Nguyen (2026); Blood Stream Infections and Infective Endocarditis (Therapeutic Concepts)

What are (2) IV empiric / definitive options for MSSA associated bloodstream infections?(

Adult dosing, NO renal dysfunction)

(Drug, Dose, Route, Frequency

Cefazolin 2g IV Q8h

OR

Nafcillin 2g IV Q4h

What are (2) IV empiric / definitive options for MRSA associated bloodstream infections?

(Adult dosing, NO renal dysfunction)

(Drug, Dosing target / Dose, Frequency)

Vancomycin IV (trough 15-20 or AUC/MIC 400-600)

OR

Daptomycin 6mg/kg IV Q24h (some may use 8-10mg/kg per dose)

What are (2) empiric / definitive options for Staph. epidermidis associated bloodstream infections?

(Adult dosing, NO renal dysfunction)

(Drug, Dosing target / Dose, Frequency)

Same as MRSA:

Vancomycin IV (trough 15-20 or AUC/MIC 400-600)

OR

Daptomycin 6mg/kg IV Q24h (some may use 8-10mg/kg per dose)

What are the empiric / definitive treatment options (2) for Enterococcus faecalis associated bloodstream infections?

(Adult dosing, NO renal dysfunction)

(Drug, Dosing target / Dose, Frequency)

Ampicillin 2g IV Q4h

OR

Vancomycin IV (target trough 15-20 mg/L)

What are (3) empiric / definitive treatment options for (NON ESBL) E.coli associated bloodstream infections?

(Adult dosing, NO renal dysfunction)

(Drug, Dosing target / Dose, Frequency)

Same as Klebsiella spp. associated bacteremia:

• Ceftriaxone 2g IV Q24h

• Ciprofloxacin 400 mg IV Q12h OR 500 mg PO Q12h

• Levofloxacin 500 mg IV/PO Q24h

Definitive only & clinically stable: TMP/SMX PO 5mg/kg/dose Q8h-Q12h

What are (3) empiric / definitive treatment options for (NON ESBL) Klebsiella spp. associated bloodstream infections? Definitive & clinically stable patients?

(Adult dosing, NO renal dysfunction)

(Drug, Dose, Route, Frequency)

Same as E.Coli associated bacteremia:

• Ceftriaxone 2g IV Q24h

• Ciprofloxacin 400 mg IV Q12h OR 500 mg PO Q12h

• Levofloxacin 500 mg IV/PO Q24h

Definitive only & clinically stable: TMP/SMX PO 5mg/kg/dose Q8h-Q12h

What is the empiric treatment for ESBL-producing enterobacterales (E.Coli, Klebsiella spp.) associated bloodstream infections?

(Drug, Route, Dose, Frequency)

Ertapenem 1g IV Q24h

Critically ill: Meropenem 1g IV Q8h

What are (5) treatment options for Pseudomonas associated bloodstream infections?

(Drug, Route, Dose, Frequency)

•Cefepime 2g IV Q8h

•Ceftazidime 2g IV Q8h

•Ciprofloxacin 400mg IV Q8h OR 750mg PO Q12h

•Piperacillin/tazobactam:

—Intermittent infusion (30 min): 4.5g IV q6h

—Extended infusion (4 hrs): 3.375-4.5g IV Q8h

•Meropenem 1g IV Q8h

When using Piperacillin/tazobactam for the treatment of Pseudomonas associated bloodstream infections, what are the two infusion rates you can use?

(Duration, Dose, Route, Frequency)

Piperacillin/tazobactam:

• Intermittent infusion (30 min): 4.5g IV q6h

• Extended infusion (4 hrs): 3.375-4.5g IV Q8h

Typical final treatment duration for gram negative bloodstream infections?

7 days for gram negative

Typical final treatment duration for gram positive bloodstream infections?

14 days for gram positive

Exception: Complicated staph aureus

What are the (5) features of uncomplicated bacteremia?

NO endocarditis

NO implanted prostheses

NO evidence of metastatic sites of infection

Follow-up blood cultures 2-4 days after initial positive cultures are negative

Afebrile within 72 hours of starting effective treatment

What are the (2) recommended treatment durations for Staphylococcus aureus associated bacteremia?

Uncomplicated and Complication: (Duration)

Uncomplicated: 14 days

Complicated: 4-6 weeks

Repeat blood cultures: Staph aureus & Candida BSI, (Repeat, Stop, when is Day 1 of tx?)

Repeat Q48h (surveillance) until negative

Day 1 of tx = 1st day of negative cultures

Repeat blood cultures: Gram-negatives BSI

Generally no added value to recheck

Day 1 of tx = 1st day of effective antibiotic

BSI treatment principles (4) (preferred: route, type, dosing, formulation)

• IV route preferred

• Bactericidal drugs preferred

• Dose at higher end of range (if dosing range available)

• Once stable, can consider PO switch w/ high bioavailability (e.g., IV ceftriaxone -> PO cipro for GNR)

*GNR, gram negative rods

What are the (3) potential complications of infective endocarditis?

• Valvular abscess

• Valve prolapse, aortic insufficiency -> heart failure (HF)

• Septic emboli -> (e.g. stroke, pulmonary embolism (PE))

What are the treatment options for MSSA associated Native Valve Infective Endocarditis?

(Drug, Dose, Route, Frequency, Duration)

Nafcillin 2g IV Q4h

OR

Cefazolin 2g IV Q8h

Duration: 6 weeks

What are (2) treatment options for MRSA associated Native Valve Infective Endocarditis?

(Drug, Route, Dose, Frequency, Duration)

Vancomycin IV (trough 15-20 or AUC/MIC 400-600)

OR

Daptomycin 8-10 mg/kg IV Q24h (total BW)

Duration: 6 weeks

What are the treatment options for MSSA associated Prosthetic Valve Infective Endocarditis?

(Drug, Dose, Route, Frequency)

Nafcillin 2g IV Q4h (or Cefazolin 2g IV Q8h) x ≥6 weeks

PLUS

Rifampin 300 mg PO Q8h x ≥6 weeks

PLUS

Gentamicin (1 mg/kg Q8h, IBW) (target peak 3-5 mg/L, target trough <1 mg/L) × 2 weeks

What are the treatment options for MRSA associated Prosthetic Valve Infective Endocarditis?

(Drug, Dose, Route, Frequency)

Vancomycin IV (trough 15-20 or AUC/MIC 400-600) × ≥6 weeks

PLUS

Rifampin 300 mg PO Q8h × ≥6 weeks

PLUS

Gentamicin (1 mg/kg Q8h, IBW) (target peak 3-5 mg/L, target trough <1 mg/L) × 2 weeks

What are the primary treatment regimens for Native Valve Streptococcal associated Infective endocarditis IF PCN MIC ≤0.12 µg/mL?

(Drug, Dose, Route, Frequency, DURATION)

Penicillin G 2-3 million units IV Q4h

OR

Ceftriaxone 2g IV Q24h

Duration: 4 weeks

Note, Beta-lactam allergy: Vancomycin IV (trough 15-20 or AUC/MIC 400-600)

What are the primary treatment regimens in Native Valve Streptococcal associated infective endocarditis IF you want to do a short course duration IF PCN MIC ≤0.12 µg/mL?

(Drug, Dose, Route, Frequency, Duration)

Short-course Duration: 2 weeks

Either, Penicillin G 2-3 million units IV Q4h IV

OR

Ceftriaxone 2g/ IV or IM Q24h

PLUS

Gentamicin 3 mg/kg once daily (Only target trough <1 µg/mL)

What are (2) treatment options for Native Valve, Streptococcal associated infective endocarditis IF PCN MIC >0.12 µg/mL to <0.5 µg/mL?

Penicillin G 4 MU IV Q4h × 4 week

OR

Ceftriaxone 2g/ IV or IM Q24h × 4 weeks

PLUS

Gentamicin 3 mg/kg once daily (target trough <1) × 2 weeks

Note, Beta-lactam allergy: Vancomycin IV (trough 15-20 or AUC/MIC 400-600) × 4 weeks

W hat are (2) treatment options for Streptococcal associated Prosthetic Valve Infective Endocarditis IF PCN MIC ≤0.12 µg/mL?

(Drug, Dose, Route, Frequency, Duration)

Penicillin G 4 million U IV Q4h × 6 week

OR

Ceftriaxone 2g IV Q24h × 6 week

+/-

Gentamicin 3 mg/kg once daily (target trough <1) × 2 week

Note, Beta-lactam allergy: Vancomycin IV (trough 15-20 or AUC/MIC 400-600) × 6 weeks

What are (2) treatment options for Streptococcal associated Prosthetic Valve Infective Endocarditis? (PCN-Resistant strain)

(Drug, Dose, Route, Frequency, Duration)

Penicillin G 4 million U IV Q4h

OR

Ceftriaxone 2g IV Q24h

PLUS

Gentamicin synergy (3mg/kg/24hr, one dose, target trough: <1)

Duration: 6 weeks

Note, Beta-lactam allergy: Vancomycin IV (trough 15-20 or AUC/MIC 400-600) × 6 weeks

What is the primary treatment option for Enterococcal Native or Prosthetic Valve associated Infective Endocarditis? (Susceptible to PCN/Amp + Gent)

(Drug, Dose, Route, Frequency, Duration)

Ampicillin 2g IV Q4h

PLUS

Gentamicin IV (1 mg/kg Q8h, IBW) (target peak 3-5 mg/L, target trough <1 mg/L)

Duration: 4-6 weeks

* 4 weeks: NVE, symptoms <3 months

* 6 weeks: NVE, symptoms >3 months, or any prosthetic valve/material

What is the primary treatment option for Enterococcal Native or Prosthetic Valve associated Infective Endocarditis? (Susceptible to PCN/Amp, RESISTANT to Gent)

(Drug, Dose, Route, Frequency, Duration)

(Dual beta-lactam synergy)

Double B-lactam Ampicillin 2g IV Q4h

PLUS

Ceftriaxone 2g IV Q12h (Note: different from typical Q24h)

Duration: 6 weeks

What are (2) treatment options for Native or Prosthetic Valve Vancomycin Resistant Enterococcal (VRE) associated Infective Endocarditis?

(Drug, Dose, Route, Frequency, Duration)

Daptomycin 10-12 mg/kg IV Q24h (total BW)

OR

Linezolid 600mg IV/PO Q12h

Duration: At least 6 weeks

What is the mechanism of gentamicin synergy with beta-lactams, and what are the two dosing strategies with their respective pharmacokinetic targets?

Beta-lactam disrupts cell wall -> aminoglycoside penetrates to 30S ribosome

1. IF dose: 1 mg/kg, target peak 3-5 mg/L, 2. IF dose: 3mg/kg, target trough <1 mg/L

What are (4) treatment options for Infective Endocarditis Prophylaxis (dental procedures) in patients WITH a penicillin allergy?

Cephalexin 2g PO

OR

Azithromycin 500mg PO

OR

Clarithromycin 500mg PO

OR

Doxycycline 100mg PO (Note: Added in 2021 AHA Guideline Update)

Regimen: Single Dose 30 to 60 min before procedure

What is the preferred PO treatment option for Infective Endocarditis Prophylaxis (dental procedures)?

Amoxicillin 2g PO

Regimen: Single Dose 30 to 60 min before procedure

What is a "TTE"?

TransThoracic Echocardiogram (TTE), used for diagnosis of infective endocarditis

What is "TEE"

TransEsophageal Echocardiogram (TEE), used for diagnosis of infective endocarditis