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Step 1 Exam > Microbiology Bacteria - First Aid > Flashcards

Microbiology Bacteria - First Aid Flashcards

1
Q

Function of Peptidoglycan

A

gives rigid support, protects against osmotic pressure

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2
Q

Composition of Peptidoglycan

A

sugar backbone with peptide side chains cross-linked by transpeptidase

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3
Q

Cell wall/cell membrane (gram positives) function

A

major surface antigen

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4
Q

Cell wall/cell membrane composition

A

peptidoglycan for support; lipoteichoic acid that induces TNF and IL-1

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5
Q

Outer membrane (gram negatives) function

A

site of endotoxin (lipopolysaccharide (LPS)): major surface antigen

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6
Q

Outermembrane composition

A

Lipid A induces TNF and IL-1; O polysaccharide is the antigen.

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7
Q

Plasma membrane function

A

site of oxidative and transport enzymes

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8
Q

Plasma membrane composition

A

phospholipid bilayer

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9
Q

Ribosome function

A

protein synthesis

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10
Q

Ribosome composition

A

50S and 30S subunits

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11
Q

Periplasm function

A

space between the cytoplasmic membrane and outer membrane in gram negative bacteria

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12
Q

Periplasm composition

A

contains many hydrolytic enzymes, including beta-lactamases

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13
Q

Capsule function

A

protects against phagocytosis

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14
Q

Capsule composition

A

polysaccharide (except Bacillus anthracis which contains D-glutamate)

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15
Q

Pilus/fimbria function

A

mediate adherence of bacteria to cell surface; sex pilus forms attachment between 2 bacteria during conjugation

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16
Q

Pilus/fimbria composition

A

glycoprotein

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17
Q

Flagellum function

A

motility

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18
Q

Flagellum composition

A

protein

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19
Q

Spore function

A

resistant to dehydration, heat and chemicals

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20
Q

Spore composition

A

keratin-like coat; dipicolinic acid; peptidoglycan

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21
Q

Plasmid function

A

consists of a variety of genes for antibiotic resistance, enzymes and toxins

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22
Q

Plasmid composition

A

DNA

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23
Q

Glycocalyx function

A

mediates adherence to surfaces, especially foreign surfaces (indwelling catheters)

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24
Q

Glycocalyx composition

A

polysaccharide

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25
Q

Circular (coccus) gram positives

A

Staphylococcus

Streptococcus

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26
Q

Circular (coccus) gram negatives

A

Neisseria

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27
Q

Rod (bacillus) gram positives

A 
Clostridium
Corynebacterium
Bacillus
Listeria
Mycobacterium (acid fast)
Gardnerella (gram variable)
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28
Q

Rod (bacillus) gram negative enterics

A 
E. coli
Shigella
Salmonella
Yersinia
Klebsiella
Proteus
Enterobacter
Serratia
Vibrio
Campylobacter
Helicobacter
Pseudomonas
Bacteroides
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29
Q

Rod (bacillus) gram negative respiratory

A

Haemophilus (pleomorphic)
Legionella (silver)
Bordetella

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30
Q

Rod (bacillus) gram negative zoonotics

A

Francisella
Brucella
Pasteurella
Bartonella

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31
Q

Branching filamentous gram positive

A

Actinomyces

Nocardia (weakly acid fast)

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32
Q

Pleomorphic gram negatives

A

Rickettsiae (Giemsa)

Chlamydiae (Giemsa)

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33
Q

Spiral gram negatives

A

Borrelia (Giemsa)
Leptospira
Treponema

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34
Q

No cell wall

A

Mycoplasma (does not gram stain)

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35
Q

Mycoplasma contains…

A

sterols and has no cell wall.

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36
Q

Mycobacteria contains…

A

mycolic acid and has a high lipid content.

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37
Q

These bugs do not gram stain well:

A 
Treponema
Mycobacteria
Mycoplasma
Legionella pneumophila
Rickettsia
Chlamydia
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38
Q

Treponema does not gram stain well becasue…

A

it is too thin to be visualized.

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39
Q

Mycobacteria does not gram stain well but its…

A

high lipid content in cell wall is detected by carbolfuchsin in acid-fast stain.

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40
Q

Mycoplasma does not gram stain well because…

A

it has no cell wall.

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41
Q

Legionella pneumophila does not gram stain well because…

A

it is primarily intracellular.

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42
Q

Rickettsia does not gram stain well because…

A

it is an intracellular parasite.

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43
Q

Chlamydia does not gram stain well becasue….

A

it is an intracellular parasite and lacks muramic acid in the cell wall.

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44
Q

Treponemes can be visualized with…

A

dark-field microscopy and fluorescent antibody staining.

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45
Q

Legionella can be visualized with…

A

silver stain.

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46
Q

Giemsa stain

A 
Chlamydia
Borrelia
Rickettsiae
Trypanosomes
Plasmodium

(Certain Bugs Really Try my Patience)

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47
Q

PAS (periodic acid-Schiff) stain

A

stains glycogen, mucopolysaccharides

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48
Q

PAS stain is used to diagnose…

A

Whipple disease (Tropheryma whipplei).

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49
Q

Ziehl-Neelson (carbol fuchsin) stain

A

acid-fast organisms (Nocardia, Mycobacterium)

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50
Q

India Ink Stain

A

Cryptococcus neoformans (mucicarmine can also be used to stain the thick polysaccharide capsule red)

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51
Q

Silver stain

A

Fungi (Pneumocystis)
Legionella
Helicobacter pylori

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52
Q

Media used for H. influenzae

A

chocolate agar w/ factors V (NAD+) and X (hematin)

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53
Q

Media used for N. gonorrhea and N. meningitidis

A

Thayer-Martin (VPN) with Vancomycin, Polymyxin and Nystatin

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54
Q

In the VPN media, Vancomycin acts to…

A

inhibit gram-postitive organism. Polymyxin inhibits gram-negative except for Neisseria. And Nystatin inhibits fungi.

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55
Q

Media used for Bordetella pertussis

A

Bordet-Gengou (potato) agar

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56
Q

Media used for C. diptheriae

A
  • Tellurite agar

- Loffler medium

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57
Q

Media used for M. tuberculosis

A

-Lowenstein-Jensen agar

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58
Q

Media used for M. pneumoniae

A

-Eaton agar, requires cholesterol

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59
Q

Media used for lactose fermenting enterics

A

pink colonies on MacConkey agar

fermentation produces acid, turning the colony pink

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60
Q

E. coli is also grown on…

A

eosin-methylene blue (EMB) agar as colonies with green metallic sheen.

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61
Q

Media used for Legionella

A

Charcoal yeast extract agar buffered with cysteine and iron

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62
Q

Media for fungi

A

Sabouraud agar

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63
Q

Obligate aerobes use…

A

O2-dependent system to generate ATP.

Examples include Nocardia, Pseudomonas aeruginosa and Mycobacterium tuberculosis.

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64
Q

Reactivation of M. tuberculosis (after immune compromise or TNF-alpha inhibitor use) has a predilection for…

A

the apices of the lung, which have the highest PO2.

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65
Q

P. aeruginosa is an aerobe seen in…

A

burn wounds, diabetes complications, nosocomial pneumonia and pneumonias in CF pts.

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66
Q

Examples of Obligate Anaerobes

A
  • Clostridium
  • Bacteroides
  • Actinomyces
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67
Q

Obligate Anaerobes lack…

A

catalase and/or superoxide dismutase and are thus susceptible to oxidative damage.

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68
Q

Obligate Anaerobe general features

A
  • foul smelling (short-chain fatty acids)
  • difficult to culture
  • produce gas in tissue (CO2 and H2)
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69
Q

Anaerobes are normal…

A

flora in the GI tract and pathogenic elsewhere.

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70
Q

The antibiotic that is ineffective against anaerobes is…

A

aminoglycosides because this antibiotic requires O2 to enter the bacterial cell.

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71
Q

Obligate intracellualar bugs are…

A

Rickettsia and Chlamydia because they can’t make their own ATP.

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72
Q

Facultative intracellular bugs are…

A 
Salmonella
Neisseria
Brucella
Mycobacterium
Listeria
Francisella
Legionella
Yersinia

(Some Nasty Bugs May Live FacultativeLY)

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73
Q

Encapsulated Bacteria Examples

A 
Strep pneumponiae
Haemophilus influenza
Neisseria meningitidis
Escherichia coli
Salmonella
Klebsiella pneumoniae
group B Strep

(SHiNE SKiS)

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74
Q

Capsule + protein conjugate serves as…

A

an antigen in vaccines.

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75
Q

Encapsulated bacteria are normally…

A

opsonized and then cleared by the spleen. Asplenics have decreased opsonizing ability and are at risk for severe infection.

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76
Q

All asplenics should receive…

A

s. pneumoniae, H. influenzae and N. meningitidis vaccines.

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77
Q

Catalase acts to…

A

degrade H2O2 before it can be converted to microbicidal products by myeloperoxidase.

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78
Q

People with chronic granulomatous disease (NADPH oxidase deficiency) have…

A

recurrent infections with catalase + organisms.

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79
Q

Examples of Catalase + organisms

A 
Pseudomonas
Listeria 
Aspergillus
Candida
E. coli
S. aureus
Serratia

(You need PLACESS for your cat.)

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80
Q

Some vaccines containing polysaccharide capsule antigens are conjugated to a carrier protein, which….

A

enhances immunogenicity by promoting T-cell activation and subsequent class switching.

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81
Q

A polysaccharide antigen alone cannot be presented to…

A

T cells.

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82
Q

PCV

A

pneumococcal conjugate vaccine (Prevnar)

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83
Q

PPSV

A

pneumococcal polysaccharide vaccine with no conjugated protein (Pneumovax)

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84
Q

Hib and meningococcal vaccines are both…

A

conjugate vaccines.

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85
Q

Urease positive bugs

A 
Cryptococcus
H. pylori
Proteus
Ureaplasma
Nocardia
Klebsiella
S. epidermidis
S. saprophyticus

(CHuck Norris hates PUNKSS)

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86
Q

Pigment producing bacteria

A

Actinomyces israeli
S. aureus
Pseudomonas aeruginosa
Serratia marcescens

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87
Q

Actinomyces produces pigment that is…

A

yellow “sulfur” granules whcih are composed of filaments of bacteria

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88
Q

S. aureaus produces a…

A

yellow pigment.

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89
Q

Pseudomonas aeruginosa produces a…

A

blue-green pigment.

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90
Q

Serratia marcescens produces a…

A

red pigment.

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91
Q

Protein A

A

binds Fc region of IgG; prevents opsonization and phagocytosis

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92
Q

Protein A is expressed by…

A

S. aureus.

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93
Q

IgA protease is…

A

an enzyme that cleaves IgA.

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94
Q

IgA protease is secreted by…

A

S. pneumoniae, Hib, and Neisseria in order to colonize respiratory mucosa.

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95
Q

M protein helps…

A

prevent phagocytosis and is expressed by group A strep.

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96
Q

Source of exotoxin

A

certain species of some gram-postivive and gram-negative bacteria

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97
Q

Source of endotoxin

A

outer cell membrane of most gram-negative bacteria

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98
Q

Chemistry of exotoxins

A

polypeptide

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99
Q

Chemistry of endotoxins

A

Lipopolysaccharide (structural part of bacteria, released when lysed)

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100
Q

location of genes of exotoxins

A

plasmid or bacteriophage

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101
Q

location of genes of endotoxins

A

bacterial chromosomes

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102
Q

toxicity of exotoxin

A

high

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103
Q

toxicity of endotoxin

A

low

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104
Q

clinical effects of endotoxin

A

fever, shock, DIC

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105
Q

Mode of action of endotoxin

A

induces TNF, IL-1 and IL-6

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106
Q

Antigenicity of Exotoxin

A

induces high-titer antibodies called antitoxins

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107
Q

Antigenicity of Endotoxin

A

poorly antigenic

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108
Q

Vaccines of exotoxins

A

toxoids used as vaccines

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109
Q

Vaccines of endotoxins

A

no toxoids formed and no vaccines available

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110
Q

Heat stability of exotoxins

A

destroyed rapidly at 60 C (except staph enterotoxin)

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111
Q

Heat stability of endotoxins

A

stable at 100 C for 1 hr

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112
Q

Typical diseases of exotoxins

A

Tetanus
Botulism
Diptheria

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113
Q

Typical diseases of endotoxins

A

Meningococcemia

Sepsis by gram-negative rodsCory

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114
Q

Corynebacterium diphtheriae exotoxin

A

Diphtheria toxin inactives elongationg factor 2 (EF-2) causing pharyngitis with pseudomembranes in the throat and severe lymphadenopathy (bull neck).

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115
Q

Pseudomonas aeruginosa exotoxin

A

Exotoxin A inactivates EF-2 leading to host cell death.

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116
Q

Shigella exotoxin

A

Shiga toxin inactivates 60S ribosome by removing adenine from rRNA leading to GI mucosal damage (dysentery); ST also enhances cytokine release (HUS).

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117
Q

EHEC exotoxin

A

Shiga-like toxin inactivate 60S ribosome by removing adening from rRNA leading to cytokine release (HUS).

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118
Q

EHEC is different from Shigella because…

A

it does not invade host cells.

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119
Q

ETEC exotoxins

A

Heat-labile toxin (LT)

Heat-stable toxin (ST)

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120
Q

ETEC LT toxin

A

overactivates adenylate cyclase (increase cAMP) leading to increaesd chloride secretion in the gut and H2O efflux

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121
Q

ETEC ST toxin

A

overactivates guanylate cyclase (increases cGMP) leading to decreased resorption of NaCl and H2O in the gut

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122
Q

Manifestation of ETEC exotoxins

A

Watery Diarrhea

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123
Q

Bacillus anthracis exotoxin

A

Edema factor mimics the adenylate cyclase enzyme (increases cAMP). This is likely responsible for edematous borders of black eschar in cutaneous anthrax.

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124
Q

Vibrio cholerae exotoxin

A

Cholera toxin overactivates adenylate cyclase by permanently activating Gs leading to increased chloride secretion in the gut and H2O efflux. Manifestation is voluminous “rice-water” diarrhea.

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125
Q

Bordetella pertussis exotoxin

A

Pertussis toxin overactivates adenylate cyclase (increased cAMP) by disabling Gi, impairing phagocytosis to permit survival of the microbe.

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126
Q

Manifestation of the pertussis toxin

A

whooping cough: child coughs on expiration and “whoops” on inspiration

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127
Q

Clostridium tetani exotoxin

A

Tetanospasmin cleaves SNARE proteins required for NT release. Toxin prevents release of inhibitory (GABA and glycine) from Renshaw cells in the spinal cord.

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128
Q

Manifestation of the Tetanospasmin toxin

A
  • spasticity
  • risus sardonicus
  • lockjaw
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129
Q

Clostridium botulinum exotoxin

A

Botulinum toxin cleaves SNARE proteins required for NT release. Prevents release of stimulatory (ACh) signals at NMJs leading to flaccid paralysis.

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130
Q

Manifestations of Botulinum toxin

A
  • flaccid paralysis

- floppy baby

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131
Q

Diptheria toxin, Exotoxin A, Shiga toxin, Shiga-like toxin, Heat-labile toxin, Cholera toxin and Pertussis toxin are all…

A

ADP ribosylating A-B toxins. The B component binds to host cell surface receptor enabling endocytosis. The A component attaches ADP-ribosyl to disrupt host cell prtoeins.

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132
Q

Clostridium perfringens exotoxin

A

Alpha toxin is a phospholipse (lecithinase) that degrades tissue and cell membranes.

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133
Q

Manifestation of Clostridium perfringens alpha toxin

A

degradation of phospholipids leads to myonecrosis (“gas gangrene”) and hemolysis (“dobule zone” of hemolysis on blood agar)

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134
Q

Streptococcus pyogenes exotoxin

A

Streptolysin O is a protein that degrades cell membranes

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135
Q

Manifestation of Streptolysin O

A

lyses RBCs
contributes to beta-hemolysis
host antibodies against toxin (ASO) are used to diagnose rheumatic fever

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136
Q

Staphylococcus aureus exotoxin

A

Toxic shock syndrome toxin (TSST-1) brings MHC II and TCR in proximity to the outside of an antigen binding site to cause an overwhelming release of IFN-gamma and IL-2 leading to shock.

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137
Q

Manifestation of TSST-1 and Exotoxin A

A

Toxic shock syndrome: fever, rash, shock

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138
Q

Other toxins of Staph aureus cause…

A

scalded skin syndrome (exfoliative toxin) and food poisoning (enterotoxin).

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139
Q

Strep pyogenes exotoxin

A

Exotoxin A brings MHC II and TCR in proximity to the outside of an antigen binding site to cause overwhelming release of IFN-gamma and IL-2 leading to shock.

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140
Q

Tranformation

A

ability to take up DNA from the environment; seen in S. pneumoniae, Hib and Neisseria

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141
Q

F+ x F- Conjugation

A

F+ plasmid contains genes required for sex pilus and conjugation. Bacteria without this plasmid are termed F-. Plasmid (dsDNA) is replicated and transferred through the pilus from the F+ cell. There is no transfer of chromosomal genes.

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142
Q

Hfr x F- conjugation

A

F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high-frequency recombination (Hfr) cell. Replication of incorporated plasmid DNA may include some flanking chromosomal DNA. Transfer of plasmid and chromosomal genes.

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143
Q

Transposition

A

Segment of DNA (transposon) that can “jump” can transfer genes from plasmid to chromosome and vice versa.

144
Q

Examples of transposition include…

A

antibiotic resistance gene on R plasmid.

145
Q

Generalized transduction

A

Lytic phage infects bacterium leading to cleavage of bacterial DNA. Parts of bacterial chromosomal DNA becom packaged in viral capsid. Then the phage infects another bacterium, transferring the genes.

146
Q

Specialized transduction

A

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 then packaged into phage viral capsid and can infect another bacterium.

147
Q

Genes for the following 5 bacterial toxins are encoded in a lysogenic phage:

A

ABCDE

  1. ShigA-like toxin
  2. Botulinum toxin
  3. Cholera toxin
  4. Diphtheria toxin
  5. Erythrogenic toxin of S. pyogenes
148
Q

Novobiocin sensitivity

A

Staph saprophyticus is resistant.

Staph epidermidis is sensitive.

149
Q

Optochin sensitivity

A

Strep viridans is resistant.

Strep pneumoniae is sensitive.

150
Q

Bacitracin sensitivity

A

group B strep are resistant

group A strep are sensitive

151
Q

Alpha-hemolytic bacteria form…

A

a green ring around colonies on blood agar

152
Q

Alpha-hemolytic bacteria include:

A

Strep pneumoniae

Viridans strep

153
Q

Beta-hemolytic bacteria form…

A

a clear area of hemolysis on blood agar.

154
Q

Beta-hemolytic bacteria include…

A

Staph aureus
Strep pyogenes
Strep agalactiae
Listeria

155
Q

Staphylococcus aureus features

A
  • gram positive cocci in clusters
  • Protein A (binds Fc-IgG, inhibiting complement activation and phagocytosis)
  • commonly colonizes the nose
156
Q

Staph aureus causes (3):

A
  1. inflammatory disease
  2. Toxin-mediated disease
  3. MRSA infection
157
Q

Inflammatory diseases of Staph aureus

A
  • skin infections
  • organ abcesses
  • pneumonia (often after virus infxn)
  • endocarditis
  • osteomyelitis
158
Q

MRSA infection is an important cause of…

A

serious nosocomial and community acquired infections; resistant to methicillin and nafacillin because of altered penicillin binding protein (PBP).

159
Q

Use of vaginal or nasal tampons predisposes to…

A

toxic shock syndrome.

160
Q

S. aureus food poisonin is due to…

A

ingestion of a preformed toxin (that is not destroyed by cooking). Short incubation (2-6 hrs).

161
Q

S. aureus is able to form a…

A

fibrin clot around itself leading to abscess.

162
Q

Staphylococcus epidermidis infects…

A

prosthetic devices and IV catheters by producing adherrent biofilms

163
Q

S. epidermidis is a normal part of…

A

skin flora and can contaminate blood cultures.

164
Q

Staphylococcus saprophyticus is the second most common cause of…

A

uncomplicated UTI in young women.

165
Q

Streptococcus pneumoniase is the most common casue of:

A
  1. Meningitis
  2. Otitis media
  3. Pneumonia
  4. Sinusitis
166
Q

Strep pneumoniae features

A
  • lancet-shpaed, gram-positive diplococci
  • encapsulated
  • IgA protease
167
Q

Pneumococcus is associated with…

A

rusty sputum
sepsis in sickle cell anemia
splenectomy

168
Q

Strep pneumoniae has no virulence without..

A

its capsule.

169
Q

Viridans strep features

A
  • alpha-hemolytic

- normal flora of the oropharynx

170
Q

Viridans group strep causes…

A 
dental caries (S. mutans)
bacterial endocarditis (S. sanguinis)
171
Q

S. sanguinis makes…

A

dextrans which bind to fibrin-platelet aggregates on damaged heart valves.

172
Q

Streptococcus pyogenes (Group A) causes…

A

pyogenic, toxigenic and immunologic diseases.

173
Q

Pyogenic diseases of S. pyogenes

A
  • pharyngitis
  • cellulitis
  • impetigo
174
Q

Toxigenic diseases of S. pyogenes

A
  • scarlet fever
  • toxic shock-like syndrome
  • necrotizing fasciitis
175
Q

Immunologic diseases of S. pyogenes

A
  • rheumatic fever

- acute glomerulonephritis

176
Q

Antibodies to M protein enhance…

A

host defenses against S. pyogenes but can give rise to rheumatic fever.

177
Q

Recent S. pyogenes infection is detected by…

A

ASO titer.

178
Q

JONES criteria for Rheumatic Fever

A 
Joints (polyarthritis)
<3 (carditis)
Nodules (subcutaneous)
Erythema marginatum
Sydenam chorea
179
Q

Impetigo more commonly precedes…

A

glomerulonephritis than pharyngitis.

180
Q

Scarlet Fever

A

scarlet rash w/ sandpaper-like texture; strawberry tongue, circumoral pallor

(caused by S. pyogenes)

181
Q

Streptococcus agalactiae (group B) features

A
  • beta-hemolytic
  • colonizes the vagina
  • causes pneumonia, meningitis and sepsis mainly in babies
  • Hippurate test +
182
Q

S. agalactiae produces…

A

CAMP factor which enlarges the area of hemolysis formed by S. aureus.

183
Q

Pregnant pts with a positive screen for S. agalactiae at…

A

35-37 wks should receive intrapartum penicillin prophylaxis.

184
Q

Enterococci (group D strep) features

A
  • normal colonic flora
  • penicillin G resistant
  • cause UTI, biliary tract infections and subacute endocarditis
185
Q

Lancefield grouping of streptococci is based on…

A

differences in the C carbohydrate on the bacterial cell wall.

186
Q

VRE (vancomycin-resistant enterococci) are an important cause of…

A

nosocomial infection.

187
Q

Lab test for enterococci

A

can grow in 6.5% NaCl and bile

188
Q

Streptococcus bovis (group D streptococci)

A

colonizes the gut; can cause bacteremia and endocarditis in colon cancer pts

189
Q

Bovis in the blood =

A

cancer in the colon

190
Q

Corynebacterium diphtheriae causes…

A

diphtheria via exotoxin encoded by Beta-prophage.

191
Q

Symtpoms of diptheria

A
  • pseudomembranous pharyngitis (grayish-white membrane)
  • lymphadenopathy
  • myocarditis
  • arrhythmias
192
Q

Lab diagnosis of C. diphtheriae is based on…

A

gram-positive rods with metachromatic (blue and red) granules and Elek test for toxin.

(shaped like a club)

193
Q

Diphtheria can be prevented with…

A

a toxoid vaccine.

194
Q

C. diphtheriae show black colonies on…

A

cystine-tellurite agar.

195
Q

Some bacteria can form spores at the end of the…

A

stationary phase when nutrients are limited.

196
Q

Spores features (3)

A
  • highly resistant to heat and chemicals
  • have dipicolinic acid in their core
  • no metabolic activity
197
Q

To kill spores, you must…

A

autoclave them by steaming at 121 C for 15 min.

198
Q

Spore forming gram positive bacteria found in soil (3)

A
  1. Bacillus anthracis
  2. Clostridium perfringens
  3. Clostridium tetani
199
Q

Other spore formers inlcude (3):

A
  1. B. cereus
  2. C. botulinism
  3. Coxiella burnetii
200
Q

Clostridia features (3)

A
  • gram positive
  • spore forming
  • obligate anaerobic bacteria
201
Q

C. tetani produces…

A

tetanospasmin, an exotoxin causing tetanus.

202
Q

Tetanus is…

A

tetanic paralysis (blocks glycine and GABA release from Renshaw cells in the spinal cord). Causes spastic paralysis, trismus (lockjaw) and risus sardonicus.

203
Q

C. botulinism causes disease in adults by…

A

ingestion of a preformed toxin. In babies, ingestion of spores in honey causes the disease.

204
Q

C. difficile produces…

A

2 toxins:

  1. Toxin A (enterotoxin) binds to the brush border of the gut.
  2. Toxin B (cytotoxin) causes cytoskeletal disruption via actin depolymerization leading to pseudomembranous colitis and diarrhea.
205
Q

C. diff often occurs secondary to…

A

antibiotic use (esp. clindamycin and ampicillin).

206
Q

C. diff is diagnosed by…

A

detection of one or both of the toxins in the stool.

207
Q

Tretment for C. diff

A

Metronidazole or Oral Vancomycin

fecal transplant may prevent relapse in recurring infxns

208
Q

Bacillus anthracis features (4):

A
  1. gram positive
  2. spore-forming rod
  3. produces anthrax toxin (causing anthrax)
  4. only bacterium with a polypeptide capsule (contains D-glutamate)
209
Q

Cutaneous anthrax

A

A boil like lesion leads to an ulcer with black eschar (painless, necrotic). This can but rarely leads to bacteremia and death.

210
Q

Pulmonary anthrax

A

Inhalation of spores leads to flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis and shock.

211
Q

Woolsorter’s disease

A

inhalation of anthrax spores from contaminated wool

212
Q

Bacillus cereus causes…

A

food poisoning. Spores survive cooking in rice (and pasta). Keeping rice warm results in germination of spores and enterotoxin formation.

213
Q

2 Types of B. cereus food poisoning

A
  1. Emetic type (nausea/vomiting within 1-5 hrs, caused by cereulide (a preformed toxin))
  2. Diarrheal type (watery, nonbloody diarrhea and GI pain w/i 8-18 hrs)
214
Q

Listeria monocytogenes is a…

A

facultative intracellular microbe. It is the only gram-positive bacteria to produce LPS.

215
Q

Listeria monocytogenes forms…

A

“rocket tails” via actin polymerization that allow them to move through the cytoplasm and into the cell membrane, thereby avoiding abtibody. Characteristic tumbling motility.

216
Q

Listeria monocytogenes is acquired by…

A

ingestion of unpasteurized dairy products an deli meats, via transplacental transmission or vaginal transmission during birth.

217
Q

Listeria monocytogenes causes:

A
  1. amnionits
  2. septicemia
  3. spontaneous abortion
  4. granulomatosis infantiseptica
  5. neonatal meningitis
  6. meningitis in immunocompromised pts
  7. mild gastroenteritis
218
Q

Treatment for Listeria

A

Ampicillin in infants, immunocompromised pts and the elderly in empiric tx of meningitis.

219
Q

Both Actinomyces and Nocardia form…

A

long, branching filaments resembling fungi.

220
Q

Actinomyces features

A
  1. gram positive anaerobe
  2. normal oral flora
  3. causes oral/facial abcesses that drain through sinus tracts and form yellow “sulfur granules”
  4. treat with penicillin
221
Q

Nocardia features

A
  1. gram positive aerobe
  2. acid fast (weak)
  3. found in soil
  4. causes pulmonary infxns in immunocompromised and cutaneous infections after trauma in immunocompetent
  5. treat with sulfonamides
222
Q

Pts will be PPD+ for TB if…

A

they have a current infxn, past exposure or BCG vaccinated.

223
Q

Pts will be PPD- for TB if…

A

they have no infxn or are anergic (steroids, malnutrition, immunocompromised) and in sarcoidosis.

224
Q

A more specific test for TB is…

A

an interferon gamma release assay (IGRA) which has fewer false positives from the BCG vaccine.

225
Q

Mycobacterium kansasii causes…

A

pulmonary TB-like symptoms.

226
Q

Mycobacterium avium-intracellulare causes…

A

disseminated, non-TB disease in AIDS pts; give prophylactic treatment with Azithromycin.

227
Q

TB symptoms include…

A

fever, night sweats, weight loss and hemoptysis.

228
Q

Virulent strains of mycobacterium have…

A

cord factor which inhibits macrophage maturation and induces release of TNF-alpha.

Sulfatides (surface glycolipids) inhibit phagolysosomal fusion.

229
Q

Leprosy (Hansen Disease) is caused by…

A

Mycobacterium leprae, an acid-fast bacillus that likes cool temperatures (infects skin and superficial nerves).

230
Q

Lepromatous form of Hansen Disease

A

presents diffusely over the skin with leonine facies and is communicable; characterized by low cell-mediated immunity with a humoral Th2 response.

231
Q

Tuberculoid form of Hansen Disease

A

limited to a few hypoesthetic, hairless skin plaques; characterized by high cell-mediated immunity w/ a largely Th1 immune response

232
Q

Treatment for Leprosy

A

Tuberculoid form: Dapsone and Rifampin for 6 months

Lepromatous form: Dapsone, Rifampin, Clofazimine for 2-5 yrs

233
Q

Examples of Lactose-fermenting enteric bacteria (5)

A
  1. Citrobacter
  2. Klebsiella
  3. E. coli
  4. Enterobacter
  5. Serratia (weak fermenter)
234
Q

E.coli produces…

A

Beta-galactosidase, which breaks down lactose into glucose and galactose.

235
Q

On EMB agar, lactose fermenters grow as…

A

purple/black colonies. E.coli also has a green sheen.

236
Q

Gram-negative bacilli are resistant to…

A

penicillin G but may be susceptible to penicillin derivatives such as ampicillin and amoxicillin.

237
Q

Gram-negative bacilli are resistant to penicllin G and vancomycin because…

A

the outer membrane layer inhibits entry of the drugs.

238
Q

Neisseria features

A
  • gram negative diplococci
  • ferment glucose
  • produce IgA protease
  • N. gonorrhea is often intracellular (w/i neutrophils)
239
Q

Neisseria gonococci features

A
  • sexually transmitted

- causes gonorrhea, septic arthritis, neonatal conjuctivitis, PID and Fitz-Hugh-Curtis syndrome

240
Q

Neonatal transmission of N. gonorrhae can be prevented with…

A

erythromycin ointment.

241
Q

Treatment for N. gonorrhae

A

Ceftriaxone + (azithromycin or doxycycline) for possible chlamydia coinfection

242
Q

Neisseria menigococci features

A
  • polysaccharide capsule
  • maltose fermentation
  • vaccine
  • respiratory and oral secretions
  • causes meningococcemia and meningitis and waterhouse-friderichsen syndrome
243
Q

N. meningitidis can be prevented in close contacts with…

A

rifampin, ciprofloxacin or ceftriaxone prophylaxis.

244
Q

Treatment for N. meningitidis

A

Ceftriaxone or Penicillin G

245
Q

Haemophilus influenzae features

A
  • small, gram negative rod
  • aerosol transmission
  • produces IgA protease A
246
Q

Haemophilus influenzae causes…

A

Epiglottitis (cherry red/thumbprint sign)
Meningitis
Otitis media
Pneumonia

247
Q

H. influenzae mucosal infections can be treated with…

A

Amoxicillin +/- Clavulanate.

248
Q

Hib meningitis can be treated with…

A

ceftriaxone. And Rifampin can be given to close contacts for prophylaxis.

249
Q

The H. influenzae vaccine contains…

A

type B capsular polysaccharide (polyribosylribitol phosphate) conjugated to diphtheria toxoid. Given between 2 and 18 months of age.

250
Q

H. influenzae does not cause…

A

the flu. The influenza virus does.

251
Q

Legionella pneumophila features

A
  • gram-negative rod
  • use silver stain
  • grow on charcoal yeast extract culture with iron and cysteine
252
Q

Transmission of Legionella pneumophila

A

Aerosol transmission from environmental water source habitat (air conditioning, hot water tanks). No person-to-person transmission.

253
Q

Legionella pneumophila is detected clinically by…

A

presence of antigen in the urine.

254
Q

Treatment for Legionella

A

Macrolide or Quinolone

255
Q

Labs for Legionella show…

A

hyponatremia.

256
Q

Legionella causes…

A

Legionnaires’ disease and Pontiac fever.

257
Q

Pontiac Fever is…

A

a mild flu-like syndrome.

258
Q

Legionnaire’s disease is…

A

severe pneumonia, fever, GI and CNS symptoms

259
Q

Pseudomonas aeruginosa features

A
  • aerobic, gram-negative rod
  • non lactose fermenting
  • oxidase +
  • produces pyocyanin (blue-green pigment)
  • grape-like odor
  • water source
  • produces endotoxin and exotoxin A
260
Q

Pseudomonas is associated with:

A 
wound and burn infections
pneumonia (esp. CF)
Sepsis
external otitis (swimmer's ear)
UTI
Drug use
Diabetic Osteomyelitis
hot tub folliculitis
Ecthyma gangrenosum
261
Q

Ecthyma gangrenosum is…

A

a rapidly progressive, necrotic cutaneous lesion caused by Pseudomonas bacteremia. Typically in immunocompromised pts.

262
Q

Treatment for pseudomonas aeruginosa

A

aminoglycoside plus extended spectrum penicillin

263
Q

Chronic pneumonia in CF pts is associated with…

A

biofilm from pseudomonas.

264
Q

E. coli virulence factors (and what they cause)

A
  1. fimbrae - cystitis and pyelonephritis
  2. K capsule - pneumonia and neonatal meningitis
  3. LPS endotoxin - septic shock
265
Q

EIEC mechanism

A

microbe invades intestinal mucosa and causes necrosis and inflammation (similar manifestations to Shigella)

266
Q

EIEC presentation

A

dysentery

267
Q

ETEC mechanism

A

produces heat-labile and heat-stable enterotoxins. no inflammation or invasion

268
Q

ETEC presentation

A

travelere’s diarrhea (watery)

269
Q

EPEC mechanism

A

no toxin produced; adheres to apical surface, flattens villi, prevents absorption

270
Q

EPEC presentation

A

diarrhea (usually in children)

271
Q

EHEC mechanism

A

O157:H7 is the most common serotype. produces shiga-like toxin that causes HUS (triad of anemia, thrombocytopenia and acute renal failure). Microthrombi form on the endothelium damaged by the toxin leading to mechanical hemolysis (schistocytes) and decreased renal blood flow.; microthrombi consume platelets leading to thrombocytopenia.

272
Q

EHEC presentation

A

dystentery

273
Q

EHEC is distinguished from other forms of E. coli because…

A

it does not ferment sorbitol.

274
Q

Klebsiella features

A
  • mucoid colonies caused by abundant polysaccharide capsules
  • red “currant jelly” sputum
  • intestinal flor
275
Q

Klebsiella causes…

A

lobar pneumonia in alcoholics and diabetics when aspirated. (abscesses in lungs and liver)

Can also cause nosocomial UTIs.

276
Q

Salmonella features

A
  • flagella
  • disseminate hematogenously
  • many animal reservoirs
  • produces hydrogen sulfide
  • does not ferment lactose
277
Q

Antibiotics for salmonella may…

A

prolong fecal excretion of the organism.

278
Q

Salmonella acts by…

A

invading intestinal mucosa and causing a monocytic response sometimes leading to bloody diarrhea.

279
Q

Shigella features

A
  • cell to cell transmission
  • human and primate reservoirs
  • does not ferment lactose
280
Q

Abitibotics for shigella may…

A

shorten the duration of fecal excretion of the organism.

281
Q

Shigella acts by…

A

invading intestinal mucosa and causing PMN infiltration often leading to bloody diarrhea.

282
Q

Salmonella typhi causes…

A

typhoid fever characterized by red spots on the abdomen, fever, HA and diarrhea.

283
Q

Salmonella typhi can remain in the…

A

gallbladder and cause a carrier state.

284
Q

Campylobacter jejuni is a major cause…

A

of bloody diarrhea.

285
Q

Campylobacter is transmitted…

A

fecal-orally through foods such as poultry, meat and unpasteurized milk.

286
Q

Features of Campylobacter jejuni

A
  • comma or S-shaped
  • oxidase +
  • grows at 42 C
287
Q

Campylobacter is a common antecedant to…

A

Guillain-Barre Syndrome and reactive arthritis.

288
Q

Vibrio cholerae produces…

A

rice-water diarrhea via enterotoxin that permanently activates Gs (increasing cAMP). Prompt oral rehydration is necessary.

289
Q

Vibrio cholerae features

A
  • comma shaped
  • oxidase +
  • grows in alkaline media
  • endemic to developing countries
290
Q

Yersinia enterocolitica is usually transmitted from…

A

pet feces, contaminated milk or pork.

291
Q

Yersinia enterocolitica causes…

A

mesenteric adenitis that can mimic Chron’s or appendicitis.

292
Q

Helicobacter pylori causes…

A

gastritis and peptic ulcer (esp. duodenal).

293
Q

H. pylori is a risk factor for…

A

peptic ulcer, gastric adenocarcinoma and lymphoma.

294
Q

H. pylori features

A
  • curved, gram negative rod
  • catalase +
  • oxidase +
  • urease +
  • creates an alkaline environment
295
Q

Most common initial treatment for H. pylori is…

A

proton pump inhibitor + Clarithromycin + either amoxicillin or metronidazole

296
Q

Spirochetes are…

A

spiral-sharped bacteria with axial filaments and include Borrelia, Leptospira and Treponema.

297
Q

Of the spirochetes, only Borrelia can be visualized using…

A

aniline dyes (Wright or Giemsa stain) in light microscopy.

298
Q

Treponema is visualized by…

A

dark-field microscopy.

299
Q

Leptospira interrogans is found in…

A

water contaminated with animal urine and causes leptospirosis: flu-like symptoms, jaundice, photophobia with conjunctival suffusion (erythema without exudate).

300
Q

Leptospira interrogans is prevalent among…

A

surfers and in the tropics (Hawaii).

301
Q

Weil Disease

A

severe form of leptospirosis with jaundice and azotemia from liver and kidney dysfunction; fever, hemorrhage and anemia

302
Q

Lyme disease is caused by..

A

Borrelia burgdorferi which is transmitted by the tick Ixodes. Natural reservoir is the mouse.

303
Q

Initial symptoms of lyme disease

A

-erythema chronicum migrans
-flu like symptoms
+/- facial nerve palsy

304
Q

Later symptoms of lyme disease

A
  • monoarthritis
  • migratory polyarthritis
  • AV nodal block
  • encephalopathy
  • facial nerve palsy
  • polyneuropathy
305
Q

Treatment for Lyme Disease

A

Doxycycline, Ceftriaxone

306
Q

Syphlis is caused by…

A

the spirochete Treponema pallidum.

307
Q

Primary syphilis

A

a localized diseae presenting with painless chancre

308
Q

Serologic testing for primary and secondary syphilis

A

VDRL/RPR (non-specific)

Confirm w/ specific test (FTA-ABS).

309
Q

Secondary syphilis

A

disseminated disease with constitutional symptoms, maculopapular rash (palms and soles), condylomata lata

310
Q

Tertiary syphilis

A

Gummas (chronic granulmoas), aortitis (vasa vasorum destruction), neurosyphilis (tabes dorsalis “general paresis”), Argyll Robertson pupil

311
Q

Signs of Tertiary syphilis

A
  • broad-based ataxia
  • positive Romberg
  • Charcot joint
  • stroke w/o HTN
312
Q

To diagnose tertiary syphilis, test…

A

spinal fluid with VDRL or RPR.

313
Q

Congenital syphilis signs

A
  • saber shins
  • saddle nose
  • CN VIII deafness
  • Hutchinson teeth
  • mulberry molars
314
Q

To prevent congenital syphilis:

A

treat mother early in pregnancy bc transmission usually occurs after the 1st trimester

315
Q

Argyll Robertson pupil

A

constricts with accommodation but is not reactive to light

associated with tertiary syphilis

316
Q

VDRL detects…

A

nonspecific antibody that reacts with beef cardiolipin; it is sensitive for syphilis but not specific.

317
Q

VDRL has many false positives due to…

A

viral infection (mono, hepatitis)
drugs
rheumatic fever
SLE

318
Q

Jarisch-Herxheimer rxn

A

flu-like syndrome after antibiotics are started - due to killed bacteria releasing pyrogens

319
Q

Anaplasma is a zoonotic bacteria that causes…

A

anaplasmosis from ixodes ticks.

320
Q

Bartonella is a zoonotic bacteria that causes…

A

cat scratch disease, bacillary angiomatosis from cat scratches.

321
Q

Borrelia recurrentis is a zoonotic bacteria that casues…

A

relapsing fever from louse.

322
Q

Brucella is a zoonotic bacteria that causes…

A

Brucellosis/undulant fever from unpasteruized dairy.

323
Q

Chlamydophila psittaci is a zoonotic bacteria that causes…

A

Psittacosis from parrots and other birds.

324
Q

Coxiella burnetii is a zoonotic bacteria that causes…

A

Q fever from aerosols of cattle/sheep amniotic fluid.

325
Q

Ehrlichia chaffeensis is a zoonotic bacteria that causes..

A

Ehrlichiosis from Lone Star ticks.

326
Q

Francisella tularensis is a zoonotic bacteria that causes…

A

Tularemia from ticks, rabbits and deer fly.

327
Q

Pasteurella multocida is a zoonotic bacteria that causes…

A

cellulitis and osteomyelitis from animal bites, cats and dogs.

328
Q

Rickettsia prowazekii is a zoonotic bacteria that causes…

A

epidemic typhus from louse.

329
Q

Rickettsia rickettsii is a zoonotic bacteria that causes…

A

Rocky Mountain spotted fever from dermacentor ticks.

330
Q

Rickettsia typhi is a zoonotic bacteria that causes…

A

endemic typhus from fleas.

331
Q

Yersinia pestis is a zoonotic bacteria that causes….

A

plague from fleas.

332
Q

Gardnerella vaginalis is a…

A

pleomorphic rod that presents with vaginosis as a gray vaginal discharge with a fishy smell; nonpainful.

333
Q

Gardnerella is associated with…

A

sexual activity but is not sexually transmitted.

334
Q

Bacterial vaginosis is also characterized by….

A

overgrowth of certain anaerobic bacteria in the vagina.

335
Q

In bacterial vaginosis, under the microscope….

A

clue cells, or vaginal epithelial cells covered with the Gardnerella bacteria are visible.

336
Q

Treatment for Gardnerella vaginalis

A

Metronidazole (or Clindamycin to treat anaerobic bacteria).

337
Q

Treatment for all Rickettsial disease and vector-borne illnesses is…

A

Doxycycline.

338
Q

Rocky Mountain Spotted Fever occurs primarily in…

A

the South Atlantic States (esp. North Carolina). Rash starts at wrists and ankles and spreads to trunk, palms, soles.

(caused by Rickettsia rickettsii)

339
Q

Rickettsiae features

A
  • obligate intracellular

- need CoA and NAD+ because they cannot synthesize ATP

340
Q

Classic Triad of Rocky Mountain Spotted Fever

A
  • headache
  • fever
  • rash
341
Q

Typhus rash starts…

A

centrally and then spreads out, sparing the palms and soles.

342
Q

Ehrlichiosis

A
  • monocytes with moulae (berry-like inclusions) in cytoplasm

- rash is rare

343
Q

Anaplasmosis

A
  • granulocytes with morulae in cytoplasm

- rash is rare

344
Q

Q fever

A
  • presents as pneumonia
  • rash is rare
  • no arthropod vector
345
Q

Chlamydiae features

A
  • cannot make their own ATP
  • obligate intracellular
  • cause mucosal infections
346
Q

2 forms of Chlamydiae:

A
  1. Elementary body (small, dense): infectious, enters cell via endoctyosis and transforms into reticulate body
  2. Reticulate body: replicates in cell by fission; reorganizes into elementary body
347
Q

Chlaymdia trachomatis causes…

A

reactive arthritis (Reiter syndrome), follicular conjunctivitis, urethritis and PID.

348
Q

C. pneumoniae and C. psittaci cause…

A

atypical pneumonia; transmitted by aerosol.

349
Q

Treatment for Chlamydiae

A

Aziththromycin or Doxycycline

350
Q

The chlamydial cell wall is unusal in that it…

A

lack muramic acid.

351
Q

Chlamydia trachomatis types A, B and C

A

chronic infection, cause blindness due to follicular conjunctivitis in Africa

352
Q

Chlamydia trachomatis types D-K

A

urethritis/PID, ectopic pregnancy, neonatal pneumonia (staccato cough), neonatal conjunctivitis

353
Q

Chlamydia trachomatis typse L1, L2 and L3

A

Lymphogranuloma venereum - small, painless ulcers on genitals; swollen, painful inguinal LNs that ulcerate

354
Q

Mycoplasma pneumoniae is the classic cause of…

A

atypical “walking” pneumonia (insidious onset, HA, nonproductive cough, patchy or diffuse interstital infiltrate).

355
Q

Atypical pneumonia findings

A
  • X-ray looks worse than pt
  • high titer of cold agglutinins (IgM)
  • grown on Eaton agar
  • more common in pts less than 30
  • frequent outbreaks in miliatry recruits and prisons
356
Q

Treatment for Mycoplasma pneumoniae

A
  • macrolide
  • doxycycline
  • fluoroquinolone
357
Q

Mycoplasma pneumoniae features

A
  • no cell wall (thus, penicillin is ineffective)
  • not seen on gram stain
  • bacterial membrane contains sterols for stability

Step 1 Exam (32 decks)

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