Exam 1 Flashcards
Container for Stool specimens must be free of:
urine, water, other potential contaminants
Preservation Protocol for Stool Specimens
no preservation if processed within two hours PVA fixative or formalin if over 2 hours
Temperature for Stool Specimens
ALWAYS AT ROOM TEMPERATURE
Number of specimens for Stool sample
one initially, 2 if symptoms persist & more than three after a ‘purge’
Times of collection for Stool specimens
collected within 10 days; one sample every other day
Stages of protozoan found in Formed stool
most likely cysts, larvae, and eggs NO TROPHOZOITES
Formalin Advantages
good for preservation of CYSTS
preserves organisms w/o compromising organism morphology
Formalin Disadvantages
DESTROYS TROPHOZOITES
PVA Advantages
can be used for transporting specimens!
excellent at preserving CYSTS, TROHPOZOITES, FLAGELLATES etc
PVA Disadvantages
Giardia and Trichomonas don’t concentrate well in PVA Isopora, if present, not usually seen
Sedimentation
uses gravity or centrifugation contains more fecal debris contain a ^^ # of diagnostic forms of parasite Giardia lamblia may be missed
Flotation
yields much cleaner prep than Sedimentation
must be examined immediately
not an acceptable method for recovery of operculated eggs
cysts may become distorted if in prep for prolonged period
Saline Procedure
O.85% NaCl
protozoan cysts are more refractile & can see troph motility!
Iodine Prep
D’Antoni’s Iodine or Lugol’s iodine 1:5 dilution
acts as a stain to improve detection & ID of protozoan **cysts; Trophs will be destroyed **& immobilized
best for ID of cysts
Purpose of the trichrome stain
definitive diagnosis of protozoan; easiest staining procedureto detect & ID protozoan
What observations should be noted in a stool when examining for the presence of parasites?
Blood, Mucous, & Consistency!
Entamoeba histolyica cyst
Pathogen!!
12-15um; never more than >4 nuclei!!!!
small central karyosome; even bead-like distribution of chromatin along inner nuclear membrane
chromatidal bars are rounded!!!!

Entamoeba histolytica trophozoite
15-20 um
unidirectional motility!
INGESTION OF RBCs!!
single pseudopod; fine granular cytoplasm

What is the most important differentiating characteristic for intestinal protozoan
structure of the nucleus!
Entamoeba coli cyst
non pathogen
spherical, UP TO 8 NUCLEI!! - each large w/ central karyosome
chromatoidal bars are splintered w/ pointed ends

Entamoeba coli trophozoite
non pathogen
relatively large; cytoplasm is usually junky - filled w/ food vacuoles
pseudopods are exteded in many directions- slow, non-directional motility
Endolimax nana
non pathogen
very small- both cyst & troph
2 unique features of Iodamoeba butschlii
LARGE, GLYCOGEN VACUOLE
stains brown in iodine prep

Entamoeba histolytica geographic distribution
EVERYWHERE
fecal-oral route of infection
Acanthamoeba causes:
associated w/ granulomatous amoebic encephalitis
more commonly associated w/ KERATITIS!- contaminated contact lense solution & swimmin pools
naegleria causes:
Primarily amoebic meningoencephalitis!!! (PAM)
mostly in children & young adults swimming in polluted fresh water
see motile trophs in spinal fluid
cyst definition
inactive stage! dormant & able to survive adverse environmental conditions
reproductive division
1-8 nuclei
trophozoite definition
actively motile
feeding stage
single nucleus; except! Giardia & Dientamoeba fragilis
Cryptosproidium parvum
very small! 5um
acid-fast stain
located on superficial brush border of intestines
Isospora belli
usually nonpathogenic except in HIV patients
sexual & asexual forms in intestine
can complete life cycle w/o separate host
Cyclospora
non pathogenic except in HIV patients
similar to cryptosporidium parvum but larger
also acid-fast stain
Blastocystis hominis
nonpathogenic except in HIV patients
>5 organisms per low power field are reported
recurrent diarrhea is most common symptoms
Why should the presence of the non-pathogens always be reported?
implies contact w/ feces & should look for other indicators of contamination & can flag E. histolyica being present
Giardia lamblia cyst
10-15 um oval/elliptical
thin smooth wall
4 nuclei in mature form!

Giardia lamblia trophozoites
10-20 um
PEAR SHAPED
motile via 4 pairs of flagella - ‘falling leaf motility’
2 NUCLEI!

Dientamoeba fragilis cyst
AH HA! NO CYST FORM!
Dientamoeba fragilis trophozoite
significant if seen in children
2 nuclei!!! karyosome consists of cluster of small granules
motile via pseudopod
cytoplasm-finely granular
Chilomastix mesnili
not really important but is lemon-shaped!
Trichomonas hominis
not really that important; nonpathogen
NO CYST form
pear-shaped w/ single anterior nucleus
Clinical significance of Dientamoeba fragilis?
children - significant pathogen: fatigue, failure to thrive, diarrhea, abdominal pain, anorexia, nausea
adults- usually asymptomatic
Infective stage of Giardia lamblia?
mature cyst!
4 Structural characteristics of Balantidium coli that separate ciliate from flagellates
- large trophozoites - up to 100 um
- cilia cover the surface
- bean-shaped macronucleus & micronucleus
- boring motility
only cilia thats pathogenic to humans
reservoir - hogs
Diagnosis for Giardia
Entero-Test for giardia antigen!
Macronucleus & mirconucleus
macro- large, kidney-bean shaped nucleus
micro- small, dot like cluster of nuclear material; difficult to see
both present in Balantidium coli
Clinically significant flagellates & ciliates
Giardia lamblia
Dientamoeba fragilis-children
Trich. vaginalis
Giardia lamblia pathology of infection important notes
diarrhea, abdominal cramps, bloating, malabsorption
NOT INVASIVE
Trichomonas vaginalis picture ID & diagnosis
seen in vaginal preps; always observe in fresh specimens

Taenia saginata
BEEF TAPE WORM!
ovum: 35-50um; spherical w/ a thick, striate, smooth shell & contain a hexacanth embryo
adult: Unarmed!! 4 suckers; proglottids have 13+ lateral uterine segments

Taenia solium
PORK TAPE WORM
same eggs as taenia saginata
adults: ARMED scolex; proglottids have 7-13 lateral uterine segments
Hymenolepis nana
DWARF TAPE WORM
adult worm has proglottids that are wider than they are long
ellipical ovum w/ thin outer shell w/ 4-8 filaments extending into open space
Diphyllobothrium latum
FISH TAPE WORM
large, oval ovum
adult worm: almond shaped, creates a vitamin B12 deficiency (via competitive consumption) & can lead to megaloblastic anemia

Intermediate host infection w/ Taenia solium?
cysticerosis - an infection of both pig & human from the worm’s larval stage
can invade the tissuess –> VERY DANGEROUS
Echinococcus granulosus
DOG TAPE WORM
transmitted by food & water containing eggs
Proglottid
egg producing segments which has both male & female sexual organs
hydatid cyst
larval stage in the life of Echinococcus granulosus; consisting of a germinal membrane from which daughter cysts develop, contained within a fluid filled bladder

2 organisms whos egg stage may be mistaken for Taenia saginata
- Ascaris lumbricoides
- hookworm