Integrating a Rapid Diagnostic Test and Antimicrobial Stewardship: Optimizing Discharge Antibiotics in Skin and Soft Tissue Infections (SSTI)
S. aureus (SA) is the leading cause of SSTI. Empiric antibiotics for SSTI should have activity against methicillin-resistant SA (MRSA) and methicillin-susceptible SA (MSSA). Clindamycin is highly utilized for SSTI; however, clindamycin-resistance rates in MSSA are nearly 20% at our institution. Differentiation between MRSA and MSSA using a rapid antigen test that detects penicillin-binding protein (PBP2a) for methicillin-resistance prior to final susceptibility could allow early targeted antimicrobial therapy. This quality-improvement project aims to optimize antibiotic usage in SA SSTIs through utilization of the PBP2a rapid diagnostic test.
Baseline antimicrobial use for inpatient SA SSTIs was collected for 1 year prior to implementation. Live education regarding interpretation of the PBP2a test was provided to hospitalists and housestaff. The test was implemented for SA SSTI in January 2014. Test results were faxed to the Antimicrobial Stewardship Program (ASP) and reviewed; recommendations were made if necessary. Data was collected to assess impact of PBP2a results on antimicrobial prescribing. Targeted therapy for MSSA was defined as effective beta-lactam therapy.
163 patients were evaluated prior to PBP2a implementation. 44/163 (27%) were discharged prior to final susceptibility. Of those, 24 (55%) patients were infected with MSSA and 20 (83%) were prescribed clindamycin; 4 (17%) patients had clindamycin-resistant MSSA. In the post-PBP2a implementation interim analysis, 36 patients were reviewed; 14 (39%) patients were discharged prior to final susceptibility. Of those, 8 (57%) patients had MSSA and 2 (25%) of those were discharged with clindamycin. Among all patients, ASP intervened in 7 cases (19%); no intervention was made if therapy was appropriate (n = 13), if the team changed to an appropriate therapy (n = 9), if Infectious Diseases service was involved (n = 5), or if patient was already discharged (n = 2).
In this interim analysis, targeted MSSA therapy increased from 17% to 75% in patients discharged prior to final susceptibility. It appears that rapid diagnostics in combination with education likely improves targeted antibiotic therapy for SA SSTI. Further audit and feedback by ASP may improve antibiotic mismatch rates.
J. Newland, Pfizer: Grant Investigator, Grant recipient
R. Selvarangan, Alere: Investigator, Research grant
J. Goldman, Pfizer: Grant Investigator, Research grant