Fungal Infections

Question 1

Yeast

Answer 1

unicellular forms of fungi
Reproduce by budding
Some yeasts produce psuedohyphae, which are buds that do not detach from the parent yeast

Question 2

Molds

Answer 2

Multicellular filamentous fungal colonies w/ branching tubules (hyphae).
Mass of tangled hyphae is called mycelium

Question 3

Dimorphic Fungi

Answer 3

May grow as yeasts or molds, depending on their environment.

Question 4

Pneumocystis jiroveci

Answer 4

Progressive, often fatal, pneumonia in immunosuppressed
*Opportunistic pathogen in AIDS
Reproduces in association w/ alveolar Type I cells
Active disease is confined to the lungs, where the alveoli progressively fill w/ organisms & proteinaceous fluid. This prevents adequate O2 exchange & the patient suffocates.

Question 5

Candida albicans

Answer 5

yeast- resides in oropharynx, GI, vagina

Candidal endocarditis: large vegetations on the heart valves

Question 6

Candida spp.

Answer 6

yeast- some part of normal flora
associated w/ intertrigo (maceration), paronychia (maceration), diaper rash (maceration), vulvovaginitis (alteratio to normal flora), thrush (decreased cell immunity), esophagitis (decreased cell immunity)
Usually associated with superficial infections, deep infections are associated w/ immunocompromised patients
Bacteria from normal flora normally inhibit yeast overgrowth

Question 7

Aspergillus fumigatus

Answer 7

*Opportunistic- involves the lungs
Found in soil, decaying plant matter, dung
Inhalation of conidia spores from environment

Question 8

Allergic Bronchopulmonary Aspergillosis

Answer 8

Virtually restricted to asthmatics
Spores germinate & grow in the airways, causing long-term exposure to the ag.
Bronchi & bronchioles show infiltrates of lymphocytes, plasma cells.
Exacerbation of asthma

Question 9

Colonization of a Preexisting pulmonary cavity (aspergilloma or fungus ball)

Answer 9

Inhaled spores germinate in the warm humid environment provided by these hallows and fill them with masses of hyphae.
No invasion by organisms.
Occur most frequently in old TB cavities
* Best left untreated

Question 10

Invasive Aspergillosis

Answer 10

*Neutropenic patients
Apsergillus readily invades the blood vessls and produces thrombosis.
Multiple nodular infarcts are seen throughout the lung

Question 11

Mucormycosis (Zygomycosis)

Answer 11

Caused by Rhizopus, Mucor, Rhizomucor, Absidia of the class Zygomycetes
Ubiquitous in the environment
Severe necrotizing, invasive, opportunistic infections that begin in the nasal cavities of the lungs.

Question 12

Rhinocerebral mucormycosis

Answer 12

Proliferate in nasal sinuses, invade surrounding tissues, extend into facial soft tissue, nerves,blood vessels and brain.
Causes fatal necrotizing hemorrhagic encephalitis

Question 13

Pulmonary mucormycosis

Answer 13

Resembles invasive pulmonary aspergillosis, including vascular invasion
Usually fatal

Question 14

Subcutaneous zygomycosis

Answer 14

Limited to the tropics and is caused by Basidiobolus haptosporus.
Grows slowly in panniculus, producing a gradually enlarging hard inflammatory mass.

Question 15

Cryptococcus neoformans

Answer 15

Principally affects the meninges, brain & lungs (portal of entry).
Main reservoir: pigeon droppings (alkaline, hyperosmolar)
**Proteoglycan capsule- essential for pathogenicity
Affects those with impaired cell mediated immunity

Question 16

Histoplasmosis capsulatum

Answer 16

Usually self-limited but can lead to systemic granulomatous disease (those w/ impaired cell mediated immunity).
Grows as a mold at ambient temperature, yeast in the body. reservoirs are bird dropping and soil
Inhalation of spores
Reproduces in naive macrophages, producing an area of pulmonary consolidation, leading to a hypersensitivity reaction where activated macrophages produce necrotizing granulomas in lung
Disseminated infection develops in those with impaired immune function.

Question 17

Coccidioides immitis

Answer 17

Coccidioidomycosis- chronic, necrotizing mycotic infection. Resembles TB.
dimorphic fungus; grows as mold in soil where it produces spores
Spores survive naive macrophages and are only destroyed when they become activated.
Necrotizing granulomas form w/ onset of specific hypersensitivity and cell mediated responses.
Infection severity is dependent on the size of the infecting dose and immune status of the host.

Question 18

Blastomyces dermatitidis

Answer 18

Chronic granulomatous suppurative pulmonary disease, which is often followed by dissemination to skin & bone (primarily).
Self-limited in some cases.
Progressive pulmonary disease is characterized by upper lobe infiltrates.
Skin lesions resemble squamous cell carcinoma, most common sign of extrapulmonary dissemination.

Question 19

Paracoccidioides brasiliensis

Answer 19

Paracoccidioidomycosis (south american blastomycosis)- chronic granulomatous infection
Dimorphic fungus, mold resides in soil.
Inhalation of spores- most infections are asymptomatic (men develop asymptomatic infections 15x than women)

Question 20

Sporothrix schenckii

Answer 20

Sporotrichosis- chronic infection of the skin, SubQ tissues and regional lymph nodes
Dimorphic- mold in soil & decaying plant matter, yeast in body
Inoculation from (rose) thorns, infection often spreads along subq lymphatic channels
Begins as a solitary nodular lesion, which often ulcerate & drain serosanguineous fluid.

Question 21

Chromomycosis

Answer 21

Chronic skin infection caused by several species of fungi that live a saprophytes in soil
Lesion begins as papules, over years become verrucous, crusted and sometimes ulcerated

Question 22

Dermatophyte Infections

Ringworm, tinea

Answer 22

Fungi that cause localized superficial infections of keratinized tissues
Trichophyton, Microsporum, Epidermophyton
Resident to soil, on animals and humans
Proliferate within tissue. Spread centrifugally from the initial site, produce round,expanding lesions.Thickening of squamous epithelium, w/ increased #s of keratinized cells.

Question 23

Mycetoma

Madurella mycetomatis, Petrilidium boydii, Actinomadura madurae, Nocardia brasiliensis

Answer 23

Slowly progressive, localized and often disfiguring infection of the skin, soft tissues and bone.
Soil dwelling fungi & fillamentous bacteria
are responsible organisms- tropics
“Madura Foot”-when people walk barefoot on soggy ground
Organism proliferates in subcutis & spread to adjacent tissues,including bone. Mixed suppurative & granulomatous inflammatory infiltrate.
Solitary SubQ abscess slowly expands to form multiple abscesses interconnected by sinus tracts that eventually drain to the skin surface.