Fungi: Opportunistic Fungal Infections Flashcards
List the opportunistic fungal infections
- candida albicans
- aspergillus fumigatus
- Cryptococcus neoformans
- mucor
- rhizopus
- pneumocystis jirovecii
Candida albicans is a
dimorphic fungus, but differs from other dimorphic fungi in that it forms pseudohyphae and budding yeast at 20°C (yeast form), and germ tubes at 37°C (mold form)
Candida albicans forms
- germ tubes at 37°C (mold form)
2. pseudohyphae and budding yeast at 20°C (yeast form)
Candida albicans fungi are
catalase positive
Candida albicans can cause
- cutaneous candidiasis in areas exposed to heat and humidity (diaper rash in infants)
- disseminated disease in immunocompromised patients (especially those with neutropenia)
- HIV-associated esophagitis (an AIDS-defining illness), which presents with adherent grey/white pseudomembranes
- infection of the vulva and vagina (vulvovaginal candidiasis), which typically presents with vulvar pruritus and a thick white vaginal discharge
oral thrush due to Candida albicans
oral thrush due to Candida albicans (which commonly presents as white patches on the lining of the mouth) is associated with oral or inhaled steroid use and immunosuppression
the white patches of Candida albicans fungi that form on lining of the mouth can be
scraped off
Candida albicans infection can be diagnosed with
KOH mount of oral/vaginal/skin scrapings (microscopic examination will show budding yeast and pseudohyphae)
esophageal candidiasis is an
AIDS-defining illness that generally occurs in patients with a CD4+ count <200
risk factors for vulvovaginal candidiasis
uncontrolled diabetes mellitus, antibiotic use, and high estrogen levels (i.e. oral contraceptives, pregnancy)
the vaginal pH in vulvovaginal candidiasis
the vaginal pH typically remains normal (3.8-4.5) in vulvovaginal candidiasis
Candida infective endocarditis commonly affects
Candida infective endocarditis commonly affects the tricuspid valve and is associated with IV drug use, prosthetic heart valves, and indwelling lines
_________ is effective against Candida albicans
fluconazole
__________ can be used to treat Candida albicans infections (typically when resistance or intolerance to antifungals is suspected or proven)
amphotericin B
_________ is used topically to treat Candida skin infection (but is not indicated for vaginal candidiasis) and orally for thrush
nystatin
________ can be used to treat oral, esophageal, and systemic candidiasis
caspofungin/micafungin (echinocandins antifungals)
Aspergillus spp. fungi are
catalase positive
________ produced by Aspergillus flavus can be found in nuts, legumes, wheat, and other crops
aflatoxins
aflatoxins
aflatoxins of Aspergillus flavus have been linked to hepatocellular carcinoma
Aspergillus spp. have
septate hyphae that form 45-degree angle branches
Aspergillus is transmitted via
inhalation of spores (contained in fruiting bodies)
allergic bronchopulmonary aspergillosis (a type I hypersensitivity reaction) presents with
migratory pulmonary infiltrates, wheezing, and increased serum IgE (most commonly in cystic fibrosis and asthma patients)
elevated serum IgE is a common clinical manifestation of
allergic bronchopulmonary aspergillosis (a type I hypersensitivity reaction)
colonization of Aspergillus in the lung
colonization of Aspergillus in the lung (“fungus balls” that usually form in old pulmonary cavities) may cause fever, hemoptysis, and cough
aspergillomas (“fungus balls”) typically develop in
old pulmonary cavities (from tuberculosis, sarcoidosis, emphysema, etc.)
aspergillomas (“fungus balls”) classically appear as
radiopaque structures that shift with change in position on chest X-ray (gravity-dependent)
invasive pulmonary aspergillosis
invasive pulmonary aspergillosis (angioinvasive, airway centered invasive) occurs in immunosuppressed and neutropenic patients
in severely immunocompromised and neutropenic patients, Aspergillus can
in severely immunocompromised and neutropenic patients, Aspergillus can invade blood vessels and spread hematogenously to the kidneys, endocardium, brain, skin, and paranasal sinuses, causing infection and infarction
invasive pulmonary aspergillosis occurs in
immunocompromised/neutropenic patients
invasive pulmonary aspergillosis occurs in immunocompromised/neutropenic patients and can present with
some combination of fever, cough, and hemoptysis, chest pain and dyspnea
in immunocompromised and neutropenic patients, Aspergillus can spread hematogenously to the
- kidneys, which may result in infarction and renal failure
- endocardium, which may result in endocarditis
- CNS; CNS aspergillosis can present with ring-enhancing lesions
- paranasal sinuses, which may lead to tissue necrosis
_______ is effective against aspergillosis
viroconazole
_________ can be used to treat invasive aspergillosis
amphotericin B
Cryptococcus neoformans yeast cells are
- encapsulated by a thick polysaccharide layer with antiphagocytic properties
- urease positive
the thick capsule surrounding Cryptococcus neoformans yeast cells is composed of
polysaccharides
Cryptococcus neoformans is commonly found in
bird (particularly pigeon) droppings and soil and enters the body through inhalation
Cryptococcus neoformans yeast cells are encapsulated by
a thick polysaccharide layer with antiphagocytic properties
Cryptococcus neoformans is an
opportunistic fungi that more commonly affects immunocompromised patients (i.e. HIV patients)
pulmonary cryptococcosis is often
asymptomatic, but may present with coughing and dyspnea
the most common manifestation of Cryptococcus neoformans infection is
meningitis (particularly in immunocompromised patients), which often presents with fever and neck stiffness
Diagnosis of pulmonary cryptococcosis
- microscopic examination of bronchoalveolar lavage prepared with mucicarmine or methenamine stain
- bronchoalveolar lavage can be prepared with mucicarmine (red) or methenamine (silver) stain
in cryptococcal meningitis, India ink staining of cerebrospinal fluid will show
a wide clear zone (capsular “haloes”) around Cryptococcus neoformans yeast cells on a dark background
the latex agglutination test detects the polysaccharide capsule antigen of Cryptococcus neoformans in the serum and cerebrospinal fluid for diagnosis of
cryptococcosis
Diagnosis of Cryptococcosis via latex agglutination test
the latex agglutination test detects the polysaccharide capsule antigen of Cryptococcus neoformans in the serum and cerebrospinal fluid for diagnosis of cryptococcosis
cryptococcal meningoencephalitis may present with
“soap bubble” brain lesions on MRI
initial treatment of cryptococcal meningitis is
a combination of amphotericin B and flucytosine (followed by long-term therapy or fluconazole)
_______ is given for long-term maintenance therapy for cryptococcal meningitis (after initial treatment of amphotericin B and flucytosine)
fluconazole
Mucor spp. and Rhizopus spp. are opportunistic fungi that cause
mucormycosis
mucormycosis affects
immunocompromised patients
mucormycosis is strongly associated with
diabetes mellitus and diabetic ketoacidosis
certain species of Rhizopus are
common bread molds
Mucor spp. and Rhizopus spp. enter the body through
inhalation
mucormycosis caused by Rhizopus spp. is strongly associated with
diabetic ketoacidosis (likely due to ketone reductase activity of Rhizopus spp., which allows for survival in an acidic environment)
_____ _____ of Mucor spp. and Rhizopus spp. form nonseptate hyphae that branch at right angles (90°)
mold forms
Mucor spp. and Rhizopus spp. proliferate in
blood vessel walls
Mucor spp. and Rhizopus spp. can enter the brain via the
cribriform plate
rhinocerebral mucormycosis can lead to
necrosis of the nasal cavity, presenting as a black eschar on the palate or turbinates
treatment of mucormycosis includes
amphotericin B and surgical debridement
Pneumocystis jirovecii pneumonia is the most prevalent opportunistic infection in
HIV patients and is an AIDS-defining illness
Pneumocystis jirovecii is an opportunistic fungi and affects
immunocompromised patients almost exclusively
disease caused by Pneumocystis jirovecii in immunocompetent patients is
extremely rare (immunocompetent individuals may be asymptomatic carriers of P. jirovecii)
HIV patients with a CD4+ count <200 are at risk of developing
Pneumocystis jirovecii pneumonia
“ground glass” infiltrates on chest X-ray are a feature of
Pneumocystis jirovecii pneumonia
microscopic examination or PCR of bronchoalveolar lavage fluid or induced sputum sample can be used to
diagnose Pneumocystis jirovecii pneumonia
methenamine silver stain of lung biopsy or bronchoalveolar lavage fluid shows
disc-shaped yeast-like cells in Pneumocystis jirovecii pneumonia
yeast-like cells of Pneumocystis jirovecii have
an ovoid or “crushed ping pong ball” appearance on microscopic examination of methenamine silver stained lung tissue or bronchoalveolar lavage fluid
______ is used in HIV patients for prevention (given prophylactically when CD4+ count is <200) and treatment of Pneumocystis jirovecii pneumonia
Bactrim (trimethoprim-sulfamethoxazole)
_______ is used in HIV patients for prevention (given prophylactically when CD4+ count is <200) and treatment of Pneumocystis jirovecii pneumonia
trimethoprim-sulfamethoxazole
________ can be used in HIV patients for prevention (given prophylactically when CD4+ count is <200) and treatment of Pneumocystis jirovecii pneumonia when trimethoprim-sulfamethoxazole is not tolerated
pentamidine