Sketchy Micro: Fungi Flashcards
What dimorphic fungi is associated with bird or bat droppings?
Histoplasma capsulatum.
Look for cave dwellers and farmers with chickens.
Where is Histoplasma Capsulatum endemic to?
Midwestern and Central states, notably along the Mississppi and Ohio River valley.
How is Histoplasma Capsulatum diagnosed?
What are some clinical manifestations of Histoplasmosis?
- chronic pulmonary issues similar to TB
- erythema nodosum
- hepatosplenomegaly
- cough, fatigue, weight loss, and lung cavitations
What would you see on CXR in histoplasmosis?
Enlarged hilarious and mediastinal nodes and popcorn calcifications.
How can reactivation occur with Histoplasmosis?
Immunosuppression, HIV, or TNF-alpha inhibitors (ie infliximab, etanercept, adalimumab, certolizumab, and golimumab).
What is the treatment for Histoplasmosis?
Oral azoles or amphotericin B for severe infections.
Itraconazole is the preferred azole.
How is Histoplasma capsulated transmitted?
Inhalation of airborne spores from mold.
How is erythema nodosum describes?
Painful red nodules typically found symmetrically on the shins.
What dimorphic fungus is primarily found in eastern and central USA near t he Ohio and Mississippi River valleys and the Great Lakes?
Blastomyces dermatitidis
How is Blastomyces dermatitidis reproduced?
Broad based budding
How is Blastomyces dermatitidis transmitted?
Inhalation of mold spores, colonizing in the lungs.
What are the findings for blastomycosis?
- patchy alveolar infiltrate (“haziness”) and cavitary lesions on CXR
- if
immunocompromised, then skin ulcerations and osteomyelitis
How would you diagnose for Blastomycosis dermatitidis?
KOH prep/culture and urine antigen test
How would you treat for Blastomycosis dermatitidis?
Itraconazole and amphotericin B
What dimorphic fungus is commonly found in California and Southwestern states?
Coccidiodes immitis
How is Coccidiodes immitis transmitted?
Inhalation from dust, look for post-earthquake scenarios
What is another name for coccidioidomycosis?
San Joaquin Valley fever
How is Coccidiodes immitis shown in the body?
yeast-like spherules (larger than RBCs) containing endospores, these endospores spread through the lungs
How does coccidioidomycosis present?
Acute pneumonia, fever, sweats, and arthralgias. Also look for erythema nodosum in immunocompromised pts, meningitis can also occur.
How does coccidioidomycosis present on radiograph?
Cavitis or nodules in the lungs
How do you treat coccidioidomycosis?
Oral azoles for local lung involvement and Amphotericin B for systemic manifestations
Where in the world is Paracoccidioides brasiliensis most commonly seen?
Brazil and South America
How is Paracoccidioides brasiliensis transmitted?
Inhalation of mold spores and respiratory droplets
How does paracoccidioidomycosis present?
- Cough
- Lymphadenopathy (cervical, axillary, and inguinal)
- Granulomas in the lungs
- Mucosal ulcers in the upper respiratory tract
How do you treat Paracoccidioidomycosis?
Azoles and amphotericin B
What does Malassezia furfur cause?
Pityriasis versicolor under hot and humid conditions
How can you diagnose Malassezia furfur?
KOH prep of skin scrapings showing a “spaghetti and meatball” appearance.
Where does Malassezia furfur reside in the skin?
Stratum Corneum
How does Pityriasis versicolor present?
Hypopigmented or hyper pigmented patches on sun exposed skin, typically chest and back.
What is the mechanism behind the patches in Pituriasis versicolor?
Lipid degradation caused by the fungus, leading to FA production damaging melanocytes
What is Malassezia Fungemia associated with?
Neonates receiving Total parenteral nutrition (TPN)
- via catheters
Also seen in lipid transfusion in adults, though symptoms not as severe
What is the treatment for Pityriasis versicolor?
Topical Selenium sulfide (aka Selsun Blue) promoting the shedding of the stratum corneum.
Name the different dermatophytes:
Trichophyton, Epidermophyton, and Microsporum
Term for Dermatophyte infection on the scalp:
Tinea capitis
Term for Dermatophyte infection on the body:
Tinea corporis
Term for Dermatophyte infection on the groin:
Ținea cruris (jock itch)
Term for Dermatophyte infection on the feet:
Tinea pedis (athletes foot
How would you diagnose dermatophyte infection?
KOH prep
- Microsporum may fluoresce under Wood’s lamp
How do you treat tinea infections?
Topical azoles like clotrimazole
Term for Dermatophyte infection in the nails:
Onychomycosis
How do you treat onychomycosis?
Oral terbinafine or oral griseofulvin
- griseofulvin can also be used in severe tinea infections
What dimorphic fungus is rose thorn, tree bark, and bushes?
Sprorothrix schenkii
How does Sprorothrix schenkii present microscopically?
Cigar- shaped cells
How does sporotrichosis present?
Local pustules or ulcers, over time additional nodule can appear in an ascending pattern along the lymphatic channels
How do you diagnose Sporotrichosis?
Culture the organism, biopsy can reveal granulomas containing histiocytes, multinucleate giant cells, and the yeast cells
How do you treat Sporotrichosis?
Itraconazole or less commonly used Potassium iodide
Describe the characteristics of Candida albicans:
- opportunistic
- catalase-positive
- dimorphic fungus: pseudohyphae and budding yeast at 25 C, germ tubes at 37 C
What patient population is generally affected by Candida Pathologies?
- neutropenic
- diabetics
- HIV or AIDs
What can Candida albicans manifest if infected?
- oral candidiasis (steroid pts) and candida esophagitis (CD4 < 200 can be AIDs defining)
- candida vulvovaginitis (birth control, abc, diabetics, does not change pH)
- diaper rash due to a warm and humid environment
- Endocarditis (IVDA)
*rinse mouth after oral steroids
What medication can be used in cases of Ampho B resistant Candida?
Capsofungin
- MOA: Caspofungin blocks the synthesis of β(1,3)-d-glucan of the fungal cell wall, by non-competitive inhibition of the enzyme β(1,3)-d-glucan synthase
Is Aspergillus fumigatus catalase positive or negative?
Opportunistic or non opportunistic?
Positive and opportunistic
What does Aspergillus fumigatus produce that makes it so dangerous?
What does can it contaminate?
- Produces Aflatoxins which is associated with HCC
- contaminates nuts, legumes, wheat, and other grain crops.
How is Aspergillus fumigatus identified?
Septate hyphae that branch at acute 45 degree angles
How is Aspergillus fumigatus transmitted?
Inhalation of spores present in its fruiting bodies.
How does ABPA present?
Allergic bronchopulmonary aspergillosis (type 1 hypersensitivity reaction)
- seen in pts with vystic fibrosis and asthma
- shows increased serum IgE, migratory pulmonary infiltrates, wheezing, and fever
What are Aspergillomas?
Fungus balls in old pulmonary cavities.
- fever, hemoptysis, and cough
- seen in conditions like TB, sarcoidosis, emphysema, and klebsiella
- CXR shows radiopaque structures that shift upon pt position
What can Aspergillus fumigatus cause if invades the blood?
- kidney infarction
- endocarditis
- CNS lesions
- Necrosis in the paranasal sinuses
- known as angioinvasive aspergillosis
What is the treatment for Aspergillus fumigatus?
Voriconazole and amphotericin B
What pt population is primarily infected with Cryptococcus neoformans?
Immunucompromized individuals, look for pts with malignancies, HIV, or on high dose steroid therapy.
How does Cryptococcus neoformans evade the immune system?
- Urease enzyme
- heavily encapsulated with repeating polysaccharide capsular antigen
Where can Cryptococcus neoformans be found?
Soil and pigeon droppings
What complication can Cryptococcus neoformans form?
Meningitis
How can you identify Cryptococcus neoformans?
- Bronchopulmonary washings
- Tissue staining with Mucicarmine (red) or Methanamine silver stains
- also India Ink staining CSF
- Latex agglutination test to detect Polysaccharide capsular antigen
What will you see in imaging for Cryptococcus neoformans?
“soap bubble lesions” in the brain’s gray matter
What is the tx for Cryptococcus neoformans?
Amphotericin B and flucytosine, with maintenance therapy using Fluconazole
Which fungi cause mucormycosis?
Mucor and Rhizopus (bread mold)
What pts are at risk for mucormycosis?
Immunocompromised individuals, esp leukemia, neutropenia, and diabetes
How does Mucor and Rhizopus infect and invade?
Spore inhalation, proliferating in the blood vessel walls, especially in setting with elevated glucose and ketones, like in DKA.
How is Mucor and Rhizopus identified?
Non-septate hyphae with wide-angle branching at 90 degrees
How does Mucor and Rhizopus make its way up to the brain?
What can it cause?
Pierces through the cribriform plate causing rhino cerebral mucormycosis, in advance stages causes frontal cortex abscesses resulting into tissue (liquefactive) necrosis.
Black eschar can be visible in the nasal cavity and on the face.
What is the tx for mucormycosis?
Combination of surgical debridement to excise necrotic tissue and amphotericen B.
Is Pneumocystis Pneumonia an AIDs defining illness?
Yes, significant correlation when CD4 could is below 200
What can you see on CXS indicating diffuse interstitial pneumonia caused by Pneumocystis jiroveci?
Ground glass appearance
What is the definitive method of diagnosing PCP?
Bronchoalveoloar lavage (BAL) with methenamine silver staining, showing disc-shaped yeast cells
What is the treatment for Pneumocystis jiroveci?
- Bactrim (trimethoprim-sulfamethoxazole) for tx and prophylaxis
- Those with sulfa allergies Pentamidine
