The Role of Negative Methicillin-Resistant Staphylococcus aureus Nasal Surveillance Swabs in Predicting the Need for Empiric Vancomycin Therapy in Intensive Care Unit Patients

Abstract

OBJECTIVES The role of methicillin-resistant Staphylococcus aureus (MRSA) nasal surveillance swabs (nasal swabs) in guiding decisions about prescribing vancomycin is unclear. We aimed to determine the likelihood that patients with negative MRSA nasal swabs develop subsequent MRSA infections; to assess avoidable vancomycin days for patients with negative nasal swabs; and to identify risk factors for having a negative nasal swab and developing a MRSA infection during the intensive care unit (ICU) stay. METHODS This retrospective cohort study was conducted in 6 ICUs at a tertiary-care hospital from December 2013 through June 2015. The negative predictive value (NPV), defined as the ability of a negative nasal swab to predict no subsequent MRSA infection, was calculated. Days of vancomycin continued or restarted after 3 days from the collection time of the first negative nasal swab were determined. A matched case-control study identified risk factors for having a negative nasal swab and developing MRSA infection. RESULTS Of 11,441 patients with MRSA-negative nasal swabs, the rate of subsequent MRSA infection was 0.22%. A negative nasal swab had a NPV of 99.4% (95% confidence interval [CI], 99.1%-99.6%). Vancomycin was continued or started after nasal swab results were available in 1,431 patients, translating to 7,364 vancomycin days. No risk factors associated with MRSA infection were identified. CONCLUSIONS In our hospital with a low prevalence of MRSA transmission, a negative MRSA nasal swab was helpful in identifying patients with low risk of MRSA infection in whom empiric vancomycin therapy could be stopped and in whom the subsequent initiation of vancomycin therapy during an ICU admission could be avoided. Infect Control Hosp Epidemiol 2018;39:290-296.

The impact of a multimodal approach to vancomycin discontinuation in hematopoietic stem cell transplant recipients (HSCT) with febrile neutropenia (FN)

“…Nasal colonization with MRSA has been shown to be a risk factor for developing a clinical MRSA infection . In two large studies, a negative MRSA nasal swab has been shown to have a negative predictive value (NPV) greater than 99% for the development of future MRSA infections . Dangerfield B, et al analyzed 435 patients’ MRSA nasal swabs and the development of pneumonia.…”

“…Chotiprasitsakul D, et al analyzed 12 215 patients’ MRSA nasal swabs in the ICU and demonstrated a NPV of 99.4% for MRSA infection at any timepoint. Only 0.22% of the patients who had a negative MRSA nasal swab developed a MRSA infection . In this study, the negative MRSA nasal swab resulted in potentially 7364 days of avoidable vancomycin use .…”

“…Only 0.22% of the patients who had a negative MRSA nasal swab developed a MRSA infection . In this study, the negative MRSA nasal swab resulted in potentially 7364 days of avoidable vancomycin use . Although not validated in the immunosuppressed population, our criteria incorporated the negative MRSA nasal swab as a tool for de‐escalation based on the above literature.…”

Clinical Utility of Methicillin‐Resistant Staphylococcus aureus Nasal Screening for Antimicrobial Stewardship: A Review of Current Literature

“…In the 11,441 patients with negative surveillance screening during ICU admission, only 25 patients (0.22%) developed a clinically significant MRSA infection requiring treatment resulting in an NPV of 99.4% (95% confidence interval [CI] 99.1–99.6). The investigators estimated that 7364 days of vancomycin therapy could have been avoided if vancomycin had been discontinued in the patients with negative swab results . This study excluded patients with a history of MRSA from surveillance cultures or clinical cultures within the previous 12 months .…”

“…25 A recently published retrospective cohort study of 11,882 patients across six intensive care units (ICUs) in a 19-month period investigated the utility of the MRSA nasal swab to predict any MRSA infection. 26 In the 11,441 patients with negative surveillance screening during ICU admission, only 25 patients (0.22%) developed a clinically significant MRSA infection requiring treatment resulting in an NPV of 99.4% (95% confidence interval [CI] 99.1-99.6). The investigators estimated that 7364 days of vancomycin therapy could have been avoided if vancomycin had been discontinued in the patients with negative swab results.…”