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Microbiology Exam V > Parasitic and Fungal Infections of the CNS > Flashcards

Parasitic and Fungal Infections of the CNS Flashcards

1
Q

Systemic Mycoses

A

Not opportunistic fungi (cause disease in previously healthy individuals)
All five are found in the environment
Acquired by inhalation of fungal elements (hyphae or spores)
-All clinical syndromes begin with pulmonary infection

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2
Q

Systemic Mycoses (Species, Dimorphic vs Encapsulated Yeast)

A

Dimorphic Fungi (Filamentous molds in the environment; yeast in tissues during infection):

  • Histoplasma capsulatum
  • Blastomyces dermatitidis
  • Paracoccidioides brasiliensis
  • Coccidioides immitis
Encapsulated Yeast (Both in environment and in man):
-Cryptococcus neoformans
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3
Q

Coccidioidomycosis

A

Found throughout Western Hemisphere

-Highly endemic to San Joaquin of CA and Southern Arizona

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4
Q

Coccidioidomycosis (Epidemics)

A

Drought-Rain-Drought pattern

-Large numbers of fungal elements present in BLOWING DUST

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5
Q

Coccidioides immitis - Coccidioidomycosis (Characteristics)

A
  • Dimorphic fungus
  • Arthroconidia are easily airborne*

Following inhalation, fungus converts to SPHERULE
-Multinucleated structure, produces hundreds of single nucleated spores

In environment: spores convert to mold form
In tissues: spores develop new spherules

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6
Q

Coccidioides immitis - Coccidioidomycosis (Clinical)

A
  • 60% of infected individuals are ASYMPTOMATIC
  • Pulmonary disease (mild to moderate influenza-like syndrome)
  • Most individuals spontaneously resolve the infection in 2 to 3 weeks
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7
Q

Coccidioides immitis - Coccidioidomycosis (Coccidial Meningitis)

A

Develops SLOWLY with increasing headache, fever, stiff neck, and neurological signs

Frequently fatal if untreated

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8
Q

Coccidioides immitis - Coccidioidomycosis (Diagnosis and Treatment)

A

Diagnosis:

  • Cultivation (RARELY successful)
  • Antigen detection in CSF
  • Serology

Treatment:
Amphotericin B

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9
Q

Cryptococcus neoformans - Cryptococcosis (Characteristics)

A

LEADING FORM of fungal meningitis
Encapsulated Yeast (Not Dimorphic)

Abundant in BIRD DROPPINGS (mostly PIGEON)

INDIA INK STAIN

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10
Q

Cryptococcus neoformans - Cryptococcosis (Pulmonary Disease)

A

Asymptomatic or mild, spontaneously resolving, influenza-like illness
Little sputum production
Little damage to the lung (Granuloma or Cavitation)

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11
Q

Cryptococcus neoformans - Cryptococcosis (Meningitis)

A

MOST COMMON recognized form of cryptococcal infection
Develops SLOWLY
Intermittent bouts of headache, irritability, dizziness, and other CNS findings
Symptoms may present over weeks or months

AIDS/Immunocompromised:

  • Acute onset
  • 10 to 20% of all AIDS patients become infected with C. neoformans (as CD4 levels drop)
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12
Q

Cryptococcus neoformans - Cryptococcosis (Diagnosis)

A
  • INDIA INK STAIN*
  • Cultivation
  • Serology
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13
Q

Cryptococcus neoformans - Cryptococcosis (Meningitis - Treatment)

A
  • Long-term treatment (6-10 weeks) with a combination of AMPHOTERICIN B and 5-fluorocytosine or fluconazole
  • Relapse in AIDS patients is common and may require SUPPRESSIVE THERAPY
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14
Q

Zygomycoses (Characteristics, Predisposing Factors)

A

Ubiquitous in the environment found
-Soil, vegetation, and food (fruits and bread)

Predisposing Factors:
-Immunosuppression, diabetes, and burns

Infection is rare in normal healthy individuals

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15
Q

Zygomycetes

A

Rhizopus
Absidia
Mucor

Non-septate hyphae
Sporangia bearing sporangiospores

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16
Q

Rhinocerebral zygomycosis

A

MOST COMMON form of zygomycosis

  • Primarily in DIABETIC patients
  • Infections in sinuses (inhalation of spores) extend to neighboring tissues

Nasal/sinus symptoms –> Facial/periorbital edema and visual disturbances –> Altered mental status, coma, and death

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17
Q

Zygomycoses (Mucormycosis) (Diagnosis and Treatment)

A

Diagnosis:

  • Observation of HYPHAL ELEMENTS in clinical material
  • Culture confirmation
  • In tissue section BROAD ASEPTATE HYPHAE with BRANCHING AT 90 DEGREE ANGLES

Treatment:
Amphotericin B

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18
Q

Parasitic Infections (3 of them)

A

Entamoeba histolytica
-Brain abscesses

Trypanosoma brucei (African Trypanosome)
-Sleeping sickness

Plasmodium falciparum
-Cerebral malaria

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19
Q

Parasitic Infections (Protozoa vs Helminths)

A

Protozoa (e.g. Strongyloides)

  • Opportunistic Amoeba
  • Toxoplasmosis

Helminths (e.g. Cysticercosis - pork tapeworm; Visceral larval migrans (zoonotic disease))

  • Cysticercosis
  • Visceral larval migrans
20
Q

Opportunistic (Free-Living) Amoeba

A

Include at least 3 genera: Acanthamoeba, Naegleria, and Balamuthia

Thought to normally reside in fresh water and are opportunistic or ACCIDENTAL parasites of man

Only a few thousand documented cases

21
Q

Opportunistic (Free-Living) Amoeba (Disease)

A

All three organisms can cause fatal infections of the CNS:
Primary Amebic Meningoencephalitis (PAM)
-Caused by Naegleria fowleri
-Acquired in HOT SPRINGS, HEATED POOLS, HOT TUBS
-IntraNASAL inoculation
Fatal within 1 week

Neti Pots used with tap water

22
Q

Naegleria fowleri (PAM - Diagnosis and Treatmet)

A

Observation of trophozoites in biopsy material or CSF

Treatment:
Amphotericin B (somewhat successful)
Binds to ergosterol in membranes

23
Q

Granulomatous Amoebic Encephalitis (GAE)

A

Caused by Acanthamoeba and Balamuthia

  • Amoeba invade brain, resulting in a SLOWLY DEVELOPING ULCERATIVE LESION
  • SLOWER (1-2 weeks) course of disease than PAM
  • Symptomatology is similar to PAM, however

Dissemination of infection in AIDS patients

24
Q

Acanthamoeba keratitis (Caused by, Symptoms, Treatment)

A

Chronic infection of the CORNEA
Associated with CONTACT LENS USE and homemade or contaminated cleaning solutions

Symptoms: Corneal ulceration and ocular pain

Treatment: Topical, Corneal Transplantation/Eye enucleation

25
Q

Toxoplasma gondii - Toxoplasmosis (Life Cycle)

A

1) Outdoor cats prey on mice and birds contaminated with sporozoan
2) Sexual reproduction occurs in guts of cat
3) Cats shed oocysts into litter, grass/soil, or garden vegetables, which are then ingested by humans or livestock (end up in humans when they eat the meat)

Can cross placenta and infect fetus

26
Q

Toxoplasma gondii - Toxoplasmosis (Characteristics)

A

One of the most common parasitic infections of humans and animals

30-50% of world’s population has been exposed or infected (seropositive)
Can be reactivated if you become immunosuppressed

Majority of individuals are ASYMPTOMATIC

27
Q

Toxoplasma gondii - Toxoplasmosis (Congenitally Acquired Infection)

A

400-400 cases in the US annually
Miscarriage or stillbirth
Blindness, mental retardation, neurological disorders

28
Q

Toxoplasma gondii - Toxoplasmosis (Ocular infection Immunocompromised)

A

Ocular infection: incidental findings noted at eye exam due to small scars from dead or degenerative infections)

Immunocompromised (HIV/AIDS)- Encephalitis:

  • Severe and often FATAL disease
  • ~10% of new HIV infections will prsent with an episode of toxoplasmosis

10-30% of deaths in European and American AIDS patients were the result of Toxoplasmosis

29
Q

Toxoplasma gondii - Toxoplasmosis (Transmission)

A

Undercooked meat containing cysts or ingesting oocyst shed in cat feces

10-20% of lamb and pork show evidence of cyst

Estimated that ~1% of cats shed oocyst in their feces

  • Cats are the DEFINITIVE HOST
  • Most likely acquire infection from eating infected rodents
30
Q

Toxoplasma gondii - Toxoplasmosis (Maternal Infection)

A

Pregnant women should avoid cats/cat litter

If maternal infection occurs in the FIRST trimester: 15-25% change of fetal infection, but with SEVERE disease

If maternal infection occurs in the THIRD trimester: 65% chance of fetal infection, but with LESS SEVERE or ASYMPTOMATIC disease

31
Q

Toxoplasma gondii - Toxoplasmosis (Disease)

A

Most infections are ASYMPTOMATIC
Symptomatic disease = “Flu-like”

Following infection (ingestion) parasite goes through a process of DIFFERENTIATION and DISSEMINATION (Muscle, Brain)

Immune system “walls off” Bradyzoite filled cyst

Reactivation occurs when immune system is weakened

32
Q

Toxoplasma gondii - Toxoplasmosis (Congenital vs Immunosuppressed)

A

Congenital (Depends on period of acquisition)

  • Miscarriage
  • CNS/Neurological disease

Immunosuppressed

  • Encephalitis (due to reactivation of existing infection)
  • Seizures
  • Death
33
Q

Toxoplasma gondii - Toxoplasmosis (Diagnosis)

A
  • Serological Testing*
  • Congenital infection –> PCR of amniotic fluid

Maternal Testing:
-IgM or rising IgG titers indicate ACUTE INFECTION

Newborn Testing:
-IgM indicates CONGENITAL INFECTION, however, not all infected newborns are IgM positive

34
Q

Toxoplasma gondii - Toxoplasmosis (Prevention/Control)

A

Cooking meat thoroughly

Avoid contact with cat feces (pregnant or immunosuppressed)

35
Q

Toxoplasma gondii - Toxoplasmosis (Treatment)

A

Normal individuals = No treatment required
Pregnant = early treatment
Congenital in children = treated for one year
Immunosuppressed = Prophylactic therapy

36
Q

Taenia solium - Pork Tapeworm (Transmission)

A

Ingestion of undercooked PORK containing encysted larvae leads to INTESTINAL DISEASE

Ingestion of embryonated eggs results in EXTRA-INTESTINAL DISEASE

37
Q

Taenia solium - Pork Tapeworm (Extra-Intestinal Infection)

A

Ingested eggs hatch in intestine and release infectious larvae that enter the circulation and travel to various body sites where they encyst

  • **Cysticercus creates a space-filling lesion and induces localized inflammation
  • Location and size determines pathology (e.g. striated muscle, heart, brain, eyes)
38
Q

Taenia solium - Pork Tapeworm (Neurocysticercosis)

A
  • Severe complication (Seizure and Neurological defects)
  • Most cases occur in recent emigrant from endemic areas MEXICO or their family members
  • Highest incidence is in HISPANIC POPULATION*
39
Q

Taenia solium - Pork Tapeworm (Diagnosis)

A

Extra-intestinal: CT scan, MRI, Serology

40
Q

Ascaris lumbricodies - Ascariasis

A

Largest of intestinal nematodes

41
Q

Visceral Larval Migrans

A
  • Zoonotic disease

- The infection of man by ASCARID worms which normall infect and cause intestinal disease in DOGS and CATS

42
Q

Visceral Larval Migrans (Species and Transmission)

A

Toxocara canis (Dogs) and Toxocara cati (Cats

Transmission achieved through accidental INGESTION OF EGGS

43
Q

Visceral Larval Migrans (Pathogenesis in Humans)

A

Humans ingest eggs, which hatch in the intestine and release larvae
Larvae enter bloodstream and migrate to numerous body sites
Granulomatous lesions develop (commonly in the liver (hepatitis), spleen, lung (cough, wheezing), and EYE
(Like to die in the eye)
*EOSINOPHILIA

44
Q

Visceral Larval Migrans (Disease)

A

Symptoms depend on location; usually include FEVER and EOSINOPHILIA

Lesions in brain can result in epilepsy and encephalopathy

Eye infections are most common:

  • Squinting or loss of visual acuity
  • Retinal scarring
  • Eye enucleation may be necessary
45
Q

Visceral Larval Migrans (Diagnosis and Treatment)

A

Eosinophilia, clinical presentation, serology, and history (pets)

NO eggs in feces; adults only develop in dogs and cats

Treatment:
Symptomatic (Steroids)

Microbiology Exam V (6 decks)

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