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Microbiology > Parasitology Exam 1 > Flashcards

Parasitology Exam 1 Flashcards

1
Q

Symbiosis

A

Any close/long term interaction between two organisms of different species

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2
Q

Commensalism

A

one organism benefits and the other is neither benefitted nor harmed

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3
Q

Mutualism

A

All species involved benefit

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4
Q

Parasitism

A

Parasite dependent on host and benefits, while host harms

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5
Q

What are the 3 main classes of parasites that can cause disease in humans?

A

Protozoa
Helminths
Ectoparasites

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6
Q

What is the Domain of parasites?

A

Eukaryotes

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7
Q

What are the 2 kingdoms of parasites?

A

Protista and Animalia

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8
Q

What is the subkingdom of Protista?

A

Protozoa

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9
Q

Protozoa: unicellular or multicellular

A

unicellular

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10
Q

What is the subkingdom of Animalia?

A

Metazoa

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11
Q

Are metazoa multicellular or unicellular?

A

Multicellular

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12
Q

What phylums are in the subkingdom protozoa?

A

Mastigophora (flagellates)
Sarcodina (amoebae)
Ciliophora (ciliates)
Sporozoa

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13
Q

What phylums are in the subkingdom metazoa?

A

Platyhelminthes (flat worms)
Nemathelminthes (round worms)

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14
Q

Platyhelminths = ______ worms? What classes does platyhelminth include?

A

Flat worms
Cestoda (tape worms)
Trematoda (flukes)

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15
Q

Trematoda

A

Flukes

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16
Q

Cestoda

A

Tape worms

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17
Q

Platyhelminths

A

Flatworms (flues and tapeworms)

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18
Q

Nemathelminthes

A

Round worms

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19
Q

What class is included in the phylum nemathelminthes?

A

Nematoda (round worms)

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20
Q

Protozoa vs metazoa

A

protozoa: unicellular, able to multiply in humans, binary fission

metazoa: multicellular, cannot multiply in humans in adult form, sexual reproduction

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21
Q

Platyhelminths vs nemathelminthes?

A

Platyhelminth = flat worm
Nemathelminthe = round worm

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22
Q

Key characteristics of protozoa

A
  • Unicellular
  • Able to multiply in humans
  • Can be intestinal or infect blood/tissue
  • Reproduce asexually (binary fission)
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23
Q

Key characteristics of Helminths

A
  • Multicellular
  • Cannot multiply in humans in their adult form
  • Sexual reproduction
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24
Q

Key characteristics of ectoparasites

A
  • Arthropods that establish on the body surface of the host
  • Can have 4 or 3 pairs of appendages (Arachnida and Insecta, respectively)
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25
Q

Which type of host shelters an organism which does not usually parasitize that host, not allowing transmission to the definitive host?

A

Accidental host

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26
Q

Which type of host is where sexual reproduction of a parasite takes place, and the host that harbors the adult parasite?

A

Definitive host

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27
Q

Which type of host is in which a parasite develops but does not reach sexual maturity, and the host that harbors asexual forms of the parasite?

A

Intermediate host

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28
Q

Which type of host harbors the parasite but produces no symptoms, and serves as a source of infection for humans?

A

Reservoir host

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29
Q

Which type of host is a carrier in which the organism remains alive, but does not develop or multiply, and is not necessary for the parasite’s development cycle?

A

Transport (paratenic) host

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30
Q

What is an organism that does not cause disease itself, but carries and usually transmits parasites and diseases from one host to another, usually an arthropod, and is essential for the completion of the life cycle?

A

Vector

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31
Q

Diagnostic stage of a parasitic infection

A

Developmental stage of a pathogenic organism that can be detected in human specimens

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32
Q

Infective stage of a parasite

A

Stage where the parasite is capable of entering and continuing development within the host, required part of the life cycle for that parasite

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33
Q

Facultative parasite

A

Organism that may survive in the absence of a host but occasionally infects a host organism

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34
Q

Obligate parasite

A

Organism that cannot complete its life cycle without a host, cannot survive without a host

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35
Q

Overall, which populations are more affected by parasitic infections?

A

Poor and underdeveloped countries in tropical/subtropical regions (warm climates)

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36
Q

What are the WHO’s top 5 most harmful parasitic diseases?

A

Malaria
Leishmaniasis
Trypanosomiasis
Onchocerciasis
Schistosomiasis

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37
Q

What safety precautions should be followed when handling parasitology specimens?

A

Biosafety Level 2
Proper PPE, biological safety cabinets, decontaminate, proper disposal, etc

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38
Q

How should stool specimens be preserved?

A

10% formalin and PVA (1:3 ratio of stool to preservative)

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39
Q

When can fresh stool samples be examined?

A

Immediately

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40
Q

When should stool samples be preserved? What ratio of stool to preservative?

A

ASAP; 1 volume of stool to 3 volumes of preservative

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41
Q

If stools are a type 7 (LIQUID) what would you see more of: trophs or cysts?

A

Trophs

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42
Q

If stools are a type 1 (SOLID) what would you see more of: trophs or cysts?

A

Cysts

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43
Q

Bristol stool chart type 1 vs type 7

A

type 1: solid
type 7: liquid

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44
Q

What are the two main preservatives for stool?

A

PVA and 10% formalin

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45
Q

What is the collection procedure for a parasitology stool specimen?

A

3 specimens passed at intervals of 2-3 days should be examined (3 specimens over 10 days)

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46
Q

How long do you have to examine liquid fresh stool specimens? (no preservative)

A

Within 30 minutes of passage

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47
Q

How long do you have to examine soft fresh stool specimens? (no preservative)

A

Within 1 hour of passage

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48
Q

How long do you have to examine formed fresh stool specimens? (no preservative)

A

Up to one day (24 hours) with overnight refrigeration

49
Q

What does a fresh specimen permit? (what is a benefit)

A

Permits observation of motile trophozoites but must be carried out without delay

50
Q

What is the purpose of concentration procedures for stool specimens?

A

Separates parasites from fecal debris to increase chances of detecting parasitic organism

51
Q

What is the flotation technique?

A

A concentration method that uses solutions with higher specific gravity than organism, so organism floats to the top

52
Q

What is the sedimentation technique?

A

A concentration method that uses solutions with lower specific gravity than organism, so organism settles to the bottom

53
Q

Example of flotation technique

A

Zinc sulfate and Sheather’s sugar

54
Q

Example of sedimentation technique

A

Formalin-ethyl acetate technique

55
Q

What specimens, preserved in 10% formalin, can a wet mount be performed on?

A

Protozoa and helminths

56
Q

What specimens, preserved in 10% formalin, can an ELISA be performed on?

A

Giardia and cryptosporidium

57
Q

What specimens, preserved in 10% formalin, can a chromotrope stain be performed on?

A

Microsporidia

58
Q

What specimens, preserved in PVA, can the trichrome stain be performed on?

A

Protozoa

59
Q

What preservative is required for the trichrome stain?

A

PVA

60
Q

What preservative allows you to perform the sedimentation technique (formalin-ethyl acetate) on various organisms for more specific tests?

A

10% Formalin

61
Q

What organisms can be safranin stained to test?

A

Cyclospora

62
Q

What organisms can you perform a DFA on?

A

Giardia and cryptosporidum

63
Q

What organisms can you perform an acid fast stain on?

A

Cryptosporidum and cyclospora, and isospora

64
Q

What additional tests does the formalin-ethyl acetate concentration allow you to perform?

A

DFA, safranin stain, direct mount, acid fast stain, wet mount

65
Q

T/F: blood specimens should be collected after treatment is initiated

A

False (before)

66
Q

Why are multiple smears required for parasitic blood specimens?

A

Parasitemia may fluctuate for babesia and malaria

67
Q

What type of parasite has marked periodicity depending on the species?

A

Microfiliariae

68
Q

What is the purpose of the chromotrope stain, and what type of preservative is used?

A

Differentiate microsporidia spores
10% formalin

69
Q

What is the purpose of the modified acid-fast stain, and what preservative is used?

A

ID oocyts of cyclospora, cryptosporidium, cystoisospora (fresh or formalin-preserved)

70
Q

What is the purpose of the safranin stain and what preservative is used

A

ID oocysts of cyclospora, cryptosporidium, cystoisospora
Fresh or formalin-preserved

71
Q

What is the purpose of the trichrome stain and what preservative is used

A

ID of cysts and trophozoites of intestinal protozoa
Fresh stool or PVA

72
Q

What are the rules of blood parasite collection?

A
  • 2 thick and 2 thin smears must be made
  • Must make smears within 1 hour of collection of EDTA specimen
73
Q

What does a thick smear allow for? What does it not allow for?

A

More efficient detection of parasites - quicker to tell if they are present or not because it is more concentrated
Does not allow for species ID

74
Q

What does a thin smear allow for?

A

Allows for parasite ID and detection

75
Q

How is a thin smear made vs a thick smear?

A

Thin smear: Wright-Giemsa stain on Midas like normal

Thick smear: 1 ml of Giemsa stain to 50 mL of XPR plus Buffer (AlphaTec) - stain for 45 min and must air dry for a long time (can not use heated drying rack)

76
Q

How does a thin smear look different than a thick smear under the microscope?

A

Thin smear will look like a normal blood smear, can see individual RBC
Thick smear will not be able to see RBCs, just organisms if they are present

77
Q

When is a stereoscopic microscope used for parasitic examination?

A

Recommended for larger specimens (arthropods, tapeworms)

78
Q

What is the purpose of a stage (ocular) micrometer?

A

Must be used for final ID, allows microbiologist to determine the exact size of the parasitic element

79
Q

When is a brightfield microscope used in parasitic exam?

A

Always used first

80
Q

What is the gold standard to ID parasites?

A

Microscopic examination

81
Q

What is the purpose of using a wet mount for stool specimens?

A

ID of protozoan trophozoites, cysts, oocysts, and helminth eggs and larvae

82
Q

What is the purpose of using stained slides for stool specimens?

A

ID of protozoan trophozoites and cysts and for confirmation of species

83
Q

What is the purpose of using UV fluorescence for stool specimens?

A

Enhanced demonstration of Cyclospora oocysts

84
Q

Procedure for examining stool specimen stained slides

A

Must examine 200-300 fields at 100x

85
Q

Procedure of wet mount examination of stool specimen

A
  • Two smears prepared on one slide, one stained with iodine
  • Place coverslip over each smear
  • Thickness should be able to read newsprint through specimen
  • Scan entire coverslip area at 10x, if anything suspicious use a higher magnification
86
Q

What will Cyclospora oocysts look like under UV fluorescence microscopy?

A

Blue circles

87
Q

List 3 microscopic tests that can be performed on a stool specimen

A

Wet mount
Stained slide
UV fluorescence

88
Q

What do you result if you dont see any parasites on a blood smear?

A

NPF (No parasites found)

89
Q

Allowed specimens for parasititic blood tests

A
  • Whole blood w/ no anticoagulant
  • Anticoagulated whole blood
  • Sediment from concentration procedures
90
Q

Two most commonly used stains for blood specimens

A

Wright’s and Giemsa

91
Q

Blood film for parasitic exam is always _______.

A

STAT

92
Q

Rules for examination of thin/thick blood smears

A

2 of each made
Minimum of 300 fields on BOTH must be examined before reported smear as NPF

93
Q

What do you do when you see a parasite on a thin blood smear?

A

Identify parasite species and determine % parasitemia if relevant

94
Q

What do you do when you see a parasite on a thick blood smear?

A

Make a tentative species determination, move to thin smear to quantify and ID

95
Q

When would you determine % parasitemia after seeing parasites on a blood film? (which organisms)

A

Only intracellular parasites (Malaria and babesia)

96
Q

Formula for % parasitemia

A

(Parasitized RBCs/total RBCs counted) x 100

97
Q

Procedure for determining % parasitemia

A

Count parasitized RBCs among 500-2000 RBCs on thin smear, divide parasitized by total counted to get percentage

98
Q

T/F: If multiple parasites are seen in a single cell, that cell is only counted as one parasitized cell.

A

TRUE

99
Q

Which preservatives are good for molecular testing?

A

TotalFix
Unifix
Modified PVA
Ecofix

100
Q

Which preservatives are bad for molecular testing?

A

10% Formalin
SAF
LV-PVA
Protofix

101
Q

Why are parasitic molecular testing specimens ALWAYS accompanied by blood smears?

A

PCR testing will NOT be performed if ID can be determined by microscopic exam (microscopic exam is gold standard and cheaper)

102
Q

What blood parasites are RDTs/EIAs available for?

A

Plasmodium and Wuchereria bancrofti

103
Q

What stool parasites are RDTs/EIAs available for?

A

Cryptosporidium sp, Giardia duodenalis, Entamoeba histolytica/dispar

104
Q

Why isn’t antibody testing (serum/plasma) commonly used to diagnose parasitic infections?

A

Cannot tell if patient currently is infected or has been infected in the past

105
Q

What organism is the cellophane tape preparation used for? What are the rules for collection?

A

Pinworm (Enterobius vermicularis) - recovery of eggs
- Must use clear tape, must be performed at night/early morning (preferably when child is still asleep)

106
Q

Non-blood/stool specimens that may be sent for parasitic testing? What organisms found with each?

A

Duodenal drainage - G. duodenalis or S. stercoralis

Urogenital tract specimens - T. vaginalis

Sputum - organisms that may cause pneumonia, pneumonitis, or Loeffler syndrome

Bone marrow/CSF/Cyst aspirates - hydatid disease, leishmania, trypanosoma cruzi, plasmodium, naegleria fowleri

Biopsy - tissue specimens

107
Q

Why might parasitic culture techniques be used?

A

Diagnostic testing methods, epidemiologic analysis of outbreaks, testing drug resistance, life cycle analysis

108
Q

Detection of what organism are corneal scrapings or contact lenses inoculated onto agar overlayed with E. coli or Enterobacter?

A

Acanthamoeba

109
Q

What is an axenic culture technique?

A

Parasite grown in PURE culture without augmentation with bacteria

110
Q

What is a monoxenic culture technique?

A

A single known bacteria species used to help cultivate the parasite

111
Q

What is a coproculture technique?

A

Fecal culture methods useful for detection of hookworm, S. stercoralis, and Trichostongylus infections

112
Q

What is xenodiagnosis?

A

Use of an intermediate host to isolate a parasitic organism from a human host (ex. T. cruzi)

113
Q

Preventative measures for parasitic infections

A

: Improved personal hygiene
: Ensure proper sanitation
: Avoid fecal-oral contact
: Avoid contaminated water or
soil

114
Q

Ectoparasites

A

Members of the phylum arthropoda that act as biological and mechanical vectors

115
Q

ID of ectoparasites is based on?

A

Recognizing morphological characteristics

116
Q

4 characteristics of arthropods

A
  • Chitinized exoskeleton
  • Pairs of jointed legs or appendages
  • Bilateral symmertry
  • Hemocele (contain blood or lymph)
117
Q

Arachnida vs Insecta

A

Arachnida: 4 pairs of appendages
Insecta - 3 pairs of appendages

118
Q

What are chemoprophylactic agents?

A

Given to individuals traveling to areas where malaria is endemic

Microbiology (24 decks)

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