Mycology II Flashcards
What type of immunity is responsible for mediating systemic mycoses? Be specific.
Cell mediated immunity, especially TH1 type immune responses
Opportunistic pathogens infect what kind of patient?
Neutropenic patients (immunosuppressed, organ transplant, and cancer pts.
Endemic pathogens live as saprophytes, and enter the body through _____.
Inhalation of spores
What are the four opportunistic species we learned in class?
Candida (yeast, most common)
Cryptococcus neoformans (yeast)
Aspergillus (mold)
Zygomycetes
The species _____ is the leading cause of opportunistic infections.
Candida albicans
Candida is associated with hospital acquired infections (nosocomial infections) due to its affinity for what kind of items? What structures account for this affinity?
Plastics (catheters, central lines, etc.). Candida can form biofilms on plastic tubing due to their sticky pseudohyphae and true hyphae.
Which species of candida does NOT form pseudohyphae and true hyphae?
C. glabrata
C. tropicalis, C. parapsilosis, and C. albicans all have pseudohyphae and true hyphae
Candida appear as an _____ that produce blastoconidia and reproduce by budding.
Oval yeast
C. albicans form what special type of structure in serum at body temperature?
Germ tubes
These structures help us differentiate C. albicans from other yeasts
Identification of different Candida species is best accomplished by culturing on _____
Chrome agar
Candida –> Chrome. They both start with C. I tried.
Candida exist as a _____ in the environment, and as a _____ in mammalian hosts.
Environment: Filamentous fungi
Host: Yeast
As commensals, candida can colonize _____. As such, most candida infections are _____
EVERY MUCOSAL SURFACE
Most candida infections are ENDOGENOUS, resulting from an overgrowth of normal/commensal flora.
Exogenous acquisition is possible, but unusual (contaminated irrigation solutions, IV fluids, donor tissues, unwashed hands, etc.). Remember Candida’s affinity for plastics.
List some risk factors for Candida infection
1) Hematological malignancy
2) Neutropenia *** (Neutrophils = main line of defense)
3) GI surgery (Abx post-op wipe out normal flora –> opportunity for Candida to grow)
4) Extremes of age
5) Exposures
Candida use _____ and _____ to infect the host. What are the roles of these proteins?
Candida use ADHESINS and PROTEASES to infect the host.
Adhesins: Facilitate adhesion to host tissue via binding to fibronectin (an ECM glycoprotein)
Proteases: Destroy epithelial layer, allowing Candida to reach underlying lamina/basement membrane. This allows Candida to get between cells, evading phagocytes. Proteases are located on the hyphae or germ tube.
What are the three major clinical manifestations of Candidiasis?
1) Oropharyngeal infection (thrush)
2) Vulvovaginitis (yeast infection)
3) Cutaneous infection (Jock itch, nail/interdigital infection, diaper rash, e.g.)
Other examples: UTI, pneumonia (ventilated pts.), cardiovascular, CNS, endogenous ocular disease, bone and joint, abdominal, hematogenous)
Oropharyngeal infection (thrush) is characterized by _____ that cannot be scraped off. They are painful and can affect taste.
White plaques
These lesions can be seen around the lips and may go all the way down to the pharynx. They present as white cottage cheese like lesions (patchy to confluent), perhaps with angular chelitis.
Vulvovaginitis is a yeast infection of the _____.
Vaginal mucosa
The loss of normal flora (from douching, abx) in the healthy vagina results in the loss of _____, an organism that contributes to the vagina’s acidic pH.
Lactobacilli
What are some predisposing conditions that may lead to vulvovaginitis?
Diabetes
Pregnancy
Broad spectrum abx usage
Changes in vaginal acidity
etc.
Cutaneous disease caused by Candida most often occurs in _____ and is associated with _____.
Cutaneous disease caused by Candida most often occurs in MOIST PARTS OF THE BODY (groin, fat folds, under breasts, etc.) and is associated with POOR HYGIENE.
Additionally the skin may be weakened by trauma, burns or maceration, providing a route of entry for Candida.
Diagnosis of Candidiasis is accomplished by _____, _____, and _____.
1) Observing yeast and pseudohyphae in sputum, exudates, or tissue
2) Culture
3) Complement fixation, immunodiffusion, Beta-D-glucan test (best for Candidiasis)
What are the treatments for mucosal and cutaneous Candidiasis?
Topical antifungals - Nystatin, Miconazole for vulvovaginitis
Oral fluconazole, itraconazole
What are the treatments for deep seeded Candidiasis? How and why is C. glabrata treated differently?
Oral or IV fluconazole or echinocandin
C. glabrata is treated with amphotericin B and echinocandin because it can be resistant to fluconazole.
What non-pharmacologic measures should be taken to treat Candidiasis? What additional measures should be taken for immunosuppressed patients?
Non-pharmacologic: Remove contaminated catheters and other possibly infected material, drain abcesses
Immunosuppressed patients: Reconstitute immune system along with antifungal treatment.
Which species of Aspergillus is the most important in terms of pathogenicity?
A. fumigatus
Other species: A. flavus, A. niger, A. terreus
Describe the characteristic morphological features of Aspergillus
Branched, septate hyphae that are dichotomous and arise at acute, 45 degree angles. Appear as branches on a tree.
Distinctive conidiophore that looks like an old-fashioned shaving brush or holy water brush.
T/F Aspergillus is non-allergenic.
FALSE
Aspergillus account for a significant amount of allergic rhinitis caused by mold spores.
What structures can obstruct airways and are formed when Aspergillus colonizes the paranasal sinuses and lower airways? What patients are susceptible to the development of these structures? How are they treated?
Aspergillomas (fungus balls)
Tx: Surgical removal
Patients with preexisting pulmonary conditions are most likely to develop aspergillomas. Aspergillus grows easily in areas of previous infection.
Lagniappe: Aspergillomas can spread to other areas via blood to organs, causing an obstruction, or can grow into end-organ tissues.
_____ conidia of Aspergillus can cause pulmonary infections.
Inhaled conidia –> pulmonary infections
T/F Neutropenic patients have a low mortality rate, even when displaying invasive pulmonary aspergillosis & disseminated aspergillosis.
FALSE
These patients have a high mortality rate
The diagnosis for Aspergillosis is derived from what three methods?
1) Observation of characteristic hyphae in tissue samples
2) Culture from clinical samples on mycological agar (ID based on morphology)
3) Immunoassay for serum galactomannan
Treatment for Aspergillosis?
Posaconazole
Amphotericin B
Voriconazole
Echinocandins
(P.A.V.E.)
What class of fungus is characterized by rapid growth, grey to wooly brown colonies, broad hyaline (visualized without stain) and sparsely septate coenoccytic (multinucleated) hyphae.
Zygomycetes
Unlike Aspergillus (conidia on conidiophores), Zygomycetes have _____ within a sac or ______. What other characteristic structure, appearing rootlike, may be present?
Unlike Aspergillus, Zygomycetes have ASEXUAL CONIDIA within a sac or SPORANGIUM.
Rhizoids may also be present.