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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
Q

bacterial genetics

A
  • circular DNA: genophore found in nucleoid region

- plasmids: separate from genophore, confer additional abilities

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26
Q

horizontal gene transfer

A
  • conjugation: plasmid exchange via pilus

- transformation: uptake of free DNA from the environment

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27
Q

aerobic bacteria

A
  • obligate aerobes

- require oxygen for growth/energy

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28
Q

anaerobic bacteria

A
  • do not need oxygen for growth/energy
  • usually found in the GI tract
  • 3 types: obligate, aerotolerant, facultative
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29
Q

obligate anaerobes

A

die with exposure to oxygen

30
Q

aerotolerant anaerobes

A

tolerate but do not use oxygen

31
Q

facultative anaerobes

A

can use oxygen but don’t need it to survive

32
Q

bacterial cell wall

A
  • 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
Q

bacteria morphology

A
  • cocci= spherical
  • bacilli= rod-like
  • vibrio= comma-shaped
  • spirochete= spiral
34
Q

bacteria categories

A
  • “true” bacteria
  • filamentous bacteria
  • spirochetes
  • mycoplasma
  • rickettsia
  • chlamydia
35
Q

“true” bacteria

A
  • most disease causing bacteria
  • binary fission
  • certain types of morphologies
  • ex: staphylococcus aureus
36
Q

filamentous bacteria

A
  • branching, fungus-like structures

- ex: actinomyces israelii (causes canaliculitis)

37
Q

spirochetes

A
  • motile, anaerobic, spiral filaments

- treponema pallidum= syphilis

38
Q

mycoplasma

A
  • lack a cell wall= pleomorphic (many shapes)

- mycoplasma pneumoniae

39
Q

rickettsia

A
  • pleomorphic, obligate intracellular parasite

- rickettsia rickettsii

40
Q

chlamydia

A
  • pleomorphic, obligate intracellular parasite

- chlamydia trachomatis (causes chlamydial conjunctivitis and trachoma)

41
Q

microbiome: normal flora

A
  • 100 trillion microbes
  • 10:1 bacteria: human cells
  • symbiotic/commensal relationship
  • opportunistic pathogens
42
Q

symbiotic/commensal relationship between humans and microbiome

A
  • secrete digestive enzymes
  • metabolite production
  • part of the innate immune system
43
Q

opportunistic pathogens in microbiome

A
  • breakdown in immune/inflammatory system
  • injury
  • immunocompromised
44
Q

process of infection: overview

A

1) colonization
2) invasion and evasion
3) multiplication
4) spread

45
Q

process of infection: colonization

A
  • originate in reservoir
  • transmission (direct or indirect)
  • adherence
46
Q

bacterial adherence

A
  • 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
Q

process of infection: invasion and evasion

A
  • confrontation of host defense mechanisms
  • penetrate tissues - surrounding tissues or elsewhere
  • evade host immunity - specific and non-specific (innate barriers)
48
Q

evasion of host immune response

A
  • encapsulation
  • coat themselves in “self-protein”
  • degrade immune molecules (IgA)
  • adaptive immune suppression via toxins
  • block complement cascade products
  • antigenic variation
49
Q

evasion of host immune response: encapsulation

A
  • polysaccharide coat + some specific proteins

- prevents complement activation and inhibits phagocytosis

50
Q

evasion of host immune response: coat themselves in “self-protein”

A
  • host antibodies
  • fibrin coat
  • capsule antigen mimicry (hyaluronic acid)
51
Q

evasion of host immune response: antigenic variation

A
  • 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
Q

process of infection: multiplication

A
  • host= warm, nutrient rich environment –> rapid growth; tissue damage, disease symptoms
  • obligate intracellular
  • extracellular bacteria growth can produce biofilm
53
Q

biofilm

A
  • 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
Q

process of infection: spread

A
  • 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
Q

process of infection: multiplication and spread

A
  • 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
Q

clinical stages of infection

A
  • incubation
  • prodromal
  • invasion (illness)
  • convalescence
57
Q

clinical stages of infection: incubation

A

-period between initial exposure and onset of first symptom

58
Q

clinical stages of infection: prodromal

A

-onset of initial symptoms - vague (malaise)

59
Q

clinical stages of infection: invasion (illness)

A
  • period of active immune response

- major symptoms experienced

60
Q

clinical stages of infection: convalescence

A
  • period of recovery and decline of symptoms after removal
  • infection goes dormant
  • alternative: death
61
Q

common symptoms: direct or indirect cause

A
  • fatigue
  • malaise
  • weakness
  • lack of concentration
  • generalized aching
  • loss of appetite (anorexia)
62
Q

hallmark of infection

A

fever

63
Q

fever is caused by ____

A
  • exogenous pyrogens: microbial origin
  • endogenous pyrogens: immune cell origin (IL-1, TNF-alpha)
  • pyrogens act on the hypothalamus
64
Q

endotoxin/lipopolysaccharide (LPS)

A
  • 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
Q

exotoxins

A
  • 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
Q

botulinum toxin (clostridium botulinum)

A
  • neurotoxin
  • blocks release of ACh at NMJ= no action
  • Botox: treatment for blepharospasm
67
Q

diphtheria toxin (corynebacterium diphtheria)

A
  • blocks protein synthesis within target cells

- causes necrosis of heart and liver

68
Q

cholera toxin

A
  • changes electrolytic balance across intestinal cell membrane
  • causes massive outflow of water into intestinal lumen
  • can cause death due to dehydration
69
Q

superantigens

A
  • 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
Q

endospores

A
  • 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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