Lecture 15: Endocarditis and Meningitis Flashcards
What is infective endocarditis
An infection of the encardial surface of the heart
What part of the heart is infective endocarditis most involved in
mostly involved in the heart valves, but the wall of the heart may be involved or infected ion may occur at the site of structural defects
It I’d also very common for patients with prosthetic valves and other foreign materials in their valves
Explain how the heart works
The blood comes up the great veins and gets into the right side of the heart and then down into the right ventricle and is pumped out into the pulmonary truck and goes out to the lungs, comes back through the left atrium into the left ventricle and shut out through the aorta
What are considered acute infections in infective endocarditis
Presenting within 6 weeks, often caused by more virulent organisms that cause more damage more quickly
Ex. S. Aureus, S. pneumoniae
What are considered Subacute infections in infective endocarditis
Presenting from 6 weeks to 3 months
Often caused by organisms of low virulence with gradual destruction of valves
Ex. Viridans (alpha haemolytic) Streptococci
What are considered chronic infections in infective endocarditis
Presenting after more then 3 months
Often caused by organisms of low virulence wirh gradual destruction of the valves
Ex. Viridans (alpha hemolytic) Streptococci
How do Viridans work in infective endocarditis
They are found in the mouth, they produce these sticky substances that enable them to stick onto the side of the teeth, they can also use this sticky substance to hang on in the heart valves
What is the epidemiology of endocarditis
Infective endocarditis is very rare; approximately 20 cases per year might be seen at the QEII
What type of hearts does endocarditis take place on
Normal and abnormal heart valves and on congenital abnormal hearts
What bacteria typically infects normal hearts with endocarditis
S. Aureus (a highly virulent bacterial)
What is most likely to cause endocarditis on abnormal valves and where are these organisms most common
Low virulence, oral and skin microorganisms are more likely to cause infection on abnormal valves (e.g. alpha hemolytic streptococci, enterococci, and coagulase negative staphylococci).
Most common in the oral and gastric flora and produce capsular materials to aid in sticking to teeth (and heart valves)
What is the most common organism to cause native valve IE
Alpha haemolytic (“Viridans”) Streptococci
What are the risks of infection in prosthetic valves
They are most susceptible and may be infected by all of the above in addition to bacteria contaminating the valve at the time of its insertion
Ex. Coagulate negative staphylococci are commonest in PV IE
What is bacteremia
Bacteria circulating in the blood
Describe the steps in the pathogenesis of Endocarditis
- Mucous membranes and skin are colonized
- Trauma results in bacteremia
- Organisms adhere to roughed endocardial surfaces
- Adherence is promoted by fibrin, platelet aggregation, and endothelial damage
- Further platelet fibrin depositions takes place
- Bacteria divided begins and vegetations (looks like warts) develop
- Vegetations develop with dormant organisms at the centre
- As vegetation fragment, parts break off into the blood stream and embolism other organs (ex., brain or kidney)
What are the consequences of infection of the heart valves
Cauliflower vegetations may develop on the valves, and impair normal valve function or mat break off into the systemic circulation
Ongoing inflammation may destroy the valve and produce valvular insufficiency
Small emboli may enter the coronary arteries and cause myocardial infarction
Abscesses may develop in the heart muscle which impair electrical conduction
What are the consequences in the brain of endocarditis
The cortex may be showered with multiple micro-emboli (block vessels in the brain from blood clots) regulating in the development of confusion or coma
Large emboli may produce a stroke
Large emboli may occasionally result in one or more brain abscesses
Meningitis may occur from ongoing bacteraemia or emboli
What are the consequences in the kidney of endocarditis
Large emboli may break off and obstruct renal arteries
Immune complexes (bacterial antigens, complement and immunoglobulin) may cause renal kidney inflammation and damage
Can endocarditis affect the spleen
yes, emboli from large vegetations may go to the spleen, extremities, eye, or other organs
In endocarditis occasionally involved blood vessels will ____ and result in ___
weaken
stretching and bursting
What are janeway lesions
They are peripheral emboli that look like black dots on the skin or under nails
What increases the risk of developing endocarditis
previously recognized valvular heart disease
Preceding dental or other surgical procedures
Intravenous drug use (Encouraging bacteria to get into the blood)
Recent heart surgery
Long standing indwelling lines
How is endocarditis diagnosed
Blood cultures: they are positive in approximately 90% of cases
Negative cultures may occur with prior treatment or with organisms that do not grow in blood cultures
Echocardiogrpahy (looking at the action of heart in real time) it recognizes vegetations, if valves are moving abnormally
What is the treatment for endocarditis
The treatment is customized for every patient and depends on;
- They type of organism and its susceptibility pattern
- The presence or absence of foreign material (harder to treat)
- The feasibility of surgery
- Allergies, toleration of the therapy and convince
How long are cases of endocarditis created for
almost all cases are treated for at least 4 weeks
What type of combination treatments are common for endocarditis
penicillin and aminoglycoside combinations which act more effectively when combined for some organisms
Who has published guidelines for prophylactic antibiotics for at risk dental and surgical procedures
The American Heart Association
What prevention is there for endocarditis
Prophylactic antibiotics are normally given immediately before and for several hours after the procedure when a bacteremia is considered likely
Antibiotics likely interfere to decrease bacterial adherence so infection does not become established
What is meningitis
Inflammation of the membranes covering the brain and spinal cord (meninges)
This inflammation of the brain tissue is encephalitis (usually viral)
What symptoms are associated with acute meningitis
sudden onset
headaches that can lead to comotose
neck stiffness
Confusion (as the infection progresses)
What are the causes of acute bacterial meningitis
Streptococcus pneumonia
Neisseria meningitides (cousin of Neisseria gonerria): common in young adults
Haemopilus influenzae: less common because of immunization
Listeria monocytogenes: common in babies, older, and immuno suppressed
What are causes of acute viral meningitis
Enteroviruses (esp late summer and fall)
Arboviurses (transmitted by vectors)
Herpesviruses
Is bacterial or viral causes of meningitis more severe
Bacterial is more severe
what are the causes of chronic meningitis
Other diseases may be complicated by meningitis such as;
syphilis and Lyme disease
Tuberculosis
Cryptococcus ( a fungus) infection
What is the epidemiology of Streptococcus pneumoniae
Streptococcus pneumoniae occurs in both young children and adults and does not cause outbreaks
What is the epidemiology of Neisseria meningitides
Neisseria meningitides occurs primarily in infants, younger children, and teenagers/young adults; both sporadic and outbreak cases occur. Immunization may reduce future rates
What is the epidemiology of Haemophilus influenza
Haemophilus influenza affects children between 3 months and 5 years. Now virtually eliminated where HI vaccine is used
What is the epidemiology of Listeria monocytogenes
May affect the very young and the older (<50); most cases are likely food related and outbreaks occur
What is the epidemiology of enteroviruses
Usually responsible for mild cases during summer may occur in clusters
What is the epidemiology of arboviruses
these are misquotes seen primarily in localized areas of the work where the virus, mosquitos and other hosts encounter optimal conditions
Describe the initial invasion of the pathogenesis of bacterial meningitis
- Nasopharyngeal colonization (common esp in young adults crowed together)
- Local invasion
- Bacteremia
- Meningeal invasion (headaches, bacteria is starting to multiply under the membranes causing inflammation and puss)
- Bacterial replication in the subarachnoid space
- Release of bacterial cell wall components, endotoxins are very toxic and cause inflammation
Describe the development of the disease in the pathogenesis of bacterial meningitis
- Release of bacterial cell components
- Activation of macrophages to release cytokines
- Subarachnoid space inflammation
- Increased CSF (very delicate and clear gets cloudy with this) outflow resistance
- Cerebral vasculitis (swelling of brain)
- Increased blood brain barrier permeability
- Increased brain edema
- Confusion and coma
How is meningitis diagnosed
clinical features: headaches, stiff neck, fever, confusion (can progress over hours)
CT scan showing no evidence of a mass in the brain
Cloudy cerebral spinal fluid with increased numbers of white cells, high protein and low glucose
Organisms seen on gram stain (not always seen though) may be negative when antibiotics have been administered, or in early infection
CSF culture for bacteria, culture of blood also useful, PCR for bacteria in CSF may be used if cultures are negative
How is viral meningitis diagnosed
viral meningitis may be diagnosed using PCR
How is chronic meningitis diagnosed
test for specific agents
What is the treatment for meningitis
usually given empirically (right away) before the organism has been identified
Cerftriazone/vancomycin + ampicillin for a risk groups
What treatment is given for S. pneumonia meningitis
third-generation cephalosporin (such as cerftriaxone), vancomycin if resistant
penicillin treated for a week
What is the treatment for neisseria meningitis
ceftriaxone: penicillin for a week
What treatment is used for haemophilia influenzae
cerftriaxone
What treatment is used for Listeria
ampicillin because its resistant to all cephalosporins
treated for 3 weeks or so, hard to get rid of
What is meant by definitive treatment
once the cause is known
