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Medical Microbiology > L23(Part1) - B > Flashcards

L23(Part1) - B Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

____: Association in which one organism derives benefit (parasite) to the detriment of other (host)

____: A parasite that lives within body/internal body passages of its host

____: A parasite that lives on the body surface of the host

A

Parasitism
Endoparasite
Ectoparasite

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2
Q

____: Host which harbors adult SEXUAL stage of parasite

____: host which harbors ASEXUAL stage of parasite; essential to parasite lifecycle; transfers parasite from one definitive host to another

A

Definitive (sexual)
Intermediate (asexual)

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3
Q

______: A vertebrate host that provides a source of parasitic infection to another host in nature

_______: A carrier (usually arthropod) that transmits causative organism of the disease from an infected to an uninfected indivudla

A

Reservoir

Vector

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4
Q

_____: Dormant, immotile stage that permits survival when environmental conditions are hostile

______: Motile, active feeding and reproducing vegetative stage

_____: The encapsulated fertilized ovum of certain sporozoa

A

Cyst

Trophozoite

Oocyst

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5
Q

True or False: A Sporozoan is a protozoan with complex life stages (includes: sexual and asexual stages)

A

True

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6
Q

True or False: Treatment of protozoan parasites are not easy since they are multicellular, prokaryotic organisms

A

False - Treatment of protozoan parasites are not easy since they are UNICELLULAR and EUKARYOTIC organisms

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7
Q

How do protozoan parasite reproduce?

A

Mitotic division (bin fis)
Meiosis

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8
Q

True or False: Trichomonas vaginalis is the only protozoa that causes uro-genital infections

A

True

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9
Q

What are the four major protozoal groups, classified according to mode of locomotion?

A

1) Amebas
2) Flagellates
3) Ciliates
4) Sporozoa

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10
Q

Which of the following protozoa is an Ameba?
A. Giardia
B. Trichomonases
C. Toxoplasma
D. Enamoeba histolytica

A

D. Enamoeba histolytica

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11
Q

Which two protozoa are flagellates?
A. Giardia
B. Trichomonases
C. Toxoplasma
D. Enamoeba histolytica

A

A. Giardia
B. Trichomonases

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12
Q

Which two protozoa are flagellates?
A. Giardia
B. Trichomonases
C. Toxoplasma
D. Enamoeba histolytica

A

A. Giardia
B. Trichomonases

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13
Q

True or False: Naegleria fowleri is neither an ameba nor a flagellates. Rather, it is something in between.

A

True

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14
Q

Which four protozoa are sporozoa (PCB + T)?

A

Plasmodium
Cryptosporidium
Babesia
Toxoplasma

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15
Q

In the trophozoite form, ______ is an active and vegetative amoeba found in the colon that EATS RBC’s and releases PROTEASES (virulence factor!!!)
A. E. histolytica
B. G. lamblia
C. Cryptosporidium parvum

A

A. E. histolytica

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16
Q

Which stage of E. histolytica is mostly found in formed stool and allows for transmission and infection of NEW host?
A. Cyst
B. Trophozoite
C. Oocyst

A

A. Cyst

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17
Q

True or False: In the trophozoite form of E. histolytica, the nucleus has a “ring and dot” appearance (peripheral chromatin + karysome)

A

True

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18
Q

The E. histolytica life cycle:

Ingested form is ___
Excysts in which organ?

A. cyst; small intestine
B. oocyst; large intestine
C. trophozoite; colon

A

A. cyst; small intestine

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19
Q

In the E. histolytica life cycle, trophs live in the ____ via releasing which enzyme?

A

Lives in colon
Releases: proteases

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20
Q

How can E. histolytic disseminate to multiple organs?

A

Via use of protease

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21
Q

When does the cyst for of E. histolytica form?

A

Feces forms and dries in colon

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22
Q

True or False: E. histolytica is transmitted via food and water and dysentary (bloody diarrhea) is the main manifestation

A

True

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23
Q

Flask shaped amoebic ulceration, or liver/brain abscess suggests infection by which pathogen?

A

E. histolytica

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24
Q

True or False: E. histolytica primarily targets the liver and exists in asymptomatic carrier state

A

True

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25
Q

Which three conditions are associated with infection with E. histolytica?

A

1) Amoebic dysentery/colitis
- blood + mucus in stool
2) Amoebic liver/brain abscesses
3) Amoeboma

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26
Q

How do you dx E. histolytica?

A

Microscopic examination of feces (x3 stool)

-Diarrheric feces - trophozoites
-Formed stool - cysts

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27
Q

Which pathogen is found (in trophozoite) in the duodenum and upper jejunium, has “falling leaf” motility, as well as a characteristic “spook” appearance.
A. E. histolytica
B. G. lamblia
C. Cryptosporidium parvum

A

B. G. lamblia

28
Q

What triggers the cyst for of G. lamblia? Where is it found?
A. low Na/large intestine
B. high Na/small bowel
C. dehydration/large bowel
D. dehydration/small bowel

A

C. dehydration/large bowel

29
Q

For G. lamblia, how does one ingest the cyst?

A

Fecally contaminated food or drink

30
Q

Where does G. lamblia excysts?
How does it attach to microvilla?

A. Large intestine; sucking disks
B. Small intestine; suckers
C. Large intestine; suckers
D. Small intestines; sucking disks

A

D. Small intestines; sucking disks

31
Q

True or False: G. lamblia invades villi of the small intestine

A

False - G. lamblia trophozoites live on surface of villi, but do NOT invade (non-invasive)

32
Q

How are G. lamblia cysts formed?

Where are cysts commonly found?

A

Formed: as trophs dehydrate
Found: formed stool

33
Q

Villous atrophy and blunting (lawnmower effect) suggest infection by which microbe?

A

G. lamblia

34
Q

Which pathogen is a common cause of waterborne diarrhea outbreaks and can be transmitted via: food or fecal contamination of food/water?

A

G. lamblia

35
Q

___ are the main reservoir of G. lamblia (but mammals and avians may also harbor..)

A

Humans

36
Q

True or False: Individuals infected with G. lamblia and symptomatic have interference w/fat and protein absorption.

By contrast, carriers are histologically normal, but shed cysts in their stool.

A

True

37
Q

Statorrhea (excess fat in stool) suggests infection by which microbe?

A

G. lamblia

38
Q

Which stain can you do to detect presence of excess fat in stool?

A

Direct Fecal Sudan Stain

39
Q

True or False: PCR/ELISA can be used to diagnose G. lamblia

A

False - can dx E. histolytica

40
Q

How do you dx G. lamblia?

A
  • Stool exam x 3 days
  • Endoscopy
  • Enterotest (duodenal string)
41
Q

In G. lamblia, ____ are found in formed stools while ____ are found in loose/diarrheic stools
A. trophozoites; cysts
B. cysts; trophozoites

A

B. cysts; trophozoites

42
Q

_____ is a sporozoan related to pathogens causing malaria and toxoplasmosis
A. E. histolytica
B. G. lamblia
C. Cryptosporidium parvum

A

C. Cryptosporidium parvum

43
Q

How can you see morphology of C. parvym?

A

Stain w/ Giemsa or H&E (acid fast)

44
Q

_____: A microbe the requires intracellular residences (obligate intracellular parasite) + deep tissue invasion occurs only in immunocompromised hosts

A

Cryptosporidium parvum

45
Q

True or False: Stool smear can be used to identify oocyst of C. parvum

A

True

46
Q

True or False: The thin walled oocyst (sporulated) form of C. parvum exits host, contaminates food/water, then is ingested by host

A

False - thick walled !!!

47
Q

Describe the life cycle of C. parvum

A
48
Q

In the lifecycle of C. parvum, _____ are release from oocyte and attach to microvilli, becoming ____ (obligate intracellular protozoans)
A. cysts; meronts
B. trophozoites; meronts
C. sporozoites; meronts

A

C. sporozoites; meronts

49
Q

What is asexual vs. sexual reproduction known as in the C. parvum life cycle?

A

Asexual: Merogony
Sexual: Sporogony

50
Q

True or False: In C. parvum, oocysts are the result of asexual reproduction

A

False - SEXUAL reproduction

51
Q

True or False: In C. parvum, thin walled oocyts are shed in stool while thick-walled oocyts auto-infect

A

False

Thin walled = autoinfect
Thick walled = shed in stool

52
Q

In C. parvum, Type 1 meront is involved in ____ cycle while Type 2 meront is involved in ____ cycle
A. sexual; asexual
B. asexual; sexual
C. asexual; asexual
D. sexual; sexualt

A

B. asexual; sexual

53
Q

Infection by ____ occurs primarily via: fecal-oral spread. However, it has emerged as the most frequently recognized cause of recreational watter-associated outbreaks of gastroenteritis.

A

C. parvum

54
Q

True or False: Oocysts of C. parvum are more resistant to chlorine and removal by water sanitation than G. lamblia

A

True

55
Q

C. parvum usually infects jejunum, but found throughout GI tract in which patients?

A

Immunocompromised

56
Q

How do symptoms of C. parvum compare in immunocompetent vs. immunocompromised patients?

A
57
Q

How can you identify oocysts in C. parvum?

A

-AF staining / Direct immunofluorescence
- Anti-crytosporidia Ab

58
Q

Prophylaxis for C. parvum?

A
59
Q

True or False : Trichomonas vaginalis, which causes urogenital infections, is a flagellate

A

True

60
Q

How are Acanthamoeba and N. fowleri similar? different?

A

Both environmental amoebas
- N. fowleri is also a flagellate

61
Q

True or False: Plasmodium, Babesia, and Toxoplasma are sporozoan

A

True

62
Q

____ is the only protozoan known to be transmitted via sex

A

T. vaginalis

63
Q

In Trichcomonas, when trophozite is in vaginal/prostatic secretions and urine, it is in ____ stage
A. Infective
B. Diagnostic

A

B. Diagnostic

64
Q

True or False: Trichomonas vaginalis prefers a more acidic environment

A

False - basic

65
Q

True or False: In males, trichomonas often lives on urethral surface, prostate, seminal vesicles – but is often asymptomatic

By contrast, in females, it can cause discharge, vaginitis, and desquamation (does not invade beyond epithelium!)

A

True

66
Q

Strawberry cervix suggests infection by ____

A

Trichomonas

67
Q

How do you dx Trich?

A

1) Motile trichomonads via wet mount
2) Elevated pH in vaginal fluids
3) Frothy discharge

Medical Microbiology (31 decks)

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