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Block 6 Week 3 > Sumby: Bacterial Pathogenesis > Flashcards

Sumby: Bacterial Pathogenesis Flashcards

1
Q

Infections and parasitic diseases are the second leading cause of death behind cardiovascular disease

A

True

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2
Q

Are most host:bacterial relationships parasitic?

A

no! mutualistic and commensal relationships predominate over parasitic - humans are colonized with bacteria that is essential and beneficial

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3
Q

List some roles of the human microbiome (ecological community of things that share our body space)

A

nutrient acquisition
stimulates innate and adaptive immune responses
helps maintain epithelial boundary functions
provides colonization resistance of pathogens

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4
Q

Problems with the human microbiome can lead to multiple conditions. Give a few examples.

A

psoriasis
obesity
inflammatory bowel disease
colorectal carcinoma

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5
Q

Give an example of how the human microbiome promotes adaptation

A

In Japan, some people have a gene for digesting seaweed in their microbiome. In other areas, this gene is normally just in environmental bacteria, but it was somehow transferred to humans so they could digest seaweed.

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6
Q

Clostridium difficle is a bacterial infection that is usually treated via oral antibiotics. Some spores are antibiotic resistant, however, and antibiotics also damage the gut microbiome. What is one alternative treatment option for these patients?

A

fecal microbiota transplantation
**donor stool is homogenized and placed in the GI tract during a colonoscopy to confer a better microbiome in the patient

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7
Q

What does H. pylori infection do to the diversity of the stomach microbiome?

A

decreases the number and abundance of other bacterial species

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8
Q

time between the moment the person is exposed to the microbe (or toxin) and the appearance of symptoms (note info is an important diagnostic clue)

A

incubation period

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9
Q

time during which nonspecific symptoms occur.

A

prodrome period

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10
Q

time during which specific clinical signs and symptoms occur.

A

disease period

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11
Q

time during which symptoms resolve and health is restored.

A

recovery period

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12
Q

What are the four stages of infection? What can happen in some people after the final stage of infection has resolved?

A
  1. incubation
  2. prodrome
  3. disease
  4. recovery

**after the recovery period, some people will become chronic carriers of the organism and may develop latent infections

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13
Q

How does human to human transmission of microbes occur?

A

direct contact

indirectly through a vector (mosquito or other host)

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14
Q

How does human-to-non-human transmission of microbes occur?

A

via animals (direct contact or animal vector)
soil
water
food

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15
Q

Human diseases for which animals are the reservoir are called (blank)

A

zoonoses

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16
Q

What are the main portals of entry into the body?

A

respiratory tract
GI
UG

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17
Q

Give a clinical example of a disease that is passed from direct human-to-human contact

A

gonorrhea

**sexual transmission or when giving birth

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18
Q

Give a clinical example of a disease that is passed from human-to-human via non-direct contact?

A

cholera

**fecal–>oral

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19
Q

Give a clinical example of a disease that is passed from human-to-human via the placenta.

A

congenital syphillis

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20
Q

Give a clinical example of a disease that is passed from the soil to humans

A

tetanus

**spores in soil enter skin

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21
Q

Give a clinical example of a disease that is passed from a water source to humans

A

Legionnaire’s disease

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22
Q

Give 3 different examples of diseases transmitted via an animal source.

A
  1. directly - cat scratch fever (bacteria enter cat scratch)
  2. insect vector - lyme disease
  3. animal excretion - hemolytic-uremic syndrome caused by e. coli (bacteria in cow poo is ingested in undercooked hamburger)
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23
Q

Give an example of a disease caused by bacterial transmission from one OBJECT to another

A

staph skin infection

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24
Q

How can a bacterial pathogen be successful in living in a host?

A
  1. enter the host and COLONIZE
  2. avoid the immune system
  3. acquire nutrients and REPRODUCE
  4. exit the host and move to a new cell (disseminate)
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25
Q

Is death of the host cell common in bacterial infections?

A

no; host and pathogen usually strike a balance that allows for both to survive

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26
Q

process whereby microbes attach to host cells or tissues.

A

adherence

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27
Q

asymptomatic harboring of microbes on or in the body; commensals as well as pathogens.

A

colonization

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28
Q

epithelial barrier breached; some host damage caused by a microbe; can be subclinical.

A

infection

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29
Q

Hospital-acquired infection,

occurs in 1/10 hospital patients.

A

Nosocomial infection

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30
Q

tissue destruction with specific signs and

symptoms.

A

disease

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31
Q

a microbe with the inherent capability
of causing infection and disease in a host with an
intact immune system.

A

pathogen

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32
Q

microbe that usually causes disease only in immunocompromised hosts

A

opportunistic pathogen

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33
Q

the ability of a microorganism to produce infection and disease in a host

A

pathogenicity

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34
Q

term that provides a quantitative measure of pathogenicity, or the likelihood of causing disease

A

virulence

35
Q

gene products that enable a microbe to establish itself on or in a host (e.g. exotoxins)

A

virulence factors

36
Q

Pathogens can show different virulence levels. Give an example of a pathogen with low virulence.

A

streptococcus salivarius

37
Q

Give an example of a pathogen with moderate virulence.

A

escherichia coli

**in colon, can cause urinary infections

38
Q

Give an example of a pathogen with high virulence.

A

bordetella pertussis

**causes whooping cough

39
Q

Give an example of a pathogen with extremely high virulence.

A

yersinia pestis

**cause of plague

40
Q

this microbe causes a bloody diarrhea 16 hours to 2 days after ingestion of contaminated foods.

A

salmonella spp.

41
Q

this microbe causes a bloody diarrhea 12 hours to 6 days after ingestion of contaminated foods.

A

shigella spp.

42
Q

this microbe is a frequent skin colonizer, can contaminate food during preparation and secrete heat-stable enterotoxins. The toxins enter the blood and affect the vomiting control center of the brain, inducing vomiting 1 to 6 hours following ingestion.

A

staph. aureus

43
Q

What are some things that make a bacteria virulent?

A

adhesins - can attach readily to host cells

surface capsules or slime layers - prevent phagocytosis

secretions - toxins

exotoxins - cytotoxic proteins, degradative enzymes, superantigens

endotoxins

44
Q

(blank) facilitate adherence to human cells. They are fibers that extend from the surface of bacteria that mediate attachment to specific host cell or tissue components

A

fimbriae or pili

45
Q

What are some adhesins that can promote pathogen adherence to host cells

A

Collagen-binding proteins
Fibrinogen-binding proteins
Fibronectin-binding proteins
Laminin-binding proteins

46
Q

(blank) or “slime layers” can promote pathogen adherence,

A

capsules

**ex: strep. pyogenes binds epithelial cells via capsule - host cells have hyaluronic-acid-binding protein that binds the capsule

47
Q

This is another name for the bacterial polysaccharide capsule or slime layer

A

glycocalyx

48
Q

How does the polysaccharide capsule enhance immune evasion?

A
  1. inhibits PAMPS on the microbe from binding recognized by pattern recognition receptors
  2. inhibits C3b from binding to the microbe and also keeps phagocytic cells from binding to C3b on the microbe
49
Q

What is a biofilm?

A

bacterial cells embedded in extracellular polymeric substance (a mixture of extracellular DNA, proteins, and polysaccharides)

**part of the infectious cycle for many bacterial pathogens

50
Q

How do biofilms assist pathogenic bacteria?

A

they help the bacteria to resist antibiotic treatments
they trap nutrients for bacterial growth
they allow bacteria to adhere to environmental surfaces and resist flushing
they allow bacteria to live in close association w other bacteria
they enhance immune evasion

51
Q

What is a bacterial secretion system?

A

when a bacteria injects various effector molecules (toxins, enzymes) into the host cell cytoplasm and alters the cell’s machinery or communication

52
Q

What is the most common type of bacterial secretion system? Describe what this entails.

A

Type 3 secretion system; secretion apparatus is assembled in the bacterial cell wall that forms a needle to penetrate the host cell membrane - effector proteins in the bacterium can now be injected into the cytoplasm of the host cell (injectosome)

53
Q

What is this:

a protein that promotes bacterial invasion of tissues or cells

A

invasin

54
Q

What are two types of invasins?

A 
extracellular proteins (ex: hyaluronidase of Strep. pyogenes which splits the epithelial cells of tissues)
intracellular proteins (ex: IpaB of Shigella flexneri)
55
Q

Some bacteria bind to cell surface (blank) and induce their own endocytosis; some bacteria escape the (blank), and others multiply in the (blank).

Bacteria may remain intracellular, or move through the cell and escape into the (blank) (transcytosis).

A

receptors; vacuole; phagolysosome; submucosa

56
Q

These are microorganisms that synthesize proteins that are toxic to their hosts; they are excreted into the environment or are found associated with the microbial surface; usually have some degree of host cell specificity

A

exotoxins

57
Q

Exotoxins are antigenic and induce antibodies called (blank).
Exotoxins can be modified to form (blank), which are antigenic but not toxic (e.g., tetanus toxoid vaccine).

A

antitoxins; toxoids

58
Q

What are the 4 classifications of exotoxins?

A

Type 1: cell surface active (superantigens like toxic shock syndrome toxin)
Type 2: membrane damaging (Clostridial alpha-toxin with phospholipase activity)
Type 3: intracellular (cholera toxin)
Type 4: extracellular damaging (hyaluronidase, collagenase)

59
Q

Describe the mode of action of the cholera toxin.

A

The cholera toxin has an A1 and an A2 domain. The A1 domain is cleaved from A2, making A1 catalytically active. ADP ribosylates Gs, which results in continuous activation of adenylate cyclase which leads to high cAMP levels. Increased cAMP activates the CFTRs causing a dramatic efflux of ions and water leading to diarrhea.

60
Q

bind simultaneously to T cell receptors and MHC class II molecules outside of the normal peptide-binding groove.

Hyper-stimulate T cells to secrete cytokines
(cytokine storm).

Up to 20% of all peripheral T cells can be
stimulated.

A

superantigens

ex: S. aureus:
Toxic shock syndrome toxin
Staph. enterotoxins

S. pyogenes:
Strep. pyrogenic exotoxins

61
Q

lipopolysaccharides (LPS) located in
the outer membrane of Gram-negative bacteria; they are
not secreted by bacteria; poorly antigenic

A

endotoxins

62
Q

What is the toxic component of LPS? What does this do?

A

Lipid A; induces the overproduction of cytokines and inflammatory mediators from macrophages leading to septic shock (fever, hypotension, multi-organ system failure)

63
Q

What two cascades does LPS activate?

A

coagulation **disseminated intravascular coagulatioon

complement **increased vascular permeability

64
Q

What makes E. Coli uropathogenic?

A

fimbriae

**fimbriae are significant virulence determinants of uropathogenic E. coli, the most common cause of urinary tract infections. These fimbriae mediate attachment of uropathogenic strains to uroepithelial cells

65
Q

What makes the capsule of Klebsiella pneumoniae virulent?

A

it resists phagocytosis

66
Q

What kind of environmental factors may control expression of virulence genes?

A

temp
pH
osmolarity

67
Q

In Corynebacterium diphtheria, the gene for diphtheria toxin is regulated by (blank)

A

iron concentration

68
Q

In Borrelia burgdorferi, expression of surface proteins is regulated by (blank)

A

temperature

69
Q

the production and release by individual bacteria of molecules called autoinducers that modulate gene expression in response to the density of a bacterial population.

A

Quorum sensing

70
Q

What does bacterial quorum sensing do?

A

facilitates coordinated responses by bacterial populations

Ex: if there are a lot of bacteria in a colony, this may lead to a coordinated response like biofilm formation

71
Q

Some virulence factors are present in all isolates of a given pathogenic species, part of the “core” (blank).

Some virulence factors are variably present between isolates, usually encoded on (blank) (e.g. plasmids, bacteriophages, pathogenicity islands [PAIs]).

Different isolates of the same bacterial species can have widely different (blank) characteristics.

A

chromosome; mobile genetic elements; virulence

72
Q

How do most bacterial plasmids replicate? What genes might plasmids carry? Do all pathogen isolates have plasmids?

A

extra-chromosomally; may contain genes for virulence factors or Ab resistance; no, some have many some have non

73
Q

Plasmids have essential roles in the ability of this bacteria to cause disease

A

Bacillus anthracis

74
Q

What are the two stages of bacteriophage replication? Which form of phage is likely to encode virulence factors?

A

lytic or lysogenic; lysogenic

75
Q

collections of genes, many of which encode virulence factors, that are clustered together on the bacterial chromosome

A

pathogenicity islands

76
Q

How are pathogenicity islands usually acquired?

A

via horizontal gene transfer or conjugation

77
Q

What determines the E.Coli pathotype?

A

mobile genetic elements

78
Q

What can antibiotic treatment of E.Coli infection lead to?

A

hemolytic uremic syndrome **the result of rapid/premature death of RBCs, the remnants of which clog the kidneys and lead to renal failure

79
Q

There is also evidence that Ab increase (blank) by E.Coli

A

Shiga-like toxin

80
Q

List a few ways in which bacteria defend against host immunologic clearance

A 
encapsulation
antigenic mimicry
antigenic variation
anti-Ig proteases
destruction of phagocytes
inhibition of chemotaxis/phagocytosis/phago-lysosomal fusion
81
Q

This organism expresses an arsenal of virulence factors to thwart the host immune response

A

GAS

82
Q

What are two ways in which bacteria can avoid opsonization via antigenic variation?

A
  1. phase variation: expression of surface proteins switched on or off
  2. antigenic variation: surface antigens switched from one type to another
83
Q

List a few intracellular bacterial pathogens that avoid humoral immunity

A 
Mycobacterium spp.
Brucella spp.
Francisella spp.
Rickettsia spp.
Legionella pneumophila
84
Q

How do some microorgansisms inhibit killing following phagocytosis?

A
  1. inhibition of phago-lysosomal fusion
  2. resistance to lysosomal enzymes
  3. escape from phagolysosome to cytoplasm

Block 6 Week 3 (6 decks)

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