Mycology Flashcards Preview

Microbiology USMLE step 1 > Mycology > Flashcards

Flashcards in Mycology Deck (14)
Loading flashcards...
1
Q

Systemic mycoses

A
  • All of them Can cause pneumonia and can disseminate
  • They are dimorphic fungi: cold (20C)= mold, heat (37C) = yeast
  • Treatment: fluconazole or itraconazole for local infection; amphotericin B for systemic infection.
  • Can form granulomas (like TB) but cannot be transmitted person to person (unlike TB)
  • Causal agents:
  • Histoplasma : histoplasmosis
  • Blastomycosis: Balstomyces dermatitidis
  • Coccidioidomycosis: coccidioides
  • Paracoccidioidomycosis: paraccoccidio
  • Dx: sputum cytology and culture on blood agar and sabouraud mold agar.
2
Q

Histoplasmosis

A

Histoplasma capsulatum
*Endemic region: eastern Great Lakes, Ohio, Mississippi River and Missouri River.
* exposure to bird or bat (murcielago) excrement
* Facultative intracellular yeast
* Disease: Fungus Flu (pneumonia) normal patients with acute pulmonary; inmunocompromised patient with chronic pulmonary or disseminated infection.
Lesions have the tendency to calcify as they heal.
Disseminated infection: mucocutaneous lesions are common.
Dx: sputum or blood cultures with mononuclear cells pack with yeast cells.
Tx: itraconazole for mild, amphotericin B for severe.

3
Q

Coccidioidomycosis

A

Coccidioides immitis

*Dimorphic fungus:
-environmental form: hyphae breaking up in arthroconidia.
Found in desert sand: Southwestern United States California especially San Joaquin Valley, Arizona, Texas, Nevada.
-Tissue form: spherules with endospores which we can see in the sputum .
*Disease: Valley Fever: asymptomatic to self-resolving pneumonia or erythema nodosum

4
Q

Blastomycosis

A

Blastomyces dermatitidis
Endemic regions: north and South Carolina, co exist with histoplasmosis
Disease:
-Acute and chronic pulmonary disease
-Disseminated to skin
Dx: Sputum has broad based, budding yeast with double, refractive cell walls

5
Q

Paracoccidioidomycosis

A

LATIN AMERICA systemic mycoses

budding yeasts with “captain’s wheel” formation

6
Q

Cutaneous mycoses

Tinea (dermatophytes)

A
  • Tinea (dermatophytes) : Microsporum, Trichophyton, Epidemophyton. They are branching septate hyphae visible on KOH preparation with blue fungal stain. The lesions are itching.
  • Tinea capitis: head, scalp. Associated with alopecia, scaling.
  • Tinea corporis: torso. “Ringworm” ( Erythematous scaling rings with central clear). Can be acquired from contact with an infected cat or dog.
  • Tinea Cruris: inguinal area.
  • Tinea pedis: three varieties: 1) interdigital 2) moccasin distribution
    3) vesicular type
  • Tinea unguium: onuchomycosis (nails)
7
Q

Cutaneous mycoses

Tinea (pityriasis) versicolor

A

Malassezia furfur

Pathogenesis: degradation of lipids produces acids that damage melanocytes and cause hypopigmented and/or pink patches.
The lesions are in the chest and back

Most common in summer (moist, warm climates)

Dx: microscopy with KOH SHOWS “ spaghetti and meatballs”
Coppery -orange fluorescence under wood lamp

Tx: selenium sulfide, topical and/or oral antifungal medications

8
Q

Subcutaneous mycoses

A

Sporothrix schenckii

  • Sporotrichosis (rose gardener disease) subcutaneous / lymphocutaneous mycetomas.
  • Sporotrichosis pulmonar: alcoholic rose garden sleeper disease (homeless, urban alcoholics)

Dimorphic fungus : *environmental form: on plant material as hyphae with rosettes and sleeves of conidia. * Tissue form: cigar-shaped yeast.

Transmission: traumatic implantation (rose)
Dx: cigar shaped yeast in pus.
Tx: itraconazole or potassium iodide

9
Q

Opportunistic Fungi

AIDS Patients

A
  • Aspergillus fumigatus
  • Candida albicans
  • Cryptococcus neoformans ( most common cause of meningitis in inmunocompromised )
  • Mucor and Rhizopus spp.
  • Pneumocystis jirovecii
10
Q

Candida albicans

A
  • Yeast endogenous to our mucous membrane normal flora.
  • Inmunocompromised patient, overuse of antibiotics , IV drug abusers.
  • Discharge will be like cut cheese
  • Diseases: *Oral and esophageal thrush in inmunocompromised
    * Vulvovaginitis
    * Diaper Rash
    * Endocarditis
    * Chronic mucocutaneous candidiasis
  • Dx: KOH , Septicemia needs culture
  • tx: topical imidazoles or oral ; nystatin
    Disseminated: amphotericin B or fluconazole
11
Q

Aspergillosis

A
  • Causal agent: Aspergillus fumigatus
  • monomorphic filamentous fungus: acute angles, frequent septate hyphae with 45 grades angles
  • risk : patient with asthma, cystic fibrosis, patient with cavity lung, patient with burns
  • Allergic bronchopulmonary aspergillosis and invasive aspergillosis (severe neutropenia)
12
Q

Cryptococcus neoformans

A

Heavily encapsulated yeast. Not dimorphic
Environment source: soil enriched with pigeon droppings .
Acquired through inhalation with hematogenous dissemination to meninges.
Dx: culture in sabouraud agar , India ink
Diseases: - cryptococcosis
- cryptococcal meningitis
- encephalitis (lesions in brain “soap bubble”)
Risk: inmunocompromised patients
Tx: Amb+ flucytosine per 10 weeks, then fluconazole

13
Q

Mucor and Rhizopus spp.

A

Mucormycosis= rhinocerebral infection= zygomycosis

Paranasal swelling, necrotic tissue, hemorrhagic exudates from nose and eyes (black color) and mental lethargy . Headache, facial pain, may have cranial nerve involvement

Patients risk: ketoacidotic diabetic patients and leukemic patients

Pathogenesis: fungi proliferate in the blood vessel walls, penetrate cribiforme plate and enter brain.

14
Q

Pneumocystis jirovecii

A

Fungus, obligate extracellular parasite.

Cause Pneumocystis Pneumonia in AIDS: diffuse interstitial pneumonia

Symptoms: fever, cough, shortness of breath, sputum nonproductive except in smokers

X-ray: patchy infiltrative (ground glass appearance)

Dx: x Ray, clinic, silver staining cysts in bronchial alveolar lovage fluids or biopsy.

Tx: TMP-SmX for mild, dapsone for moderate to severe.