View source for Staphylococcus aureus bacteremia

==Background==
===Classification===

*'''Community-onset:''' positive blood culture obtained within 48 hours of presentation
*'''Nosocomial:''' positive blood culture obtained after 48 hours of presentation

===Etiology===

*IVDU
*Poor dentition
*Dental work

==Clinical Manifestations==

*Often non-specific fevers and chills, diagnosed on blood cultures
*May have back pain unrelated to spinal osteomyelitis
*May present with focus of metastatic disease

===Prognosis===

*Associated with about 30% mortality[[CiteRef::bai2022st]]
*Mortality halved by ID consult in observational studies
*Prognosis worse with
**Increased age
**Female sex
**[[Pneumonia]] or source unknown
**[[Dementia]]
**Increasing comorbidities
**[[Shock]] at time of presentation
**Institutionalized patient

==Investigations==

*Repeat blood cultures every 24 to 48 hours until negative
*Transthoracic echo (TTE) or transesophageal echo (TEE)
**A modern TTE that is good-quality and shows normal valves is quite good, though TEE is still better
**TEE is strongly suggested in certain cases:
***[[Embolic stroke|Cerebral]] or peripheral emboli
***[[Meningitis]]
***[[Cardiovascular implantable electronic device infection|Implantable cardiac device]] or [[prosthetic heart valve]]
***Prior [[infective endocarditis]]
***Native valve disease
***Injection drug use
***Persistent bacteremia beyond 72 hours
**Can also use [[VIRSTA score]] to decide if they need TEE[[CiteRef::tubiana2016th]]
***Highest sensitivity (~99%), though specificity only 35%
***The high sensitivity gives very high negative predictive value of ~99%
***Likely preferred to others like the [[PREDICT score]], which has lower sensitivity though higher specificity[[CiteRef::van der vaart2021pr]]

==Management==

*Infectious diseases consultation

=== Echocardiography ===
*Must rule out endocarditis! TTE, followed by TEE if suspicion remains high (see [[VIRSTA score]])
**Low risk for endocarditis (no TEE) if all of the following:
***No intracardiac device
***Sterile follow-up blood cultures within 4 days from the initial set
***No hemodialysis
***Nosocomial acquisition
***Absence of secondary foci
***No clinical signs of endocarditis
**Uncomplicated if all of the following:
***Endocarditis is excluded
***No implanted prostheses
***Blood cultures clear by 2-4 days
***Defervesces within 72 hours
***No evidence of metastases
***+/- identified source has been removed

=== Antimicrobial Therapy ===
*Two-week course acceptable if uncomplicated, otherwise 4-6 weeks based on clinical course and underlying foci of infection
*MSSA: [[cloxacillin]] 2g IV q4h for 2 weeks ([[cefazolin]] as an alternative)
*MRSA: [[vancomycin]] 1g IV q12h for 2 weeks
**Adjust based on serum trough before every fourth dose
**Target trough 15-20
*Standard of care is still currently IV therapy for the duration, though there is emerging evidence for treating a number of deep-seated infections ([[osteomyelitis]], [[Infective endocarditis|endocarditis]]) with early oral antibiotics, including infections caused by [[Staphylococcus aureus]]

=== Dosing ===

==== Penicillin- or Methicillin-Susceptible Strains ====
{| class="wikitable"
!Antibiotic
!Renal Function
!Standard Dose
!Critical Illness Dose†
|-
| rowspan="4" |[[benzylpenicillin]] (pen G)
| eGFR >50
| 1.8 g (3 MU) q4h 
| 2.4 g (4 MU) q4h
|-
|eGFR 10-50
|1.8 g (3 MU) q6h 
|1.8 g (3 MU) q4h
|-
|eGFR <10
|1.8 g (3 MU) load, then 1.2 g (2 MU) q8h
|2.4 g load, then 1.2 g (2 MU) q6h
|-
| CRRT 
| 1.2 g (2 MU) q6h
|1.8 g (3 MU) q6h
|-
| rowspan="3" |[[flucloxacillin]]
|eGFR ≥10
|2 g q6h
|2 g q4h 
|-
|eGFR <10
|1 g q6h
|1 g q4h
|-
|CRRT
|2 g q6h
|2 g q6h
|-
|[[cloxacillin]]
|any 
|2 g q4h
|2 g q4h
|-
| rowspan="4" |[[cefazolin]]
|eGFR >40
|2 g q8h
|2 g q6h
|-
|eGFR 20-40
|2 g q12h
| 2 g q12h
|-
|eGFR <20
|1 g q24h 
|1 g q24h
|-
|CRRT
|2 g q12h
|2 g q12h
|}*† Critical illness dosing should be used for patients with septic shock, admitted to ICU, with endocarditis, or with CNS infection (excluding spinal epidural abscess)
**May be decreased to standard dosing once no longer requiring mechanical ventilation or vasopressors for at least 24 hours

===== Methicillin-Resistant Strains =====

====== Vancomycin Dosing ======
* [[Vancomycin]] dosing may follow local guidelines
*Includes loading dose of 25 mg/kg (max 3 g) if considered appropriate by the physician, then maintenance dosing at 15-20 mg/kg q12h, adjusted to target AUC 400-600 mg h/L or trough 10-20 mg/L

====== Daptomycin Dosing ======
{| class="wikitable"
!Renal Function
!Suggested Dose
|-
|eGFR >50
|8-10 mg/kg q24h 
|-
|eGFR 11-50
|6-8 mg/kg q24h
|-
|eGFR ≤10
|8 mg/kg q48h
|-
|CRRT
|8 mg/kg q48h
|-
|HD
|8 mg/kg q48h, given after dialysis
|}

====== Adjunctive Cefazolin Dosing ======
{| class="wikitable"
!Renal Function
!Suggested Dose
|-
| CrCl >40
|2 g q8h
|-
|CrCl 20-40
| 2 g q12h
|-
| CrCl <20
|1 g q24h
|-
|CRRT
| 1 g q8h or 2 g q12h
|-
|HD
|2 g after each dialysis session
|}

==== Early Oral Switch ====
{| class="wikitable"
!Silo
!IV Antibiotic
!Suggested First-Line
! Suggested Second-Line (ordered)
|-
| rowspan="2" | PSSA
|[[benzylpenicillin]]
|[[amoxicillin]]
|[[flucloxacillin]]/[[dicloxacillin]], [[cefalexin]]/[[cefadroxil]], [[linezolid]]
|-
|([[Flucloxacillin|flu]])[[cloxacillin]]
|[[flucloxacillin]]/[[dicloxacillin]] 
|[[amoxicillin]], [[cefalexin]]/[[cefadroxil]], [[linezolid]]
|-
| rowspan="2" |MSSA 
|([[Flucloxacillin|flu]])[[cloxacillin]]
|[[flucloxacillin]]/[[dicloxacillin]]
|[[cefalexin]]/[[cefadroxil]], [[linezolid]]
|-
|[[cefazolin]]
|[[cefalexin]]/[[cefadroxil]]
|[[flucloxacillin]]/[[dicloxacillin]], [[linezolid]]
|-
| rowspan="2" |MRSA
|[[vancomycin]]/[[daptomycin]]
|[[linezolid]]
|[[fluoroquinolone]]+[[rifampin]], [[TMP-SMX]], [[fusidic acid]]+[[rifampin]]
|-
|[[vancomycin]]/[[daptomycin]]+[[cefazolin]]
|[[linezolid]]
|[[fluoroquinolone]]+[[rifampin]], [[TMP-SMX]], [[fusidic acid]]+[[rifampin]]
|}
{| class="wikitable"
!Antibiotic
!Renal Function
!Suggested Dose
!Notes
|-
| rowspan="5" |[[amoxicillin]]
|normal
|1 g q6h ± [[probenecid]]
|
|-
|CrCl 10-30
|1 g q8h
|
|-
|CrCl <10
|1 g q12h
|
|-
|CRRT
|1 g q8h
|
|-
|HD/PD
|1 g q12h
|
|-
| rowspan="6" |[[cefadroxil]]
|normal
|1 g q12h
|
|-
|CrCl 10-50
|1 g then 500 mg q12h
|
|-
|CrCl <10
|1 g then 500 mg q36h
|
|-
|CRRT
|1 g then 500 mg q12h
|
|-
|HD
|1 g then 1 g post-HD
|
|-
|PD
|500 mg q24h
|
|-
| rowspan="4" |[[cefalexin]]
|normal
|1 g q6h ± [[probenecid]]
|
|-
|CrCl <10
|1 g q12h
|
|-
|CRRT
|1 g q6h
|
|-
|HD/PD
|1 g q12h
|
|-
| rowspan="4" |[[ciprofloxacin]]
|normal
|750 mg q12h
|
|-
|CrCl <30
|750 mg q24h
|
|-
|CRRT
|250-500 mg q12h
|
|-
|HD/PD
|750 mg q24h
|
|-
|[[clindamycin]]
|any
|450 mg q8h
|
|-
|[[cloxacillin]]
|any
|1 g q6h
|
|-
| rowspan="4" |[[dicloxacillin]]
|normal
|1 g q6h
|
|-
|CrCl <10
|1 g q8h
|
|-
|CRRT
|1 g q6h
|
|-
|HD/PD
|1 g q8h
|
|-
|[[doxycycline]]
|any
|100 mg q12h
|
|-
| rowspan="4" |[[flucloxacillin]]
|normal
|1 g q6h
|
|-
|CrCl <10
|1 g q8h
|
|-
|CRRT
|1 g q6h
|
|-
|HD/PD
|1 g q8h
|
|-
|[[fusidic acid]]
|any
|500 mg q24h
|
|-
| rowspan="5" |[[levofloxacin]]
|normal
|750 mg q24h
|
|-
|CrCl 20-49
|750 mg q48h
|
|-
|CrCl <20
|750 mg then 500 mg q48h
|
|-
|CRRT
|250 mg q24h
|
|-
|HD/PD
|750 mg then 500 mg q48h
|
|-
| rowspan="4" |[[linezolid]]
|normal
|600 mg q12h
|
|-
|CrCl <10
|600 mg q24h
|
|-
|CRRT
|600 mg q12h
|
|-
|HD/PD
|600 mg q24h
|
|-
|[[moxifloxacin]]
|any
|400 mg daily
|
|-
| rowspan="3" |[[probenecid]]
|CrCl ≥60
|500 mg with each dose of β-lactam
|
|-
|CrCl 30-60
|250 mg with each dose of β-lactam
|
|-
|CrCl <30
|avoid use
|
|-
| rowspan="2" |[[rifampin]]
|any (weight <60kg)
|600 mg daily
|
|-
|any (weight >60 kg)
|900 mg daily
|
|-
|[[tedizolid]]
|any
|200 mg q24h
|
|-
| rowspan="4" |[[TMP-SMX]]
|normal
|2 DS q12h or 1 DS q8h
|
|-
|CrCl 26-50
|normal dose for 14 days then 1 DS q12h
|
|-
|CrCl 15-25
|normal dose for 3 days then 2 DS q24h
|
|-
|CrCl <15
|avoid use
|
|}

==== Adjunctive Clindamycin ====
*[[Clindamycin]] 600 mg IV q8h for 5 days as adjunctive therapy regardless of clindamycin susceptibility
*Alternative is 450 mg p.o. q8h for 5 days, though preference for IV
==Further Reading==

{{DISPLAYTITLE:''Staphylococcus aureus'' bacteremia}}
[[Category:Endovascular infections]]
[[Category:Bacteremias]]