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Medical Microbiology > L8: Bacterial Pathogenicity > Flashcards

L8: Bacterial Pathogenicity Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

_____: Sum of the characteristics that allow bacterium to produce disease (biochemical, structural, genetic)

A

Virulence

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2
Q

What are the two primary bacterial defense strategies?

A

1.Colonize and invade host surfaces
2. Evade complement, phagocytes, and antibody response

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3
Q

True or False: For a pathogen to penetrate intact skin, there has to either be disruption of skin (catheter, surgery) or transmission by arthropods (B. burdorfi, Lyme)

A

True

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4
Q

What do most bacteria have that makes it easier for mucin to trap them?

A

Mucin binding surface

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5
Q

What three features do bacteria that are able to EVADE trapping by mucin have?

A
  1. Lack mucin receptors
  2. Make mucin-degrading enzymes (hydrolases)
  3. Move between mucin strands
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6
Q

True or False: Colonic bacteria (clostridia, enterobacteria, B. fragilis) tend to be good at evading trapping by mucin layer

A

True

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7
Q

_____: small cysteine-rich cationic proteins, a natural bactericidal, that create PORES in bacterial membranes + diffuse through porins and peptidoglycan to reach CYTOPLASMIC MEMBRANE

A

Defensins

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8
Q

____, which has a negative charge, binds defensins and prevents them from reaching the cytoplasmic membrane
A. TLR
B. LPS
C. Olg gene
D. Bacterial membranes

A

B. LPS

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9
Q

What are two ways that the bacterial cell gets rid of defensins?

(hint: enzymes and pumps)

A
  1. Peptidase degrades it
  2. Cytoplasmic proteins pump them out
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10
Q

Which immunoglobulin molecule makes mucin sticky + binds bacterial antigens (via ABC and interact w/mucin via their Fc portions)?
A. sIgG Protease
B. sIGB Protease
C. sIGD Protease
D. sIGA Protease

A

D. sIGA Protease

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11
Q

Bacteria produce extracellular enzyme that
cleave ___ at hinge region, breaking links
between bacteria and mucin

A

IgA

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12
Q

What are the two type of microbial adhesion factors that exist?

A

Protein and Polysaccharide

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13
Q

Are Flagella, Fimbrae, Pili, S Layer, and Afimbrial polysaccharide or protein adhesions?
A. Polysaccharide Adhesions
B. Protein Adhesions

A

B. Protein Adhesions

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14
Q

True or False: The capsule and cell wall are protein adhesions

A

False - polysaccharide

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15
Q

True or False: Afimbriae, Flagella, Fibriae, and Pili are all appendages

A

True

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16
Q

Where in bacteria is the S Layer Found?
A. Cell envelope
B. Cell wall
C. Cytoplasm
D. Outer Membrane

A

A. Cell envelope

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17
Q

True or False: In medical situations, adhesions would be considered a major determinant of virulence for many pathogens

A

True

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18
Q

Which two rod-shape, hair-like protein structures on surface of
bacteria mediate attachment?

A

Pili and fimbriae

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19
Q

Tip structure of fimbriae and pili attaches specifically to receptor on host
cell, often carbohydrate residues of ____ or ___

A

glycoproteins or glycolipids

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20
Q

True or False: Fimbrae play vital role in conjugation ; comprise subunits
called pillin that forms a canal that allowed exchange of DNA between two bacterial cells; serves as receptors for certain viruses (bacteriophage)

A

False - Pili !

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21
Q

Which is found in greater abundance in the bacteria cell and is specialized for attachment of bacteria to its host?
A. Pili
B. Fimbriae
C. Flagella

A

B. Fimbriae

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22
Q

Pili are constantly lost and reformed (due to fragility). How does this help bacteria avoid host defenses?

A

Change pilus type by altering antigenicity

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23
Q

True or False: Pili and Fimbriae allow bacteria and host cell to form initial loose
contact, triggering mechanisms of tighter adherence

A

True

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24
Q

True or False: Mostly gram-positive pathogen (E.coli - urinary tract
infections and gastroenteritis), V. cholera,
P. aeruginosa, and Neisseria spp have fimbrae and pilli

A

False - gram negative!

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25
Q

After adhesion in a bacterial cell, there is ____ ____. What are the two outcomes?

A

signal transduction

  1. Host alters gene expression in response to adhesion binding
  2. +/- virulence genes of bacterial cell
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26
Q

_____: Cells surface proteins that do not form
pili
A. Apillus
B. Afimbrial
C. Aflagellar

A

B. Afimbrial

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27
Q

True or False: Afimbrial cells likely mediate WEAKER binding of bacterial and host cells
and may bind proteins on carbohydrates rather than host cells

A

False - Afimbrial cells likely mediate TIGHTER binding of bacterial and host cells
and may bind proteins on HOST CELLS
rather than carbohydrates

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28
Q

Yersinia, Neisseria, E. coli, and Strep/Staph all share which feature?
A. Apillus
B. Afimbrial
C. Aflagellar

A

B. Afimbrial

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29
Q
A
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30
Q

___: filamentous protein structures that provide swimming movement for most motile bacterial cells
A. Fibrae
B. Flagella
C. Pili

A

B. Flagella

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31
Q

Which pathogen has motility and is its determinant of virulence? (swims into intestinal mucosa to avoid being flushed out by peristaltic action of the gut)
A. Strepto
B. Staphylo
C. Vibrio
D. Enterbacteria

A

C. Vibrio

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32
Q

The distally located flagellar cap protein has been reported to function as adhesins in which three pathogens?

A

1) E.coli
2) P. aeruginosa
3) C. difficile

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33
Q

True or False: Flagella may also adhere to amoebae or connect two bacterial species

A

True

34
Q

____: Proteins in outermost layer of cell envelope (underneath capsule if present) and has tiled appearance; can function as adhesions (!!)

A

S Layers

35
Q

Which three pathogens have S Layers?

A
  1. Gram (+)
  2. Gram (-)
  3. Archea
36
Q

How do S Layers contribute to bacterial virulence?

A

Protect bacterium against 1) complement and 2) phagocyte attack

37
Q

Teichoic acids and gram-positive cell wall (as seen in Strep and Staph) are examples of ____ adhesions
A. Protein Adhesions
B. Polysaccharide Adhesions

A

B. Polysaccharide Adhesions

38
Q

Capsule of Mycobacteria are also
recognized by host cell receptors to
promote ____
A. virulence
B. adherence

A

B. adherence

39
Q

True or False: LPS/cell wall are polysaccharide adherins

A

True

40
Q

___: Toxic components of the cell wall of Gram-
neg. and positive bacteria are central
mediators in the development of septic
shock

A

LPS

41
Q
A
42
Q

Why is iron concentration in
human body is low?

A

Mostly bound to: lactoferrin, transferrin, ferritin, and Hb

43
Q

Bacteria secrete
siderophore, which carries ___

A

iron

44
Q

Siderophores-iron
complexes are taken up by
special _____
receptors on the bacterial
surface

A

siderophores

45
Q

What happens to iron-siderophore complexes that are internalized by bacteria?

A

Cleaved to release the iron inside the bacteria

46
Q

True or False: Since free iron is scarce in tissue fluids and blood, bacterial siderophores compete effectively
for Fe3+ bound to lactoferrin and transferrin

A

True

47
Q

What are two ways that bacteria remove iron?

A
  1. Bind and directly remove iron from host’s transferrin, lactoferrin, or Hb
  2. Bacteria make toxins, which kill host, leading to iron release
48
Q

What is an example of a pathogen that does not require iron (iron abstinence) but uses other ions, such as: manganese?
A. Cholera
B. Vibrio
C. Borrelia burgdorgeri
D. Streptococcus

A

C. Borrelia burgdorgeri

49
Q

What is the function of invasion?

A

Allows bacteria to gain deeper access into the host to
perpetuate the infection cycle

50
Q

Which type of invasion occurs when a microbe breaks down the barriers of a tissue to disseminate in the host while remaining outside of host cells?
A. Intracellular Invasion
B. Extracellular Invasion

A

B. Extracellular Invasion

51
Q

_____ degrade host’s extracellular molecules by producing elastase/collagenase, which aids tissue
invasion and is associated with keratitis, burn
tissue necrosis, and cystic fibrosis

A. P. aeruginosa
B. C. diff
C. E. Coli
D. Streptococcus

A

A. P. aeruginosa

52
Q

Which five enzymes are secreted by beta-hemolytic Streptococcus and S. aureus to degrade host cell molecules?

A
  1. Hyaluronidase* : cleaves
    proteoglycans in connective tissue
  2. Streptokinase and Staphylokinase: breaks down fibrin clots
  3. Lipase: degrades accumulated host oils
  4. Nuclease: digests RNA and DNA
  5. Haemolysins: lyse erythrocytes and other cell types
53
Q

S. aureus secretes ____, an enzyme that clots plasma, forming a sticky coat of fibrin around themselves; opposite effect of kinase
A. Lipase
B. Coagulase
C. Nuclease
D. Hyaluronidase

A

B. Coagulase

54
Q

_____: A microbe penetrates the cells of a host tissue and gains access to the intracellular environment

A. Intracellular Invasion
B. Extracellular Invasion

A

A. Intracellular Invasion

55
Q

Intracellular host invasion can be facilitated by which two aspects?

A
  1. Natural phagocytosis mechanisms (macrophage, neutrophil)
  2. Induced uptake: pathogens signals host cell to engulf adhered bacteria (type 3 secretion systems)
56
Q

True or False: Salmonella and Shigella use type III
secretion systems

A

True

57
Q

True or False: Host cells can be phagocytes (macrophages and neutrophils) or non-phagocytic cells (epithelial and endothelial)

A

True

58
Q

What type of lifestyle do Chlamydia, Rickettsia, and
Mycobacterium have?
A. Facultative Intracellular
B. Obligate Intracellular
C. Anaerobic Intracellular

A

B. Obligate Intracellular

59
Q

______is a facultative intracellular pathogen that persists for years and require extensive antibiotic therapy
A. Mycoplasm
B. Neiserria
C. Mycobacterium
tuberculosis

A

C. Mycobacterium
tuberculosis

60
Q

What are the three general intracellular niches in which pathogens reside?

A
  1. Within phagolysome
  2. Within phagosome
  3. Within host cell cytosol
61
Q

Chlamydia, Salmonella, Legionella, and Mycobacterium all:
A. prevent phagosome-lysosome fusion
B. escape from phagosome into cytoplasm

A

A. prevent phagosome-lysosome fusion

62
Q

Where does Coxiella burnetti reside?
A. phagosome
B. phagolysome
C. host cell cytosol

A

B. phagolysome

63
Q

Where do: Shigella, Listeria, and Rickettsia reside?
A. phagosome
B. phagolysosome
C. host cell cytosol

A

C. host cell cytosol

Escaping from phagosome into cytoplasm is
mediated by a bacterial protein that disrupts host’s
membranes either by degrading membranes or by
forming pores in the membrane

64
Q

True or False: In addition to the host cell lysis, Shigella and Listeria utilize a pathway of cell-to-cell spread

A

True

  • Involves extension of the infected cell into an adjacent cell, followed by membrane fusion
    and formation of a bacteria-containing vacuole in the adjacent cell
65
Q

Bacteria residing in macrophages and neutrophils may use these cells as _____ spread systemically via blood or lymphatic circulatory systems

A

vehicle to

66
Q

Salmonella, Yersinia, and Brucella
move between tissue in which manner?
A. Lyse host membrane
B. Vehicle to spread
C. Cell to cell spread

A

B. Vehicle to spread

67
Q

Chlamydia and Rickettsia:
A. lyse the host cell membrane
B. vehicle to spread
C. cell to cell spread

A

A. lyse the host cell membrane

  • releasing infectious bacteria which attach to and invade adjacent cells
68
Q

_____: network of polymers covering surface of
bacteria, usually polysaccharides (proteins)

A

Capsules

69
Q

True or False: Capsules protect against host immune response (complement activation, phagocyte-mediated killing, and abx therapy) and leads to host mediated pathogenesis

A

True

70
Q

What three pathogens utilize capsules?

A
  1. S. pneumoniae
  2. Neisseria
  3. P. aeruginosa
71
Q

Some bacteria have capsule that resemble host
polysaccharide, such as: hyaluronic acid in _____ or sialic acid in ______
A. Neisseria and Salmonella
B. Neisseria and S. pyogenes
C. S. pyogenes and Neisseria
D. S. pyogenes and Salmonella

A

C. S. pyogenes and Neisseria

72
Q

True or False: Bacterial capsules that resemble host polysaccharides, as in hyaluronic acid, is immunogenic

A

False - it is NOT immunogenic and host does NOT produce antibodies that opsonize capsular surface

73
Q

True or False: Capsules may mediate specific or non-specific attachment

A

True

74
Q

Which molecule is a reactive form of nitrogen made by some cells in the human body as an antibacterial defense?

A

NO

75
Q

In E. coli, resistance to NO is mediated by ____, which is normally part of the respiratory system

A

flavohemoglobin

76
Q

What is the function of flavohemoglobin?

A

Converts NO into NO3-

77
Q

What are two LPS modifications that prevent formation of complement components?

A
  1. Sialic acid bound to O antigen (E. coli) or to LOS of Neisseria
  2. Changes in length of O antigen side chains prevents MAC killing (serum resistance)
78
Q

Which two mechanisms prevent migration of phagocytes?

A
  1. Enzymes that degrade C5a, strategy for interfering with signaling function of complement
  2. Toxic proteins that kill phagocytes, inhibit migration, or reduce ox burst strength
79
Q

What are the three major ways that pathogens evade host’s antibody response?

A
  1. Alter pilus protein
  2. Capsule that resembles host
  3. Bacteria coat themselves with host proteins (fibronectin or bind to Igg, e.g protein A or G)
80
Q

______ helps bacteria evade antimicrobial peptides made by epithelial tissues in lungs (as part of innate immune response)
A. capsule shedding
B. capsule uncloaking
C. capsule evasion

A

A. capsule shedding

81
Q

What are 2 host proteins that pathogens can coat themselves with to evade host antibody response?

A

Fibronectin
Immunoglobulin

  • Note: these proteins bind Fc portion of antibodies but do not lead to bacteria opsonization
82
Q

When Protein A binds to S. Aureus, the ___ portion of the IgG is not available for the receptor, leading the pathogen free to begin infecting cells

A

Fc portion

Medical Microbiology (31 decks)

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