Micro- Stools Rotation

Question 1

How long are stool cultures held?

Answer 1

48 hours (Campy up to 96 hours)

Question 2

What does “self-limiting” mean for enteric infections?

Answer 2

Infection resolves without antibiotics

Question 3

What does HE agar select for?

Answer 3

Salmonella and Shigella

Question 4

Salmonella on HE agar looks like?

Answer 4

Green/blue colonies with black center

Question 5

Shigella on HE agar looks like?

Answer 5

Green colonies

Question 6

What does black on HE or SS indicate?

Answer 6

H₂S production

Question 7

What does CIN agar select for?

Answer 7

Yersinia and Aeromonas

Question 8

What is a “bull’s-eye” colony on CIN

Answer 8

Red center with clear edge

Question 9

What organism does MAC with sorbitol detect?

Answer 9

E. coli O157:H7

Question 10

E. coli O157:H7 on MAC-S looks like?

Answer 10

Colorless colonies

Question 11

What agar is used for Vibrio?

Answer 11

TCBS

Question 12

Vibrio cholerae on TCBS looks like?

Answer 12

Yellow colonies

Question 13

What agar is used for Campylobacter?

Answer 13

CAMPY agar

Question 14

What does oxidase-positive NFL suggest in stool cultures? (4)

Answer 14

Vibrio, Aeromonas, Plesiomonas, Campylobacter

Question 15

What does oxidase-negative suggest of BAP?

Answer 15

Enterobacteriaceae (Salmonella, Shigella, E. coli)

Question 16

What does PAD stand for?

Answer 16

Phenylalanine deaminase

Question 17

Which organisms are PAD positive?

Answer 17

Proteus, Providencia, Morganella

Question 18

Why is PAD useful in stool cultures?

Answer 18

Helps rule out Salmonella and Shigella

Question 19

What does TSI test for?

Answer 19

Sugar fermentation, gas, H₂S

Question 20

What does K/A (red/yellow) on TSI mean?

Answer 20

Glucose fermentation only

Question 21

What does A/A (yellow/yellow) on TSI mean?

Answer 21

Glucose, lactose, and/or sucrose Fermenter

Question 22

Salmonella gram stain?

Answer 22

GNR

Question 23

Salmonella oxidase?

Answer 23

neg

Question 24

Salmonella motility?

Answer 24

pos

Question 25

Salmonella TSI?

Answer 25

K/A + H₂S

Question 26

Shigella motility?

Answer 26

Non-motile

Question 27

Shigella TSI?

Answer 27

K/A, no gas, no H₂S

Question 28

Disease classically caused by Shigella?

Answer 28

Dysentery

Question 29

Shigella Group A = ?

Answer 29

Shigella dysenteriae

Question 30

Shigella Group B = ?

Answer 30

Shigella flexneri

Question 31

Shigella Group C = ?

Answer 31

Shigella boydii

Question 32

Shigella Group D = ?

Answer 32

Shigella sonnei

Question 33

Campylobacter gram stain appearance?

Answer 33

Gull-wing shaped GNR

Question 34

Campylobacter oxidase?

Answer 34

pos

Question 35

Campylobacter motility?

Answer 35

Rapid darting

Question 36

Campylobacter growth temperature?

Answer 36

42°C

Question 37

Campylobacter oxygen requirement?

Answer 37

Microaerophilic

Question 38

Yersinia enterocolitica motility at room temp?

Answer 38

Motile

Question 39

Yersinia motility at 37°C?

Answer 39

Non-motile

Question 40

Yersinia urease?

Answer 40

pos

Question 41

Most normal stool flora on MAC are?

Answer 41

Lactose fermenters

Question 42

Oxidase result of normal Enterobacteriaceae?

Answer 42

neg

Question 43

Examples of normal stool flora? (4)

Answer 43

E. coli (non-O157), Enterobacter, Klebsiella, Citrobacter

Question 44

Inflammatory diarrhea means?

Answer 44

Blood and WBCs present

Question 45

Common causes of inflammatory diarrhea? (5)

Answer 45

Shigella, Salmonella, Campylobacter, E. coli O157, Yersinia

Question 46

Non-inflammatory (watery) diarrhea is associated with which organism?

Answer 46

Vibrio

Question 47

what is in HE agar that inhibits GP

Answer 47

bile salts

Question 48

what is in HE agar that makes it diff

Answer 48

lactose and sucrose

Question 49

name of pH indicator in HE agar

Answer 49

Bromthymol blue

Question 50

how does HE agar detect H2S

Answer 50

Ferric salts (Sodium thiosulfate & Ferric Ammonium citrate)

Question 51

what makes SS agar selective for NLF GN (3)

Answer 51

Bile Salts, Sodium Citrate and Brilliant Green

Question 52

what is the pH indicator in SS agar

Answer 52

Neutral red

Question 53

source of sulfur for the production of H2S in SS agar

Answer 53

Sodium thiosulfate

Question 54

what rxn with H2S in SS agar that forms a black center in the colony

Answer 54

ferric chloride

Question 55

what sugar is in SS agar

Answer 55

Mannitol

Question 56

what sugar is in MAC with Sorbitol

Answer 56

Sorbitol

Question 57

agar? -Peptone base agar with yeast extract, oxgall (bile), sodium cholate, citrate, sucrose, ferric citrate, and sodium thiosulfate

Answer 57

TCBS

Question 58

what are the pH indicators in TCBS

Answer 58

Thymol blue and Bromothymol blue

Question 59

when are antibiotics given in stool cases

Answer 59

cholera or severe Shigellosis.

Question 60

What does K/K (red/red) on TSI mean?

Answer 60

Glucose, Lactose, and Sucrose Non-utilizer

Question 61

heat-stable antigens and are identified first in Shigella stereotyping

Answer 61

O antigens

Question 62

heat-labile envelope antigen that may surround a cell wall and mask somatic antigen activity in shigella stereotyping

Answer 62

Vi antigen

Question 63

true or false:Microorganisms having the Vi Antigen will not agglutinate in O antisera

Answer 63

true

Question 65

antigens are heat labile and are usually associated with motility in shigella stereotyping

Answer 65

Flagellar (H) antigens

Question 66

how do you determine the O antigen of shigella cultures

Answer 66

organism must be boiled to destroy the Vi antigen and then tested with O antisera

Question 67

true of false: Salmonella and Shigella do not ferment lactose

Answer 67

true

Question 68

aerobic organism require how much o2

Answer 68

~21% O₂

Question 69

what is the base agar of CAMPY agar

Answer 69

Columbia Agar Base

Question 70

what is in CAMPY agar

Answer 70

activated charcoal, hematin, sodium pyruvate

Question 71

what are the 3 antimicrobial agents in in Campy agar

Answer 71

cefoperazone, cycloheximide and vancomycin

Question 72

shigella on MAC

Answer 72

Non-lactose fermenter → colorless colonies

Question 73

shigella on HE

Answer 73

Green colonies, no black center

Question 74

shigella on SS

Answer 74

Colorless colonies

Question 75

Most common facultative gram-negative rod in normal stool flora

Answer 75

e. coli

Question 76

What type of pathogen is E. coli (non-O157)?

Answer 76

Opportunistic pathogen

Question 77

Give an example of E. coli as a true enteric pathogen

Answer 77

E. coli O157:H7

Question 78

Which antigen is used for Shigella serogrouping?

Answer 78

o

Question 79

What is the O antigen part of?

Answer 79

Lipopolysaccharide (LPS)

Question 80

Is the O antigen heat stable or heat labile?

Answer 80

Heat stable

Question 81

What antigen is associated with bacterial motility?

Answer 81

h antigen

Question 82

Is the H antigen heat stable or heat labile?

Answer 82

heat labile

Question 83

Why doesn’t Shigella have an H antigen?

Answer 83

it is non-motile

Question 84

What is the K antigen?

Answer 84

Capsular antigen

Question 85

Is the K antigen heat stable or heat labile?

Answer 85

heat labile

Question 86

How can the K (Vi) antigen affect serotyping?

Answer 86

It can block O antigen detection

Question 87

What sugars are in Hektoen Enteric (HE) agar?

Answer 87

lactose, sucrose, & salicin

Question 88

What compound supplies sulfur for H₂S production on HE?

Answer 88

Sodium thiosulfate

Question 89

What compound reacts with H₂S to form black precipitate?

Answer 89

Ferric ammonium citrate

Question 90

Which Enterobacteriaceae is non-motile and lactose fermenting?

Answer 90

klebsiella

Question 91

What lab finding is associated with inflammatory diarrhea?

Answer 91

Fecal WBCs

Question 92

What is the mechanism of cholera diarrhea?

Answer 92

Toxin-mediated fluid secretion

Question 93

What complication is associated with E. coli O157:H7?

Answer 93

Hemolytic uremic syndrome (HUS)