2024 Eastern States Conference

TITLE: Utilization of methicillin resistant staphylococcus aureus nares to guide vancomycin de-escalation in skin and soft tissue infection 

AUTHORS:  Jessica Zagari, PharmD, John Cao, PharmD, BCPS, BCIDP, Sean M. Stainton, PharmD, Abhimanyu Aggarwal, MD, Nabila Ahmed-Sarwar, PharmD, BCPS, BCACP, CDCES, BC-ADM 

OBJECTIVE: Determine the clinical implication of using a MRSA nares surveillance result to de-escalate vancomycin in SSTIs 

SELF ASSESSMENT QUESTION: Patient AB is a 52-year-old male who presented to the ED with complaints of leg pain and swelling. AB has a past medical history of hypertension, otherwise healthy with no recent hospitalizations or antibiotic use. His white blood count is 16.2x10^3 cells/mL and heart rate 120 bpm. All other findings are normal. No wound culture obtained. AB was admitted to the hospital with uncomplicated cellulitis and is on day 2 of intravenous vancomycin 1,000mg every 12 hours. A MRSA nares surveillance was collected and resulted as negative. AB’s white count and heart rate have now normalized with reduced leg swelling. What would you recommend for AB at this time?
A. Discontinue vancomycin and start PO linezolid
B. Discontinue vancomycin and start PO doxycycline and cephelexin
C. Discontinue vancomycin and start PO cephalexin
D. Continue vancomycin 

BACKGROUND: There is limited data on the negative predictive value of methicillin-resistant Staphylococcus aureus (MRSA) nares surveillance for skin and soft tissue infections (SSTI) and a notable gap in clinical outcomes following de-escalation of vancomycin 

METHODOLOGY: A prospective chart review was conducted for hospitalized patients ≥18 years of age with a SSTI initiated empirically on vancomycin. Exclusion criteria included perioperative prophylaxis, hemodialysis, contraindications to vancomycin, prior de-escalation, history of intravenous drug use or necrotizing fasciitis. The primary outcome looked to compare nares surveillance and wound culture results for concordance. The secondary outcome looked to assess clinical outcomes following de-escalation of vancomycin. In those whose vancomycin regimen was de-escalated, the patient was evaluated for 48-hours for signs of clinical deterioration, including signs of systemic inflammatory response syndrome criteria and/or reinitiation of vancomycin due to worsening infection. McNemar test along with predictive values will be used to analyze the primary outcome. Descriptive statistics will be used to analyze clinical outcomes after de-escalation. 

RESULTS: Of the 73 patients included to date, 29 patients had both MRSA nares and culture results collected. Preliminary analysis has shown a concordance of 82.8% with negative MRSA nares result and non-MRSA culture result (p=0.684). One patient clinically deteriorated due to non-infectious complications after vancomycin de-escalation. We anticipate these interim results to hold true, and study findings should result in a high negative correlation between MRSA nares surveillance and the occurrence of MRSA in SSTIs. Moreover, we expect that discontinuing vancomycin based on negative MRSA nares surveillance results will not adversely affect clinical outcomes. Research is ongoing, finalized results to be presented upon completion. 

CONCLUSIONS: Our research lends further support for clinical utility of MRSA nares de-escalation for vancomycin in the majority of patients with SSTIs. This approach has the potential to reduce the duration of vancomycin therapy without negatively impacting clinical outcomes. Research is ongoing, finalized conclusions to be presented upon completion.