Pathogenic Protozoa I Flashcards by Joel Glotfelty

Includes Giardia and Trichomonas and their distant relatives Trypanosoma and Leishmania

Flagellates

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Amoeboid at one stage of its life cycle and flagellated at another, may be more closely related to flagellates than to other amoeboid organisms

Naegleria

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Includes Entamoeba (the cause of ‘amoebic dysentery’), Acanthamoeba, and Hartmanella

Amoebozoa

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What are the three types of alveolates?

-named for their cortical alveoli and flattened membrane-bound sacs

Apicomplexa, Cilliates, and Dinoflagellates

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Apicomplexa includes one of the most significant pathogens worldwide, the cause of malaria, which is called

Plasmodium

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Human apicomplexa pathogens are members of the class Sporozoa and most of the subclass Coccidia, so are sometimes called

Sporozoans or coccidia

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Includes the intestinal pathogen Balantidium and the familiar non-pathogen Paramecium

Ciliates

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Flagellated photosynthetic >algae=; cause >red tides= that kill marine organisms

Dinoflagellates

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Not known to cause human infections but secrete toxins which cause human illness either from direct exposure or from consumption of fish or shellfish which have fed on them

Dinoflagellates

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Tiny intracellular parasites which lack mitochondria

Microsporidia

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What are three other major groups of eukaryotes?

) Green algae, red algae, and plants
) Rhizaria or cercozoa
) Heterokonts

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Amoeboid organisms, many with elaborate shells

Rhizaria or cercozoa

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Made up of brown algae, diatoms, and their relatives, who, like Dinoflagellates, became photosynthetic via symbiosis not with bacteria but with eukaryotic algae

Heterokonts

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Organism used by another as a source of nutrition and protection

Host

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Organism that uses another as a source of nutrition and protection, with harm to the host

Parasite

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Organism that uses another as a source of nutrition and protection, without harm to the host

Commensal

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Organism in which a parasite replicates in nature, from which it is transmitted to humans

Reservoir

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Organism which transmits a parasite to humans; it may or may not be a host

Vector

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Host in which parasite undergoes sexual cycle (meiosis + fertilization)

Definitive host

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Host in which parasite multiplies asexually

Intermediate host

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Growing/multiplying form of a parasitic protozoan

Trophozoite

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Non-growing form, specialized for resistance to unfavorable environments and dispersal

Cyst

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Cells of a single species may take on different morphology at different stages of the life cycle. Some protozoa reproduce in an obligate cycle between two

Host species

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In this situation, forms produced by growth in the first host are

Infectious for the second

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Microscopic examination is often the key to diagnosis of

Protozoa infection

To check stool for protozoa, we perform an

O and P workup (Ova and parasites)

Unfixed "wet mounts" (unstained and stained with iodine) of fresh material to visualize live organisms

O and P workup

Called the "backpackers" diarrhea

Giardia lamblia

Infections acquired by consuming contaminated water

Giardia

Giardia multiplies in the lumen of the intestine; cells and cysts are shed in

Feces

Cells have two nuclei (giving them the appearance of a 'face' under the microscope) and a large ventral 'sucker disk' with which they adhere to the intestinal mucosa

Giardia

Acute or (in AIDS) chronic diarrhea. Organisms adhere to brush border

Giardia infection

The diarrhea seen in a giardia infection is from

Maladsorption

Sexually transmitted infection that multiplies on GU mucosal membranes

Trichomonas Vaginalis

Cells have a tuft of flagella at one end and an 'undulating membrane' which extends part-way down the cell

Trichomonas Vaginalis

In women, trichomonas vaginalis infection is typically limited to the

External genitalia, vagina, and cervix

Symptoms are itching or burning and a pale yellow, watery discharge; many infections asymptomatic

Trichomonas Vaginalis infection

Transmitted by insect vectors; multiply in both vector and host

Hemoflagellates

Produces bloodstream infections and multiply outside cells

Trypanosoma

Produce tissue infections and multiply intracellularly

Leishmania

Hemoflagellate cells are elongate, with a single flagellum which originates in a unique organelle called the

Kinetoplast

Visible as a dark short rod in stained cells

The kinetoplast

What are the four stages that a hemoflagellate goes through -Defined by the relative positions of the kinetoplast and nucleus, and the presence or absence of and flagellum and undulating membrane

Amastigote, Promastigote, Epimastigote, and Trypomastigote | Pneumonic "You don't want a hemoflagellate as A PET

Characterized by the central localization of the nucleus and kinetoplast -No flagellum

Amastigote

Has the kinetoplast at the anterior end of the cell - Flagellum is present - No undulating membrane

Promastigote

The kinetoplast migrates centrally -Has flagellum with short unulating membrane

Epimastigote

Has the kinetoplast at the posterior end of the cell -Undulating membrane extends the full length of the cell

Trypomastigote

What are the three types of Trypnosoma brucei

T. b. brucei, T. b. rhodesiense, and T. b. gambesiense

Causes the infection Ngana, a disease of wild or domestic ungulates

T. b. brucei

Rapidly-progressive human infections

T. b. rhodesiense

Slowly progressive human infections

T. b. Gambesiense

Multiply in the gut and salivary glands of the tsetse fly glossinia

Epimastigotes

Multiply in the bloodstream of mammals

Trypomastigotes

A localized inflammatory lesion; trypanosomes multiply at the site of the

Tsetse fly bite

The acute or bloodstream phase of disease can be long-lasting and is characterized by the signs and symptoms of chronic inflammation: fever, headache, muscle/joint pains, rash, anemia, leukocytosis, weight loss, enlarged lymph nodes, elevated ESR

Trypanosoma brucei

Enlarged posterior cervical lymph nodes are called

Winterbottom's sign

Chronic or late stage african trypanosomes disease with invasion of the CNS. It progresses through lassitude, motor and reflex abnormalities, stupor, coma, and

Death

African trypanosomes evade the immune system by

Phase variation

The outer surface of bloodstream forms is covered with a single protein, the

Variable Surface Glycoprotein (VSG)

The genome contains 1-2 expressed copies of the VSG gene and several thousand silent copies which encode

Antigenically distinct forms

The form transmitted to humans by insect vectors occurs in a single

Antigenic state

As the immune system reacts to this antigen and begins to destroy trypanosomes, a rare recombination event between a silent copy and an expressed copy results in production of an entirely new antigenic form of the

VSG

In an experimental animal trypanosomes have been followed through many waves of parasitemia, each characterized by a distinct

Surface antigen

IgM levels in an infected person may be

20x normal

American trypanosomiasis or Chagas disease

Trypanosoma cruzii

Forms at the site of infection, with regional lymphadenitis as the organisms spread

Primary lesion from T. cruzii

The primary lesion may be transferred to the conjunctiva if the eye is rubbed with a contaminated finger, resulting in unilateral swelling of the eyelids. This is called

Romana's sign

Multiply in the gut of the nocturnal, blood-sucking bug triatoma

Promastigotes

Multiply intracellularly, initially in muscle

Amastigotes

Characterized by fever, lymphadenopathy, enlargement of liver and spleen

Acute T. cruzii

Characterized by invasion of the heart, leading to cardiac dysfunction, and /or the CNS, especially autonomic ganglia of abdominal viscera, leading to smooth muscle dysfunction and esophageal or intestinal enlargement

Late T. cruzii disease

T. cruzii infection is diagnosed by

Seroconversion or muscle biopsy

Leishmania causes visceral and muco-cutaneous infectrions. It is transferred via the

Sandfly

Produce visceral Leishmaiansis or Kala-Azar as a result of multiplication in liver, spleen, lymph nodes, bone marrow, and other tissues

L. donovani and L chagasii

Amastigotes from these species in tissue are termed

Leishman-Donovan (LD) bodies

Widespread dermotropic Leishmanias cause ulcerative dermal lesions at the site of

Infection

A classic site for these ulcerative dermal lesions in the

Back of the neck (chiclero ulcer)

Lesions are often localized but may spread, or there may be granulomatous

Satellite lesions

Spreads from a cutaneous site of infection to the mucous membranes of the oral or nasal cavity and may remain latent there for years or decades, eventually to produce a spreading destructive lesion

L. braziliensis

These lesions from L. braziliensis are called

Espundia

Amoebas and Amoeboflagellates cause

Amoebic dysentery

The life cycle and epidemiology of Amoebas and Amoeboflagellates starts with the ingestion of -From contaminated water or food

Cysts

In the colon cysts develop into -Multiply and produce more cysts which are excreted in feces

Amoeboid trophozoites

Trophozoites of E. histolyica are larger than those of other species and contain ingested

RBC's rather than bacteria

Differentiation of cysts relies on size and shape, number of nuclei, and presence or absence of a large

Glycogen inclusion

Cysts of E. histolytica are round, medium sized, don't have much glycogen, and have

4 nuclei

Amoebas invade the intestinal epithelium wall at the base of a crypt, producing a small

Ulcer

They penetrate the muscularis mucosa and spread laterally to produce a flask-shaped

Necrotic lesion

Ulcers contain trophozoites; amoeboid cysts are formed only in the

Intestinal lumen

Caused by free-living amoebas of several genera: Naegleria, Hartmanella, Acanthamoeba. Infection usually results from swimming in natural waters

Amoebic Meningoencephalitis

In amoebic meningoencephalitis, amoebas enter the nose and sinuses and pass into the brain through the

Cribiform plate

Have been successfully used to treat Amoebic Meningoencephalitis

Amphotericin and azoles

Causes severe keratitis; some cases resulted from use of contact lens solution made with contaminated water

Acanthamoeba

Some dinoflagellates (photosynthetic protozoa) produce potent

Toxins

These can cause human and/or animal disease, contracted by contact with or consumption of organisms such as shellfish which have fed on these

Dinoflagellates

Has caused massive kills of fish -Before its toxigenic properties were recognized it caused serious neurological poisoning among laboratory workers

Pfeisteria piscidida

Causes intestinal disease similar to that produced by E. histolytica

Balantidium coli

Trophozoites of B. coli are very large, with an indented feeding apparatus at one end and a large kidney-shaped

Macronucleus

Motion in wet mounts is smooth translation with rotation around the long axis of the cells. -Cysts are large and round

B. coli

Named for the apical complex used to infect host cells

Apicomplexa