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Medical Microbiology > Exam D > Flashcards

Exam D Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

A formed stool is received in the laboratory at 3 am for ova and parasite exam. The night shift tech is certain that the workload will prevent examination of the specimen until 6 AM when the next shift arrives. The technologist should…

A

preserve the specimen in formalin until it can be examined

-formed stool is unlikely to contain trophozoites so direct examination of the stool is not necessary. the stool should be preserved as soon as possible to preserve any cysts, ova, or larvae that may be present.

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2
Q

Preservatives of stool:

If you cant use a specimen within ____ hour, use PVA.

A

1

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3
Q

Protozoan motility AND _____________ will not be accurate if unpreserved and examined after 30 minutes.

A

trophozoites

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4
Q

Protozoan motility AND trophozoites will not be accurate if unpreserved and examined after ____ minutes

A

30

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5
Q

Smears being evaluated using the trichrome stain should be preserved in a ________TUBE

A

PVA

(10% formalin)

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6
Q

PVA acts as an _________

A

adhesive***

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7
Q

Formed stool should be examined within ___ hours and may be refrigerated for 1-2 days if examination is delayed, but this does not guarantee full recovery of parasites

A

24

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8
Q

What can be found in formed stool within 24 hours, or 1-2 days if refrigerated?

A

-Protozoan cysts are found here
-Helminth eggs and larvae are found here

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9
Q

Semisolid stool should be examined within ___ hours

Liquid stool should be examined within ___ minutes

A

1, 30

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10
Q

What is found in semisolid stool?
In liquid stool?

A

-trophozoites
-Helminth eggs and larvae

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11
Q

What is trichrome stain used for?

A

intestinal protozoa

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12
Q

What is Methenamine Silver stain used for?

A

Pneumocystis jirovecii ( upside down shaped bulb)***

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13
Q

What is Iron hematoxylin stain used for?

A

non-coccidial intestinal protozoa

-Protozoa trophozoites and cysts
-Yeast

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14
Q

What is Modified kinyoun acid-fast stain used for?

A

Cryptosporidium, cyclospora, isospora, microsporidia

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15
Q

What is Giemsa stain used for?

A

-Blood parasites: plasmodium, trypanosomes, babesia, and leishmania
-Schuffner dots stain red

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16
Q

Coccidial protozoa include:

A

Cryptosporidium
Cyclospora
Isospora
Toxoplasma
Coccidial protozoa are classified by their thick walled oocysts

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17
Q

P. vivax, P. ovale, P. malariae, Babesia:

Acute phase: ________
Latent phase: _______

A

in blood

in organs

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18
Q

-Schuffner’s dots (eosinophilic stippling)**
-Signet rings**
-enlarged RBCs, x number of merozoites (If RBC too full, merozoites leave and then causes fever)
-Tertian

A

P. vivax

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19
Q

-Tertian
-Schizont resembling a rosette
-Schuffner dots

A

P. ovale

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20
Q

-band/basket shape
-Quartan

A

P. malariae

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21
Q

Maltese cross with…

A

Babesia

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22
Q

What are two ways plasmodium is opposite from Babesia?

A

Babesia:
-Amount does not correlate with the severity of the disease (plasmodium is opposite)
-Absent schizonts, gametocytes, and pigment (plasmodium is opposite)

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23
Q

-Maltese cross
-Can be intracellular or extracellular
-Tick borne vector but affects rodents and cattle the most (plasmodium affects man and has mosquito vectors)

A

Babesia

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24
Q

which plasmodium has 6 - 12 merozoites?***

A

?

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25
Q

TRUE OR FALSE:
germ tubes always have a constriction

A

False

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26
Q

What is the best stain for AFB?*

A

Auramine or Fluorescein

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27
Q

What is not spread by spores?*

A

Sporothrix = from skin trauma, not inhalation of spores

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28
Q

Is Cryptosporidium a fungus or a parasite?

A

parasite

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29
Q

What is KOH used for?*

A

serves as an enzymatic agent that breaks down debris in a specimen, such as epithelial cells and WBCs, to view yeast or pseudohyphae.

-breaks down hair and nail

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30
Q

M. avium complex is associated in what patient population?

A

immunosuppression/pulm like TB/dissemination/AIDS

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31
Q

which media is NOT typically used for ID of M.tb?

A

Loeffler – Loeffler is used for Corynebacterium

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32
Q

M. tuberculosis:

Niacin ____ and nitrate ____.

A

pos, pos

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33
Q

-Aerobic
-Nonmotile
-Gram + (due to mycolic acids)

A

M. tuberculosis

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34
Q

Cell wall of M. tuberculosis?

A

thick, hydrophobic, waxy and rich in mycolic acids (mycolates)

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35
Q

M. tuberculosis grows on what substrate?

A

ammonia/nitrogen sources, glycerol as carbon source w/ mineral salts, optimal growth is 25C to over 50C
-Some species are fastidious

36
Q

What antibiotics are used for M.tuberculosis?

A

Use Beta-lactam: Carbapenem (Meropenem; Cell wall synthesis inhibitor or Rifampin (Metronidazole; NA synthesis inhibitor)

37
Q

M. tuberculosis:

Spontaneous mutation and AB resistance occurs w. Rifampin due to mutation in ______ gene coding the beta subunit of RNA polymerase.

A

rpoB

38
Q

Diphtheria and M avium is tellurite _______ and urease ________

A

pos, neg

39
Q
A

Curvularia***

40
Q

Measles is…

A

paramyxoviridae**

41
Q

_____________ for influenza

-An influenza-infected cell contains virally encoded glycoprotein hemagglutinins in cytoplasmic membrane
-Add RBCs to culture medium

A

Hemadsorption

42
Q

What is the specimen collection for RSV?

A

(nasopharyngeal aspirate vs sputum)
Cotton rayon or dacron swab w/ aluminum wire (No wooden shafts)

43
Q

-common colds and acute respiratory diseases
-Double stranded DNA virus (dsDNA)

A

Adenovirus***

44
Q

What markers would be seen in chronic hepatitis?

A

+ HBsAg, + HBeAb, + HBcAb (check this one)

45
Q

What is the common cause of viral gastroenteritis in children?

A

Rotavirus (reoviridae family)

46
Q

Protozoan, pt had recurrent fever 48 hrs, went to Vietnam, what where would u find the parasite?

A

Blood (maybe P. Vivax , ovale, or falciparum?)

47
Q

Case study: man from brazil had lots of amastigotes. What could it be?

A

Trypanosoma cruzi (chagas disease)***

48
Q

The incorrect match between organisms and characteristic is:

a. Chilomastix mesnili and Shepherd’s crook and lemon shape
b. Plasmodium malariae and band trophozoite
c. Hymenolepsis nana and striated shell (dwarf tapeworm: cestode)
d. Wuchereria bancrofti and sheathed microfilariae

A

c. Hymenolepsis nana and striated shell (dwarf tapeworm: cestode)

49
Q

Case study: Pt has muscle aches and ate bad pork, physician believes it to be trichinosis.
caused by…

A

trichinella spiralis

50
Q

What is NOT a way to differentiate the microfilariae?

-Nuclei in tail
-Female genitalia
-Geographic location
-Sheath or unsheath

A

Geographic location

51
Q

Which can be seen in stool?

A

Strongyloides stercoralis eggs and larvae (rhabditiform larvae)

52
Q

-short buccal capsule and large genital primordium*
-Smallest nematode known to cause human infection

A

Strongyloides stercoralis***

53
Q

Causes a TB-like infection

A

histoplasma

54
Q

What type of tapeworm is Taenia saginata?
Taenia solium?

A

Beef tapeworm

Pig tapeworm

55
Q

Which is longer, Taenia solium or Taenia saginata?

A

Taenia saginata

56
Q

Small and globular scolex with 2 layers of hooks and 4 suckers

A

Taenia solium***

57
Q

Large quadrate scolex (4 large circles on head) with no hooks, no rostelum;

A

Taenia saginata

58
Q

Taenia solium or Taenia saginata?

Egg and larvae are infective to man

A

Taenia solium

59
Q

What is the definitive host for Taenia solium and Taenia saginata?

A

man

60
Q

-Hookworm
-buccal capsule and 6 teeth
-Larger and thicker than Strongyloides stercoralis

A

Ancylostoma duodenale

61
Q

What are the hosts for Ascaris lumbricoides (roundworm)?

A

Only host is human
Largest nematode that can infect us
No teeth, has 3 lips
Can lay fertilized or unfertilized

62
Q

Parasite that can be both intermediate and main host in humans?

A

enterobius vermicularis***
-Most common worm parasite in the world
Pinworm
-Autoinfection and retroinfection

63
Q

What is the only pathogenic spp of entamoeba?

A

Entamoeba histolytica

64
Q

-Protozoa
-Direct life cycle
-LARGEST centrally located karyosome
-Trophozoite has a “clean” cytoplasm without any vacuoles and 1 nucleus

A

Entamoeba histolytica

65
Q

Cysts have 1-4 nuclei with 1-2 chromatoid bodies (rarely 4 nuclei mostly just 1)
No binary fission, but the nucleus does divide (4 max) (division= infectious stage!)

A

Entamoeba histolytica

66
Q

What are the three types of Leishmania?

A

-visceral
-cutaneous
-mucocutaneous

67
Q

Large red dots

A

Mauer’s dots

68
Q

What is the most common and frequent cause of malaria?

A

P. Vivax

( others include: P falciparum, P vivax, P ovale and P malariae)

69
Q

Hydatid cyst disease is found in…

A

dogs and humans!

70
Q

What is the dog tapeworm?

A

Echinococcus granulosus (Cestode; dog tapeworm)

71
Q
A

Dientamoeba ***

72
Q

Two pictures, E. coli and Iodamoeba butchlii, what you would do if you see these two in the sample?

A

don’t do anything bc they both are nonpathogenic amoebas)

Entamoeba coli trophozoite has a “dirty” cytoplasm that is coarse and vacuolated

73
Q

-Oriental blood fluke in feces
-Round with small lateral knob**
-Small ovary in the middle of the body
-Has no “tail”/spine

A

Schistosoma japonicum (lil bulb) (blood fluke; schistosome)

74
Q

What eggs/larvae you can find in stool?

A

Strongyloides sterocoralis larvae is found in stool**

Strongyloides stercoralis: “autoinfection” and free living life cyclecro! Can live in host or outside of host

75
Q

___________ is found in the appendix and stool samples are not recommended because it is rare to find them in the stool

A

Enterobius vermicularis

76
Q

What organism has an egg that is operculated with a knob at the abopercular (on the opposite) end

A

clonorchis sinensis (liver fluke)

77
Q

Blood fluke (trematodes)

A

Schistosoma (Mansoni, Haematobium, Japonicum)

78
Q

-Jerky or twitching motility
-No cysts
-Pear shape, with undulating membrane and 4 flagella

A

trichomonas vag

79
Q

-West african sleeping sickness (stage II)
-Intermediate host: Caused by tsetse fly bite
-Blood parasite
-Painless chancre at bite site
-Long “shrimp-like” body
-Definitive host: man

A

Trypanosoma brucei gambiense ***

80
Q

-South american trypanosomiasis
-Chagas disease
-Intermediate host: Triatomine bug “kissing bug” bite
-Definitive host: man
-Blood parasite
-C or U shaped “shrimp”

A

Trypanosoma cruzi***

81
Q

What is the causative agent of Chagas disease?

A

Trypanosoma cruzi***

82
Q

types of Leishmania:**

also known as kala-azar, is fatal if left untreated in over 95% of cases. It is characterized by irregular bouts of fever, weight loss, enlargement of the spleen and liver, and anemia. Most cases occur in Brazil, east Africa and India.

A

Visceral

83
Q

types of Leishmania:**

is the most common form and causes skin lesions, mainly ulcers, on exposed parts of the body. These can leave life-long scars and cause serious disability or stigma. About 95% of CL cases occur in the Americas, the Mediterranean basin, the Middle East and central Asia.

A

Cutaneous

84
Q

types of Leishmania:

leads to partial or total destruction of mucous membranes of the nose, mouth and throat. Over 90% of mucocutaneous leishmaniasis cases occur in Bolivia (the Plurinational State of), Brazil, Ethiopia and Peru.

A

Mucocutaneous

85
Q
A

Medical Microbiology (12 decks)

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