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Microbiology > Parasitology Pt 2 > Flashcards

Parasitology Pt 2 Flashcards

1
Q

3 Classes of Helminths

A
  1. Nematodes (roundworms)
  2. Cestodes (tapeworms)
  3. Trematodes (flukes)
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2
Q

Nematodes (Roundworms)

A
  1. Enterobius vermicularis
    (human pinworm)
  2. Ascaris lumbricoides & suum
    (intestinal roundworms of humans & pigs)
  3. Hookworms
    - Toxocara canis & catti
    - Ancylostoma braziliensis
  4. Trichuris species
    (whipworms)
  5. Dracunculus medinensis
    (Guinea worm)
  6. Filariae
    - Wuchereria bancrofti
    - W. (Brugia) malayi
    - Onchocerca volvulus
    - Loa loa (eyeworm)
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3
Q

Cestodes (Tapeworms)

A

Flat/ribbon-shaped, segmented bodies

Proglottids
(reproductive segments containing both F & M sex organs)

No digestive system
(absorbs nutrients)

Transmitted via ingestion of contaminated undercooked meat OR fleas infected with dog/cat tapeworms

Taenia solium (pork tapeworm)

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4
Q

Taenia solium (pork tapeworm)

A

Pig = 1st intermediate host
1. Ingests embryonated ovum from human feces
2. Cysticercus develops in flesh (burrows/forms cysts in tissue)

Human = 2nd intermediate host
(definitive host)
3. Ingests pork containing cysticerci
4. Cysticercus develops into mature tapeworm in small intestine
5. Ova & ova-filled proglottids passed in human feces

Neurocysticercosis
- Eggs hatch & form cyst in brain

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5
Q

Trematodes (Flukes)

A

Bilaterally symmetrical flat/leaf-shaped

Suckers
(allow attachment while fluid withdrawn)

Can burrow through skin

Hermaphroditic

Life cycle includes 1 or more intermediate hosts (after escapes from egg )
- Larval form = within egg
- Cercariae = last stage

Schistosoma species

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6
Q

Schistosoma species

A

Hermaphroditic

Snail = 1st intermediate host
1. Miracidium hatches from eggs in freshwater & infects
2. Cercariae leave snail

Human = 2nd intermediate host
(definitive host)
3. Cercariae penetrates skin (in water)
4. Immature worm enters bloodstream & ends up in veins near intestine or bladder
5. Reach sexual maturity in veins of abdominal cavity
6. Females produce eggs
7. Eggs enter intestinal tract or bladder
8. Eggs passed in urine or feces into freshwater

Penetration of skin causes itching

Eggs become encapsulated in liver, lungs, brain
- Block portal veinous system

Molecular mimicry (adult worms)
- Incorporate host antigens on surface

Diagnosed by eggs in urine (S. haemotobium) or feces (S. mansoni or S. japonium)

High mortality rate

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7
Q

Enterobius vermicularis

A

Human pinworm
- Very common infection (North America & Europe)

Symptoms:
1. Mild GI upsets
2. Perianal itching
3. Irritability
4. Insomnia
5. Vaginal irritation (adult pinworms)

Diagnosed by eggs (scotch tape test) or worms (flashlight) on perianal area

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8
Q

Enterobius vermicularis:
Life Cycle

A
  1. Human infected when ingest eggs
  2. Eggs hatch in small intestine
  3. Worms migrate to large intestine & reach sexual maturity
  4. Females crawl out of anus & deposit eggs on perianal skin
    - RETROINFECTION (eggs hatch & juveniles crawl back into anus to mature into adults)
  5. Eggs become infective within 6 hrs
  6. Hands, bed clothing/linens, etc. contaminated with infective eggs
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9
Q

Ascaris lumbricoides & suum

A

Intestinal roundworms of humans & pigs

Most common nematode infection world-wide

Symptoms:
1. Ascaris pneumonia
2. Blockage of GI tract
3. Acute (fatal) peritonitis &/or blockage of bile/pancreatic duct

Diagnosed by eggs in feces of infected person

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10
Q

Ascaris lumbricoides & suum:
Life Cycle

A
  1. Eggs ingested by host
  2. Eggs hatch in small intestine
  3. Juveniles penetrate tissues of intestine & enter bloodstream
  4. Juveniles migrate to lungs & molt into 3rd stage juveniles
  5. 3rd stage juveniles migrate from pulmonary capillaries into alveoli
  6. “Coughed up” & swallowed
  7. Complete development into adults in small intestine
  8. Females produce eggs
  9. Eggs passed in host feces
  10. Juveniles within eggs mature to infective (2nd) stage
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11
Q

Toxocara canis & catti (hookworms)

A

Visceral larva migrans

Eggs from feces of infected dogs/cats ingested by human
- Hatch in intestine
- Can penetrate mucosa & enter circulation

Carried to:
- Liver
- Lungs
- Eyes
- Other organs

Cause inflammatory necrosis

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12
Q

Ancylostoma braziliense (hookworms)

A

Cutaneous larval migrans
- “Creeping eruption”
- Prevalent in tropical/subtropical countries & US

Filariform larvae in dog/cat feces infect humans
- Intestinal parasite of dogs/cats
- Contact with contaminated soil

Causes skin eruptions
- Migrates in skin (larvae move around)

Symptoms last 2-10 weeks (duration of larval persistence)

Prevention:
1. Treat pets
2. Wear shoes outside
3. Clean up after dogs/cats

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13
Q

Hookworms:
Life Cycle
(Necator spp. & Ancylostoma spp.)

A
  1. Infective juveniles penetrate skin
    - Migrate via blood to lungs (coughed up & swallowed)
  2. Juveniles enter small intestine
    - Attach to surface
    - Mature to adult forms
  3. Adult hookworms attach to lining of small intestine
    - Feed on blood
  4. Females produce eggs
    - Eggs passed in feces
  5. Eggs hatch in soil
    - Juveniles develop into infective (3rd) stage
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14
Q

Trichuris species (whipworm)

A

Live in large intestine
- Anterior end embeds in cells of lining

Can live long time
- Constant reinfection & heavy worm burdens

Symptoms:
1. Diarrhea
2. Dysentery
3. Anemia

Heavy worm infection in children lead to mental & physical retardation

Diagnosed by eggs in feces

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15
Q

Trichuris species:
Life Cycle

A
  1. Eggs ingested by host
  2. Eggs hatch in small intestine
  3. Juveniles migrate to large intestine
  4. Males & females reach sexual maturity & mate
  5. Adults in large intestine
  6. Eggs passed in feces
  7. Juveniles within eggs mature into infective juveniles
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16
Q

Dracunculus medinensis (Guinea worm)

A

Host infected by drinking water containing infected copepods (intermediate host)

Can live in body 1-2 years

Dies & causes little reaction if doesn’t reach skin

In superficial tissue:
- Liberates toxic substance that produces local inflammatory reaction (sterile blister)
- Worm lies beneath blister

Contamination of blister produces:
- Abscesses
- Cellulitis
- Ulceration
- Necrosis

Removal strategy = pour water on blister

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17
Q

Dracunculus medinensis:
Life Cycle

A
  1. Human drinks unfiltered water containing copepods with L3 larvae
  2. L3 larvae released when copepods die
    - Penetrate host’s stomach & intestinal wall
    - Mature & reproduce
  3. Fertilized female worm migrates to skin surface
    - Causes blister
    - Discharges larvae
  4. L1 larvae released into water from emerging female worm
    - Female worm begins to emerge 1 yr after infection
  5. L1 larvae consumed by copepod
  6. Undergoes 2 molts & becomes L3 larvae
18
Q

Filariae

A

Major blood & tissue parasites of humans
- Thread-like roundworms
- Belong to family Filarioidea

Spread by bite of arthropod

Adult filariae live in lymphatic tissue & give birth to prelarval forms (microfilariae)
- Microfilariae burrow through tissue & circulate in blood/lymphatic system
- Blocks lymphatics (swelling)

19
Q

Wuchereria bancrofti & W. (Brugia) malayi

A

W. bancrofti = Pacific islands & Africa
W. malayi = SE Asia

Transmitted by bite of infected mosquito
- Microfilariae mature into adults & mate in lymphatics of genitals/lower extremities
- Offspring enter nearby blood vessels

Symptoms:
1. Fever
2. Swollen lymph nodes
3. Elephantiasis (swelling of legs/genitals)

Elephantiasis
- Formation of fibrous tissue around dead filariae plugs up lymphatic system

20
Q

Wuchereria bancrofti:
Life Cycle

A
  1. Mosquito takes blood meal
    - L3 larvae enter human skin
  2. Adults in lymphatics
  3. Adults produce sheathed microfilariae
    - Migrate into lymph/blood channels
  4. Mosquito takes blood meal
    - Ingests microfilariae
  5. Microfilariae shed sheaths, penetrate midgut, & migrate to thoracic muscle
  6. L1 larvae
  7. L3 larvae
  8. Migrate to head & proboscis
21
Q

Onchocerco volvulus

A

River blindness (blinding filariasis)

Vector = female black fly

Onchocerciasis
- Nodular & erythematous lesions in skin & subcutaneous tissue
(chronic inflammatory response to infection)
- Microfilariae migrate through dermis, CT, & eye

22
Q

Loa loa (eyeworm)

A

Filarial infection that may lead to blindness

Vector = deer fly

Migrates under skin
(up to 1in every 2 min)

Swelling appears spontaneously
- Fugitive/Calabar swelling
- Persists 4-7 days & disappears

Usually no serious problems
- EXCEPT: passing through orbital conjunctiva or nose bridge

23
Q

4 Groups of Fungi
(based on sexual reproduction)

A
  1. Zygomycetes (zygospores)
  2. Basidiomycetes (basidiospores)
  3. Ascomycetes (ascospores)
  4. Deuteromycetes (or fungi imperfecti)
    - Sexual reproduction not observed
24
Q

4 Ways Fungi Cause Disease

A
  1. Allergic reaction (inhaling spores)
  2. Reaction to fungal toxin (mycotoxins)
  3. Mycoses (fungi grow in/on body)
  4. Economic impact (destroys food supply & leads to starvation)
25
Q

Superficial Mycoses

A
  1. Pityriasis versicolor (tinea versicolor)
  2. Tinea nigra
26
Q

Pityriasis versicolor (tinea versicolor)

A

Malassezia species

Chronic superfical fungal infection

Leads to hypo/hyper-pigmented patches on skin (do not tan in sunlight)

27
Q

Tinea nigra

A

Exophiala weneckii

Dark brown/black painless patches on soles of hands/feet

28
Q

Superfical Cutaneous Mycoses

A
  1. Dermaphytosis
    (normal skin = resistant to dermaphytes)
  2. Candida albicans
    (overgrowth of normal flora)
29
Q

Dermatophytosis

A

Excessive moisture allows invasion of keratinized layers of tissue
- Infection of hair, skin, nails

Caused by dermatophytes
(keratinophilic fungi of 3 specific genera):
1. Trichophyton
2. Epidermophyton
3. Microsporum

Dermatophytes produce keratinase
- Allow destruction of keratin
(byproducts used as nutrients)

30
Q

Dermatophyte Infections

A
  1. Tinea corpis (ringworm)
    - Mycoses of body
  2. Tinea capitis
    - Mycoses of scalp
  3. Tinea axillaris
    - Mycosis of underarm
  4. Tinea cruris (jock itch)
    - Mycosis of groin
  5. Tinea pedis (athlete’s foot)
    - Mycosis of foot
  6. Tinea unguium (onychomycosis)
    - Mycosis of nails
31
Q

Candida albicans

A

Overgrowth of natural commensal fungi (mainly located in GI tract)

  1. Oral thrush (mouth)
    - Heavy duty antibiotics
  2. Diaper rash (groin)
  3. Candida vaginitis (vagina)
32
Q

Subcutaneous Mycoses

A

Caused by saprophytic fungi
- Normal soil inhabitants

Enter following trauma to skin

Remain localized to subcutaneous tissue OR spread along lymphatics to local nodes
- See track (line)
- Local necrosis

  1. Sporothrix schenckii
  2. Phialophora & Cladosporium
33
Q

Sporothrix schenckii

A

Sporotrichosis
- Local pustule or ulcer with nodules draining lymphatics

Dimorphic fungus

Hazard for gardeners

34
Q

Phialophora & Cladosporium

A

Chromoblastomycosis
- Wart-like lesions with crusting abscesses extending along lymphatic system

35
Q

Systemic Mycoses by Dimorphic Fungi

A
  1. Coccidioides immitis
  2. Histoplasma capsulatum
  3. Blastomyces dermatitids
36
Q

Coccidioides immitis

A

Coccidioidomycosis (Valley Fever)
- Endemic in SW USA & Latin America (arid regions)
- Mild pneumonia/flu-like symptoms
(Often asymptomatic)

Dimorphic
- Mold in soil
- Spherule (containing endospores) in tissue

Transmitted via inhalation of arthrospores
- May spread from lungs to bones & CNS
- Dissemination more often in immunocompromised

Resolution of disease results in long-term immunity against reinfection

Johny Moore (SA spur infected & 2 yr treatment - ended career )

37
Q

Histoplasma capsulatum

A

Histoplasmosis (Spelunker’s Disease)
- Endemic in central & eastern states

Dimorphic fungus
- Mold in soil
(contaminated with bat/bird droppings)
- Yeast in tissue
(tuberculate macro or microconidia multiplying within macrophages)

Transmitted via inhalation of conidia (spore)

Mild respiratory symptoms
(often asymptomatic)

Spreads through body within macrophages
- Dissemination most often in immunocompromised

Small granulomatous foci of infection heals by calcification

38
Q

Blastomyces dermatitids

A

Blastomycosis
- SE USA & Ohio-MS River Valley area

Dimorphic fungus
- Mold in soil
- Yeast in tissue (broad-based bud)

Transmitted via inhalation of conidia

Symptoms:
1. Primary pulmonary stage
2. Chronic granulomatous disease
3. Dissemination may result in ulcerated granulomas of skin, bone, & other sites
4. Destruction of nasal passages

39
Q

Systemic “Opportunistic” Mycoses

A
  1. Cryptococcus (Filiobasidiella) neogormans
  2. Candida albicans
  3. Asperigillus fumigatus/flavus
40
Q

Cryptococcus (Filiobasidiella) neogormans

A

Cryptococcosis

Present in soil
- Pigeon droppings

Transmitted by inhalation of minimally encapsulated spores (basidiospores)

Usually asymptomatic or pneumonia

Can spread to CNS in immunocompromised
- Cryptococcal meningitis/meningoencephalitis

Most often occurs in individuals with suppressed cell-mediated immunity (ex: AIDS)

Virulence factors:
1. Capsule
2. Melanin production
3. Growth within macrophages

41
Q

Candida albicans

A

Normal flora (present in body)
- Upper respiratory tract
- GI tract
- Female genital tract

Occurs when local/systemic host defenses impaired
- Overgrowth of normal flora

Clinical presentation:
1. Thrush
2. Esophageal
3. Disseminated candidiasis (bloodstream infection)
4. Chronic mucocutaneous candidiasis

Diagnosed by pseudohyphae & germ tube formation

Vaccine studies underway at UTSA
- Dr. Jose Lopez-Ribot & Stepgen Saville (MBT laboratory)

42
Q

Asperigillus fumigatus/flavus

A

Aspergillosis

Exists ONLY as molds
- Soil, decomposing organic materials, fruits, nuts, grains

Occurs most often in neutropenic patients

Growth in pulmonary cavities
- Fungus ball
- Invades lungs & other organs

Allergic bronchopulmonary aspergillosis (ABPA)
- Fungal infection of the lung due to a hypersensitivity reaction to antigens of A. fumigatus

Aflatoxin production (A. flavus)

Microbiology (15 decks)

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