Exercise 11 Gram Negative Enteric Rods

Front 1

Coliform bacteria

Back 1

A gram negative rod that is capable of fermenting lactose with the production of acid and gas. Examples: Escherichia coli, Enterobacter aerogenes, Klebsiella sp.

Front 2

Enteric

Back 2

Pertaining to intestines

Front 3

Fermentation

Back 3

An energy yielding metabolic pathway in which organic compounds are both electron acceptors and donors.

Front 4

Normal flora

Back 4

Normal flora helps to prevent pathogens from establishing infections through competition of space, nutrients, and attachment sites.
Altered normal flora allows for opportunistic pathogenic organisms to grow unchecked and establish infection.

Front 5

C. difficile

Back 5

part of the normal flora;
kept at a low level by normal flora
antibiotic-induced colitis (pseudomembranous colitis)

Front 6

Enterobacteriaeceae family

Back 6

Gram-, non sporulating bacilli (rods);
1. lactose fermeter: Escherichia coli, Klebsiella, Enterobacter aerogenes
2. non lactose fermenter: Proteus vulgaris, Pseudomonas aeruginosa, Salmonella, Shigella

Front 7

IMViC biochemical test

Back 7

commonly performed to distinguish among different enteric organisms.
indole, methy red, Voges-Proskauer, citrate

Front 8

Indole test

Back 8

1% tryptone broth (amino acid, tryptophan)
if the bacteria contains tryptophanase, they can hydrolyze trptophan into indole, pyruvic acid and ammonia. The bacteria will not use indole.
Indole will accumkulate in the media.
If added 4 drops of Kovacs' reagent,
cherry red ring+
brownish yellow ring-

Front 9

Methy red test

Back 9

all enteric bacteria utilize glucose for their energy needs
end product varies due to different enzyme pathsway;
8 drop Methy red reagent

glucose formentation product (lactic, acetic, formic, ph 4) : red +

glucose formentation (ph6): yellow-

Front 10

Voges-Proskauer test

Back 10

identifies bacteria that ferment glucose
10 drops Voges Proskauer reagent A, B
glucose fermentation (acetoin, 2,3-butanediol)--brick red precipitate +
no color -

take 14 minutes to an hour to develop

Front 11

Simmon citrate test

Back 11

determines if an organism can utilize citrate as its sole carbon source for their energy needs.

use citrate (alkaline, ph increases)--blue +

green-

Front 12

Urea hydrolysis

Back 12

if the organism has the enzyme urease, it is capable of hydrolyzing the urea and form co2 and ammonia, ph increases
from peach to pink: +
yellow -

Front 13

Motility agar

Back 13

organisms re stabbed into semi-solid agar to determine motility.
Use inoculating needle to transfer test organism to the center of deep.
Insert needle as far as you can.

Motile: move away from the stab line, seems cloudy throughout
non-motile: only be observed in the stab-line

Front 14

Oxidase test

Back 14

determines if the organism contains cytochrome C as part of their electron transport chain.
hot pink (20s)

Front 15

MacConkey agar

Back 15

selective/differential medium
selective because only Gram- can grown on MacConkey;
differential because it contains a color indicator that will cause the colonies to turn purple if the organism is capable of fermenting lactose (lower ph)

Front 16

Sugar fermentation tube

Back 16

contain different sugar and Durham tube (inverted with the test tube to detect gas production)
any media displacement within the Durham indicates gas production

yellow +
pink _
A: acid
K: alkaline
gas production

Front 17

E. coli

Back 17

Gram- rod
motile with peritrichous flagella,
facultative anaerobe,
indole positive
methyl red positive,
Voges-Proskauer negative
Citrate negative

lactose positive,
urea negative
oxidase negative

Front 18

Klebsiella sp.

Back 18

Gram negative rod,
non-motile,
facultative anaerobe,
indole positive
Methyl red negative,
Voges-Proskauer positive, citrate positive

lac+
oxidase negative
urea positive

Front 19

E. aerogenes

Back 19

Gram negative rod
motile with peritrichous flagella
facultative anaerobe,

indole negative,
methyl red negative
Voges-Proskauer positive
Citrate positive

lactose +
oxidase -
urea-

Front 20

Psuedomonas aueruginosa

Back 20

Gram- rod
motil with monotrichous flagella
strict aerobe

indole negative
methy red negative
Voges-Proskauer negative
Citrate positive

lac-
oxidase+
urea+/-

Front 21

Proteus vulgaris

Back 21

Gram-rod,
motile with peritrichous flagella
facultative anaerobe,

indole +/-
methyl red positive
Voges-Proskauer negative
citrate +/-

lactose-
oxidase-
urea+

Front 22

which organisms are able to ferment lactose

Back 22

Escherichia coli and Klebsiella (occasional pathogen) and Enterobacter aerogenes (normal flora)

Front 23

Which biochemical test would be necessary to perform to separate Psuedomonas aeruginosa from Proteus vulgaris

Back 23

methyl red test
oxidase

Front 24

Which biochemical tests would be necessary to perform to separate E coli from E. aerogenes

Back 24

IMViC test

Front 25

Two pieces of information obtained from MacConkey agar

Back 25

1.Selective: only Gram negative organism can grown on MacConkey;
2. Differential: contains a color indicator that will cause the colonies to turn purple if the organism is able to ferment lactose (lower the ph); if the organism is unable to ferment lactose the colonies will not be purple.