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Micro - opportunistic fungi


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Describe the appearance of Candida. Where is it found endogenously?
*oval yeast, pseudohyphae may be present
*skin and mucous membranes, esp. skin folds, oral cavity, and female GU tract
How can pseudohyphae be differentiated from normal hyphae?
The walls of pseudohyphae are not parallel.
What does Candida look like on culture?
Not fluffy but rather appear as bacterial colonies.
Name 7 factors which can dispose someone to fulminant infection be Candida.
1.Antibiotic treatment - especially females
2.Maceration of tissues - diaper rash
3.Immunosuppressive steroid tx
6.DM pts
7.HIV and CA pts
What manifestation of Candida infection can signal a low CD4+ count in HIV pts?
Oral thrush
What manifestations of Candida are seen in IV drug abusers?
Fundal endocarditis and endophthalmitis
CA pts with profound immunosupression and Candidemia may present with what symptom?
Microabscesses in the RES.
In diagnosing a Candida infection, why is it important to differentiate between C. albicans and other species?
C. albicans is susceptible to fluconazole, whereas other species will need to be treated with amphoteracin.
What factors may confound diagnosis of Candida?
*b/c it is endogenous, presence may not indicate infection
*pts with candidemia may have negative blood cultures
Describe the appearance of cryptococcus.
Encapsulated round yeast.
What environmental factor stimulates growth of cryptococcus? How is it acquired?
*bird feces
*inhalation of yeast
What patient population most frequently presents with fulminant infection by cryptococcus?
*those with defects in T-cell immunity
What is the most common manifestation of Cryptococcus in HIV/AIDS pts? What part of the structure facilitates this?
*asceptic meningitis
*capsule allows movement into CNS
What is the best means of diagnosing cryptococcus infection? What kind of sensitivity does this method offer?
*detection of antigen in CSF or serum
*90% sensitivity
What asymptomatic manifestation of cryptococcus may appear in immunocompetent patients?
A cryptocoma in the lungs.
What treatment is recommended for HIV patients presenting with cryptococcal infections?
Lifetime fluconazole prophylaxis.
Describe the appearance of Aspergillus. Where is it found in nature?
A mold with septate hyphae that shows acute right-angle branching in tissue. The fungus is ubiquitous and found nearly everywhere.
List the 3 disease states associated with aspergillus.
1.Allergic bronchopulmonary aspergillosis
3.Invasive aspergillosis
What is ABPA? What patient population does it occur most often in?
*allergic bronchopulmonary aspergillosis
*hypersensitivity reaction to spores
*no tissue invasion
*most common in pateinst with reactive airway disease, like CF or asthma
How is aspergillus acquired?
Inhalation of spores.
Aspergillus can form a "fungus ball". What is this and how is it treated?
*grows in cavity spaces in lungs
*because of avscularity, rx are often ineffective and surgery is required
What patient populations are most susceptible to invasive aspergillosis? What is the mortality in these patients?
*HIV, bone marrow and solid organ transplant pts.
*for BM transplants, mortality is 70-100%
*severity of disease correlated with degree of immunosupression
What occurs in invasive aspergillosis?
*invasion of lung tissue and vasculature
*hemoptysis due to massive pulmonary hemorrhage
*septic emboli may cause extra-pulmonary disease
Describe the appearance of the Zygomycetes.
*wide, aseptate ribbony hyphae with right-angle branching
What patient populations are most susceptible to rhinocerebral zygomycosis?
*poorly controlled DM pts
*neutropenic pts
What symptoms does rhinocerebral zygomycosis present with? What are the dangers of this infection?
*H/A, facial pain, periorbital swelling
*penetration into brain has 100% mortality
What treatment is indicated for rhinocerebral zygomycosis?
Aggressive surgical treatment, with debridement to continue until margins are clear.
How is PCP usually identified?
*not able to be cultured
*By direct examination
*induced sputum or bronchoscopic exam
What kind of symptoms are caused by PCP? What part of the organism's pathogenesis contributes to this?
*pneumonia with non-productive cough
*airway fills with foamy exudate which interferes with gas exchange
What are the two recommended rx for tx of PCP?

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