Basic Bacteriology Flashcards
(174 cards)
1
Q
Bacterial appendages
A
Flagellum, pilus/fimbria
2
Q
Flagellum - chemical composition
A
Proteins
3
Q
Flagellum - function
A
Motility
4
Q
Pilus/fimbria - chemical composition
A
Glycoprotein
5
Q
Pilus/fimbria - function
A
Mediate adherence of bacteria to cell surface; sex plus forms during conjugations
6
Q
Bacterial specialized structures
A
Spore
7
Q
Spore - chemical composition
A
Keratin-like coat; dipicolinic acid; peptidoglycan, DNA
8
Q
Spore - function
A
Gram + only
Survival: resist dehydration, heat, chemicals
9
Q
Bacterial cell envelope components
A
Capsule, glycocalyx, outer membrane, periplasm, cell wall, cytoplasmic membrane
10
Q
Capsule - chemical composition
A
Organized, discrete polysaccharide layer (except poly-D-glutamate on B. anthracis)
11
Q
Capsule - function
A
Protects against phagocytosis
12
Q
Glycocalyx - chemical composition
A
Loose network of polysaccharides
13
Q
Glycocalyx - function
A
Mediated adherence to surfaces, especially foreign surfaces (eg, indwelling catheters)
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
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
16
Q
Periplasm - chemical composition
A
Space between cytoplasmic membrane and outer membrane in gram - bacteria (peptidoglycan in middle)
17
Q
Periplasm - function
A
Accumulates components exiting gram - cells, including hydrolytic enzymes (eg, b-lactamases)
18
Q
Cell wall - chemical composition
A
Peptidoglycan is a sugar backbone with peptide side chains cross-linked by transpeptidase
19
Q
Cell wall - function
A
Net-like structure gives right support, protects against osmotic pressure damage
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
21
Q
Cell wall components - unique to gram +
A
Lipoteichoic acid
22
Q
Cell wall components - common to both
A
Flagellum, pilus, capsule, cell wall, peptidoglycan, cytoplasm
23
Q
Cell wall components - unique to gram -
A
Outer membrane: endotoxin/LPS, porin
Periplasmic space: b-lactamase location
24
Q
Bacterial taxonomy - morphologies
A
Spherical (coccus), rod (bacillus), branching filamentous, pleomorphic (no cell wall), spiral (spirochetes)
25
Coccus - gram + examples
Staphylococcus (clusters), Streptococcus (chains or pairs), Enterococcus (pairs or short chains)
26
Coccus - gram - examples
Moraxella catarrhalis, Neisseria
27
Bacillus - gram + examples
Bacillus, Clostridium, Corynebacterium, Gardnerella (gram variable), Lactobacillus, Listeria, Mycobacterium (acid fast), Propionibacterium
28
Bacillus - gram - examples (enteric)
Bacteroides, Campylobacter, E coli, Enterobacter, Fusobacterium, Helicobacter, Klebsiella, Proteus, Pseudomonas, Salmonella, Serratia, Shigella, Vibrio, Yersinia
29
Bacillus - gram - examples (respiratory)
Bordetella, Burkholderia cepacia, Haemophilus (pleomorphic), Legionella (silver stain)
30
Bacillus - gram - examples (zoonotic)
Bartonella, Brucella, Francisella, Pasteurella
31
Branching filamentous - gram + examples
Actinomyces, Nocardia (weakly acid fast)
32
Pleomorphic - gram - examples
Anaplasma, Ehrlichia, Chlamydiae (Giemsa), Rickettsiae (Giemsa), Mycoplasma (contains sterols, which do not gram stain)
33
Spirochetes - gram - examples
Borrelia (Giemsa), Leptospira, Treponema
34
Stains
Gram, Giemsa, Periodic acid-Schiff, Ziehl-Neelsen (carbol fuchsin), India ink, silver, fluorescent antibody
35
Gram stain
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
36
Gram stain - bugs that don't Gram stain well
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
37
Giemsa stain
Chlamydia, Borrelia, Rickettsia, Trypanosomes, Plasmodium
38
Periodic acid-Schiff stain
Stains glycogen, mucopolysaccharides; used to diagnose Whipple disease (Tropheryma whipplei)
39
Ziehl-Neelsen stain (carbol-fuchsin)
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)
40
India ink stain
Cryptococcus neoformans; mucicarmine can also be used to stain thick polysaccharide capsule red
41
Silver stain
Fungi (eg, Coccidioides, Pneumocystis jirovecii), Legionella, Helicobacter pylori
42
Fluorescent antibody stain
Used to identify many bacteria and viruses (example is FTA-ABS for syphillus)
43
Properties of growth media
Selective or indicator (differential)
| Note: the same type of media can possess both (or neither) of these properties
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Selective media
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
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Indicator (differential) media
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
46
Bugs with special culture requirements
H influenzae, N gonorrhoeae/meningitidis, B pertussis, C diphtheriae, M tuberculosis, M pneumoniae, lactose-fermenting enterics, E coli, Legionella, fungi
47
H influenzae - Cx
Chocolate agar: factors V (NAD+) and X (hematin)
48
N gonorrhoeae/meningitidis - Cx
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
49
B pertussis - Cx
Boret-Gengou agar: potato extract
| Regan-Lowe medium: charcoal, blood and antibiotic
50
C diphtheriae - Cx
Tellurite agar, Löeffler medium
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M tuberculosis - Cx
Löwenstein-Jensen agar
52
M pneumoniae - Cx
Eaton agar
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Lactose-fermenting enterics - Cx
MacConkey agar: fermentation produces acid, causing colonies to turn pink
54
E coli - Cx
Eosin-methylene blue (EMB) agar: colonies with green metallic sheen
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Legionella - Cx
Charcoal yeast extract agar buffered with cysteine and iron (BYCE)
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Fungi - Cx
Sabouraud agar
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Aerobes - energy generation
Use an O2-dependent system to generate ATP
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Aerobes - examples
Nocardia, Pseudomonas aeruginosa, and Mycobacterium tuberculosis
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Reactivation - M tuberculosis
Following immunocompromise or TNF-a inhibitor use (has a predilection for the apices of the lung)
60
Anaerobes - characteristics
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)
61
Anaerobes - examples
Clostridium, Bacteroides, Fusobacterium, and Actinomyces
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Aminoglycosides vs Anaerobes
Ineffective, these antibiotics require O2 to enter into bacterial cells
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Facultative anaerobes - energy generation
Use fermentation and other non oxygen-dependent pathways to generate ATP but are not killed by O2
64
Facultative anaerobes - examples
Streptococci, staphylococci, and enteric gram + bacteria
65
Obligate intracellular - examples
Rickettsia, Chlamydia, Coxiella
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Obligate intracellular - characteristics
Rely on host ATP
67
Facultative intracellular - examples
Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, Yersinia pestis
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Encapsulated bacteria - examples
Pseudomonas aeruginosa, Streptococcus pneumoniae, Haemophilus influenzae type B, Neisseria meningitidis, Escherichia coli, Salmonella, Klebsiella pneumoniae, group B strep
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Encapsulated bacteria - capsules
Serve as an antiphagocytic virulence factor
70
Encapsulated bacteria - vaccine antigen
Capsular polysaccharide + protein conjugate serves as an antigen in vaccines
71
Encapsulated bacteria - immune response
Opsonized and then cleared by spleen
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Encapsulated bacteria - asplenic patients
Have decreased opsonizing ability and thus increased risk for severe infections by encapsulated bacteria
Give S pneumoniae, H influenzae, N meningitidis vaccines
73
Encapsulated bacteria vaccines - characteristics
```
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
Encapsulated bacteria vaccines - examples
```
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
Urease-positive organisms - examples
Proteus, Cryptococcus, H pylori, Ureaplasma, Nocardia, Klebsiella, S epidermidis, S saprophyticus
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Urease-positive organisms - mechanism
Urease hydrolyzes urea to release ammonia and CO2 -> increasing pH
77
Urease-positive organisms - complications
Predisposes to struvite (ammonium magnesium phosphate) stones, particularly Proteus
78
Catalase-positive organisms - mechanism
Catalase degrades H2O2 into H2O and bubbles of O2 before it can be converted to microbicidal products by the enzyme myeloperoxidase
79
Catalase-positive organisms - chronic granulomatous disease patients
CGD patients have a NADPH oxidase deficiency, and have recurrent infections with certain catalase + organisms
80
Catalase-positive organisms - examples
Nocardia, Pseudomonas, Listeria, Aspergillus, Candida, E coli, Staphylococci, Serratia, B cepacia, H pylori
81
Pigment-producing bacteria - examples
Actinomyces israelii, S aureus, P aeruginosa, Serratia marcesencs
82
Actinomyces israelii - pigment
Yellow "sulfur" granules, which are composed of filaments of bacteria
83
S aureus - pigment
Yellow/gold pigment
84
P aeruginosa - pigment
Blue-green pigment (pyocyanin and pyoverdin)
85
Serratia marcescens - pigment
Red pigment
86
In vivo biofilm-producing bacteria - examples
S epidermidis, Viridans streptococci (S mutans, S sanguinis), P aeruginosa, nontypeable (unencapsulated) H influenzae
87
S epidermidis biofilm - infection
Catheter and prosthetic devices
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Viridans streptococci biofilm - infection
Dental plaques, infective endocarditis
89
P aeruginosa biofilm - infection
Respiratory tree colonization in patients with cystic fibrosis, ventilator-associated pneumonia, contact lens-associated keratitis
90
Nontypeable (unencapsulated) H pylori biofilm - infection
Otitis media
91
Bacterial virulence factors - function
Promote evasion of host immune response
92
Bacterial virulence factors - examples
Protein A, IgA protease, M protein
93
Protein A - mechanism
Binds Fc region of IgG
Prevents opsonization and phagocytosis
Expressed by S aureus
94
IgA protease - mechanism
Enzyme that cleaves IgA, allowing bacteria to adhere and colonize mucous membranes
Secreted by S pneumoniae, H influenzae type B, and Neisseria
95
M protein - mechanism
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
Type III secretion system
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
Bacterial genetics - transformation
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
Bacterial genetics - F+ x F- conjugation
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
Bacterial genetics - Hfr x F- conjugation
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
Bacterial genetics - generalized transduction
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
Bacterial genetics - specialized transduction
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
Bacterial genetics - specialized transduction lysogenic phage
```
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
Bacterial genetics - transposition
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
Bacterial genetics - spore-forming bacteria
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
Spore-forming bacteria - examples
Bacillus anthracis (anthrax), Bacillus cereus (food poisoning), Clostridium botulinum (botulism), Clostridium difficile (pseudomembranous colitis), Clostridium perfrigens (gas gangrene), Clostridium tetani (tetanus)
106
Exotoxins - source
Certain species of gram + and gram - bacteria
107
Exotoxins - secreted from cell
Yes
108
Exotoxins - chemistry
Polypeptide
109
Exotoxins - location of genes
Plasmid or bacteriophage
110
Exotoxins - adverse effects
High (fatal dose on the order of 1 microgram)
111
Exotoxins - antigenicity
Induces high-titer antibodies called antitoxins
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Exotoxins - vaccines
Toxoids used as vaccines
113
Exotoxins - heat stability
Destroyed rapidly at 60 C (except staphylococcal enterotoxin and E coli heat-stable toxin)
114
Exotoxins - typical diseases
Tetanus, botulism, diphtheria
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Endotoxin - source
Outer cell membrane of most gram - bacteria
116
Endotoxin - secreted from cell
No
117
Endotoxin - chemistry
Lipid A component of LPS (structural part of bacteria; released when lysed)
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Endotoxin - location of genes
Bacterial chromosome
119
Endotoxin - adverse effects
Low (fatal dose on the order of hundreds of micrograms)
120
Endotoxin - clinical effects
Fever, shock (hypotension), DIC
121
Endotoxin - mode of action
Induces TNF, IL-1, and IL-6
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Endotoxin - vaccines
No toxoids formed and no vaccine available
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Endotoxin - heat stability
Stable at 100 C for 1 hour
124
Endotoxin - typical diseases
Meningococcemia; sepsis by gram - rods
125
Exotoxin inhibiting protein synthesis - examples
Corynebacterium diphtheriae, Pseudomonas aeruginosa, Shigella spp, Enterohemorrhagic E coli (EHEC)
126
Corynebacterium diphtheriae - toxin
Diphtheria toxin
127
Diphtheria toxin - mechanism
Inactivate elongation factor (EF-2)
128
Diphtheria toxin - manifestation
Pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)
129
Pseudomonas aeruginosa - toxin
Exotoxin A
130
Exotoxin A - mechanism
Inactivate elongation factor (EF-2)
131
Exotoxin A - manifestation
Host cell death
132
Shigella spp - toxin
Shiga toxin (ST)
133
Shiga toxin - mechanism
Inactivate 60S ribosome by removing adenine from rRNA
134
Shiga toxin - manifestation
GI mucosal damage -> dysentery; ST also enhances cytokine release, causing hemolytic-uremic syndrome (HUS)
135
EHEC - toxin
Shiga-like toxin (SLT)
136
Shiga-like toxin - mechanism
Inactivated 60S ribosome by removing adenine from rRNA
137
Shiga-like toxin - manifestation
SLT enhances cytokine release, causing HUS (prototypically in EHEC serotype O157:H7)
Unlike Shigella, EHEC does not invade host cells
138
Exotoxin increasing fluid secretion - examples
Enterotoxigenic E coli (ETEC), Bacillus anthracis, Vibrio cholerae
139
ETEC - toxins
Heat-labile toxin (LT), heat-stable toxin (ST)
140
Heat-labile toxin - mechanism
Overactivates adenylate cyclase (increasing cAMP) -> increasing Cl- secretion in gut and H2O efflux
141
Heat-stable toxin - mechanism
Overactivates guanylate cyclase (increasing cGMP) -> decreasing resorption of NaCl and H2O in gut
142
LT and ST - manifestation
Watery diarrhea
143
Bacillus anthracis - toxin
Edema toxin
144
Edema toxin - mechanism
Mimics the adenylate cyclase enzyme (increasing cAMP)
145
Edema toxin - manifestation
Likely responsible for characteristic edematous borders of black eschar in cutaneous anthrax
146
Vibrio cholerae - toxin
Cholera toxin
147
Cholera toxin - mechanism
Overactivates adenylate cyclase (increasing cAMP) by permanently activating Gs -> increasing Cl- secretion in gut and H2O efflux
148
Cholera toxin - manifestation
Voluminous "rice-water" diarrhea
149
Exotoxin inhibiting phagocytic ability - example
Bordetella pertussis
150
Bordetella pertussis - toxin
Pertussis toxin
151
Pertussis toxin - mechanism
Overactivates adenylate cyclase (increasing cAMP) by disabling Gi, impairing phagocytosis to permit survival of microbe
152
Pertussis toxin - manifestation
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
Exotoxins inhibiting release of neurotransmitter - examples
Clostridium tetani, Clostridium botulinum
154
Clostridium tetani - toxin
Tetanospasmin
155
Tetanospasmin and botulinum toxin - mechanism
Protease that cleaves SNARE (soluble NSF attachment protein receptor), a set of proteins required for neurotransmitter release via vesticular fusion
156
Tetanospasmin - manifestation
Spastic paralysis, rises sardonic, and "lockjaw"; toxin prevents release of inhibitory (GABA and glycine) neurotransmitters from Renshaw cells in spinal cord
157
Clostridium botulinum - toxin
Botulinum toxin
158
Botulinum toxin - manifestation
Flaccid paralysis, floppy baby; toxin prevents release of stimulatory (ACh) signals at neurotransmitter junction
159
AB toxin
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
Exotoxins lysing cell membranes - examples
Clostridium perfringens, Streptococcus progenes
161
Clostridium perfringens - toxin
Alpha toxin
162
Alpha toxin - mechanism
Phospholipase (lecithinase) that degrades tissue and cell membranes
163
Alpha toxin - manifestation
Degradation of phospholipids -> myonecrosis ("gas gangrene") and hemolysis ("double zone" of hemolysis on blood agar)
164
Streptococcus pyogenes - toxins
Streptolysin O and Exotoxin A
165
Streptolysin O - mechanism
Protein that degrades cell membrane
166
Streptolysin O - manifestation
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
Exotoxins creating superantigens causing shock - examples
Staphylococcus aureus, Streptococcus pyogenes
168
Staphylococcus aureus - toxin
Toxic shock syndrome toxin (TSST-1)
169
TSST-1 and Exotoxin A - mechanism
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
Endotoxin - characteristics
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
Endotoxin - main effects
Macrophage activation (TLR4), complement activation, and tissue factor activation
172
Endotoxin - macrophage activation (TLR4)
IL-1, IL-6 -> fever
TNF-a -> fever and hypotension
Nitric oxide -> hypotension
173
Endotoxin - complement activation
C3a -> histamine release: hypotension and edema
| C5a -> histamine release: hypotension and edema; neutrophil chemotaxis
174
Endotoxin - tissues factor activation
Coagulation cascade -> DIC
