Enteric Bacteria

Front 1

What are enteric bacteria?

Back 1

Gram-negative bacteria that are associated with gastrointestinal flora or disease.

Front 2

What are six families of enteric bacteria?

Back 2

1) Enterobacteriaceae
2) Vibrionaceae
3) Pseudomonadeceae
4) Bacteroidaceae
5) Campylobacteraceae
6) Helicobacteraceae

Front 3

What are eight genera that are part of the Enterobacteriaceae family?

Back 3

1)Escherichia
2) Salmonella
3) Shigella
4) Klebsiella
5) Proteus
6) Enterobacter
7) Serratia
8) Yersinia

Front 4

What are the oxygen requirements of most G- rods?

Back 4

Facultative anaerobes

Front 5

What are three exceptions of G- rods that are NOT facultative anaerobes?

Back 5

Pseudomonas and Bacteroides are obligate anaerobes
Campylobacter is microaerophilic

Front 6

What are three common metabolic characteristics of most G- rods?

Back 6

1) Ferment glucose to produce acid and gas
2) Reduce nitrates to nitrites
3) Oxidase negative

Front 7

What is the one exception to the three common metabolic characteristics of most G- rods?

Back 7

Pseudomonas does not ferment glucose and is oxidase positive.

Front 8

What biochemical properties can be used to differentiate enteric bacteria?

Back 8

1) Ability to ferment lactose
2) Ability to produce urease
3) Ability to produce hydrogen sulfide (H2S)

Front 9

Which three intestinal pathogens cannot ferment lactose?

Back 9

1) Shigella
2) Salmonella
3) Pseudomonas

Front 10

Which three intestinal pathogens can ferment lactose?

Back 10

1) Escherichia
2) Enterobacter
3) Klebsiella
EEK! a mouse eats cheese (lactose)

Front 11

Which five enteric bacteria produce urease?

Back 11

1) Helicobacter
2) Klebsiella
3) Proteus
4) Providencia
5) Morganella

Front 12

What is the function of urease?

Back 12

Metabolizes urea to form carbon dioxide ammonia, and water, producing a habitable alkaline environment.

Front 13

What differential media can be used to isolate enteric bacteria from G+ bacteria?

Back 13

Eosin-methylene blue (EMB) agar
MacConkey agar,
Hektoen enteric agar

Front 14

What characteristic do Eosin-methylene blue (EMB) agar, MacConkey agar, &Hektoen enteric agar select for?

Back 14

G- bacteria

Front 15

How does EMB inhibit growth of G+ bacteria?

Back 15

Aniline dyes

Front 16

How does MacConkey agar inhibit growth of G+ bacteria?

Back 16

Bile salts and crystal violet

Front 17

How does Hektoen enteric agar inhibit growth of G+ bacteria

Back 17

Bile salts

Front 18

What characteristic do Eosin-methylene blue (EMB) agar, MacConkey agar, &Hektoen enteric agar screen for?

Back 18

Lactose-fermenting versus
Lactose-NONfermenting bacteria

Front 19

How do lactose-fermenting bacteria appear on EMB?

Back 19

Metallic-green colonies

Front 20

How do lactose-fermenting bacteria appear on MacConkey agar?

Back 20

Pink colonies

Front 21

How do lactose-fermenting bacteria appear on Hektoen enteric agar?

Back 21

Yellow or orange

Front 22

How do nonlactose-fermentig bacteria appear on EMB?

Back 22

Translucent

Front 23

How do nonlactose-fermenting bacteria appear on macConkey agar?

Back 23

Translucent

Front 24

How do nonlactose-fermenting bacteria appear on Hektoen enteric agar?

Back 24

Blue-green

Front 25

What other media selects against G+ organisms?

Back 25

Salmonella-Shigella agar

Front 26

Which four surface antigens are used to differentiate among enteric bacteria?

Back 26

O antigen
H antigen
K antigen
and pili

Front 27

What is the O antigen?

Back 27

Heat-stable cell wall antigen located on the most external surface of LPS (remember "O" for outer)

Front 28

What part of the O antigen confers unique characteristics to different O antigens?

Back 28

Sugars, e.g., the O157 subtype, which is differentiated by its sugar moiety.

Front 29

What is the H antigen?

Back 29

Antigen located on teh flagella
Only those bacteria with "flagHella" will have an H antigen.

Front 30

What is the K antigen?

Back 30

Antigen associated with the capsule of fimbriae

Front 31

What are pili?

Back 31

Antigenic fimbriae responsible for attachment and colonization of an organism.

Front 32

What three characteristics make enteric bacteria pathogenic?

Back 32

1) Enterotixins
2) Endotoxins
3) Capsule

Front 33

How are enterotoxins pathogenic?

Back 33

They cause transduction of fluid into the ileum.

Front 34

How are endotoxins different from enterotoxins?

Back 34

Enterotoxins are released from bacteria.
Endotoxins are found in the LPS complex of the bacterial outer membrane.

Front 35

What endotoxin do almost all G- rods contain?

Back 35

LPS

Front 36

What is a common component in most endotoxins?

Back 36

Toxid Lipid A

Front 37

Why are endotoxins pathogenic?

Back 37

1) Stimulate release of tumor necrosis factor, interleukin-1, and IL-6 leading to hypotension.
2) Stimulate release of IL-1 and IL-6 leading to fever.
3) Hemorrhage in the intestine, adrenal glands, heart, and kidneys.

Front 38

How is the capsule pathogenic?

Back 38

It suppreses phagocytosis

Front 39

Where do G- rods usually cause disease?

Back 39

Intraintestinal, extraintestinal, or both, depending on genera.

Front 40

Which G- rods cause disease primarily inside the enteric tract?

Back 40

Shigella
Vibrio
Helicobacter

Front 41

Which G- rods cause disease outside of the enteric tract?

Back 41

Klebsiella, Enterobacter, Serratia, Proteus, Providencia, Morganella, Pseudomonas, and Bacteroides

Front 42

Which G- rods cause disease both inside and outside of the enteric tract?

Back 42

Escherichia
Salmonella
Yersinia
Campylobacter