Bloodstream Infections Flashcards
What is bacteraemia?
Presence of bacteria in the blood
How do microbes gain access?
Via portal of entry
What can bacteraemia lead to?
Systemic infection
Haematogenous disease
What haematogenous disease can bacteraemia lead to?
Endocarditis
Osteomyelitis
Organ infections
Meningitis
What is septicaemia?
Bacteraemia and symptoms of systemic infection
What are symptoms of systemic infection?
Pyrexia Chills Rigors Hypotension Shock Multiple organ failure
What is sepsis?
Life-threatening condition where body’s response to infection injures tissues and organs
What is sepsis assessed by?
Sepsis-related organ failure assessment (SOFA) score
Measures function of major organs
What is septic shock?
Subset of sepsis where underlying circulatory and cellular/metabolic abnormalities are profound enough to substantially increase mortality
What is the treatment of sepsis?
Give oxygen (94%)
Take blood cultures
Administer empiric IV antibiotics
Measure serum lactate and send full blood count
Start IV fluid resuscitation
Commence accurate measurement of urine output
What are the effects of cytokine storm?
Inflammation
Shock
Multiple organ dysfunction syndrome
Death
What is the mortality rate of sepsis?
35%
What is the primary cause of death from infection?
Sepsis
What percentage of worldwide communicable disease deaths is due to sepsis?
Approximately 50%
What are the negatives of antibiotic therapy?
Increases costs
Causes side effects
Complicates diagnosis
What are the leading causes of Sepsis?
Escherichia coli
Staphylococcus aureus
How does E. coli infect a patient to lead to sepsis?
UTIs via catheters, intestinal lesions, biliary tract infections
Extra-intestinal diseases (extra-intestinal pathogenic E. coli ExPEC)
How does staphylococcus aureus infect a patient to lead to sepsis?
Via abscesses, cellulitis, infected joints, post-operative
What are some other causes of sepsis?
Streptococci (pneumonia, agalactiae, pyogenes)
Salmonella typhi (paratyphi)
Candida
Neisseria meningiditis
How do bacteria survive in the bloodstream?
LPS - resist lysis via complement deposition
Haemolysins
Glycocalyx (capsule/slime layer)
Camouflage by binding IgG in ‘wrong’ orientation
What does protein A in staphylococcus aureus do?
SpA impedes phagocytosis by binding the Fc component of immunoglobulin
Mutants of S. aureus lacking SpA means what?
More efficient phagocytosis in-vitro
Diminished virulence
Lost cloak of invisibility
What does fibronectin binding protein do?
Tethers the bacteria to the endothelium lining
What is infectious endocarditis caused by?
Bacteraemia after medical/dental procedures and colonisation of damaged heart valves
Where can infectious endocarditis spread to?
Brain, lungs, kidneys, or spleen once form clots that break off
What bacteria is responsible for infectious endocarditis?
Viridans streptococci (oral flora) e.g. Streptococcus oralis
Staphylococcus aureus
HACEK group organisms
What are the pathogenicity factors in endocarditis?
Clumping factor (fibrinogen binding protein) Fibronectin binding protein
What are some conditions of immunocompromised patients?
Transplant related immunosuppression Cancer AIDS Congenital problems Splenectomised patients
What bacteria commonly cause infections to immunocompromised patients?
Low-virulence opportunistic pathogens C-N streptococci Listeria spp Candida spp Aspergillus spp
Which drugs are used for effective eradication for immunocompromised patients?
Cidal antimicrobials
How is antibiotic susceptibility testing carried out?
Give provisional result
Use media and incubation appropriate to target
Confirm with purified cultures
