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Infectious Disease and Medical Microbiology > Fungi > Flashcards

Fungi Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

Fungi

A
  • eukaryotic
  • grow without roots, stems, leaves
  • no chlorophyll or photosynthetic pigments
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2
Q

Unique Features of Fungi (3)

A
  • thick cell walls (chitin, manna sometimes cellulose)
  • sterol in cell membrane
  • reproduce by spore production
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3
Q

Yeasts

A
  • unicellular
  • reproduce by budding, not binary fission
  • form bacteria-like colonies on plates, usually white
  • normally oval or spherical
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4
Q

Molds

A
  • multicellular
  • form filamentous hyphae
  • reproduce via sexual and asexual spore production
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5
Q

Types of Medically Important Molds (5)

A
  • dimorphic fungi
  • haline hyphomycetes
  • zygomycetes
  • dematiaceous fungi
  • dermatophytes
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6
Q

Clinical Classification of Fungi (3)

A
  1. Superficial - infect skin, hair, nails, mucous membranes, eg. Tinea spp, Malassezia furfur
  2. Systemic/Deep Mycoses - deep ix’s of internal organs, eg. Histoplasma, Coccidioides imitis
  3. Opportunistic - ix’s in immunocompromised, eg. Candida spp., Pneumocystis
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7
Q

0Medically Important Yeasts (3)

A
  • Candida
  • Cryptococcus
  • other yeast-like fungi, eg. Pneumocystis
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8
Q

Yeasts

A
  • ubiquitous in environment

- common colonizers of GI and respiratory tract

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9
Q

Candida spp.

A
  • over 200 species in nature, C. albicans most common infectious agent of humans
  • many different types of ix’s (vulvovaginal candidiasis, oropharyngeal candidiasis, systemic ix’s)
  • opportunistic ix
  • systemic ix is serious and life threatening
  • management delayed by diagnosis delay
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10
Q

Candidiasis Management

A
  • remove IV, catheter, foreign bodies
  • begin on IV anti fungal against Candida
  • consult ID
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11
Q

Cryptococcus spp.

A
  • associated with bird droppings

- human pathogens - C. neoformans, C. gattii

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12
Q

Cryptococcal Disease

A
  • usually due to C. neoformans
  • usually an opportunistic ix
  • rarely infects immunocompetent (large exposure to aerosolized bird droppings)
  • CNS and pulmonary involvement
  • inhaled into lungs, hematogenous spread to brain, meninges, bones, skin, joints
  • outbreak of C. gattii on Vancouver Island over last 20 years
  • AIDS defining condition
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13
Q

Pneumocystis jirovecii (P. carinii)

A
  • fungal
  • long debate over whether it was fungal or protozoal
  • reproduce in lung alveoli (exact life cycle unknown)
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14
Q

P. jirovecii Epidemiology

A
  • mammal is reservoir
  • haven’t found environmental source
  • most humans exposed by ages 2-4
  • transmitted by airborne route, inhaled
  • low ID and short exposure required for transmission
  • transmission occurs btwn immunocompetent people and immunocompromised people
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15
Q

P. jirovecii Clinical Significance

A
  • AIDS defining illness
  • leading opportunistic ix in AIDS patients
  • presents as non-productive cough, night sweats, fever, tachypnea
  • chest exam: fine basilar rales
  • CXR: diffuse, symmetrical interstitial infiltrates
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16
Q

Medically Important Fungi (5)

A
  • Aspergillus spp.
  • Fusarium spp.
  • Agents of mucormycosis
  • Dimorphic fungi
  • Dermatophytes
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17
Q

Aspergillus spp.

A
  • ancient filamentous mold
  • requires substrate for growth
  • differences in antifungal susceptibility amongst species, important to ID quickly
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18
Q

Aspergillosis Disease Classification

A
  1. Allergic Syndromes (allergic bronchopulmonary aspergillosis, allergic sinusitis)
  2. Colonization and Superficial Syndromes (keratitis, pulmonary aspergilloma, otomycosis)
  3. Direct inoculation (cutaneous ix)
  4. Invasive Syndromes (invasive pulmonary aspergillosis, tracheobronchitis, sinusitis, disseminated ix)
19
Q

Fusarium spp.

A
  • typically found in soils and organic debris
  • direct major trauma required to develop disease in immunocompetent host
  • inhalation or minor trauma enough in immunocompromised host
20
Q

Fusarium Clinical Infections

A
  • keratitis
  • onchormycosis
  • endophthalmitis
  • MSK ix’s
  • disseminated ix’s
21
Q

Disseminated fusariosis

A
  • begins as skin lesions
  • lesions begin as papules, become necrotic
  • in neutropenic pt’s can quickly progress to death
22
Q

Agents of mucormycosis

A
  • eg. Order Morales
  • lid lifters
  • eg. Rhizopus spp., Mucor spp., Absidia spp.
23
Q

Mucormycosis Epidemiology

A
  • ubiquitous
  • low virulence in humans
  • high spore production, rapid growth
  • disease in immunocompromised pt’s, DM pt’s, trauma
24
Q

Mucormycosis Infections

A

-must overcome immune system and gain access to blood stream through respiratory tract

25
Q

Clinical Presentations

A
  • GI
  • respiratory
  • cutaneous
  • CNS
26
Q

Dimorphic Fungi

A
  • grow as molds at environmental temps (25-27 degrees) and yeasts at tissue temps (37 degrees)
  • all are pathogenic to humans
  • many require containment, important to ID and let lab know
27
Q

Medically Important Dimorphic Fungi

A
  • begin through inhalation of spores
  • not transmissible person to person
  • Histoplasma capsulatum
  • Blastomyces dermatitidis
  • Coccidioides imitis
28
Q

Histoplasma capsulatum

A
  • Eastern and Central US
  • Europe and Asia
  • associated with bat and bird droppings
29
Q

Histoplasmosis

A
  • infection common, disease not common
  • spectrum of disease
    • asymptomatic
    • benign respiratory symptoms
    • acute disseminated histoplasmosis (GI sx’s, young children, AIDS pt’s)
    • chronic disseminated histoplasmosis (weight loss, low grade fever, weakness, hepatosplenomegaly, 10-12 mt’s, fatal if not treated)
    • chronic pulmonary (resembles TB clinically and radiologically)
30
Q

Blastomyces dermatitidis

A
  • endemic to Mississippi, Ohio River valleys, Northwestern Ontario
  • found in moist soil and decomposing organic debris
31
Q

Blastomyces Clinical Presentation

A
  • 50% of exposures result in disease
  • sx presentation similar to flu-like symptoms, 3-15 wks post exposure
  • rarely progresses to disseminated disease
32
Q

Coccidioides immitis

A
  • endemic to New Mexico, Texas, Central America, South America
  • inhalation of spores
33
Q

Coccidiomycosis

A
  • usually presents as flu-like illness
  • usually heals with pulmonary fibrosis
  • rarely progresses to disseminated ix, often fatal
  • incubation period - 10-16 days
34
Q

Dermatophytes (3)

A
  • Trichophyton spp
  • Microsporum spp
  • Epidermophyton spp
35
Q

Dermatophyte Definition

A

-filamentous fungi that are able to digest and obtain nutrients from keratin

36
Q

Dermatophyte Ix’s

A
  • chronic process, transmitted by contact (either direct or indirect)
  • some are specifically human pathogens, others found in environment
  • more common in tropical, subtropical regions
37
Q

Tinea spp. Infections

A
  • no living tissue infected, lives in stratum corneum
  • response to enzymes released by fungus produces eczematous response
  • very common
38
Q

Tinea pedis

A
  • infection of foot web
  • shedding of infectious scales
  • public health risk
  • Trichophyton or Epidermophyton
39
Q

Tinea cruris

A
  • infection of medial proximal thighs, perineum, buttocks
  • often spread from feet, common in men
  • Trichophyton or Epidermophyton
40
Q

Tinea unguium

A
  • infection of nails
  • 50% of dystrophic nails due to fungus
  • usually Trichophyton
41
Q

Tinea capitis

A
  • hair loss and inflammation
  • worldwide disease
  • common in children, highly contagious
  • Trichophyton, Microsporum
42
Q

Malassezia spp.

A
  • normal flora, can become opportunistic
  • neonates on Total Parenteral Nutrition can produce fungemia, serious ix
  • can also cause Tinea versicolor
43
Q

Tinea versicolor

A
  • common ix in kids in warm humid area, fungus feeds on skin oils, treat with topical antifungals
  • produces areas of altered pigmentation in skin on chest, back, neck, forehead, face

Infectious Disease and Medical Microbiology (11 decks)

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