3Consider de-escalating MRSA coverage if MRSA nares negative within prior 7 days
4If ceftriaxone was chosen initially and patient is clinically improving, continue ceftriaxone. If patient is hemodynamically unstable or clinically worsening, broaden to antipseudomonal agent:
No penicillin allergy: pip/tazo*
Mild-mod penicillin allergy: cefepime*
Severe penicillin allergy: aztreonam or levofloxacin*
*Contact ASP Pharmacist or ID Fellow for approval of pip/tazo, cefepime, and levofloxacin (pip/tazo and cefepime do not need approval in the ICU)
Antibiotic dosing for HAP/VAP (refer to IV antimicrobial dosing section for renal dose adjustments and vancomycin dosing/monitoring guidance in Antimicrobial guidebook)
- Piperacillin/tazobactam (pip/tazo) 4.5 gm IV q6h
- Cefepime 2 gm IV q8h
- Ceftriaxone 2 gm IV q24h
- Vancomycin 20 mg/kg IV one-time loading dose + maintenance dose targeting AUC 500-600 mg*h/L
- Aztreonam 2 gm IV q8h
- Levofloxacin 750 mg IV/PO q24h
VASF Respiratory Culture Considerations
- Final results are available 2 days after collection (i.e., No further work up, or "bacteriology final report")
- If additional work up is required, contact the micro lab to request organism ID and antibiotic susceptibilities
- Micro lab will discard plates after 5 days
Role and Interpretation of Methicillin-Resistant S. aureus (MRSA) Nares Results in Context of Hospital-Acquired and Ventilator-Associated Pneumonia (HAP/VAP)
Collecting a MRSA nares culture/PCR is recommended for all patients initiating anti-MRSA therapy (e.g. vancomycin) for suspected HAP or VAP.
How to interpret a negative MRSA nares result in patient with possible HAP/VAP:
A negative MRSA nares culture or PCR indicates the patient is less likely to be colonized with MRSA. Multiple studies indicate that a negative MRSA nares culture or PCR carries a high negative predictive value for MRSA pneumonia (> 95%),3-6 even when collected prior to onset of pneumonia.3,5 If a patient’s MRSA nares is negative, their likelihood of having MRSA pneumonia is exceedingly low and anti-MRSA therapy (e.g. vancomycin) can reasonably be discontinued or withheld.
How to interpret a positive MRSA nares result in patient with possible HAP/VAP:
A positive MRSA nares culture or PCR indicates that the patient is colonized with MRSA. Patients with a known positive MRSA nares culture/PCR who develop a HAP or VAP should be initiated on antibiotics including empiric anti-MRSA therapy (e.g. vancomycin). However, antibiotics should be tailored to respiratory gram stain & culture results. Stop vancomycin at 48 hours if no MRSA isolated from clinical cultures. If a patient's MRSA nares culture or PCR results positive after the patient has been started on antibiotics to treat HAP/VAP, no change in therapy is recommended (in other words – no need to add empiric anti-MRSA therapy) provided the patient is stable and clinically improving.