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Bacteriology > General Bacteriology > Flashcards

General Bacteriology Flashcards

1
Q

What are commensals?

A

Microorganisms living on or within humans that do not harm the host under normal circumstances and may even be beneficial

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2
Q

How can commensals be beneficial?

A

Inhibiting growth of pathogens
Aiding in digestion

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3
Q

Name normal skin flora

A

Staph epidermidis

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4
Q

Name normal nasal flora

A

Staph epidermidis

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5
Q

Name normal oropharyngeal flora

A

Viridans group strep

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6
Q

Name normal flora of dental plaques

A

Strep mutans

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7
Q

Name normal gut flora

A

E coli
Bacteroides

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8
Q

Name normal vaginal flora

A

Lactobacillus acidophilus

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9
Q

Name normal lung flora

A

Neisseria catarrhalis
Alpha hemolytic strep
Staph
Non-pathogenic corynebacteria
Candida albicans

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10
Q

What are transient flora and give examples

A

Microorganisms that are temporarily present
E coli or s aureus on the hands

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11
Q

How can pathogens be differentiated?

A

Facultative versus obligate pathogens

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12
Q

What are facultative pathogens?

A

Microorganisms capable of survival outside of a host

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13
Q

Give examples of facultative pathogens

A

E coli
Vibrio cholera
Pseudomonas aeruginosa

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14
Q

Give examples of opportunistic pathogens

A

Oral candida
PJP
CMV
Cryptococcus
Toxoplasma encephalitis

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15
Q

What are obligate pathogens?

A

Microorganisms that can only replicate inside the cells of a host and therefore must infect a host to survive

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16
Q

Give examples of obligate pathogens

A

Salmonella
T pallidum
Mycobacterium tuberculosis

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17
Q

Which fatty acid can be found in the cell walls of acid fast bacteria?

A

Mycolic acid

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18
Q

Which enzyme cross links peptide side chains?

A

Transpeptidase

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19
Q

What is peptidoglycan?

A

A polymer chain of the sugars, n-acteyl-muramic acid and n-acetyl-glucosamine, and amino acids

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20
Q

What does lipoteichoic acid stimulate the release of?

A

TNF-alpha
IL-1
IL-6

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21
Q

Which endotoxin does the outer membrane of gram negative bacteria contain?

A

Lipopolysaccharide (LPS)

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21
Q

What is LPS composed of?

A

Lipid A
Core polysaccharide
O antigen

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22
Q

Which component of LPS is antigenic?

A

Lipid A

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23
Q

What does lipid A stimulate the release of?

A

TNF-alpha
IL1
IL6

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24
Q

Which layer are penicillin binding proteins found in?

A

Cytoplasmic membrane

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25
Q

The cytoplasmic membrane is __________ (hydrophobic/hydrophilic)?

A

Hydrophobic

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26
Q

The bacterial capsule is __________ (hydrophobic/hydrophilic)?

A

Hydrophilic

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27
Q

Which polypeptide component does bacillus anthracis contain in its bacterial capsule?

A

Poly-D-glutamate

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28
Q

What does the bacterial capsule protect against?

A

Phagocytosis
Complement mediated lysis

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29
Q

What is a glycocalyx?

A

A glycoprotein-polysaccharide layer that covers the cell membrane

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30
Q

What is the function of the glycocalyx?

A

Adhesion of bacteria to cell and foreign surfaces

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31
Q

What does the periplasm contain?

A

Beta lactamase

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32
Q

Which bacteria are spore formers?

A

Gram positive

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33
Q

What does the coating later of endospores contain?

A

Keratin
Dipicolinic acid
Peptidoglycan
DNA

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34
Q

What do endospores protect against?

A

Dehydration
Temperature damage
Chemical damage

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35
Q

Give reasons for poor gram staining of atypical bacteria

A

Lack of cell wall
Atypical cell wall composition
Very thin cell wall
Intracellular bacteria

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36
Q

Give examples of bacteria lacking a cell wall

A

Mycoplasma
Ureaplasma

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37
Q

Give an example of a bacteria with high lipid percentage in its cell wall

A

Mycobacteria

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38
Q

Give an example of a bacteria lacking peptidoglycan in its cell wall?

A

Chlamydia

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39
Q

Give an example of a bacteria lacking LPS in its cell wall

A

Treponema

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40
Q

Give an example of a bacteria with a very thin cell wall

A

Leptospira

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41
Q

Name the two types of acid fast staining

A

Ziehl Neelsen (red)
Auramine rhodamine (yellow-red)

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42
Q

Which element of acid fast bacteria is stained?

A

Mycolic acid in the cell wall

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43
Q

Differentiate between obligate and facultative intracellular bacteria

A

Obligate - cannot produce ATP outside of host cell
Facultative - can produce ATP outside of host cell

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44
Q

Give examples of obligate intracellular bacteria

A

Rickettsia
Chlamydia
Coxiella

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44
Q

Give examples of facultative intracellular bacteria

A

Mycobacterium
Salmonella
Neisseria
Listeria
Francisella
Legionella
Yersinia
Brucella

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44
Q

Define obligate anaerobes

A

Grows only in absence of oxygen

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45
Q

Why are obligate anaerobes susceptible to oxidative damage

A

Lack of enzymes that can detoxify oxygen radicals

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45
Q

Why do obligate anaerobes often produce a foul smell?

A

Short chain fatty acids and gases (CO2 and H2)

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46
Q

Define facultative anaerobes

A

Can use oxygen for ATP generation but may switch to anaerobic metabolism when necessary

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47
Q

Give examples of obligate anaerobes

A

Foul Anaerobes Can’t Breathe

Fusobacterium
Actinomyces israelii
Clostridium
Bacteroides

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48
Q

Give examples of aerobic bacteria

A

Pseudo aeruginosa
Myco tuberculosis
Bordetella pertussis
Nocardia

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49
Q

Why is alpha hemolysis green?

A

Hemoglobin partially oxidized by hydrogen peroxide to methemoglobin which contains biliverdin

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50
Q

Give examples of alpha hemolytic bacteria

A

S pneumo
S viridans

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51
Q

Give examples of beta hemolytic bacteria

A

S aureus
S pyogenes
S agalactiae

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52
Q

Which bacteria in the Lancefield grouping falls under Group A?

A

S pyogenes

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53
Q

Which bacteria in the Lancefield grouping falls under Group B?

A

S agalactiae

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54
Q

Which bacteria in the Lancefield grouping falls under Group C?

A

S equisimilis
S equi
S zooepidemicus
S dysgalactiae

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55
Q

Which bacteria in the Lancefield grouping falls under Group D?

A

Enterococci
S bovis

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56
Q

Which bacteria in the Lancefield grouping falls under Group E?

A

S milleri
S mutans

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57
Q

Which bacteria in the Lancefield grouping falls under Group F?

A

S anginosus

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58
Q

Which bacteria in the Lancefield grouping falls under Group G?

A

S canis
S dysgalactiae

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59
Q

Which bacteria in the Lancefield grouping falls under Group H?

A

S sanguinis

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60
Q

Which bacteria in the Lancefield grouping falls under Group L?

A

S dysgalactiae

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61
Q

Which bacteria in the Lancefield grouping falls under Group N?

A

Lactococcus lactis

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62
Q

Which bacteria in the Lancefield grouping falls under Group R & S?

A

Streptococcus suis

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63
Q

Which is the only bacteria which exhibits growth in bile esculin agar as well as 6.5% NaCl?

A

Group D streptococci

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64
Q

Discuss the principles of the indole test

A

Indole test determines the ability of a microorganism to produce indole from the breakdown of tryptophan. Tryptophan is hydrolyzed by tryptophanase to produce indole, pyruvate or ammonium ion. Indole reacts with Kovac’s agent under acidic conditions to produce a red dye

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65
Q

Explain Kovac’s agent

A

Contains para-dimethylaminobenzaldehyde and isoamyl alcohol
Para-dimethylaminobenzaldehyde reacts with indole to produce rosindole red dye
Isoamyl alcohol forms a complex with the dye causing it to precipitate

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66
Q

What colour does indole positive turn?

A

Pink

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67
Q

What colour does indole negative stay?

A

Yellow

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68
Q

What is an antibiogram?

A

Microbiological test that assesses the susceptibility of pathogen to various antibiotics

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69
Q

What is MIC?

A

Lowest concentration of antimicrobial that inhibits the growth of a specific microorganism isolate

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70
Q

What is generation time?

A

Time required by bacteria to double in number in a culture

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71
Q

What does generation time depend on?

A

Species of bacterium
Type of culture medium

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72
Q

Specify types of culture media

A

Selective media
Indicator media

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73
Q

What does Thayer-Martin agar contain?

A

Vancomycin (inhibits gram +)
Trimethoprim (inhibits gram -)
Colisitin (inhibits gram -)
Nystatin (inhibits fungi)

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74
Q

Which pathogen is isolated using Thayer-Martin agar?

A

Neisseria spp

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75
Q

Describe the colony morphology of neisseria gonorrhoea

A

Small size
Define margins
Mucoid appearance
Colourless/grayish-white colonies
Smooth consistency

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76
Q

Describe the colony morphology of neisseria meningitidis

A

Medium to large
Mucoid appearance
Blue-gray colour

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77
Q

What does MacConkey agar contain?

A

Lactose
Bile salts
Sodium chloride
pH indicator

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78
Q

What does MacConkey agar isolate?

A

Lactose fermenters

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79
Q

Describe the colony morphology of lactose fermenters

A

Pink colonies (fermentation to hydrogen sulphide which is acidic)

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80
Q

Which pathogen is isolated on Bordet-Gengou agar?

A

Bordetella pertussis

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81
Q

What does Bordet-Gengou agar contain?

A

Potato extract
Sheep blood
Glycerol

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82
Q

Describe the colony morphology of bordetella pertussis on Bordet-Gengou agar

A

Small
Round
Shiny
Mercury-silver appearance

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83
Q

Which pathogen is isolated on Regan-Lowe medium?

A

Bordetella pertussis

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84
Q

What does Regan-Lowe medium contain?

A

Blood
Charcoal
Antibiotics

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85
Q

Describe the colony morphology of bordetella pertussis on Regan-Lowe medium

A

Small
Glistening
Greyish-white

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86
Q

Which pathogen is isolated on chocolate agar?

A

Haemophilus influenza and fastidious organisms

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87
Q

What does chocolate agar contain?

A

X factor (haematin)
V factor (NAD+)

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88
Q

What is NAD?

A

Nicotinamide adenine dinucleotide

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89
Q

Describe the colony morphology of haemophilus influenzae on chocolate agar

A

Small
Pale-grayish
Mucoid
Coccobacillary shape

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90
Q

Which pathogen is isolated on Eaton agar?

A

Mycoplasma pneumonia

91
Q

What does Eaton agar contain?

A

Cholesterol

92
Q

Describe the colony morphology of mycoplasma pneumonia on Eaton agar

A

Fried egg appearance

93
Q

Which pathogen is isolated on cystine-tellurite agar?

A

Corynebacterium diptheriae

94
Q

What does cystine-tellurite agar contain?

A

Animal tissue
Sodium chloride
L-cystine
Sodium thiosulfate

95
Q

Describe the colony morphology of corynebacterium diptheriae on cystine-tellurite agar

A

Black colonies with a brown halo

96
Q

Which pathogen is isolated on Loffler medium?

A

Corynebacterium diptheriae

97
Q

What does Loffler medium contain?

A

Dextrose
Beef extract
Horse extract
Sodium chloride
Proteose peptone

98
Q

Describe the colony morphology of corynebacterium diphteriae on Loffler medium

A

Cream-coloured
Raised centers
Dark blue metachromatic granules with methylene blue stain

99
Q

Which pathogen is isolated on eosin methylene blue agar?

A

E coli

100
Q

What does eosin methylene blue agar contain?

A

Lactose
Dipotassium phosphate
Eosin
Methylene blue

101
Q

Describe the colony morphology of e coli on eosin methylene blue agar

A

Green metallic sheen

102
Q

Which pathogens are isolated on charcoal yeast extract agar

A

Legionella
Pastuerella
Brucelle
Francisella

103
Q

What does charcoal yeast extract agar contain?

A

Charcoal
Yeast
Cysteine
Iron

104
Q

Describe the colony morphology of legionella on charcoal yeast extract agar

A

Smooth surface
Precise edges
White-gray to blue-gray

105
Q

Describe the colony morphology of pastuerella on charcoal yeast extract agar

A

Moderate size
Smooth
Greyish

106
Q

Describe the colony morphology of brucella on chocolate yeast extract agar

A

Small
Smooth
Slightly yellowish

107
Q

Describe the colony morphology of francisella

A

Tiny
Pinpoint
Gray-white, translucent or opaque

108
Q

Which pathogen is isolated on Lowenstein-Jensen agar?

A

M. tuberculosis

109
Q

What does Lowenstein-Jensen agar contain?

A

Potato extract
Egg suspension
Asparagine
Glycerol
Malachite green
Penicillin
Nalidixic acid

110
Q

Describe the colony morphology of m tuberculosis on Lowenstein-Jensen agar

A

Small
Brownish
Granular
“Buff, rough and tough”

111
Q

Which pathogen is isolated on Middlebrook agar?

A

M tuberculosis

112
Q

What does Middlebrook agar contain?

A

Inorganic salts
Oleic acid
Albumin

113
Q

Describe the colony morphology of m tuberculosis on Middlebrook agar

A

Small
Brownish
Granular
“Buff, rough and tough”

114
Q

Which pathogen is isolated on Hektoen enteric agar?

A

Enteric eg salmonella, shigella

115
Q

What does Hektoen enteric agar contain?

A

Proteose peptone
Sugars (lactose, sucrose, salicin)
Sodium thiosulfate
Iron ammonium citrate

116
Q

Describe the colony morphology of salmonella on Hektoen enteric agar

A

Black colonies

117
Q

Describe the colony morphology of shigella on Hektoen enteric agar

A

Green colonies

118
Q

Which pathogen is isolated on triple sugar iron agar?

A

Enteric bacteria eg salmonella, shigella

119
Q

What does triple sugar iron agar contain?

A

Fermentable sugars (lactose, sucrose, glucose)
Iron

120
Q

Which pathogen is isolated on mannitol salt agar?

A

Gram positives (specifically staph spp)

121
Q

What does mannitol salt agar contain?

A

High level of salt

122
Q

Describe the colony morphology of s aureus on mannitol salt agar

A

Golden yellow

123
Q

Which pathogen is isolated on bile esculin agar?

A

S gallolyticus
Enterococcus

124
Q

What does bile esculin agar contain?

A

Bile
Esculin
Ferric citrate

125
Q

Describe the colony morphology of s gallolyticus and enteroccocus spp on bile esculin agar

A

Blackening of medium

126
Q

Which pathogen is isolated on thiosulfate citrate bile salts sucrose agar?

A

Vibrio spp
Enterococcus spp

127
Q

What does thiosulfate citrate bile salts sucrose agar contain?

A

Sodium thiosulfate
Sodium citrate
Sodium chloride
Saccharose
Proteose peptone

128
Q

Describe the colony morphology of vibrio and enterococcus spp on thiosulfate citrate bile salts sucrose agar

A

Round
Smooth
Glistening
Slightly flattened
Yellow

129
Q

What is catalase?

A

An enzyme that breaks down hydrogen peroxide into water and oxygen which prevents its breakdown into microbiocidal substances via myeloperoxidase

130
Q

Name catalase positive organisms

A

Staphylococci
E coli
Nocardia
Serratia
Listeria
Pseudomonas
Bukholderia cepacia
H pylori
Bordetella pertussis
Candida
Aspergillus

131
Q

Which chronic disease results in recurrent infections with catalase positive organisms?

A

Chronic granulomatous disease

132
Q

What is coagulase?

A

An enzyme that converts fibrinogen into fibrin

133
Q

What is oxidase?

A

An enzyme that catalyzes the donation of hydrogen atoms of oxygen, forming water or hydrogen peroxide

134
Q

Name oxidase positive organisms

A

Campylobacter
Vibrio
Pseudomonas
Brucella

135
Q

What is oxidase also known as?

A

Cytochrome c oxidase

136
Q

What is urease?

A

An enzyme that hydrolyzes urea to ammonia and carbon dioxide, increasing pH

137
Q

Name urease producing organisms

A

Proteus
H pylori
Ureaplasma
Nocardia
Klebsiella
S epidermidis
S saprophyticus
Cryptococcus

138
Q

Name pigments produced by pseudomonas aeruginosa

A

Pyoverdin
Pyocyanin

139
Q

What pigment is produced by serratia marcescens?

A

Red pigment

140
Q

What pigment is produced by actinomyces israelii?

A

Yellow sulfur granules

141
Q

What pigment is produced by staph aureus?

A

Yellow pigment

142
Q

Name indirect serology methods

A

Qualitative antibody detection
Titer development
T cell reaction detection (interferon y release assay)

143
Q

Define plasmids

A

Bacterial nonchromosomal DNA fragments that replicate independently from chromosomal replication

144
Q

Define integrons

A

Bacterial nonchromosomal DNA that cannot replicate independently and require integrase to integrate into chromosomal bacteria

145
Q

Define pathogenicity islands

A

A group of genes assoc with virulence factors such as adhesins and toxins

146
Q

Name intracellular mechanisms of genetic variability of bacteria

A

High mutation rate
Homologous recombination

147
Q

What is homologous recombination?

A

Exchange of larger gene segments between bacteria that have a similar gene sequence

148
Q

Name intercellular mechanisms of genetic variability of bacteria

A

Bacterial transformation
Bacterial conjugation
Hfr cell mediated conjugation
Bacterial transduction
Bacterial transposition

149
Q

Explain bacterial transformation

A

Uptake of free segments of naked bacterial DNA released by cell lysis from the surroundings through the cell membrane -> combination of new DNA material with bacterial pre-existing DNA -> degradation of unused DNA -> expression of new genes -> transformation

150
Q

Name bacteria that undergo transformation

A

Neisserie
Haemophilus influenzae type B
Strep pneumo

151
Q

Explain bacterial conjugation

A

Transfer of plasmids by a bridge-like connection between 2 bacteria

152
Q

What is F factor?

A

Fertility factor, a bacterial plasmid that enables transfer of genetic material between bacteria

153
Q

What are Hfr cells?

A

High frequency recombination cells
Bacteria with a conjugative plasmid integrated into their chromosomal DNA

154
Q

Explain conjugation mediated by Hfr cells

A

Hfr bacteria connect with F- bacteria via the sex pilus -> transfer and replication of DNA material on recipient F- bacteria -> new genes on F- bacteria

155
Q

Define bacteriophages

A

Viruses that only infect bacteria

156
Q

Explain bacterial transduction

A

The process of gene transfer between bacteria via bacteriophages
Can be generalized or specialized

157
Q

How do generalized and specialized transduction differ?

A

Generalized - any portion of bacterial genome transferred
Specialized - specific portion of bacterial genome transferred

158
Q

Explain the process of generalized transduction

A

Bacteriophage attaches to bacterial cell well and injects its DNA into bacterium -> cleavage of bacterial DNA and replication of viral DNA -> formation of new bacteriophages with phage capsids containing fragments of bacterial DNA -> lysis of bacterium and release of bacteriophages -> bacteriophages infect other bacteria

159
Q

Explain the process of specialized transduction

A

Bacteriophage infects bacteria -> viral DNA incorporated into the bacterial DNA at a specific location but remains inactive (prophage stage) -> upon activation, the viral DNA is replicated and excised from bacterial genome with flanking bacterial DNA -> excised DNA is incorporated in new bacteriophage capsids -> lysis of bacterium and release of new bacteriophages -> bacteriophages infect other bacteria

160
Q

Name toxins that are transferred via specialized transduction

A

Erythrogenic toxin (s. pyogenes)
Cholera toxin
Diphtheria toxin
Shiga toxin
Botulinum toxin

161
Q

What is bacterial transposition?

A

Exchange of genetic information via transposons within the genome or between genomes of various bacteria

162
Q

Define transposons

A

Bacterial DNA sequence that cannot replicate independently

163
Q

Which gene is transferred from VRE enterococcus to VRSA?

A

vanA gene

164
Q

Which bacteria are capable of bacterial transformation?

A

SHIN

Strep pneumo
Haemophilus Influenzae
Neisseria

165
Q

How do you calculate virulence?

A

Dividing number of individuals who become severely ill or die due to an infection by total number of individuals who have contracted the disease

166
Q

Name virulence factors that aid in bacterial colonization

A

Lipoteichoic acid (LTA)
Bacterial adhesins
Biofilm
Flagella

167
Q

How does LTA increase inflammation?

A

Functions as a ligand of toll like receptor 2, stimulating TNF-alpha production

168
Q

Name examples of bacterial adhesins

A

Pertussis toxin
Hemagglutinins

169
Q

What are peritrichous flagella?

A

Flagella around the bacterium

170
Q

Give an example of a bacterium with peritrichous flagella

A

E. coli

171
Q

What are lophotrichous flagella?

A

Several flagella at one pole

172
Q

Give an example of a bacterium with lophotrichous flagella

A

Pseudomonas

173
Q

What are polar flagella?

A

One flagellum at one of the bacterial poles

174
Q

Give an example of a bacterium with polar flagella

A

Vibrio cholerae

175
Q

How does IgA protease assist with colonization of mucous membranes?

A

Cleaves mucosal IgA

176
Q

Name bacteria with IgA protease

A

Neisseria
Haemophilus influenzae
S pneumo

177
Q

How does Protein A function?

A

Found in bacterial cell well
Binds to Fc region of mainly IgG to prevent immunoglobulin binding to complement or host leucocytes -> inhibits phagocytosis, complement fixation and antibody-dependent killing mechanisms

178
Q

How does M protein assist with avoiding the immune system?

A

Prevents opsonization by C3b -> inhibits phagocytosis and alternative complement activation

179
Q

How is the secretion of siderophores a virulence factor?

A

Chelate and import iron

180
Q

Give examples of virulence factors

A

Colonization
Avoidance of immune system
Bacterial nutrition
Antigenic variation
Intracellular survival
Type III secretion system
Inflammatory response

181
Q

Which bacteria inhibits phagosome-lysosome fusion?

A

M tuberculosis

182
Q

Which bacteria exits phagosomes before fusion occurs?

A

Listeria monocytogenes

183
Q

Which bacteria have invasins?

A

Yersinia spp

184
Q

What is an injectisome?

A

Bacterial appendage that connects bacteria and immune cells and delivers bacterial toxins directly into the cell

185
Q

Which bacteria have injectisomes?

A

E coli
Salmonella
Yersinia
P aeruginosa
Chlamydia

186
Q

Compare the bacteria type of endotoxins and exotoxins

A

Endotoxin - gram negative only
Exotoxin - gram negative AND positive

187
Q

Where is the genetic information of endotoxins encoded?

A

In bacterial chromosome

188
Q

Where is the genetic information of exotoxins encoded?

A

In the plasmid or bacteriophage

189
Q

How are endotoxins released?

A

Bacterial lysis
Exocytosis

190
Q

How are exotoxins released?

A

Actively secreted by living bacteria

191
Q

Are exotoxins heat stable or heat labile?

A

Heat labile

191
Q

Are endotoxins heat stable or heat labile?

A

Heat stable

192
Q

Which exotoxins are heat stable?

A

Some e coli toxins
SEA
SEB

193
Q

What is the antigenicity of endotoxin vs exotoxin?

A

Endotoxin - low
Exotoxin - high

194
Q

What is the likelihood of causing disease of endotoxin vs exotoxin

A

Endotoxin - low
Exotoxin - high

195
Q

Which toxins form toxoid that can be modified into a toxoid vaccine?

A

Exotoxins

196
Q

Name the toxins produced by s pyogenes

A

Streptolysin O
Erythrogenic exotoxin A

197
Q

What is the mechanism of action of streptolysin O?

A

Degrades cell membranes, mainly of RBC (beta hemolysis)

198
Q

What is the mechanism of action of erythrogenic exotoxin A?

A

Binds to beta region of TCR and MHC II -> release TNF alpha, IL1, IL2, INF-y

199
Q

Name toxins produced by s aureus

A

Toxic shock syndrome toxin (TSST-1)
Exfoliative toxin
Enterotoxin B

200
Q

What is the mechanism of action of TSST-1?

A

Binds to beta region of TCR and MHC II -> release TNF alpha, IL1, IL2, INF-y

201
Q

What is the mechanism of action of exfoliative toxin?

A

Damages desmosome proteins of the stratum granulosum -> epidermolysis

202
Q

What is the mechanism of action of enterotoxin B?

A

Forms pores in enterocyte membranes -> leakage of Na+ and water into intestinal lumen

203
Q

What toxin is produced by c perfringens?

A

Alpha toxin

204
Q

What is the mechanism of action of alpha toxin?

A

Acts as a phospholipase -> degrades cell membranes and tissue

205
Q

What toxin is produced by c diphtheriae?

A

Diphtheria toxin

206
Q

What is the mechanism of action of diphtheriae toxin?

A

Inactivates EF-2 -> arrested protein translation and synthesis -> cell death and necrosis

207
Q

What toxin is produced by p aeruginosa?

A

Pseudomonas exotoxin A

208
Q

What is the mechanism of action of pseudomonas exotoxin A?

A

Inactivates EF-2 -> arrested protein translation and synthesis -> cell death and necrosis

209
Q

What toxin is produced by shigella?

A

Shiga toxin

210
Q

What is the mechanism of action of shiga toxin?

A

Removes adenine from rRNA -> inactivation of 60s ribosome -> disrupted protein synthesis -> cell death -> GI mucosal damage -> diarrhea
Enhanced cytokine release -> microthombi that occlude the arterioles and capillaries -> microangiopathic hemolytic anemia, thrombocytopenia, AKI

211
Q

What toxin is produced by enterohemorrhagic e coli (EHEC)?

A

Shiga-like toxin

212
Q

What is the mechanism of action of shiga-like toxin?

A

Removes adenine from rRNA -> inactivation of 60s ribosome -> disrupted protein synthesis -> cell death -> GI mucosal damage -> diarrhea
Enhanced cytokine release -> microthombi that occlude the arterioles and capillaries -> microangiopathic hemolytic anemia, thrombocytopenia, AKI

213
Q

Which toxin is produced by enterotoxigenic e coli?

A

Heat stable toxin
Heat labile toxin

214
Q

Which other organism produces heat labile toxin?

A

Bacillus cereus

215
Q

What is the mechanism of action of heat stable toxin?

A

Activation of guanylate cyclase -> incr cGMP -> decr NaCl reabsorption -> water efflux into intestinal lumen -> secretory diarrhea

216
Q

What is the mechanism of action of heat labile toxin?

A

Overactivates adenylate cyclase -> incr cAMP -> incr secretion of chloride and water efflux into intestinal lumen -> watery diarrhea

217
Q

What toxin is produced by v cholerae?

A

Cholera toxin

218
Q

What is the mechanism of action of cholera toxin?

A

Permanently activates Gs protein -> overactivation of adenylate cyclase -> incr cAMP -> incr secretion of chloride and water efflux into intestinal lumen -> watery diarrhea

219
Q

How is the diarrhea caused by cholera described?

A

Rice water diarrhea

220
Q

What toxin is produced by bacillus anthracis?

A

Anthrax toxin

221
Q

What is the mechanism of action of anthrax toxin?

A
  1. Edema factor (EF) binds to calcium and calmodulin and gains adenylate cyclase activity -> incr cAMP -> cell edema
  2. Lethal factor (LF) destroys MAPKK -> cell death
  3. Protective antigen binds to endothelial receptors and facilitates entry of EF and LF into host cells
222
Q

Which toxin is produced by bordetella pertussis?

A

Pertussis toxin

223
Q

What is the mechanism of action of pertussis toxin?

A

Causes ADP-ribosylation of the alpha subunit of Gi protein -> inhibition of Gi protein -> adenylate cyclase disinhibition -> cAMP accumulation -> impaired cell signaling pathways

224
Q

Which toxin is produced by c tetani?

A

Tetanospasmin

225
Q

What is the mechanism of action of tetanospasmin?

A

Acts as protease that cleaves synaptobrevin (SNARE protein) -> prevention of inhibitory NT release from Renshaw cells in spinal cord -> uninhibited activation of alpha motor neurons -> mm spasms, rigidity, autonomic instability

226
Q

Which toxin is produced by c botulinum?

A

Botulinum toxin

227
Q

What is the mechanism of action of botulinum toxin?

A

Acts as a protease that cleaves SNARE proteins and prevents fusion of transmitter-containing vesicles with the presynaptic membrane -> inhibition of Ach release from presynaptic axon terminals

228
Q

Name extrachromosomal genetic mechanisms of drug resistance

A

Resistance plasmid
Beta lactamase
Acetyltransferase
Protein pumps

Bacteriology (4 decks)

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