78. Impact of Methicillin-Resistant Staphylococcus aureus (MRSA) Nares Screen on Vancomycin Utilization for Respiratory Tract Infections

Abstract Background S. aureus, including MRSA, is a common colonizer of the nares. Recent data have shown that a negative MRSA nares screen by PCR has a negative predictive value of 98%. This implies that the absence of colonization can significantly reduce empiric vancomycin utilization. This study aimed to determine the utilization of MRSA nares screening on patients receiving vancomycin for respiratory tract infections (RTI) following the addition of the screen to the institutional RTI management guidelines. Methods This was a retrospective chart review of adult inpatients presenting to two community-teaching hospitals who were prescribed vancomycin for the treatment of RTIs. Patients were divided into pre-guideline (Jan-Feb 2019), post-guideline 1 (Jan-Feb 2020), and post-guideline 2 (Jan-Feb 2021) groups. The primary endpoint was the difference in percent of vancomycin orders discontinued within 24 hours of a negative screen. Secondary endpoints included the percent of screens ordered, re-initiation of vancomycin within seven days for RTI, and total vancomycin days of therapy (DOT) per 1000 patient days (PD). Results Of 493 vancomycin orders screened, 100 orders in each arm were analyzed. There was an absolute increase of 20.6% in vancomycin orders discontinued within 24 hours of a negative screen between the pre-guideline and post-guideline 2 groups (59.1% vs. 79.7%, p = 0.0177). When compared to the pre-guideline group, utilization of the screen increased by 15% in the post-guideline 1 group (48% vs. 63%, p = 0.0328) and 26% in the post-guideline 2 group (48% vs. 74%, p = 0.000164). There was no difference in re-initiation of vancomycin. A statistically significant reduction in total vancomycin DOT/1000PD from the pre-guideline to the post-guideline 1 and 2 groups (66 to 63 to 60, respectively) was also observed. Conclusion The addition of the MRSA nares screen to the institutional RTI guidelines increased utilization of the test and demonstrated a reduction in vancomycin utilization. With an increase in education, prospective audit and feedback, and prescriber comfort with the use of the MRSA nares screen in the post-guideline 2 group, there was significant improvement in MRSA nares screen utilization, vancomycin discontinuation after a negative screen, and vancomycin utilization. Disclosures All Authors: No reported disclosures

Background. S. aureus, including MRSA, is a common colonizer of the nares. Recent data have shown that a negative MRSA nares screen by PCR has a negative predictive value of 98%. This implies that the absence of colonization can significantly reduce empiric vancomycin utilization. This study aimed to determine the utilization of MRSA nares screening on patients receiving vancomycin for respiratory tract infections (RTI) following the addition of the screen to the institutional RTI management guidelines.
Methods. This was a retrospective chart review of adult inpatients presenting to two community-teaching hospitals who were prescribed vancomycin for the treatment of RTIs. Patients were divided into pre-guideline (Jan-Feb 2019), post-guideline 1 (Jan-Feb 2020), and post-guideline 2 (Jan-Feb 2021) groups. The primary endpoint was the difference in percent of vancomycin orders discontinued within 24 hours of a negative screen. Secondary endpoints included the percent of screens ordered, re-initiation of vancomycin within seven days for RTI, and total vancomycin days of therapy (DOT) per 1000 patient days (PD).

Results.
Of 493 vancomycin orders screened, 100 orders in each arm were analyzed. There was an absolute increase of 20.6% in vancomycin orders discontinued within 24 hours of a negative screen between the pre-guideline and post-guideline 2 groups (59.1% vs. 79.7%, p = 0.0177). When compared to the pre-guideline group, utilization of the screen increased by 15% in the post-guideline 1 group (48% vs. 63%, p = 0.0328) and 26% in the post-guideline 2 group (48% vs. 74%, p = 0.000164). There was no difference in re-initiation of vancomycin. A statistically significant reduction in total vancomycin DOT/1000PD from the pre-guideline to the post-guideline 1 and 2 groups (66 to 63 to 60, respectively) was also observed.
Conclusion. The addition of the MRSA nares screen to the institutional RTI guidelines increased utilization of the test and demonstrated a reduction in vancomycin utilization. With an increase in education, prospective audit and feedback, and prescriber comfort with the use of the MRSA nares screen in the post-guideline 2 group, there was significant improvement in MRSA nares screen utilization, vancomycin discontinuation after a negative screen, and vancomycin utilization.
Disclosures. Background. Empiric use of vancomycin is common in clinical practice. Currently there is strong evidence to support the use of MRSA nasal screening to predict the absence of MRSA in respiratory infections; however, minimal data exists regarding its utility as a de-escalation tool beyond pulmonary indications. Furthermore, MRSA nasal PCR has been shown to be a more efficient way to detect the presence of MRSA colonization than traditional culture methods. The purpose of this study was to evaluate the correlation between results of MRSA nasal PCR assays and blood or bone/soft tissue cultures.
Methods. This was a retrospective study of patients who presented to any of three hospitals part of an integrated health system in Des Moines, Iowa, from March 1, 2019 to February 29, 2020. Included patients were those who underwent MRSA nasal PCR screening and had a clinical culture (blood, bone, tissue, deep podiatric wound, joint aspirate, or synovial fluid) obtained within 3 days of the MRSA nasal PCR. Data on age, sex, diabetes mellitus and dialysis were collected. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for all cultures, and blood and bone/soft tissue cultures separately were estimated.
Results. A total of 1989 patients were included in the study. Of these patients, 1953 patients had a blood culture obtained and 171 patients had a bone/soft tissue culture obtained. The median age was 66 years, and 1086 (54.6%) patients were male. At baseline, 33.1% and 3.8% of patients had diabetes or were on dialysis, respectively. The overall prevalence of MRSA colonization was 12.3%. The sensitivities of the MRSA nasal PCR screening were 67.5% for all clinical cultures, 81.8% for blood cultures, and 55% for bone/soft tissue cultures. Specificities were 88.8%, 88.5%, and 92.7% for all cultures, blood cultures, and bone/soft tissue cultures, respectively. The PPVs were 11%, 7.5%, and 50% for all cultures, blood cultures, and bone/soft tissue cultures, respectively, and the NPVs were 99.3%, 99.8%, and 92.7%, respectively.