Opportunistic Fungal Infections Flashcards
List the opportunistic fungal infections (5)
Candida albicans Aspergillus fumigatus Cryptococcus neoformans Mucormycosis Pneumocystis jirovecii
What is the most common cause of opportunistic mycoses?
Candida
If you have a patient who is neutropenic, has HIV/AIDS, or is diabetic and you suspect fungal infection - think Candida
Candida dimorphism
Yeast in the cold
Mold in the heat (dafuq??)
Forms pseudohyphae and budding yeast at 20C.
Forms germ tubes (hyphae) at 37C
What fungal infections are patients with chronic granulomatous disease especially susceptible to?
Candida and Aspergillus - catalase (+)
Where is Candida normally found?
It is normal GI flora (including oral cavity). It is present in about 40% of people. As long as host is immunocompetent it doesn’t usually pose any problems
Since it is so common in normal people, it commonly contaminates sputum cultures so WATCH OUT
Candida infection presentations (5)
1) Diaper rash in a characteristic distribution due to the heat and humidity within baby’s diaper
2) Oral candidiasis (thrush) is seen in immunocompromised patients or those using oral steroids.
Oral steroids (inhalers for example) must be followed by oral rinsing to avoid candidiasis
White patches form in mouth that can be scraped off (in leukoplakia you cannot scrape it off)
KOH is used to prep oral cavity scrapings to diagnosis oral candidiasis
3) Candidal esophagitis - white patches/pseudomembranes in esophagus
Associated with AIDS - it’s an AIDS-defining illness (CD4 4.5 it is NOT candida
Candidal vulvovaginitis is common in diabetes and in people who use antibiotics and birth control pills
5) Endocarditis - candida is an important cause of endocarditis
Commonly seen in drug users - Candida is often found growing in certain kinds of heroin. When injected IV, it seeds heart valves. The first valve they would encounter is tricuspid (commonly infected in IV drug users)
Candida Tx
Azoles for minor infection
Amphotericin B for severe, disseminated (in immunocompromised)
Oral or esophageal = Nystatin - a liquid taken as a swish/spit or swish/swallow respectively
For disseminated infection, if Candida is resistant to amphotericin, give capsofungin
Aspergillus flavus
Produces aflatoxins (associated with peanuts) that are extremely carcinogenic - esp for hepatocellular carcinoma
What does aspergillus look like?
Hyphae form acute angles in their branching
Septated
Aspergillus forms conidiophores with fruiting bodies - important for transmission. These conidiophores are released into the air and inhaled by humans. Kind of looks like the end of asparagus.
What are the 3 infections caused by Aspergillus?
1) Allergic Bronchopulmonary Aspergillosis - ABPA
2) Aspergillomas
3) Angioinvasive Aspergillosis
Allergic Bronchopulmonary Aspergillosis presentation
Caused by Aspergillus
Type 1 hypersensitivity
Causes wheezing, fever, migratory pulmonary infiltrate*
ABPA is associated with asthma and CF
Blood tests show high IgE
Aspergillomas presentation
Caused by Aspergilus
Responsible for formation of aspergillomas - fungus balls
These are solid balls of fungus within the lungs
People who are susceptible are those who may already have cavities in lungs (people with TB or Kleb Pneumo)
Aspergillomas are gravity dependent* - in upright CXR, fungus balls will be at bottom of the cavities
Angioinvasive aspergillosus
Worst infection caused by aspergillus
Affects the immunocompromised (Patients with neutropenia from leukemia/lymphoma)
Invades blood vessels and disseminates quickly throughout body.
Fever. Cough w/ hemoptysis.
Invasion of kidneys leads to kidney failure
Endocarditis
Ring enhancing lesions in brain
Could present with “seizures/focal deficits, has a cough and symptoms of pneumonia and in the past had TB” - Ring enhancing lesions gives us Aspergillus
Infection can also spread to paranasal sinuses and may cause necrosis around the nose (also seen in mucor)
Aspergillus Tx
Less serious - Voriconazole
Aspergillomas need to be surgically debrided in addition to treatment
For angioinvasive you need Amphotericin B
Cryptococcus capsule
It is heavily encapsulated
Capsule is made up of repeating polysachharide capsular antigens - main virulence factor making it anti-phagocytic - basis for a dx test
Cryptococcus transmission
Often in pigeon droppings/soil
After it is inhaled it settles in lung as primary focus
Random unique fact about cryptococcus
It is urease (+)
Who is most at risk for a cryptococcus infection?
It is an opportunistic infection!
Immunocompromised - esp in HIV, high dose steroids, malignancies
What is the #1 cause of fungal meningitis?
Cryptococcus
Cryptococcus presentation
Pulmonary symptoms:
Cough, dyspnea, other serious lung infections
Unlikely to be caught at this stage though and will progress to more worrisome symptoms
Can spread to CSF and cause meningitis - can lead to permanent neuro issues/death
Summary: Fever, pneumonia, meningitis
After invading brain, crypto has unique brain findings - Soap Bubble Lesions in gray matter of brain = crypto meningitis
Cryptococcus diagnosis
Culture on Sabouraud agar (ALL FUNGI)
- This takes weeks to come back though
Use bronchopulmonary washings to diagnose - tissue samples are stained with mucicarmine (red) or methanamine silver stains
Lumbar puncture to dx crypto meningitis:
- CSF stained with India Ink (This is a negative staining technique - background dark, organism transparent)
- We will see the organism and its capsule as a halo
Latex Agglutination Test - detects the polysaccharide capsular antigen and causes agglutination - it detects its repeating capsular antigen
- More sensitive
Cryptococcus Tx
For crypto meningitis: Joint therapy with amphotericin B + Flucystosine
Followed by maintenance therapy with fluconazole
What 2 fungi is mucormycosis caused by?
Mucor and Rhizopus (a bread mold)
Mucormycosis transmission
Spore inhalation
Who is most at risk of mucormycosis infection?
It is opportunistic! Immunocompromised (leukema and neutropenia especially) and diabetics
What does mucormycosis look like?
Hyphae are not septated and have wide-angle (90 degrees) separation - looks like a tire iron
Mucormycosis pathogenesis and presentation
After inhalation, the fungi like to proliferate in blood vessel walls, especially where there is excess glucose and ketones - explains why diabetics are at heightened risk
DKA is most common predisposing factor to this fungus
After invading blood vessels, the fungus likes to invade cribiform plate of skill and enter the brain
This causes necrosis of tissues leading to rhinocerebral mucormycosis and eventually to frontal cortex abscesses.
Patients present with black eschar on face and in nasal cavity. Prognosis if this is present is very poor. Necrosis of nasal cavity and eyes - bc it spreads so quickly through blood vessels it likely means that it has spread already to deep parts of brain causing neuro deficits and death
What is the most common predisposing factor for mucormycosis infection?
DKA
Mucormycosis Tx
Surgical debridement of dead tissue
Amphotericin B for medical management
Pneumocystis transmission
respiratory transmission
PCP presentation
Can infect normal people, but usually asymptomatic. Immunocompromised people are the only ones with signs of infection
PCP is an AIDS-defining illness CD4
PCP Diagnosis
Confirm by getting good sample with brochoalveolar lavage (lung biopsy would work too, but it’s more invasive)
Get the sample, do methamine silver stain on tissue - PCP will look like disc-shaped yeast (ovoid)
PCP Tx
Prophylaxis in HIV+ patient with CD4
