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USMLE1 - Microbiology > 1. Basic Structures and Staining > Flashcards

1. Basic Structures and Staining Flashcards

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1
Q

Bacterial Structures: Peptidoglycan. Function and Chemical compositions

A

Gives rigid support, protects against osmotic pressure; Sugar backbone w/ cross-linked peptide side chains.

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2
Q

Bacterial Structures: Cell wall / cell membrane (G+’s). Function and Chemical compositions

A

Major surface Ag; Peptidoglycan for support. Lipoteichoic acid induces TNF and IL-1.

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3
Q

Bacterial Structures: Outer membrane (G-). Function and Chemical compositions

A

Site of endotoxin (Lipopolysaccharide, LPS), major surface Ag; Lipid A induces TNF and IL-1 Polysaccharide is the Ag

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4
Q

Bacterial Structures: Plasma membrane. Function and Chemical compositions

A

Site of oxidative and transport enzymes; Lipoprotein bilayer

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5
Q

Bacterial Structures: Ribosome. Function and Chemical compositions.

A

Protein synthesis; 50S and 30S subunits

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6
Q

Bacterial Structures: Periplasm. Function and Chemical compositions

A

Space btw the cytoplasmic membrane and the peptidoglycan wall in G- bacteria; Contains many hydrolytic enzymes, including beta-lactamases

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7
Q

Bacterial Structures: Capsule Function and Chemical compositions (except which bacteria?)

A

Protects against phagocytosis; Polysaccharide (except in Bacillus anthracis , which contains D-glutamate)

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8
Q

Bacterial Structures: Pilus/fimbria. Function and Chemical compositions.

A

Mediate adherence of bacteria to cell surface, sex pilus forms attachment btw 2 bacteria during conjugation; Glycoprotein

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9
Q

Bacterial Structures: Flagellum. Function and Chemical compositions

A

Motility; Protein

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10
Q

Bacterial Structures: Spore. Function and Chemical compositions

A

Provides resistance to dehydration, heat, and chemicals; Keratin-like coat, dipiclonic acid

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11
Q

Bacterial Structures: Plasmid. Function and Chemical compositions

A

Contains a variety of genes for antibiotic resistance, enzymes, toxins; DNA

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12
Q

Bacterial Structures: Glycocalyx. Function and Chemical compositions

A

Mediates adherence to surfaces, especially foreign surfaces (e.g. indwelling catheters); Polysaccharide

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13
Q

Structures unique to gram (+) organisms

A

Teichoic acid Cell wall

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14
Q

Structures common to Gram +/- organisms

A

Flagellum, pilus, capsule, PDG, cytoplasmic membrane

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15
Q

Features unique to G(-) organisms

A

Endotoxin/LPS (outer membrane) Periplasmic space (location of many beta-lactamases)

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16
Q

What are the bacteria w/ unusual cell membranes/walls (2)?

A

Mycoplasma: contain sterols and have no cell wall , G+ rod

Mycobacteria: Contain mycolic acid. High lipid content.

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17
Q

Name the G(+) cocci (2)

A

Staphylococcus Streptococcus

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18
Q

Name the G(-) cocci (1)

A

Neisseria

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19
Q

Name the G(+) Rods (5)

A

My cobacterium (acid-fast) List eria B acillus C lostridium C orynebacterium

What happened when you were sending that email to Gram + Rod ? My List B ecame CC ‘d

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20
Q

Bacterial taxonomy of: Mycobacterium (acid fast), Listeria, Bacillus, Cornybacterium, Clostridium

A

G(+) Rods

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21
Q

Name the G(-) Rods (9)

A

H ave Y ou E ver L istened to GNR (Guns n’ Roses = Gram (-) Rods)? I P refer F un G reat B ig B oy B ands.

Haemophilus Yersinia Enterics (separate card) Legionella (silver stain) Bordatella Brucella Bartonella Francisella Pasteurella Gardnerella (gram variable)

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22
Q

Bacteria taxonomy of: Haemophilus, Yersinia, Enterics, Legionella, Pasteurella, Francisella, Gardnerella (gram variable), Bordetella, Brucella, Bardetella

A

G(-) Rods

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23
Q

Name the G+ Branching Filamentous bacteria (2)

A

Actinomyces Nocardia (weakly acid-fast)

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24
Q

Bacteria taxonomy: Actinomyces, Nocardia (weakly acid-fast)

A

Branching Filamentous bacteria (G+)

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25
Q

Name the Pleomorphic (G-) bacteria (2)

A

Rickettsiae
Chlamydiae (Giemsa stain)

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26
Q

Bacteria taxonomy: Rickettsiae, Chlamydiae (Giemsa stain)

A

Pleomorphic (G-) bacteria

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27
Q

Name the Spirochetes (G-) (3)

A

Leptospira Borrelia (Giemsa stain) Treponema

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28
Q

Bacterial taxonomy: Leptospira, Borrelia (Giemsa stain), Treponema

A

Spirochetes (G-)

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29
Q

Neither G+ nor G- (b/c no cell wall)

A

Mycoplasma

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30
Q

Bugs that won’t Gram stain (6)

A

These Rascals May Microscopically Lack Color Treponema (too thin to be visualized) Rickettsia (intracellular parasite) Mycobacteria (high-lipid-content cell wall requires acid-fast stain) Mycoplasma (no cell wall) Legionella pneumophilia (primarily intracellular) Chlamydia (intracellular parasite; lacks muramic acid cell wall)

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31
Q

Visualizing Treponemes

A

Darkfield microscopy and fluorescent Ab staining

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32
Q

Visualizing Mycobacteria

A

Acid-fast stain

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33
Q

Visualizing Legionella

A

Silver stain

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34
Q

Giemsa’s stain is used to visualize…?

A

use for: Borrelia Plasmodium Trypanosomes Chlamydia

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35
Q

PAS (periodic acid-Schiff) stain

A

stains glycogen, mucopolysaccharides*; Used to diagnose Whipple’s dz, Tropheryma whippelii (*PASs the sugar)

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36
Q

Ziehl-Neelsen stain (carbol fuchsin)

A

Use to stain Acid-fast bacteria

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37
Q

India ink

A

used to visualize Cryptococcus neoformans

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38
Q

Silver stain

A

used to visualize: fungi (e.g. pneumocystics), Legionella

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39
Q

Media/Special culture requirements for: H. influenzae

A

Chocolate agar w/ factors V (NAD) and X (hematin) (Media used for isolation)

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40
Q

Chocolate agar w/ factors V (NAD) and X (hematin)

A

H. influenzae

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41
Q

Media/Special culture requirements for: N. gonorrheae

A

Thayer-Martin media (or VPN)
Vancomycin (inh. G+), Polymyxin (inh G-), Nystatin (inh. fungi); “to connect to Neiserria, please use your vpN client”

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42
Q

Thayer-Martin media (VPN Vancomycin-Polymyxin-Nystatin)

A

N. gonorrheae

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43
Q

Media/Special culture requirements for: B. pertussis

A

Bordet-Gengou (potato) agar (Bordet for Bordetella)

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44
Q

Bordet-Gengou (potato) agar

A

B. pertussis

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45
Q

Media/Special culture requirements for: C. diphtheriae

A

Tellurite plate, Loffler’s media (don’t Laugh and double Dip and Tell)

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46
Q

Tellurite plate, Loffler’s media

A

C. diphtheriae

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47
Q

Media/Special culture requirements for: M. tuberculosis

A

Lowenstein-Jensen agar (Media used for isolation)

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48
Q

Lowenstein-Jensen agar

A

M. tuberculosis

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49
Q

Media/Special culture requirements for: M. pneumoniae

A

Eaton’s agar (Media used for isolation)

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50
Q

Eaton’s agar

A

M. pneumoniae

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51
Q

Media/Special culture requirements for: E. coli

A

Eosin-methylene Blue (EMB) agar (green colonies w/ metallic sheen) (Media used for isolation)

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52
Q

Eosin-methylene Blue (EMB) agar (green colonies w/ metallic sheen)

A

E. coli

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53
Q

Media/Special culture requirements for: Lactose-fermenting enterics

A

Pink colonies on MacConkey’s agar; fermentation produces acid, turning plate pink (Media used for isolation)

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54
Q

Pink colonies on MacConkey’s agar

A

Lactose-fermenting enterics

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55
Q

Media/Special culture requirements for: Legionella

A

Charcoal yeast extract agar buffered w/ increased iron and cysteine (Media used for isolation)

56
Q

Charcoal yeast extract agar buffered w/ increased iron and cysteine

A

Legionella

57
Q

Media/Special culture requirements for: Fungi

A

Sabouraud’s agar (Media used for isolation)

58
Q

Sabouraud’s agar

A

Fungi

59
Q

G(-) Enterics (rod-shaped) (13)

A

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

60
Q

Obligate aerobes

A

Use an O2-dependent system to generate ATP Examples: (Nagging Pests Must Breathe) Nocardia Pseudomonas Mycobacterium tuberculosis (w/ prediliction for apices of lungs, where PO2 is highest) Bacillus Also: to help remember Pseudomonas aeruginosa - AERuginosa is an AERobe

61
Q

Pseudomonas aeruginosa O2 tolerance? Where does it show up?

A

P. AERuginosa is an AERobe seen in burn wounds, nosocomial pneumonia, and pneumonias in cystic fibrosis pts.

62
Q

Obligate Anaerobes

A

Lack catalase and/or superoxide dismutase, and thus are susceptible to oxidative damage. Generally foul-smelling (short-chain FA’s), are difficult to culture, and produce gas in tissue (CO2 and H2). Normal flora in GI tract, pathogenic elsewhere. Examples: AminO2 glycosides are ineffective against anaerobes because the antibiotics require O2 to enter bacterial cell. (anaerobes Can’t Breathe Air) Clostridium Bacteroides Actinomyces

63
Q

Aminoglycosides and anaerobes

A

AminO2 glycosides are ineffective against anaerobes b/c these ABX require O2 to enter into the bacterial cell.

64
Q

Obligate intracellular bugs

A

Rickettsia, Chlamydia (Stay inside [cells] when it’s R eally C old) *Can’t make their own ATP

65
Q

Facultatively intracellular bugs (8)

A

Some Nasty Bugs May Live FacultativeLY Salmonella Neisseria Brucella Mycobacterium Listeria Francisella Legionella Yersinia

66
Q

Quellung Reaction

A

Postive quellung: If encapsulated bug is present, the capsule swells when specific anti-capsular antisera are added (Quellung = capsular swellung)

67
Q

Capsule and vaccines

A

Capsule is Ag for vaccines (e.g. Pneumovax, H. influenzae B, meningococcal vaccines) Conjugation w/ protein increases immunogenicity and T-cell dependent response

68
Q

Quellung (+) Bacteria

A 
SHiN SKiS (Strep pneumo, H Influenzae type B, Neisseria, Salmonella, Klebsiella, group B Strep)
 Polysaccharide capsule is an antiphagocytic virulence factor for above bacteria. Asplenic individuals have decreased ability to opsonize encapsulated pathogens so are at risk of severe infections (give s. pneumo, h. influenza and N. mening vaccines)
69
Q

Urease (+) bugs

A

Proteus, Ureaplasma, Nocardia, Cryptococcus, H.pylori, Klebsiella
“PUNCH the Kid who pee on you”

70
Q

Pigment-producing bacteria (hint: what is yellow (2)? red? blue-green?)

A

Actinomyces israelii - yellow “sulfur” granules, composed of mass of filaments and formed in pus (Israel has yellow sand)
S. aureus (gold) - yellow pigment
Pseudomonas aeruginosa - blue-green (arugula is green)
Serratia marcescens - red (Mars is red)

71
Q

Virulence factors

A

Promote evasion of host immune response

72
Q

Important virulence factors in S. aureus

A

protein A: Binds Fc region of Ig, disrupts opsonization and phagocytosis.

73
Q

Who makes Protein A? What is it for?

A

S. aureus. Virulence factor that binds Fc region of Ig to prevent opsonization and phagocytosis.

74
Q

Who secretes IgA protease and what is it for?

A

S. pneumo, H. influenzae type B, Neisseria (same capsulated SHiN); virulence factor to colonize respiratory mucosa (mucosal immunity)

75
Q

Important virulence factor for SHiN group (S. pneumoniae, H.influenzae type B, Neisseria)

A

IgA protease. Enzyme that cleaves IgA to colonize respiratory mucosa.

76
Q

Group A streptococcus virulence factors

A

M protein: Helps prevent phagocytosis

(A.M. A for Staph aureus and M. for Group A Strep)

77
Q

Who has M protein and what is it for?

A

Group A streptococcus virulence factors; helps prevent phagocytosis

78
Q

Exotoxin vs. Endotoxin: Source

A

Certain species of some G(+) and G(-) organisms; Outer cell membrane of most G(-) bacteria and Listeria

79
Q

Exotoxin vs. Endotoxin: Is it ecreted from cell?

A

Exotoxin is secreted from cell. Endotoxin is not.

80
Q

Exotoxin vs. Endotoxin: Chemistry

A

Polypeptide; Lipopolysaccharide (structural part of the bacteria. Released when lysed)

81
Q

Exotoxin vs. Endotoxin: Location of genes

A

Plasmid or bacteriophage; bacterial chromosome (Exo ; Endo)

82
Q

Exotoxin vs. Endotoxin: Toxicity

A

High (fatal dose on the order of 1 microgram); Low (fatal dose on the order of hundreds of micrograms) (Exo ; Endo)

83
Q

Exotoxin vs. Endotoxin: Clinical effects

A

Various; Fever, shock (Exo ; Endo)

84
Q

Exotoxin vs. Endotoxin: Mode of action

A

Various; Includes TNF and IL-1 (Exo ; Endo)

85
Q

Exotoxin vs. Endotoxin: Antigenicity

A

Induces high-titer Abs called antitoxins ; Poorly antigenic (Exo ; Endo)

86
Q

Exotoxin vs. Endotoxin: Vaccines

A

Toxoids useful as vaccines; No toxoids formed and no vaccine available (Exo ; Endo)

87
Q

Exotoxin vs. Endotoxin: Heat stability

A

Destroyed rapidly at 60C (except staphylococcal enterotoxin); Stable at 100C for 1 hour (Exo ; Endo)

88
Q

Exotoxin vs. Endotoxin: Typical diseases

A

Tetanus, botulism, diphtheria; Meningococcemia, sepsis by G(-) rods (Exo ; Endo)

89
Q

Superantigens

A

Bind directly to MHCII and T-cell receptor simultaneously, activating large numbers of T-cells to stimulate release of IFN-gamma and IL-2

90
Q

Toxins: TSST-1

A

Organism, toxin function: S. aureus SuperAg that causes toxic shock syndrome (fever, rash, shock).

91
Q

S. aureus SuperAg that causes toxic shock syndrome (fever, rash, shock).

A

TSST-1

92
Q

Toxins: Exfoliatin

A

Organism, toxin function: S. aureus Causes staphylococcal scalded skin syndrome

93
Q

S. aureus Causes staphylococcal scalded skin syndrome

A

Exfoliatin

94
Q

Toxins: Enterotoxins

A

Organism, toxin function: S. aureus (and others) Cause food poisoning

95
Q

S. aureus (and others) Cause food poisoning

A

Enterotoxins

96
Q

Toxins: Scarlet fever-erythrogenic toxin

A

Organism, toxin function: S. pyogenes SuperAg that causes toxic shock-like syndrome

97
Q

S. pyogenes SuperAg that causes toxic shock-like syndrome

A

Scarlet fever-erythrogenic toxin

98
Q

ADP ribosylating exotoxins

A

Interfere w/ host cell function. B (binding) component binds to a receptor on the surface of the host cell, enabling endocytosis. A (active) component then attaches an ADP-ribosyl to a host cell protein (ADP ribosylation), altering protein function.

99
Q

Toxins: Diphtheria exotoxin

A

Organism, toxin function: Corynebacterium diphtheriae ADP-ribosylating A-B exotoxin that inactivates EF-2 (similar to Psudomonas exotoxin A) Causes pharyngitis and pseudomembrane in throat.

100
Q

Corynebacterium diphtheriae ADP-ribosylating A-B exotoxin that inactivates EF-2 (similar to Psudomonas exotoxin A) Causes pharyngitis and pseudomembrane in throat.

A

Diphtheria exotoxin

101
Q

Toxins: Cholera toxin

A

Organism, toxin function: Vibrio Cholerae ADP ribosylation of G-protein stimulates adenylyl cyclase Increased pumping of Cl- into gut and decreased Na+ absorption Water moves into gut lumen Causes voluminous rice-water diarrhea

102
Q

Vibrio Cholerae ADP ribosylation of G-protein stimulates adenylyl cyclase Increased pumping of Cl- into gut and decreased Na+ absorption Water moves into gut lumen Causes voluminous rice-water diarrhea

A

Cholera toxin

103
Q

Toxins: Heat-labile toxin, Heat-stabile toxin

A

Organism, toxin function: E. coli ADP-ribosylating A-B toxins Heat-labile: stimulates Adenylyl cyclase Heat-stabile: stimulates Guanylate cyclase Both: cause watery diarrhea Labile like the A ir, Stable like the G round

104
Q

Toxins: Pertussis toxin (PT)

A

Organism, toxin function: Bordetella pertussis ADP-ribosylating A-B toxin that increases cAMP by inhibiting G-alpha1 Causes whooping cough Inhibits chemokine receptor –> causes lymphocytosis

105
Q

Toxins: alpha toxin

A

Organism, toxin function: Clostridium perfringens Causes gas gangrene Get double zone of hemolysis on blood agar

106
Q

Clostridium perfringens Causes gas gangrene Get double zone of hemolysis on blood agar

A

alpha toxin

107
Q

Toxins: Tetanus toxin (tetanospasmin)

A

Organism, toxin function: C. tetani Blocks the release of inhibitory neurotransmitters GABA and glycine Causes lockjaw

108
Q

C. tetani Blocks the release of inhibitory neurotransmitters GABA and glycine Causes lockjaw

A

Tetanus toxin (tetanospasmin)

109
Q

Toxins: Botulinum toxin (aka Botox)

A

Organism, toxin function: C. botulinum Blocks release of ACh Causes anticholinergic symptoms, CNS paralysis (especially cranial nerves) Spores found in canned food, honey (causes floppy baby)

110
Q

C. botulinum Blocks release of ACh Causes anticholinergic symptoms, CNS paralysis (especially cranial nerves) Spores found in canned food, honey (causes floppy baby)

A

Botulinum toxin (aka Botox)

111
Q

Toxins: Anthrax toxin

A

Organism, toxin function: Bacillus anthracis Edema factor, part of the toxin complex, is an adenylate cyclase

112
Q

Toxins: Shiga toxin

A

Organism, toxin function: Shigella, and E. coli O157:H7 Cleaves host cell rRNA (inactivates 60S ribosome) Enhances cytokine release, causing HUS

113
Q

Shigella, and E. coli O157:H7 Cleaves host cell rRNA (inactivates 60S ribosome) Enhances cytokine release, causing HUS

A

Shiga toxin

114
Q

Toxins: Streptolysin O

A

Organism, toxin function: S. pyogenes a hemolysin. Ag for ASO Ab, which is used in Dx of rheumatic fever

115
Q

S. pyogenes a hemolysin. Ag for ASO Ab, which is used in Dx of rheumatic fever

A

Streptolysin O

116
Q

cAMP inducers (list)

A

Vibrio cholerae B. pertussis E. coli Bacillus anthracis* *Cholera, pertussis, and E. coli toxins act via ADP ribosylation to permanently activate endogenous adenylate cyclase (increasing cAMP), While anthrax edema factor is itself an adenylate cyclase

117
Q

Vibrio Cholerae toxin and cAMP

A

Toxin permanently activates Gs, Causing rice-water diarrhea (Cholera turns the on on)

118
Q

B. pertussis and cAMP

A

Pertussis toxin permanently disables Gi, causing whooping cough (Pertussis toxin turns the off off) *Pertussis toxin also promotes lymphocytosis by inhibiting chemokine receptors.

119
Q

E. coli and cAMP

A

Heat-labile toxin stimulates adenylyl cyclase

120
Q

Bacillus anthracis and cAMP

A

Anthrax toxin includes edema factor, a bacterial adenylate cyclase (increases cAMP)

121
Q

Endotoxin

A

A Lipopolysaccharide found in the cell wall of G(-) bacteria N-dotoxin is an integral part of the gram-Negative cell wall *Endotoxin is heat stable

122
Q

Endotoxin and Macrophages

A

Activates Macs: IL-1 causes fever TNF causes fever, hemorrhagic tissue necrosis NO causes hypotension (shock)

123
Q

Endotoxin and complement

A

Activates the complement (alternative pathway): C3a causes hypotension, edema C5a causes PMN chemotaxis

124
Q

Endotoxin and Hageman factor (factor XII)

A

Activates Hageman factor This activates coagulation cascade, causing DIC

125
Q

Bacterial growth curve

A

Lag phase: metabolic activity w/o division Log phase: rapid cell division Stationary phase: nutrient depletion slows growth. Spore formation in some bacteria. Death phase: prolonged nutrient depletion and buildup of waste products leads to death.

126
Q

Transformation

A

DNA taken up directly from environment by competent prokaryotic and eukaryotic cells. Any DNA can be used

127
Q

F+ x F- Conjugation

A

F+ plasmid contains genes for conjugation process. Bacteria w/o this are termed F-. Plasmid is replicated and transferred through pilus from the F+ cell. Plasmid DNA only, no transfer of chromosomal genes.

128
Q

Hfr x F- Conjugation

A

F+ plasmid can become incorporated into bacterial chromosomal DNA, now termed Hfr cell. Replication of incoporated plasmid DNA may include some flanking chromosomal DNA. Transfer of plasmid and chromosomal genes.

129
Q

Generalized transduction

A

Lytic phage infects bacterium, leading to cleavage of bacterial DNA and synthesis of viral proteins. Parts of bacterial chromosomal DNA may become packaged in viral capsid. Phage infects another bacterium, transferring these genes.

130
Q

Specialized transduction

A

Lysogenic phage infects bacterium; viral DNA incorporated into bacterial chromosome. When phage DNA is excised, flanking bacterial gnees may be excised w/ it. DNA is packaged into phage viral capsid and can infect another bacterium.

131
Q

Transposition (transposons)

A

Segment of DNA can jump (excision and reincorporation) from one location to another, can transfer genes from plasmid to choromosome and vice versa. When excision occurs, may include some flanking chromosomal DNA, which can be incorporated into a plasmid and transferred to another bacterium.

132
Q

5 bacterial toxins encoded in a lysogenic phage

A

ABCDE ShigA -like toxin B otulinum toxin (certain strains) C holera toxin D iphtheria toxin E rythrogenic toxin of Streptococcus pyogenes

133
Q

Which bugs are catalase-positive?

A

S.aureus, Serratia, Pseudomonas, Actinomyces, Candida, E.coli (SSPACE for you CATs)
Degrades H2O2 before it can be converted to microbicidal products by enzyme myeloperoxidase. People with chronic granulomatous disease (NADPH oxidase deficiency) have recurrent infections with these microbes because they degrade the limited H2O2.

134
Q

How do vaccines containing polysaccharide work?

A

A polysaccharide antigen alone would not be recognized and presented by T cells (only IgM antibodies produced). A protein is conjugated to polysaccharide antigen to promote T-cell activation and subsequent class switching A.

135
Q

What are examples of polysaccharide vaccines?

A

Pneumovax (polysaccharide vaccine with no conjugated protein), H. influenzae type B (conjugated vaccine), Meningococcal vaccines

USMLE1 - Microbiology (7 decks)

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