Microbiology 8 Flashcards
1
Q
lower respiratory diseases killed how many people in 2016?
A
3 million
2
Q
diarrhoeal diseases killed how many people in 2016?
A
1.4 million
3
Q
in developed countries ….% of hospital patients encountered …. infection
A
5-12
nosocomial
4
Q
risks are determined by individual susceptibility and are multifactorial.
give examples of these?
A
- genes
- previous exposure
- age
- chronic illness
- medicines
- surgery
- malnourishment
5
Q
what is the highest cause of deaths in high-income countries?
A
ischaemic heart disease
6
Q
what is an endemic?
A
an infection present in a population which is maintained constantly with no external input
e.g. chickenpox
7
Q
what is an epidemic?
A
an infection which rapidly spreads in a short time period (usually < or equal to 2 weeks/less)
e.g. ebola
8
Q
what is a pandemic?
A
an epidemic which has spread across a large region (multiple continents/ globally)
e.g. spanish flu, black death, 2009 H1N1 influenza pandemic
9
Q
what is pathogenicity?
A
ability of a pathogen to produce an infectious disease in an organism
10
Q
what is virulence?
A
relative degree of damage done by a pathogen/ degree of pathology caused by a pathogen
11
Q
where does colonisation of a niche happen?
A
in host
12
Q
what is immunoevasion?
A
evasion of hosts immune response
13
Q
what is immunosuppression?
A
inhibition of hosts immune response
14
Q
where do pathogens obtain nutrients from?
A
host
15
Q
what are obligate pathogens?
A
a microorganism that has to cause disease to be passed between hosts and must infect host in order to survive
e.g mycobacterium tuberculosis
16
Q
what is an opportunistic pathogen?
A
a commensal/non harmful microorganism that can cause disease when hosts resistance is low
e.g. Candida albicans, staph aureus, pseudomonas aeruginosa
17
Q
commensal microorganisms?
A
- part of normal flora
- usually non-pathogenic
- some = pathogenic but unable to enter disease process
- lack ability to attach suitable surface
- held in check by other organisms
18
Q
how can commensal microorganisms prevent disease?
A
- block attachment sites
- produce antimicrobial products as part of normal metabolism
19
Q
when can commensal microorganisms cause disease in humans?
A
- microbial balance is upset (after antibiotic treatment)
- microbes get to places where shouldn’t be (blood stream infections)
- host community compromised
20
Q
what are the waterborne sources of disease?
A
- cholera
- typhoid
- legionella
21
Q
what are the food borne sources of disease?
A
- salmonella
- campylobacter
- e.coli
22
Q
what are sources of disease on surfaces?
A
norovirus form
23
Q
what are the sources of disease in soil?
A
- clostridium botulinum
- c tetani
24
Q
what are the sources of disease in bacteria?
A
- anthrax
- e.coli
- plague
25
what are the sources of disease in parasites?
toxoplasmosis
26
what are the sources of disease in viruses?
- avian influenza
- CCHF
- ebola
- Rift Valley fever
27
what are the other sources of disease in animals?
BSE
28
what are zoonoses?
infectious diseases that can = naturally transmitted between non-humans (usually vertebrates) and humans
29
what can animals act as?
a reservoir (place where agents live)
contribute to development of pandemics
30
what are the occupations that come in close contact with animals/animal products?
- farmers
- tanners
- slaughterhouse workers
31
what other occupations are at a high risk of exposure to infectious agents?
- laboratory
| - healthcare
32
what animal viruses can humans contract?
- bird flu
- H5N1
- H1N1 swine flu
33
what is antigenic shift?
combination of 2/more different strains
- prod new form of virus which shows mixture of surface antigens
34
what is antigenic drift?
accumulation of mutations within antibody binding regions
- reduces effectiveness of immune system
35
when was koch's postulates first described?
1890
36
what is the proof available for koch's postulates?
- plague
- anthrax
- diphtheria
- cholera
- typhoid
37
when is koch's postulate less evident?
- condition = chronic / minor
- condition has multiple causes/pathogens = non - culturable
- no suitable animal model of infection
- agents causing pneumonia, wound infection, UTIs, septicaemia
38
koch's postulate process
1. microorganism must = found in abundance in all organisms suffering from disease (not in healthy organisms)
2. microorganism = isolated from diseased organism and grown in pure culture
3. cultured microorganism should cause disease when introduced into healthy organism
4. microorganism re-isolated from inoculated, diseased experimental host & found as being identical to original specific causative agent
39
updated koch: molecular postulated?
- identify gene responsible
- show that gene is present in disease causing strains of bacteria
(not present in avirulent strains)
- show that disrupting gene reduces virulence
- introduce cloned gene into avirulent strain
(should confer virulence)
(gene expressed in vivo)
- specific immune response to gene protects
40
what 3 stages can disease be broadly split into?
- transmission and exposure
- attachment and invasion
- colonisation and damage
41
describe the disease process?
1. pathogen exposure
2. skin/mucosa adherence
3. epithelia invasion
3. colonisation and growth
4. invasiveness (further growth at original/other sites) & local/systemic toxicity
5. tissue damage and disease
42
what is transmission?
passing of communicable disease from infected host to particular individual/group, regardless of whether other individual was previously infected
43
give an example of vertical transmission?
mother to child e.g. HIV
44
give an example of horizontal transmission?
person to person transmission e.g. chlamydia
45
what is vehicle borne transmission?
transmission through inanimate object
46
what is vector borne transmission?
transmission through another organism e.g. malaria
47
what disease can be vertical, horizontal or vehicle borne?
HIV
48
what routes does horizontal exposure tend to be?
- inhalation
- ingestion
- contact
49
what does successful exposure depend on?
- microbe count: more = better
- airborne: size, density, surface features
- waterborne: density, surface features hydrophobicity
- contact: environmental persistence (imp in hospital acquired infections)
- distribution on host: into cuts, digestive system, GU system, lungs..
- vectors
50
what does attachment and invasion depend on?
surface break / on active microbial procedures
51
virulence factors play an important role in what?
- pili/adhesins (aid attachment to cells)
- capsules (resist phagocytosis)
- enzyme production
52
what does a biofilm comprise of?
any group of microorganisms in which cells stick to each other and to surface
53
are biofilms naturally occuring?
yes
54
an estimated … of infections involve biofilms
80%
55
what do biofilms increase?
- average hospital stay
| - resistance to treatment
56
what are biofilms especially important in?
CF
- form within lungs
57
what does growth in tissues require?
cells to resist host responses
- potentially neutralise e.g. enzymes, capsules
58
what does growth also need?
appropriate nutrients
- some tissues have limited (e.g. iron) / specific nutrients which slow/enhance microbial growth
59
host cell death happens as a result of..
- damage
- toxin accumulation
- enzymatic digestion
60
what pathogenicity factors play an important role in colonisation and damage?
- bacterial toxins
- exotoxins
- endotoxins (LPS)
- capsule
- bacterial enzymes
61
microbial toxins promote infection by...
damaging tissue
through endotoxins (LPS) and exotoxins (secreted toxins)
62
endotoxins are part of the bacterial cell membrane.
what can they lead to?
- septic shock
| - highly controlled in sterile pharmaceutical products
63
clostridium difficile produces two main toxins.
what are they?
- toxin A (enterotoxin)
- toxin B (cytotoxin)
play important role in disrupting gut epithelia
64
give an example of another toxin that has found other uses?
- botulinum toxin among most powerful
| - estimated LD50 of 1.3-2.1 ng/kg IV or IM
65
what are the 3 general types of microbial exotoxins based on effect?
- cytotoxins (kills cells)
- neurotoxins (interfere with normal nerve impulses)
- enterotoxins (affect cells lining GI tract)
66
what can these microbial exotoxins be further divided into?
- Type 1 - superantigens
- Type 2 - membrane disrupting toxins
- Type 3 - protein modification
67
Type 1 exotoxins?
- cause intense immune response
- due to nonspecific cytokine release from host cells
produced by some S.AUREUS strains
68
Type 2 exotoxins?
- disrupt phospholipid bilayer
| - make protein channels in PM e.g. cholera toxin
69
Type 3 exotoxins?
- e.g. diphtheria, shiva toxin
- inhibit synthesis
- tetanus toxin cleaves protein involved in neurotransmitter release
70
microbial endotoxins are heat stable.
what does this mean?
difficult to remove from pharmaceutical preparations
71
what portion of LPS is lipid A part of?
toxin portion
72
what is lipid A responsible for? and how?
fever associated with G bacterial infections
- when G cells digested, endotoxins released - causes fever
- if immune system acting on high G- bacterial load, large release of endotoxins trigger septic shock
- antibiotics initially cause fever / shock due to endotoxin release
73
what do haemolysins cause
red blood cell lysis by forming pores in plasma membranes
74
what are haemolysins?
most = proteins
| some are lipid biosurfactants
75
bacteria can be classified on basis of haemolysis.
give the 3 classifications?
- ALPHA - oxidise iron (S. pneumoniae)
- BETA - ruptures RBC (S. pyogenes)
- GAMMA (non-haemolytic)
76
what can haemolysis lead to?
haemolytic anaemia
| - bone marrow can't produce RBC fast enough to replace loss
77
mycoses are diseases caused by fungi
give properties of mycoses?
- persistent (chronic)
- localised/ systemic
- from inhalation of fungal spores
- most common in immunocompromised patients or those taken antibiotics
78
give 3 examples of what fungal diseases include?
- athletes foot
- thrush
- aspergillosis
79
athletes foot
- irritation, dry, inflamed skin with localised pain
| - caused by species of trichophtyon, epidermophyton, microsporum
80
thrush
caused by Candida albicans
81
aspergillosis
- caused by aspergillus fumigatus
| - invasive in immune compromised patients
82
viral diseases can cause communicable and non-communicable diseases.
give examples of communicable diseases?
- herpes
- HIV
- influenza
83
give examples of non-communicable diseases?
- HPV -> cervical cancer
- human adenovirus Ad-36 -> obesity
- mouse mammary tumour virus -> human breast cancer
