Feasibility of rapid polymerase chain reaction for detection of methicillin-resistant Staphylococcus aureus colonization among emergency department patients with abscesses

Michael S Pulia,¹ Mary Calderone,² Brad Hansen,² Christine E Stake,³ Mark Cichon,³ Zhanhai Li,⁴ Nasia Safdar<sup>5

1</sup>Division of Emergency Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA; ²Loyola University Stritch School of Medicine, Maywood, IL, USA; ³Department of Emergency Medicine, Loyola University Medical Center, Maywood, IL, USA; ⁴University of Wisconsin Department of Biostatistics and Medical Informatics, Madison, WI, USA; ⁵William S Middleton Veterans Affairs Medical Center and the Department of Medicine, Division of Infectious Disease, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA

Purpose: In the era of community-associated methicillin-resistant Staphylococcus aureus (MRSA), clinicians face a difficult challenge when selecting antibiotics to treat abscesses. The lack of rapid diagnostics capable of identifying the causative organism often results in suboptimal antibiotic stewardship practices. Although not fully elucidated, the association between MRSA colonization and subsequent infection represents an opportunity to enhance antibiotic selectivity. Our primary objective was to examine the feasibility of utilizing a rapid polymerase chain reaction (PCR) system (Cepheid’s GeneXpert^®) to detect MRSA colonization prior to patient discharge in the emergency department (ED).
Methods: This feasibility study was conducted at a tertiary care, urban, academic ED. Patients presenting with a chief complaint related to a potential abscess during daytime hours over an 18-week period were screened for eligibility. Subjects were enrolled into either the PCR swab protocol group (two-thirds) or traditional care group (one-third). PCR swabs were obtained from known MRSA carriage sites (nasal, pharyngeal) and the superficial aspect of the wound.
Results: The two groups were similar in terms of demographics, abscess location, and MRSA history. The PCR results were available prior to patient discharge in 100% of cases. The turnaround times in minutes for the PCR swabs were as follows: nasal 73 ± 7, pharyngeal 82 ± 14, and superficial wound 79 ± 17. No significant difference in length of stay was observed between the two groups. The observed ideal antibiotic selection rates improved by 45% in the PCR group, but this trend was not significant (P = 0.08).
Conclusion: When collected in triage, PCR swabs demonstrated turnaround times that were effective for use in the ED setting. Utilizing a rapid PCR MRSA colonization detection assay for ED patients with abscesses did not adversely impact the length of stay. Real-time determination of MRSA colonization may represent an opportunity to improve antibiotic selectivity in the treatment of abscesses.

Keywords: MRSA, carrier state, antibiotic stewardship, PCR, multiple drug resistant organisms, MDROs