Negative Nasal MRSA PCR Rules Out Future MRSA Infections in Trauma ICU Patients

Author(s):
Kaely Miller; Seth Garner; Kristin Rebo; Andrew Nunn; Greg Stettler

Background:

Studies have shown that Methicillin resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) swabs aid in de-escalating and decreasing the duration of antibiotic use in respiratory infections. Recent data suggests the utility of MRSA PCR swabs in predicting future MRSA infections in a mixed ICU population, however, little data has evaluated the utility of MRSA PCR swabs in trauma patients. The aim of this study is to determine if MRSA PCR screening swabs are associated with future MRSA infections in trauma patients admitted to the ICU.

Hypothesis:

Negative MRSA PCRs are associated with negative MRSA infections in trauma patients admitted to the ICU.

Methods:

Trauma patients admitted to the ICU with a nasal MRSA PCR from July 2022-September 2023 were retrospectively evaluated. Demographics, as well as complication rates, cultures obtained, days from PCR to culture, and positivity of a MRSA infection were collected.  The Mann Whitney test was used for continuous variables. The Chi-squared test was use for categorical variables.

Results:

In the study period, 40 injured patients were identified with a MRSA PCR. Most patients were male (78%), suffered a blunt mechanism (83%), and had a 28-day mortality rate of 58%. Of the 40 injured patients, five (12.5%) had a positive MRSA PCR screen. Compared to patients with a negative PCR, those with a positive PCR were older (61 vs 46 years, p<0.05) and had a less rapid heart rate (80 vs 100 bpm, p<0.05). In the 5 patients with a positive PCR, 9 cultures were obtained (mean 10 days from PCR). One culture (11%) resulted in a positive MRSA infection. Of the 35 patients that had a negative PCR, 90 cultures were obtained (mean 10 days from PCR). This included 46 blood cultures, 11 wound cultures, 32 respiratory cultures, and 1 urine culture. No patient that had a negative PCR had a positive MRSA infection.

Conclusions:

The incidence of MRSA positive infections in patients with a negative MRSA PCR is zero.  Based on these findings, there should be consideration of withholding empiric MRSA coverage in trauma ICU patients with a negative MRSA PCR, which may aid in reducing unnecessary antibiotic initiation and healthcare costs. Larger studies are needed to validate these findings and help delineate patients for which empiric MRSA coverage can be withheld.