1
Q
total cells in our body
A
10 trillion
2
Q
total microorganisms in our body
A
100 trillion
3
Q
term for all microbes that reside on or within a person
A
indigenous microflora
4
Q
how many different species of indigenous microflora do we have
A
500-1000
5
Q
what has no indigenous microflora
A
a fetus
6
Q
when does a fetus get indigenous microbes
A
during birth, as they are exposed to maternal vaginal, fecal, and skin microbiota
7
Q
how much bacteria do we have on our skin
A
1 trillion
8
Q
what does the bacteria on our skin do
A
break down the chemicals in sweat, causing body odor
9
Q
what is the bacteria on our teeth
A
oral streptococci
10
Q
what is oral streptococci
A
biofilms of bacteria 300 to 500 cells thick on the surface of teeth
11
Q
what does oral streptococci cause
A
dental plaque
12
Q
how many species of bacteria are in our gut
A
> 500
13
Q
how much does the bacteria in our gut weigh in total
A
3.3 pounds
14
Q
what does the bacteria in our gut do
A
- break down carbs
- make essential nutrients (vitamins K & B12)
- crowd out harmful bacteria
15
Q
what major bacteria is in the gut
A
Firmicutes and Bacteroidetes
16
Q
what is vaginal flora
A
the community of microorganisms that normally live in the vagina
17
Q
what group does vaginal flora belong to
A
the beneficial ones belong to the Lactobacillus group
18
Q
what does Lactobacillus do
A
produce lactic acid, preventing growth of harmful invaders like candida albicans
19
Q
what does Lactobacillus protect against
A
hostile invaders like the pathogenic yeast Candida albicans which causes vaginal thrush
20
Q
what is a latent infection
A
- viruses that don’t leave the body after infection
- they remain inside cells in a dormant state
21
Q
examples of a latent infection causing virus
A
- human papillomavirus (HPV)
- herpes
- chickenpox
22
Q
how many types of HPV can infect humans
A
> 100
23
Q
what are fossil viruses
A
ancient viral genetic sequences that integrated into the germline of host organisms millions of years ago and were passed down to offspring
24
Q
how much of our genome is fossil viruses
A
1/12
25
what is symbiosis
a close interaction between two different species living together
26
examples of symbiotic relationships
- mutualism
- neutralism
- commensalism
- parasitism
- synergism
27
what is mutualism
both organisms gain something
28
what is neutralism
two organisms live in the same environment but don’t affect each other at all
29
what is commensalism
one organism gains something, the other is unaffected
30
what is parasitism
one organism (the parasite) benefits while the other is harmed
31
what is synergism
two organisms work together and the outcome is greater than either could achieve alone
32
mutualism vs synergism?
- mutualism is symbiotic relationship necessary for survival
- synergism is a cooperative interaction, but is not necessary for survival
33
what are pathogens
microorganism that cause disease
34
what percentage of microbes are harmful to humans
<3%
35
what is an opportunistic pathogen
a microorganism that doesn’t cause disease in a healthy person, but can cause infection if the conditions are right
36
bacterial ports of entry
- ingestion
- inhalation
- trauma
- needlestick
- anthropod bite
- sexual transmission
37
example of bacteria that enters via needlestick
staphylococcus aureus
38
example of bacteria that enters via inhalation
streptococcus
39
what were the earliest known diseases in egypt
- tuberculosis
- syphilis
- parasitic worm infections
40
what were the earliest known diseases in greece
bubonic plague
41
what were the earliest known diseases in china
smallpox
42
examples of more earliest known diseases
- rabies
- anthrax
- measles
- diphtheria
- typhoid fever
43
what is the germ theory
the idea that certain diseases are caused by the invasion of the body by microorganisms
44
what are Koch postulates
four established criteria designed to determine if a specific microorganism causes a specific disease
45
what are the 4 Koch's postulates
1. the microorganism must be found in all organisms suffering from the disease, but not in healthy organisms
2. the microorganism must be isolated from a diseased organism and grown in pure culture
3. the cultured microorganism must cause disease when introduced into a healthy organism
4. the microorganism must be re-isolated from the newly infected host and identified as being identical to the original organism
46
what were the original postulates based on
anthrax and tuberculosis
47
what are the revisioned postulates
P1: first posulate should be abandoned as the disease can be present in asymptomatic individuals
P2: not all microbes can be grown in artificial culture
P3: the cultured microbe won't always cause disease when introduced to another individual, so it is revised to "should" cause disease not "must" cause disease
48
why does exposure to pathogen not always lead to disease
- organism is unable to grow at site of contact
- absence of host receptors for colonisation
- antibacterial factors
- microbial antagonism: indigenous flora uses up nutrients and/or produces antibacterial factors
- overall health status
- immunity to organism (natural or after vaccination)
- elimination by immune system
49
what are antibacterial factors called
bacteriocins
50
what's an example of antibacterial factors
lysozomes in tears can fend off eye infections
51
what are the periods in the course of an infectious disease
1. incubation period
2. prodromal period
3. illness
4. convalescent period
52
what is the incubation period
- time between initial infection and the first appearance of symptoms
- patient feels normal
53
what is the prodormal period
- specific disease symptoms haven't appeared
- patient feels generally unwell or “out of sorts”
54
what is the illness period
- specific disease symptoms are fully present
- patient feels the worst
55
what is the convalescent period
- recovery phase
- patient is healing and returning to normal
56
what are the steps in pathogenesis of infectious diseases
1. entry
2. attachment: pathogen binds to host tissue
3. multiplication: pathogen reproduces at infection site
4. invasion or spread to other parts of body
5. evasion of host defenses: pathogen avoids destruction
6. damage to host tissue: symptoms, disability, death
57
what are the types of human carriers
1. passive carrier
2. incubatory carrier
3. convalescent carrier
4. active carrier
58
what's a passive carrier
someone who carries the pathogen without ever having had the disease
59
what's a incubatory carrier
someone who can spread the pathogen during the incubation period, before symptoms appear
60
what's a convalescent carrier
someone who is recovering from the disease but still carries and sheds the pathogen
61
what's an active carrier
continues to carry and shed the
pathogen
62
what are the types of infection
- localised infection
- systemic infection
- acute infection
- chronic infection
- latent infection
- secondary infection
63
what is a localised infection
infection is restricted to one part of the body
64
what is a systemic infection
infection spreads throughout the body
65
what is an acute infection
infection with rapid onset of symptoms and quick recovery
66
what is a chronic infection
infection with slow onset and slow recovery
67
what is a latent infection
infection in which the pathogen never fully clears after recovery, but remains dormant
68
what is a secondary infection
a new infection that occurs during or after a primary infection (due to weakening of immune system)
69
infectious disease vs microbial intoxication
infectious disease: disease caused by the pathogen itself colonising and multiplying in your body
microbial intoxication: disease caused by toxins produced by microbes outside the body, which are then ingested
70
what are virulence factors
- the tools or strategies a pathogen uses to cause disease
- turn commensal microbes into pathogenic
71
examples of bacterial virulence factors
- promote attachment to host cells via adhesins
- help bacterium to enter host cell via invasins
- damage host cell or tissue
- help bacteria to spread from local infection
- immunopathogenic factors: over-stimulate immune response
- mediate immune evasion
72
examples of biofilm
- indwelling catheters
- artificial valves
- dental plaque
73
what are cytolysins
toxins produced by bacteria that destroy erythrocytes, leukocytes and other cells
74
why do bacteria produce cytolysins
- access to nutrients from host cells
- immune evasion
- bacterial spreading
75
what are immune evasion factors
mechanisms used by pathogens to escape detection or destruction by the host’s immune defences
76
examples of immune evasion factors
- capsules (prevents opsonisation and phagocytosis)
- destruction of phagocytes
- inhibition of phagocyte chemotaxis (moving towards infection)
- inhibition of phagocytosis
- destruction of complement factors
- destruction of immunoglobulins (antibodies)
- intracellular replication (pathogen hides and replicates inside the host cell)
medsci 202
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