Forensic biology - Bacteria: disease and antibiotics

?
  • Created by: aarafa11
  • Created on: 01-06-20 22:02
Virulence Factors include
Pili for adhesion to cells, tissues and surfaces; Enzymes to evade host’s defences Toxins;; The capsule
1 of 62
after bacteria invades/enters/attached host cells, what is next?
infection & colonisation
2 of 62
what are the adhesion factors
Proteins or glycoproteins; Found on end of Fimbriae – attachment pili; Often adhere to receptors on host cells surface; Adherence to specific tissues – lining of lungs, GI tract, GU tract, etc.
3 of 62
Spreading factors
digestive enzymes; Breakdown tissues and allow rapid invasion; And disease
4 of 62
type of digestive enzyme used to spread disease
hyaluronidase ; collagenase
5 of 62
what does hyaluronidase do
Breaks down hyaluronic acid, an important part of the extracellular matrix
6 of 62
what produces hyaluronidase
Streptococci
7 of 62
what does collagenase do
– break down collagen; Allowing bacteria to invade between cells; Necrotizing fascitis – highly virulent form of Streptococcus pyogenes; Can invade tissues at a rate of 2.5 cm h-1
8 of 62
how pathogens invade through basement membrane
reach epithelial surface; produce hyaluronidase; invade deeper tissue;
9 of 62
how pathogens invade through blood vessesl
produce coagulase; blood clot forms around pathogens; produce streptokinase - dissolving clot and release bacteria
10 of 62
types of toxins
Endotoxins and Exotoxins
11 of 62
where are endotoxis released
Released into bacteria’s environment; Often released when bacteria die or divide
12 of 62
what does endotoxins do
Generally induce the same symptoms, e.g. fever and aches
13 of 62
examples of endotoxins
lipid A and lipopolysaccharides (LPS) complexes of gram –ve bacteria
14 of 62
what produced exotoxins
both Gram +ve and –ve bacteria; generally specific to a particular bacterial species
15 of 62
where is exotoxins released
bacterial cell
16 of 62
what are the symptoms of exotoxins
Very high potency, amongst the most toxic substances to man
17 of 62
which is more potent between exotoxins and endotoxins
exotoxisn
18 of 62
how much heat can exotoxins and endotoxins withstand
ENDO)Relatively heat stable – withstand several hours at 60 oC; EXO) Often Denatured by heat and proteolytic enzymes
19 of 62
what is the mode of action for exotoxins
SPECIFIC - affected by cell signalling; Pore forming toxins (‘punch’ hole in plasma membrane); AB toxins (two part toxins); Enzymes
20 of 62
how is exotoxins affected by cell signalling
Directly affects signal receptors; Altered cell membrane permeability to Ca2+; Increased in production of cAMP
21 of 62
how does Pore forming toxins (PFTs) attack the membrane
Proteins form pores on host membrane; Alter permeability of membrane; Leads to ions K+, amino acids and other small molecules leaking out; & others leaking in, (Ca2+, water); Diverse cellular responses – death, senescence, activation of signal cascad
22 of 62
how does virulence factors of Pore forming toxins (PFTs) Contribute to pathogen growth and colonisation
Disruption of epithelial barriers; Avoidance of host immune system; Facilitaing invasion of cells; Release of nutrients; Eliminate competing bacterial species
23 of 62
how does Pore forming toxins (PFTs) work
Toxin receptor on cell membrane; PFT protein Binds to receptor; Another PFT protein is recruited; Oligomerisation;reveals hydrophobic surface; insert pft comp into plasma; trans membrane formed; pore alters permiability=leaks;
24 of 62
examples of exotoxins
Leukocidins & haemolysin & Clostridium perfringens β toxin
25 of 62
what is Leukocidins
virulence factor and Pore forming toxins (PFT)
26 of 62
what does Leukocidins do
Damage neutrophil and macrophage white blood cells (WBCs); Both types of WBC are phagocyctic and leukocidins most effective after the fact; Release cells own lysosomal enzymes
27 of 62
what is haemolysin
lysis blood cells by forming channels
28 of 62
what does haemolysin do
Important in nutrient acquisition
29 of 62
what is Clostridium perfringens β toxin
channel forming toxin that forms a small pore
30 of 62
what does Clostridium perfringens β toxin do
Pore allows efflux K+ and influxes of Ca2+, Cl− and Na+; PFTs differ between species, but pathogenic species tend to have several PFTs in their arsenal
31 of 62
what is AB toxins
exotoxins; 2 part protein; A) active toxin; B) binding protein
32 of 62
what is the purpose of the binding protein in AB toxin
to get A into the cell
33 of 62
What is the role of AB toxin
Target of diphtheria toxin- Translation elongation factor 2 (EF2); Release tRNA from the binding site on ribosome to make way for the next tRNA; Inactivate EF2 & translation, thus, protein synthesis stops
34 of 62
what does Shiga toxin do - exotoxin
acts by cleaving sub-units of the ribosome; no translation; Exploits the difference between prokaryotic and eukaryotic ribosomes
35 of 62
what does botulinum toxin (Clostridium botulinum ) do
Inhibits secretion of the neurotransmitter acetylcholine (Ach); Cleaves SNARE protein on Ach containing vesicles; Switching off nerve impulse, causing gradual paralysis and death
36 of 62
what does tetanospasmin toxin (Clostridium tetani) do
cleaves SNARE but of vesicles containing the inhibitory neurotransmitters GABA and glycine; Motor neurons increase rate of firing, resulting in muscle contraction – lock jaw
37 of 62
what are the type of SNARE protein cleavage
tetanospasmin toxin (Clostridium tetani); botulinum toxin (Clostridium botulinum )
38 of 62
how can some exotoxins be enzymes
Can act catalytically; Some have a broad cytotoxic activity; Phospholipases, cleave the phospholipids of the cell membrane
39 of 62
how is antibodies a chemotheraputic drub
Selectively kill prokaryotic cells, but have a far lower toxicity to eukaryotic cells
40 of 62
how does antibodies Exploit the fact that prokaryotic and eukaryotic cells have differences
Peptidoglycan cell wall; Ribosomes with a different structure to eukaryotes
41 of 62
Examples of β-lactam class Anitibiotics
penicillins & cephalosporins, generally most effective against Gram +ve bacteria
42 of 62
where was β-lactam class Anitibiotics extracted
fungi, e.g. Penicillin sp
43 of 62
what is β-lactam class Anitibiotics
Irreversible inhibitors of the enzyme peptidoglycan transpeptidase
44 of 62
what does β-lactam class Anitibiotics so
catalyses the formation of peptide bridges between peptidoglycan polymers; stops cell wall formation & therefore bacterial growth; weakens existing cell wall
45 of 62
why is it bad if β-lactam class Anitibiotics weaken existing cell wall
Gram +ve bacteria have a high osmotic pressure compare to body fluids
46 of 62
What is not affected by first generation β-lactam antibiotics
Gram -ve bacteria
47 of 62
why isn't Gram -ve bacteria affected by first generation β-lactam antibiotics
Outer membrane prevents the antibiotic reaching the cell wall;
48 of 62
what is the purpose of broad spectrum antibiotics
Exploit differences between bacterial and mammal ribosomes
49 of 62
how does antibodies create action against translation
Principally effecting tRNA binding and ribosomal enzymes that form peptide bonds between amino acids; But still get resistance
50 of 62
Two modes of action of antimetabolites
Competitive inhibitors of enzymes; Incorporated in biochemical in place of normal metabolite
51 of 62
which group of antibodies inhibit nucleic acid synthesis
rifamycin
52 of 62
where is rifamycin found
Fist isolated from soil bacterium Amycolatopsis rifamycinica
53 of 62
how does rifamycin inhibit nucleic acid synthesis
Bind to bacterial RNA polymerase with high affinity; And thereby inhibiting mRNA synthesis
54 of 62
problem with rifamycin inhibit nucleic acid synthesis
Have low affinity for mammalian RNA polymerase
55 of 62
why is rifamycin inhibit nucleic acid synthesis useful
treatment of mycobacteria
56 of 62
why is antibodies resistant
Enzymic deactivation of the antibiotic; Pumping the antibiotic out of the cell; Suppressing the antibiotic with specific proteins; Altering the shape of the target molecules; Altering membrane permeability to prevent entery
57 of 62
how does bacteria deactivate antibodies
use enzyme β-lactamase to cleave β-lactam ring
58 of 62
what should you know about β-lactamase inhibitors
used to over come Penicillin resistance
59 of 62
Transmission of antibiotic resistance genes
R plasmid; Antibiotics (mis)use naturally selects for bacteria with resistance genes; X10 the quantity of antibiotics used in agriculture than used to treat humans
60 of 62
How does the R plasmid transmit antibiotic resistance genes
- contain up to 10 genes linked to antibiotic resistance - Transferred during conjugation - and by Transformation
61 of 62
what does Resistance transfer factor contain
replication function; resistance to lead and mercury; resistance to arsenic antimony;
62 of 62

Other cards in this set

Card 2

Front

after bacteria invades/enters/attached host cells, what is next?

Back

infection & colonisation

Card 3

Front

what are the adhesion factors

Back

Preview of the front of card 3

Card 4

Front

Spreading factors

Back

Preview of the front of card 4

Card 5

Front

type of digestive enzyme used to spread disease

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

Biology
See all Biology resources »See all Bacteria: disease and antibiotics resources »