POM 10 - Activities of a pathogen 2 Flashcards
what are the 4 components of virulence factors
adherence
invasion
immune evasion
toxins
what are virulence factors
the genetic determinants that allow a pathogen to cause disease
explain the virulence factor of adherence
ability to interact or bind with humor cell
explain the virulence factor of invasion
factors that enable bacteria to find a new niche
explain the virulence factor of immune evasion
avoidance of innate immune system
most important factor
explain the virulence factor of toxins
bacteria release to damage neighboring cells
what is the most important virulence factor
immuen evasion
what is virulence
the ability to cause disease in hosts with intact defences
what does virulence require
some breech of host defences
what is pyrogenic infection - what are the 3 parts to it
tissue invasion, multiplication, and immune response in sterile site
what is granulomatous/chronic infection - what part of the immune system does it evade and what cells are activated to respond to this infection
evade innate immune system
activated macrophages fuse and surround the antigen
incomplete host response = granuloma
what is bacterial intoxication
change in host physiology and tissue destruction
how does cholera cause an infection at a cellular level - 4 steps
infection with vibrio cholerae
cholera divides in bowel and releases a toxin which inhibits GTPase enzyme
cGMP builds up inside cell and causes cell membrane pump to pump Cl- ions out of cell
Cl- Na+ and water is lost in bowel = profuse diarrhoea
what happens at the start of appendicitis
appendix is obstructed with a faecolith
bacteria propogate
how does the bacteria affect the appendix in appendicitis at the cellular level
bacteria interact with cells lining the appendix
bacteria damages cells via toxins/cytolysins
what do the damaged cells release in appendicitis and what is the response to this
damaged cells release chemicals/cytokines which trigger inflammation
immune cells (neutrophil) leave blood vessels and travel to infection site - attracted to cytokine via chemotaxis
E coli can communicate to other cells - explain what this means in terms of appendicitis
when do they communicate, what happens after communication
as resources decrease ecoli bacteria can communicate with other ecoli cells
some ecoli save resources and share DNA with other ecoli
ecoli can then develop into ninja ecoli which can bind to other cells and release toxin that can kill cells
what happens in appendicitis when the immune system repsonds
neutrophils engulf the bacteria via phagocytosis
toxic granules fuse with the phagosome to form lysosome
bacteria are killed within lysosome
how do lysosomes kill bacteria
by generating oxygen free radicals
where is appendicitis pain felt initially and over time - why is this
nerves from appendix enter spinal cord at umbilicus level so initial pain is felt there
over time inflammation spreads to parietal peritoneum which has more precise innervation and pain shifts to right iliac fossa
what are the potential outcomes of appendicitis
2 pathways it can proceed in:
- inflamed appendix is encased by omentum and forms chronic inflammatory appendiceal mass
- appendix bursts -> peritonitis -> sepsis -> death
what are the 4 methods of management for appendicitis
pain relief
fluids
surgery
antibiotics
when are antibiotics given for appendicitis if at all
antibiotics dont do much for appendicitis
can be given peri-operatively to reduce the risk of surgical wound infection but it only reduces risk by small amount
what are the 3 things that streptococcus pyogenes cause
pharyngitis
skin infection/cellulitis
rheumatic fever or glomerulonephrosis following infection
what are the symptoms of rheumatic fever - 5 things
fever
painful joints
connective tissue and heart muscle inflammation
rash
chorea (involuntary random muscle movements)
describe how streptococcus pyogenes causes symptoms/diseases on the cellular level - 5 things
streptococcus pyogenes surface M proteins binds to pharynx cells
innate immune system activates and streptococcus pyogenes toxins damage pharynx cells
M protein resemble human tissue antibodies that form which can cross react
Can react to own tissues as antibodies formed against bacterial proteins sometimes bind to human tissues
antibody binding to human tissue (eg joints/heart etc) causes local inflammation unrelated to initial infection site
bacteria cell wall is made up of what? what is the bacteria cell wall structure
repetitive carbohydrate blobs - NAM and NAG - which dont have good 3D structure
5 amino acids (peptide chain) hang off side of NAG - 5th aa is removed when 2 NAG peptide chains link
cross linking between peptide chains gives it structure
what is the difference between gram + and gram - bacteria at the cellular level
gram + bacteria = thick cell walls made of many carbohydrate chains
gram - bacteria = one layer of carbohydrate making up cell wall
what facilitates the cross linking of peptide chains in the bacterial cell wall
transpeptidase
how does penicillin work in regard to the bacterial cell wall
penicillin binds to transpeptidase so that bacterial cell wall cannot maintain its integrity and falls apart
