Bloodstream Infections Flashcards
What is sepsis (definition in man)
Life threatening organ dysfunction caused by a dysregulated host response to infection. body’s extreme response to an infection
Difference between bacteraemia and septicaemia (now sepsis)
Bac: Presence of bacteria in the blood- may have no disease implications/ asymptomatic & transient
Sept: presence of bacteria in blood with clinical symptoms (e.g temp high/ hear. Rate/ respiratory rate ^of septicaemia)
3 types of bacteremia patterns
Transient- cleared rapidly by macrophages- no clinical consequence - dental extraction
Intermittent- in clinical conditions, whether there’s bacteria in blood depends on timing of when blood culture has been taken or whether it has had antibiotics- pneumococcal pneumonia, gram negative sepsis, intra-abdominal abscess
Continuous- continuously in blood; infective endocarditis, catheter bacteria
Is Systemic inflammatory response syndrome (SIRS) specific for infection?
NO
What are SIRS
Where do we get SIRS (Systemic inflammatory response syndrome)
Systemic signs of inflammation
Infection, trauma, burns, surgery, thrombo-embolism, autoimmune disease, chemical poisoning, vasculitis
Sepsis is over or underdiagnosed?
Under-diagnosed
Sepsis real definition
SIRS (systemic inflammatory response) plus infection (documented or clinical suspicion of infection)
What does uncomplicated infection mean
Infection that isn’t sepsis; no systemic features/physiological derangement,localised; confined to the skin or lungs or bladder etc
What is severe sepsis
sepsis induced organ dysfunction or tissue hypo-perfusion- organism are starting to fail due to not enough o2 delivery to tissues
What is septic shock and what’s the major problem with it
Sepsis induced hypotension (fall in blood pressure) not responding to fluid resuscitation- sepsis caused by infection causing low blood pressure, to treat this need to give fluids however with septic shock it doesn’t work because vessels are vasodilated and vasculature is leaky therefore fluid being lost
Causes of sepsis
-Bacteria;gram positive and gram negative and their secreted products e.g toxins they produce
-Fungi- mainly yeasts
-Some systemic & localised viral infections e.g canine parvovirus,influenza,Ebola
-Malaria
Sepsis is a systemic infection. What does it release into blood stream and describe the cycle that this causes
Releases cytokines TNF-a and IL-1 into blood stream which causes loss of blood volume; dilation of veins, blood lost from veins and fluid. In tissues; this leads to physiological derangement i.e coaggulation; leads to clotting factors being used up; leads to bleeding; failure of organs; death.
What is the diamond skin disease
Bleeding/clotting of blood into the skin from the bloodstream infection
Can sepsis occur even when blood bacteria cultures are negative? (No live bacteria in blood). If yes, how?
Yes, it is a severe localised infection of the e.g lung, urinary tract, soft tissue and bacterial components (peptidoglycan, LPS) are released into blood causing clinical symptoms
Difficult or easy to distinguish G-positive from G-neg?
Difficult
Certain bacterial toxins called ________ cause systemic symptoms of shock
Which types of bacteria relaease these toxins?
-superanttigens
-bacteria involved in skin or soft tissues- usually gram positive
The sepsis cascade
Look over this
How does the superantigen (SA) work
Cross links the MHC and T cell receptor; causes massive release of pro-inflammatory cytokines leading to septic shock/toxic shock syndrome
What are host cell pattern recognition receptors (PRRs)
Recognition molecules that are the link between organism and activation of sepsis response in host- toll-like receptors
Recognise structures of pathogen
What bacterial component do each of these toll like receptors recognise?
-TLR-2
-TLR-4
-TLR-5
-TLR-9
- Peptidoglycan,lipoproteins
2.LPS, lipid A - Flagellin
- Bacterial DNA
Viral infections and intracellular bacteria recognised by what kind of receptors?
Intracellular pattern-recognition receptors- not surface receptors
How do the toll-like receptors work (fungi do this as well)
-bind their specific component
-induces a signal transduction cascade which activates transcription factor
-factor induces pro inflammatory cytokines which have the systemic effects of sepsis and septic chock
Which molecule links local/systemic inflammation with acquired immune response?
Macrophages
What do citrates macrophages release?
Cytokine
Severe sepsis & septic shock causes release of physical derangements such as;
Shock
Impaired O2 delivery exchange
Lung damage- lung filled with fluid and starts drowning and leaking resulted by complement activated
Activation of clotting factors; once used up haemorrhage occurs
Where should complement not be active and why?
In tissue as it binds to surfaces, produces membrane attack complex and cells are destroyed
Severe sepsis/septic shock clinical implications
Acute Respiratory Distress Syndrome (ARDS)
Cardiac output initially rises then falls
Hypotension often leads to renal failure
Haematology: ^ white cells, ^ platelets
-Disseminated Intravascular Coagulation (DIC)
-Widespread tissue ischemia & organ failure
-Increased bleeding
What is Sepsis “therapy” and what does it consist of
Maintenance of physiological parameters as close to normal as possible
-Fluid management – maintain arterial and venous pressures
-Respiratory support – oxygen or ventilator
-Renal support
Sepsis is bacterial or viral?
Mostly bacterial but sometimes viral
What is primary viraemia and how does it work
What is secondary viraemia and how does it work
spread of the virus into the blood from the initial site of infection
-clinically silent. Virus acquired that gets into bloodstream and goes to target organ; grown in organ during incubation period
Secondary viraemia is when symptoms of infection start appearing; virus multiplied sufficiently and now gets back into blood stream. Once back causes the physiological consequences of sepsis
