Microbiology - Opportunistic & deep fungal infections Flashcards Preview

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Flashcards in Microbiology - Opportunistic & deep fungal infections Deck (9):
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1. What types of host are susceptible to opportunistic mycoses? Give a few examples

Opportunistic mycoses are infections caused by fungi of low virulence and thus require impaired host immunity – localised or generalised. Patients with HIV/AIDS or those on immunosuppressants.

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2. What are some risk factors for patient susceptibility to candidaemia?

Debilitation, recent surgery, immunosuppression
Recent or current antibiotics
Intravascular cannulas (portals of entry)
Concurrent skin or mucous membrane candidiasis
Patient on TPN (total parental nutrition)

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3. What are some clinical manifestations of systemic candidiasis?

Once in bloodstream, Candida can settle into any tissue/organ where it produces nodules, abscesses and tissue destruction
Candidaemia (40% mortality rate) and organ invasion → “invasive candidiasis”
Retinal candidiasis – externally observable
Pulmonary candidiasis
Cutaneous candidiasis (seeding of skin from inside) -externally observable
Renal candidiasis – multiple small abscesses

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4. What are some manifestations of invasive pulmonary aspergillosis?

In severely immunocompromised,
Necrotizing bronchopneumonia
Septic emboli to other organs (brain)
High mortality

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5. What are some manifestations of disseminated aspergillosis?

In severely immunocompromised,
Spreads to many other organs (rhino-orbital, cerebral)

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6. Outline some features of rhinocerebral mucormycosis

Mucormycosis cause infections in severely compromised hosts
Predilection for invading and destroying blood vessels → necrosis of tissue – commonly involve the facial sinuses and orbits with gross, rapid tissue destruction and high mortality
Fascial: weakness, numbness, pain
Nasal: purulent drainage, stuffiness, rhinorrhoea, epistaxis, nasal hypoesthesia
Ocular: periorbital pain, blurred vision, amaurosis, progression to blindness
CNS: convulsions, dizziness, altered mental status

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7. What is the relevance of a positive India Ink preparation?

A positive India ink preparation means that Cryptococcus neoformans is present – visualised if sample is put on glass slide with India ink as it blocks out light except where it is transmitted through the capsules

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8. How does one acquire Cryptococcus and how does it manifest after infection?

Cryptococcus neoformans occurs widely in nature – serotypes A and D found in pigeon droppings, B and C associated with eucalyptus trees. Infection acquired by inhalation and usually is asymptomatic
Disease can occur in: immunocompetent hosts AND immunocompromised hosts
Pulmonary cryptococcosis is caused by C. neoformans. The respiratory tract is route of entry and leads to lung nodules/masses with or without cavitation, mediastinal lymphadenopathy and pleural effusion. It can metastasize to brain
Symptoms on presentation can be: asymptomatic, mild cough and low-grade fever to high fever and severe shortness of breath

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9. Outline the features of CNS cryptococcosis?

Most common fungal infection and 2nd most common opportunistic infection of CNS
CNS cryptococcosis results in meningitis or meningoencephalitis, headache, seizure or blurred vision - due to increased intracranial pressure, acute or insidious onset, infection may not be suspected

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