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Microbiology > Parasitology Exam 4: Coccidia, Amoeba, Flagellates + Ciliates > Flashcards

Parasitology Exam 4: Coccidia, Amoeba, Flagellates + Ciliates Flashcards

1
Q

What is the class/phylum/subkingdom of Coccidia? What does each classification indicate?

A

Class: Coccidia
Phylum: Sporozoa (Apicomplexa) –> Indicates there is an apical complex and intracellular parasites
Subkingdom: Protozoa –> Indicates they are unicellular

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2
Q

Describe Coccidia as a whole.

A

Unicellular
Obligate intracellular parasites
Have an apical complex

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3
Q

What is an apical complex?

A

Organelle used for host cell penetration and establishment of the intracellular parasitism

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4
Q

What are the intestinal coccidia?

A

Cryptosporidium sp.
Cystoisospora belli
Cyclospora cayetanensis

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5
Q

What are the tissue coccidia?

A

Sarcocystis sp.
Toxoplasma gondii

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6
Q

What are the 2 pertinent Cryptosporidium species and what do they each primarily infect?

A

Cryptosporidium parvum –> mammals in general, including humans
Cryptosporidium hominis –> humans
Cannot differentiate between these 2 species morphologically

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7
Q

Cryptosporidium infects BOTH ___________ and __________ individuals.

A

Immunocompromised AND immunocompetent

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8
Q

Briefly describe the Cryptosporidium life cycle!

A
  • Oocysts ingested
  • Oocytes release sporozoites which invade epi cells
  • Development into trophozoites
  • Trophozoites undergo asexual amplification called merogony to form meronts which contain merozoites
  • Merozoites undergo gametogony to form sexual gametocytes
  • New oocysts formed in epi cells via sporogony
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9
Q

What is a parasitophorous vacuole?

A

Layers of endoplasmic reticulum around an intracellular parasite

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10
Q

Thin-walled vs thick-walled oocysts

A

Thin-walled: ~20%, excyst in the digestive tract, associated with autoinfections

Thick-walled: ~80%, excreted in the environment, resistant to low temperature, salinity, and most disinfectants

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11
Q

What is the ONLY extracellular stage in cryptosporidium life cycle?

A

Oocysts

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12
Q

Transmission of Cryptosporidium sp.

A

Direct contact w/ infected people or animals
Consumption of contaminated water or food
Oocysts are IMMEDIATELY infectious when passed in stool

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13
Q

What is the infective and diagnostic stages of Cryptosporidium?

A

Infective: Oocysts
Diagnostic: thick-walled oocysts in feces

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14
Q

Briefly describe the disease associated with Cryptosporidium in immunocompetent vs immunocompromised individuals.

A

Immunocompetent: diarrhea, nausea, low-grade fever (self-limiting)

Immunocompromised: renal failure patients or renal transplant patients can experience life-threatening diarrhea and AIDS patients can experience extraintestinal infections

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15
Q

Lab diagnosis of Cryptosporidium

A

Modified acid fast stain (bright red oocysts against blue background)
OR
DFA with Giardia (Crypto will appear smaller than Giardia)
OR
H&E staining in jejunum

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16
Q

Reporting/Prevention of Cryptosporidium

A

Cryptosporidiosis = reportable disease in the US, positive diagnosis should be sent to reference lab for confirmation

Prevention: highly resistant to most commercial disinfectants, chlorine can dramatically decrease the oocysts but almost pointless due to exposure time and concentration needed

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17
Q

Infectious/diagnostic stage of Cystoisospora belli

A

Infective: sporulated oocyst –> releases sporozoites
Diagnostic: oocysts in feces

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18
Q

Transmission of Cystoisospora belli

A

Ingestion of food or water contaminated with water, sporulated oocysts

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19
Q

Cystoisospora belli disease

A

Diarrhea

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20
Q

Doctors should consider C. belli infection in AIDS patients who . . . .

A
  • Have immigrated from or traveled to Latin America
  • Are Hispanics born in the US
  • Are young adults
  • Have not received prophylaxis for Pneumocystis infection
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21
Q

Cystoisospora belli lab diagnosis

A

Modified acid fast stain of oocysts in stool
H&E stain on histology specimen

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22
Q

Cystoisospora belli reporting/prevention

A

Quantitation NOT required, but should be reported if seen in stool

Prevention = improve hygiene, improve sanitary conditions

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23
Q

Cyclospora cayetanensis host

A

ONLY HUMANS

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24
Q

Cyclospora cayetanensis infective/diagnostic stages

A

Diagnostic stage = UNSPORULATED oocysts
Infective stage = SPORULATED oocysts

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25
Q

Transmission of C. cayetanensis

A

Fecal-oral - associated with ingestion of contaminated fruits and vegetables

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26
Q

Disease of C. cayetanensis

A

Flulike illness
May be associated with biliary disease

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27
Q

C. cayetanensis lab diagnosis

A

Oocysts are variably acid-fast, may contain granules or have a bubbly appearance (“wrinkled cellophane”)

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28
Q

C. cayetanensis reporting/prevention

A
  • Report to local public health authorities AND CDC

Prevention: wear gloves when gardening, wash your produce thoroughly

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29
Q

2 relevant Sarcocystis species

A

Sarcocystis hominis
Sarcocystis suihominis

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30
Q

Definitive and intermediate hosts of Sarcocystis species

A

Both species definitive hosts = humans
Intermediate host of S. hominis = cattle
Intermediate host of S. suihominis = pigs

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31
Q

Describe the infection process of Sarcocystis species.

A

Intermediate hosts (cows and pigs) infected via ingestion of sporocysts excreted in the feces of definitive hosts.
Definitive hosts infected via ingestion of mature cysts found in the muscles of intermediate hosts.

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32
Q

Diagnostic/infective stage of Sarcocystis species

A

Diagnostic: sporocysts in stool
Infective: ingestion of sporocysts

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33
Q

Disease of Sarcocystis species

A

Sarcocysts develop in human muscle after ingestion of oocysts
Few problems/evidence of being infected
Patients MAY develop muscle swellings with erythema of overlying skin

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34
Q

Lab ID of Sarcocystis

A

Human fecal specimens containing sporocysts
Biopsy specimens containing sarcocysts (mostly cardiac and skeletal muscle) after ingestion of beef or pork

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35
Q

Sarcocystis sp. Reporting/Prevention

A

Reporting = cannot differentiate species, ID should be confirmed by reference lab

Prevention = thoroughly cook meat, careful disposal of animal feces

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36
Q

Definitive host of Toxoplasma gondii

A

Cats

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37
Q

How are cats infected with Toxoplasma gondii?

A

Ingestion of oocysts or carnivorism (outdoor cats more likely to become infected)

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38
Q

3 infectious stages of Toxoplasma gondii

A

Tachyzoites - rapidly multiply
Bradyzoites - in tissue cysts, slowly multiply
Sporozoites - in oocysts of cat feces

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39
Q

Differentiate between tachyzoites and bradyzoites (T. gondii)

A

Tachyzoites - rapidly multiply, crescent shaped, one end more rounded than the other

Bradyzoites - slowly multiply, strong PAS positive

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40
Q

T. gondii disease

A

Toxoplasmosis can be categorized into 4 groups -

Acquired in immunocompetent patient –> usually asymptomatic

Acquired or reactivated in immunocompromised patient –> CNS primarily involved (altered mental state)

Congenital –> can pass to baby and cause microcephaly, etc. (This is why Kristen cannot change cat litter)

Ocular –> chorioretinitis

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41
Q

T. gondii lab diagnosis

A

Most common method is serological diagnosis through antibody testing

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42
Q

2 situations where T. gondii detection is very significant :

A
  1. Tachyzoites in smears/tissue cultures inoculated from CSF
  2. Tachyzoites in patients with acute pulmonary disease and demonstration of tachyzoites in BAL fluid
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43
Q

What group are Flagellates?

A

Mastigophora

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44
Q

Describe flagella as a whole

A

Have specialized locomotor organelles called flagella (long, thin, cytoplasmic extensions)
May infect intestinal tract, bloodstream, or tissues

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45
Q

Distinctive criteria for ID of:
Giardia duodenalis
Chilomastix mesnili
Trichomonas spp

A

Giardia –> sucking disk and axonemes
Chilomastix –> cytostome and spiral grove
Trichomonas –> undulating membrane

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46
Q

Types of pathogenic Intestinal flagella

A

Giardia duodenalis
Dientamoeba fragilis

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47
Q

Types of pathogenic urogenital flagella

A

T. vaginalis

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48
Q

What is the most common cause of intestinal infection worldwide?

A

Giardia duodenalis

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49
Q

Types of non-pathogenic intestinal flagella

A

Chilomastix mesnili
Pentatrichomonas hominis

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50
Q

Describe the life cycle of Giardia duodenalis including diagnostic and infective stages

A

Trophozoite and cyst stages –> ingestion of infective cysts from contaminated food/water (infective stage)

Trophozoites are produced and divide by longitudinal binary fission that produce two daughter trophozoites

  • Trophozoites attach to intestinal epithelium of the host villi using their ventral sucking disk, leave impression prints
51
Q

Giardia epidemiology (transmission, hosts, affected populations)

A

Transmission: ingestion of viable cysts

Beavers are a common reservoir host

Associated with travelers and campters

52
Q

What is the disease of Giardiasis like?

A

GI disease that has stools with lack of blood, mucus, and cellular exudate

53
Q

Giardia lab diagnosis

A

Entero-test capsule or duodenal aspirates can be used for recovering organisms

Antigen detection using DFA

54
Q

Describe the trophozoite of Giardia

A

Pear shaped, looks like old man
Sucking disks, median bodies, and 8 flagella may also be seen

55
Q

What is villous atrophy and what is it associated with?

A

Lack of villi in intestines; degree of atrophy correlates with the degree of malabsorption; associated with Giardia

56
Q

Reporting and prevention of Giardia

A

Reporting = may need to examine up to 6 stool samples, positive stool does NOT require quantitation

Prevention = ensure safe drinking water

57
Q

Describe Chilomastix mesnili (transmission, infection/disease)

A

Transmitted by ingestion of cysts

Nonpathogenic, does not cause disease

58
Q

Chilomastix mesnili trophozoite morphology

A

Distinct oral groove called a cytostome close to the nucleus

59
Q

Chilomastix mesnili cyst morphology

A

Curves cytostomal fibril called the shepherd’s crook

60
Q

Transmission and Affected populations of Dientamoeba fragilis

A

Fecal-oral route suspected due to presence of cyst stage - associated with helminth eggs

Higher infection rates in mental institutions, missionaries, and native americans in arizona

61
Q

Infective/diagnostic stage of Dientamoeba fragilis

A

Infective: fecal-oral route of eggs/cysts

Diagnostic: trophs in feces

62
Q

Trophozoite morphology of Dientamoeba fragilis

A

Lacks external flagella!!!
Resembles amoebae but is NOT

63
Q

Tramission/epidemiology of Paratrichomonas hominis

A

One of the most commonly identified flagellates (after G. duodenalis and D. fragilis)

Nonpathogenic and noninvasive

NO cyst stage

Transmission probably occurs in the trophic form

64
Q

Trophozoite morphology of Paratrichomonas hominis

A

Slender axostyle projects from posterior end
Undulating membrane
5 Flagella (4 anteriorly, 1 posterior)

65
Q

Describe trichomonas vaginalis (transmission, etc)

A

Transmitted through sexual intercourse

The most common nonviral STD

Life cycle only includes trophozoite

66
Q

What is the only natural host for T. vag?

A

Humans

67
Q

Preferred vaginal pH for trichomonas

A

Slightly alkaline

68
Q

Trophozoite morphology of T. vag

A

Obvious axostyle that protrudes through the bottom of the organism, slightly unvisible flagella at anterior end

69
Q

Symptoms of T. vag

A

Vaginal pruritus, discharge, odor, edema, etc

70
Q

T. vag lab ID

A

Often recovered in centrifuged urine sediment
Wet mounts –> must be performed within 10-20 min after sample collection in order to visualize motility

71
Q

Trichomonas tenax is known as?

A

Oral trichomonas

72
Q

Disease of T. tenax

A

Colonizes patients with poor oral hygiene and periodontal disease

73
Q

T. tenax is the _______ of the trichomonads

A

Smallest

74
Q

Transmission of T. tenax

A

Saliva, droplet spray, kissing, contaminated dishes or drinking water

75
Q

lab ID of T. tenax

A

Mouth scrapings

76
Q

Describe ciliates as a whole

A

Move by means of cilia - short extensions of the cytoplasm that cover the surface of the organism

77
Q

What is the one ciliate that infects humans?

A

Neobalantidium coli

78
Q

Ciliates have two different types of nuclei. Describe them

A

Macronucleus - only one
Micronucleus - one or more

79
Q

Describe the life cycle of Neobalantidium coli (infective and diagnostic stage)

A

Infective stage = cyst form
Ingestion of cyst –> excystation –> trophozoites secrete hyaluronidase –> organisms live in small intestine –> cyst formed as trophozoite move down intestine

80
Q

Neobalantidium coli is widely distributed. What animals would it be found in and what climates?

A

Hogs in warm temps
Monkeys in tropics

81
Q

Describe the trophozoite morphology of Neobalantidium coli

A

Anterior end has a cytostome, two nuclei (one bean shaped macronucleus and one smaller round micronucleus)

82
Q

Transmission of neobalantidium coli

A

Ingestion of infective cysts through contaminated food or water

83
Q

Lab ID of neobalantidium coli

A

Stool specimens

84
Q

Therapy of neobalantidium coli

A

Therapy: tetracycline drugs

85
Q

Amoebae class

A

Sarcodina

86
Q

Describe the amoebae as a class.

A

Multiply by binary fission
Capable of movement by pseudopods
Usually transmitted through fecal-oral route
Have both trophozoite and cyst stages - cyst = infective stage

87
Q

What are the pathogenic, free-living amoebae?

A

Naegleria fowleri
Acanthamoeba sp.
Balamuthia mandrillaris

88
Q

What are the pathogenic, intestinal amoebae?

A

Entamoeba histolytica
Blastocystis hominis (controversial)

89
Q

What is the only pathogenic intestinal amoebae?

A

Entamoeba histolytica
(Controversial if B. hominis is pathogenic)

90
Q

Describe Entamoeba histolytica in terms of distribution, affected populations, and transmission.

A

Worldwide distribution from tropics to Arctics.
Affected: men who have sex with men, travelers, institutionalized
Transmission: Ingestion of cysts from contaminated hands/food

91
Q

What is considered DIAGNOSTIC for Entamoeba histolytica?

A

Presence of RBCs in the cytoplasm!!

92
Q

Describe E. histolytica trophozoite (motility and morphology)

A

Monopodial (one pseudopod at a time) motility
Centrally located karyosome
Ingested RBCs = diagnostic for E. histolytica

93
Q

Describe E. histolytica pre-cyst morphology

A

Single nucleus
2 inclusions: chromatoidal bars with SMOOTH, ROUND edges and glycogen mass

94
Q

Describe E. histolytica cyst morphology

A

Can have up to 4 nuclei
Chromatoidal bars with rounded edges still seen
Cyst morphology not used to differentiate Entamoeba species since they all look similar

95
Q

What is the disease of E. histolytica like?

A

amebiasis, amebic dysentery, amebic colitis, amebic hepatitis
Lyses host cells and causes tissue destruction

96
Q

What is trogocytosis?

A

Adherence to mucosa (E. histolytica) - amoeba takes a bite out of host cellular membrane –> development of amebic ulcers and tissue damage in intestinal tract

97
Q

E. histolytica lab ID

A

Start with O&P exam, permanent stained smears are key

98
Q

Reporting of E. histolytica

A

Note genus, species, and life cycle stage present
Should report E. histolytica/dispar group
If species ID is not available, physician is responsible to determine if treatment is warranted

99
Q

E. dispar

A

morphologically identical to E. histolytica, but is the nonpathogenic form
Can only be determined through molecular analysis

100
Q

How is Entamoeba coli different from Entamoeba histolytica?

A
  • Not pathogenic
  • Does not ingest or invade host tissue
  • Cyst chromatoidal bars are IRREGULAR, SPLINTER-SHAPED
  • Cyst contains 8 NUCLEI with eccentrically placed karyosome in each
101
Q

How is Entamoeba hartmanii morphology different from other Entamoeba?

A
  • Mature cyst contains 4 nuclei
  • Mature cysts RETAIN THEIR CHROMATOIDAL BARS (not seen in E. histolytica/dispar)
  • Smaller and more numerous chromatoidal bars
102
Q

What is the smallest of the intestine-dwelling amoebae infecting humans? (nonpathogenic)

A

Endolimax nana

103
Q

What is standout about Iodamoeba butschlii (nonpathogenic intestinal amoeba) morphology?

A

Cyst has a LARGE GLYCOGEN VACUOLE
Only one nucleus!

104
Q

Blastocystis spp. –> what is standout?

A

Pathogenicity is controversial
May be considered a stramenophile (includes brown algae, slime molds, etc)
4 major forms including central vacuole form –> most common form found in clinical stool samples

105
Q

What is the most common form of Blastocystis found in clinical stool samples?

A

Central vacuole form

106
Q

Reporting of Blastocystis species

A

SHOULD be quantified
NOT necessary to state the life cycle form present

107
Q

What causes PAM?

A

N. fowleri

108
Q

What causes GAE?

A

Acanthamoeba spp. and Balamuthia

109
Q

Acanthamoeba keratitis

A

related to poor lens care in contact lens wearers

110
Q

Transmission of Naegleria fowleri

A

Amoebae enter the nasal cavity by inhalation or aspiration of water containing cysts or trophozoites and migrate via olfactory nerves to the brain

111
Q

What types of environments does Naegleria fowleri live in?

A

Freshwater; Highly thermophilic; can survive temperatures up to 45C

112
Q

N. fowleri disease

A

PAM (primary amebic meningoencephalitis) –> infection of the brain and meninges that can be rapidly fatal

113
Q

What is N. fowleri associated with?

A

Neti pots
Swimming in warm lakes and rivers

114
Q

What is the specimen of choice for N. fowleri lab diagnosis?

A

CSF; will show trophozoites; increased protein, decreased glucose high wbc count
NEVER refrigerate

115
Q

N. fowleri culture

A

Bacteria are a food source for the amoebae, tracks made by amoeba as it moves across the plate eating the bacteria

116
Q

Most cases of N. fowleri are diagnosed when?

A

At autopsy

117
Q

Trophozoite morphology of Acanthamoeba sp.

A

Spinelike pseudopods
Single nucleus has a large karyosome

118
Q

Cyst morphology of Acanthamoeba sp.

A

Single nucleus, large karyosome, double wall, slightly wrinkled outer cyst wall

119
Q

What disease is associated with Acanthamoeba sp?

A

GAE (granulomatous amoebic encephalitis)
NOT associated with swimming such as N. fowleri
Associated with keratitis and unproper care of contact lens

120
Q

What is the leading risk factor of Acanthamoeba sp infection?

A

Use of contact lens

121
Q

Morphology of Balamuthia mandrillaris

A

3 visible cyst layers
Difficult to differentiate from Acanthamoeba morphologically
Ectocyst – outer, wrinkled
Mesocyst – middle, structureless
Endocyst – inner, thin

122
Q

Balamuthia disease

A

GAE, similar to Acanthamoeba

123
Q

T/F: Balamuthia will leave tracks on an agar plate.

A

FALSE; does not feed on bacteria like N. fowleri

Microbiology (24 decks)

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