Bacteremia Flashcards
What pathogen is the leading cause of community-acquired and hospital-acquired bacteremia?
staphylococcus aureus
(also streptococcus spp or enterococcus spp)
Patients with SAB can develop numerous potential complications
Mortality rates ∼20-40% (higher with MRSA compared to MSSA)
Treatment failure in staphylococcus aureus
Treatment failure is relatively common in SAB, especially if due to MRSA
* Death within 30 days following treatment
* Persistent bacteremia > 10 days after initiation of appropriate therapy (some recommend shorter duration of persistence)
* Recurrence of bacteremia within 60 days of discontinuing treatment
What is the clinical approach to SAB? - history and physical exam
What is the source of the bacteremia?
Question patients carefully regarding potential entry sites
* Skin/skin structure infection, any breaks in the skin
* Presence of indwelling IV catheters; orthopedic hardware; cardiac devices (remove if medically possible)
Question patients regarding symptoms that may reflect metastatic infection (occurs in up to 30% of cases)
* Bone or joint pain; back pain may suggest vertebral osteomyelitis, discitis, and/or epidural abscess
* Protracted fever, night sweats, murmur, heart failure – suggestive of infective endocarditis
* Abdominal pain, especially LUQ pain – may reflect splenic infarction (due to embolic phenomenal [endocarditis?])
* CVA tenderness – may reflect renal infarction or psoas abscess
* Headache, difficulty breathing – septic emboli
What is the clinical approach to SAB? - physical exam
Serial bedside examinations to detect complications that may develop after initial evaluation
* Metastatic seeding may occur within the first few days of hospitalization but may not be clinically apparent
for several weeks
* 39% of patients with vertebral osteomyelitis and 57% of patients with epidural abscess had the diagnosis on admission
INFECTIOUS DISEASES CONSULTATION
* Do it, even if not mandatory!
* ID consults associated with decreased mortality, fewer relapses, and decreased readmission rates
Repeat blood cultures q48-72h to document clearance
What are peripheral manifestations of endocarditis?
osler’s nodes, janeway lesions, splinter hemorrhages, petechiae, roth spots
What are osler’s nodes?
Purplish or erythematous subcutaneous papules or nodules that appear on the pads of the fingers and toes (painful and tender)
What are janeway lesions?
- Hemorrhagic, painless plaques on palms of hands or
soles of feet - Embolic in origin
What are splinter hemorrhages?
Thin, linear hemorrhages under the nail beds of fingers or toes
What is petechiae?
- Small, erythematous, painless hemorrhagic lesions on anterior trunk, conjunctivae, buccal mucosa, and palate
- Result from either local vasculitis or emboli
What are roth spots?
Oval, pale, retinal lesions surrounded by hemorrhage
What is the diagnostic evaluation in SAB?
- Blood cultures – always clinically significant regardless of number of positive blood cultures
- Repeat blood cultures (2 sets) q48-72h until negative
- Echocardiography – all patients with SAB!!
- Transthoracic echocardiography (TTE) performed FIRST
- Transesophageal echocardiography (TEE) usually performed after TTE (preferred for MRSA bacteremia): All patients with community-acquired SAB; may not be needed for hospital-acquired SAB; More sensitive that TTE for identifying vegetation size/location; Better for identifying intracardiac abscesses and valve perforation; Most sensitive when performed 5-7 days after onset of bacteremia; May repeat if negative but highly clinical suspicion of IE
What if urine cultures are positive for staph aureus?
- S. aureus is NOT a common organism in UTIs.
- Prevalence of S. aureus bacteriuria in patients with SAB is 8-40%
- Associated with increased mortality
- Translocation of S. aureus from blood to urine due to hematogenous seeding and development of microabscesses
Catheter and prosthetic device management
- S. aureus has many virulence factors that allow the organism to colonize and infect metal, plastic surfaces, catheters, and other prosthetic devices; may be infected without any clinical signs/symptoms of infection.
- Consider all IV catheters and prosthetic devices to be infected in patients with SAB until infection ruled out: Attempt to remove all prosthetic devices; if not, significant increase in risk of relapse; If unable to remove, may add rifampin and may need long-term suppressive therapy
- Catheter management: Short term catheters–remove ASAP; Long-term catheters–remove unless major contraindication; Replace catheters when blood cultures negative for 48-72 hours
What is the empiric treatment of S. aureus bacteremia?
- Prompt source control and antimicrobial therapy
- Empirically cover MSSA and MRSA (rapid diagnostics): Vancomycin or Daptomycin
What is the treatment of MRSA bacteremia?
- Vancomycin
- Daptomycin: May be used in patients with septic pulmonary emboli
- Addition of gentamicin or rifampin to vancomycin is not recommended
- Limited data with ceftaroline
What is the treatment of MSSA bacteremia?
nafcillin, oxacillin, or cefazolin
When would you use combination therapy for MRSA bacteremia?
It may be reasonable to employ combination therapy with a PBP-1 active β-lactam or ceftaroline with vancomycin or daptomycin early in MRSA bacteremia treatment course, especially in patients at highest risk of treatment failure and death.
What is the duration of treatment for uncomplicated SAB?
14 days of IV therapy from 1st negative blood culture
What is the duration of treatment for complicated SAB?
4 weeks
What is the duration of treatment for complicated SAB with metastatic infection?
6-8 weeks
Bacteremia due to other gram-positive cocci: streptococci
- Treatment duration:14 days (IV→PO)
- S.pyogenes, S.agalactiae–penicillin IV (q4h or CI)→high dose amoxicillin PO * S.pneumoniae–ceftriaxone or penicillin (if susceptible)
Bacteremia due to other gram-positive cocci: enterococci
- Treatment duration: 7 days
- E.faecalis: Ampicillin (majority are susceptible); if amp-R or β-lactam allergy – vancomycin or daptomycin
- E.faecium: If vanA and vanB negative – vancomycin; If vanA or vanB positive (VRE) – daptomycin, linezolid
What is the treatment of uncomplicated gram-negative bacteremia?
treatment duration: 7 days (total days of therapy, not from 1st day of negative blood cultures, do not always have to repeat blood cultures like in S. aureus!)
* IV → PO when clinically improved and able to take PO: PO–frequently TMP/SMZ, FQ, or β-lactam
What is the treatment duration of uncomplicated gram-negative bacteremia?
Take home point: Longer is not always better. 7 days of therapy had comparable outcomes as compared to 14 days in patients with uncomplicated gram-negative bacteremia
What is the treatment duration for enterobacteriaceae bacteremia?
Take home point: Longer duration of therapy is not always better.
less than 10 days
What is the antibiotic therapy duration for P. aeruginosa bacteremia?
short course (median 9 days)
Clinical pearls + key takeaways
- Mandatory repeat blood cultures q48-72h until negative for S. aureus, usually not needed for other bacteremia
- Empiric therapy for MRSA: Vancomycin (AUC-guided dosing) or Daptomycin (higher dose in severe infections)
- MSSA treatment: Beta-lactams (nafcillin, oxacillin, cefazolin) are superior to vancomycin
- Shorter treatment durations (7-10 days) are effective for most cases of bacteremia including uncomplicated Gram- negative bacteremia
