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Case 3: Medical Microbiology Infect. Endocarditis - Coggle Diagram
Case 3: Medical Microbiology Infect. Endocarditis
Infective Endocarditis (IE)
Define Infective Endocarditis
Infective endocarditis is the infection of the endocardial surface of the heart.
Endocardium is the innermost lining of the chambers of the heart.
Endocarditis usually involves the cardiac valves, which are continuous with the endocardial layer of the heart.
Infective endocarditis can occur both in Valvular endocarditis and Congenital Heart Defects
Pathogenesis and Pathology of Infective Endocarditis
Describe the Pathogenesis and Pathology of Infective Endocarditis
The Pathogenesis of IE is multifactorial
The different processes occur in Tandem (conjunction with each other)
The Valve has to undergo Surface Damage. eg: Recurrent attacks of Acute Rheumatic Fever
Damage allows deposition of Platelets, Fibrin and other proteins to attach to the Surface of the Valve
Turbulent flow around the valve encourages this process
Eventually, Bacteria that transiently enter the Bloodstream, for example after a dental procedure, attach to the Valve and Colonize it resulting in the formation of a Vegetation.
What is a vegetation made up of ?
Vegetation is a mass of Platelets, Fibrin, Colonies of bacteria and Inflammatory Cells.
Aetiology and microbiology of Infective Endocarditis
Describe the Aetiology of Infective Endocarditis
Infective Endocarditis is caused by the following organisms:
Streptococci
Streptococci can be further classified into the:
Viridans Streptococci also known as the Alpha Haemolytic Group Streptococci
Enterococci
Staphylococci
Staphylococci can be further divided into:
Staphylococcus aureus, one of the most Virulent and Destructive organisms
Coagulase-Negative Staphylococci, which are less Virulent and usually require damaged valves to gain a foothold of Infection
HACEK organisms
Haemophilus species
Aggregatibacter
Cardiobacterium
Eikenella
Kingella
Bartonella, Brucella and Coxiella (BBC)
This organisms are Difficult-to-Grow or Fastidious
Describe the Microbiology of Streptococci and Staphylococci when viewed under the microscope
Streptococci
When Gram Stained and viewed under the microscope:
Streptococci are Gram Positive Cocci which form Chains
Staphylococci
When Gram Stained and viewed under the microscope:
Staphylococci are Gram Positive cocci which from Clusters
There is NO WAY to differentiate Staphylococcus aureus from Coagulase-Negative Staphylococci on microscopy
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REVIEW CASE 1 MICROBIO
Classification of Streptococci
Outline the Classification of Streptococci
Streptococci are further divided into
Viridans Streptococci also known as Alpha-Haemolytic Streptococci
This is because Alpha-Haemolysis causes a green discolouration of the Blood Agar Plates
This is because these organism cause Horse/Sheep blood in agar plates to turn green
"Viridis" in Latin means green
Hence, Viridans Streptococcus
Beta-Haemolytic Streptococci include Streptococcus pyogenes which cause Rheumatic Fever
Describe the purpose of classifying Streptococci as Alpha and Beta Haemolytic groups
Classifying Streptococci into Alpha and Beta Haemolytic groups is useful for procedures in the Laboratory
As well as for predicting the final identity of the causative organism and possible treatment option
Epidemiology and Risk factors of Infective Endocarditis
IE requires some abnormality of the Valve
Most commonly, valve damage is due to Rheumatic Fever or Congenital Heart defects
Outline the Risk Factors of Infective Endocarditis
Abnormal Heart Valves
Rheumatic Heart Disease
Congenital Heart Disease
Artificial/Prosthetic Heart Valves
Introduction of bacteria into the bloodstream
Intravenous drug users
Poor Dentition/Oral Health
Some patients have NO risk factors of Endocarditis BUT still develop Infective endocarditis
Epidemiology and Classification of Infective Endocarditis
Differentiate between the types of Infective Endocarditis
Endocarditis can be Right-Sided or Left-Sided Endocarditis
Right-Side Infective Endocarditis usually involves the Tricuspid Valve and Pulmonary Valve
Right-sided Infective Endocarditis is usually caused by Intravenous drug use.
How ?
IV Drug use allows bacteria to enter into the Venous system and for the bacteria to be carried away to the Right-side of the Heart
Left-Sided Infective Endocarditis is usually involves the Aortic Valve and mitral valve
Endocarditis can be Native Valve or Prosthetic Valve endocarditis
Native Valve Infective Endocarditis occurs in patients who have NEVER had a Valvular Surgery
Native valve endocarditis is caused by virulent organisms such as Staphylococcus aureus
Prosthetic Valve Infective Endocarditis occurs in patients with Artificial Cardiac valves
Prosthetic valve endocarditis is caused by less virulent organisms such as Coagulase-negative Staphylococci
The treatment for both entities differs
Endocarditis can be Acute or Subacute Endocarditis
Acute Infective Endocarditis has an Acute Onset
Acute Infective Endocarditis is caused by Staphylococcus aureus
Therefore, it is critical to commence antibiotics that will cover this organism
Subacute Infective Endocarditis has a Subacute Onset
It is caused by a vast array of organisms
Is Rheumatic Fever the same as Infective Endocarditis ?
NO, Rheumatic Fever and Infective Endocarditis are separate Clinical Syndromes.
However, Rheumatic Heart disease is a risk factor of Infective Endocarditis
Clinical Findings (Signs and Symptoms) of Infective Endocarditis
Patients with Infective Endocarditis may present with:
Non-Specific Symptoms such:
Fever, night sweats
Fatigue, Loss of appetite and Weight Loss
Cardiac Murmurs such as:
Regurgitation murmur localized to affected valve
"Classic" Features
Clubbing
Splinter Haemorrhages
Osler Nodes
Roth Spots
Janeway Lesions
Cardiac Murmurs
Auscultate all valves at their respective locations with both the Diaphragm and Bell of the Stethoscope whilst palpating the Carotid Pulse
Auscultate the Carotid pulse with the Bell of the Stethoscope
Perform Accentuation Maneuvers
Aortic Murmurs: Ask patient to sit forward and breathe Deeply in and out and hold it
Aortic Murmurs will get louder with expiration
Mitral murmurs: Ask patient to sit back in 45 degree angle and breathe Deeply in and out and Hold it.
and then Roll onto Left lateral position and Hold it.
Mitral Murmurs will get louder Expiration
Auscultate the Axilla to listen for radiation from the Mitral Murmur
"Classic" Features
Clubbing
Clubbing of the fingers is also a feature of Chronic Inflammatory conditions such as Bronchiectasis
Splinter Haemorrhages
Splinter Haemorrhages are brown, linear streaks on the fingernails
Roth Spot
Roth spot is visualized on the Fundoscopy
ALWAYS remember to examine patient's Fundi
Osler Nodes
Osler nodes are painful nodes found on the pads of the fingers or toes
Janeway Lesions
Janeway lesions are painless nodules on the palms or soles
Embolic Phenomena of Infective Endocarditis
Explain the Embolic Phenomena of the Infective Endocarditis
Sometimes, vegetations may break off and embolise to distant organs.
This frequently occurs as a Stroke in left-Sided Infective Endocarditis
MRI (Magnetic Resonance Imaging) shows Ischaemia in the brain parenchyma in a patient with Infective Endocarditis
Special Investigations: Echocardiogram "Echo"
Define the Echocardiogram
Echocardiograms also known as an "Echo" is the most useful radiological investigation in Infective Endocarditis.
How does the Echocardiogram work ?
It visualizes the heart using Ultrasound
It may show a vegetation directly, or the abnormal flow of blood around the valves
Determines blood flow and cardiac function
Special investigations: Microbiological (Blood Culture)
Outline the process of Blood Culture
Blood culture is one of the most critical investigations to perform in the work-up of Infective endocarditis
The Blood Culture test is as follows:
Venous blood is drawn into a specially designed Blood Culture Bottle.
It is important for this procedure to be STERILE in order to avoid any contamination with skin or environmental bacteria
Two separate Blood Cultures should be drawn, before antibiotic are administered.
Blood culture bottle has a special indicator on the underside of the bottle
Indicator changes with Bacterial Growth and the colour is continuously monitored by an automated instrument
Bacteria in the patient's blood continue to multiply in the bottle, producing Carbon Dioxide, which changes the colour of the indicator on the bottom of the bottle
Once the Blood Culture bottle flags Positive, culture material is aspirated from the Blood culture bottle using a Needle and Syringe
Gram Stain test is then perfumed
The culture material is then placed into Agar Plates and identified to the species level
The organisms is also tested for Susceptibility to antibiotics
Susceptibility testing is performed differently for different organisms
For Streptococci, we usually test with Penicillin.
If we determine the organism is sensitive to a particular antibiotic, and if it is appropriate for the type of infection.
Antibiotic can be used to treat the patient.
Special Investigations: Microbiological
Warning !
For future reference:
To prevent bacterial contamination
To prevent wastage of resources
To prevent usage of inappropriate and dangerous antibiotics
AND TO PASS MEDICAL SCHOOL
Perform the blood culture procedure EXACTLY as stipulated
Failure to do so could result in the patient being administered incorrect and toxic antibiotics for no reason
Diagnostic Criteria
Together, the Clinical, Radiological and Microbiological Findings are taken and applied to the Diagnostic Criteria which can help make the diagnosis.
This is known as the Modified Duke Criteria
Outline the Modified Duke Criteria
The Modified Duke Criteria is made up of the:
Major Criteria
Minor Criteria
The Major and Minor Criteria are then used to define the disease as:
Definitive Infective Endocarditis
Possible Infective Endocarditis
Diagnosis rejected/ No Infective Endocarditis
Outline the Clinical Criteria
For Definitive Infective Endocarditis there must be:
2 Major Criteria OR
1 Major Criteria and 3 Minor Criteria OR
5 Minor Criteria
For Possible Infective Endocarditis there must be:
1 Major Criteria and 1 Minor Criteria OR
3 Minor Criteria
List the findings of the Major Criteria and the Minor Criteria of Infective Endocarditis
Major Criteria
Blood culture is positive for IE
Typical microorganisms consistent with IE from 2 separate blood cultures (Staphylococcus aureus or Viridans Streptococci)
Evidence of Endocardial Involvement
Echocardiogram is positive for IE
Minor Criteria
Predisposing Heart Condition or Intravenous Drug Use
Increased Temperature (> 38 degrees Celsius), Fever
Vascular Phenomena: Emboli, Sceptic Pulmonary Infarcts, Conjunctival Haemorrhages, Mycotic aneurysm, Janeway Lesions
Immunological Phenomena: Glomerulonephritis, Osler nodes, Roth spots
Microbiological finding
Positive Blood Culture BUT does NOT meet a major criteria
Example 1
A patient has two positive blood cultures with viridans streptococci and an echo
shows a large vegetation.
Answer: Definitive Infective Endocarditis
Example 2
A patient with rheumatic heart disease presents who presents with fever
and neurological signs suggestive of a stroke. The echo is normal and blood cultures are negative.
Answer: The patient has no major criteria, but has 3 minor criteria. Therefore, Possible Infective Endocarditis
Treatment for Infective Endocarditis
List the treatment options for Infective Endocarditis
Treatment for Infective endocarditis:
Antibiotics given Intravenously
Surgical Removal and replacement of Infected Valve
Treatment for Infective Endocarditis: Antibiotics
Outline the treatment procedure of Antibiotics for Infective Endocarditis
While waiting for the Blood culture results:
Start Empirical Antibiotics to cover the most likely Aetiology.
For example: In Acute Endocarditis, make sure antibiotics cover Staphylococcus aureus
Once organism is identified, the antibiotic can be changed to target the organism
NOTE: Antibiotics are given Intravenously until we have local data about oral therapy
Treatment is prolonged (6 weeks)
Mechanisms of action of Antibiotics in LOM
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Treatment for Infective Endocarditis: Surgical
Outline the Surgical Treatment procedure for Infective Endocarditis
In severe cases of Infective Endocarditis which result in Valve Destruction and Cardiac failure, Infected valves must be removed by Open Heart Surgery and replaced.
Severe cases of Infective Endocarditis result in Valve Destruction and Cardiac Failure
Histology, Microbiology and PCR of the Infected Valve can help make the diagnosis.
Prevention of Infective Endocarditis
Outline the Prevention of infective Endocarditis
Antibiotic Prophylaxis is given to:
Patients with Rheumatic Heart Disease before a dental procedure
Patient's before a Dental procedure
STILL recommended in SA
Prevention of Infective Endocarditis at a Public Health Level includes:
Improving the socio-economic situation
Improving general Oral health
Special case: Culture Negative Endocarditis
What happens when the Blood cultures are negative and No organism is grown ?
Reasons
Firstly, Why would this happen ?
Usually it is a result of antibiotics being given before Blood Culture is drawn.
The Infection is caused by a Difficult-to-grow organism/ Fastidious organisms that do not grow well in blood culture bottles such as (Brucella, Bartonella and Coxiella) "BBC"
Diagnosis
To differentiate between the 2 causes, draw Serum for antibody testing for Bartonella and Coxiella
Treatment
How do we treat Culture Negative Endocarditis ?
Culture negative endocarditis can be treated for the most COMMON Aetiologies
PLUS treatment can be given for Fastidious organisms
