A1 - Bacteraemia/Endocarditis Flashcards
What is Bacteraemia?
The presence of viable bacteria in the blood stream
What is Bloodstream Infection?
- Bacteraemia with recognised pathogen plus clinical signs of infection.
- Sometimes used interchangeably with bacteraemia
What is Sepsis?
- Life-threatening organ dysfunction caused by a dysregulated host response to infection
- Infection with evidence of organ dysfunction
Bacteraemia can be in sterile sites and non-sterile sites?
What is the difference?
Sterile sites: No resident bacteria; isolation of any bacteria from these compartments is significant. These should be taken seriously
Non-sterile sites: Host to multitude of organisms of varying pathogenicity; isolation may represent colonisation only. Represents colonisation. Commnesal
Examples of bacteraemia in sterile sites?
- Blood
- Central nervous system
- Pleural, peritoneal, pericardial, synovial fluid
- Bone marrow
Examples of Bacteraemia in non-sterie sites?
Lower intestine
- Urinary tract
- Skin
- Oropharynx/upper-respiratory tract
Name some common microorganisms that cause bacteraemia?
Why is it important to treat bacteraemia?
There is high risk of progression to sepsis.
Delay in appropriate antibacterial treatment associated with rapidly increasing risk of death
Classificaiton by site
What is the difference between extravascular and intravascular infections?
Extra: Infection located outside of the cardiovascular system. Indirectly goes through the lymphatic system and causes bactraemia
Intra: Infection located inside the cardiovascular system
How can intravascular infection be further classified?
Vascular Infections - infection of the blood vessels. less common but very serious.
Intravascular catheter related infection- MC
Infective endocartitis
Bacteraemia
Common source of infection?
Other sources of bacteraemia can be transient causes
Think of some examples?
- Flossing, dental procedures, other activities of daily living…
- Tooth brushing – approx. 20%
- Flossing – approx. 20%
- Partuition – approx. 10%
- Defaecation – approx. 5%
WHat are the different patterns of bacteraemia?
How do you diagnose bacteraemia?
Through blood cultures (venous sample)
Blood cultures essential for the diagnosis of bloodstream infection (BSI).
2 blood cultures in __-hr will detect ~90% of BSI; __ sets may be needed to detect >99% of BSIs.
Sample prior to antibiotics if possible to maximise yield. Sampling using strict aseptic technique to avoid _____________.
Blood cultures essential for the diagnosis of bloodstream infection (BSI).
2 blood cultures in 24-hr will detect ~90% of BSI; 4 sets may be needed to detect >99% of BSIs.
Sample prior to antibiotics if possible to maximise yield. Sampling using strict aseptic technique to avoid contamination.
When can you get a false positive blood culture?
How do you prevent this?
WHen you get a blood culture, the neddle goes through the skin. Microorangisms might be on the skin that enter through the needle which would show you a positive result when actually they arent in the blood.
strict non touch aseptic technique to avoid contamination
What happens after taking a blood sample (bacteraemia)?
- at the bottom of the blood culture bottle there is a pH sensor which can cause a change in colour
- they enter automated machines (silos). these will detect whether they are positive or negative.
- then you take a sample and do a gram stain
- place it in an agar plate. Where there is a high inhibition zone the better/effective the antibiotic
you have two bottles of blood culture
Why?
one bottle is in aerobic condition
one bottle is in anaerobic conditon
Think carefully before dismissing positive blood culture as contaminant if patient at risk for infection with skin flora organism
Examples are?
e.g. prosthetic heart valve, long-term vascular access device
What is the pattern of bacteraemia?
Transient bacteraemia: • Lasts minutes or hours. • Usually secondary to a procedure at a non-sterile site e.g. gastric biopsy, toothbrushing.
Intermittent bacteraemia: • Can occur from infections such as abscesses, also osteomyelitis, pneumonia. EXTRAVASCULAR
Persistent bacteraemia: • Usually an intravascular infection e.g. Infective Endocarditis, vascular graft infection. • Sometimes also early stages of systemic infections e.g. Salmonella Typhi
What antibacterial treatment should you use?
Start SMART Empirical treatment based on suspected source of infection or broadspectrum cover if source unknown. Aim to cover likely spectrum implicated pathogenic bacteria. Consider: severity of illness; risk of resistant organisms (treatment and travel history)
Then FOCUS Targeted treatment: Narrowest spectrum antimicrobial, with confirmed effectiveness against isolated organism(s), able to penetrate site of infection. May initially modify treatment based on Gram stain before selecting definitive treatment based on susceptibility results.
What is infective endocarditis
Infective endocarditis, also called bacterial endocarditis, is an infection caused by bacteria that enter the bloodstream and settle in the heart lining, a heart valve or a blood vessel. IE is uncommon, but people with some heart conditions have a greater risk of developing it
Patho of Infective Endocarditis?
- arises when there is structural heart abnormality that affects cardiac valves
- this can be caused by things like congenital heart disease, accquired heart disease, ASD, VSD
- Endocardial injury will lead to
- platelet deposition/aggregration and eventually cause fibrin matrix
- Microbial ahesion
Infective Endocarditis: Risk factors
For Endocardial Damage
Congenital heart disease
• e.g. Bicupsid valves, ventricular septal defect, Tetralogy of Fallot
Acquired heart disease
• e.g. Rheumatic heart disease, degenerative valve disease, prior endocarditis
Intracardiac prosthetic material
• Valve replacements, pacemakers, defibrillators
