Fungi Flashcards
1
Q
Fungi
A
- eukaryotic
- grow without roots, stems, leaves
- no chlorophyll or photosynthetic pigments
2
Q
Unique Features of Fungi (3)
A
- thick cell walls (chitin, manna sometimes cellulose)
- sterol in cell membrane
- reproduce by spore production
3
Q
Yeasts
A
- unicellular
- reproduce by budding, not binary fission
- form bacteria-like colonies on plates, usually white
- normally oval or spherical
4
Q
Molds
A
- multicellular
- form filamentous hyphae
- reproduce via sexual and asexual spore production
5
Q
Types of Medically Important Molds (5)
A
- dimorphic fungi
- haline hyphomycetes
- zygomycetes
- dematiaceous fungi
- dermatophytes
6
Q
Clinical Classification of Fungi (3)
A
- Superficial - infect skin, hair, nails, mucous membranes, eg. Tinea spp, Malassezia furfur
- Systemic/Deep Mycoses - deep ix’s of internal organs, eg. Histoplasma, Coccidioides imitis
- Opportunistic - ix’s in immunocompromised, eg. Candida spp., Pneumocystis
7
Q
0Medically Important Yeasts (3)
A
- Candida
- Cryptococcus
- other yeast-like fungi, eg. Pneumocystis
8
Q
Yeasts
A
- ubiquitous in environment
- common colonizers of GI and respiratory tract
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
10
Q
Candidiasis Management
A
- remove IV, catheter, foreign bodies
- begin on IV anti fungal against Candida
- consult ID
11
Q
Cryptococcus spp.
A
- associated with bird droppings
- human pathogens - C. neoformans, C. gattii
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
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)
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
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
16
Q
Medically Important Fungi (5)
A
- Aspergillus spp.
- Fusarium spp.
- Agents of mucormycosis
- Dimorphic fungi
- Dermatophytes
17
Q
Aspergillus spp.
A
- ancient filamentous mold
- requires substrate for growth
- differences in antifungal susceptibility amongst species, important to ID quickly
18
Q
Aspergillosis Disease Classification
A
- Allergic Syndromes (allergic bronchopulmonary aspergillosis, allergic sinusitis)
- Colonization and Superficial Syndromes (keratitis, pulmonary aspergilloma, otomycosis)
- Direct inoculation (cutaneous ix)
- 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
Clinical Presentations
- GI
- respiratory
- cutaneous
- CNS
26
Dimorphic Fungi
- 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
Medically Important Dimorphic Fungi
- begin through inhalation of spores
- not transmissible person to person
- Histoplasma capsulatum
- Blastomyces dermatitidis
- Coccidioides imitis
28
Histoplasma capsulatum
- Eastern and Central US
- Europe and Asia
- associated with bat and bird droppings
29
Histoplasmosis
- 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
Blastomyces dermatitidis
- endemic to Mississippi, Ohio River valleys, Northwestern Ontario
- found in moist soil and decomposing organic debris
31
Blastomyces Clinical Presentation
- 50% of exposures result in disease
- sx presentation similar to flu-like symptoms, 3-15 wks post exposure
- rarely progresses to disseminated disease
32
Coccidioides immitis
- endemic to New Mexico, Texas, Central America, South America
- inhalation of spores
33
Coccidiomycosis
- usually presents as flu-like illness
- usually heals with pulmonary fibrosis
- rarely progresses to disseminated ix, often fatal
- incubation period - 10-16 days
34
Dermatophytes (3)
- Trichophyton spp
- Microsporum spp
- Epidermophyton spp
35
Dermatophyte Definition
-filamentous fungi that are able to digest and obtain nutrients from keratin
36
Dermatophyte Ix's
- 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
Tinea spp. Infections
- no living tissue infected, lives in stratum corneum
- response to enzymes released by fungus produces eczematous response
- very common
38
Tinea pedis
- infection of foot web
- shedding of infectious scales
- public health risk
- Trichophyton or Epidermophyton
39
Tinea cruris
- infection of medial proximal thighs, perineum, buttocks
- often spread from feet, common in men
- Trichophyton or Epidermophyton
40
Tinea unguium
- infection of nails
- 50% of dystrophic nails due to fungus
- usually Trichophyton
41
Tinea capitis
- hair loss and inflammation
- worldwide disease
- common in children, highly contagious
- Trichophyton, Microsporum
42
Malassezia spp.
- normal flora, can become opportunistic
- neonates on Total Parenteral Nutrition can produce fungemia, serious ix
- can also cause Tinea versicolor
43
Tinea versicolor
- 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
