Vascular Infections Flashcards
What is meant by the term “vascular infection”?
There is a source of infection in the heart or vascular system
What is bacteraemia?
How is this different to a bloodstream infection?
Bacteraemia is NOT a diagnosis - it means that bacteria have been detected in the blood
blood cultures are an important infection test
bacteraemia + symptoms/signs of infection = bloodstream infection
What are the 3 different types of bacteraemia?
1. Transient
2. Intermittent
- pneumonia, pyelonephritis, abscess, meningitis
3. Continuous
- endocarditis, mycotic aneurysm, pacing lead infection, infected DVT
When should blood cultures be taken?
Blood cultures are taken when temperature reaches 38oC or above
don’t just sample blood when temp > 38oC, use other features such as confusion
What is the pathogenesis of an intravascular catheter-related bloodstream infection (CRBSI)?
The routes of colonisation and infection are:
- at the time of insertion
- via hub contamination
- haematogenous
- via infusion
What organisms are most commonly responsible for an intravascular catheter-related bloodstream infection (CRBSI)?
- Coagulase negative staphylococci (31%)
- staphylococcus aureus (20%)
- candida (9%)
- enterococci (9%)
- coliforms (13%)
- pseudomonas aeruginosa (4%)
How is CRBSI diagnosed?
Clinical diagnosis is unreliable
CRBSI should be considered in any patient with an intravascular catheter and
- Systemic signs of infection, or
- Bacteraemia or fungaemia
when CRBSI is suspected, what tests are used to diagnose it?
- Clinical signs of infection that resolve on catheter removal
- same organism from at least 1 peripheral blood culture and catheter tip OR
- differential time to positivity (DTP)
paired peripheral and through line blood cultures (same volume, same time) should be sent from all lumens when CRBSI is suspected
What is differential time to positivity (DTP)?
How can it be used to detect CRBSI and what is the main limitation?
Same volume of blood from the lumen and peripheral vein is taken at the same time
growth of microbes from a blood sample drawn from a catheter at least 2 hours before microbial growth is detected int he blood sample from a peripheral vein
using DTP > 2 hours will fail to detect some CRBSIs, but a positive result has a high probability of being CRBSI
What reading for DTP is highly specific for CRBSI?
a DTP > 2 hours is highly specific for CRBSI
What is infective endocarditis?
An infection of the endocardium or devices within the heart
there are vegetations present which contain densely packed bacteria
What types of things should be looked for in a clinical history for infective endocarditis?
Which patients are at high risk?
- Non-specific illness
- lethargy, malaise, night sweats, anorexia, weight loss
- heart failure
- shortness of breath, orthopnea, PND
- results of extra-cardiac foci of infection
- back pain from HVO, stroke, abdominal pain from splenic infarct
particularly in patients with known heart valve disease, pacemaker, prosthetic valve or congenital heart disease
what is meant by “stigmata” when performing a clinical examination of a patient with infective endocarditis?
A physical mark that is characteristic of the disease
What are the clinical signs of infective endocarditis?
How common are they?
- Fevers > 38oC (96%)
- splinter haemorrhages (8%)
- Oslers nodes (3%)
- Janeway lesions (5%)
- Roth spots (2%)
- conjunctival haemorrhages (5%)
- splenomegaly (11%)
- new murmur (48%)
What is the aetiology of infective endocarditis like?
What are Osler nodes?
Red-purple, slightly raised, tender lumps, often with a pale centre
pain often precedes the development of the visible lesion by up to 24 hours
what are janeway lesions?
Non-tender, small erythematous or haemorrhagic macular, papular or nodular lesions on the palms or soles
they are only a few millimetres in diameter
what are Roth spots?
White-centred retinal haemorrhages that are associated with multiple systemic illnesses
How is infective endocarditis diagnosed?
Echocardiography (transthoracic and transoesophageal)
AND
blood cultures - 3 sets taken at different times
(2 sets in severe sepsis)
What is involved in the antimicrobial management of infective endocarditis?
How long is treatment given for and what are the different treatments?
Antimicrobial therapy should be directed towards the pathogens identified by blood cultures
treatment for 4-6 weeks is usually IV, but some evidence for oral switch
usually treatment is fluclocoaxacillin 2g 6-hourly IV for S. Aureus (methicillin-susceptible)
In addition to antimicrobials, what is involved in the non-antimicrobial management of infective endocarditis?
Surgery may be required to:
- replace or repair damaged valves
- remove infection when antimicrobials don’t work
- remove infected devices e.g. pacemaker
- prevent complications like stroke
- drain purulent collections e.g. in spleen or spine
What is a mycotic aneurysm?
Aneurysms resulting from, or secondarily infected by, microorganisms
What is involved in the pathogenesis of mycotic aneurysm?
- Haematogenous seeding (e.g. secondary to IE)
- trauma to arterial wall + direct contamination (e.g. IVDU)
- extension from a contiguous infected focus
- secondary to septic microemboli (e.g. secondary to IE)
What is the presentation of mycotic aneurysm like?
Usually systemic symptoms of infection and variable symptoms from aneurysm, depending on the location
- no localising symptoms
- painless swelling
- painful swelling
- symptoms caused by rupture (e.g. intracerebral haemorrhage, collapse)
What organisms tend to cause mycotic aneurysm?
- Salmonella spp
- staphylococcus aureus
- streptococcus spp
- pseudomonas aeruginosa
- escherichia coli
What is involved in the diagnosis and management of mycotic aneurysm?
Diagnosis:
- imaging (e.g. USS) and detection of bacteria within tissue
Management:
- surgical removal
- stenting or coiling (depending on location) with antibiotics
What is an infected deep vein thrombosis?
DVTs can be seeded with bacteria during bacteraemia or directly
e.g. IVDU injecting into femoral vein, seeds femoral DVT
What is the presentation of infected DVT like?
- Symptoms/signs of DVT and systemic infection and/or respiratory symptoms
- when infected thrombus breaks from DVT, it travels via the venous system to the lungs (infected pulmonary emboli)
What typically causes an infected DVT?
It depends on the mechanism, but commonly:
- S aureus
- streptococci
- anaerobes in IVDUs
What is involved in the diagnosis and management of infected DVT?
Diagnosis:
- multiple (3) blood cultures
- confirmation of DVT plus exclusion of other causes
Management:
- antibiotics plus anticoagulation
