Basic Bacteriology Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Bacterial appendages

A

Flagellum, pilus/fimbria

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

Flagellum - chemical composition

A

Proteins

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

Flagellum - function

A

Motility

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

Pilus/fimbria - chemical composition

A

Glycoprotein

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

Pilus/fimbria - function

A

Mediate adherence of bacteria to cell surface; sex plus forms during conjugations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Bacterial specialized structures

A

Spore

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

Spore - chemical composition

A

Keratin-like coat; dipicolinic acid; peptidoglycan, DNA

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

Spore - function

A

Gram + only

Survival: resist dehydration, heat, chemicals

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

Bacterial cell envelope components

A

Capsule, glycocalyx, outer membrane, periplasm, cell wall, cytoplasmic membrane

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

Capsule - chemical composition

A

Organized, discrete polysaccharide layer (except poly-D-glutamate on B. anthracis)

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

Capsule - function

A

Protects against phagocytosis

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

Glycocalyx - chemical composition

A

Loose network of polysaccharides

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

Glycocalyx - function

A

Mediated adherence to surfaces, especially foreign surfaces (eg, indwelling catheters)

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

Outer membrane - chemical composition

A

Outer leaflet: contains endotoxin (LPS/LOS)
Embedded proteins: porins and other outer membrane proteins (OMPs)
Inner leaflet: phospholipids

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

Outer membrane - function

A

Gram - only
Endotoxin: lipid A induces TNF and IL-1; antigenic I polysaccharide component
Most OMPs are antigenic
Porins: transport across outer membrane

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

Periplasm - chemical composition

A

Space between cytoplasmic membrane and outer membrane in gram - bacteria (peptidoglycan in middle)

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

Periplasm - function

A

Accumulates components exiting gram - cells, including hydrolytic enzymes (eg, b-lactamases)

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

Cell wall - chemical composition

A

Peptidoglycan is a sugar backbone with peptide side chains cross-linked by transpeptidase

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

Cell wall - function

A

Net-like structure gives right support, protects against osmotic pressure damage

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

Cytoplasmic membrane - chemical composition

A
Phospholipid bilayer sauce with embedded proteins (eg, penicillin-binding proteins [PBPs]) and other enzymes
Lipoteichoic acids (gram + only) extend from membrane to exterior
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Cell wall components - unique to gram +

A

Lipoteichoic acid

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

Cell wall components - common to both

A

Flagellum, pilus, capsule, cell wall, peptidoglycan, cytoplasm

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

Cell wall components - unique to gram -

A

Outer membrane: endotoxin/LPS, porin

Periplasmic space: b-lactamase location

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Bacterial taxonomy - morphologies

A

Spherical (coccus), rod (bacillus), branching filamentous, pleomorphic (no cell wall), spiral (spirochetes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Coccus - gram + examples

A

Staphylococcus (clusters), Streptococcus (chains or pairs), Enterococcus (pairs or short chains)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Coccus - gram - examples

A

Moraxella catarrhalis, Neisseria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Bacillus - gram + examples

A

Bacillus, Clostridium, Corynebacterium, Gardnerella (gram variable), Lactobacillus, Listeria, Mycobacterium (acid fast), Propionibacterium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Bacillus - gram - examples (enteric)

A

Bacteroides, Campylobacter, E coli, Enterobacter, Fusobacterium, Helicobacter, Klebsiella, Proteus, Pseudomonas, Salmonella, Serratia, Shigella, Vibrio, Yersinia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Bacillus - gram - examples (respiratory)

A

Bordetella, Burkholderia cepacia, Haemophilus (pleomorphic), Legionella (silver stain)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Bacillus - gram - examples (zoonotic)

A

Bartonella, Brucella, Francisella, Pasteurella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Branching filamentous - gram + examples

A

Actinomyces, Nocardia (weakly acid fast)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Pleomorphic - gram - examples

A

Anaplasma, Ehrlichia, Chlamydiae (Giemsa), Rickettsiae (Giemsa), Mycoplasma (contains sterols, which do not gram stain)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Spirochetes - gram - examples

A

Borrelia (Giemsa), Leptospira, Treponema

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Stains

A

Gram, Giemsa, Periodic acid-Schiff, Ziehl-Neelsen (carbol fuchsin), India ink, silver, fluorescent antibody

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Gram stain

A

First-line lab test in bacterial identification
Bacteria with thick peptidoglycan layer retain crystal violet dye (gram +)
Bacteria with thin peptidoglycan layer turn red or pink (gram -) with counterstain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Gram stain - bugs that don’t Gram stain well

A

Too thin to be visualized: Treponemia, Leptospira
Cell wall has high lipid content: Mycobacteria
No cell wall: Mycoplasma, Ureaplasma
Primarily intracellular: Legionella, Rickettsia, Chlamydia (also lacks classic peptidoglycan because of decreased muramic acid), Bartonella, Anaplasma, Ehrlichia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Giemsa stain

A

Chlamydia, Borrelia, Rickettsia, Trypanosomes, Plasmodium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Periodic acid-Schiff stain

A

Stains glycogen, mucopolysaccharides; used to diagnose Whipple disease (Tropheryma whipplei)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Ziehl-Neelsen stain (carbol-fuchsin)

A

Acid-fast bacteria (eg, Mycobacteria, Nocardia; stains mycolic acid acid in cell wall); protozoa (eg, Cryptosporidium oocysts)
Current standard of care is auramine-rhodamine stain for screening (inexpensive, more sensitive but less specific)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

India ink stain

A

Cryptococcus neoformans; mucicarmine can also be used to stain thick polysaccharide capsule red

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Silver stain

A

Fungi (eg, Coccidioides, Pneumocystis jirovecii), Legionella, Helicobacter pylori

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Fluorescent antibody stain

A

Used to identify many bacteria and viruses (example is FTA-ABS for syphillus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Properties of growth media

A

Selective or indicator (differential)

Note: the same type of media can possess both (or neither) of these properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Selective media

A

Favors the growth of a particular organism while preventing growth of other organisms, eg, Thayer-Martin agar contains antibiotics that allow the selective growth of Neisseria by inhibiting the growth of other sensitive organisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Indicator (differential) media

A

Yields a color change in response to the metabolism of certain organisms, eg, MacConkey agar contains a pH indicator; a lactose fermenter like E coli will convert lactose to acidic metabolites -> color change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Bugs with special culture requirements

A

H influenzae, N gonorrhoeae/meningitidis, B pertussis, C diphtheriae, M tuberculosis, M pneumoniae, lactose-fermenting enterics, E coli, Legionella, fungi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

H influenzae - Cx

A

Chocolate agar: factors V (NAD+) and X (hematin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

N gonorrhoeae/meningitidis - Cx

A

Thayer-Martin agar: selectively favors growth of Neisseria by inhibiting growth of gram + organisms with vancomycin, gram - organisms (except Neisseria) with trimethoprim and colistin, and fungi with nystatin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

B pertussis - Cx

A

Boret-Gengou agar: potato extract

Regan-Lowe medium: charcoal, blood and antibiotic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

C diphtheriae - Cx

A

Tellurite agar, Löeffler medium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

M tuberculosis - Cx

A

Löwenstein-Jensen agar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

M pneumoniae - Cx

A

Eaton agar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Lactose-fermenting enterics - Cx

A

MacConkey agar: fermentation produces acid, causing colonies to turn pink

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

E coli - Cx

A

Eosin-methylene blue (EMB) agar: colonies with green metallic sheen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

Legionella - Cx

A

Charcoal yeast extract agar buffered with cysteine and iron (BYCE)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Fungi - Cx

A

Sabouraud agar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Aerobes - energy generation

A

Use an O2-dependent system to generate ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Aerobes - examples

A

Nocardia, Pseudomonas aeruginosa, and Mycobacterium tuberculosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

Reactivation - M tuberculosis

A

Following immunocompromise or TNF-a inhibitor use (has a predilection for the apices of the lung)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

Anaerobes - characteristics

A

Lack catalase and/or superoxide dismutase (susceptible to oxidative damage)
Generally foul smelling (short chain fatty acids)
Difficult to culture
Produce gas in tissue (CO2 and H2)
Normal flora of the GI (pathogenic everywhere else)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

Anaerobes - examples

A

Clostridium, Bacteroides, Fusobacterium, and Actinomyces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Aminoglycosides vs Anaerobes

A

Ineffective, these antibiotics require O2 to enter into bacterial cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

Facultative anaerobes - energy generation

A

Use fermentation and other non oxygen-dependent pathways to generate ATP but are not killed by O2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

Facultative anaerobes - examples

A

Streptococci, staphylococci, and enteric gram + bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

Obligate intracellular - examples

A

Rickettsia, Chlamydia, Coxiella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

Obligate intracellular - characteristics

A

Rely on host ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

Facultative intracellular - examples

A

Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, Yersinia pestis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

Encapsulated bacteria - examples

A

Pseudomonas aeruginosa, Streptococcus pneumoniae, Haemophilus influenzae type B, Neisseria meningitidis, Escherichia coli, Salmonella, Klebsiella pneumoniae, group B strep

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

Encapsulated bacteria - capsules

A

Serve as an antiphagocytic virulence factor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

Encapsulated bacteria - vaccine antigen

A

Capsular polysaccharide + protein conjugate serves as an antigen in vaccines

71
Q

Encapsulated bacteria - immune response

A

Opsonized and then cleared by spleen

72
Q

Encapsulated bacteria - asplenic patients

A

Have decreased opsonizing ability and thus increased risk for severe infections by encapsulated bacteria
Give S pneumoniae, H influenzae, N meningitidis vaccines

73
Q

Encapsulated bacteria vaccines - characteristics

A
Some vaccines containing polysaccharide capsule antigen are conjugated to a carrier protein, enhancing immunogenicity by promoting T-cell activation and subsequent class switching
A polysaccharide antigen alone cannot be presented to T cells
74
Q

Encapsulated bacteria vaccines - examples

A
Pneumococcal vaccine: PCV13 (pneumococcal conjugate vaccine), PPSV23 (pneumococcal polysaccharide vaccine with no conjugated protein)
H influenzae type B (conjugate vaccine)
Meningococcal vaccine (conjugate vaccine)
75
Q

Urease-positive organisms - examples

A

Proteus, Cryptococcus, H pylori, Ureaplasma, Nocardia, Klebsiella, S epidermidis, S saprophyticus

76
Q

Urease-positive organisms - mechanism

A

Urease hydrolyzes urea to release ammonia and CO2 -> increasing pH

77
Q

Urease-positive organisms - complications

A

Predisposes to struvite (ammonium magnesium phosphate) stones, particularly Proteus

78
Q

Catalase-positive organisms - mechanism

A

Catalase degrades H2O2 into H2O and bubbles of O2 before it can be converted to microbicidal products by the enzyme myeloperoxidase

79
Q

Catalase-positive organisms - chronic granulomatous disease patients

A

CGD patients have a NADPH oxidase deficiency, and have recurrent infections with certain catalase + organisms

80
Q

Catalase-positive organisms - examples

A

Nocardia, Pseudomonas, Listeria, Aspergillus, Candida, E coli, Staphylococci, Serratia, B cepacia, H pylori

81
Q

Pigment-producing bacteria - examples

A

Actinomyces israelii, S aureus, P aeruginosa, Serratia marcesencs

82
Q

Actinomyces israelii - pigment

A

Yellow “sulfur” granules, which are composed of filaments of bacteria

83
Q

S aureus - pigment

A

Yellow/gold pigment

84
Q

P aeruginosa - pigment

A

Blue-green pigment (pyocyanin and pyoverdin)

85
Q

Serratia marcescens - pigment

A

Red pigment

86
Q

In vivo biofilm-producing bacteria - examples

A

S epidermidis, Viridans streptococci (S mutans, S sanguinis), P aeruginosa, nontypeable (unencapsulated) H influenzae

87
Q

S epidermidis biofilm - infection

A

Catheter and prosthetic devices

88
Q

Viridans streptococci biofilm - infection

A

Dental plaques, infective endocarditis

89
Q

P aeruginosa biofilm - infection

A

Respiratory tree colonization in patients with cystic fibrosis, ventilator-associated pneumonia, contact lens-associated keratitis

90
Q

Nontypeable (unencapsulated) H pylori biofilm - infection

A

Otitis media

91
Q

Bacterial virulence factors - function

A

Promote evasion of host immune response

92
Q

Bacterial virulence factors - examples

A

Protein A, IgA protease, M protein

93
Q

Protein A - mechanism

A

Binds Fc region of IgG
Prevents opsonization and phagocytosis
Expressed by S aureus

94
Q

IgA protease - mechanism

A

Enzyme that cleaves IgA, allowing bacteria to adhere and colonize mucous membranes
Secreted by S pneumoniae, H influenzae type B, and Neisseria

95
Q

M protein - mechanism

A

Helps prevent phagocytosis
Expressed by group A streptococci
Shares similar epitopes to human cellular proteins (molecular mimicry); possibly underlies the autoimmune response seen in acute rheumatic fever

96
Q

Type III secretion system

A

AKA “injectisome”
Needle-like protein appendage facilitating direct deliver of toxins from certain gram - bacteria (eg, Pseudomonas, Salmonella, Shigella, E coli) to eukaryotic host cell

97
Q

Bacterial genetics - transformation

A

Competent bacteria are able to bind and import short pieces of environmental naked bacterial chromosomal DNA (from bacterial cell lysis)
The transfer and expression of newly transferred genes is called transformation
Feature of many bacteria, especially S pneumoniae, H influenzae type B, and Neisseria
Any DNA can be used
Adding deoxyribonuclease to environment will degrade DNA in medium -> no transformation seen

98
Q

Bacterial genetics - F+ x F- conjugation

A

F+ plasmid contains genes required for sex pilus and conjugation
Bacteria without this plasmid are termed F-
Sex pilus on F+ bacterium contacts F- bacterium
A single strand of plasmid DNA is transferred across the conjugal “mating” bridge
No transfer of chromosomal DNA

99
Q

Bacterial genetics - Hfr x F- conjugation

A

F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high-frequency recombination (Hfr) cell
Transfer of leading part of plasmid and a few flanking chromosomal genes
High-frequency recombination may integrate some those bacterial genes
The recipient cell remains F- but now may have new bacterial genes

100
Q

Bacterial genetics - generalized transduction

A

A “packaging” event
Lytic phage infects bacterium, leading to cleavage of bacterial DNA
Parts of bacterial chromosomal DNA may become packaged in phage capsid
Phage infects another bacterium, transferring these genes

101
Q

Bacterial genetics - specialized transduction

A

An “excision” event
Lysogenic phage infects bacterium; viral DNA incorporates into bacterial chromosome
When phage DNA is excised, flanking bacterial genes may be excised with it
DNA is packaged into phage capsid and can infect another bacterium

102
Q

Bacterial genetics - specialized transduction lysogenic phage

A
Genes for the following 5 bacterial toxins are encoded in a lysogenic phage:
Group A strep erythrogenic toxin
Botulinum toxin
Cholera toxin
Diphtheria toxin
Shiga toxin
103
Q

Bacterial genetics - transposition

A

Segment of DNA (eg, transposon) that can “jump” (excision and reintegration) from one location to another, can transfer genes from plasmid to chromosome and vice versa.
When excision occurs, may include some flanking chromosomal DNA, which can be incorporated into a plasmid and transferred to another bacterium (ef, vanA gene from vancomycin-resistant Enterococcus to S aureus)

104
Q

Bacterial genetics - spore-forming bacteria

A

Some bacteria can form spores at the end of the stationary phase when nutrients are limited
Spores are highly resistant to heat and chemicals, have dipicolinic acid in their core, have no metabolic activity
Must autoclave to potentially kill spores (as done to surgical equipment) by steaming at 121 C for 15 minutes

105
Q

Spore-forming bacteria - examples

A

Bacillus anthracis (anthrax), Bacillus cereus (food poisoning), Clostridium botulinum (botulism), Clostridium difficile (pseudomembranous colitis), Clostridium perfrigens (gas gangrene), Clostridium tetani (tetanus)

106
Q

Exotoxins - source

A

Certain species of gram + and gram - bacteria

107
Q

Exotoxins - secreted from cell

A

Yes

108
Q

Exotoxins - chemistry

A

Polypeptide

109
Q

Exotoxins - location of genes

A

Plasmid or bacteriophage

110
Q

Exotoxins - adverse effects

A

High (fatal dose on the order of 1 microgram)

111
Q

Exotoxins - antigenicity

A

Induces high-titer antibodies called antitoxins

112
Q

Exotoxins - vaccines

A

Toxoids used as vaccines

113
Q

Exotoxins - heat stability

A

Destroyed rapidly at 60 C (except staphylococcal enterotoxin and E coli heat-stable toxin)

114
Q

Exotoxins - typical diseases

A

Tetanus, botulism, diphtheria

115
Q

Endotoxin - source

A

Outer cell membrane of most gram - bacteria

116
Q

Endotoxin - secreted from cell

A

No

117
Q

Endotoxin - chemistry

A

Lipid A component of LPS (structural part of bacteria; released when lysed)

118
Q

Endotoxin - location of genes

A

Bacterial chromosome

119
Q

Endotoxin - adverse effects

A

Low (fatal dose on the order of hundreds of micrograms)

120
Q

Endotoxin - clinical effects

A

Fever, shock (hypotension), DIC

121
Q

Endotoxin - mode of action

A

Induces TNF, IL-1, and IL-6

122
Q

Endotoxin - vaccines

A

No toxoids formed and no vaccine available

123
Q

Endotoxin - heat stability

A

Stable at 100 C for 1 hour

124
Q

Endotoxin - typical diseases

A

Meningococcemia; sepsis by gram - rods

125
Q

Exotoxin inhibiting protein synthesis - examples

A

Corynebacterium diphtheriae, Pseudomonas aeruginosa, Shigella spp, Enterohemorrhagic E coli (EHEC)

126
Q

Corynebacterium diphtheriae - toxin

A

Diphtheria toxin

127
Q

Diphtheria toxin - mechanism

A

Inactivate elongation factor (EF-2)

128
Q

Diphtheria toxin - manifestation

A

Pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)

129
Q

Pseudomonas aeruginosa - toxin

A

Exotoxin A

130
Q

Exotoxin A - mechanism

A

Inactivate elongation factor (EF-2)

131
Q

Exotoxin A - manifestation

A

Host cell death

132
Q

Shigella spp - toxin

A

Shiga toxin (ST)

133
Q

Shiga toxin - mechanism

A

Inactivate 60S ribosome by removing adenine from rRNA

134
Q

Shiga toxin - manifestation

A

GI mucosal damage -> dysentery; ST also enhances cytokine release, causing hemolytic-uremic syndrome (HUS)

135
Q

EHEC - toxin

A

Shiga-like toxin (SLT)

136
Q

Shiga-like toxin - mechanism

A

Inactivated 60S ribosome by removing adenine from rRNA

137
Q

Shiga-like toxin - manifestation

A

SLT enhances cytokine release, causing HUS (prototypically in EHEC serotype O157:H7)
Unlike Shigella, EHEC does not invade host cells

138
Q

Exotoxin increasing fluid secretion - examples

A

Enterotoxigenic E coli (ETEC), Bacillus anthracis, Vibrio cholerae

139
Q

ETEC - toxins

A

Heat-labile toxin (LT), heat-stable toxin (ST)

140
Q

Heat-labile toxin - mechanism

A

Overactivates adenylate cyclase (increasing cAMP) -> increasing Cl- secretion in gut and H2O efflux

141
Q

Heat-stable toxin - mechanism

A

Overactivates guanylate cyclase (increasing cGMP) -> decreasing resorption of NaCl and H2O in gut

142
Q

LT and ST - manifestation

A

Watery diarrhea

143
Q

Bacillus anthracis - toxin

A

Edema toxin

144
Q

Edema toxin - mechanism

A

Mimics the adenylate cyclase enzyme (increasing cAMP)

145
Q

Edema toxin - manifestation

A

Likely responsible for characteristic edematous borders of black eschar in cutaneous anthrax

146
Q

Vibrio cholerae - toxin

A

Cholera toxin

147
Q

Cholera toxin - mechanism

A

Overactivates adenylate cyclase (increasing cAMP) by permanently activating Gs -> increasing Cl- secretion in gut and H2O efflux

148
Q

Cholera toxin - manifestation

A

Voluminous “rice-water” diarrhea

149
Q

Exotoxin inhibiting phagocytic ability - example

A

Bordetella pertussis

150
Q

Bordetella pertussis - toxin

A

Pertussis toxin

151
Q

Pertussis toxin - mechanism

A

Overactivates adenylate cyclase (increasing cAMP) by disabling Gi, impairing phagocytosis to permit survival of microbe

152
Q

Pertussis toxin - manifestation

A

Whooping cough - child coughs on expiration and “whoops” on inspiration (toxin may not actually be a cause of cough; can cause “100-day cough” in adults)

153
Q

Exotoxins inhibiting release of neurotransmitter - examples

A

Clostridium tetani, Clostridium botulinum

154
Q

Clostridium tetani - toxin

A

Tetanospasmin

155
Q

Tetanospasmin and botulinum toxin - mechanism

A

Protease that cleaves SNARE (soluble NSF attachment protein receptor), a set of proteins required for neurotransmitter release via vesticular fusion

156
Q

Tetanospasmin - manifestation

A

Spastic paralysis, rises sardonic, and “lockjaw”; toxin prevents release of inhibitory (GABA and glycine) neurotransmitters from Renshaw cells in spinal cord

157
Q

Clostridium botulinum - toxin

A

Botulinum toxin

158
Q

Botulinum toxin - manifestation

A

Flaccid paralysis, floppy baby; toxin prevents release of stimulatory (ACh) signals at neurotransmitter junction

159
Q

AB toxin

A

Two component toxin (or three for anthrax) with B enabling binding and triggering uptake (endocytosis) of the active A component
The A components are usually ADP ribosyltransferases; others have enzymatic activities

160
Q

Exotoxins lysing cell membranes - examples

A

Clostridium perfringens, Streptococcus progenes

161
Q

Clostridium perfringens - toxin

A

Alpha toxin

162
Q

Alpha toxin - mechanism

A

Phospholipase (lecithinase) that degrades tissue and cell membranes

163
Q

Alpha toxin - manifestation

A

Degradation of phospholipids -> myonecrosis (“gas gangrene”) and hemolysis (“double zone” of hemolysis on blood agar)

164
Q

Streptococcus pyogenes - toxins

A

Streptolysin O and Exotoxin A

165
Q

Streptolysin O - mechanism

A

Protein that degrades cell membrane

166
Q

Streptolysin O - manifestation

A

Lyses RBCs; contributes to b-hemolysis; host antibodies against toxin (ASO) used to diagnose rheumatic fever (do not confuse with immune complexes of poststreptococcal glomerulonephritis)

167
Q

Exotoxins creating superantigens causing shock - examples

A

Staphylococcus aureus, Streptococcus pyogenes

168
Q

Staphylococcus aureus - toxin

A

Toxic shock syndrome toxin (TSST-1)

169
Q

TSST-1 and Exotoxin A - mechanism

A

Binds to MHCII and TCR outside of antigen binding site to cause overwhelming release of IL-1, IL-2, IFN-g, and TNF-a -> shock

170
Q

Endotoxin - characteristics

A

LPS found in outer membrane of gram - bacteria (both cocci and rods)
Composed of O antigen + core polysaccharide + lipid A (the toxic component)
Released upon cell lysis or by living cells by blebs detaching from outer surface membrane (vs exotoxin, which is actively secreted)

171
Q

Endotoxin - main effects

A

Macrophage activation (TLR4), complement activation, and tissue factor activation

172
Q

Endotoxin - macrophage activation (TLR4)

A

IL-1, IL-6 -> fever
TNF-a -> fever and hypotension
Nitric oxide -> hypotension

173
Q

Endotoxin - complement activation

A

C3a -> histamine release: hypotension and edema

C5a -> histamine release: hypotension and edema; neutrophil chemotaxis

174
Q

Endotoxin - tissues factor activation

A

Coagulation cascade -> DIC