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Basic Pathology > Infectious Disease and Bacterial Characteristics > Flashcards

Infectious Disease and Bacterial Characteristics Flashcards

1
Q

infection remains a major cause of ____

A

death and disease

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2
Q

some very successful eradication efforts

A
  • polio: worldwide
  • smallpox: worldwide
  • measles: western hemisphere
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3
Q

many remaining challenges of infectious disease

A
  • emerging diseases
  • antimicrobial/antibiotic resistance
  • globalization - increasing spread
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4
Q

endemic

A
  • regularly found in the population, stable

- ex: common cold, flu

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5
Q

epidemic

A
  • significant increase in new infections
  • AKA “outbreak”
  • ex: 2010 cholera outbreak in Haiti - vibrio cholera (contaminated drinking water)
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6
Q

pandemic

A
  • widespread epidemic
  • ex: flu pandemic of 1918: ~40 million deaths worldwide
  • ex: 2019-2020 SARS-COV-2 pandemic
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7
Q

5 modes of disease transmission

A
  • direct: droplet, direct contact

- indirect: airborne, vectors, vehicles

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8
Q

droplet transmission

A
  • short-range, short-term aerosols with large droplet particles
  • coughing, sneezing, and talking
  • ex: influenza, pertussis
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9
Q

direct contact transmission

A
  • physical touch
  • kissing, sexual intercourse, contaminated soil in an open wound
  • ex: HIV, herpes, hookworm
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10
Q

airborne transmission

A
  • longer-term, longer-range aerosols with small particles

- ex: measles, hantavirus (rodent urine)

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11
Q

vector transmission

A
  • organisms that carry infection between hosts

- arthropods and mosquitoes

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12
Q

vehicle transmission

A
  • inanimate objects that harbor the pathogen
  • fomites: cover paddle, slit lamp, countertops
  • contaminated food or water
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13
Q

entry portal

A
  • route by which infection enters a host
  • mucous membranes
  • lungs
  • skin
  • parenteral (IV)
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14
Q

exit portal

A
  • route by which infection leaves a host
  • bodily secretions (tears, saliva, mucous, etc.)
  • blood
  • respiratory droplet
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15
Q

zoonotic transmission

A
  • diseases that move from animal to human

- ex: SARS-COV-2 (bats), anthrax (sheep)

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16
Q

reservoir

A
  • traditional host or source of infection
  • environment (soil, air)
  • animals
  • human carriers (HIV)
  • microbiome/microbiota
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17
Q

vertical transmission

A
  • mother to child
  • placental: treponema pallidum (syphilis)
  • perinatal: HIV
  • postnatal: staphylococcus aureus
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18
Q

horizontal transmission

A
  • person to person

- direct or indirect contact

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19
Q

infectivity

A
  • measure of ability to establish an infection
  • measured by “ID50” or “infectious dose, 50%”
  • dose necessary to infect 50% of exposed individuals
  • ex: hepatitis B virus has an ID50 of 10 viral particles
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20
Q

pathogenicity

A
  • measure of ability to produce disease

- if you are infected, will you get sick or remain asymptomatic?

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21
Q

virulence

A
  • measure of disease severity

- if I get sick, how sick?

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22
Q

toxigenicity

A
  • ability of toxins produced by pathogens to cause damage to host cells
  • measured by “LD50” or “lethal dose, 50%”
  • dose necessary to cause death in 50% of exposed individuals
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23
Q

infectious microorganisms

A
  • bacteria
  • viruses
  • fungi
  • protozoa
  • helminths
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24
Q

bacteria characteristics

A
  • prokaryotes
  • no membrane-bound organelles
  • peptidoglycan cell wall (support and protection)
  • reproduce asexually via binary fission
  • horizontal gene transfer can occur, and antibiotic resistance can be transferred
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25
bacterial genetics
- circular DNA: genophore found in nucleoid region | - plasmids: separate from genophore, confer additional abilities
26
horizontal gene transfer
- conjugation: plasmid exchange via pilus | - transformation: uptake of free DNA from the environment
27
aerobic bacteria
- obligate aerobes | - require oxygen for growth/energy
28
anaerobic bacteria
- do not need oxygen for growth/energy - usually found in the GI tract - 3 types: obligate, aerotolerant, facultative
29
obligate anaerobes
die with exposure to oxygen
30
aerotolerant anaerobes
tolerate but do not use oxygen
31
facultative anaerobes
can use oxygen but don't need it to survive
32
bacterial cell wall
- used to classify bacteria - gram negative: outer membrane + thin cell wall, lose iodine-crystal violet complexes, appear red/pink with a counterstain - gram positive: thicker cell wall, retains iodine-crystal violet complexes, appear dark blue/purple when decolorized
33
bacteria morphology
- cocci= spherical - bacilli= rod-like - vibrio= comma-shaped - spirochete= spiral
34
bacteria categories
- "true" bacteria - filamentous bacteria - spirochetes - mycoplasma - rickettsia - chlamydia
35
"true" bacteria
- most disease causing bacteria - binary fission - certain types of morphologies - ex: staphylococcus aureus
36
filamentous bacteria
- branching, fungus-like structures | - ex: actinomyces israelii (causes canaliculitis)
37
spirochetes
- motile, anaerobic, spiral filaments | - treponema pallidum= syphilis
38
mycoplasma
- lack a cell wall= pleomorphic (many shapes) | - mycoplasma pneumoniae
39
rickettsia
- pleomorphic, obligate intracellular parasite | - rickettsia rickettsii
40
chlamydia
- pleomorphic, obligate intracellular parasite | - chlamydia trachomatis (causes chlamydial conjunctivitis and trachoma)
41
microbiome: normal flora
- 100 trillion microbes - 10:1 bacteria: human cells - symbiotic/commensal relationship - opportunistic pathogens
42
symbiotic/commensal relationship between humans and microbiome
- secrete digestive enzymes - metabolite production - part of the innate immune system
43
opportunistic pathogens in microbiome
- breakdown in immune/inflammatory system - injury - immunocompromised
44
process of infection: overview
1) colonization 2) invasion and evasion 3) multiplication 4) spread
45
process of infection: colonization
- originate in reservoir - transmission (direct or indirect) - adherence
46
bacterial adherence
- adhesion molecules and receptors - protects against mechanical barriers of the innate immune system, ex: coughing - tissue tropism - due to specificity of adherence - glycocalyx (glycoprotein coat) - sticky "capsule", blocks interaction of immune cells - fimbriae/pili - hairlike structures on the surface of the bacteria, stick to the host tissue (like Velcro) - flagella (also motility) - other various specific adhesion molecules
47
process of infection: invasion and evasion
- confrontation of host defense mechanisms - penetrate tissues - surrounding tissues or elsewhere - evade host immunity - specific and non-specific (innate barriers)
48
evasion of host immune response
- encapsulation - coat themselves in "self-protein" - degrade immune molecules (IgA) - adaptive immune suppression via toxins - block complement cascade products - antigenic variation
49
evasion of host immune response: encapsulation
- polysaccharide coat + some specific proteins | - prevents complement activation and inhibits phagocytosis
50
evasion of host immune response: coat themselves in "self-protein"
- host antibodies - fibrin coat - capsule antigen mimicry (hyaluronic acid)
51
evasion of host immune response: antigenic variation
- mutation: changes genes that code for surface molecules of bacteria; can happen quickly, even during an infection - transformation: picking up DNA from the environment - gene switching: different genes turn on and off at different times; bacteria express different surface antigens
52
process of infection: multiplication
- host= warm, nutrient rich environment --> rapid growth; tissue damage, disease symptoms - obligate intracellular - extracellular bacteria growth can produce biofilm
53
biofilm
- complex aggregation of bacteria - glycocalyx holds the cells together and blocks immune system - slows pathogen metabolism and growth (weaker immune response) - resistant to antibiotics and host defenses - grows on solid substrates: body (tooth plaque, heart valves (endocarditis)); medical devices (catheters, artificial valves, contact lenses)
54
process of infection: spread
- not required for disease (ex: cholera) - within body or between people - relies on a variety of virulence factors: adhesion molecules, toxins they produce aid in movement, protection against host immune system, opportunistic infections - some highly invasive (enter lymphatics, blood (sepsis))
55
process of infection: multiplication and spread
- rapid division (bacteria reproduce much faster than host can respond) - bacteremia or septicemia (presence of bacteria in blood, usually gram negative*) - secrete enzymes that allow spread (hyaluronidase, streptokinase/fibrinolysin, collagenase)
56
clinical stages of infection
- incubation - prodromal - invasion (illness) - convalescence
57
clinical stages of infection: incubation
-period between initial exposure and onset of first symptom
58
clinical stages of infection: prodromal
-onset of initial symptoms - vague (malaise)
59
clinical stages of infection: invasion (illness)
- period of active immune response | - major symptoms experienced
60
clinical stages of infection: convalescence
- period of recovery and decline of symptoms after removal - infection goes dormant - alternative: death
61
common symptoms: direct or indirect cause
- fatigue - malaise - weakness - lack of concentration - generalized aching - loss of appetite (anorexia)
62
hallmark of infection
fever
63
fever is caused by ____
- exogenous pyrogens: microbial origin - endogenous pyrogens: immune cell origin (IL-1, TNF-alpha) - pyrogens act on the hypothalamus
64
endotoxin/lipopolysaccharide (LPS)
- in outer membrane of gram negative bacteria - released upon death of bacteria - lipid A and polysaccharide chain - activates plasma protein systems (initiates widespread inflammatory response) - causes the release of inflammatory mediators (TNF-a, interferon, IL-1) - fever and shock may result (pyrogenic bacteria)
65
exotoxins
- enzymes produced while bacteria is alive - released during bacterial cell growth - cause major damage to host directly (disrupt plasma membranes, disrupt intracellular signaling, inhibit protein synthesis, weaken epithelial adhesions) - elicit production of antibodies (immunogenic)- we can develop immunity and vaccines against these exotoxins (ex: tetanus, pertussis, diphtheria)
66
botulinum toxin (clostridium botulinum)
- neurotoxin - blocks release of ACh at NMJ= no action - Botox: treatment for blepharospasm
67
diphtheria toxin (corynebacterium diphtheria)
- blocks protein synthesis within target cells | - causes necrosis of heart and liver
68
cholera toxin
- changes electrolytic balance across intestinal cell membrane - causes massive outflow of water into intestinal lumen - can cause death due to dehydration
69
superantigens
- exotoxins (some) - binds MHC II and TCR regardless of specificity (cause activation of T-cells w/o being specific for that T-cell) - activates many more Helper T-cells (widespread activation) - induce excessive cytokine production (fever, low blood pressure, shock)
70
endospores
- produced by some gram positive bacteria - formed under harsh environments - metabolically inactive - resistant to environmental extremes (heat, dryness, radiation, acids and other chemicals) - bacillus anthracis and clostridium botulism

Basic Pathology (21 decks)

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