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Microbiology > Lecture 11: Pathogenicity & Epidemiology > Flashcards

Lecture 11: Pathogenicity & Epidemiology Flashcards

1
Q

What is the ability to cause disease

A

Pathogenicity

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2
Q

What is the extent of pathogeniciy?

A

Virulence

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3
Q

What are the virulence factors?

A

adhesion factors
extracellular enzymes
toxins
antiphagocytic factors

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4
Q

What are the exo enzymes/ secreted enzymes?

A

Coagulase: coagulate blood

Kinases: Digest fibrin clots

Hyaluronidase: Hydrolyses hyaluronic acid

Collagenase: Hydrolyzes collagen

IgA proteases: destroy IgA antibodies

Siderophores: take iron from host iron-binding proteins

Antigenic variation: alter surface proteins

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5
Q

What are the adhesion factors on microbes?

A

Surface lipoproteins or glycoproteins called ligands bind to receptors on host cells

Ability to change or block the ligand or its receptor can prevent infection

Inability to make attachment proteins or adhesions renders the microorganisms avirulent

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6
Q

What are substances that contribute to pathogenicity?

A

Toxin

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7
Q

Ability to produce a toxin

A

Toxigeniciity

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8
Q

Presences of toxin the host’s blood

A

Toxemia

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9
Q

Inactivated toxin used in a vaccine

A

Toxoid

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10
Q

Antibodies against a specific toxin

A

Antitoxin

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11
Q

What are the characteristics of exotoxins that are extracellular and secretal?

A

Source: mostly Gram+

Metabolic product: by-products of growing cell

Chemistry: protein

Fever?: No

Neutralized by antitotoxin: yes

LD50: Small

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12
Q

Where are exotoxins produced?

A

Inside mostly gram-positive bacteria as part of their growth and metabolism.

They are then secreted or released following lysis into the surrounding medium

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13
Q

Type I, type II, and type III toxins

A
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14
Q

Explain type 1 toxins: superantigens

A

Cause an intense immune response due to (overhwelming amount of) cytokine released by hosts

Fever, nausea, vomiting, diarrhea, shock, death

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15
Q

Explain II toxins

A

Membrane-disrupting toxins

Lyse host’s cells:
Makes protein channels in the plasma membrane (eg leukocidins, hemolysins)

Disrupts phospholipid bilayer

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16
Q

Explain III A-B toxins

A
  1. Bacterium produces and releases exotoxin
  2. B (binding) component of exotoxin binds to host cell receptor and exotoxin enters cell
  3. A (active) component of exotoxin alters cell function by inhibiting protein synthesis
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17
Q

Describe endotoxins characteristics

A

Source: Gram negative

Metabolic product: present in LPS of outer membrane

Chemistry: Lipid A

Fever?: Yes

Neutralized by antitoxin: no

LD50: relatively large

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18
Q

Describe endotoxins

A

Endotoxins are part of the outer portion of the cell wall of gram-negative bacteria. They are liberated when the bacteria die and the cell wall breaks apart

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19
Q

Describe antiphagocytic factors

A

Certain factors prevent phagocytosis by the host’s phagocytic cells

-Bacterial capsule: composed of same chemicals found in host’s body
-Slippery - difficult for phagocytes to engulf the bacteria

-Antiphagocytic chemicals
-some prevent fusion of lysosome and [phagocytic vesicles
-Leukocidins directly destroy phagocytic white blood cells

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20
Q

What are the cytopathic effects of viruses?

A
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21
Q

Pathogenic properties of fungi

A

Fungal waste products may cause symptoms

Chronic infections provoke an allergic response

some fungi have toxins called mycotoxins

can also have capsule that prevents phagocytosis

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22
Q

Pathogenic properties of protozoa

A

presence of protozoa

protozoan waste products may cause symptoms

avoid host defenses by
-growing in phagocytes
-antigenic variation

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23
Q

Pathogenic properties of helminths (parasites0

A

use host tissue
presence of parasite interferes with host function
parasites metabolic waste can cause symtoms

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24
Q

Principles of epidemiology

A

Pathology: study of disease

Etiology: study of the cause of a disease

-Pathogenesis: development of disease
-Infection: colonization of the body by pathogens
-Disease: an abnormal state in which the body is not functionally normal

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24
Pathogenic properties of algae
neurotoxins produced by dinoflagellates -saxitoxin - paralytic shellfish poisoning
25
Normal microbiota or macrobiota
permanently colonize the host
25
Mechanisms of pathogenicity (chart)
26
Transient microbiota
present for hours, days, weeks, or months -cannot persist in the body -competition from other microorganism -elimination by the body's defenses cells -chemical or physical changes in the body can't colonize in the body
27
Symbiosis
close, long-termed reactions between two organisms
28
Commensalism
one organism is benefited and the other is unaffected
29
Mutualism
both organisms benefit
30
Parasitism
one organism is benefited at the expense of the other
31
Relationship between normal microbiota and the host is an example of?
Mutualism
31
Probiotics
Living microbes applies to or ingested into the body intended to exert a beneficial effect
32
Normal microbiota and the host
Normal microbiota protect the host by: -occupying niches that pathogens might occupy -producing acids -producing bacteriocins Some normal microbiota are opportunistic pathogens
33
Microbial antagonism
Competition between microbes
33
Contamination vs infection
Contamination- mere presence of microbes in or on the body Infection - an organism has evaded the body's external defenses, multiplied, and become established in the body
34
Resident/normal/ permanent microbiota
see chart
34
Portals of entry
Sites through which pathogens enter the body -skin (broken) -mucous membranes (nose, eyes, ears, mouth, vagina, anus, penus, urethra) -placenta -parenteral route (insect bite, injection, needle)
34
Locations of normal microbiota in humans
chart When does a person acquire normal flora? -essentially through birth -food, people, environment - mature normal flora How does a bacteria attach itself to the host? -Capsule, fimbriae, etc.,
35
Opportunistic pathogens
Normal microbiota that can cause disease under certain circumstances Conditions that provide opportunities for pathogens -immune suppression -Changes in the normal microbiota- changes in the relative abundance of normal microbiota may allow opportunity for a member to thrive and cause disease -introduction of normal microbiota into unusual site in the body
36
Skin
outer layer of packed, dead, skin cells usually a barrier to pathogens pathogens can enter -through opening or cuts -some can burrow into or digest the outer layers of skin
37
Parenteral route
not a true portal of entry, since its via injection or insertion pathogens deposited directly into tissues beneath the skin or mucous membranes
37
Mucous membrane
line the body cavities that are open to the environment provides a moist, warm environment respiratory tract is the most commonly used site of entry - entry is through the nose, mouth or eyes gastrointestinal tract - pathogens must be able to survive the acidic pH of the stomach
38
Pathogenic organisms
portal of entry attachment or adhesion to cause infection - bacteria viruses, and protozoa (parasites) Infection - the invasion of the host by a pathogen Disease - results only if the invading pathogen alters the normal functions of the body, also referred to as morbidity
39
Koch's postulates
see chart used to prove the cause of an infectious disease
40
Sign
a change in a body that can be measured or observed as a result of disease
41
Exceptions to Koch's postulates
41
Classifying infectious diseases
42
Symptom
a change in body function that is felt by a patient as a result of disease
43
Syndrome
a specific group of signs and symptoms tha accompany a disease
44
Communicable disease
a disease that is spread form one host to another (also contains contagious disease)
45
Contagious disease
a communicable disease that is easily spread
46
Non-communicable disease
a disease that is not transmitted from one host to another
47
Severity of duration of a disease Acute disease
symptoms develop rapidly
48
Severity of duration of a disease Chronic disease
disease develops slowly
49
Severity of duration of a disease Subacute disease
Symptoms between acute and chronic
50
Severity of duration of a disease Latent disease
disease with a period of no symptoms when the patient is inactive
51
Extent of host's involvement: Local infection
pathogens limited to a small area of the body
51
Extent of host's involvement: Systemic infection
an infection throughout the body
52
Extent of host's involvement: Focal infection
Systemic infection that began as a local infection
53
Extent of host's involvement: Bacteremia
Bacteria in the blood
54
Extent of host's involvement: Septiicemia
Growth of bacteria in the blood
55
Extent of host's involvement: Toxemia
toxins in the blood
56
Extent of host's involvement: Viremia
viruses in the blood
57
Extent of host's involvement: Primary infection
acute infection that causes the initial illness
58
Stages of infections
following infection, sequence of events called the disease process occurs Many infectious diseases have five stages following infection: 1. Incubation period: no signs or symptoms 2. Prodromal period: vague, general symptoms 3. Illness: most severe signs and symptoms 4. Decline: declining signs and symptoms 5. Convalescence: no signs or symptoms
58
Extent of host's involvement: Subclinical disease
No noticeable signs or symptoms (inapparent infection)
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Extent of host's involvement: Secondary infection
Opportunistic infection after a primary (predisposing) infection
59
Predisposing factors
Make the body more susceptible to disease -inherited traits such as the sickle-cell gene -climate and weather -fatigue -age -lifestyle -male/female - short urethra in females -chemotherapy
60
Movement of the pathogens out of the host
Pathogens leave host through portals of exit see chart
61
Reservoirs of infections
continual sources of infection humans: carriers may have inapparent infections or latent diseases animals: some zoonoses may be transmitted to humans nonliving things (soil)
62
Transmission of disease: contact
Directo contact: close association between infection and susceptible host Indirect contact: spread\ by fomites (touching surface that is contaminated) - or droplet transmission via airborne droplets
63
Relative frequency of nosomial infections
see pie chart
63
Nosocomial infections
Are acquired as a result of a hospital stay 5-15% of all hospital patients acquire nosocomial infections see chart
63
Transmission of diseases: vehicle and vector
Vehicles: transmission by an inanimate reservoir (food, water) Vectors: arthropods, especially fleas, ticks, and mosquitoes - Mechanical arthropod carries pathogen on feet -Biological pathogen reproduces in vector (intermediate hosts)
63
Transmission of disease
see chart
64
Occurrence of disease: Prevalence
Fraction of a population having a specific disease at a given time
64
Epidemology
The study of where and when diseases occur and how they are transmitted in a population
64
Emerging new diseases and contributing factors
65
Occurrence of disease: Incidence
fraction of a population that contracts a disease during a specific time period
66
Occurrence of disease: Pandemic disease
worldwide epidemic - disease that occur in a large area and also occur occasionally
66
67
Occurrence of disease: Epidemic disease
disease that occur in a large area and also occur occasionally
67
Occurrence of disease: Sporadic disease
disease that occurs occasionally in a population
68
Occurrence of disease: Endemic disease
Disease constantly present in a population Disease acquired by many hosts in a given area in a short time
68

Microbiology (17 decks)

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