Opportunistic Mycoses-Kozel Flashcards
What are the opportunistc mycoses?
- Candidiasis
- Aspergillosis
- Mucormycosis
- Cryptococcosis
- Pneumocystosis
What is the morphology of candida albicans and candida spp?
primarily yeasts; also pseudohyphae and true hyphae
form germ tubes
What are germ tubes?
hypha emerging from a yeast-like structure
What is commensalism?
an association between two organisms in which one benefits and the other derives neither benefit nor harm.
Where does candida albicans and candida spp. hang out?
skin-particularly health care workers
entire GI tract- mouth to rectum
femal genital tract
What are the species of candida spp? What is the most common?
C. albicans (most common) C. glabrata C. parapsilosis C. tropicalis C. krusei C. lusitaniae C. guilliermondii C. dublinensis
What is candidasis?
infection with candida, especially as causing oral or vaginal thrush.
Most infections of candidiasis are (Blank)
endogenous
How do you get canidiasis?
endogenously, normal commensal flora takes advantage of an opportunity to cause infection
What can candidiasis present as?
- Mucus mebrane infection
- Cutaneous candidiasis syndromes
- Deep organ involvement
What are the mucous membrane infections that candidiasis causes?
- Thrush
- Candida esophagitis-often in AIDS
- Vaginitis - 75% of normal women have at least one episode
What organ can be involved with candidiasis?
CNS Endocarditis Pneumonia Bone and Joint pain Urinary tract Abdominal Hematogenous disseminated candidiasis (INVASIVE candidiasis)
What is a nosocomial infection
(of a disease) originating in a hospital.
What is the third most common blood stream infection?
invasive candidiasis (super expensive to cure)
What are the general risk factors for invasive candidiasis?
hematologic malignancy neutropenia GI surgery premature infants patients older than 70 years
What are the specific risk factors for invasive candidiasis?
time spent in the ICU
central venous catheter
colonizaton at multiple sites
number of antibiotics given
How do you diagnose candidiasis?
Direct examination
Culture
How do you directly examine candidiasis to diagnose it?
- Scrapings of mucosal or cutaneous lesions -KOH
- Histopathology
- Budding yeast-like forms and pseudohyphae
How do you test a culture of candidiasis?
- take a sample (scrapings, blood (only 50% pos), tissue or sterile body fluids)
- growth on mycologic media
- selective chromogenic medium (CHROmagar Candida)
- confirmation by germ tube formation
How do different candida spp appear on chromogenic medium?
different colors
How do you treat oral thrush caused by mucocutaneous candidiasis?
- topical creams, lotions; nystatin or clotrimazole
- oral systemic therapy: flucanole or other azoles
- prophylactic fluconazole in AIDS
How do you treat esophagitis caused by mucocutaneous candidiasis?
oral system therapy: fluconazole
How do you treat uncomplicated vaginitis caused by mucocutaneous candidiasis?
over the counter topical azoles
oral azoles
How do you treat recurrent vaginitis caused by mucocutaneous candidiasis?
- remove or treat causal factors, i.e HIV, uncontrolled diabetes, antibacterials, hormone replacement therapy
- induction course of azole followed by long-term maintenance regimen
How do you prevent deep seated candidiasis?
- avoid broad spectrum antibiotics
- meticulous catheter care
- rigorous infection control
How do you treat deep-seated candidiasis?
remove source of infection
- remove or change vascular catheter
- drain abscesses
What antifungal agents should you use on deep-seated candidiasis?
varies w/ site of infection and patient status i.e neutropenic vs. non-neutropenic
If deep seated candidiasis what polyene antifungals should you use?
amphotericin B or liposomal amphotericin B
If deep seated candidiasis what triazole antifungals should you use?
primarily fluconazole
If deep seated candidiasis what Echinocandin antifungals should you use?
caspofungin
What is the morphology of Aspergillus spp?
branched septate hyphae
conidial heads with spheric conidia
Where will you find aspergillus spp?
ubiquitous in air, soil, and decaying vegetation
Hospitals-air, water, potted plants
(CONSTANTLY being inhaled)
WHat is the distribution of aspergillus spp?
worldwide distribution
How many species of importance does aspergillus spp have?
19 disease producing species
WHat is the most common invasive species of aspergillus spp?
A. fumigatus
WHat are the top four most common invasive species of aspergillus spp?
A. fumigatus
A. flavus
A. niger
A. terreus
Is aspergillus easy to treat?
no it is new and hard to treat
What TH-2 response can aspergillosis give you?
allergic bronchopulmonary aspergillosis
What is aspergilloma?
fungus balls of lungs
mass of hyphae in pre-existing cavity
How can aspergillosis infection progress to an invasive syndrome?
- begins in lungs following inhalation of conidia.
- Angioinvasive
What is ingasive aspergillosis associated with?
immunosuppression
i.e. organ, stem cell or marrow transplants, neutropenia, corticosteroids or other immunosuppressive therapies
What are clinical forms of aspergillosis?
invasive pulmonary aspergillosis disseminated infection (EXTREMELY HIGH MORTALITY)
Aspergillosis is toxic, why?
aflatoxin
Is aspergillosis super scary in transplants to get?
YES it kills a lot of people especially liver transplant patients
How do you diagnose aspergilosis?
tissue biopsy
cultures
radiology
If you take a tissue biopsy and look at the histopath what wil you see?
invasion with septate hyphae.
acute-angle branching
What are the special stains you should you in diagnosis of aspergillosis?
Gomori methenamine silver, PAS
If you take a tissue biopsy, is it easy to culture?
yyyeeeeaaaahhhhh
speciation requires skills though
T or F
tissue biopsy sometimes too risky in immunosuppressed patients
T
Are blood cultures for aspergillosis often positive?
no, actually it is rarely
Cultures from a non-sterile site are (easy/difficult) to interpret
difficult
When is radiology useful with aspergillosis?
in invasive pulmonary aspergillosis
Why are biomarkers useful for aspergillosis?
- to identify beta-glucan (nonspecific fungal marker)
- immunoassay for galctomannan in serum
How do you prevent aspergillosis?
- patient isolation, HEPA filters, positive pressure
- Pozaconazole prophylaxis for very high risk patients
How do you treat aspergillosis?
voriconazole (primary therapy)
alternatives: AmB, triazoles, echinocandins
What is the morphology of mucorales and mucormycosis?
Coenocytic hyphae-few septae, multinucleate
Saclike fruiting structure (sporangia) with internal spores (sporangiospores)
Where can you find mucorales and mucormycosis?
ubquitous in evironment, particularly decaying organic substrates: bread, fruits, vegetable matter, soil
Is infection with mucorales and mucormycosis prevalent?
no
What are the important types of fungi in the Mucorales family?
Rhizopus (most prevalent; 47%)
Mucor
Cunninghamella
Absidia
How do you get mucormycosis?
inhalation or cutanaeous or percutaneous inoculation of spores
Is mucormycosis angioinvasive?
yes
What are the risk factors for mucormycosis?
- neutropenia
- solid organ/hematopoietic stem cell transplant
- diabetes or metabolic acidosis
- deferoxamine (chelation) therapy to remove excess iron
What are the clinical diseases associated with mucormycosis?
rhinocerebral-associated with diabetes
pulmonary infection
cutaneous
disseminated mucormycosis
How do you diagnose mucormycosis?
Samples
Histopath
Culture
Biomarkers
What samples do you want to get to diagnose mucormycosis?
Biopsy, swabs, etc.
Blood cultures rarely positive
What should histopath show you in mucormycosis?
– broad (3 to 25 µm diameter), empty, thin-walled, mostly aseptate hyphae
What will a culture of mucormycosis show you?
- rapid growth on standard mycologic media
- speciation based on shape of the sporangium and the location of sporangiospores
What will biomarkers test for mucormycosis show you?
tests for β-glucan or galactomannan are negative
What is the treatment for mucormycosis?
AmB
reverse underlying condition, surgical resection
Why does mucormycosis have such a poor prognosis?
Resistant to many antifungals: ketoconazole, fluconazole, voriconazole, flucytosine (5-FC), and the echinocandins
The patient is a 43-year-old woman who became severely neutropenic during the course of chemotherapy for treatment of breast cancer. She developed cough, chest pain, shortness of breath and had a persistent fever despite conventional antibiotic therapy. Results of a lung biopsy are shown below. What is the diagnosis?
Pulmonary blastomycosis Chronic pulmonary histoplasmosis Pulmonary tuberculosis Invasive pulmonary aspergillosis Progressive pulmonary coccidioidomycosis
This is a case of invasive pulmonary aspergillosis. The micrograph shows branching, septate hyphae. Blastomycosis and histoplasmosis would show yeast cells in tissue. Pulmonary tuberculosis would show small bacilli. Coccidioidomycosis would show spherules with no hyphae
The patient is a 28-year-old who presents with vaginitis that is accompanied by a thick, curdlike discharge. Physical exam showed edema and pruritis of the vulva. Microscopy showed epithelial cells and masses of hyphae. She was given a topical antifungal that is widely available over the counter. What is the mechanism of action of the antifungal?
Blocks ergosterol synthesis Inhibits DNA and RNA synthesis Inhibits squaline epoxidase Inhibits folic acid synthesis Inhibits glucan synthesis
This is a case of vaginal candidiasis. Topicals for treatment of candida vaginitis have an azole as their active ingredient. Azoles inhibit lanosterol demethylase to block ergosterol synthesis. The distractors describe respectively the modes of action of flucytosine, terbinafine, sulfonamides and the caspofungins.
A 12-year-old girl received aggressive chemotherapy for acute lymphoblastic leukemia. Four weeks after initiation of therapy, she presented with signs, symptoms and radiological evidence of brain abscess. A craniotomy and biopsy were done. Histopathology showed the presence of broad, largely aseptate hyphae. Culture grew the organism shown below. What is the best antifungal for treatment of this infection?
Ketoconazole Fluconazole Caspofungin Amphotericin B Flucytosine
This is a case of cerebral mucormycosis. The image shows the sporangium and internal sporangiospores characteristic of the order Mucorales. The drug of choice for treatment of mucormycosis is amphotericin B. The Mucorales are intrinsically resistant to the other antifungals.
