Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

micro 187 maddie > 7.8 ENTEROBACTERIACEAE > Flashcards

7.8 ENTEROBACTERIACEAE Flashcards

1
Q

ENTEROBACTERIACEAE

A

 Gram negative bacilli (“enterics”, “GNB”, “neg b’s”)
 Facultative anaerobes
 Mesophilic
 Reduce nitrate to nitrite
 Peritrichous flagella (if motile)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

some background

A

Those that
commonly cause
human GI tract
(enterics) or cause
human infections

interchange with

Those that colonize
humans but are
rarely associated
with infections, are
environmentals or
animal colonizers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

GROWTH ON URINE MEDIA

BA

A
  • Large grey glistening
  • Large grey glistening
    mucoid (capsule)
  • Beta/gamma-hemolytic
  • Pigmented (Serratia
    sp.)
  • Swarming (Proteus sp.)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

MAC

A
  • LF
  • NLF
  • Mucoid (capsule)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

CLED

A
  • LF
  • NLF
  • Mucoid (capsule)
  • *no swarming of
    Proteus sp
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how will a MAC plate look when its LF vs NLF

A

pink if LF and colorless if not

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

CLED LF vs not

A

LF is yellow
not is colorless on a blue plate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

EPIDEMIOLOGY/ clin sig for ENTEROBACTERIACEAE

A

 Infections are often endogenous (GIT colonizers move to sterile site)
 Can also pass person-to-person (usually nosocomial)
 Some species are strict pathogens – cause gastrointestinal infections,
acquired via oral or fecal-oral route

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

PATHOGENESIS

A

For UTIs – concern lies with opportunistic pathogens
Escherichia coli
* Most common
cause of UTI

Common
opportunists
* Citrobacter spp.
* Enterobacter spp.
* Klebsiella sp.
* Proteus spp.
* Serratia spp

*Virulence Factors
* Endotoxins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

IDENTIFICATION OF ENTEROBACTERIACEAE

A

 More than 50 biochemical tube tests available
 Commercial panels of mini tests can now be used (manual, semi-automated,
automated)
 Inoculate, incubate, read, discard
 Need extensive computer database (so many species!)
 Definitive ID can be made by molecular methods (done at reference labs)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

API strip not sure if we need the pos / neg but on slide 23

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

AUTOMATED MINI BIOCHEMICAL TEST
ANALYZER
called

A

VITEK

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

ESCHERICHIA COLI

A

 NF of the GIT and sometimes female GT
 Opportunistic, some strains may be strict pathogens
 Indicated in UTI, wounds, pneumonia, sepsis, meningitis (neonates)
 Most frequent Enterobacteriaceae in nosocomial infections
 Most frequent cause of UTI (endogenous)
 BA – large grey glistening, beta/gamma hem
 MAC/CLED – LF (dry)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

KLEBSIELLA SPP.

A

 NF of GIT
 Indicated in UTI, pneumonia, septicemia
 BA – large grey glistening/grey mucoid, gamma hem
 MAC/CLED – LF (mucoid)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

ENTEROBACTER SPP

A

 NF of the GIT
 Also found in soil and water
 Indicated in UTI, RT, and cutaneous infections
 BA – large grey glistening/grey mucoid, gamma hem
 MAC/CLED – LF (mucoid)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

SERRATIA MARCESCENS

A

 Nosocomial opportunist
 Indicated in UTI, pneumonia, septicemia
 Multiple resistance to antibiotics
 BA – large grey glistening, large pigmented (usually red-orange), gamma hem
 MAC/CLED – late LF (pigmented)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

CITROBACTER FREUNDII

A

 NF of GIT
 Indicated in UTI, wound and RT, bacteremia, endocarditis, meningitis, and brain
abscesses (mainly in immunocompromised patients)
 BA – large grey glistening, gamma hem
 MAC/CLED – late LF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

PROTEUS SPP.

A

 Tribe: Proteae
 NF of GIT
 Indicated in UTI
 Proteus mirabilis – wound infections
 Proteus vulgaris – infections in immunocompromised hosts (especially post-antibiotics)
 BA – large grey glistening or grey swarming, gamma hem
 MAC/CLED – NLF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

MORGANELLA MORGANII

A

 Tribe: Proteae
 NF of GIT
 Indicated in UTI, wound infections
 BA – large grey glistening, gamma hem
 MAC/CLED – NLF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

PROVIDENCIA SPP

A

 Tribe: Proteae
 NF of GIT
 Indicated in UTI
 BA – large grey glistening, gamma hem
 MAC/CLED – NLF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

BACTERIAL IDENTIFICATION
purpose

A

 Determines clinical significance
 Guides physician care
 Determines need for antimicrobial susceptibility (AMS) testing
 Determines appropriate antimicrobials for treatment
 Determines if AMS profiles are unusual
 Alerts Public Health or Infection Control risk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

IDENTIFICATION SCHEME

A

molecular techs and

*Phenotypic Characteristics
* Classic approach
* Observable physical or
metabolic characteristics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

PHENOTYPIC CRITERIA 6

A

Microscopic morphology
Macroscopic morphology
Environmental requirements
Resistance/ susceptibility to antimicrobials
Nutritional requirements
Metabolic capabilities

24
Q

PHENOTYPIC CRITERIA

purpose

A

 We can use growth characteristics, microscopic morphologies and
single test results to categorize most bacterial isolates into general
groups
 Definitive ID to species often requires use of schemes that produce
metabolic profiles

25
Q

ENZYMATIC TESTS

A

 Enzymes are the “driving force” of bacterial metabolism
 Genetically encoded (the bacterium DNA tells the cell to make the
enzyme or not)
 Can detect a single enzyme or a complete pathway that utilizes
several enzymes

26
Q

enzymatic tests
single enzyme
metabolic pathway

A

Single Enzyme Tests
* Usually quick and easy
* Cannot usually ID to species
level but can be used to
determine next step in ID
scheme
* i.e. Catalase

Metabolic Pathway Tests
* Tests the metabolic pathway
that an organism takes
* Tests for the end-products
made by the pathway
* May involve several enzymes

27
Q

OXIDATION AND FERMENTATION TESTS

A

 Carbohydrate (CHO) and protein substrates
 Oxidative process requires oxygen, fermentation does not
 We look for the acid by-products in presence or absence of oxygen through a
change in colour (pH indicator)

28
Q

AMINO ACID DEGRADATION

A

 We look for enzymes that deaminate or decarboxylate amino acids
 i.e. lysine, ornithine, arginine, phenylalanine

29
Q

SINGLE SUBSTRATE UTILIZATION

A

 We can test the ability of an organism to grow in the presence of a
single nutrient or carbon source

30
Q

CITRATE UTILIZATION (SIMMON’S CITRATE)

A

 Single substrate utilization
 Tests ability of an organism to utilize sodium citrate as its only source of carbon
(and energy) and ammonium salt as its only source of nitrogen
 pH indicator – bromthymol blue
 Positive: growth (blue)
 Negative: no growth (green)

31
Q

DECARBOXYLASE TEST

A

 Tests for metabolic pathways via amino acid degradation
 The enzyme decarboxylase can cleave a carboxyl group from an amino acid
 This cleaving results in production of CO2
and an amine (alkaline end product)
 pH indicator changes colour due to alkaline end product
 Decarboxylation is an anaerobic process and requires an acid environment for
activation

32
Q

MOELLER’S DECARBOXYLASE tube contains 2

A

 Tube contains:
 Glucose
 pH indicator (bromcresol purple)
 Amino acid (lysine or ornithine)
 We cover the tubes with oil to create an anaerobic environment

33
Q

MOELLER’S DECARBOXYLASE

how it reacts

A

 Glucose in the tube is fermented by all Enterobacteriaceae
 The fermentation creates the acidic environment necessary for the decarboxylation
to occur
 Because of the fermentation, the bromcresol purple will turn from purple to
yellow a few hours after inoculation
 The acid environment created allows for the decarboxylation to occur
 The cleaving of the carboxyl group results in an alkaline pH due to the amine
produced
 The alkaline environment created causes the bromcresol purple to convert back to
purple
 Must be controlled by testing basic medium that contains only glucose and the pH
indicator
 NO amino acid present
 Should see a yellow colour in the tube if organism has fermented glucose
 If control tube is purple, test results are NOT reliable

Positive: purple
Negative: yellow

34
Q

DNA HYDROLYSIS (DNASE)

A

 Single enzyme test
 Tests the ability of the organism to hydrolyze DNA via deoxyribonuclease
(Dnase)
 Agar plate contains polymerized DNA attached to methyl green complex
 If DNA is hydrolyzed, methyl green is released for the complex
 Green colour around the colony fades
 Positive: clear halo around colony
 Negative: no clear halo
 Positive controls: S. aureus, Serratia
marcescens, Moraxella catarrhalis

35
Q

INDOLE PRODUCTION (TUBE METHOD)

A

 Determines an organism’s ability to produce indole from tryptophan
 Upon addition of Kovac’s reagent (p-dimethylaminobenzaldehyde), tube will show
a bright pink ring

Tryptophan (tyrprophanase)
Indolepyruvic acid (deaminiation)
Indole + Pyruvic acid

36
Q

INDOLE PRODUCTION (SPOT METHOD)

A

 Single enzyme test
 Determines an organism’s ability to produce indole from tryptophan via
tryptophanase
 Breakdown products are pyruvic acid, ammonia and indole
 Indole reacts with 1% p-dimethylaminocinnamaldehyde → blue-green colour
 Must be performed from BA (or other media with tryptophan)

 Saturate filter paper with Spot Indole reagent
 Add unknown organism with stick or loop
 Read colour within 20-30 seconds
 Positive: blue-green
 Negative: no colour change

37
Q

MOTILITY TEST METHOD

A

 Determines if an organism possess a flagellum (or flagella)
 Tube test contains semi-solid agar (<0.4%) to allow for movement
 Touch one colony and stab part way down with a straight wire
 Incubate at 35-37°C for 18-24 hours
 Positive: growth spreading out from stab line
 Negative: no growth away from stab lin

38
Q

MOTILITY TEST (BROTH METHOD)

A

 Combines three tests into one semi-solid media tube:
 Motility
 Indole
 Lysine decarboxylase

 Usually contains bromcresol purple indicator
 Touch one colony and stab part way down with a straight wire
 Incubate at 35-37°C for 18-24 hours
 Add Kovac’s reagent after reading motility and lysine to visualize
indole result

39
Q

ONPG

A

 Permease: allows lactose to enter the bacterial cell
 β-galactosidase: breaks down lactose to glucose and galactose

 LF possess both enzymes (can ferment quickly)
 LLF possess only β-galactosidase (can ferment but just slower)

 Determines if an organism possesses β-galactosidase and therefore confirms its ability to ferment lactose
 β-galactosidase hydrolyzes the substrate ONPG to orthonitrophenol (yellow)
 Positive: yellow
 Negative: no colour change

40
Q

OXIDASE TEST

A

 Single enzyme method
 Used most often to differentiate between groups of Gram negative bacteria
 Determines if an organism possesses the enzyme cytochrome oxidase
 Aerobic process

 Substrate: 1% tetramethyl-p-phenylenediamine dihydrochloride
 If the organism possesses the enzyme, the substrate is oxidized to indophenol
causing a colour change

 Positive: dark purple
 Negative: no colour change

41
Q

OXIDASE TEST METHOD
false neg and pos

A

False negatives
* Colonies >24 hours old
* Test done from selective
medium or medium
containing glucose (i.e.
MAC)

False positives
* Iron or chromium loop
(use wooden sticks)
* Auto-oxidized reagent

42
Q

OXIDASE TEST METHOD

filter papepr

disc or strips

swabs

A

Filter Paper
* Saturate a filter paper with substrate
* Rub organism on and read within 10 seconds

Disc or strips
* Impregnated with substrate

Swab
* Add reagent after swabbing colonies

43
Q

PHENYLALANINE DEAMINASE (PPA)

A

 Amino acid degradation test
 Determines an organism’s ability to oxidatively deaminate phenylalanine to
phenylpyruvic acid (PPA)
 Inoculate by streaking up slant and incubate for 18-24 hours at 35-37°C
 PPA is detected with 10% ferric chloride (FeCl3)

 Positive: dark green after addition of FeCl3
 *All Tribe Proteae are positive
 Negative: no change with addition of FeCl3

44
Q

TRYPTOPHANE DEAMINASE

A

 Amino acid degradation test
 Determines an organism’s ability to deaminate tryptophane to indolepyruvic acid
 Indole pyruvic acid turns brown in the presence of 10% ferric chloride (FeCl3)

 Positive: brown after addition of FeCl3
 Negative: no colour change

45
Q

TSI (TRIPLE SUGAR IRON) AGAR

whats in it

A
  • 1 part glucose (0.1%)
  • 10 parts lactose (1%)
  • 10 parts sucrose (1%)
  • Peptone (provides nitrogen)
  • Phenol red (pH indicator)
  • Ferric sulfate
  • Sodium thiosulfat
46
Q

TSI (TRIPLE SUGAR IRON) AGAR METHOD

A

 Determines if suspect organism can ferment sugars and produce gas and
hydrogen sulfide
 Inoculation:
 Stab to bottom of butt (ANO2)
 Streak up surface of slant (O2)
 Incubate no longer than 24 hours with cap loosened

 All Enterobacteriaceae ferment glucose
 After 8-12 hours of incubation, the small
amount of glucose will be fermented and
acid end products will cause a change in
the phenol red indicator from red to yellow
in the slant and butt

47
Q

TSI (TRIPLE SUGAR IRON) AGAR

 If the organism can only ferment glucose.

A

 After ~12 hours, the pH changes on the slant
due to the oxidation of peptone to amines
 CO2
and H2O products cause the oxidation of
the fermentation products
 Slant reverts to red (butt still yellow)

48
Q

TSI (TRIPLE SUGAR IRON) AGAR
 If the organism can ferment glucose and lactose
and/or sucrose..

A

 There is a large volume of acid end products
 Any amines produced are neutralized by the large
amount of acid
 Even after ~12 hours, slant remains yellow

49
Q

TSI AGAR – GAS PRODUCTION
 If the organism also produces CO2
and/or H2 gas..

A

 There will be bubbles or cracks in agar
 There may be separation of agar from
inner surface of tube

50
Q

TSI AGAR – H2
S PRODUCTION

 Bacteria may produce H2S if given the raw
materials.

A

 H2 gas + Na thiosulfate → H2S (colorless)
 H2S + ferric sulfate = black precipitate
 MUST have an acidic environment for this reaction to
occur
 Acid environment provided by fermentation of sugars
(will only see in butt if glucose is the only sugar
fermented)

51
Q

TSI (TRIPLE SUGAR IRON) AGAR

incubation time and oxygen recs

A

 Do not incubate >24 hours
 Oxidation products will eventually overwhelm acids and tube will revert to red
 Be sure to provide atmospheric oxygen to allow for peptone
metabolism on slant and gas formation (loose caps)

52
Q

UREA HYDROLYSIS (CHRISTENSEN’S METHOD)

A

 Single enzyme test
 Determines the ability of an organism to hydrolyze urea by the enzyme urease
 Tube contains broth or agar with urea as primary carbon source
 Urea → ammonia + CO2 + H2O
 Ammonia causes the pH of the medium to increase (alkaline)
 Phenol red indicator turns magenta

 Inoculate by streaking up the slant of the agar
 Incubate for 18-24 hours at 35-37C
 Positive: magenta
 Negative: light orange or yellow

53
Q

METHYL RED/VOGES PROSKAUER

A

 Methyl Red Test
 Tests for lactic, formic, and acetic acids produced after glucose utilization
 We will not be performing this test

54
Q

VOGES PROSKAUER

A

 Looking for neutral end products of glucose utilization
 Glucose fermentation follows the EMP metabolic pathway resulting in the end
product pyruvic acid
 Pyruvic acid can further follow the butylene glycol pathway with acetoin as its
neutral end product
 After the addition of 40% KOH, acetoin is converted to diacetyl
 Diacetyl + 𝛼-napthol reagent + guanido group forms a red complex

Acetoin (40% KOH) Diacetyl Red (a-napthol) complex

55
Q

VOGES PROSKAUER

A

-Positive: red colour after addition of 40% KOH and α-naphthol
 Negative: yellow or no colour change

micro 187 maddie (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions