Bacteremia Flashcards
Staphylococcus Aureus Bacteremia (SAB)
Leading cause of community-acquired & hospital-acquired bacteremia
Higher mortality & treatment failure with MRSA
SAB Diagnosis
Blood cultures–>gold standard
Clinically significant regardless of the number of positive bottles
Repeat (2 sets) every 48-72 hours until negative
- Establishes day 0 of antibiotics–> 1st negative test
Echocardiography
All patients
1st: Transthoracic echocardiography (TEE)
2nd: Transesophageal echocardiography (TEE)–>preferred for MRSA
- More sensitive than TTE for vegetation size/location
- Most sensitive within 5-7 days onset of bacteremia
- Better for identifying intracardiac abscesses & valve perforation
- Only repeat if highly suspicious of IE
Urine Culture
S. aureus is NOT a common organism in UTI
- Translocation of S. aureus from blood to urine is due to hematogenous seeding and development of microabscesses
If present, high likelihood of SAB
Catheter/Prosthetic Device Management
All IV catheter and prosthetic devices must be considered infected by SAB until infection ruled out
Prosthetic devices:
- 1st remove prosthetic device
- 2nd if cannot, add rifampin + long term suppressive therapy
Catheters:
- Short-term catheter: remove ASAP
- Long-term catheter: remove unless major contraindication: replace when blood cultures are negative for 48-72 hours
Empiric therapy
Cover MSSA and MRSA–>gram stain showing clusters
- IV vancomycin, IV daptomycin
High risk (severe sepsis, endocarditis, prosthetic device, hemodynamically unstable, hx of MSSA bacteremia)
- Vancomycin + Nafcillin/oxacillin/cefazolin
Targeted
MRSA:
- Vancomycin IV–>target AUC/MIC 400-600
- Daptomycin IV–>recommended for right-sided endocarditis (septic pulmonary emboli)
Refractory, persistent MRSA:
- Vancomycin/Daptomycin + Ceftaroline
MSSA:
IV Nafcillin/Oxacillin/Cefazolin
What not to do in MSSA?
- Vancomycin–>less effect vs MSSA and increased mortality
- Combination with rifampin–>drug interactions
- Combination with AGS–>toxicity
Duration
Uncomplicated SAB–> 14 days
Must meet all criteria:
- Exclusion of endocarditis (negative TTE, TEE)
- No indwelling or implantable devices/prostheses
- Follow-up blood cultures at 2-4 days were negative
- Clinically improvement in 48-72 hours
- No evidence of metastatic infection
Complicated SAB–> 4 weeks
Complicated SAB + metastatic infection–> 6-8 weeks
Prognosis
Presence of prosthetic material or devices increase risk of relapse
Mortality higher in:
Increased age
Female
Immunosuppression
Comorbidities
Type of infection
Persistent bacteremia
MRSA
Bacteriuria
Sepsis/shock
Time to positivity of blood cultures < 12 hours
Streptococci bacteremia risk of endocarditis
High risk: viridians strep, strep gallolyticus
Low risk: S. agalactiae, S, pyogenes, S. pneumoniae
Streptococci bacteremia HANDOC Score
Determines need for TEE
Heart murmur
Aetiology
Number of positive blood cultures ≥ 2
Duration of symptoms ≥ 7 days
Only 1 species in blood culture
Community-acquire infection
Streptococci bacteremia treatment
Group A and B strep–> IV penicicllin–> amoxicillin PO
S. pneumoniae–> ceftriaxone or penicillin
Streptococci bacteremia duration
14 days
Can transition from IV to PO
Enterococci bacteremia
E. faecalis, E, faecium
DENOVA Score for E. faecalis
Duration ≥ 7 days
Embolization
Number of positive cultures
Origin of infection unknown
Valve disease
Auscultation of murmur
Enterococci bacteremia treatment
E. faecalis: Ampicillin
- if resistant or allergy–>vancomycin/daptomycin
E. faecium: VanA or VanB negative–>vancomycin
VanA or VanB positive–>daptomycin or linezolid
Duration: 7 days
Uncomplicated gram negative
Treatment:
Pseudomonas–>Zosyn, Cefepime, Levofloxacin, Meropenem, Bactrim
Duration: 7 days
Total days, not from Day 0
Do not always have to repeat blood cultures
May switch from IV to PO when clinically stable
Longer duration is not always better
Can show a 4% risk of infection per day longer on therapy
