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USMLE > Microbiology Superset RidEZ - Part 1 > Flashcards

Microbiology Superset RidEZ - Part 1 Flashcards

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USMLE® Step 1 flashcards
1
Q

Function and chemical composition of bacterial structure: Peptidoglycan

A

Function:

  1. Rigid support
  2. Protects against osmotic pressure

Chemical composition:
Sugar backbone with cross-linked peptide side chains

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2
Q

Function and chemical composition of bacterial structure: Cell wall/cell membrane

A

Gram positives only

Function: Major surface antigen

Chemical composition: Teichoic acid, which induces TNF and IL-1

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3
Q

Function and chemical composition of bacterial structure: Outer membrane

A

Gram negatives only

Function: Site of endotoxin (lipopolysaccharide) and major surface antigen

Chemical composition: Lipid A induces TNF and IL-1, and polysaccharide is the antigen

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4
Q

Function and chemical composition of bacterial structure: Plasma membrane

A

Function: Site of oxidative and transport enzymes

Chemical composition: Lipoprotein bilayer

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5
Q

Function and chemical composition of bacterial structure: Ribosome

A

Function: Protein synthesis

Chemical composition: 50S and 30S subunits

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6
Q

Function and chemical composition of bacterial structure: Periplasm

A

Function: Space between the cytoplasmic membrane and outer membrane in gram-negative bacteria

Chemical composition: Contains many hydrolytic enzymes, including beta-lactamases

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7
Q

Function and chemical composition of bacterial structure: Capsule

A

Function: Protects against phagocytosis

Chemical composition: Polysaccharide (except Bacillus anthracis which contains D-glutamate)

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8
Q

Function and chemical composition of bacterial structure: Pilus/fimbria

A

Function: Mediates adherence of bacteria to cell surface; sex pilus forms attachment between 2 bacteria during conjugation

Chemical composition: Glycoprotein

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9
Q

Function and chemical composition of bacterial structure: Flagellum

A

Function: Motility

Chemical composition: Protein

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10
Q

Function and chemical composition of bacterial structure: Spore

A

Function: Provides resistance to dehydration, heat, and chemicals

Chemical composition: Keratin-like coat and dipicolinic acid

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11
Q

Function and chemical composition of bacterial structure: Plasmid

A

Function: Contains a variety of genes for antibiotic resistance, enzymes, and toxins

Chemical composition: DNA

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12
Q

Function and chemical composition of bacterial structure: Glycocalyx

A

Function: Mediates adherence to surfaces, especially foreign surfaces (eg indwelling catheters)

Chemical composition: Polysaccharide

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13
Q

Function of this structure: IgA proteases

A

Function: Allow some organisms to colonize mucosal surfaces

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14
Q

Which bacteria have IgA proteases?

A
  1. Streptococcus pneumoniae
  2. Neisseria meningitidis
  3. Neisseria gonorrheae
  4. Hemophilus influenzae
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15
Q

Which bacterial substances induce cytokines, and which are they?

A

Cytokines induced:

  1. IL-1
  2. TNF

Gram positive inducer: Teichoic acid

Gram negative inducer: Lipopolysaccharide (Endoxtoxin)

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16
Q

What does the capsule of Bacillus anthracis consist of?

A

D-glutamate

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17
Q

What bacterial structure contains D-glutamate?

A

Capsule of Bacillus anthracis

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18
Q

What are the main differences between gram negative and gram positive organisms?

A

Peptidoglycan cell wall: Gram positive has thick. Gram negative has thin.

Flagellar basal body rings: Gram positive has two. Gram negative has four.

Outer antigen: Gram positive: Teichoic acid. Gram negative: Lipidpolysaccharide

Periplasmic space: Gram positive does not have. Gram negative has.

Porin channel: Gram positive does not have. Gram negative has.

Lysozyme and penicillin attack: Gram positive are sensitive. Gram negative are resistant.

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19
Q

What bacteria do not gram stain well?

A

Mnemonic: These Rascals May Microscopically Lack Color

  1. Treponema
  2. Rickettsia
  3. Mycobacteria
  4. Mycoplasma
  5. Legionella pneumophila
  6. Chlamydia
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20
Q

Why does the following bug not gram stain well?: Treponema

A

Too thin to be visualized

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21
Q

Why does the following bug not gram stain well?: Rickettsia

A

Intracellular parasite

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22
Q

Why does the following bug not gram stain well?: Mycobacteria

A

high-lipid-content cell wall

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23
Q

Why does the following bug not gram stain well?: Mycoplasma

A

No cell wall

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24
Q

Why does the following bug not gram stain well?: Legionella pneumophila

A

Primarily intracellular

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25
Q

Why does the following bug not gram stain well?: Chlamydia

A

Intracellular parasite which lacks muramic acid in cell wall

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26
Q

How is the following bug visualized?: Treponema

A
  1. Darkfield microscopy
  2. Fluorescent antibody staining
  3. silver stain
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27
Q

Why does the following bug not gram stain well?: Mycobacteria

A

Acid fast for high lipid content cell wall

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28
Q

What are the stages of bacterial growth and what are their relative lengths?

A
  1. Lag phase: x
  2. Log phase: 1.5x
  3. Stationary phase: 2.5x
  4. Death phase: 4x
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29
Q

What happens in the following phase of bacterial growth, and where does it fall in the order?: Lag

A

1st phase: Metabolic activity without division

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30
Q

What happens in the following phase of bacterial growth, and where does it fall in the order?: Log

A

2nd phase: Rapid cell division

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31
Q

What happens in the following phase of bacterial growth, and where does it fall in the order?: Stationary

A

3rd phase: Nutrient depletion slows growth

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32
Q

What happens in the following phase of bacterial growth, and where does it fall in the order?: Death

A

4th phase: Prolonged nutrient depletion and buildup of waste products leads to death

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33
Q

Bacterial endotoxins and exotoxins: Source?

A

Exotoxin: Certain species of gram positive and gram negative bacteria

Endotoxin: Cell wall of most gram-negative bacteria

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34
Q

Bacterial endotoxins and exotoxins: Secreted from cell?

A

Exotoxin: Yes

Endotoxin: No

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35
Q

Bacterial endotoxins and exotoxins: Chemistry

A

Exotoxin: Polypeptide

Endotoxin: Lipopolysaccharide

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36
Q

Bacterial endotoxins and exotoxins: Location of genes

A

Exotoxin: Plasmid or bacteriophage

Endotoxin: Bacterial chromosome

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37
Q

Bacterial endotoxins and exotoxins: Toxicity (fatal dosage)

A

Exotoxin: High (fatal dose on the order of 1 microgram)

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

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38
Q

Bacterial endotoxins and exotoxins: Clinical effects

A

Exotoxin: Toxin specific

Endotoxin: Fever and shock

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39
Q

Bacterial endotoxins and exotoxins: Mode of action

A

Exotoxin: Toxin specific

Endotoxin: Includes TNF and IL-1

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40
Q

Bacterial endotoxins and exotoxins: Antigenicity

A

Exotoxin: Induces high-titer antibodies called antitoxins

Endotoxin: Poorly antigenic

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41
Q

Bacterial endotoxins and exotoxins: Vaccines

A

Exotoxin: Toxoids used as vaccines

Endotoxin: No toxoids formed and no vaccine available

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42
Q

Bacterial endotoxins and exotoxins: Heat stability

A

Exotoxin: Destroyed rapidly at 60 degrees celsius (except Staphylococcal enterotoxin)

Endotoxin: Stable at 100 degrees celsius for 1 hour

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43
Q

Bacterial endotoxins and exotoxins: Typical diseases

A

Exotoxin: Tetanus, botulism, diphtheria

Endotoxin: Meningococcemia, sepsis by gram negative rods

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44
Q

Mechanism of superantigens

A
  1. Bind directly to MHC II and T cell receptor
  2. Large numbers of T cells are activated.
  3. Stimulates release of IFN-gamma and IL-2
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45
Q

Mechanism of ADP ribosylating A-B toxins

A

Interfere with host cell function

  1. B (binding) component binds to a receptor on surface of host cell.
  2. The toxin is endocytosed.
  3. A (active) component attaches an ADP-ribosyl to a host cell protein.
  4. That protein’s function is altered.
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46
Q

List of bugs that release superantigens

A
  1. Staphylococcus aureus

2. Streptococcus pyogenes

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47
Q

List of bugs that release ADP ribosylating A-B toxins

A
  1. Corynebacterium diphtheriae
  2. Vibrio cholerae
  3. E. coli
  4. Bordetella pertussis
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48
Q

What to know about exotoxins released by Staphylococcus aureus

A

Superantigens

  1. TSST-1 causes toxic shock syndrome (fever, rash, shock).
  2. Enterotoxins cause food poisoning.
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49
Q

What to know about exotoxins released by Streptococcus pyogenes

A

Scarlet fever (superantigen)

  1. Erythrogenic
  2. Causes toxic shock-like syndrome

Streptolysin O (hemolysin). The antigen for ASO antibody is found in rheumatic fever

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50
Q

What to know about exotoxins released by Corynebacterium diphtheriae

A

ADP ribosylating A-B toxin (similar to Pseudomonas exotoxin A)

Encoded by beta-prophage

Disease: Pseudomembranous pharyngitis (grayish-white membrane) with lymphadenopathy

Mechanism:
Inactivates elongation 
factor 2 (EF-2)
Mnemonic: ABCDEFG
ADP ribosylation
Beta-prophage
Corynebacterium
Diphtheriae
Elongation Factor 2
Granules (metachromatic)
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51
Q

What to know about exotoxins released by Vibrio cholerae

A
  1. A-B toxin ADP ribosylates Gs protein thus:
  2. Permanently activates Gs protein
  3. Constant stimulation of adenylyl cyclase which:
  4. Increases pumping of Cl into gut
  5. H2O follows it
  6. Leads to rice water diarrhea
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52
Q

What to know about exotoxins released by E. coli

A

E.coli 0157:H7 produces Shiga toxin.

ADP ribosylating A-B toxins

Heat-labile: Permanent activation of adenylyl cyclase (cholera-like mechanism) leading to watery diarrhea

Heat-stabile: Stimulates guanylate cyclase

Mnemonic: Labile like the Air, Stabile like the Ground.

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53
Q

What to know about exotoxins released by Bordetella pertussis

A
  1. ADP ribosylating A-B toxin
  2. Permanently disables Gi
  3. Constant stimulation of adenylate cyclase
  4. Causes whooping cough
  5. Also inhibits chemokine receptor causing lymphocytosis
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54
Q

What to know about exotoxins released by Clostridium perfringens

A

alpha toxin (aka lecithinase) causes:

  1. gas gangrene
  2. myonecrosis
  3. hemolysis (See double zone of hemolysis on blood agar.)

PERFringens PERForates a gangrenous leg.

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55
Q

What to know about exotoxin released by Clostridium botulinum

A

Properties:

  1. Preformed
  2. Heat-labile

Mechanism:
Blocks the release of acetylcholine causing:
1. anticholinergic symptoms
2. CNS paralysis (especially cranial nerves)
3. Floppy baby syndrome

BOTulinum is from bad BOTtles of food and honey and sausage (causes flaccid paralysis)

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56
Q

What to know about exotoxins released by Clostridium tetani

A

Blocks the release of inhibitory neurotransmitter glycine from Renshaw cells in the spinal cord. Causes “lockjaw”

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57
Q

What to know about exotoxins released by Bacillus anthracis

A

1 toxin in the toxin complex is edema factor, an adenylate cyclase

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58
Q

What to know about exotoxins released by Shigella

A

Shiga toxin (also produced by E.coli 0157:H7).

Cleaves host cell rRNA. Also enhances cytokine release causing hemolytic uremic syndrome.

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59
Q

Endotoxin: What is it and where is it found?

A

Lipopolysaccharide found in the outer membrane of gram-negative bacteria. Heat stable.

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60
Q

Endotoxin: What does it activate and what do they release?

A
  1. Macrophages (IL-1, TNF, Nitric oxide)
  2. Alternative complement pathway (C3a, C5a)
  3. Hageman factor (Coagulation cascade)
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61
Q

What mediators are released when endotoxin activates macrophages, and what do they do?

A
  1. IL-1: Fever
  2. TNF: Fever and Hemorrhagic tissue necrosis
  3. Nitric Oxide: Hypotension (shock)
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62
Q

What mediators are released when endotoxin activates the alternative complement cascade, and what do they do?

A
  1. C3a: Hypotension and edema

2. C5a: Neutrophil chemotaxis

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63
Q

What mediators are released when endotoxin activates Hageman factor, and what do they do?

A

Coagulation cascade: Disseminated intravascular coagulopathy

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64
Q

What method is used to differentiate Neisseria?

A

Sugar fermentation

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65
Q

What do meningococci ferment?

A

MeninGococci ferment Maltose and Glucose

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66
Q

What do gonococci ferment?

A

Gonococci ferments Glucose

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67
Q

What are the pigment producing bacteria and what pigments do they produce?

A

Staphylococcus aureus: Yellow pigment (Aureus means gold in Latin)

Pseudomonas aeruginosa: blue-green pigment

Serratia marcescens: red pigment (think red maraschino cherries)

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68
Q

Special culture requirements for: Hemophilus influenzae

A

Chocolate agar with factors V (NAD) and X (hematin)

Mnemonic: When a child has “flu” mom goes to five (V) and dime (X) to buy some chocolate.

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69
Q

Special culture requirements for: Neisseria gonorrhoeae

A

Thayer-Martin media

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70
Q

Special culture requirements for: Bordetella pertussis

A

Bordet-Gengou (potato) agar

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71
Q

Special culture requirements for: M. tuberculosis

A

Lowenstein-Jensen agar

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72
Q

Special culture requirements for: Lactose-fermenting enteric bacteria

A

Pink colonies on MacConkey’s agar

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73
Q

Special culture requirements for: Legionella

A

Charcoal yeast extract agar buffered with increased iron and cysteine

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74
Q

Special culture requirements for: Fungi

A

Sabouraud’s agar

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75
Q

What microbes can be stained with: Congo red

A

Amyloid. Apple-green birefringence in polarized light (because of beta-pleated sheets)

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76
Q

What microbes can be stained with: Giemsa’s

A
  1. Borrelia
  2. Plasmodium
  3. Trypanosomes
  4. Chlamydia
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77
Q

What microbes can be stained with: periodic acid-Schiff (PAS)

A

Glycogen and mucopolysaccharides. Used to diagnose Whipple’s disease

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78
Q

What microbes can be stained with: Ziehl-Neelsen

A

Acid-fast bacteria.

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79
Q

What microbes can be stained with: India ink

A

Cryptococcus neoformans

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80
Q

What microbes can be stained with: Silver stain

A
  1. Fungi
  2. PCP (Pneumocystis Pneumonia)
  3. Legionella
  4. Treponema
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81
Q

For the following genetic transfer procedure, explain the process: Conjugation

A

Direct cell to cell DNA transfer

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82
Q

For the following genetic transfer procedure, explain the process: Transduction

A

Phage-mediated cell to cell DNA transfer

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83
Q

For the following genetic transfer procedure, explain the process: Transformation

A

Purified DNA taken up by a cell

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84
Q

For the following genetic transfer procedure, explain the processd: Transposition

A

DNA transfer to same or another chromosome or plasmid WITHIN a cell

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85
Q

For the following genetic transfer procedure, give the types of cells involved: Conjugation

A

Prokaryotic

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86
Q

For the following genetic transfer procedure, give the types of cells involved: Transduction

A

Prokaryotic

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87
Q

For the following genetic transfer procedure, give the types of cells involved: Transformation

A

Prokaryotic or eukaryotic

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88
Q

For the following genetic transfer procedure, give the types of cells involved: Transposition

A

Prokaryotic or eukaryotic

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89
Q

For the following genetic transfer procedure, give the nature of DNA transferred: Conjugation

A

Chromosomal or plasmid

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90
Q

For the following genetic transfer procedure, give the nature of DNA transferred: Transduction

A

Generalized transduction: Any gene

Specialized transduction: Only certain genes

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91
Q

For the following genetic transfer procedure, give the nature of DNA transferred: Transformation

A

Any DNA

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92
Q

For the following genetic transfer procedure, give the nature of DNA transferred: Transposition

A

DNA sequences “jumping genes”

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93
Q

What is lysogeny?

A

When the genetic code for a bacterial toxin is encoded in a lysogenic phage.

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94
Q

Name 4 lysogenic toxins.

A

BCDE

  1. Botulinum
  2. Cholera
  3. Diphtheria
  4. Erythrogenic toxin of Streptococcus Pyogenes
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95
Q

List four obligate aerobes.

A

Nocardia, Pseudomonas aeruginosa, Mycobacterium tuberculosis, Bacillus

Mnemonic: Nagging Pests Must Breathe

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96
Q

Where in the lung does M. tuberculosis prefer, and why?

A

Apices of the lung, as they have the highest PO2.

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5
Perfectly
97
Q

What conditions occur concurrently with P. Aeruginosa infection?

A
  1. Burn wounds
  2. Nosocomial pneumonia
  3. Pneumonias in Cystic Fibrosis patients
98
Q

List 3 obligate anaerobes

A

Clostridium, Bacteroides, and Actinomyces

99
Q

What enzymes do obligate anaerobes lack?

A

Catalase (aka glutathione peroxidase)

AND/OR

Superoxide dismutase (converts O2-radical[ie superoxide] to H2O2)

100
Q

Why are anaerobes foul-smelling?

A

They produce short-chain fatty acids.

101
Q

What do anaerobes produce in tissue?

A

CO2 and H2 gases

102
Q

Where are anaerobes normal flora?

A
  1. GI tract

2. Between teeth and gums

103
Q

What antibiotics are particularly ineffective against anaerobes?

A

AminO2glycosides, as they require O2 to enter the bacterial cell.

104
Q

List the obligate intracellular bacteria.

A

Rickettsia and Chlamydia.

Mnemonic: Stay inside (cells) when it is Really Cold

105
Q

What is the defining characteristic of obligate intracellular bacteria.

A

Can’t make their own ATP.

106
Q

List the facultative intracellular bacteria.

A

Mnemonic: Some Nasty Bugs May Live FacultativeLY

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

OR

Mnemonic: My Liege, Your Niece Lists Frank, Bruce and Sam.

Mycobacterium, Leigonella, Yersinia, Neisseria, Listeria, Francisella, Brucella, Salmonella.

107
Q

List four major examples of encapsulated bacteria

A
  1. Streptococcus pneumoniae
  2. Hemophilus influenzae (especially B serotype)
  3. Neisseria meningitidis
  4. Klebsiella pneumoniae
108
Q

What does a positive quellung reaction indicate?

A

Positive quellung: If encapsulated bug is present, capsule swells when specific anticapsular antisera are added.

Mnemonic: Quellung = capsular “swellung”

109
Q

In which vaccines does the capsule serve as an antigen?

A

Pneumovax, H influenzae B, Meningococcal vaccines

110
Q

What does conjugation with protein do to vaccines that have a capsular antigen?

A

Increases the immunogenicity and T-cell dependent responce.

111
Q

Which bacteria form spores?

A

Gram positive soil bugs (eg Bacillus anthracis, Clostridium perfringens, Clostridium tetani)

112
Q

How can one destroy spores?

A

Autoclave (as is done to surgical equipment)

113
Q

Which bacteria are alpha hemolytic?

A

Streptococcus (all catalase-negative)

If optochin sensitive, bile soluble, or quellung positive: Streptococcus Pneumoniae

If optochin resistant, bile insoluble, or quellung negative: Streptococcus Viridans (eg S. Mutans)

114
Q

Which bacteria are beta-hemolytic?

A

Rods:
Listeria monocytogenes

Cocci:
If catalase positive and coagulase positive: Staphylococcus Aureus

If catalase negative, Streptococcus.
Then, if bacitracin sensitive, S. pyogenes. If bacitracin resistant, S. agalactiae.

115
Q

What are the important points about Listeria monocytogenes?

A
  1. Tumbling motility
  2. Meningitis in newborns
  3. Unpasteurized milk
116
Q

Gram positive: Which are catalase positive and which are catalase negative?

A

Positive: Staph
Negative: Strep

117
Q

Gram positive: Which are catalase positive bacteria make coagulase?

A

Staph aureus does.

Staph epidermidis and saprophyticus do not.

118
Q

What is Protein A?

A

Virulence factor of Staphylococcus Aureus. Binds Fc-IgG, inhibiting complement fixation and phagocytosis.

119
Q

What disease states does Staphylococcus Aureus cause?

A

Inflammatory:

  1. Skin infections
  2. Organ abscesses (acute bacterial endocarditis, osteomyelitis)
  3. Pneumonia

Toxin-mediated:

  1. Toxic shock syndrome (TSST-1)
  2. Scalded skin syndrome (exfoliative toxin)
  3. Rapid-onset food poisoning (ingestion of preformed enterotoxin)
120
Q

What disease states does Streptococcus Pyogenes cause?

A

Pyogenic

  1. Pharyngitis
  2. Cellulitis
  3. Impetigo

Toxigenic

  1. Scarlet fever
  2. Toxic shock syndrome

Immunologic

  1. Rheumatic fever
  2. Acute glomerulonephritis
121
Q

What are two sequelae of Streptococcus Pyogenes pharyngitis?

A

Rheumatic fever and acute glomerulonephritis

Mnemonoic: PHaryngitis gives you rheumatic PHever and glomerulonePHritis

122
Q

Which antibody enhances host defenses against Streptococcus Pyogenes?

A

Antibody to M protein

123
Q

Antibody to M protein enhances host defenses against what?

A

Streptococcus Pyogenes

124
Q

What does ASO titer detect?

A

Recent S. Pyogenes infection

125
Q

How can one detect recent S. Pyogenes infection?

A

ASO titer

126
Q

What are the signs and symptoms of rheumatic fever?

A
  1. Subcutaneous nodules
  2. Polyarthritis
  3. Erythema marginatum
  4. Chorea
  5. Carditis (bacterial endocarditis)

Mnemonic: No “rheum” for SPECCulation

127
Q

What is streptococcus pneumoniae the most common cause of?

A
  1. Meningitis
  2. Otitis media (in children)
  3. Pneumonia
  4. Sinusitis

S. pneumoniae MOPS are Most OPtochin Sensitive

128
Q

What is the most common cause of meningitis?

A

Streptococcus pneumoniae

129
Q

What is the most common cause of otitis media?

A

Streptococcus pneumoniae

130
Q

What is the most common cause of pneumonia?

A

Streptococcus pneumoniae

131
Q

What is the most common cause of sinusitis?

A

Streptococcus pneumoniae

132
Q

What is indicated by “rusty” sputum?

A

Streptococcus pneumoniae infection

133
Q

What are common associations with Pneumococcus?

A

Streptococcus Pneumoniae

  1. “Rusty” sputum
  2. Sepsis in sickle cell anemia 3. splenectomy
134
Q

What does sepsin in sickle cell anemia indicate?

A

Streptococcus pneumoniae

135
Q

What do Group B streptococci cause?

A

B for Baby

  1. Pneumonia
  2. Meningitis
  3. Sepsis
136
Q

3 most common causes of meningitis in infants younger than 3 months of age

A
  1. E. coli
  2. Listeria monocytogenes
  3. Group B streptococcus
137
Q

How do infants with meningitis present?

A
  1. Fever
  2. Vomiting
  3. Poor feeding
  4. Irritability
138
Q

Name the Lancefield Group D bacterial categories and examples of each.

A

Enterococci:

  1. Enterococcus faecalis
  2. Enterococcus faecium

Non-enterococci

  1. Streptococcus bovis
  2. Streptococcus equinus
139
Q

What is Streptococcus bovis infection a sign of?

A

Colonic malignancy

140
Q

What kind of hemolysis do enterococci cause?

A

Variable

CMMRS says alpha; FA says variable and gamma

141
Q

What drug resistances do the enterococci show?

A
  1. Penicillin G
  2. Ampicillin
  3. Vancomycin
142
Q

What is Lancefield grouping determined by?

A

Differences in the C carbohydrate on the bacterial cell wall

143
Q

Which Group D bacteria are hardier?

A

Enterococci are hardier than nonenterococci. They can grow in 6.5% NaCl

144
Q

A colony of bacteria grows in 6.5% NaCl. What is it?

A

Enterococcus

145
Q

What disease states/problems does Staphylococcus epidermidis cause?

A

Infection of prosthetic devices and catheters. Contaminates blood cultures.

146
Q

How is Streptococcus Viridans characterized?

A
  1. Alpha hemolysis
  2. Optochin resistant
  3. Normal mouth flora

(Mnemonic: Viridans lives in the mouth because it is not afraid of-the-chin)

147
Q

Where is Strep. Viridans part of the normal flora?

A

Oropharynx

148
Q

What disease states/problems does Streptococcus Viridans cause?

A
  1. Dental caries (Streptococcus mutans)

2. Subacute Bacterial endocarditis (Streptococcus Sanguis)

149
Q

What disease states does Streptococcus mutans cause?

A

Dental caries

150
Q

What disease states does Streptococcus sanguis cause?

A

Subacute bacterial endocarditis

Sanguis = blood, lots of blood in the heart.

151
Q

How are clostridia characterized?

A
  1. Gram positive rods
  2. Spore forming
  3. Obligate anaerobes
152
Q

What disease state does Clostridium difficile cause, and what is its mechanism?

A

Disease state: pseudomembranous colitis secondary to clindamycin or ampicillin use. (Mnemonic: DIfficile causes DIarrhea)

Mechanism:

  1. Antibiotic kills off protective flora
  2. C. difficile takes hold and proliferates
  3. Produces cytotoxin, an enterotoxin.
  4. Cytotoxin kills enterocytes.
153
Q

Treatment for C. difficile infection

A

Metronidazole

154
Q

Lab diagnosis basis for Cornyebacterium diphtheriae

A

Gram positive rods with metachromatic granules, grown on tellurite agar (aka Loffler’s coagulated serum medium)

155
Q

How is Bacillus anthracis characterized?

A
  1. Gram positive rod
  2. Spore forming
  3. Protein capsule
156
Q

Which bacteria have a protein capsule?

A

Bacillus anthracis (the only one)

157
Q

What are the mechanisms of anthrax infection and disease?

A
  1. Non-inhalation contact with bacillus anthracis
  2. Formation of malignant pustule (painless ulcer)
  3. Progression to bacteremia
  4. Death
  5. Inhalation of spores
  6. Development of flulike symptoms that rapidly progress to fever, pulmonary hemorrhage and shock.
158
Q

What organism: Development of flulike symptoms followed by fever, pulmonary hemorrhage and shock.

A

Inhalation anthrax: Bacillus anthracis

159
Q

What do skin lesions in anthrax look like?

A

Vesicular papules covered by black eschar

160
Q

What is Woolsorter’s disease

A

Inhalation of Bacillus anthracis spores from contaminated wool

161
Q

What organism: Gram-positive rods forming long branching filaments resembling fungi

A

Actinomyces israelii or Nocardia asteroides

162
Q

What organism: Oral or facial abscesses with yellow granules in sinus tracts

A

Actinomyces israelii

163
Q

What disease state does Actinomyces israelii cause?

A

Oral or facial abscesses with yellow granules draining out skin through sinus tracts

164
Q

How is Actinomyces israelii characterised?

A

Gram-positive anaerobic rods forming long branching filaments resembling fungi (Nocardia also has this description)

Causes oral or facial abscesses with yellow granules

165
Q

How is Nocardia asteroides characterized?

A

Gram-positive (weakly acid fast) rods forming long branching filaments resembling fungi (Actinomyces also has this description)

166
Q

What disease state does Nocardia asteroides cause?

A

Pulmonary infection in immunocompromised patients

167
Q

What is the treatment for Actinomyces israelii?

A

Penicillin

Mnemonic: SNAP (Sulfa for Nocardia; Acintomyces use Penicillin)

168
Q

What is the treatment for Nocardia Asteroides?

A

Sulfonamides

Mnemonic: SNAP (Sulfa for Nocardia; Acintomyces use Penicillin)

169
Q

Penicillin G and Gram negative bugs

A

Gram-negatives are resistant to benzyl penicillin G. The gram-negative outer membrane layer inhibits entry of penicillin G and vancomycin.

May be susceptible to penicillin derivatives such as ampicillin.

170
Q

What bacteria genus can live in neutrophils?

A

Neisseria

171
Q

How are neisseria characterized?

A

Gram-negative cocci that resemble paired coffee beans

172
Q

Gonococcus and meningococcus: Polysaccharide capsule

A

G: No
M: Yes

173
Q

Gonococcus and meningococcus: Maltose fermentation

A

G: No (Gonococcus ferments Glucose)
M: Yes (MeninGococcus ferments Maltose and Glucose)

174
Q

Gonococcus and meningococcus: Vaccine availability

A

G: No
M: Yes

175
Q

What disease states does Gonococcus cause?

A
  1. Gonorrhea
  2. septic arthritis
  3. neonatal conjunctivitis
  4. PID
176
Q

What disease states does Meningococcus cause?

A
  1. Meningococcemia
  2. Meningitis
  3. Waterhouse-Friderichsen syndrome
177
Q

What is Waterhouse-Friderichsen syndrome?

A

massive, usually bilateral, hemorrhage into the adrenal glands caused by fulminant meningococcemia.

Characterised by overwhelming bacterial infection, rapidly progressive hypotension leading to shock, disseminated intravascular coagulation (DIC) with widespread purpura, particularly of the skin, and rapidly developing adrenocortical insufficiency associated with massive bilateral adrenal hemorrhage.

178
Q

What disease states does Haemophilus Influenzae cause?

A

HaEMOPhilus causes

  1. Epiglottitis
  2. Meningitis
  3. Otitis media
  4. Pneumonia

Does not cause flu (that’s a virus)!

179
Q

How is Haemophilus Influenzae characterized?

A

Small gram-negative coccoid rod.

180
Q

How is Haemophilus Influenzae transmitted?

A

Aerosol

181
Q

Which type of Haemophilus Influenzae is most pathogenic?

A

capsular type B

182
Q

Treatment for Haemophilus Influenzae meningitis

A

Ceftriaxone

183
Q

Prophylaxis for Hemophilus Influenzae

A

Vaccine: Type B polysaccharide conjugated to diphtheria toxoid or other protein. Given between 2 and 18 months of age.

Close contacts of infected person: Rifampin

184
Q

How are enterobacteriaceae characterized?

A

Gram negative diverse group

Mnemonic: COFFEe

  1. Capsule (K [kapsular] antigen related to virulence of the bug)
  2. O antigen (somatic antigen which is the polysaccharide of endotoxin)
  3. Flagella (H antigen found in motile species)
  4. Ferment glucose
  5. Enterobacteriaceae (woo!)
185
Q

Enterobacteriaceae list

A
  1. Escherichia coli
  2. Klebsiella pneumoniae
  3. Proteus mirablis
  4. Enterobacter sp.
  5. Serratia
  6. Shigella
  7. Salmonella
  8. Yersinia enterocolitica
186
Q

What disease states does Klebsiella cause?

A
  1. Pneumonia in alcoholics and diabetics (In the name: Klebsiella pneumoniae)
  2. Nosocomial UTIs (large mucoid capsule and viscous colonies)

Mnemonic: AAA (Aspiration pneumonia, Abscess in lungs, Alcoholics)

187
Q

Signs and symptoms of Klebsiella infection

A
  1. Red currant jelly sputum

2. Abscess in lungs

188
Q

Orange sputum: What bugs?

A
  1. Pneumococcus

2. Klebsiella (or described as “red currant jelly sputum”)

189
Q

Red currant jelly sputum: What bug?

A

Klebsiella

190
Q

Lactose-fermenting enteric bacteria

A

Mnemonic: Test lactose with MacConKEE’S.

  1. Citrobacter
  2. Klebsiella
  3. E. coli
  4. Enterobacter
  5. Serratia
191
Q

Salmonella vs. Shigella: Lactose fermenter?

A

Neither

192
Q

Salmonella vs. Shigella: Motile

A

Both (Though, the evidence that shigella is motile is recent.)

Can invade and disseminate hematogenously.

193
Q

Salmonella vs. Shigella: Animal reservoir

A

Salmonella: Yes
Shigella: No

194
Q

Shigella transmission

A

4 Fs:

  1. Food
  2. Fingers
  3. Feces
  4. Flies
195
Q

Salmonella vs. Shigella: Virulence

A

Salmonella: 100,000 organisms
Shigella: 10 organisms

196
Q

True or False: Salmonellosis symptoms may be prolonged with antibiotic treatments

A

True

197
Q

What type of inflammatory response is seen in Salmonellosis?

A

Monocytes

198
Q

Transmission of Yersinia enterocolitica

A
  1. Pet feces (eg puppies)

2. Contaminated milk or pork

199
Q

Yersinia enterocolitica infection: Clinical presentation

A
  1. Outbreaks are common in day-care centers

2. Can mimic Crohn’s or appendicitis

200
Q

What bug causes contamination of this food: Seafood

A

Vibrio:

  1. parahaemolyticus
  2. vulnificus
201
Q

What bug causes contamination of this food: Reheated rice

A

Bacillus cereus

Mnem: “Food poisoning from reheated rice? Be serious!”

202
Q

What bug causes contamination of this food: Meat

A
  1. Staphylococcus Aureus (starts quickly and ends quickly)
  2. Salmonella (including poultry)
  3. Clostridium perfringens (reheated meat dishes)
  4. Vibrio (parahaemolyticus, vulnificus) (in seafood)
  5. E. coli O157:H7 (undercooked meat)
  6. Clostridium Botulinum (in sausage)
203
Q

What bug causes contamination of this food: Mayonnaise

A

Staphylococcus Aureus (starts quickly and ends quickly)

204
Q

What bug causes contamination of this food: Custard

A

Staphylococcus Aureus (starts quickly and ends quickly)

205
Q

What bug causes contamination of this food: Reheated meat

A

Clostridium perfringens

Mnem: “Food poisoning from reheated meat? Clostridium perfringens!”

206
Q

What bug causes contamination of this food: Bulging cans

A

Clostridium botulinum

BOTulinum is from bad BOTtles of food and honey and sausage

207
Q

What bug causes contamination of this food: Sausage

A

Clostridium botulinum

BOTulinum is from bad BOTtles of food and honey and sausage

208
Q

What bug causes contamination of this food: Honey

A

Clostridium botulinum

BOTulinum is from bad BOTtles of food and honey and sausage

209
Q

What bug causes contamination of this food: Poultry

A

Salmonella

210
Q

What bug causes contamination of this food: Eggs

A

Salmonella

211
Q

Bloody or watery diarrhea: Vibrio parahaemolyticus

A

Either bloody or watery

212
Q

Bloody or watery diarrhea: Campylobacter

A

Bloody

213
Q

Bloody or watery diarrhea: Salmonella

A

Bloody

214
Q

Bloody or watery diarrhea: Shigella

A

Bloody

215
Q

Bloody or watery diarrhea: Enterohemorrhagic E. coli

A

Bloody

216
Q

Bloody or watery diarrhea: Enteroinvasive E. coli

A

Bloody

217
Q

Bloody or watery diarrhea: Yersinia enterocolitica

A

Bloody

218
Q

Bloody or watery diarrhea: C. difficile

A

Bloody

219
Q

Bloody or watery diarrhea: Entamoeba histolytica

A

Bloody

220
Q

Bloody or watery diarrhea: Enterotoxigenic E. coli

A

Watery

221
Q

Bloody or watery diarrhea: Vibrio cholerae

A

Watery

222
Q

Bloody or watery diarrhea: C. perfringens

A

Watery

223
Q

Bloody or watery diarrhea: Protozoa

A

Watery

224
Q

Bloody or watery diarrhea: Viruses

A

Watery

225
Q

Diagnosis: Bloody diarrhea with oxidase-positive comma or S-shaped organisms grown at 42 degrees celsius

A

Campylobacter

226
Q

Diagnosis: Bloody diarrhea with motile, lactose negative gram negative bugs

A

Salmonella or Shigella

Shigella have a very low ID50 and cause dysentery

227
Q

Diagnosis: Bloody diarrhea with schistocytes and azotemia

A

Enterohemorrhagic E coli (eg O157:H7)

Caused by shiga-like toxin

228
Q

Diagnosis: Bloody diarrhea with hemolytic uremic syndrome

A

Enterohemorrhagic E coli (eg O157:H7)

Caused by shiga-like toxin

229
Q

Diagnosis: Bloody diarrhea with pathologic section revealing bacteria invading colonic mucosa

A

Enteroinvasive E. coli

230
Q

Diagnosis: Bloody diarrhea with symptoms of appendicitis

A

Yersinia enterocolitica

231
Q

Diagnosis: Bloody diarrhea in a day care center

A

Yersinia enterocolitica

232
Q

Diagnosis: Bloody diarrhea with pseudomembranous colitis

A

Clostridium dificile

233
Q

Diagnosis: Bloody diarrhea with protozoans

A

Entamoeba histolytica

234
Q

Diagnosis: Watery diarrhea in someone who just visited Mexico

A

Enterotoxigenic E coli (no preformed toxin)

235
Q

Diagnosis: Watery diarrhea with comma-shaped organisms

A

Vibrio cholerae

236
Q

Diagnosis: Watery diarrhea with appearance of rice water

A

Vibrio cholerae

237
Q

Diagnosis: Watery diarrhea with gangrenous leg

A

Clostridium perfringens

238
Q

Diagnosis: Watery diarrhea in an immunocompromised patient

A

Protozoa (eg Giardia or Cryptosporidium)

239
Q

Diagnosis: Watery diarrhea

A

Think viruses first.

Rotavirus
Adenovirus
Norwalk virus

240
Q

Difference between mechanisms of cholera and pertussis toxins

A

Cholera: Permanently activates Gs (turns the “on” on)

Pertussis: Permanently disables Gi (turns the “off” off)

241
Q

What is edema factor?

A

A toxin in the Bacillus Anthracis exotoxin complex that functions as adenylyl cyclase

USMLE (13 decks)

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