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Micro & Pathology > Micro Exam 3 > Flashcards

Micro Exam 3 Flashcards

1
Q

What are the metabolic products being tested for in the MRVP test?

A

Methyl red
Voges-Proskauer

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2
Q

What does methyl red contain?

A

Mixed acids (lactic, acetic, formic, and succinic)

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3
Q

What does Voges-Proskauer contain?

A

Acetoin and 2,3-butanediol

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4
Q

What is the positive reaction for a MRVP test?

A

formation of red color in the liquid medium, peptone base with dextrose (clear light yellow color)

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5
Q

What tests would you use to identify gram negative rods?

A

Oxidase test, gram stain, maconkey agar, can tell us if the microorganism is gram + or -

TSI, IMViCdetermine the type of gram - negative rod they are

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6
Q

What does the positive reaction in a MRVP test indicate about the fermentation?

A

It is a carbohydrate fermentation

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7
Q

Describe a Simmons Citrate Agar Slant

A

A solid medium with a sodium citrate, ammonium salt, bromthymol blue and agar with the medium being a forest green color

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8
Q

What is the function of the citrate slant test?

A

To see if the organism can use citrate as its only carbon source and ammonium salt as its only nitrogen source

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9
Q

What represents a positive citrate test?

A

Turns blue (negative is when it remains green)

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10
Q

Describe a SIM medium deep

A

It is a semi-solid, non-selective, differential agar medium with iron salt, thiosulfate, and peptone

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11
Q

What is the SIMs test used to indicate?

A

used to determine 3 tests in gram negative rods: Sulfide, Indole, Motility

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12
Q

What are the three tests in the SIMs Medium Deep and what are the positive results?

A

Hydrogen sulfide - blackening shows positive
- determines if the bacteria can break down sulfur into hydrogen sulfide gas

Indole Production - pink is positive
- checks whether the bacteria can break down tryptophan, an amino acid, to produce indole

Motility - cloudy or turbid growth from the stab is positive

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13
Q

What tests does the IMViC testing process include?

A

Indole, MR, VP, Citrate

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14
Q

Whats the first basic test used to differentiate fermenters from nonfermenters? What does a positive reaction look like?

A

Oxidase test, blue color means its positive which means its a nonfermenter and produces cytochrome

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15
Q

How can we get a false positive or false negative oxidase test?

A

False positive by a metal loop or
False negative when sampling with an older culture

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16
Q

Name the bacterium that are lactose fermenters and oxidase negative

A

Klebsiella pneumoniae, E. Coli, E. aerogenes

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17
Q

Define enterics

A

group of gram-negative rods that inhabit the intestinal tract

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18
Q

What are the oxidase test and MacConkey agar results for Pseudomonas aeruginosa?

A

Oxidase positive so its a nonfermenter

Clear = negative on Mac

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19
Q

Describe a MacConkey agar

A

a differential and selective medium used for detecting gram negative rods due to the crystal violet and bile salts that inhibit the growth of gram +

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20
Q

What results does lactose fermenters show on a Maconkey agar?

A

Pink

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21
Q

Name the contents in a Triple Sugar Iron Agar Slant (TSI)

A

a solid slant with glucose, lactose, sucrose, sulfur, sodium thiosulfate, ferrous sulfate, and phenol red and the pH indicator

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22
Q

Describe a TSI test and what it is used for

A

non-selective and differential medium, used to differentiate enteric, gram-negative bacteria based on their ability to reduce sulfur and ferment carbohydrates

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23
Q

What are the test results of a TSI?

A

Yellow is an acid color (A) and means its a carb fermentator
Red is alkaline because there was no change (K)
H2S production positive would show blackening of agar
Gas production positive shows bubbles in the medium

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24
Q

What is the Kirby Bauer sensitivity test used for?

A

Its a method used to see how a specific drug will effect/kill a patient’s bacterium

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25
Q

What is the physician looking for in a Kirby Bauer sensitivity test?

A

They are looking for the drug that will kill the bacteria the most easily without negative effects to the patient

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26
Q

Name the disk symbol and their antibiotic in the Kirby Bauer test

A

GM - Gentamicin
TMP- Trimethoprim
VA- Vancomycin

27
Q

Name the zone sizes for each antibiotic

A

Resistant, Intermediate, Sensitive

GM Disk content: 10 ug
<=12 13-14 >=15

TMP Disk content: 5 ug
<=10 11-15 >=16

VA Disk content 30 ug
<=14 None >=15

28
Q

Who are the disk content values standardized by?

A

CLSI, Clinical Laboratory Standards

29
Q

If the antibiotic results are sensitive, does that mean it will cure the patient?

A

No, the drug might not react the same in the in vivo as in vitro. It can be TOO sensitive to the point of toxicity or it might not even be able to reach the appropriate body part

30
Q

Whats an example of a sensitive antibiotic that could negatively impact hearing?

A

Aminoglycosides

31
Q

What is Cary Blair media?

A

A liquid transport media that will preserve pathogenic bacteria in stool cultures

32
Q

What are the host defense mechanisms of the GI tract?

A

High stomach acidity, normal flora that colonizes tract and makes it difficult for pathogens to intrude

33
Q

Name the bacterial pathogens of the GI tract

A

Salmonella, Shigella, Campylobacter, Aeromonas, Pleisiomonas, shiga toxin, E.coli 0157

34
Q

Describe and name the pathogen for Pseudomembranous colitis

A

Clostridium difficile’s toxins and is usually associated by using heavy amounts of antibiotics

35
Q

What would you use to clean a patients room who had pseudomembranous colitis?

A

We would use bleach as this disease is easily spread nosocomially

36
Q

What are the two bacterial toxins that are released by bacteria?

A

A Component (Enterotoxin)
B Component (Cytotoxin)

37
Q

B Component (Cytotoxin)

A

the toxin is responsible for binding to the host cell, facilitating the entry or enhancing the effect of the active “A” component

38
Q

A Component (Enterotoxin)

A

The active part of the toxin responsible for the specific effect inside host cells, often interfering with cellular functions. The “A” part typically disrupts the regulation of ion transport in intestinal cells, leading to water loss and diarrhea. Enterotoxins specifically affect the gut

39
Q

Describe Proctitis and name the pathogen associated

A

Inflammation of rectal mucosa and is associated with sexually transmitted diseases like:

Neisseria gonorrhea (GC), Chlamydia
Syphilis (Treponema pallidum)

40
Q

Describe Cholera and name the pathogen associated

A

associated with watery and profuse stools caused by Vibrio cholera

41
Q

Name the viruses that cause Viral gastroenteritis

A

Norovirus (adults), Rotavirus (children)

42
Q

Name common parasites that can cause GI tract diseases

A

Entamoeva histolytica
Giardia
Cyclospora
Cryptosporidium

43
Q

Describe a Eosin Methylene Blue agar (EMB)

A

a selective and differential culture medium used to isolate pathogenic gram - bacteria found in GI tract

44
Q

Name test results for Salmonella

A

MacConkey - Clear colonies / +
Citrate - Blue / +
EMB - Clear / - (they look for lactose fermenter pathogens and salmonella is not one)
TSI - K/A G H2S

45
Q

Whats the mode of transmission for Salmonella?

A

contamined foods most common

46
Q

Name the test results for Shigella

A

MAC - Clear / +
TSI - K/A
Citrate- Green / -

47
Q

Hemolytic uremic syndrome

A

(DIC) the blood does not clot, causes kidney failure, severe complication and life threatening condiiton

48
Q

Who does the hemolytic uremic syndrome happen to?

A

About 10% of people infected with a shiga toxin

49
Q

What organism can cause hemolytic uremic syndrome and releases the shiga toxin?

A

E.coli 0157:H7

50
Q

What should patients with E.coli 0157:H7 be treated with?

A

Only should be treated with supportive therapy like fluids

Never antibiotics

51
Q

What is the Disk Diffusion Method of Kirby Bauer Sensitivity?

A

It is a manual way of doing a sensitivity test

52
Q

Describe the steps of a sensitivity test the manual way

A

An inoculum of bacteria is placed on a Mueller Hinton plate. Paper disks impregnated with a standard concentration of antibiotic are placed on the surface. The antibiotic diffuses out from the disk. The zone around the antibiotic, the kill zone, determines how effective the antibiotic is.

Remember: The disk diffusion test is not a perfect indicator of how the drug will behave in vivo or in the patient’s body

53
Q

Describe the positive results of a catalase reaction and how to trigger a false positive

A

Bubbles = positive
False positive = taking an organism from blood agar plate

54
Q

Name the organism: beta hemolytic, A antigen positive, aka strep group A

A

Streptococcus pyogenes

55
Q

Name the organism: Non-hemolytic, D antigen positive, aka Group D strep

A

Enterococcus faecalis

56
Q

Name the organism: Staphaurex/Rapid Staph Latex positive

A

Staphylococcus aureus

57
Q

Name the organism: Stapaurex/rapid staph latex negative

A

Staphylococcus epidermidis

58
Q

Steps on a strep typing

A

Use white card
2 drops of Reagent 1 in tube
2 drops of Reagent 2 in tube
Pick up organism with Stick (4-6 colonies)
Mix in reagents 1 and 2
Add 4 drops Reagent 3
Use Beryl pipette to place organism on disposable card
Add appropriate strep typing reagent
Mix with stick; rock
Agglutination is positive; no agglutination is negative

59
Q

Steps to do a Staph typing

A

Use smaller card
Drop of staphaurex on slide
Add bug with stick and mix
Rock
Agglutination is positive; no agglutination is negative

60
Q

What toxin is also known as “rice water stools”

A

Vibrio Cholera

61
Q

What is the substrate for indole?

A

Tryptophan

62
Q

Test results for Klebsiella pneumoniae

A

MAC - pink/positive
Mucoid - has a capsule
Gram stain - pink rods/negative
Oxidase - clear/negative
SIMS - negative
TSI - K/K gas
Citrate - +

63
Q

What type of specimen is Klebsiella pneumoniae?

A

sputum from an alocholic

64
Q

Test results for Pseudomonas aeruginosa

A

MAC- clear colonies /+
Blood agar - green and grapey
Oxidase - blue / positive
Gram stain - pink rods
SIMS - positive for motility
Citrate - blue / positive
TSI - K/K

Micro & Pathology (7 decks)

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