Theme 9: Clinical cardio infections: Vascular and CNS Flashcards
What are the two requirements to diagnose bacteraemia?
bacteraemia (bacteria detected in the blood) + symptoms/signs of infection
What are the 3 types of bacteraemia?
- Transient (comes and goes)
- Intermittent: pneunomia, pyelonephritis, abscess, meningitis
- Continuous: endocarditis, mycotic aneurysm, pacing lead infection, infected DVT
What is CRBSI and what are the 4 possible routes of colonisation and infection?
CRBSI - Intravascular catheter-related bloodstream infection
- Exit site –> can become contaminated during time of insertion or whilst handling this part
- Via hub contamination –> if aseptic technique isn’t used
- Haematogenous –> the intravascular portion can be seeded if someone has bacteraemia
- Via infusion –> rarely, but contaminated fusion fluid can result in colonisation of the line
Which micro-organisms can cause CRBSI?
- coagulase negative staphylocci (30%)
- S.aureus
- candida (1-%)
- enterococci (10%)
- coliforms
- pseudomonas aeruginosa
When should a CRBSI diagnosis be considered?
in any patient with an intravascular catheter and,
- Systemic signs of infection, or
- Bacteraemia or fungaemia
How do we diagnose CRBSI?
- Indirect diagnosis - clinical signs resolve on catheter removal
- same organism from at least 1 peripheral blood culture or catheter tip or
- differential time to positivity (DTP)
What is 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
- a DTP > 2 hours is highly specific for CRBSI
What is IE?
Infective endocarditis is infection of the endocardium or devices within the heart
How does a patient with IE present?
- Non specific illness (lethargy, malaise, night sweats, anorexia, weight loss)
- Heart failure (SOB, orthopnea, PND)
- Results of extra-cardiac foci of infection (back pain from HVI, stroke, abdominal pain from splenic infarct)
What are the signs of IE?
- fevers > 38
- spinter haemorrhages
- oslers nodes
- janeway lesions
- roth spots
- congunctival haemorrhages
- splenomegaly
- new murmur
What are the 3 biggest causes of IE?
Staphylococci
Streptococci
Enterococci
How do we diagnose IE?
Echocardiography (transthoracic or transoesphageal US of the heart) + blood cultures (3 sets taken at different times)
Why might surgery be required as a non-antimicrobial management, as well as antimicrobial methods, to cure IE?
- To replace or repair damage valves
- Remove infection when antimicrobials don’t work e.g abscess
- Remove infected devices e.g pacemaker
- Prevent complications like stroke
- Drain purulent extra-cardiac abscesses e.g in spleen or spine
What is a mycotic aneurysm?
aneurysms resulting from, or secondarily infected by, microorganisms
Explain the pathogenesis of a 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
What are the possible causes of a mycotic aneurysm?
- Salmonella spp
- S.aureus
- Streptococcus spp
- Pseudomonas aeruginosa
- E.coli
How do we diagnose a mycotic aneurysm?
imaging e.g USS and detection of bacteria within tissue
How do we manage a mycotic aneurysm?
surgical removal, stenting or coiling (depending on location) with antibiotics)
What is an infected DVT?
•DVTs can be seeded with bacteria during bacteraemia or inoculated directly e.g PWID injecting into femoral vein seeds femoral DVT, infected PICC seeds axillary vein DVT
How do we diagnose and manage an infected DVT?
Diagnosis: multiple (3) blood cultures, confirmation of DVT plus exclusion of other causes e.g IE
Management: antibiotics + anticoagulation
What are the 3 different types of primary infections of the CNS?
- meningitis
- encephalitis
- brain abscess
What is meningitis?
an inflammatory process of leptomeninges (inner two meninges - arachnoid and pia) and CSF
What is meningoencephalitis?
inflammation to meninges AND brain parenchyma
Which 3 ways can we classify meningitis?
- Acute pyogenic: usually bacterial meningitis
- Aseptic: usually viral meningitis, lymphocytic pleocytosis
- Chronic: mycobacterium tuberculosis, spirochetes (neurosyphilis)
What are the 4 ways infectious agents can enter the CNS?
- Haematogenous spread: most common
• Usually via arterial route
• Can be retrograde (veins) - Direct implantation
• Most often is traumatic
• Iatrogenic (rare)
• Congenital (meningomyelocele) - Local extension (secondary to established infections): most often from mastoid, frontal sinuses, infected tooth etc
- Along peripheral nerves
• Usually viruses
Explain the aetiology of acute bacterial meningitis according to age
- < 1 month = streptococcus agalactiae, E.coli, Listeria monocytogenes
- 1-23 months = streptococcus pneumoniae, neisseria meningitidis, E.coli
- 2-50 years = streptococcus pneumoniae, N. meningitidis
- > 50 years = streptococcus pneumoniae, N.meningitidis, listeria monocytogenes, aerobic gram -ve bacilli
What are the clinical features of meningitis?
- Headache
- Irritable
- Neck stiffness
- Photophobia
- Fever
- Vomiting
- Varying levels of consciousness
- Rash
How do we diagnose meningitis?
- blood cultures
- lumbar puncture: CSF for microscopy, gram stain, culture and biochemistry
- EDTA blood for PCR for viruses and bacteria
What is the difference in CSF in normal condition and in bacterial meningitis?
Normal: clear, colourless, 0-5 lymphocytes
Bacterial: cloudy, turbid, 10-2000 lymphocytes, high protein and low glucose
What is viral meningitis?
- primarily affects children and young adults
- milder signs and symptoms
- may start as respiratory or intestinal infection then viraemia
- CSF shows raised lymphocyte count- protein and glucose usually normal
What are the possible causes of viral meningitis?
- Enteroviruses: Echo, coxsackie A, B
- Paramyxovirus: mumps
- Herpes simplex, varicella zoster virus
- Adenoviruses
- Other: arboviruses, lymphocytic choriomeningitis, HIV
Explain the key features of tuberculosis meningitis
- higher incidence in immigrant populations who come from countries with a higher incidence of TB
- insidious onset
- high frequency of complications, cranial nerve palsy
- CSF has high lymphocyte, high protein and normal glucose
What is encephalitis?
an acute inflammatory process affecting the brain parenchyma
What is the most common cause of encephalitis?
Viral infection
90% is caused by herpes virus - HSV-1/2, varicella zooster, cytomegalovirus, EBV
What are the symptoms of encephalitis?
- Fever
- Headache
- Behavioural changes
- Altered level of consciousness
- Focal neurologic deficits
- Seizures
What is the most common cause of sporadic encephalitis in previously healthy people?
herpes encephalitis
What are some features of herpes encephalitis?
- might be evidence of herpes infection on skin, mucosea
- causes severe haemorrhagic encephalitis affecting temporal bone
- focal signs and epilepsy features
- acute infection or commonly reactivation of latent infection (trigeminal nerve ganglion)
How do we treat herpes encephalitis?
acyclovir
What is the criteria for recurrent meningitis?
- > 2 episodes of meningitis
- symptom-free intervals
- normal CSF between episodes
- must be differentiated from chronic meningitis
What is mollaret meningitis?
meningitis due to a viral infection (aseptic meningitis) that occurs multiple times
What is rabies?
- acute, progressive viral encephalitis
- highest case fatality of any infectious agent
- one of the most ancient diseases described
- model zoonosis
How does rabies cause infection?
- Rabies virus enter through bite, grows at trauma site for a week and multiplies, then enters nerve endings and advances toward the ganglia, spinal cord and brain
- Infection cycle completed when virus replicates in the salivary glands
explain the 4 clinical phases of rabies
- Prodromal phase - fever, nausea, vomiting, headache, fatigue, burning, tingling sensation at site of wound
- Furious phase - agitation, disorientation, seizures, twitching, hydrophobia
- Dumb phase - paralysed, disorientated, stuporous
- Progress to coma phase, resulting in death
What is neurosyphillis?
-syphillis infection leading to CNS invasion occurs early in infection in 35% of patients
What are the symptoms of neurosyphilis?
Early form:
- acute meningitis
- meningovascular stroke
Late symptomatic forms (>2 years)
- general paresis
- tabes dorsalis
What is tabes dorsalis?
slow degeneration of the nerve cells and nerve fibres that carry sensory information to the brain
How do we diagnose neurosyphillis?
by blood and CSF serology
What is a brain abscess?
a focal suppurative process within the brain parenchyma (pus in the substance of the brain)
How can a brain abscess occur?
- direct spread from “contiguous” suppurative focus e.g from ear 40%
- haematogenous spread from a distant focus e.g endocarditis
- trauma e.g open cranial fracture
- cryptogenic
Brain abscesses are often polymicrobial (mixed). What pathogens can they be made up of?
- streptococci (70%)
- S.aureus (10%- but most common after trauma/surgery)
- anaerobes
- gram -ve enteric bacteria
other: fungi, mycobacterium tuberculosis, toxoplasma gondii
What is the clinical presentation of brain abscesses?
- Headache (most)
- Focal neurological deficit (30-50%)
- Fever (<50%)
- Nausea, vomiting
- Seizures
- Neck stiffness
- Papilloedema
Why is drainage of a brain abscess the treatment of choice?
- to urgently reduce ICP
- to confirm diagnosis
- to obtain pus for microbiological investigation
- to enhance efficacy of antibiotics
- to avoid spread of infection into the ventricles
How can small brain abscesses be printed?
with antibiotics alone
what do you have to consider when choosing antibiotics for treatment of CNS infections?
penetrations of drugs through BBB and into CSF/ brain tissue is variable
What is the non-antimicrobial drug of choice for meningitis?
dexamethasone
How does coarctation of the aorta lead to hypertension?
- Narrowing of aorta increases pressure at that site
- These are the arteries that branch off to supply the arms, and we take BP from the arms
- But we have low pressure distal to the narrowing
- One of the organs experiencing hypotension will be the kidneys
- Kidneys have a big role at maintaining BP through RAAS - if the kidney senses the BP has fallen, they compensate through the chain of events below
- So the BP increases further
What are the effects of hypertension superior to the coarctation of the aorta?
- headache
- saccular aneurysms
- stroke
- coronary diseases
What are the effects of hypotension distal to the coarctation of the aorta?
- decreased perfusion of the renal
- claudication in the legs
- decreased pulses in the inferior limbs
How can an abdominal aneurysm present?
- ruptured
- pulsatile abdominal mass
- limb ischaemia
- PR bleeding
