Hertz CIS Fungal infections Flashcards
Types of fungus
Superficial and cutaneous mycoses
Subcutaneous mycoses
Endemic mycoses
Opportunistic mycoses
Superficial and cutaneous mycoses
are common and limited to the very superficial or keratinized layers of skin, hair, and nails.
Subcutaneous mycoses
involve the skin, subcutaneous tissues, and lymphatics and rarely disseminate systemically.
Endemic mycoses
are caused by dimorphic fungi that can produce serious systemic illness in healthy individuals.
Opportunistic mycoses
can cause life-threatening systemic diseases in individuals who are immunosuppressed or who carry implanted prosthetic devices or vascular catheters.
Candidiasis
Most Candida infections originate when the normal commensal flora breach the skin or mucosal barriers
C. albicans, are the most frequent cause of human fungal infections
what cells are important for protection against candida infection?
Neutrophils, macrophages and TH17 cells are important for protection against Candida infection
T helper cells are decreased in HIV and make us more susceptible to these types of organisms.
important diagnostic clue of C. albicans
pseudohyphae- chain of budding yeast cells joined end to end at constrictions. Can be seen with yeast and hyphae together in the same tissue.
Invasive candidiasis is caused by bloodborne dissemination of organisms to various tissues or organs, including…
(1) Renal abscesses
(2) Myocardial abscesses and endocarditis
(3) Brain microabscesses and meningitis
(4) Endophthalmitis (virtually any eye structure can be involved)
(5) Hepatic abscesses
Cryptococcosis
C. neoformans and C. gattii, both of which grow as encapsulated yeasts.
while C. neoformans may cause meningoencephalitis in otherwise healthy individuals, it more frequently presents as an opportunistic infection in people with AIDS, leukemia, lymphoma, systemic lupus erythematosus, or sarcoidosis, as well as in immunosuppressed transplant recipients.
Many of these patients receive high-dose corticosteroids, a major risk factor for C. neoformans infection. Cryptococcus neoformans is present in the soil and in bird (particularly pigeon) droppings and infects people when it is inhaled
AIDS with lung stuff, think
pneumocystis carinii
How big is stuff that gets stuck in the lungs?
50 microns- upper airway
25 microns- bronchii
10 microns- gets to the alveoli
if you hear pigeon, CNS, immunocompromised, think
cryptococcus. India ink preparation with the white blobs (capsule) around the bug.
Mucicarmine stains the capsule pink.
The major lesions caused by cryptococcus are
in the CNS, involving the meninges, cortical gray matter, and basal nuclei
loves perivascular area
soap bubble lesion in the brain refers to
cryptococcus
mucicarmine stain in a virchow-Robin perivascular space of the brain
Aspergillus
is a ubiquitous mold that causes allergies (allergic bronchopulmonary aspergillosis) in otherwise healthy people and serious sinusitis, pneumonia, and invasive disease in immunocompromised individuals
major conditions that predispose to aspergillus infection
neutropenia and use of corticosteroids. Aspergillus fumigatus is the most common pathogenic species of the fungus.
45 degree angles of growth, septate, fruiting heads, are key words for
aspergillus
aspergilloma
fungus ball
colonizes, walled off, minimal invasion of the tissues. Necrotizing. - often people have hemoptysis
Right angle branching, no septae, wide and fat…?
zygomycosis (mucormycosis)
Buzz word: wet cigarette paper
history will usually involve being immunocompromised, including diabetes mellitus, iron overload, corticosteroid use, etc.
what bugs love iron?
haemophilus (bacteria) and mucormycosis (fungus)
di morphic fungi
2 different morphologies: one at room temperature (mold) and one at body temperature (yeast farms)
The medically important dimorphic fungi are blastomyces, histoplasma, and coccidioidomyces
Chronic pneumonia– start by thinking
most often a localized lesion in the immunocompetent patient, with or without regional lymph node involvement. Typically, the inflammatory reaction is granulomatous, and is caused by bacteria (e.g., M. tuberculosis) or fungi (e.g., Histoplasma capsulatum)
Histoplasma capsulatum
is acquired by inhalation of dust particles from soil contaminated with bird or bat droppings that contain small spores (microconidia), the infectious form of the fungus. It is endemic along the Ohio and ***Mississippi rivers and the Caribbean
coin lesion in lung that looks like tree bark (calcified spherical nodule)
burned out caseating granuloma
histoplasmosis (do a silver stain to make sure)
rank order in size the 3 things that get stuck in the lungs
tiniest: histo. Easily gets in alveoli
next: blasto– tends to get stuck higher
biggest: coccidio, but it can send endospores down into the alveoli
The diagnosis of histoplasmosis is established by
culture or identification of the fungus in tissue lesions. In addition, serologic tests for antibodies and antigen are also available. Antigen detection in body fluids is most useful in the early stages, because antibodies are formed 2 to 6 weeks after infection
Blastomyces dermatitidis
is a soil-inhabiting dimorphic fungus.
It causes disease in the central and southeastern United States; infection also occurs in Canada, Mexico, the Middle East, Africa, and India.
There are three clinical forms: pulmonary blastomycosis, disseminated blastomycosis, and a rare primary cutaneous form that results from direct inoculation of organisms into the skin
Broad-based buds.
after inhalining spores of Coccidioidomycosis
Almost everyone who inhales the spores of Coccidioides immitis becomes infected and develops a delayed-type hypersensitivity reaction to the fungus.
Indeed, more than 80% of people in endemic areas of the southwestern and western United States and in Mexico have a positive skin test reaction.
One reason for the infectivity of C. immitis is that infective arthroconidia, when ingested by alveolar macrophages, block fusion of the phagosome and lysosome and so resist intracellular killing
if it’s a petri dish taped shut it’s a clue that it’s
coccidioides
people who get infected with histoplasma and show symptoms…
But 10% of infected people develop lung lesions, fever, cough, and pleuritic pains, accompanied by erythema nodosum or erythema multiforme (the San Joaquin Valley fever complex).
Less than 1% of people develop disseminated C. immitis infection, which frequently involves the skin and meninges
landing a helicopter in arizona, get a fever afterward
location and history tell you coccidioides because of soil blowing around and location.
buzz words to think about
cryptococcs- AIDS, soil, bird droppings
candida- pseudohyphae
mucormycosis- diabetes
blasto- broad-based
