Is group B streptococcus (Streptococcus agalactiae) bacteremia an indication for a transesophageal echocardiogram (TEE)?

Streptococcus agalactiae Bacteremia and TEE Indication

Group B streptococcus (GBS) bacteremia alone is not a routine indication for TEE, but TEE should be strongly considered if specific high-risk features are present, including prosthetic valves, intracardiac devices, persistent fever >72 hours on appropriate antibiotics, new murmur, embolic phenomena, or no identifiable source of bacteremia. 1, 2

Risk Stratification Approach

The decision for TEE in GBS bacteremia depends on clinical risk factors rather than the organism alone. Unlike S. aureus bacteremia where guidelines explicitly mention routine echocardiography is justified 1, GBS does not carry the same automatic indication.

Start with TTE First

• TTE is the recommended first-line imaging modality in all suspected infective endocarditis (IE) cases, with sensitivity of 60-70% for native valve endocarditis 1, 2, 3
• TTE should be performed rapidly when IE is suspected based on clinical presentation 1

Proceed to TEE if High-Risk Features Present

TEE is indicated when any of the following are present: 1, 2

• Prosthetic heart valves (TEE sensitivity ~90% vs TTE ~50% for prosthetic valves) 1, 3
• Intracardiac devices (pacemakers, ICDs) where TEE sensitivity is ~90% compared to only 25-40% for TTE 1, 2, 3
• Persistent fever >72 hours despite appropriate antibiotic therapy 1, 2, 4
• New heart murmur or change in existing murmur 1, 2
• Embolic phenomena (stroke, splenic infarct, other systemic emboli) 1
• No identifiable source of bacteremia 2
• TTE is negative or nondiagnostic but clinical suspicion remains high 1
• New conduction abnormalities or atrioventricular block 1

TEE Performance Characteristics

• TEE has superior sensitivity (>90%) and specificity (91-100%) for detecting vegetations, abscesses, and perivalvular complications across all valve types 1, 3
• TEE has a negative predictive value up to 98.6%, though false negatives can still occur 5, 3
• If initial TEE is negative but clinical suspicion persists, repeat TEE in 3-5 days as early vegetations may be too small initially 2, 5

Important Clinical Caveats

The GBS-Specific Context

While one case report documents GBS causing both endocarditis and ventriculitis 6, this represents a rare presentation. GBS is not classified among the "typical IE causative organisms" that automatically trigger aggressive echocardiographic evaluation like S. aureus, viridans streptococci, Enterococcus, or HACEK organisms 1.

Common Pitfalls to Avoid

• Do not skip TTE and proceed directly to TEE unless prosthetic valves or intracardiac devices are present 1, 3
• Do not perform TEE in low-risk patients with good-quality negative TTE and identified source of bacteremia (e.g., skin/soft tissue infection) 1
• Do not assume TTE adequacy without assessing image quality - even "adequate" quality TTE has only 24% sensitivity compared to 94% for TEE in one study 7
• Acoustic shadowing from prosthetic materials can limit TEE visualization - consider cardiac CT if TEE is inconclusive for prosthetic valve complications 1, 5, 3

Mortality Implications

Detection of complications on echocardiography has direct prognostic significance: 2, 5

• Intracardiac abscess independently predicts both in-hospital and 1-year mortality
• Valve perforation independently predicts 1-year mortality
• Left ventricular ejection fraction <40% combined with abscess predicts in-hospital mortality

Practical Algorithm

1. All GBS bacteremia patients: Obtain TTE to evaluate for vegetations, valve function, and complications 1

2. If TTE positive for vegetation/abscess OR any high-risk feature present: Proceed to TEE for definitive evaluation 1

3. If TTE negative but persistent fever, no source identified, or clinical deterioration: Proceed to TEE 1, 2

4. If TTE negative, source identified, clinical improvement on antibiotics, no high-risk features: TEE not indicated 1