Session 3 Lecture Notes Flashcards
What is a purpuric non-blanching rash?
Purpuric = little purple/red dots on skin - small bleeding of blood vessels near skin surface Non-blanching = the spots are fixed / do not go clear when pressed
What is the definition of sepsis?
It is a life threatening organ dysfunction due to a disregulated host response to infection
What is septic shock?
Persisting hypotension requiring treatment to maintain blood pressure despite fluid resuscitation
What is bacteraemia?
Presence of bacteria in the blood
Is sepsis a type of infection?
NO!!!!
It is a response to infection
What is the Early warning score? At what score should patients be reviewed for sepsis?
EWS = basic observations scored such as respiratory rate, heart rate, temp and blood pressure
Anything over 3 = review for sepsis
What are the Six sepsis bundle?
- Oxygen
- Blood culture
- IV antibiotics
- Fluid challenge
- Lactate
- Measure urine output
What should you always do before giving antibiotics?
Take a blood culture
What is a good inflammatory marker?
C reactive protein
What is the bacterial pathogen that causes meningococcal meningitis?
Neisseria meningitidis
How is neisseria meningitidis spread?
By direct contact with respiratory secretions
If a bacteria has a lipopolysaccharide complex what does this mean?
It is an endotoxin = gram negative bacteria
The endotoxin has the ability to promote an intense inflammatory response
What do the pilli on a bacteria do?
Enhance attachment - help the pathogen attach onto host cell
What does the polysaccharide capsule on a bacteria do?
Help to protect the pathogen from the body’s defence systems
Name some examples of cytokines
What do cytokines do?
Tumour necrosis factor
Interleukin 1
Cytokines stimulate the inflammatory response
They lead to activation of the humeral cascade, activation of thrombin and inhibit fibrinolysis
What does inhibiting fibronolysis do?
Prevents fibrin being broken down
What is the major cause of shock and multi organ failure?
Microvascular injury
damage to small blood vessels preventing oxygen and nutrients getting to vital organs
What causes progressive necrosis?
When blood supply becomes compromised - the blood is reassigned to vital organs and some parts of the body will be compromised eg hands and feet
What are some of the life threatening complications of meningococcal meningitis?
- Irreversible hypotension
- Respiratory failure
- Kidney failure
- Raised intracranial pressure
- Necrosis of hands and feet
How can you confirm diagnosis of meningococcal meningititis?
- Blood culture
- PCR of blood - to look for fragments of pathogen
- CSF PCR - as this pathogen
specifically affects cerebral spinal fluid
What type of bacteria is neisseria meningitidis?
Gram negative diplococcus
- it is an endotoxin
- has a lipopolysaccharide outer membrane
- groups of cocci (round shaped)
- stains pink/red on counter stain
- polysaccharide capsule
What is the most common strain of neisseria meningidis in the U.K.?
Group B
What are the 2 preventions you can take for neisseria meningidis?
- meningococcal C vaccine
2. antibiotic prophylaxis (preventative treatment given to those close to infected person)
What 2 factors can determine the outcome of the host pathogen relationship?
- Infectivity (ability to express)
2. Virulence factors (the way the pathogen damages the host)
What is the immune system?
Cells and organisms that contribute to immune defences against infectious and non-infectious conditions
What is an infectious disease?
When the pathogen succeeds in evading or overwhelming the host’s immune defences
Can you have an adaptive immunity without an innate immunity?
NO
The only way the adaptive response will be activated is if dendritic cells do this (if pathogen gets past innate system)
Give 3 examples of physical barriers to pathogens
- Skin
- Mucous membranes
- Bronchial cilia
Give 4 examples of examples physiological barriers
- Diarrhoea
- Vomiting
- Coughing
- Sneezing
What bacteria in the vagina produces lactic
acid to increase acidity and prevent infection?
Lactobacillus
Give 2 examples of chemical barriers
- Low pH
2. Antimicrobial molecules eg IgA, lysozymes and mucus
Where can an endogenous source of infection come from?
From within the body - the normal flora (or microbiota) moving to a location it isn’t normally found
Give an example of a normal flora bacteria found on the skin
What infection can it cause?
Staphylococcus aureas
It can cause cellulitis
Where should the normal flora only ever be found?
On the skin or around points of entry (where there is a mucus membrane)
Never in the blood, organs or tissues
How can antibiotics lead to thrush?
What is the organism that causes thrush - is it endogenous or exogenous?
Antiobiotics can reduce the levels of normal flora Candida albicans (a yeast - eukaryotic cell) is able to multiple and causes a yeast infection (thrush) It is an endogenous source of infection
Give 2 examples of bacteria from the normal flora of the respiratory tract that can cause infection
- Streptococcus pneumoniae
2. Neisseria meningitidis
Give examples of 3 common routes the normal flora can use to get into a sterile location (and cause infection)
- Breaching the skin integrity (eg burns, cut, IV lines)
- Fecal-oral route
- Fecal-perineal-urethral route (eg UTI)
What is the major route in which bacteria from our normal flora gets into the bloodstream?
Poor dental hygiene or dental work
What should be prescribed to asplenic patients?
Antibiotic prophylaxis
What is the body’s way of trying to localise/contain an infection?
Inflammation
Name the 3 main phagocytes
- Macrophages
- Monocytes
- Neutrophils
Which WBC produces cytokines?
Macrophages
What WBCs are recruited by chemokines to site of infection?
Neutrophils
What happens to neutrophils after they destroy bacteria?
They die and form pus
What is the difference between mast cells and basophils?
Mast cells are fixed in the tissue whereas basophils circulate in the bloodstream
What is the function of basophils and mast cells?
They are early actors of inflammation and important in allergic reactions
What is the function of eosinophils?
They defend against multi-cellular parasites (i.e. worms or helminths)
What is the function of natural killer cells?
To kill all abnormal host cells (infected or malignant)
What do dendritic cells do?
Activate the adaptive immune response
They present pathogens to T cells
How do PAMPs help in identifying a pathogen?
They are components that may be present on the pathogen that are not present on the host cell
(pathogen associated molecular patterns - such as carbohydrates, lipids or proteins)
What are pathogen recognition receptors?
Give an example
Example: Toll like receptors
They are receptors on the surface of phagocytes. They recognise the PAMPs on the pathogen - marking it out as a pathogen
What is good about toll like receptors?
They are present on the cell surface of phagocytes as well as inside the cell
This is key for identifying viruses which have to get inside a host cell to cause an infection
Give 2 examples of gram negative bacteria and the pathogen recognition receptor for these (PRR)
- Lipopolysaccharide (TLR4 PRR)
2. Lipoproteins and lipopeptides (TLR2 PRR)
Give 2 examples of gram positive bacteria and the type of pathogen recognition receptors for these
- Peptidoglycan (TLR2 PRR)
2. Lipoteichoic acids (TLR4 PRR)
A phagocyte can recognise all gram negative and positive bacteria using which 2 PRRs? (pathogen recognition receptors)
- TLR2
2. TLR4
What is involved in the opsonisation process?
Coating proteins called opsonins bind to the pathogen surface which enables enhanced attachment for phagocytes
Give 3 examples of opsonins
- Complement proteins (such as C3b)
- Antibodies (such as IgG)
- Acute phase proteins (such as CRP)
What are opsonins essential for clearing?
Encapsulated bacteria
Name 3 types of encapsulated bacteria
SHiN
- Streptococcus pnuemoniae
- Haemophilus influenzae b
- Neisseria meningitidis
When phagocytosed what does the pathogen become fused with?
A lysosome to become a phagolysosome
What 2 pathways have we learnt that are activated by the complement proteins?
Which acts earlier and why?
- Alternative pathway
2. MBL pathway - acts later because the mannose binding lectin has to be produced by the liver in response to infection
What complement proteins act as chemotaxins?
What does this mean?
C3a and C5a - they attract neutrophils and macrophages
What complement proteins act as opsonins?
C3b and C4b
What complement proteins help in the killing process of bacteria by punching holes in the membrane?
C5-C9
Give 3 examples of cytokines
- Tumour necrosis factor a (TNFa)
- Interleukin 1 (IL-1)
- Interleukin 6 (IL-6)
