Session 3 Lecture Notes Flashcards by Alex Roy

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

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What is the definition of sepsis?

It is a life threatening organ dysfunction due to a disregulated host response to infection

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What is septic shock?

Persisting hypotension requiring treatment to maintain blood pressure despite fluid resuscitation

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What is bacteraemia?

Presence of bacteria in the blood

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Is sepsis a type of infection?

NO!!!!

It is a response to infection

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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

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What are the Six sepsis bundle?

Oxygen
Blood culture
IV antibiotics
Fluid challenge
Lactate
Measure urine output

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What should you always do before giving antibiotics?

Take a blood culture

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What is a good inflammatory marker?

C reactive protein

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What is the bacterial pathogen that causes meningococcal meningitis?

Neisseria meningitidis

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How is neisseria meningitidis spread?

By direct contact with respiratory secretions

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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

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What do the pilli on a bacteria do?

Enhance attachment - help the pathogen attach onto host cell

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What does the polysaccharide capsule on a bacteria do?

Help to protect the pathogen from the body’s defence systems

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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

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What does inhibiting fibronolysis do?

Prevents fibrin being broken down

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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

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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

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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

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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

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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

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What is the most common strain of neisseria meningidis in the U.K.?

Group B

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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)

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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)

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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

1. Skin 2. Mucous membranes 3. Bronchial cilia

Give 4 examples of examples physiological barriers

1. Diarrhoea 2. Vomiting 3. Coughing 4. Sneezing

What bacteria in the vagina produces lactic | acid to increase acidity and prevent infection?

Lactobacillus

Give 2 examples of chemical barriers

1. 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

1. 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)

1. Breaching the skin integrity (eg burns, cut, IV lines) 2. Fecal-oral route 3. 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

1. Macrophages 2. Monocytes 3. 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)

1. 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

1. 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)

1. 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

1. Complement proteins (such as C3b) 2. Antibodies (such as IgG) 3. Acute phase proteins (such as CRP)

What are opsonins essential for clearing?

Encapsulated bacteria

Name 3 types of encapsulated bacteria

SHiN 1. Streptococcus pnuemoniae 2. Haemophilus influenzae b 3. 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?

1. 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

1. Tumour necrosis factor a (TNFa) 2. Interleukin 1 (IL-1) 2. Interleukin 6 (IL-6)