MMSC428 Final Exam Content

Commensalism

the organisms benefits bu there is not beneficial or harmful effect on the host

Mutualism

both organism and host benefits from one another

Parasitism

the organism benefits at the expense of the host - host is injured through the activities of the organism

Obligate parasite

an organism that depends completely on its host for reproduction and survival - will die without host

Facultative parasite

can exist in a free living state or as a commensal and under the right circumstances may become parasitic

Ectoparasite

parasite living on body surfaces of the host like ticks or lice

Endoparasite

parasite living within the host like malarial parasites

Definitive host

supports life or sexual reproduction of parasite

Intermediate host

host supports immature or non-reproductive form, unable to move on past host - dead end

Protozoa

intestinal and extraintestinal infections, amebae, flagellates, ciliates, sporozoans

Amebae

pseudopodia motilita, trophozoite form, feeding and replicating cyst form, mature and infection form, asexual

Flagellates

flagellar motility, asexual

Ciliates

cilia motility, asexual

Sporozoans

host tissue and RBC, asexual or sexual reproduction

Helminths

worms, intestinal and extraintestinal infections, nematodes, cestodes, trematodes

Nematodes

roundworms

Cestodes

tapeworms, trematodes: flukes, think aquatic

Mechanisms of damage parasites

invasion, toxin secretion, mechanical damage, deprive host of vita nutrients, hypersensitivity reaction to parasite proteins, eosinophilia Assess the significance of parasitic infections: Prevalent in topical and underdeveloped countries, major cause of morbidity and mortality

Big 3 US

Trichomonas vaginalis, Giardia lamblia, Cryptosporidium

Infrequent in US

temperate zone, sanitation procedures

Stool specimens for O and P exam

3:1 preservative to stool ratio, 3 24-48 hours apart over 7-10 days, no formed stool, only loose or watery stool

Zinc Polyvinyl alcohol

permanently stained smears

10% formalin

direct wet mounts, concentration, antigen detection

Single-vial

all tests

O and P exam

ova and parasite, gold standard for intestinal parasite exams, concentrated wet mount, permanently stained smear

Stool O and P exam procedure

macroscopic examination, direct wet mounts (unconcentrated)

Concentrated wet mount

for detection of larvae, centrifuge and resuspend, positive yellow Lugol's iodine is a parasite, ideal for larvae, eggs, ova of helminths

Permanently stained smear

with trichrome stain, is a modified acid fast stain, good for morphological dx of parasite (trophozoite and cyst form)

Blood specimens

for plasmodium usually, finger stick or whole blood with EDTA, permanently stained smears with Giemsa or Wright's stain

Eosinophilia

#1 job of eosinophils is to fight parasites, increased peripheral eosinophils, major basic protein in granules kills parasite but also causes inflammation

Diagnostic of giardia

microscopy, duodenal aspirate or string test, stool antigen (now gold standard for this), PCR

Giardia duodenalis/lamblia Appropriate clinical specimen

duodenal aspirate, stool

Giardia duodenalis/lamblia Morphology of diagnostic stage(s)

cysts are 8-14 𝜇m, 2-4 nuclei, trophs are 10-20 𝜇m, 2 nuclei, 4 pairs of flagella

Giardia duodenalis/lamblia Disease(s) caused, if any

Beaver fever, Backpackers diarrhea, attaches to lining of intestinal mucosa with ventral sucking disk, asymptomatic to severe diarrhea and malabsorption, chronic diarrhea and weight loss

Dientamoeba fragilis Morphology of diagnostic stage(s)

lacks external flagella and therefore must be morphologically differentiated from the small nonpathogenic amebae

Dientamoeba fragilis Disease(s) caused, if any

asymptomatic usually, but colitis, appendicitis, or IBS like sx

Chilomastix mesnil Morphology of diagnostic stage(s)

troph is 6-24 𝜇m, pear shaped, single large nucleus at anterior end, cyst is 6-10𝜇m, lemon shaped

Chilomastix mesnili Disease(s) caused, if any

nonpathogenic

Pentatrichomonas hominis Morphology of diagnostic stage(s)

no cyst stage, 6-20 𝜇m troph

Pentatrichomonas hominis Disease(s) caused, if any

nonpathogenic

Entamoeba coli Morphology of diagnostic stage(s)

cysts usually spherical but may be elongated and measure 10-35 µm, mature cysts typically have 8 nuclei but may have as many as 16 or more

Entamoeba coli is the only Entamoeba species

found in humans that has more than four nuclei in the cyst stage

Entamoeba coli Disease(s) caused, if any

nonpathogenic

Entamoeba histolytica Appropriate clinical specimen

stool antigen detection or PCR multiplex, microscopy

Entamoeba histolytica Morphology of diagnostic stage(s)

trophozoite form has single nucleus with small/central karyosome - 15-25𝜇m/ingested RBCs in trophozoite, cyst form has 4 nuclei, and chromatoidal bar - 12-15 𝜇m

Entamoeba histolytica Disease(s) caused, if any

true pathogen, most severe intestinal protozoan infection, ability to cause invasive infections from hematogenous spread, liver and lung abscesses

Entamoeba dispar Disease(s) caused, if any

nonpathogenic - identical morphologically to E. histolytica

Entamoeba moshkovskii Disease(s) caused, if any

nonpathogenic - identical morphologically to E. histolytica

Entamoeba hartmanni Disease(s) caused, if any

nonpathogenic, smaller than E. histolytica

Endolimax nana Disease(s) caused, if any

nonpathogenic

Entamoeba polecki Disease(s) caused, if any

nonpathogenic, troph is 10-25 𝜇m, cyst is 9-25 𝜇m, large nucleus and numerous chromatoidal bars

lodamoeba bütschlii Morphology of diagnostic stage(s)

nonpathogenic, large karyosome, no peripheral chromatin, troph is 8-20 𝜇m, 5-20 𝜇m - large glycogen vacuole

Balantidium coli Morphology of diagnostic stage(s)

cyst 40-70 𝜇m, bean-shaped macronucleus, and a micronucleus

Balantidium coli Ciliated troph

40 by 60 wide and 40-200 𝜇m long, contains a cytostome, also a bean-shaped macronucleus

Balantidium coli Disease(s) caused, if any

most cases are asymptomatic, clinical manifestations, when present, may be acute or chronic with abdominal symptoms

Blastocystis hominis Morphology of diagnostic stage(s)

vacuolar form of 8-10 𝜇m, contains central vacuole, surrounded by thin rim of cytoplasm containing up to six nuclei

Cystoisospora belli Morphology of diagnostic stage(s)

25-30 𝜇m oocyst, 1-2 sporoblasts, autofluorescence with UV microscopy, modified acid fast staining

Cystoisospora belli Disease(s) caused, if any

asymptomatic or mild infection, severe in immunocompromised like weight loss, dehydration, malabsorption

Microsporidium Appropriate clinical specimen

intestinal specimens of stool, sputum, BAL, tissue biopsy, CSF, conjunctival scrapings, urine sediment

Microsporidium Morphology of diagnostic stage(s)

unicellular intracellular parasites, produced resistant spored of 1-4 𝜇m with chitin in spore wall, chromotrope 2R (stains spore and spore wall pink/red) - chemifluorescence agents (calcofluor white, binds to chitin in spore wall)

Microsporidium Disease(s) caused, if any

OIP, infect immunocompetent individuals, severe in IC, post organ transplant, 4-8 stools per day with N/V/D of relapsings sx

Microsporidium Site of infection

GI tract, eyes, CNS, liver, muscle, kidneys

E. histolytica from E. coli

E. histolytica has RBC inclusions, E. coli has large number of nuclei and glycogen vacuole in cysts

Charcot Leyden crystals

spindle shaped crystals, eosinophilic granules just indicates ANY parasite - E. histolytica

One chromatoidal bar in

cyst form of E. histolytica

No peripheral chromatin

in E. nana, I. bütschlii

Numerous chromatoidal bars

in E. polecki

Evaluate the significance of finding a glycogen vacuole in an intestinal amebae

Positive for E. coli, Positive for Iodamoeba bütschlii

E. dispar difference from E. histolytica

nonpathogenic and different zymodeme (isoenzyme) patterns, examine trophozoites for ingested RBCs, antigen detection, PCR

E. moshkovskii

nonpathogenic, morphologically identical to E. histolytica and E. dispar, only PCR is differentiation

E. hartmanni

nonpathogenic, similar to E. histolytica but smaller, with ½ size smaller, troph is 5-12 𝜇m and cyst is 5-10 𝜇m

E. coli

nonpathogenic, similar to E. histolytica but larger, troph is 15-50 𝜇m, cyst is 10-35 𝜇m

E. nana

nonpathogenic, troph has large karyosome and no peripheral chromatin, tropic is 6-12 𝜇m, cyst is 5-10 𝜇m

Explain the course of infection and clinical significance of detecting Blastocystis hominis

Usually asymptomatic, symptomatic infection in Blastocytosis, GI sx like diarrhea, abdominal pain, bloating and flatulence, pathogenesis depends on subtype of blastocystis

Describe the pathogenesis and course of infection with Balantidium coli

Most asymptomatic, acute or chronic abdominal sc, diarrhea or dysentery, extraintestinal infection rare - peritonitis, liver abscesses, intestinal perforation or rupture of fulminant colonic ulcers

Name the reservoir host for B. coli

Pigs are natural host, humans are accidental host

Discuss characteristic properties of B. coli including cilia, number of nuclei, and type of nuclei

Two nuclei, large size of 40 𝜇m to 200 𝜇m, presence of cilia on cell surface, bean shaped macronucleus with a smaller micronucleus

Giardia lamblia

Pear/teardrop-shaped, 2 nuclei, present cystostomy, present sucking disc, absent undulating membrane, cyst stage present

Dientamoeba fragilis

Irregular/round shape, 1-2 nuclei, absent cystostomy, absent sucking disc, absent undulating membrane, cyst stage absent or rare

Pentatrichomonas hominis

Oval/pear-shaped, 1 nucleus, present cystostome, absent sucking disc, present undulating membrane, cyst stage absent

Chilomastix mesnili

Pear/lemon-shaped, 1 nucleus, present cystostome, absent sucking disc, absent undulating membrane, cyst stage present

Giardia lamblia trophozoites

Reside primarily in the duodenum and upper small intestine of the host.

Evaluate the types of specimens used to recover G. lamblia from humans

Stool, Duodenal aspirate, String test

Giardia lamblia motility

demonstrates a falling leaf motion, moves in a slow, oscillating manner

Identify the reservoirs for G. lamblia and where the parasite is found in the environment

Reservoirs - humans, animals like beavers, dogs, cats, Environment - contaminated water, soil, fomites, in warm environments

Describe the pathogenicity of Dientamoeba fragilis and how to detect this parasite

Pathogenesis is asymptomatic or symptomatic - usually children with pinworm (symbiosis), 5-15 𝜇m, no cyst, 80& binucleate, 20% uninucleate

Propose reasons for the increased risk for infection with Cryptosporidium seen in specific patient subpopulations

Suppression of immune system (HIV, AIDS, chemotherapy, corticosteroids)

Discuss how to diagnose Cryptosporidium infections in humans

Microscopy with Auramine rhodamine, Modified acid fast stainings to see oocysts of 4-6 𝜇m in size

Cryptosporidium has a oocyst of

4-6 𝜇m in size

Cryptosporidium modified acid fast staining

positive

Cryptosporidium UV autofluorescence

negative

Cryptosporidium auramine-rhodamine

positive

Cyclospora has a oocyst of

8-10 𝜇m in size

Cyclospora modified acid fast staining

positive

Cyclospora UV autofluorescence

positive

Cyclospora auramine-rhodamine

negative

Discuss the course of infection and clinical significance of Cyclospora

Infection from ingestion of infective oocysts, similar life cycle to Cryptosporidium BUT asexual and sexual reproduction occurs inside host intestinal cells, and oocyst sporulation occurs in environment after excretion

Evaluate the techniques available for the diagnosis of Cyclospora infection

Other common stains including Giemsa and trichrome are not adequate for the reliable detection of Cyclospora - single negative stool specimen does not rule out the diagnosis; three or more specimens at 2- or 3-day intervals may be required

Discuss the course and clinical significance of microsporidian infection

Cases are also known to occur in immunocompetent individuals, Disseminated infection can be fatal - usually immunocompromised

Compare the methods available to diagnose microsporidian infection

Uses modified trichrome or chromotrope 2R stains to detect spores in stool or tissue, appear as small (1-5 μm) - larger in Cyclospora, oval, red-pink bodies with a clear vacuole