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
2
Q
Describe Coccidia as a whole.
A
Unicellular
Obligate intracellular parasites
Have an apical complex
3
Q
What is an apical complex?
A
Organelle used for host cell penetration and establishment of the intracellular parasitism
4
Q
What are the intestinal coccidia?
A
Cryptosporidium sp.
Cystoisospora belli
Cyclospora cayetanensis
5
Q
What are the tissue coccidia?
A
Sarcocystis sp.
Toxoplasma gondii
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
7
Q
Cryptosporidium infects BOTH ___________ and __________ individuals.
A
Immunocompromised AND immunocompetent
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
9
Q
What is a parasitophorous vacuole?
A
Layers of endoplasmic reticulum around an intracellular parasite
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
11
Q
What is the ONLY extracellular stage in cryptosporidium life cycle?
A
Oocysts
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
13
Q
What is the infective and diagnostic stages of Cryptosporidium?
A
Infective: Oocysts
Diagnostic: thick-walled oocysts in feces
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
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
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
17
Q
Infectious/diagnostic stage of Cystoisospora belli
A
Infective: sporulated oocyst –> releases sporozoites
Diagnostic: oocysts in feces
18
Q
Transmission of Cystoisospora belli
A
Ingestion of food or water contaminated with water, sporulated oocysts
19
Q
Cystoisospora belli disease
A
Diarrhea
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
21
Q
Cystoisospora belli lab diagnosis
A
Modified acid fast stain of oocysts in stool
H&E stain on histology specimen
22
Q
Cystoisospora belli reporting/prevention
A
Quantitation NOT required, but should be reported if seen in stool
Prevention = improve hygiene, improve sanitary conditions
23
Q
Cyclospora cayetanensis host
A
ONLY HUMANS
24
Q
Cyclospora cayetanensis infective/diagnostic stages
A
Diagnostic stage = UNSPORULATED oocysts
Infective stage = SPORULATED oocysts
25
Transmission of C. cayetanensis
Fecal-oral - associated with ingestion of contaminated fruits and vegetables
26
Disease of C. cayetanensis
Flulike illness
May be associated with biliary disease
27
C. cayetanensis lab diagnosis
Oocysts are variably acid-fast, may contain granules or have a bubbly appearance ("wrinkled cellophane")
28
C. cayetanensis reporting/prevention
- Report to local public health authorities AND CDC
Prevention: wear gloves when gardening, wash your produce thoroughly
29
2 relevant Sarcocystis species
Sarcocystis hominis
Sarcocystis suihominis
30
Definitive and intermediate hosts of Sarcocystis species
Both species definitive hosts = humans
Intermediate host of S. hominis = cattle
Intermediate host of S. suihominis = pigs
31
Describe the infection process of Sarcocystis species.
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.
32
Diagnostic/infective stage of Sarcocystis species
Diagnostic: sporocysts in stool
Infective: ingestion of sporocysts
33
Disease of Sarcocystis species
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
34
Lab ID of Sarcocystis
Human fecal specimens containing sporocysts
Biopsy specimens containing sarcocysts (mostly cardiac and skeletal muscle) after ingestion of beef or pork
35
Sarcocystis sp. Reporting/Prevention
Reporting = cannot differentiate species, ID should be confirmed by reference lab
Prevention = thoroughly cook meat, careful disposal of animal feces
36
Definitive host of Toxoplasma gondii
Cats
37
How are cats infected with Toxoplasma gondii?
Ingestion of oocysts or carnivorism (outdoor cats more likely to become infected)
38
3 infectious stages of Toxoplasma gondii
Tachyzoites - rapidly multiply
Bradyzoites - in tissue cysts, slowly multiply
Sporozoites - in oocysts of cat feces
39
Differentiate between tachyzoites and bradyzoites (T. gondii)
Tachyzoites - rapidly multiply, crescent shaped, one end more rounded than the other
Bradyzoites - slowly multiply, strong PAS positive
40
T. gondii disease
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
41
T. gondii lab diagnosis
Most common method is serological diagnosis through antibody testing
42
2 situations where T. gondii detection is very significant :
1. Tachyzoites in smears/tissue cultures inoculated from CSF
2. Tachyzoites in patients with acute pulmonary disease and demonstration of tachyzoites in BAL fluid
43
What group are Flagellates?
Mastigophora
44
Describe flagella as a whole
Have specialized locomotor organelles called flagella (long, thin, cytoplasmic extensions)
May infect intestinal tract, bloodstream, or tissues
45
Distinctive criteria for ID of:
Giardia duodenalis
Chilomastix mesnili
Trichomonas spp
Giardia --> sucking disk and axonemes
Chilomastix --> cytostome and spiral grove
Trichomonas --> undulating membrane
46
Types of pathogenic Intestinal flagella
Giardia duodenalis
Dientamoeba fragilis
47
Types of pathogenic urogenital flagella
T. vaginalis
48
What is the most common cause of intestinal infection worldwide?
Giardia duodenalis
49
Types of non-pathogenic intestinal flagella
Chilomastix mesnili
Pentatrichomonas hominis
50
Describe the life cycle of Giardia duodenalis including diagnostic and infective stages
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
Giardia epidemiology (transmission, hosts, affected populations)
Transmission: ingestion of viable cysts
Beavers are a common reservoir host
Associated with travelers and campters
52
What is the disease of Giardiasis like?
GI disease that has stools with lack of blood, mucus, and cellular exudate
53
Giardia lab diagnosis
Entero-test capsule or duodenal aspirates can be used for recovering organisms
Antigen detection using DFA
54
Describe the trophozoite of Giardia
Pear shaped, looks like old man
Sucking disks, median bodies, and **8 flagella** may also be seen
55
What is villous atrophy and what is it associated with?
Lack of villi in intestines; degree of atrophy correlates with the degree of malabsorption; associated with Giardia
56
Reporting and prevention of Giardia
Reporting = may need to examine up to 6 stool samples, positive stool does NOT require quantitation
Prevention = ensure safe drinking water
57
Describe Chilomastix mesnili (transmission, infection/disease)
Transmitted by ingestion of cysts
Nonpathogenic, does not cause disease
58
Chilomastix mesnili trophozoite morphology
Distinct oral groove called a cytostome close to the nucleus
59
Chilomastix mesnili cyst morphology
Curves cytostomal fibril called the shepherd's crook
60
Transmission and Affected populations of Dientamoeba fragilis
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
Infective/diagnostic stage of Dientamoeba fragilis
Infective: fecal-oral route of eggs/cysts
Diagnostic: trophs in feces
62
Trophozoite morphology of Dientamoeba fragilis
Lacks external flagella!!!
Resembles amoebae but is NOT
63
Tramission/epidemiology of Paratrichomonas hominis
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
Trophozoite morphology of Paratrichomonas hominis
Slender axostyle projects from posterior end
Undulating membrane
5 Flagella (4 anteriorly, 1 posterior)
65
Describe trichomonas vaginalis (transmission, etc)
Transmitted through sexual intercourse
The most common nonviral STD
Life cycle only includes trophozoite
66
What is the only natural host for T. vag?
Humans
67
Preferred vaginal pH for trichomonas
Slightly alkaline
68
Trophozoite morphology of T. vag
Obvious axostyle that protrudes through the bottom of the organism, slightly unvisible flagella at anterior end
69
Symptoms of T. vag
Vaginal pruritus, discharge, odor, edema, etc
70
T. vag lab ID
Often recovered in centrifuged urine sediment
Wet mounts --> must be performed within 10-20 min after sample collection in order to visualize motility
71
Trichomonas tenax is known as?
Oral trichomonas
72
Disease of T. tenax
Colonizes patients with poor oral hygiene and periodontal disease
73
T. tenax is the _______ of the trichomonads
Smallest
74
Transmission of T. tenax
Saliva, droplet spray, kissing, contaminated dishes or drinking water
75
lab ID of T. tenax
Mouth scrapings
76
Describe ciliates as a whole
Move by means of cilia - short extensions of the cytoplasm that cover the surface of the organism
77
What is the one ciliate that infects humans?
Neobalantidium coli
78
Ciliates have two different types of nuclei. Describe them
Macronucleus - only one
Micronucleus - one or more
79
Describe the life cycle of Neobalantidium coli (infective and diagnostic stage)
Infective stage = cyst form
Ingestion of cyst --> excystation --> trophozoites secrete **hyaluronidase** --> organisms live in small intestine --> cyst formed as trophozoite move down intestine
80
Neobalantidium coli is widely distributed. What animals would it be found in and what climates?
Hogs in warm temps
Monkeys in tropics
81
Describe the trophozoite morphology of Neobalantidium coli
Anterior end has a cytostome, two nuclei (one bean shaped macronucleus and one smaller round micronucleus)
82
Transmission of neobalantidium coli
Ingestion of infective cysts through contaminated food or water
83
Lab ID of neobalantidium coli
Stool specimens
84
Therapy of neobalantidium coli
Therapy: tetracycline drugs
85
Amoebae class
Sarcodina
86
Describe the amoebae as a class.
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
What are the pathogenic, free-living amoebae?
Naegleria fowleri
Acanthamoeba sp.
Balamuthia mandrillaris
88
What are the pathogenic, intestinal amoebae?
Entamoeba histolytica
Blastocystis hominis (controversial)
89
What is the only pathogenic intestinal amoebae?
Entamoeba histolytica
(Controversial if B. hominis is pathogenic)
90
Describe Entamoeba histolytica in terms of distribution, affected populations, and transmission.
Worldwide distribution from tropics to Arctics.
Affected: men who have sex with men, travelers, institutionalized
Transmission: Ingestion of cysts from contaminated hands/food
91
What is considered DIAGNOSTIC for Entamoeba histolytica?
Presence of RBCs in the cytoplasm!!
92
Describe E. histolytica trophozoite (motility and morphology)
Monopodial (one pseudopod at a time) motility
Centrally located karyosome
Ingested RBCs = diagnostic for E. histolytica
93
Describe E. histolytica pre-cyst morphology
Single nucleus
2 inclusions: chromatoidal bars with SMOOTH, ROUND edges and glycogen mass
94
Describe E. histolytica cyst morphology
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
What is the disease of E. histolytica like?
amebiasis, amebic dysentery, amebic colitis, amebic hepatitis
**Lyses host cells and causes tissue destruction**
96
What is trogocytosis?
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
E. histolytica lab ID
Start with O&P exam, permanent stained smears are key
98
Reporting of E. histolytica
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
E. dispar
morphologically identical to E. histolytica, but is the nonpathogenic form
Can only be determined through molecular analysis
100
How is Entamoeba coli different from Entamoeba histolytica?
- 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
How is Entamoeba hartmanii morphology different from other Entamoeba?
- Mature cyst contains 4 nuclei
- Mature cysts RETAIN THEIR CHROMATOIDAL BARS (not seen in E. histolytica/dispar)
- Smaller and more numerous chromatoidal bars
102
What is the smallest of the intestine-dwelling amoebae infecting humans? (nonpathogenic)
Endolimax nana
103
What is standout about Iodamoeba butschlii (nonpathogenic intestinal amoeba) morphology?
Cyst has a LARGE GLYCOGEN VACUOLE
Only one nucleus!
104
Blastocystis spp. --> what is standout?
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
What is the most common form of Blastocystis found in clinical stool samples?
Central vacuole form
106
Reporting of Blastocystis species
SHOULD be quantified
NOT necessary to state the life cycle form present
107
What causes PAM?
N. fowleri
108
What causes GAE?
Acanthamoeba spp. and Balamuthia
109
Acanthamoeba keratitis
related to poor lens care in contact lens wearers
110
Transmission of Naegleria fowleri
Amoebae enter the nasal cavity by inhalation or aspiration of water containing cysts or trophozoites and migrate via olfactory nerves to the brain
111
What types of environments does Naegleria fowleri live in?
Freshwater; Highly thermophilic; can survive temperatures up to 45C
112
N. fowleri disease
PAM (primary amebic meningoencephalitis) --> infection of the brain and meninges that can be rapidly fatal
113
What is N. fowleri associated with?
Neti pots
Swimming in warm lakes and rivers
114
What is the specimen of choice for N. fowleri lab diagnosis?
CSF; will show trophozoites; increased protein, decreased glucose high wbc count
NEVER refrigerate
115
N. fowleri culture
Bacteria are a food source for the amoebae, tracks made by amoeba as it moves across the plate eating the bacteria
116
Most cases of N. fowleri are diagnosed when?
At autopsy
117
Trophozoite morphology of Acanthamoeba sp.
Spinelike pseudopods
Single nucleus has a large karyosome
118
Cyst morphology of Acanthamoeba sp.
Single nucleus, large karyosome, double wall, slightly wrinkled outer cyst wall
119
What disease is associated with Acanthamoeba sp?
GAE (granulomatous amoebic encephalitis)
NOT associated with swimming such as N. fowleri
Associated with keratitis and unproper care of contact lens
120
What is the leading risk factor of Acanthamoeba sp infection?
Use of contact lens
121
Morphology of Balamuthia mandrillaris
3 visible cyst layers
Difficult to differentiate from Acanthamoeba morphologically
Ectocyst -- outer, wrinkled
Mesocyst -- middle, structureless
Endocyst -- inner, thin
122
Balamuthia disease
GAE, similar to Acanthamoeba
123
T/F: Balamuthia will leave tracks on an agar plate.
FALSE; does not feed on bacteria like N. fowleri
