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Block 2 > Parasites/Fungi > Flashcards

Parasites/Fungi Flashcards

1
Q

protozoal infection stages

A
  1. trophozoite: feeding “ph-eeding” form; infectious
  2. cyst: hardy, excreted in feces, ingested and able to survive GI tract
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2
Q

Protozoa types

A

Amoebae:
- Entamoeba histolytica: diarrhea

Flagellates:
- Giardia intestinalis: diarrhea, malabsorption syndrome
- Trichomonas vaginalis: urogenital tract infections, vaginitis

Sporozoa:
- Cryptosporidium spp: GI disease

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3
Q

Entamoeba histolytica

A
  • ingested cyst
  • asymptomatic carriage
  • intestinal amebiasis: large intestine tissue destruction
  • extraintestinal amebiasis: liver abscesses, fever, leukocytosis, rigors, brain/heart/lung abcesses
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4
Q

Giardia intestinalis

A
  • ingestion of cysts ==> infection of trophozoites in duodenum & jejunum
  • wilderness streams, lakes, mountain resorts; reservoir animals
  • asymptomatic carriage
  • foul smelling watery diarrhea, fatty stools (“Ghiradelli chocolates”)
  • malabsorption syndrome/chronic diarrhea in IgA deficient patients

Diagnosis: microscopic examination of stools, fecal antigen test

Treatment: Metronidazole

Prevention: boiling water, filtering water (resistant to chlorine)

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5
Q

Cryptosporidium spp

A
  • intracellular parasite in brush border of intestinal epithelial cells
  • waterborne infection: resistant to chlorination and ozone
  • asymptomatic carriage
  • mild, self-limiting diarrhea
  • severe disease with massive fluid loss in immunocompromised patients (AIDS)
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6
Q

Trichomonas vaginalis

A
  • exists only as trophozoite
  • found in urethra, vagina, prostate glands
  • urogenital infections: mostly symptomatic in females (green watery vaginal discharge, vaginitis)
  • transmitted via sexual intercourse

Diagnosis: microscopic examination of discharge, elevated vaginal pH, fluorescent antibodies

Prevention: Metronidazole, safe sex

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7
Q

Protozoa of blood & tissue infections

A

Plasmodium spp: malaria, thru mosquitoes
- P. vivax
- P. ovale
- P. malariae
- P. falciparum

Babesia spp: babesiosis, thru ticks
- B. microti

Toxoplasma gondii: toxoplasmosis, thru oocyst consumption

Lesihmania spp: leishmaniasis, thru sand flies
- L. donovani
- L. tropica
- L. brailiensis

Trypanosomes: sleeping sickness & Chagas’ disease, thru Tsetse flies & kissing bugs
- T. brucei
- T. cruzii

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8
Q

Plasmodium spp

A

Malaria
- P. falciparum
- Chloroquine-resistant P. falciparum are present in all endemic regions except Central America & Carribean
- fever pattern: malignant tertian malaria
- shortest incubation period (7-10 days), most severe fever attacks

Diagnosis: blood smears (thick and thin), look for RBC infection
- Giemsa or Wright stain

Treatment: Chloroquine

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9
Q

Babesia

A
  • transmitted by Ixodes tick
  • invades RBCs and causes lysis
  • does not infect liver

Diagnosis: Maltese cross in blood smear

Treatment: Clindamycin, quinine

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10
Q

Toxoplasma gondii

A
  • CNS toxoplasmosis = brain abscesses
  • AIDS-defining illness
  • CT: multiple ring-enhancing lesions
  • causes clinical symptoms when CD4 count < 100, due to reactivation of previously asymptomatic infection
  • mental status changes, headaches, fevers, focal neurologic deficits, seizures (30%)
  • transmission through cat feces

Prophylaxis: Trimethoprim-Sulfamethoxazole

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11
Q

Leishmania spp

A
  • female sand flies
  • cutaneous, mucocutaneous, visceral diseases

Diagnosis: amastigotes (tissue stage of parasite) in macrophages

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12
Q

Trypanosoma spp

A

T. brucei
- tsetse fly
- African trypanosomiasis (sleeping sickness): CNS, Winterbottom sign (cervical lymph node swelling)

T. cruzi
- kissing bug
- Chagas’ disease: chagoma, rash, Romana’s sign; chronic disease has myocarditis, megacolon

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13
Q

Helminths

A
  • nematodes: round worms
  • platyhelminths: flat worms
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14
Q

Nematodes

A

“you EAT these” = spread thru ingestion
E - Enterobius
A - Ascaris
T - Trichinella

“from the SANd” = spread thru cutaneous penetration
S - Strongyloides
A - Ancylystoma
N - Necator

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15
Q

Enterobius vermicularis (pinworm)

A
  • most common helminth infection in U.S. children
  • eggs deposited at night in perianal folds
  • itching at night
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16
Q

Ascaris lumbricoidis (roundworm)

A
  • large worms
  • larvae develop in lung alveoli ==> swallowed and returned to small intestine
  • intestinal obstruction
  • pneumonia/asthma (Loeffler’s syndrome)
17
Q

Strongyloides stercoralis (threadworm)

A
  • larvae penetrate skin
  • undergoes entire life cycle in human host
  • larvae in sputum and duodenal aspirates
18
Q

Taenia solium (pork tapeworm)

A
  • ingestion of undercooked pork
  • neurocysticercosis (NCC): seizures, headache
  • NCC can be gotten from living in close proximity to someone w tapeworms and ingesting the eggs
19
Q

dimorphic fungi

A

both saprobic (mold, outside body) & parasitic (yeast, inside body, pathogenic) forms:
- histoplasma
- blastomycoses
- coccidioides
- sporothrix
- penicllium (Candida)

all are agents of respiratory infections, none are obligate parasites

20
Q

true pathogenic fungal infections

A
  • superficial infection: Malasezzia furfur
  • cutaneous infection: dermatophytes
  • subcutaneous: sporotrichosis
  • deep/systemic: histoplasmosis
21
Q

Superficial mycoses

A

Pityriasis (Tinea) versicolor:
- superficial infection of epidermis
- caused by Malassezia furfur
- hypopigminted skin
- diagnosis: skin scraping => KOH
- fungal elements with spaghetti and meatballs (hyphae and yeast cells)

22
Q

Cutaneous mycoses

A

Dermatophytosis or Tinea (ringworm):
- caused by dermpatophytes: Microsporum spp, Trichophyton spp, Epidermophyton spp
- only mold form with hyphae (branching septate)
- erythematous outer ring ==> crusting healing center
- jock itch, athlete’s foot, scalp
- diagnosis: Wood’s lamp (UV), Sabourauds agar
- treatment: topical antifungals

Onychomycosis (Tinea unguium):
- fungal infection under nails

23
Q

Subcutaneous mycoses

A

Sporotrichosis
- Sporothrix schenckii
- due to traumatic introduction into subcutaneous tissues
- rose gardener’s disease
- found in soil
- stains like flowers

24
Q

Opportunistic fungal pathogens
(systemic mycoses)

A
  • Candida sp.
  • Aspergillus fumigatus
  • Mucormycosis
  • Cryptococcus neoformans
  • Pneumocystis jirovecii
25
Q

Susceptible populations to opportunistic/primary mycoses

A
  • HIV
  • transplant patients
  • cancer patients
  • rheumatologic conditions => chronic immunosuppression
  • chronic diseases and comorbidities
26
Q

Candida spp

A
  • normal flora in GI/GU tracts
  • dimorphic
  • Candida albicans: causes disease in otherwise healthy patients
  • Mucocutaneous cadidiasis: overgrowth of normal flora after taking antibiotics; superficial infection on mouth (oral thrush, scrapable), groin, armpit, vagina
  • Disseminated candidiasis: contaminated indwelling catheters ==> organism invades tissue; bloodstream infection ==> endocarditis
27
Q

Aspergillius fumigatus

A
  • saprophytic mold
  • treelike pattern with acute angle branching (45˚) and septations
  • colonizing aspergillosis: fungus ball in perinasal sinuses or cavitary lung lesions
  • cause of invasive aspergillosis thru inhalation in immunocompromised patients (innate immunity): pneumonia

Treatment: Voriconazole

28
Q

Mucormycosis (aka Zygomycosis)

A
  • broad nonseptate hyphae
  • invasive infections in those with uncontrolled diabetes
  • high mortality rate
  • rinocerebral/craniofacial mucormycosis: infection of paranasal sinuses with extension into orbit/frontal lobe
29
Q

Cryptococcus neoformans

A
  • yeast-like fungus
  • virulence factor: thick polysaccharide capsule
  • stain with India Ink and Mucicarmine
  • found in bird excreta (pigeon droppings)
  • AIDS-defining illness for those CD4 count < 100
  • entry into lungs ==> pneumonia ==> meningoencephalitis

Diagnosis:
- blood/CSF antigen testing: latex agglutination test
- microscopic examination: India Ink, Mucicarmine stain showing encapsulated yeast
- NO ring-enhancing lesions on CT

Treatment: Amphotericin B + Flucytosine

30
Q

Pneumocystis carinii (jiroveci)

A
  • cyst and trophozoite forms
  • infection in debilitated/ immunosuppressed patients
  • most common opportunistic infection in patients with AIDS - AIDS defining condition
  • pneumonia
  • stain: crushed ping pong balls
  • lung CT: ground glass opacities

Treatment and prophylaxis: Trimethoprim-Sulfamethoxazole

31
Q

Primary (systemic) fungal pathogens

A
  • Blastomyces dermatitidis
  • Histoplasma capsulatum
  • Coccidioides immitis
  • Paracoccidioides brasiliensis
32
Q

Blastomyces dermatitidis

A
  • dimorphic
  • “Chicago fever”; endemic to Mississippi & Ohio river basins
  • decaying organic matter
  • large Broad-Based Budding yeast in tissue
  • cutaneous blastomycosis: papular, pustular, indolent ulcerative-necrotizing and verrucous lesions
  • systemic blastomycosis: can be confined to lung or disseminate hematogenously

Treatment: Amphotericin B for severe blastomycosis with CNS involvement

33
Q

Histoplasma capsulatum

A
  • dimorphic: mold in environment, yeast in tissue
  • endemic to Ohio & Mississippi river valleys, Central/South America
  • bat guano (caves)
  • most cases are asymptomatic
  • clinical forms: acute pulmonary, disseminated, chronic pulmonary
  • stain: halo formed due to retraction of cytoplasm in alveolar macrophages
34
Q

Coccidioides immitis

A
  • dimorphic
  • Southwestern US, found in soil/dust (increased rainfall, dust storms, earthquakes)
  • cough, fever, chest pain, night sweats, joint pain
  • stain: spherule with endospores
35
Q

Paracoccidioides brasiliensis

A
  • dimorphic
  • Central/South America
  • stain: pilot’s wheel (several budding cells attached to parent cell)
  • paracoccicoidomycosis: disseminated disease often causes ulcerative lesions of buccal, nasal, GI mucosa

“Paracoccidio parasails with the captain’s wheel all the way to Latin America”

Block 2 (10 decks)

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