspergillus.

Answer 6

allergy/ hypersensitivity pneumonitis/ allergic bronchopulmonary aspergillosis (ABPA)

mycotoxicosis: aflatoxins (fungal toxin- viable toxin not needed)

colonization of pre-existing cavities or fungus balls

invasion into lung tissue or blood and dissemination (poor prognosis)

Question 7

5. Describe the most common clinical manifestation of Pnuemocystis jiroveci infection and the significance of Pneumocystis in an immunocompromised individual.

Answer 7

diffuse interstitial pneumonia: trophozites associated with damage to pneumocytes

symptoms and signs include foamy eosinophilic exudate filling alveoli, honey comb; gas exchange is seriously compromised

Question 8

1. Discuss epidemiology for Candida albicans.

Answer 8

Dx : Syndromes include cutaneous, mucosal, chronic mucotaneous candidiasis (rare); invasive/disseminated

nosocomial blood stream infections

Question 9

1. Discuss the virulence factors of Candidiasis.

Answer 9

morphogenesis; cell-surface adhesions such as integrin complement receptors CR3, CR4; biofilm formation; hydrolytic enzymes

Question 10

1. Discuss diagnosis of Candida albicans two most common syndromes.

Answer 10

vulvovaginal candidiasis (erythema, pruritis, cheesy discharge)

dx. with pelvic speculum exam and testing of vaginal fluid (pH normal, KOH reveals filamentous fungal elements); germ tubes are specific to C. albicans

Oropharyngeal candidiasis (adherent white plaques in mouth, can continue to esophagus)

dx. based on clinical presentation and patient history, confirm with KOH prep of scrapping

positive Candida culture is always significant, limited sensitivity; assay can be use dot detect bacterial endotoxin (LPS)

Question 11

1. Discuss treatment for Candida albicans.

Answer 11

topical antifungals or oral azoles

IV azoles or echinochandins or amphotericin B for more serous infections

C. glabrata and C. krusei may who natural resistance to fluconazole

Question 12

1. What are risk factors for apsergillosis and epidemiology?

Answer 12

risk factors: neutropenia, solid organ transplant, AIDs, chronic granulomatous disease, chemotherapy, steroid therapy

epidemiology: allergy; anatomic abnormalities favorable (cavities); compromise of CMI, esp. neutropenia

Question 13

What are virulence of determinants of apergillus?

Answer 13

allergens, toxins, hydrolytic enzymes

Question 14

List the ways in which P. jiroveci is an atypical fungus.

Answer 14

cholesterol instead of ergosterol
not susceptible to amphotericin B but susceptibly to anitparsitics
life-cycle and fragile trophozoite cell wall
cannot be cultivated in vitro

fugal characteristics: chitin, B-glucan, genes and taxonomy similar with fungi

Question 15

1. Discuss the epidemiology, and diagnosis for Pneumocystis jiroveci.

Answer 15

70-80% of AIDs patients have PCP at least once, and is the cause of death in 15-20%

dx. by 1) histopathologic demonstration by biopsy, 2) B-d Glucan in blood of body fluids (no culture, serology)

Question 16

1. Discuss the treatment for Pneumocystis jiroveci.

Answer 16

TMP-SMX- acute infection or prophylaxis (oral or IV) with high prob of adverse reactions

Others: pent amine, dapsone, pyrimethamin, atovaquone, blindamycin +primaquine

Steroids in acute ill, modulate host inflammatory response