Microbiology: Fungi/mycology Flashcards
What are the four systemic mycoses?
Histoplasmosis
Blastomycosis
Coccidioidomycosis
Para-coccidiodiomycosis
- all are dimorphic fungi that are yeast in heat and mold in the cold, except for coccidiodiomycosis( is a spherule in the human body)*
Histoplasmosis
Endemic location: Mississippi and ohio river valley regions
(triangle of Iowa-> West Virginia ->Louisiana)
Unique pathology features:
- hides in macrophages and grows in them (similar to bacteria)
- commonly infects humans via bird and bat droppings
Unique signs/symptoms:
- palatial and tongue ulcers
- splenomegaly
- pancytopenia
can form granulomas, but cannot be spread from person-person via humans (unlike TB)
Treatment:
- fluconazole/ itraconazole (local only)
- amphotericin B (systemic only)
Blastomycosis
Endemic region: eastern and central US. Great Lake area.
(square of Minnesota-> Maine -> South Caroline -> northern Louisiana)
Unique pathology:
- buds look similar size to RBCs and are broad
Unique signs/symptoms
- inflammatory lung disease (common)
- can look like squamous cell cancer on imaging
- forms granulomatous nodules on skin
can form granulomas, but cannot be spread from person-person via humans (unlike TB)
Treatment:
- fluconazole/ itraconazole (local only)
- amphotericin B (systemic only)
Coccidiodiomycosis
Valley fever
Endemic region: southwestern US and California
( California, Arizona, Nevada, southern Texas and New Mexico)
Unique pathology:
- is the only spherule fungi with endospores
Unique symptoms:
- almost always disseminates into skin/bones or joints (causes “desert rheumatism” which looks like wide spread arthralgia)
- erythema nodosum ( widespread little red bumps “desert bumps”)
- can cause meningitis if not treated
can form granulomas, but cannot be spread from person-person via humans (unlike TB)*
Treatment:
- fluconazole/ itraconazole (local only)
- amphotericin B (systemic only)
Paracoccidioidomycosis
Endemic region: Latin America
Unique pathology:
- looks like a “captains wheel” under microscope due to unique budding pattern of endospores
- also much larger than RBCs in size
Unique symptoms:
- similar symptoms to blastomycosis, except for idiopathic reasons, tends to infect males> females.
can form granulomas, but cannot be spread from person-person via humans (unlike TB)*
Treatment:
- fluconazole/ itraconazole (local only)
- amphotericin B (systemic only)
Subtypes of Tinea (dermatophytes)
Tinea/dermatophytes is a cutaneous fungal species Which includes:
- microsporum
- trichophyton
- epidermophyton
All require keratin to grow as fuel source and all are have high puritic properties (very itchy)
the type of tinea is named based on where the cutaneous lesions are located
1) Tinea capitis:
- head/scalp region
- associated w/: lymphadenopathy, alopecia and scaling of the scalp skin
2) Tinea corporis: “ringworm/ dermatophyosis”
- trunk region
- associated w/: enlarged erythematous scaly ring-like patches with central clearing (white in the middle) (“ringworm”).
3) Tinea Cruis:
- pubic/ inguinal region
- assocaited with similar patches as tinea corporis, but is usually no central clearing
4) Tinea pedis:
- found either interdigtally (most common) or moccasin (sides of feet)
- similar to tinea cruis but may look more white than red.
5) Tinea unguium:
- found on fingernails
- similar to #3/4
Tinea versicolor
Pityriasis
Caused by malassezia species
- is a yeast-like fungus and is NOT a dermatophyte (despite being called “Tinea”. It uses lipids as its fuel source, not keratin
By degrading lipids in the skin, produces excess acid byproducts that inhibit melanin synthesis via directly inhibiting tyrosinase production
- this results In hypopigmented spots throughout the body, except in acute inflammation (will turn pick/red).
- less Pruritus (itching)than dermatophytes
- look like spaghetti and meatballs on a microscope *
Treatment:
- selenium sulfide
- topical fungal creams that are tolerated by the patient
What is a dermatophyte?
A fungus that colonizers the skin and requires keratin to grow
- are all called “tinea” except for tine versicolor
What are opportunistic fungal infections
Fungi that are far more dangerous than dermatophytes, but are usually only seen in immunocompromised individuals (dermatophytes can be seen in all populations)
Canada albicans
Yeast-like fungi that is dimorphic
- budding yeast forms at 20 C; germ tube shaped at 37C
is an opportunistic infection
Symptoms:
- oral/esophageal thrush (white pseudomembranes on esophagus/tongue/soft palate)
- vulvovaginitis “yeast infection” (diabetic women especially)
- diaper shaped rash (especially in children)
- endocarditis (IV drug users and usually tricuspid valve)
- chronic mucocutaneous inflammation
- can also disseminate, especially in neutropenia patients*
Treatment:
- fluconazole*
- topical “azoles” for vaginitis and rashes
- oral nystatin (oral thrush only)
- can use amphotericin B for disseminated infections
Aspergillus fumigatus
Yeast-like infection that have septae hyphae (bend @ 45 degree-angle under microscope)
- is an opportunistic infection that is responsible for almost all aspergillosis infections and is highly suspected in respiratory defect patients*
Complications:
1) necrotizing otitis externa (really only seen in HIV patinets)
2) acute pulmonary aspergillosis
- seen after inhaling fungi
- most common cause of death in patients who have chronic granulomatous disease
- unremitting fever, dry cough, cheats pain, dyspnea and increased ESR
3) pulmonary aspergilloma
- non invasive infection that usually only colonizes pre-existing cavities
- need to watch for in patients with TB/sarcoidosis/bulbous emphysema/bronchiectasis
- impinges on major vessels and airways causing serious hemorrhages and hemoptysis
- (+/-) productive cough, hemoptysis and weight loss
4) allergic bronchopulmonary aspergillosis
- an allergic reaction to Aspergillus.
- causes hypersensitivity in lungs and increased bronchial obstruction
- * need to watch for this in asthma and CF patients*
Treatment:
- voriconazole* (1st line)
- echinocandins (2nd line)
Cryptococcus neofromans
Yeast-like fungus with thick capsule and is urease positive
- opportunistic infection that is the top cause of fungal meningitis in immunocompromised patients. Also found in bird droppings and soil*
Complications
1) pulmonary cryptococcosis (uncommon)
- fever/cough/pleuritic chest pain
2) cryptococcal meningitis
3) cryptococcal encephalitis
- headache/fever
- vomiting
- nuchal rigidity
- AMS
- seizures
- cryptococcal abscesses (“soap bubble” lesions on Imaging)
4) bone infections
Treatment:
- amphotericin + flucytosine*
- also add fluconazole if meningitis*
- if meningitis/encephalitis, must also drain CSF until treatment is done (easiest way to prevent mortality
Mucormycosis and Rizopusmycosis
irregular broad hyphae fungi with wide-angle branches
Cause rapidly progressive and invasive mycotic infections
- stupid rare, even in immunocompromised patients
opportunistic infection that is round in decomposing organic material and soil. Is especially dangerous/ seen in diabetics and neutropenia individuals
Complications:
1) Rhinocerebral mucormycosis*: when spores enter cribiform plate -> brain
- headache/fever/facial pain at rest, necrotic eschar lesions on face/orbit/palate and brain (usually frontal lobe)
- may show cranial nerve defects
- cavernous sinus thrombi can be generated
- * more common in diabetics experiencing ketoacidosis
- progresses rapidly and is fatal
2) pulmonary mucormycosis:
- seen only in severely neutropenic individuals
- pleuritic chest pain
- cough
- fever/headache
- hemoptysis
3) GI mucormycosis
- seen only in severely malnourished immunocompromised people
- abdominal pain
- GI ulcers/bleeding
4) cutaneous mucormycosis*:
- after traumatic implantation fo spores on open wounds
- causes extensive necrotizing cellulitis
- painful edema/erythema
- raised indurated necrotic lesions
- really the only complication seen in immunocompetent individuals.
5) disseminated mucormycosis*:
- most commonly seen after #2 not being treated successfully
- gets to the brain and produces #1/#3/#4
- almost always fatal
- all symptoms of 1/3/4 and also AMS
Treatment:
- amphotericin B*
- surgical debridement of necrotic tissues*
- hyperbaric oxygen chamber can help also
Pneumocystis Jirovecii
Yeast-like fungi
- opportunistic infection and is leading cause of pneumonia in HIV/AIDS patients*
- is asymptomatic and easily self-limiting in immunocompetent individuals*
Pneumocystis pneumonia:
- diffuse interstital pneumonia
- shows grounded-glass like opacities throughout lungs on imaging
- look like disc shaped yeast-cells on silver staining from lung biopsy
- abrupt onset of tachypnea/fever and non productive cough
- quickly goes into ARDS and is fatal if not treated in immunocompromised people
Treatment:
- TMP-SMX*
- can also use pentamide or dapsone+ TMP-SMX to treat
- prophylaxis = TMP- SMX + pentamide (is required for all individuals who have CD4 counts <200/mm3)
Sporothrix Schenckii
Sporotrichosis/ “Rose Gardner’s disease”
Chronic subcutaneous fungi that is dimorphic
- grows as mold outside body; yeast inside body
- not opportunistic, can infect normal immunocompetent people. Also found in soil, decomposing vegetation and rose thorns. Also cats and chronic alcoholism are possible vectors (although super rare).
- found worldwide but usually in 60-70F temps*
Complications
1) lymphcutaneous sporotrichosis*: most common and first form (1-4 weeks)
- follows after a traumatic inoculation of the subcutaneous tissue
- papules develop at the site of punctuate and ulcerated into a primary lesion
- * papules develop proximally to the sentinel lymph node along the lymph tract.
- nonpurlent and odorless and usually painless
2) pulmonary sporotrichosis
- inhalation of mold
- fever/night seats/weight loss/hemoptysis/productive Purulent cough
3) meningeal sporotrichosis: only in immunocompromised
- chronic fever/headaches
- AMS
- other meningitis symptoms
4) disseminated sporotrichosis only in immunocompromised
- numerous small papules that are necrotic on trunk and limbs
- also follows lymphatic tracts similar to #1
Treatment:
- itraconazole* (local only, #1/2)
- amphotericin B (severe only, #3/4)
