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Microbiology - Unit 2 - Zach H. > Pathogenicity of Microorganisms > Flashcards

Pathogenicity of Microorganisms Flashcards

1
Q

What are parasites?

A

> Live on or within a host organism and are metabolically dependent on the host.

> Are any organisms that cause disease.

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2
Q

What is infection?

A

> A parasite growing and multiplying within/on a host.

> May or may not result in overt infectious disease.

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3
Q

What is a pathogen?

A

> Any parasitic organism causing infectious disease.

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4
Q

What is a primary (frank) pathogen?

A

Causes disease by direct interaction with healthy host.

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5
Q

What is a opportunistic pathogen?

A

May be part of normal flora and causes disease when it has gained access to other tissue sites or host is immunocompromised.

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6
Q

What is pathogenicity?

A

Ability to cause disease.

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7
Q

What are the two sources of pathogens?

A

Animate (other humans or animals) or inanimate (water, soil, food).

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8
Q

What is a reservoir?

A

Natural environmental location in which the pathogen normally resides (can be animate or inanimate).

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9
Q

What is a vector?

A

Organisms that spread disease from one host to another.

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10
Q

What is an infectious disease?

A

Infection with viruses, bacteria, fungi, protozoa, and helminths.

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11
Q

What is meant by “signs” when discussing infectious disease?

A

Objective changes in body that can be directly observed.

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12
Q

What are the different courses of infectious disease?

A

> Incubation Period
- period after pathogen entry, before signs and symptoms.

> Prodromal Stage

  • onset of sings and symptoms
  • not clear enough for diagnosis

> Period of Illness
- disease is most severe, signs and symptoms

> Convalescence
- signs and symptoms begin to disappear

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13
Q

What do virulence factors allow a pathogen?

A

To outcompete host cells and resist their defenses.

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14
Q

Virulence of Organism

A

> Degree or intensity of pathogenicity.
Virulence Factors
- determine the degree to which the pathogen causes damage, invasion, infectivity
Determined in part by pathogen’s ability to survive outside host.
- more dependent on host (cannot survive outside of host) = less virulent
- E.g., M. tuberculosis can survive for extended periods (days to weeks) outside human host.

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15
Q

What is a pathogenicity island?

A

Major virulence factors on large segments on chromosomal or plasmid DNA.
- increase bacterial virulence
- absent in nonpathogenic members
- common sequence characteristics
> insertion-like sequences for mobility
> G + C content different from bacterial genome
> several open reading frames
- can be spread through horizontal transfer of virulence genes to bacteria

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16
Q

What are virulence factors?

A

> Animal model systems may be used to determine role of virulence factor in disease process.

> Determined by characteristics of the pathogen.

  • adherence and colonization
  • invasion
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17
Q

What is the first step in disease?

A

Entrance and attachment.

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18
Q

What is the definition of colonization?

A

A site of microbial reproduction on or within host.

** does not necessarily result in tissue invasion or damage **

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19
Q

What are adherence structures found on bacterium?

A

Pili of Fimbriae - bind complementary receptor sites on host cell surface.

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20
Q

What does Stretococcus mutans use for adherence?

A

Glycocalyx

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21
Q

What does E. coli use for adherence?

A

Fimbriae

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22
Q

What does Streptococcus pyogenes use for adherence?

A

M protein

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23
Q

What is the definition of infectivity?

A

Ability to create a discrete point of infection.

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24
Q

What is the definition of invasiveness?

A

Ability to spread to adjacent tissues.

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25
What are the two different types of penetration?
Active or Passive
26
What is active penetration?
Active penetration occurs through lytic substances which: > attack the extracellular matrix and basement membranes of integuments and intestinal linings > degrade carbohydrate-protein complexes between cells > disrupt host cell surface
27
What is passive penetration?
``` Passive penetration (e.g., skin lesions, insect bites, and wounds). > spread to deeper tissues involves production of specific products and/or enzymes that promote spreading. ```
28
What is bacteremia?
presence of viable bacteria in the blood
29
What is septicemia?
pathogens or their toxins in the blood
30
Invasion of Clostridium tetani.
Produces a number of virulence factors but is non-invasive.
31
Invasion of Streptococcus spp..
Span the spectrum of virulence factors and invasiveness.
32
What is toxigenicity?
Microbe has ability to produce toxins.
33
What is a toxin?
Specific substance that damages host.
34
What is an intoxication?
Diseases that result from entry of a specific preformed toxin into host (e.g., Tetanus toxin)
35
What is toxemia?
condition caused by toxins in the blood of host.
36
What are the characteristics of exotoxins?
> soluble, heat-labile, proteins > secreted into surroundings as pathogen grows > most exotoxin producers are Gram-positive > often travel from site of infection to other tissues or cells where they exert their effects > usually synthesized by specific bacteria that have toxin genes in their plasmids or prophage DNA > among the most lethal substances known > are highly immunogenic > stimulate production of neutralizing Ab (antitoxins) > chemically inactivated to form immunogenic toxoids (e.g., tetanus toxoid)
37
Do exotoxins typically cause a fever?
no
38
Can exotoxins be neutralized by an antitoxin?
yes
39
Is the LD50 of exotoxins large or small?
small
40
What is the main source of exotoxins?
Mostly Gram positive
41
What is the chemistry of exotoxins?
protein
42
What exotoxin does Corynebacterium diphtheriae release?
A-B toxin
43
What exotoxin does Streptococcus pyogenes release?
membrane-disrupting erythrogenic toxin
44
What exotoxin does Clostridium botulinum release?
A-B toxin; neurotoxin
45
What exotoxin does C. tetani release?
A-B toxin; neurotoxin
46
What exotoxin does Vibrio cholerae release?
A-B toxin; enterotoxin **note: This is a Gram negative bacteria**
47
What exotoxin does Staphylococcus aureus release?
superantigen
48
In AB toxins, what does each subunit do?
A subunit - responsible for toxic effect. | B subunit - binds to specific target cell (is recycled to cell surface)
49
List different types of exotoxins.
> AB exotoxins > Specific host site exotoxins > Membrane-disrupting exotoxins > Superantigens
50
Superantigen Characteristics
> Stimulate 30% of T cells of the immune system. - causes the T cells to overexpress and release cytokines - results in failure of multiple host organs allowing time for the microbe to disseminate **e.g., staphylococcal enterotoxin B**
51
How does botulism effect the host?
Acetylcholine is not getting to bind to ligand gated channel. SNAP-25 is targeted by toxin and is inhibited. Acetylcholine vesicle cannot bind to pre-synaptic cleft and be released from the axon.
52
What are the characteristics of endotoxins?
> heat stable > toxic (nanogram amounts) > weakly immunogenic (because of the lipid chemistry) > generally similar, despite source > cause general system effects - fever, weakness, diarrhea, inflammation, intestinal hemorrhage, and fibrinolysis, the enzymatic breakdown of fibrin, the major protein component of blood clots.
53
How do endotoxins bring about their effects on the host?
Bring about these effects indirectly. - endotoxin interacts with host molecules and cells, activating host systems. > coagulation, complement, fibrinolytic, and kininogen system. - e.g., interaction with macrophages -> release of endogenous pyrogen (induces fever) - e.g., binding to LPS-binding protein -> release of cytokines - tumor necrosis and others lead to septic shock.
54
What type of bacteria release endotoxins?
Gram negative
55
What is the metabolic product of endotoxins?
Present in LPS of outer membrane.
56
What is the chemistry of endotoxins?
lipids **remember - exotoxins are proteins**
57
Can endotoxins be neutralized by antitoxin?
no **remember - exotoxins can be neutralized by antitoxin**
58
Is the LD50 large or small for endotoxins?
relatively large **remember - exotoxins have small LD50**
59
Biofilm Development
Biofilm growth is physiologically different from planktonic growth. > may cause chronic infection > increases virulence > become less sensitive to antibiotics > make cells in biofilm more resistant to host defense ("frustrates" phagocytes)
60
What are the cell wall components and how do they provide virulence for the bacteria?
> M protein - resists phagocytosis (e.g., S. pyogenes) > Opa protein - inhibits T helper cells (e.g., N. gonorrhoeae) > Mycolic acid (waxy lipid) - resists digestion (e.g., Mycobacterium tuberculosis)
61
How do bacteria such as Shigella sp. and Rickettsia sp. resist host defenses?
Eject themselves from cell to cell using host actin.
62
How are capsules a virulence factor?
Prevent Phagocytosis: > Streptococcus pneumoniae > Haemophilus influenzae > Bacillus anthracis
63
What does coagulase do?
Coagulates fibrinogen
64
What does kinases do?
Digest fibrin clots
65
What does hyaluronidase do?
Hydrolyzes hyaluronic acid (found in connective tissue)
66
What does collagenase do?
Hydrolyzes collagen (is a good source for nucleic acids)
67
What does IgA proteases do?
Destroy IgA antibodies
68
Does a good pathogen have a high mortality rate?
No - because they don't want to kill off their host cells.
69
Do pathogens that have direct contact for transmission into their host tend to be highly or less virulent?
Less Virulent
70
Do pathogens that have vector-borne transmission into their host tend to be highly or less virulent?
Highly virulent in human host; relatively benign in vector.
71
Do pathogens that have a greater ability to survive outside of their host tend to be more or less virulent?
more virulent
72
True or False: Transmission of the bacteria into their host alone is not enough for infection to occur.
True *Tropism - pathogen must make contact with appropriate host tissue - determined by specific cell surface receptors.*
73
What are the 5 main modes of transmission?
``` > airborne > contact > vehicle > vector borne > vertical ```
74
Is transmission of a pathogen via droplet spread that travels less than 1 meter contact transmission or airborne transmission?
Contact Transmission **droplet spread that travels greater than 1 meter is airborne transmission**
75
In contact transmission, what is the difference between direct contact and indirect contact?
Direct Contact (person-to-person) - physical interaction between source/reservoir and host. e.g., kissing, touching, and sexual contact Indirect Contact - involves an intermediate (usually inanimate) e.g., eating utensils, bedding
76
Vehicles transmission
inanimate materials or objects involved in pathogen transmission
77
Common vehicle transmission
single vehicle spreads pathogen to multiple hosts (e.g., water and food)
78
Fomites in vehicle transmission
common vehicles such as surgical instruments, bedding, and eating utensils
79
In vector-borne transmission, what is external (mechanical) transmission?
passive carriage of pathogen on body of vector no growth of pathogen during transmission
80
In vector-borne transmission, what is internal transmission?
> carried within vector > harborage transmission - pathogen does not undergo changes within vector > biologic transmission - pathogen undergoes changes within vector
81
What is vertical transmission?
occurs when the unborn child acquires a pathogen from an infected mother > not as common as horizontal transmission > babies born with an infectious disease are said to have a congenital infection > example: - gonorrhea (especially in the eyes) - herpes - german measles - toxoplasmosis
82
What is the infectious dose 50?
> number of pathogens that will infect 50% of an experimental group of hosts in a specified time. > varies with pathogen > handwashing reduces number of pathogens * *Ex. Bacillus anthracis: - 3 portal of entry - ID50 through skin = 10-50 endospores - ID50 for inhalation is 10,000 to 20,000 endospores - ID50 for gastrointestinal anthrax is ingestion of 250,000 to 1,000,000 endospores
83
What is lethal dose 50?
Lethal dose (of a toxin) for 50% of the test population. *dose that kills 50% of experimental animals within a specified period* used to examine virulence factors and their release
84
Where do extracellular pathogens grow?
Outside cells in blood and tissue fluids.
85
Where do intracellular pathogens grow?
> Grow and mutiply within cells. > Facultative intracellular pathogens (grow within or outside cells) > Obligate intracellular pathogens (only grow when inside cells)
86
What are the two main factors of host susceptibility?
> defense mechanisms of host (innate and adapted/acquired immunity) > pathogenicity of pathogen
87
What are the portals of exit for microbes?
> respiratory tract (coughing and sneezing) > gastrointestinal tract (feces and saliva) > genitourinary tract (urine and vaginal secretions) > skin > blood (biting arthropods and needles or syringes)
88
Look over slide 58!!!!
Mechanisms of Pathogenicity
89
Look over slide 58!!!!
Mechanisms of Pathogenicity
90
Arthropods provide a portal of exit for microbes in: a) skin b) respiratory tract c) blood d) genitourinary tract
c) blood

Microbiology - Unit 2 - Zach H. (7 decks)

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