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Microbiology > Exam #7: Fungal & Parasitic Infections of the CNS > Flashcards

Exam #7: Fungal & Parasitic Infections of the CNS Flashcards

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Biology 101 flashcards
1
Q

What is the leading cause of fungal meningitis?

A

Cryptococcal meningitis

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2
Q

What two systemic fungi most commonly cause meningitis?

A

Crytococcus neoformans

Coccidioidies

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3
Q

How are the systemic mycoses acquired?

A

Inhalation of fungal elements

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4
Q

What form of Coccidioides immitis infects man?

A

Filamentous mold infects man, which is then converted to yeast in tissues during infection

*Remember, “mold in the cold, yeast in the heat”

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5
Q

What form of crytococcus neoformans infections man?

A

Encapsulated yeast

Note that this is particular to cryptococcus neoforms, it is an encapsulated yeast BOTH in the environment & in infected individuals

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6
Q

Where is Coccidioidomyocsis endemic? When do most endemics occur?

A
  • San Joaquin Valley of California & in Southern Arizona i.e. Southwestern US
  • Drought-rain-drought pattern with large numbers of fungal elements present in blowing dust
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7
Q

What form of Coccidioides is found in man?

A

Spherule= a multinucleated structure that produces hundreds of single nucleated spores

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8
Q

What clinical syndromes are caused by Coccidiomycosis?

A
  • Pulmonary disease= mild to moderate flu-like illness that largely resolves spontaneously
  • Coccidial meningitis= chronically developing headache, fever, & stiff neck

*Note that in comparison to bacterial meningitis, fungal meningitis is has a SLOW onset

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9
Q

How is Coccidiomycosis diagnosed?

A
  • Antigen detection in CSF

- Serology

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10
Q

How is Coccidiomycosis treated?

A

Amphotericin B

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11
Q

How is cioccidial meningitis diagnosed?

A
  • Mainly based on history
  • Antigen detection in CSF
  • Serology i.e. antibody presence, which has limited utility in areas where coccidiomyocses is common

Note that cultivation is rarely successful

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12
Q

Where is cyrptococcus neoformans found?

A

Abundant in soil contaminated with bird droppings

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13
Q

What clinical syndromes are caused by Cryptococcus neoformans?

A
  • Pulmonary Disease= asymptomatic to mild flu-like illness that is self-resolving
  • Cryptococcal meningitis= *the most common cause of fungal meningitis
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14
Q

Describe the presentation of cryptococcal meningitis.

A
  • Chronic onset of typical meningeal symptoms (weeks–>months)
  • Intermittent headache, irritability, dizziness, & other CNS findings
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15
Q

How does the presentation of cryptococcal meningitis differ in AIDS & HIV+ patients?

A

Acute onset instead of chronic onset

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16
Q

How is Cryptococcosis diagnosed?

A

India ink i.e. stain that reveals encapsulated yeast

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17
Q

How is cryptococcal meningitis treated?

A

Amphotericin B & Flourocytosine

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18
Q

What additional therapy is needed following cryptococcal meningitis in AIDS patients?

A

Suppressive therapy

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19
Q

What causes rhinocerebral mucromycosis? What patient population is it most common in?

A
  • Zygomycoses that begins as sinusitis that eventually spreads into the eye & CNS
  • Most common in diabetic patients
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20
Q

What are the causative organisms of rhinocerebral mucromycosis?

A

Rhizopus
Absidia
Mucor

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21
Q

What are the features of the Zygomycetes? How is zygomycoses (mucormycosis) diagnosed?

A
  • Observation of non-septate (aspetate) hyphae

- Observed in blood vessels branching at 90 degrees

22
Q

What is Entamoeba histolytica?

A

Parasite that causes amoebic dysentery & brain abscesses

23
Q

What is Trypanosoma brucei?

A

African trypanosome that causes sleeping sickness

24
Q

What is plasmodium falciparum?

A

Causative organism of cerebral malaria

25
Q

What are opportunistic amoeba?

A

Protozoa/ amoebas that are normally found in the environment & occasionally infect humans

26
Q

What are the three genera of opportunistic amoeba?

A

Acanthamoeba
Naegleria
Balamuthia

  • Thought to normally reside in fresh water & accidental parasites of man
  • All cause fatal infections in man
27
Q

What is PAM?

A

Primary emebic meningoencephalitis that causes:

  • Fever
  • Headache
  • Vomiting
  • Confusion
  • Coma
  • Death
28
Q

What causes PAM?

A

Naegleria fowleri

29
Q

What is PAM associated with?

A

Warm water*

Hot springs
Heated pools
Hot tubs
Neti Pots

30
Q

How is PAM diagnosed?

A

Observation of trophozoite forms of amoeba in the CSF

31
Q

How is PAM treated?

A

There has been some success in treatment with Amphotericin B, but infection is usually fatal

32
Q

What is GAE? How does GAE compare to PAM?

A

Granulomatous amoebic encephalitis that causes a SLOWER onset of:

  • Fever
  • Headache
  • Vomiting
  • Confusion
  • Coma
  • Death
33
Q

What causes GAE?

A

Acanthamoeba

Balamuthia

34
Q

What is Acanthamoeba keratitis?

A

Chronic amoebic infection of the cornea that is associated with contact lens use

35
Q

What is Toxoplasmosis?

A
  • One of the most common parasitic infections in humans & animals
  • Most infections are asymptomatic
  • Becomes a problem in the immunosuppressed–> encephalitis
36
Q

What causes Toxoplasmosis? What patient populations are at risk for Toxoplasmosis?

A

Toxoplasma gondii

  • Congenital infection to child
  • Immunosuppressed
37
Q

Describe the lifecycle of Toxoplasma gondii. How is Toxoplasmosis transmitted to humans?

A

Humans acquire Toxoplasmosis by eating tissue cysts in undercooked meat or ingestion of oocysts in contaminated soil.

  • A single tissue cyst is enough to cause disease, and these are readily found in pork and lamb in the US
  • Soil contamination by cat feces is a major source of oocysts

*Thus, contaminated meat= tissue cyst. Cat feces= oocysts. This is why pregnant women are instructed to avoid cat litter boxes.

38
Q

What are the outcomes of congenitally acquired Toxoplasmosis?

A

Miscarriage/stillbirth or:

  • Blindness
  • Mental retardation
  • Neurological disorders
39
Q

What are the recommendations for pregnant women because of Toxoplasmosis?

A
  • Avoid cats/ cat liter
  • Concern is about a woman having a newly acquired infection during the first trimester
  • If maternal infection in 1st trimester= 15-25% chance of SEVERE disease
  • If maternal infection in 3rd trimester= 65% chance of less severe disease
40
Q

What are the symptoms of Toxoplasmosis?

A
  • Asymptomatic mostly
  • Symptoms are “flu-like”
  • Eventually walls off & forms a bradyozite filled cyst

*If the immune system is weakened, reactivation can occur

41
Q

How is Toxoplasmosis diagnosed?

A
  • Serologic testing
  • Congenital infection tested with PCR for amniotic fluid
  • Maternal= IgM (new infection) or rising IgG titer

ring-enhancing lesion on imaging studies

42
Q

What is the importance of rising IgM & IgG titers of toxoplasmosis?

A

Such titers indicate that an acute infection is likely

43
Q

How is toxoplasmosis prevented?

A
  • Cooking meat thoroughly

- Avoid contact with cat feces, especially if pregnant or immunosuppressed

44
Q

How is toxoplasmosis treated?

A

Immunocompetent= rarely require treatment
Pregnant mother= early treatment to prevent transmission
Children= treatment for 1 year
Immunocompromised= prophylactic therapy

45
Q

What is the name of the pork tapeworm?

A

Taenia solium

46
Q

What form of Taenia solium causes disseminated infection in man?

A
  • Ingestion of embyronated eggs from an infected individual
  • Ingested eggs hatch in the intestine & release larvae that enter circulation & travel to site where they encyst
  • Encysting causes space filling lesions that induce localized inflammation
47
Q

What is the name of the infection of the brain caused by Taenia solium?

A

Neurocyticercosis

48
Q

Who is at risk for Neurocyticercosis?

A

Endemic to South America; increasing prevalence in immigrant families in the US

49
Q

How is Neurocyticercosis diagnosed?

A
  • “Swiss cheese” morphology on imaging

- Serology

50
Q

What is visceral larval migrans?

A
  • Infection of man by ascarid worms that normally infect & cause intestinal disease in dogs & cats
  • Transmission to man is by ingestion of eggs
  • Eggs hatch and larvae migrate to numerous body sites, die, and then a granuloma forms
51
Q

How is visceral larval migrans diagnosed?

A
  • Eosinohpilia

* Note that eggs will NOT be in feces of humans

52
Q

What are the most common symptoms of visceral larval migrans?

A

Symptoms are highly dependent on the location of granuloma formation but,

  • Eye infections are most common
  • Lesions in the brain result in epilepsy or encephalopathy

Microbiology (49 decks)

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