RT6

Question 1

pathogenesis of mycobacterium tuberculosis

Answer 1

facultative intracellular bacterium which infects alveolar macs

• Prevent oxidative burst & inhibit phagosome-lysosome fusion􏰀 (role of sulfolipids)
• cell wall components (lipids, LAM) and presence of superoxide dismutase make bacterium resistant to lysosomal enzymes and ROS
• siderophores (exochelin) are secreted

Question 2

diagnosing tuberculosis

Answer 2

acid fast stain or rhodamine-auramine fluorescent stain or culture on enriched or special medium – sputum used

Question 3

culture of tuberculosis is done on what agar

Answer 3

lowenstein jesen agar or oleic acid albumin broth

Question 4

what does tuberculin test prove

Answer 4

prior exposure to mycobacterium tuberculosis (type IV hypersensitivity) and not that someone has tuberculosis

Question 5

treatment of TB

Answer 5

first-line: isoniazid, rifampin, streptomycin, ethambutol
second line: para-aminosalicyclic acid, cycloserine, fluoroquinolones
prevention: BCG vaccine and prophylactic antimycotics

Question 6

what are the primary fungal pathogens

Answer 6

􏰀 Histoplasma capsulatum
􏰀 Blastomyces dermatidis
􏰀 Coccidioides immitis
􏰀 Paracoccidioides dermatidis
(healthy and immunocompromised)

Question 7

what are the opportunistic pathogens

Answer 7

􏰀Cryptococcus neoformans 􏰀􏰀
Aspergillus sp.
􏰀Pneumocystis jiroveci
(immunocompromised)

Question 8

transmission of primary fungal infections

Answer 8

inhalation of aerosols – no person to person

all are dimorphic btw

Question 9

clinical syndromes of: 􏰀  
Histoplasma capsulatum
􏰀Blastomyces dermatidis
Coccidioides immitis
Paracoccidioides dermatidis

Answer 9

histoplasmosis
blastomycosis
coccidioidomycosis
paracoccidioidomycosis

Question 10

clinical symptoms of respiratory fungal infections

Answer 10

• mostly mild fever or cough or asymptomatic
• more severe chills, malaise, fever, chest pain
• sputum production
• weight loss
• granulomatous lesions on skin or mucous membrane
• may mimic TB

Question 11

pathogenesis of the primary fungal infections

Answer 11

reach alveoli –> go from mycelial form to yeast –> colonize respiratory mucosa

Question 12

why do these fungi go to the alveoli

Answer 12

important for iron uptake by fungi

Question 13

laboratory diagnosis

Answer 13

trying to identify the dimorphic fungi

• sputum analyses
• bronchoalveolar lavage
• transtracheal aspirate
• lung biopsy

Question 14

difference between a teleomorph and anamorph

Answer 14

teleomorph - sexually producing form of fungus

anamorph - asexually producing form

Question 15

2 clinically significant form of histoplasma capsulatum

Answer 15

H. capsulatum var capsulatum: Pulmonary & disseminated infections, Eastern US and Latin America, Thinner cell walls; smaller size (2-4 μm)

H. capsulatum var duboisii: Skin and bone lesions, Tropical Africa (“African histoplasmosis”), Thicker walled; larger yeasts (8-15 μm)

Question 16

natural habitat of histoplasma capsulatum

Answer 16

soil with high nitrogen content aka these soils are enriched with bird or bat droppings

Question 17

transmission of histoplasma capsulatum

Answer 17

Microconidia and hyphae are aerosolized and inhaled

Question 18

clinical presentation of histoplasmosis

Answer 18

asymptomatic –> fever, cough, chest pain

Question 19

general features of blastomycosis

Answer 19

contact with soil, found in decaying organic matter

Question 20

presentation of blastomycosis

Answer 20

pulmonary and extrapulmonary disseminated

Question 21

transmission of coccidioidomycosis

Answer 21

inhalation of arthroconidia from soil

Question 22

in coccidioidomycosis, what protects spore from phagocytosis

Answer 22

spherules

Question 23

most virulent of all the human mycotic pathogens

Answer 23

coccidioides sp

Question 24

form of opportunistic pathogens

Answer 24

monomorphic (compare to dimorphic nature of primary fungal infections)

Question 25

predisposing factor for aspergillus

Answer 25

chemo, neutropenia, and assisted ventilation

Question 26

predisposing factor for p. jiroevi (pneumocystis)

Answer 26

chemo, malnutrition, HIV/AIDS

Question 27

predisposing factor for c. neoformans

Answer 27

malnutrition, HIV/AIDS

Question 28

morphological feature of cryptococcus neoformans

Answer 28

encapsulated yeast

Question 29

most common fungal infection seen in aids patients

Answer 29

cryptococcus neoformans

Question 30

transmission of cryptococcus neoformans

Answer 30

inhalation of unencapsulated yeast found in soil enriched with pigeon droppings

Question 31

pathogenesis of cryptococcus neoformans

Answer 31

inhalation triggers production of capsule made of GXM (glucuronoxylomannan) –> affinity for CNS –> downregulates immune response –> oxidize exogenous catecholamines which leads to production of melanin that prevents fungi from phagocytic oxidative damage

Question 32

most common serious opportunistic illness in HIV infected individuals

Answer 32

pneumocystis

Question 33

general features of pneumocystis/p. jiroveci

Answer 33

lacks ergosterol in cell wall, difficult to grow in culture, may or may not be transmissible

Question 34

aspergillus is found

Answer 34

decaying matter, soil, air

Question 35

two forms of aspergillus

Answer 35

allergic (difficult to diagnose) and invasive (hyphae invade tissue)

Question 36

fungal balls

Answer 36

aspergilloma

Question 37

symptoms of aspergilloma

Answer 37

deadly invasive, pneumonia, hemoptysis, high mortality