RTI VIII

Question 1

list the primary fungal pathogens

Answer 1

• primary (healthy & immunocompetent)
  
  • Histoplasma capsulatum
  • Blastomyces dermatidis
  • Coccidiodes immitis
  • Paracoccidiodes brasiliensis

Question 2

list the opportunistic fungal pathogens

Answer 2

• opportunistic (immunocompromised individuals)
  
  • Cryptococcus neoformans
  • Aspergillus sp.
  • Pneumocystis jiroveci

Question 3

all primary fungal RTIs are acquired via ____ and all are _____

Answer 3

all primary fungal RTIs are acquired via inhalation and all are dimorphic

Question 4

____ & ____ are endemic in the area of the Mississippi River Valley and the Ohio River Valley

Answer 4

H. capsulatum & B. dermatitidis are endemic in the area of the Mississippi River Valley and the Ohio River Valley

Question 5

____ is endemic in the area of Southwestern US and Northwestern Mexico

Answer 5

C. immitis is endemic in the area of Southwestern US and Northwestern Mexico

Question 6

list the clinical features of fungal RTIs

Answer 6

Question 7

fungi that cause RTIs are able to convert to form ____

Answer 7

fungi that cause RTIs are able to convert to form capable of replication at 37 C

• mycelial → yeast form
• may enhance survival of the fungi since yeasts aren’t killed as easily by phagocytes
• colonize resp. mucosa

Question 8

describe how H. capsulatum can grow inside macrophages

Answer 8

• H. capsulatum
  
  • can increase phagolysosomal pH
  • interferes with enzyme activity and antigen processing

Question 9

the composition of the ___ may be important in the pathogenesis of fungi

explain this

Answer 9

the composition of the cell wall may be important in the pathogenesis of fungi

• certain components linked with virulence
  
  • e.g. virulence in P. brasiliensis is linked to presence of α-(1,3)-glucan in cell wall

Question 10

describe obtaining samples and techniques used for diagnosing fungal RTIs

Answer 10

Question 11

delayed hypersensitivity skin tests are useful for diagnosis of _____

Answer 11

delayed hypersensitivity skin tests are useful for diagnosis of Coccidiodomycosis

• mycelial phase antigen: coccidioidin
• spherule phase antigen: spherulin

Question 12

describe the exoantigen test

Answer 12

• exoantigen test:
  
  • basis = immunodiffusion
    
    • look for presence of specific cell free antigens produced by mycelial phase of the fungi

Question 13

the natural habitat of Histoplasma capsulatum is _____, such as that enriched with ____

Answer 13

the natural habitat of Histoplasma capsulatum is soil with high nitrogen content, such as that enriched with bird or bat droppings

Question 14

acquiring Histoplasmosis is dependent on… (2 things)

Answer 14

Question 15

name the 2 clinically significant varieties of Histoplasma

Answer 15

• H. capsulatum var capsulatum
  
  • pulmonary and disseminated infections
  • Eastern US and Latin America
  • thinner cell walls, smaller size
• H. capsulatum var duboisii
  
  • _​​_skin and bone lesions
  • tropical Africa
  • thick walled; larger yeasts

Question 16

describe what to look for when examining a tissue infected with Histoplasma

Answer 16

Question 17

Blastomyces is found in ____ and outbreaks are associated with contact with _____

Answer 17

Blastomyces is found in decaying organic matter and outbreaks are associated with contact with soil

Question 18

in Blastomycosis, look for ____

Answer 18

in Blastomycosis, look for skin lesions

Question 19

describe what to look for when examining a tissue infected with Blastomyces

Answer 19

look for single broad base bud in a yeast (B = Blastomyces)

Question 20

Coccidioides immitis is endemic to _____

Answer 20

clinical syndrome = Valley Fever

Coccidioides immitis is endemic to desert southwestern US, Nothern Mexico, certain areas of Central & South America

Question 21

____ is the most virulent of all the human mycotic pathogens

Answer 21

Coccidiodes immites is the most virulent of all the human mycotic pathogens

Question 22

____ protects Coccidioides from phagocytosis

Answer 22

spherules protects Coccidioides from phagocytosis

Question 23

opportunistic pathogens are usually (monomorphic/dimorphic)

Answer 23

opportunistic pathogens are usually monomorphic

Question 24

list the predisposing factor and the major pathogen associated with it

Answer 24

Question 25

Cryptococcus neoformans is the only fungus that is \_\_\_\_

Answer 25

Cryptococcus neoformans is the only fungus that is **encapsulated**

Question 26

describe CSF staining of Cryptococcus

Answer 26

India Ink staining is a negative stain of CSF, where the capsule creates a clear halo

Question 27

describe tissue staining of Cryptococcus

Answer 27

Question 28

Cryptococcus production of capsules is triggered by ____ and is composed of \_\_\_\_

Answer 28

Cryptococcus production of capsules is triggered by **inhalation** and is composed of **glucuronoxylomannan (GXM)**

Question 29

Cryptococci can oxidize exogenous _____ into ____ that prevents the fungi from phagocytic oxidative damage

Answer 29

Cryptococci can oxidize exogenous **catecholamines** into **melanin** that prevents the fungi from phagocytic oxidative damage

Question 30

Pneumocystis jirovecii is an unusual fungus because it lacks ____ in cell walls and has ____ instead

Answer 30

Pneumocystis jirovecii is an unusual fungus because it lacks **ergosterol** in cell walls and has **cholesterol** instead

Question 31

an AIDS patient is at risk of acquiring Pneumocystis jirovecii once the CD4 cell count drops below \_\_\_\_

Answer 31

an AIDS patient is at risk of acquiring Pneumocystis jirovecii once the CD4 cell count drops below **200 cell/uL**

Question 32

describe the staining of Pneumocystis jirovecii

Answer 32

Question 33

a "branching, tree-like pattern" on staining is indicative of \_\_\_\_

Answer 33

a "branching, tree-like pattern" on staining is indicative of **Aspergillus**

Question 34

describe the 2 forms of aspergillosis

Answer 34

* allergic: needs underlying asthma or CF * invasive: hyphae invade tissue (transplant patients -- lung) * deadly, invasive pneumonia * hemoptysis * high mortality