Should I order an echocardiogram (echo) for a patient with bacteremia due to Enterobacter (E) cloacae?

Echocardiography for Enterobacter cloacae Bacteremia

You should order an echocardiogram (TTE initially) for E. cloacae bacteremia if the patient has any high-risk features for infective endocarditis, including prosthetic valves, intracardiac devices, persistent fever despite appropriate antibiotics, new cardiac murmur, embolic events, heart failure signs, or immunocompromised status. 1

Risk Stratification Approach

Unlike S. aureus bacteremia where echocardiography has a Class IIa recommendation regardless of risk factors 1, E. cloacae bacteremia requires individualized assessment based on specific clinical features since it is not explicitly addressed in major endocarditis guidelines.

Mandatory Echocardiography (Start with TTE)

Order echocardiography immediately if ANY of the following are present:

• Prosthetic heart valve or intracardiac device (pacemaker, ICD, LVAD) - these patients require TEE regardless of TTE findings 1
• Previous history of infective endocarditis 2
• New or changing cardiac murmur 2
• Signs of heart failure (dyspnea, pulmonary edema, elevated JVP) 2
• Embolic events (stroke, splenic infarct, peripheral emboli) 2
• Persistent bacteremia (positive blood cultures >72 hours on appropriate antibiotics) 1, 2
• Persistent fever (>72 hours on appropriate antibiotics without alternative source) 1, 2
• New conduction abnormalities (new AV block suggesting perivalvular extension) 2

Consider Echocardiography

Order TTE if multiple moderate-risk features are present:

• Hospital-acquired infection - 86.5% of E. cloacae bacteremia is nosocomial 3
• Immunocompromised status (transplant recipients, chronic steroids, chemotherapy) 2, 3
• Prolonged hospitalization or ICU stay 3, 4
• Recent invasive procedures (urological procedures, central lines) 3
• Polymicrobial bacteremia - common with Enterobacter species 5, 4

Echocardiography Protocol

Initial Imaging

Start with transthoracic echocardiography (TTE) as first-line imaging 1. TTE has 70% sensitivity for native valve vegetations but only 50% for prosthetic valves 1, 2.

When to Proceed to TEE

Order transesophageal echocardiography (TEE) if:

• TTE is negative but clinical suspicion remains high (Class I recommendation) 1
• TTE is non-diagnostic or suboptimal quality 1
• Prosthetic valve or intracardiac device present (TEE mandatory regardless of TTE) 1, 2
• TTE is positive - to evaluate for complications like abscess, perforation, or fistula 1

TEE has 88-96% sensitivity for vegetations, substantially higher than TTE 2.

Timing Considerations

• Perform TTE as soon as infective endocarditis is suspected 1
• If initial TEE is negative but suspicion remains high, repeat within 5-7 days 1, 2
• Perform TEE within 24-48 hours when high clinical suspicion exists despite negative TTE 2

Clinical Context for E. cloacae

Key Epidemiological Features

E. cloacae accounts for 65-75% of Enterobacter infections, with bacteremia being the most common syndrome 5. The attributable mortality rate is 13.5% 3, and most cases (86.5%) are hospital-acquired 3.

Common Sources and Risk Factors

• Urological source - 48.1% of cases originate from urological surgery or obstruction 3
• Polymicrobial bacteremia - frequently occurs with other organisms 5, 4
• Immunocompromised hosts - transplant recipients, malignancy patients 6, 3
• Prior antibiotic exposure - 55% received antibiotics in preceding 10 days 6

Important Caveats

Do not assume low virulence - while E. cloacae is generally considered less virulent than S. aureus for endocarditis, it can cause community-acquired bacteremia with clear infectious foci even in patients without severe underlying diseases 7. The presence of shock (24% of cases) or pulmonary infection significantly worsens prognosis 6.

Elderly and immunocompromised patients may have atypical presentations with less prominent fever, requiring a lower threshold for echocardiography 2.