The infective process of endocardial layer of the heart can involve native or prosthetic valve and congenital defects/shunts. Alpha–haemolytic streptococci are the most common causes of native valve endocarditis but Staphylococcus aureus is more likely if the disease is rapidly progressive with high fever, or is related to a prosthetic valve (Staphylococcus epidermidis)

Diagnostic criteria

Modified Dukes Criteria is used. Consult microbiologist where possible. Three sets of blood cultures should be taken before starting treatment.

Modified Dukes Criteria

Major Criteria

• Positive blood cultures of typical organism for IE from at least two separate blood cultures

• Evidence of endocardial involvement by echocardiogram (Trans–thoracic Echo/Trans– oesophageal Echo)

  
  

Minor Criteria

• Fever > 38ºC

• Presence of Rheumatic heart disease, congenital heart disease

• Vascular phenomena; Major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhage, conjunctival hemorrhage, Janeway lesions

• Immunological phenomena; glomerulonephritis, Osler`s nodes, Roth`s spots,

• Rheumatoid factor.

• Serologic evidence of active infective endocarditis or blood culture not meeting major criterion.

Definitive diagnosis of IE

• Two major criteria or

• One major and three minor criteria or

• Five minor criteria

Possible Diagnosis of IE

One major and one minor or three minor criteria

Key Note: Positive blood cultures remain the cornerstone of diagnosis and provide live bacteria for both identification and susceptibility testing.

To improve yield of culturing bacteria at least three blood sample sets are taken at 30 minutes apart each containing 10 mL of blood and should be incubated in both aerobic and anaerobic atmospheres.

Sampling should be obtained from a peripheral vein using a meticulous sterile technique.

Pharmacological

Empirical Treatment: Consider when blood cultures are negative, or when the risk of delaying treatment to obtain blood cultures outweighs the benefit of waiting for culture results.

Native valve – empirical treatment

• A: Benzylpenicillin IV 18–24 million units per 24 hours, in equal doses every 4 hours, for 4–6 weeks,

• OR B: ceftriaxone IV 2 g every 24 hours for 4–6 weeks,

• AND B: cloxacillin IV 2 g every 6 hours for 4–6 weeks,

• AND A: gentamicin IV 1–1.5 mg/kg every 8 hours for at least 2 weeks.

• Methicillin-resistant staphylococci (MRSA): S: vancomycin IV 30 mg/kg per 24 hours in two equal doses (not above 2 g/24 hours unless serum levels are monitored) for 4–6 weeks.

Prosthetic valve – empirical treatment

• A: Benzylpenicillin IV 18–24 million units per 24 hours, in equal doses every 4 hours, for 6–8 weeks,

• OR B: ceftriaxone IV 2 g every 24 hours for more than 6 weeks,

• AND B: cloxacillin IV 2 g every 6 hours for more than 6 weeks,

• AND A: rifampicin 300–600 mg IV every 8 hours for more than 6 weeks,

• AND A: gentamicin IV 1 mg/kg every 8 hours for 2 weeks.

⚠ Dose check note: STG 2026 prints rifampicin "300–600 mg (IV) 8hourly" for prosthetic valve endocarditis. At the top of this range (600 mg every 8 hours = 1,800 mg/day) the risk of liver toxicity is high; WHO-aligned and international endocarditis guidance gives rifampicin 900–1,200 mg/day IV or PO in 2–3 divided doses (for example 300–400 mg every 8 hours). Cross-check this dose against the WHO recommendation before prescribing.

Gentamicin monitoring: check serum levels every 3–4 days; the 1-hour peak should not exceed 10 mg/L and the trough (pre-dose) should be below 2 mg/L. Adjust the gentamicin dose to creatinine clearance in renal failure.

At any stage, treatment may have to be modified according to:

• Detailed antibiotic sensitivity tests

• Adverse reactions or allergy

• Failure of response

Endocarditis leading to significant cardiac failure or failure to respond to antibiotics may well require early cardiac surgery within few days

Referral

Patients with complicated IE should be evaluated and managed in high level of care or centre, with immediate surgical facilities and the presence of a multidisciplinary including an Infectious Disease specialist, a microbiologist, cardiologist, imaging specialists, and cardiac surgeons

Infective Endocarditis Prophylaxis

Antibiotic prophylaxis should be considered for patients at highest risk for IE: Patients with any prosthetic valve, including a trans catheter valve, or those in whom any prosthetic material was used for cardiac valve repair.

Patients with a previous episode of IE.

Patients with Congenital Heart Disease (CHD):

(a) Any type of cyanotic CHD.

(b) Any type of CHD repaired with a prosthetic material, whether placed surgically or by percutaneous techniques, up to 6 months after the procedure or lifelong if residual shunt or valvular regurgitation remains.

Antibiotic prophylaxis is not recommended in other forms of valvular or CHD.

Prophylaxis of Endocarditis Infective

To reduce the risk of bacterial endocarditis, antibiotic prophylaxis should be given to patients undergoing dental procedures requiring manipulation of the gingival or periapical region of the teeth or perforation of the oral mucosa.

Antibiotic prophylaxis is not recommended for,

• Respiratory tract procedures including bronchoscopy or laryngoscopy, or trans nasal or endotracheal intubation

• Gastrointestinal or urogenital procedures or Trans–oesophageal Echocardiogram, gastroscopy, colonoscopy, cystoscopy, vaginal or caesarean delivery.

• Skin and soft tissue procedures

Antibiotic prophylaxis (single dose 30–60 minutes before the procedure)

Do not use cephalosporins after anaphylaxis, angio-oedema or urticaria with penicillin or ampicillin (cross-sensitivity).