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[Y1] Introductory Microbiology > Infectious diseases > Flashcards

Infectious diseases Flashcards

1
Q

what are the 5 thing you need to get an infectionous pathogen?

A
  • A pathogen (infectious agent)
  • Virulence factors (determine disease severity)
  • Exposure to pathogen
  • Infectious dose of pathogen
  • Susceptibility to pathogen
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2
Q

what are extracellular pathogens?

A

Extracellular pathogens grow outside cells in blood, tissue fluids

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3
Q

what are intracellular pathogens?

A

Intracellular pathogens grow and multiply within cells

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4
Q

what are facultative intracellular pathogens?

A

grow within or outside cells

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5
Q

what are obligate intracellular pathogens?

A

only grow when inside cells

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6
Q

what is pathogenicity?

A

the ability of a microbe to cause disease

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7
Q

what is virulence?

A

the degree or intensity of disease a pathogen can cause

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8
Q

what can virulence aid with?

A

adherence, colonisation, invasiveness

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9
Q

what is invasiveness?

A

the ability to spread to adjacent tissues

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10
Q

what is passive penetration?

A

(e.g. skin lesions / wounds, insect / animal bites)
Dissemination of pathogen from inoculation site to deeper tissues involves production of specific products and/or enzymes that promote spreading

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11
Q

what is active penetraction?

A

Active 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

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12
Q

what are exotoxins?

A

soluble, heat-labile, proteins that are secreted into surroundings as pathogen grows

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13
Q

what pathogen produces the most exotoxins?

A

Gram-positive bacteria
- may have toxin genes in genome, plasmid or prophage DNA

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14
Q

what are superantigens?

A

stimulate T-cells to release cytokines and can trigger cytokine storm – multiple organ failure

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15
Q

what percentage of the bodies T cells do superantigens stimuate?

A

30% of T cells of the immune system

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16
Q

what can endotoxins trigger?

A
  • Can trigger septic shock cascade
  • Inflammatory reaction
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17
Q

what is tropism?

A

the turning of all or part of an organism in a particular direction in response to an external stimulus.

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18
Q

what is the infectious dose 50 (ID50)?

A
  • number of pathogens that will infect 50% of an experimental group of hosts in a specified time
  • varies with pathogen
  • sanitation reduces number of pathogens
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19
Q

what is the lethal dose 50 (LD50)?

A

dose that kills 50% of experimental animals within a specified period

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20
Q

why are most microbes eliminated before they can case disease?

A

due to the immune system

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21
Q

how do successful pathogens overcome the immune system?

A

Pathogens have evolved a variety of strategies to evade or interfere with the immune response

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22
Q

what 3 things increase susceptibility to infection?

A
  • nutrition
  • genetic predeposition
  • stress
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23
Q

what is the incubation period?

A

period after pathogen entry, before signs and symptoms

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24
Q

what is the prodromal stage?

A
  • onset of signs and symptoms
  • not clear enough for diagnosis
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25
Q

what is the period of illness?

A

disease is most severe, signs and symptoms

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26
Q

what is convalescence?

A

signs and symptoms begin to disappear

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27
Q

what are the 4 stages of infectious diseases?

A
  1. incubation period
  2. prodromal stage
  3. period of illness
  4. convalescence
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28
Q

what are the 5 places pathogens can enter the body?

A
  1. Eyes (conjunctiva)
  2. Mouth
    • Respiratory tract
    • Digestive tract
  3. Skin
    • Abrasion/injury
    • Arthropod vector
    • Animal bite / scratch
  4. Urogenital tract
    • Vagina/urethra/penis
    • Placenta
  5. Anus
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29
Q

what are the 6 mediums of transmission?

A

Saliva – airborne or indirect contact
Blood – direct or indirect contact, or iatrogenic
Semen – direct contact (sexually transmitted)
Urine – indirect contact (ingestion of contaminated water / food)
Faeces - indirect contact (ingestion of contaminated water / food)
Blister / sore – direct contact, indirect contact (dust containing skin cells / dried blisters)

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30
Q

what is airborne transmission?

A

Pathogen propelled from respiratory tract of infected organisms by sneezing, coughing, or vocalization

31
Q

name 6 conditions that can be passed via airborne transmission

A
  • TB
  • pneumonic plague
  • meningitis
  • diphtheria
  • influenza
  • COVID
32
Q

what 3 things can lead to the faecal-oral route of pathogens?

A
  • eating contaminated food
  • drinking contaminated water
  • cross-contamination
33
Q

what are the 2 types of contact transmission?

A
  • direct contact
  • indirect contact
34
Q

what is direct contact transmission?

A

Physical interaction between source/reservoir and host
e.g. kissing, touching, sexual contact

35
Q

what is indirect contact transmission?

A
  • Contaminated everyday items that can transmit pathogens e.g. eating utensils, bedding, door handle, light switches are called fomites
  • Contaminated inanimate sources that transmit pathogens to multiple hosts are called vehicles e.g. food, water and biological tissue
  • Needle sharing can transmit pathogen directly into bloodstream
36
Q

what is vertical transmission?

A

Occurs when child acquires a pathogen from an infected mother during pregnancy (across placenta) or childbirth

37
Q

what is a congenital infection?

A

babies born with an infectious disease

38
Q

what is vector-borne transmission?

A
  • Living organisms that transmit pathogens are called vectors
  • Most vectors are arthropods (e.g. mosquitoes, ticks, mites, fleas, sand flies), some are vertebrates e.g. dogs, cats, rats, bats, skunks
39
Q

what is zoonoses?

A

When a disease is transmitted from animals to humans it is referred to as a zoonosis (plural = zoonoses)

40
Q

what is epidemiology?

A

Science that evaluates occurrence, determinants, distribution, and control of health and disease in a defined human population

41
Q

who was the first epidemiologist?

A

John Snow was the first epidemiologist, studied cholera in London

42
Q

what did john snow discover?

A

John Snow stated that cholera was transmitted via water (1849)

43
Q

define sporadic disease

A

occurs occasionally and at irregular intervals

44
Q

define endermic disease

A

maintains a relatively steady low-level frequency at a moderately regular interval

45
Q

define hyperendemic disease

A

gradually increase in occurrence frequency above endemic level but not to epidemic level

46
Q

define outbreak

A
  • sudden, unexpected occurrence of disease
  • usually focal or in a limited segment of population
47
Q

define epidemic

A
  • sudden increase in frequency above expected number
  • index case – first case in an epidemic
48
Q

define pandemic

A

increase in disease occurrence within large population over wide region (usually worldwide)

49
Q

what are the 3 ways to prevent infectious diseases?

A
  • reduce exposure / prevent transmssion (sanitation)
  • reduce susceptibility (vaccines)
  • eliminate pathogens (global eradication programmes)
50
Q

what was the mortality of smallpox?

A

Major: high mortality (20 – 60%)
Minor: Low mortality (1%)

51
Q

what were the long term effects of smallpox?

A

scarring, blindness, osteomyelitis

52
Q

what is variolation?

A

Variolation involved scratching scab material from someone with a mild case of smallpox and using it to inoculate scratch in the skin to intentionally cause disease

53
Q

when was the first vaccination? what was it for?

A

in 1796 Jenner gave James Phipps cow pox to stop him from getting small pox

54
Q

what is a vaccine?

A

A vaccine is a preparation of microbial antigens used to induce protective immunity

55
Q

what is immunisation?

A

the result obtained when vaccine stimulates immunity

56
Q

what are adjuvants?

A

nontoxic material that prolongs antigen interaction with immune cells and stimulates the immune response to the antigen

57
Q

what are adjuvants used for?

A

Adjuvants are mixed with antigens in vaccines to enhance the rate and degree of immunization

58
Q

what is a humoral response to a vaccine?

A

neutralising antibodies that inactivate extracellular pathogen

59
Q

what is a cellular response to a vacine?

A

kills cells that have been infected with intracellular pathogen

60
Q

how long does antibody production take after primary exposure and secondary exposure?

A
  • primary: several days after initial expossure
  • secondary: much faster (due to memory T cells)
61
Q

what are the 4 types of vaccines?

A
  • live attenuated
  • inactivated whole cell
  • acellular / subunit vaccine
  • DNA / RNA vaccine
62
Q

what are live attenuated vaccines?

A
  • Pathogens that can replicate but only weakly compared to wildtype
  • Do not cause disease but induce a full immune response
63
Q

what are inactivated whole cell vaccines?

A
  • Entire pathogen inactivated e.g. with formaldehyde
  • Do not infect but still generate an antibody response
64
Q

what are acellular/subunit vaccines?

A

Purified antigen from pathogen

65
Q

what are DNA/RNA vaccines?

A

Newer. First approved for humans, Pfizer- BioNTech and Moderna, mRNA vaccines, encoding SARS-Cov2 spike (S) glycoprotein

66
Q

what are the 4 forms of subunit vaccines?

A
  • capsular polysaccharides
  • recombinant surface antigens
  • inactivated exotoxins (toxoids)
  • Virus like particles (VLPs)
67
Q

what are subunit vaccines?

A

Use of purified molecules from microbes avoids some of the risks of whole-cell vaccines

68
Q

what is herd immunity?

A

when a large enough proportion of the population has acquired immunity to a pathogen, susceptible individuals are protected due to reduced transmission

69
Q

what is the DTaP vaccine?

A

D= diptheria
T= tetanus
aP= acellular pertussis

70
Q

HPV is responsible for >__% of cervical cancer

A

> 90%

71
Q

what are the 2 spike proteins of influenza?

A
  • Hemagglutinin (HA) binds to cell receptor (sialic acid), attaches virus to cell
  • Neuraminidase (NA) cleaves sialic acid, involved in release of virus from cell
72
Q

what is antigenic drift?

A

Drift consists of small changes (or mutations) in the genes of influenza viruses that can lead to changes in the surface proteins of the virus

73
Q

what is antigenic shift?

A

Shift is an abrupt, major change in a flu A virus, resulting in new HA and/or new HA and NA proteins in flu viruses that infect humans
- risk of pandemic

74
Q

what 3 reasons made the eradication of smallpox possible?

A
  • There is no other reservoir but man (including primates)
  • It causes only acute infections, from which the infected person either dies OR recovers with life-long immunity
  • Vaccinia virus is an effective immunogen (cross-reacting Abs)

[Y1] Introductory Microbiology (8 decks)

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