Infectious Disease and Bacterial Pathogens Flashcards
(95 cards)
1
Q
How do pathogenic microbes cause infection
A
By gaining a foothold in a particular niche
2
Q
Define colonisation
A
Growth of a microbe after gaining access to host tissue
3
Q
Define pathogenicity
A
The ability of a pathogen to inflict host damage
4
Q
Define virulence
A
The degree of pathogenicity of an infecting pathogen
5
Q
What are the two main reactions to an infectious organism
A
Immune and inflammatory reactions
6
Q
What is immunity
A
Innate or adaptive response to an infectious organism
7
Q
What is an inflammatory response
A
A non specific reaction driven by neutrophil accumulation
8
Q
What are signs of acute infection also signs of (mostly)
A
Inflammation
9
Q
What are the 5 main signs of acute infection
A
Rubor, calor, tumor, dalor and change in function
10
Q
What is rubor
A
Redness due to increased blood flow/ vasodilation
11
Q
What is calor
A
Heat due to increased blood flow/ vasodilation
12
Q
What is a tumor
A
Edema/ swelling due to increased movement of plasma from blood to tissue (capillary level permeability)
13
Q
What is dalor
A
Pain due to localised swelling from tumor formation as fluid stretches the nerves and pain receptors
14
Q
What is a change in function
A
Due to pain, change in tissue structure and usually reduced mobility
15
Q
What are the 4 main methods of adaptive immunity
A
Specificity and memory, humoral immunity, cellular immunity, ADCC
16
Q
Define a specificity and memory method of adaptive community
A
Host mediated response to target with rapid and intense repeat responses
17
Q
Define a humoral immunity method of adaptive community
A
B cells producing antibodies
18
Q
Define a cellular immunity method of adaptive community
A
T cells which attack intracellular pathogens
19
Q
Define a ADCC method of adaptive community
A
Antibody dependent cell mediated cytotoxicity
20
Q
What is bacteraemia
A
The presence of bacteria in the bloodstream leading to mass organ dissemination
21
Q
What is sepsis
A
Extreme, system-wide inflammatory response to blood poisoning
22
Q
What is systemic shock
A
A systemic drop in blood pressure leading to mass organ failure
23
Q
Where do pathogens reside in nature
A
Environmental, zoonotic and human
24
Q
What are the 4 types of diagnostic media in culture diagnostics
A
General purpose media, enrichment, selective and differential
25
What is general purpose media
Non-selective media that establishes growth, often a starting point to look for unexpected organisms
Uses LB agar and contains yeast extract, salts, water and agar
26
What is enrichment media
Selective media for certain species, which allows the causative organism to grow faster, Dependent on the symptoms and sample site
e.g. For fastidious (fussy) bacteria, often supplement media with sheep’s blood
•In a mixed sample this allows the causative organism to grow faster
27
What is selective media
Media that grows only certain bacteria to grow
28
What is differential media
Media that selects between two bacterial species and tests for the presence/ absence of enzymes for diagnosis
Enables identification of different organisms on the same plate based on biochemistry
29
What are pathogenicity or virulence factors
Structures, molecules or regulatory systems that enable the disease process
30
What drives pathogenicity/ how does a microbe become a pathogen
Adhesion to epithelial surfaces or invasion of underlying tissue
31
What two ways can pathogens adhere to mucosal surfaces
Subvert host cell function (extracellular) or invade underlying tissue (invasive) during pathogenesis
32
What is the function of polysaccharide capsules
Physical barriers to physical and immune stress (defence against immmune recognition and phagocytosis)and aid adherence and a precursor to biofilm formation
33
What is the bacterial capsule
A key virulence determinant that is a polymer composed of repeating sugar units that encase the bacterial cell for resistance against the immune recognition ect.
34
What is the bacterial capsule an important precursor of
Biofilm formation
35
What is the function of cell surface appendages on bacteria
Promote interaction with surfaces and Maintain a favourable niche via offering physical defence, nutrition, intracellular communication and exchange of genetic material
36
What is a biofilm
Multiple, symbiotic bacterial species living in parallel , default mode of bacterial growth in nature
37
What are fimbrae
Filamentous, cell surface protein structures that are capped by sugar binding, lectin-like proteins and have a high affinity for sugars on cell surfaces
38
What is FimH
Type 1 Fimbriae with CUP type adhesion, typically found on Gram -ve bacteria,has a specific affinity for mannose (sugar)
39
What is the fimbrial catch-bond theory
A mechanistic benefit in natural environments that explains how bacteria can bind more strongly under shear stress
At low shear stress bacteria bind, as stress increases so does the affinity for the groups they bind to enabling bacterial adhesion under mechanical stress.
Strength of binding is dictated by an allosteric switch in the FimH-sugar interaction
40
What are the two general pathways of transport across the inner membrane of bacteria for protein secretions
SEC transport and TAT transport
41
What is the SEC transporter
Unfolded proteins, common transport pathway that facilitates insertion of proteins into the inner membrane
42
What is the TAT transport pathway
Folded proteins/elusive substrates
43
How do bacterial toxins cause damage damage to host cells/tissue
Gain Access to tissue and nutrients and cause damage which facilitates transmission and enhances other virulence processes distal to infection site
44
What is ADME
Absorption, Distribution, Metabolism, Excretion (the 4 stages that occur when a chemical is inside of us)
45
What is absorption
Transfer of an exogenous compound e.g. toxin from site of administration into systematic circulation
46
What is distribution
Translocation of a compound or toxin through systematic circulation to the tissues and organs
47
What is metabolism
Chemical transformation of compounds and toxins to usually less toxic, larger and water soluble forms to aid excretion
48
What is excretion
The exclusion of the compound, toxin or metabolite form cells, tissues and organs or the whole organism
49
What is toxicokinetics
Toxins in motion e.g. ADME
50
What is toxicodynamics
Toxins in action e.g. binding, cellular changes
51
What are endotoxins
Bacterial toxins that are only released if the bacterial cell dies and releases its cellular contents
52
What are exotoxins
Toxins that are secreted by bacteria and bind to specific receptors to disrupt cellular processes. Can also migrate from the site of bacterial colonisation
53
Which part of the respiratory tract has an abundant microbiome which is therefore often asymptomatic due to colonisation resistance with respiratory infection
Upper respiratory tract
54
What are the 3 main causes if Gatroenteritis/ gut infections
Bacterial, viral and parasitic
55
What are Escherichia coli
Gram -ve bacteria present normally in the mammalian gut with a diverse array of pathotypes that can evade the intestines and urinary tract ect.
56
What is intestinal pathogenic E.coli
Pathogenic bacterium associated with beef and leafy greens that encodes a shiva toxin
57
What is Vibrio Cholerae
Gram -ve, comma shaped, motile bacterium associated with aquatic reservoirs, that results in massive loss of fluid via ctx activity and is a facultative anaerobe
58
What is Helicobacter pylori
Gram-ve, motile, spiral bacterium that is largely asymptomatic however can lead to severe stomach pain and is an aetiological agent gastric and peptic ulcers
59
Describe features of UTI and bloodstream infections
Adapted gut colonisation with specific virulence and fitness factors that promote UTI and bloodstream dissemination and can lead to sepsis e.g. E.coli
60
Describe features of skin infections
Mostly due to opportunistic pathogens that cause skin lesions and inflammation, often gram +ve bacteria e.g. staphylococcus
61
What is the main source of vibrio cholerae
Faecal organism that enters GI tract via faecal-oral route by contaminated water or food
62
What are the symptoms of V.cholerae infection
Acute diarrhoea, vomiting, lower leg cramps
63
What adaptations does V.cholerae have enabling it to reach the epithelial cells of the GI tract
- withstand low stomach pH
- motile so can transverse mucus layer to reach epithelial surface of intestine
64
What is an AB toxin
A toxin composed of an A and B subunit
65
What is the A subunit
Catalytic subunit
66
What is B subunit
Cell binding subunit
67
What is Cholera toxin/CT
An AB toxin produced by the O1 and O139 serotypes
68
How does the cholera toxin cause mass water loss
Refilled in ER and released into the cytosol as the A subunit and binds to the G protein, which locks it in the GTP configuration, resulting prolonged adenylate cyclase activation and PrK activation triggering mass water loss and electrolyte loss
69
What is STEC
Shiga toxin producing E.Coli
70
What are the sources of STEC
Ruminants, animal manure (contaminate food chain)
71
What is the shiga toxin
AB toxin released when STEC attaches to the the enterocyte
72
What does the shiga toxin cause
Inhibition of protein synthesis and thus cell death , effacement of villi and can migrate to other organs e.g kidney and CNA
73
How does the shiga toxin inhibit protein synthesis
A subunit is released into the cytosol where it removes adenine from the 28s RNA in the larger ribosome subunit, blocking amino acyl tRNA in protein synthesis
74
How is the shiga toxin linked to Haemolytic uraemia syndrome
Shiga toxin causes damage to capillary endothelial cells in kidney, thrombin and fibrin accumulate, plasminogen activator inhibitor increases which blocks fibrin degradation resulting in clotting and renal failure
75
What is clostridium botulinum
Gram+ve bacterium that is spore for,img and an obligate anaerobe that releases Botulinum toxin
76
What is Botulinum toxin
AB toxin that causes flaccid paralysis in muscle cells
77
What are the main exposures of C.Botulinum
Ingestion of contaminated food, inhalation of spores or direct inoculation of wounds
78
How does BT cause muscle paralysis
BT degrades the snare proteins so synaptic vesicles cannot fuse with synaptic cleft, so ACh is not released , so paralysis
79
What is the difference between virulence and pathogenicity
Pathogenic is qualitative, virulence is quantitative
80
What is a T3SS required for
required for epithelial attachment (EHEC) and in some cases invasion
81
What is a T6SS required for
T6SS – Used for inter-bacterial warfare as well as host-cell subversion
82
What is T4SS required for
T4SS – primarily involved in genetic exchange (conjugation)
83
What are the differences between exotoxins and endotoxins
Exotoxins are more serious and are secreted proteins that have Cytotoxin, Enterotoxin, Neurotoxin, superantigen mode of action with high toxicity
Endotoxins are Lipopolysaccharides that cause fever, vomiting and diahhorea with weak toxicity
84
How do pathogens cause disease
Exposure, adherence, invasion through epithelium,colonisation, toxicity or further invasiveness, damage/ disease
85
What are examples of bacteria that cause disease in the respiratory tract
Mycobacterium tuberculosis and legionella pneumophila
86
What are examples of bacteria that cause gut infection
E.coli, v.cholera, h.pylori
87
What is the most common e.coli serotype
O157:H7, encodes shiga toxin
88
What are examples of systematic infection
Bacteraemia, sepsis and systemic shock
89
Why us diagnosis key
Determines whether it is an infection or other cause and determines where it is resistant to antibiotics
90
How are patients typically diagnosed
Rapid testing by antibody assay, antigen assay and molecular assay
91
What are the 4 steps of biofilm formation
1) adsorption
2) irreversible attachment
3) growth and division
4) mature macro colony
92
What is bacterial protein secretion
The process of how bacteria get proteins inside our body
93
Describe protein secretion in gram+ve bacteria
1 membrane so one step secretion
94
Describe protein secretion in gram-ve bacteria
Either one step (both membranes) or two steps with SEC translocation out of the inner membrane and a specific secretory system for outer membrane transport
95
What is the oral route of contamination
Exogenous compounds Exeter orally and are absorbed by the small intestine
