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88 Cards in this Set

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  • Back
Why are fungal infections on the rise?
More immunocompromised patients with weak cell-mediated immunities
Do fungi require an aerobic environment?
YES! They are eukaryotic cells
What is a yeast?
unicellular form of fungi; can appear spherical or ellipsoidal
What are pseudohyphae?
long chains of yeast cell that haven't separated after budding
What are hyphae?
threadlike, branching, cylindrical tubules made of fungal cells attached end to end
What are molds or mycelia?
multicellular colonies composed of clumps of intertwined branching hyphae; produce spores
What are spores?
reproducing bodies of spores; spores are rarely seen in skin scrapings
What are dimorphic fungi?
fungi that can grow as either yeast or mold, depending on environment and temperature
What are saprophytes?
fungi that live in and utilize organic matter as an energy source
What is the essential sterol in fungal cell membranes?
How do amphotericin B and nystatin work?
bind to ergosterol and punch holes in the fungal cell membrane
How does ketoconazole work?
Inhibits ergosterol synthesis
How can fungal capsules be visualized in the lab?
India ink stain
How are the fungal infections organized?
by skin layer affected: 1. superficial; 2. cutaneous; 3. subcutaneous; 4. systemic
What are the 2 superficial fungal infections?
1. pityriasis versicolor; 2. tinea nigra
Are the superficial fungal infections dangerous?
No, they cause change in skin color and are not associated with other symptoms
How are superficial skin infections diagnosed?
skin scrapings mixed with KOH reveal hyphae and spherical yeast as the KOH digests non-fungal debris
How do you treat superficial fungal infections?
With dandruff shampoo or antifungal imidazoles.
What is dermatophytosis?
category of cutaneous fungal infections caused by more than 30 species of fungi; fungi live in skin, hair, nails
What enzyme do the dermatophytotic fungi release?
What are the 5 dermatophytoses?
1. tinea corporis; 2. tinea cruris; 3. tinea pedis; 4. tinea capitis; 5. tinea unguium (onychomycosis)
What is ringworm?
fungi spread into the horny layer of the skin to form a red, raised border in a ring shape
What is tinea cruris?
jock itch
What is tinea pedis?
athlete's foot
What is tinea capitis?
in kids, expanding ring of scaly red lesions with hair loss
What is tinea unguium?
thickened, discolored nails
How do you diagnose a dermatophyte infection?
1. dissolve skin scrapings in KOH; 2. direct exam of hair and skin with Wood's light (some microsporum will fluoresce a brilliant green)
What is the first line drug against the dermatophytes?
topical imidazoles; keep skin dry and exposed to air; oral griseofulvin for tinea capitis and tinea unguium
What are the 2 subcutaneous fungal infections?
sporotrichosis and chromoblastomycosis
How do subcutaneous fungal infections develop?
trauma to skin, fungus remains localized to subcutaneous tissue or spreads along lymphatics to local nodes; these fungi have low virulence
What is sporotrichosis and how is it treated?
Caused by sporothrix schenckii, which is a hazard to gardeners; it is a dimorphic fungus which causes nodules along the lymphatics. Treated with potassium iodide or amphtericin B
What is chromoblastomycosis?
subcutaneous infection caused by copper-colored soil saprophytes found on rotting wood; forms violet wart-like lesions; treated with itraconazole and local excision
What are the 3 fungi that cause systemic infections?
1. histoplasma capsulatum; 2. blastomyces dermatitidis; 3. coccidioides immitis; all 3 are dimorphic fungi
Can the 3 systemic fungi be transmitted person to person?
What makes the 3 fungi dimorphic?
grow as mycelial forms with spores at 25C on Sabouraud's agar, at 37C on blood agar they grow in yeast form. in their natural habitat (soil) they grow as mycelia and release spores into the air where humans inhale them and then they grow as yeast cells in the body
Where are the histoplasma and blastomyces fungi endemic?
Mississippi region
Where is coccidioides endemic?
southwest US
What is the 2nd most common opportunistic infection in AIDS patients in Arizona?
How do the 3 systemic fungi present clinically?
1. asymptomatic or mild resp disease; 2.mild pneumonia with fever, cough, x-ray infiltrates, granulomas with calcifications after resolution - or chronic pneumonia like in TB; 3. disseminated: this occurs rarely and only in immunocomprimised host...can lead to meningitis, bone lytic granulomas, skin granulomas and other organ lesions
How are blastomyces infections treated?
aggressive amphotericin B or itraconazole treatment
How is acute pulmonary histoplasmosis or coccidioidomycosis treated?
no treatment unless it's chronic or disseminated - then itraconazole or amphotericin B
Which of the 3 systemic fungal infection is most severe?
blastomyces dermatitidis
What does cryptococcus neoformans cause?
Where is the cryptococcus neoformans found?
this encapsulated fungus is found in pigeon droppings; 75% of cases are found in AIDS patients
How do you diagnose cryptococcus infection?
lumbar puncture to analyze CSF, an India ink stain to show yeast cells with the surrounding halo, the polysaccharide capsule
What is the most sensitive test to diagnose cryptococcal funal infection?
cryptococcal antigen test
What is the treatment for cryptococcus?
amphotericin B and flucytosine
Is candida albicans ubiquitous?
YES! given out like CANDY to humanity
Who does candida albicans affect?
women with vaginitis, babies with diaper rash, AIDS patients
What does candida albicans cause in immunocomprimised patients?
the same things as in normal hosts, but also...1. esophagitis: thrush extends into the esophagus; 2. disseminated disease: can invade the blood stream and virtually every organ
How can candida albicans be diagnosed?
examine retina to uncover white fluffy candidal patches, treat skin scrapings with KOH, culture biopsied tissue
Is candida albicans part of the normal flora?
YES! will often be cultured from urine, sputum, and stool samples
What are mycotoxins?
toxins that can cause liver damage and liver cancer that are released by fungi
What is the mycotoxin released by aspergillus flavus?
What parts of the world does aspergillus affect?
south of the Sahara in Africa, half the cancers are liver cancers and 40% of screened foods contain aspergillus
What are the two bacteria that ACT like fungi?
ACTinomycetes and nocardia
Why are actinomyces and nocardia discussed with fungi?
they grow in the form of mycelia and are water and soil saprophytes
What type of bacteria are actinomyces and nocardia?
gram + rods
What are the 4 important concepts to remember for actinomyces israelii?
1. gram + filamentous anaerobe that grows in the mouth and GI normally; 2. causes eroding abscesses following trauma to mucous membranes of mouth or GI; 3. abscess pus reveals "sulfur granule" that aren't really sulfur, but microcolonies of actinomyces; 4. treatment is with penicillin G and surgical drainage
How do you identify nocardia asteroides?
forms weakly gram +, partially acid fast beaded branching thin filaments
How do you treat nocardia infections?
trimethoprim and sulfamethoxazole
Treatment of actinomyces and nocardia is a SNAP...
Sulfa for Nocardia, Actinomyces give Penicillin
What does nocardia cause?
inhaled into lung, causing lung abscesses and cavitations
What is the main binding target of antifungal antibiotics?
ergosterol, the sterol unique to fungal cell membranes
How are antifungal antibiotics grouped?
1. serious systemic infections: amphotericin B, itraconazole; 2. less serious systemic infections: the oral azole drugs (ketoconazole, fluconazole, itraconazole); 3. superficial fungal infections: griseofulvin, nystatin and 2 azole drugs (clotrimazole and miconazole)
What are adverse effects of amphotericin?
1. reversible renal toxicity; 2. acute febrile reaction; 3. anemia; 4. inflammation of the vein at the IV site
How do you manage the amphotericin side effects?
give aspirin or acetominophen to prevent febrile reaction, monitor BUN and creatinine levels daily
How do new preparations of amphotericin atenuate side effects?
combined with lipids, they lower nephrotoxicity, but febrile rigors still occur
When is flucytosine used?
rarely because of widespread resistance; used in conjunction with amphotericin B to fight cryptococcal meningitis
How does flucytosine work?
inhibits DNA/RNA synthesis
What are side effects of flucytosine?
1. bone marrow depression; 2. nausea, vomiting, diarrhea
What causes the flucytosine side effects?
drug damages DNA of rapidly dividing cells in the bone marrow and GI epithelium
How does the azole family of drugs work?
inhibits p-450 enzyme system which is involved in ergosterol synthesis; pretty broad spectrum coverage
What are the 2 groups of azole drugs?
1. imidazoles (ketoconazole, miconazole, clotrimazole); 2. triazoles (fluconazole, itraconazole, voriconazole)
How do you remember the triazoles?
"TRY FIVe": fluconazole, itraconazole, voriconazole
What is used primarily for topical fungal infections?
clotrimazole and miconazole
What is used for systemic infections?
fluconazole and itraconazole
What are side effects of the ketoconazole drugs?
1.GI (nausea, vomiting, anorexia); 2. hepatotoxicity (increased hepatic enzymes); 3: inhibition of testosterone synthesis; 4. adrenal suppression
What is fluconazole used for?
kills candida albicans very well, prevents relapse of cryptococcal meningitis in AIDS patients
How is amphotericin B administered?
What is the use of itraconazole?
it's becoming the next amphotericin B without the side effects; used in first line treatment for chromoblastomycosis, histoplasmosis, coccidioidomycosis, blastomycosis
What is special about voriconazole?
has a "VORacious" appetite for fungi; it's a new triazole with more clinical trials necessary to prove efficacy
How does nystatin work?
binds to ergosterol, increasing permeability and leading to lysis
What is nystatin used for?
used topically on skin and mucous membranes; order "Nystatin, Swish and Swallow" for treatment of oral, esophageal and gastric candidiasis
How does griseofulvin work?
disrupts spindle formation, blocking mitosis; deposits in keratin precursor cells in skin, hair and nails
What are adverse effects of griseofulvin?
uncommon, headache, nausea, vomiting, photosensitivity, mental confusion, bone marrow suppression (again, rapidly dividing cells!)
What is KI used for?
to fight local sporotrichosis infections
What is terbinafine?
new fungicidal agent that blocks fungal cell wall synthesis; good for tinea unguium, tinea pedis, tinea capitis, and tinea corporis