Lecture 60 Fungal & Parasitic CNS

Question 1

Most common CNS mycoses

Answer 1

Candidiasis Aspergillus Mucormycosis Cryptococcosis

Question 2

Morphology of cryptococcus neofromans

Answer 2

Yeast cell (identified by budding) surrounded by prominent polysaccharide capsule that looks like a halo in indian ink

Question 3

India ink wet mount and capsule and latex agglutination detection of capsular antigen makes you think:

Answer 3

Cryptococcus neoformans

Question 4

Where is cryptococcus neoformans found?

Answer 4

Everywhere in the environment Mostly growing in pigeon feces in the soil

Question 5

How is one infected with cryptococcus neoformans?

Answer 5

Inhalation of yeast-laden dust => infection of the lungs, transfers to the blood and lymph and thereby to the CNS Does not cause cavitation in the lungs like TB or coccidioidomycosis

Question 6

Cryptococcus virulence factors

Answer 6

Encapsulated: avoid phagocytosis, prevents antigen presentation, inhibits signaling of other macrophages Melanin: in the cell wall and acts as antioxidant Mannitol: inhibits PMN killing

Question 7

Cryptococcus treatment and outcomes

Answer 7

Non-treatment => death (especially in immunocompromised) Amphotericin B and Fluconazole

Question 8

If you see germ tubes, budding yeast, and pseudohyphae, think:

Answer 8

Candida

Question 9

How do people get infected with candida?

Answer 9

Commensal organism–everyone already has it Shows up and causes problems in immunocompromised Often in hospital setting assoc. with catheters and antibiotics

Question 10

What effects come from Candidiasis?

Answer 10

Infects both the meninges and the parenchyma of the brain Causes meningitis and multiple microabcsesses and extensive brain necrosis Hydrocephaly can be present in neonates and infants

Question 11

Cnadidiasis disseminated disease treatment

Answer 11

Amphotericin B and Fluconazole

Question 12

Branching, septate hyphae, think:

Answer 12

Aspergillus

Question 13

What conditions are common for an aspergillus infection?

Answer 13

Aspergillus is an environmental organism and mostly causes disease in immunocompromised, neutropenia, chemo, corticosteroids Infects through lungs or in ear canal

Question 14

Under microscope, what are some structures seen in assoc. with Aspergillus fumigatus?

Answer 14

Septate hyphae! Conidiophores with conidia (not inside a membrane like with Rhizopus)

Question 15

Branching, non-septate hyphae, think:

Answer 15

Mucor and Rhizopus

Question 16

Common seen mycosis in immunocompromised and with diabetic ketoacidosis

Answer 16

Mucormycosis Mucor and Rhizopus

Question 17

Where are Mucormycoses found, how do they usually infect and what can they cause?

Answer 17

Usually found in the soil Infects nasal mucosa, spreads to the brain May invade blood vessels leading to thrombosis or rupture => brain infarction or hemorrhage

Question 18

What agent is most likely picked up while swimming in contaminated water (swimming pools, desert streams, ponds) during summer? Is cause of PAM

Answer 18

Naegleria fowleri PAM = Primary Amoebic Meningoencephalitis

Question 19

Morphology, pathway of infection for PAM

Answer 19

PAM–caused by Naegleria fowleri Infective stage is flagellated trophozoites Infects nasal passages Transforms into amoeboid form Migrates along olfactory nerve to the brain Look like motile WBCs

Question 20

PAM resembles what other kind of meningitis and in what ways?

Answer 20

PAM resembles bacterial meningitis Can cause acute symptoms w/in 5 days Mimics bacterial in that it has high PMN’s, increased protein, decreased glucose, and fever

Question 21

What part of the CNS is damaged by PAM?

Answer 21

Brain parenchyma

Question 22

Acanthamoebiasis background including morphology, life cycle, locations found

Answer 22

Infective trophozoite stage, Resistant cystic stage Found in the soil, hot tubs, and in contact lens solution

Question 23

Pathophysiology of Acanthamoebiasis

Answer 23

Causes meningoencephalitis by infecting the brain parenchyma and causes edema Spreads to the brain through hematogenous routes Tends to infect chronically ill and immunocompromised Causes acanthamoebiasis keratitis and uveitis: often linked to traumatic inoculation of dirt

Question 24

Morphology of Toxoplasma gondii

Answer 24

Troph: tachyzoite (acute), bradyzoite (chronic) Zoitocyst: contains bradyzoites Oocysts: in cat feces

Question 25

Infective stages of Toxoplasma gondii

Answer 25

Zoitocyst or oocyst Comes from either cat feces (oocyst) or undercooked meat–especially pork (zoitocyst) Freezing meat kills cystic stage

Question 26

What individuals are at risk for Toxoplasma gondii?

Answer 26

Many people are infected, but most have no symptoms. Most worried about pregnant women and HIV patients

Question 27

Where do Toxoplasma gondii cysts form?

Answer 27

Muscle and brain tissue

Question 28

Frequent effects of Toxoplasma gondii in HIV patient

Answer 28

Cysts in brain and muscle (including cardiac) Chorioretinitis Focal brain lesions Headaches Mental deterioration

Question 29

Congenital presentation on Toxoplasma gondii

Answer 29

In neonates: CNS disease, chorioretinitis, hydrocephaly, microcephaly, stillbirths, mental retardation, cerebral calcifications Mother’s presentation is unremarkable, but causes fetal damage May not show problems until 2nd or 3rd decade of life

Question 30

Describe basics of Neurocysticercosis

Answer 30

Caused by Taenia solium (tapeworm) from pork Infected by ingesting the eggs Common presentation is headache and seizures, but also hemiparesis Common in developing countries

Question 31

Organism?

Answer 31

Naegleria fowleri

Question 32

Organism?

Answer 32

Cryptococcus neoformans