Methicillin-resistant Staphylococcus Aureus Nares Research Articles

Persistent methicillin-resistant Staphylococcus aureus (MRSA) nares test positivity during initial days of systemic antistaphylococcal antimicrobial therapy

The typical duration of positive nucleic acid tests for methicillin-resistant Staphylococcus aureus (MRSA) in the nares of patients receiving systemic anti-MRSA antimicrobials is unknown. In this study, hospitalized adult patients with an initial positive MRSA nares nucleic acid test prescribed systemic anti-MRSA antimicrobials had follow-up testing done 48 to 96hours later. A positive follow-up test was detected in 100/113 (88.5%), indicating that MRSA nares DNA tests still have utility for screening after patients have initiated anti-MRSA therapy.

Assessing the Predictive Value of Methicillin-Resistant Staphylococcus aureus Nares Colonization Among Transplant Recipients and Patients With Neutropenia.

Methicillin-resistant Staphylococcus aureus (MRSA) nares screening has been shown to be a powerful antibiotic stewardship tool for MRSA infections within 7 days of screening across a variety of anatomical locations given the high negative predictive value (NPV). However, the utility outside of 7 days and among transplant recipients and patients with neutropenia is less clear. This was a retrospective cohort study across Veterans Affairs medical centers in the United States from 1 January 2007 to 1 January 2023 of patients tested for MRSA colonization and who had a subsequent positive bacterial culture within 28 days of MRSA sc---reening. Sensitivity, specificity, positive predictive value, and NPV were calculated across different time points and anatomical culture locations. The cohort consisted of 686 174 patients, 6 277 437 MRSA nares tests, and 2 446 766 positive bacterial cultures within 28 days of MRSA testing. The NPV of MRSA nares screening for ruling out a MRSA infection within 28 days was 95.8% across all anatomical culture sites. The NPV was 97.9% among patients with neutropenia and 97.5% in solid organ and hemopoietic stem cell transplant recipients. MRSA nares screening can reliably be used for de-escalation of anti-MRSA therapy within 28 days of bacterial culture for all patients, including solid organ and hematopoietic transplant recipients and patients with neutropenia.

Evaluation of Gram Stain-Guided Antibiotic Therapy for Methicillin-Resistant Staphylococcus aureus Pneumonia in Intensive Care Unit Patients.

Background: Despite high negative predictive values (NPVs) seen with methicillin-resistant Staphylococcus aureus (MRSA) nares polymerase chain reaction (PCR) assays, utilization of both respiratory sample Gram stain and MRSA nares PCR in patients with pneumonia may contribute to overuse of laboratory resources. The purpose of this study was to evaluate if a Gram stain demonstrating no Gram-positive organisms from a respiratory sample is sufficient to allow for de-escalation of vancomycin therapy. Methods: This single center study retrospectively identified intensive care unit (ICU) patients started on vancomycin for presumed pneumonia at University of Wisconsin (UW) Health in Madison, WI between August 2022 and March 2023. Patients with respiratory sample demonstrating no Gram-positives on Gram stain met inclusion criteria if the sample was ordered within 24 h of vancomycin initiation. The primary outcome was NPV of respiratory sample Gram stain demonstrating no Gram-positive organisms with respect to MRSA detection of the respiratory culture. Secondary outcomes included the NPV of combined MRSA nares PCR plus respiratory sample Gram stain, and difference in time to event in patients that had both a respiratory sample and MRSA nares PCR ordered. Results: A total of 370 patients were screened for study eligibility; of which 99 patients met inclusion criteria. NPV of respiratory sample Gram stain was 99% for MRSA culture. The combined NPV of respiratory sample Gram stain plus MRSA nares PCR was 98.9% for MRSA culture (n = 88). Respiratory sample was ordered 2.3 h faster compared to MRSA nares PCR (4.3 vs 6.6 h, P = .036). Respiratory sample Gram stain resulted 4.5 h faster compared to MRSA nares PCR (10.7 vs 15.2 h, P = .002). Conclusion: Respiratory sample Gram stains demonstrating no Gram-positive organisms may be used to de-escalate vancomycin and deprioritize the use of MRSA nares PCR.

Modeling relaxed policies for discontinuation of methicillin-resistant Staphylococcus aureus contact precautions.

To evaluate the economic costs of reducing the University of Virginia Hospital's present "3-negative" policy, which continues methicillin-resistant Staphylococcus aureus (MRSA) contact precautions until patients receive 3 consecutive negative test results, to either 2 or 1 negative. Cost-effective analysis. The University of Virginia Hospital. The study included data from 41,216 patients from 2015 to 2019. We developed a model for MRSA transmission in the University of Virginia Hospital, accounting for both environmental contamination and interactions between patients and providers, which were derived from electronic health record (EHR) data. The model was fit to MRSA incidence over the study period under the current 3-negative clearance policy. A counterfactual simulation was used to estimate outcomes and costs for 2- and 1-negative policies compared with the current 3-negative policy. Our findings suggest that 2-negative and 1-negative policies would have led to 6 (95% CI, -30 to 44; P < .001) and 17 (95% CI, -23 to 59; -10.1% to 25.8%; P < .001) more MRSA cases, respectively, at the hospital over the study period. Overall, the 1-negative policy has statistically significantly lower costs ($628,452; 95% CI, $513,592-$752,148) annually (P < .001) in US dollars, inflation-adjusted for 2023) than the 2-negative policy ($687,946; 95% CI, $562,522-$812,662) and 3-negative ($702,823; 95% CI, $577,277-$846,605). A single negative MRSA nares PCR test may provide sufficient evidence to discontinue MRSA contact precautions, and it may be the most cost-effective option.

Microbiologic and Clinical Description of Postoperative Central Nervous System Infection After Endoscopic Endonasal Surgery

Consensus guidelines for antibiotic prophylaxis in endoscopic endonasal surgery (EES) have not been developed. The study objective was to define the microbiologic and clinical characteristics of post-EES central nervous system (CNS) infections. This was a single-center retrospective study of patients >18 years of age who underwent EES between January 2010 and July 2021 at a high-volume skull base center. Patients with confirmed CNS infection within 30 days of EES were included. During the study period, the standard prophylaxis regimen was ceftriaxone 2 g every 12 hours for 48 hours. For patients with a documented penicillin allergy, vancomycin plus aztreonam was recommended. In total, 2440 EES procedures were performed on 2005 patients; the CNS infection rate was 1.8% (37/2005). CNS infections were more common among patients with a history of previous EES (6.5%; 20/307) compared with those who did not (1%; 17/1698; P < 0.001). The median time from EES to CNS infection was 12 (6-19) days. Thirty-two percent (12/37) of CNS infections were polymicrobic, which was more common among patients without previous EES (52.9%; 9/17) compared with those with previous EES (15%; 3/20; P= 0.03). Across all cases, Staphylococcus aureus (n= 10) and Pseudomonas aeruginosa (n= 8) were commonly isolated pathogens. Among those with confirmed methicillin-resistant Staphylococcus aureus (MRSA) nares colonization before EES, 75% (3/4) developed MRSA CNS infections compared with 6.1% (2/33) of noncolonized patients (P= 0.005). CNS infection after EES is rare and causative pathogens vary. Further studies are needed to identify the impact of MRSA nares screening on antimicrobial prophylaxis before EES.

Antibiotic de-escalation in pneumonia with pharmacist education and ordering of methicillin-resistant Staphylococcus aureus nasal swabs

IntroductionWhen methicillin-resistant Staphylococcus aureus (MRSA) is the causative pathogen in pneumonia, in-hospital mortality rate is approximately 31.2%. However, the occurrence of MRSA pneumonia is uncommon, with a reported incidence of...

1804. Quality Improvement Project to improve empiric antibiotic therapy for skin and soft tissue infections using the nasal MRSA PCR

Abstract Background Large cohort studies from the Veteran’s Administration support the negative predictive value of the methicillin resistant Staphylococcus aureus (MRSA) nasal polymerase chain reaction (PCR) swabs for skin and soft tissue infection (SSTI). We investigated the use of the nasal MRSA PCR swab to reduce the inappropriate empiric use of vancomycin and piperacillin-tazobactam for SSTI at our institution. Methods Between July and August 2021, we educated Hospital Internal Medicine (HIM) and Internal Medicine Residents (IMR) on the basics of SSTI management and the utility of a negative nasal MRSA PCR swab. Data on empiric use of vancomycin and piperacillin-tazobactam for SSTIs were collected 3/1/2021 to 7/1/2021 (pre-intervention) and 8/30/2021 to 12/29/2021 (post-intervention). We excluded patients who didn’t have an SSTI, weren’t managed by IMR or HIM, and whose empiric antibiotics were for another indication. To account for antibiotics started in the emergency department (ED), a patient was regarded as having received appropriate empiric antibiotics if they were de-escalated in the first 24 hours of being admitted to IMR or HIM. Example of education material. These fliers were distributed to resident rooms following a series of noon conferences Results Pre-intervention there were 106 patient encounters. In 56 of these (52.8%), patients were placed on inappropriate empiric antibiotics. Post-intervention, there were 72 patient encounters. In 23of these (31.9%), patients were placed on inappropriate empiric antibiotic for an absolute risk reduction (ARR) of 20.9% with a statistically significant 95% CI (6.522 - 35.249) and a number needed to treat (NNT) of 4.78. Nasal MRSA PCR testing increased from 40.6% to 56.9%. The ARR among the HIM teams was 21.3% and was statistically significant with a 95% CI (4.24 - 38.394). Their proportion of MRSA testing increased from 41.5% to 50%. The IMR teams had an ARR of 14.8%, which was not statistically significant (95% CI, -11.339 to 40.884). Their MRSA nasal PCR testing increased from 37.5% to 72%. Conclusion Education on SSTI treatment coupled with use of the MRSA nares PCR appeared to improve empiric antibiotic choices. Residents stated that the nasal MRSA PCR facilitated empiric antibiotic choice. Positive ARR was seen in whole and sub-group analyses of physician teams. We theorize that the lack of statistical significance in the IMR group was related to a small sample size. Disclosures All Authors: No reported disclosures.

2177. Institutional Prevalence of Drug-Resistant Pathogens in Community-Acquired Pneumonia

Abstract Background Community-acquired pneumonia (CAP) is a leading cause of hospitalizations and plays a major role in mortality. The previous Infectious Diseases Society of America (IDSA) definition of healthcare-associated pneumonia (HCAP) was found to be neither sensitive nor specific for identifying drug-resistant pathogens including methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PsA) as a cause of CAP, and use is no longer supported by current guidelines. The 2019 IDSA guidelines for CAP management emphasizes the need for clinician understanding of local epidemiology data to guide selection of appropriate treatment. The primary objective of this study was to determine the prevalence of MRSA and PsA CAP at our institution. Methods This was a retrospective observational study of patients admitted to our 870-bed public hospital with a CAP or HCAP diagnosis within 48 hours of admission between March 2016 and March 2021. The primary outcome of prevalence of CAP caused by MRSA or PsA was determined by comparing the number of blood and adequate sputum cultures with MRSA or PsA to total reviewed cases. Secondary outcomes included the percentage of initial antibiotic regimens involving a broad-spectrum agent, percentage of initial broad-spectrum regimens de-escalated within 72 hours if indicated, and duration of CAP antibiotic treatment. Results A total of 220 patients were included. MRSA or PsA was isolated in 1.36% of adequate sputum cultures collected (n=3/35) and in no collected blood cultures (n=0/208). The local prevalence of CAP caused by MRSA or PsA among the analyzed sample was 1.36% (n=3/220) (Table 1). MRSA nares screening tests were completed in 10% of cases, 4.5% of which were positive (n=1/22). Secondary end point results are presented in Table 2.Table 1.Prevalence of MRSA and PsA in CAP Based on Culture DataTable 2.Secondary Outcome Data Conclusion The overall prevalence of CAP caused by MRSA or PsA among admitted patients is low at Parkland Hospital. Further research is needed to identify local risk factors associated with CAP caused by drug-resistant pathogens. Disclosures All Authors: No reported disclosures.

1287: METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS NARES SCREEN LEADS TO VANCOMYCIN DE-ESCALATION IN TRAUMA

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) nares swab is a proven screening tool to de-escalate vancomycin therapy due to its high negative predictive value in pneumonia and other infections. However, data are lacking on the utility of this test in the critically ill trauma population, which is at high risk for hospital-acquired infections. This study evaluated the impact of empiric MRSA PCR nares screening on de-escalation of vancomycin therapy in critically ill trauma patients. Methods: This is a single center, pre-post observational cohort study conducted at an academic, level I trauma center. Adult patients who were admitted for trauma and received empiric vancomycin therapy for suspected infection in the trauma intensive care unit were included. Patients were grouped by whether they were included 6 months before (pre-cohort) and 6 months after (post-cohort) the implementation of empiric rapid MRSA PCR nares screening in September 2021. The primary outcome was duration of vancomycin therapy. Secondary outcomes included rate of acute kidney injury (AKI), positive MRSA screen or cultures, ICU length of stay (LOS), hospital LOS, and mortality. Results: One-hundred fifty-eight patients were included: 82 in the pre-cohort group and 76 in the post-cohort group. Ninety vancomycin initiation orders were observed in the pre-cohort versus 80 orders in the post-cohort. Baseline demographics were similar between groups. There was a significantly higher rate of MRSA PCR orders in the post-cohort group (75%) compared to (21%) in the pre-cohort (p< 0.001). The pre-cohort group had higher rates of positive MRSA screens (26 vs. 13%, p=0.18) and MRSA positive cultures (17 vs. 9%, p=0.22) compared to post-cohort. There were no reported instances of positive MRSA cultures with a negative PCR. Vancomycin duration was significantly shorter in the post-cohort group (2.55 days vs. 3.5, p=0.02). Hospital and ICU LOS, rates of AKI, and mortality were not different between groups. Conclusions: Implementation of empiric rapid MRSA nares screening led to a shorter overall duration of vancomycin therapy by nearly one day in critically ill trauma patients. Further study is required to evaluate the potential cost savings of empiric MRSA screening in critically ill trauma patients.

Impact of Nares Swabs in the Operative Management of Distal Lower Extremity Infections

Associations between nares surveillance cultures and lower extremity wound cultures remains a topic of discussion in the literature and in clinical practice. Reports are limited due to the questionable accuracy of bedside foot cultures. A retrospective review of our institution's lower extremity wounds requiring surgical management distal to the tibial tuberosity was conducted. Deep intraoperative tissue cultures collected in a sterile operating field were referenced against nares cultures from the same hospitalization. Accuracy, sensitivity, and specificity of nares cultures for predicting methicillin-resistant Staphylococcus aureus (MRSA) infection were determined. Four hundred and forty unique patients with both nares and wound cultures met inclusion criteria. Comorbid diagnoses revealed 66.82%, 30.68%, and 32.27% of patients had diabetes mellitus, chronic kidney disease, and/or peripheral arterial disease, respectively. Sensitivity and specificity were found to be 53.13% and 96.13%, respectively. Prevalence of MRSA in a lower extremity wound was 14.9%, and accuracy of nares culture was 90.04% (CI: 86.91%-92.65%). A review of 30 false negative cases was conducted. Using exclusion criteria of a hospital admission within 60 days of presentation, history of MRSA infection, and/or presentation from a long-term care facility, negative predictive value of MRSA nares colonization was 99.51%. A case of necrotizing fasciitis accounted for one outlier. This data demonstrates that nares surveillance swabs have excellent diagnostic performance in ruling out MRSA infections in foot and ankle wounds. Further analysis is required to determine whether this performance is improved in specialized subgroups or dependent on temporal proximity.

1138. Utility of Methicillin-resistant Staphylococcus aureus Nares Screening in Hospitalized Children With Acute Infectious Disease Syndromes

BackgroundEmpirical antibiotic regimens frequently include treatment for methicillin-resistant Staphylococcus aureus (MRSA). Studies in adults with pneumonia support the use of a negative MRSA nares screening (MNS) to help de-escalate antibiotic therapy. Comparable pediatric data in the literature is scarce. We aimed to evaluate the use of MNS for antibiotic de-escalation in hospitalized children (< 18 years) at a tertiary children’s hospital. MethodsA retrospective chart review was conducted of pediatric inpatients (January 01, 2015 to December 31, 2020) with a presumed infectious diagnosis who had a PCR-based MNS test and a clinical culture (i.e. site of infection or blood) performed as part of their diagnostic work up. Those who were screened >5 days since admission or > 48 hours since start of MRSA-active antimicrobials, and those who had antibiotic treatment withdrawn after 48 hours because of negative cultures were excluded. ResultsA total of 101 children were included with a median age (range) of 2 years (0-17) and about half (n=57, 56.4%) were male. Top three diagnosis groups were skin and soft tissue infections (n=33, 32.7%), toxin-mediated syndromes (n=21, 20.8%), and osteoarticular infections (n=13, 12.9%). Pneumonia accounted for only six (5.9%) patients. The prevalence of nasal MRSA colonization was 6.9% (n=7). The sensitivity of the MNS test to predict a MRSA infection was 42.9% with a specificity of 95.7%. The positive predictive value (PPV) and negative predictive values (NPV) were 42.9% and 95.7%, respectively. In about half (55/95, 57.9%) of patients initiated on anti-MRSA therapy, these agents were discontinued during the admission. A quarter (n=14, 25.5%) were de-escalated based on the negative MNS test alone, and another third (n=21, 38.2%) after negative MNS test and negative culture results became available. ConclusionPediatric providers at this institution have started to use the MNS to help limit anti-MRSA therapy. We noted a high NPV which suggests that MNS may be useful for timely de-escalation of anti-MRSA therapy and thereby a useful antimicrobial stewardship tool for hospitalized children. Prospective studies to evaluate the utility of MNS for the various infectious syndromes are warranted.Disclosures All Authors: No reported disclosures

110. MRSA nasal swab as a stewardship tool to guide IV Vancomycin in diabetic foot infections

BackgroundThe Infectious Disease Society of America (IDSA) guidelines suggest empiric Methicillin-Resistant Staphylococcus Aureus (MRSA) coverage for Diabetic Foot Infection (DFI) with a history of MRSA infection, if local prevalence is high, or if the infection is severe. However, data suggests that there is overutilization of vancomycin in this population and this medication is associated with toxicity. MRSA nasal screen has a high negative predictive value (NPV) for ruling out MRSA in pneumonia and other sites. We performed a medication utilization evaluation (MUE) for Vancomycin IV in DFI patients who had an MRSA nares screen to determine our own NPV of this test and feasibility to use it as an antibiotic stewardship program (ASP) tool to guide vancomycin use in this population.MethodsWe retrospectively reviewed 224 patients from January 2015 to January 2020 who had a diagnosis of DFI and an MRSA nasal screen. 139 patients had cultures done. For the NPV, we excluded patients who had any MRSA positive culture or screen up to a year from admission (Figure 1).Figure 1. Flowchart from our medication utilization evaluation showing patient’s distribution by MRSA-screen result ResultsWe found 148 (66%) patients with DFI who had received IV vancomycin empirically during the admission and 196 of them were MRSA-nares negative (Figure 2). The average days of therapy (DOT) in the MRSA-nares negative patients was 5.2 days vs 4.8 in the MRSA-nares positive patients. Out of the 139 patients with a negative MRSA nasal swab, 124 had no MRSA in cultures, yielding an NPV of 89%. If we considered only the deep cultures, the NPV increased to 90%.Figure 2. Number of patients who received IV vancomycin grouped by MRSA-screen result ConclusionWe identified overutilization of IV vancomycin in patients with a diagnosis of DFI in our institution. Also, our NPV of the MRSA-nasal screening to rule out MRSA infection in DFI was high at 89% similar to previous studies. Based on these findings, we plan to implement a local ASP protocol (Figure 3) using MRSA nasal swab screen to decrease the empiric use of vancomycin. The results of these efforts will be analyzed and published in future iterations with the hopes to share this knowledge to reduce the use of IV vancomycin in this population in other centers.Figure 3. Protocol draft to be used as an ASP tool to guide IV vancomycin de-escalation based on MRSA-nasal screen for DFI patients Disclosures All Authors: No reported disclosures

Pharmacist‐driven methicillin‐resistantStaphylococcus aureus screening protocol and the impact on vancomycin exposure in hospitalized patients with pneumonia

AbstractIntroductionAlthough methicillin‐resistant Staphylococcus aureus (MRSA) is a rarely identified pathogen of pneumonia, providers are often compelled to use anti‐MRSA antibiotics empirically. As a result, patients may be exposed to unnecessary anti‐MRSA antibiotic therapy. Polymerase chain reaction (PCR) nares screening for MRSA colonization has repeatedly shown a negative predictive value of &gt;95% for MRSA pneumonia. Therefore, nares screenings have the potential to serve as a valuable tool to de‐escalate anti‐MRSA antibiotics for patients with pneumonia. Our institution implemented a protocol whereby pharmacists order a MRSA PCR screen for patients with suspected MRSA pneumonia at the time of vancomycin initiation. For negative MRSA PCR results, pharmacists contact the provider and recommend discontinuation of vancomycin.ObjectivesThe primary objective of this study was to evaluate the impact of pharmacist‐driven MRSA PCR nares screening on duration of vancomycin therapy for patients with pneumonia.MethodsThis study was a retrospective cohort study of patients with suspected MRSA pneumonia pre‐ and post‐protocol implementation. The study was conducted at a community teaching hospital September 1, 2017 through November 30, 2017 (control) and September 1, 2018 through November 30, 2018 (intervention). Patients were excluded for the following: concomitant non‐pulmonary MRSA infection, septic shock requiring vasopressors, confirmed MRSA infection within the last 30 days, cystic fibrosis, or bronchiectasis. The primary endpoint was duration of vancomycin therapy.ResultsOur institutional review board‐approved study included 196 patients (n = 81 pre‐protocol, n = 115 post‐protocol). Post implementation of the MRSA nares screen protocol, patients received a significant reduction in median hours of vancomycin (38 vs 23.5 hours, P = .002). Reduction in vancomycin exposure was not found to adversely affect clinical outcomes such as length of stay or readmission at 30 days.ConclusionsImplementation of a pharmacist‐driven MRSA nares screen significantly and safely reduces unnecessary vancomycin exposure in patients with suspected pneumonia.

Impact of Prior-to-Admission Methicillin-Resistant Staphylococcus aureus Nares Screening in Critically Ill Adults With Pneumonia

The high negative predictive value (NPV) of a negative nasal methicillin-resistant Staphylococcus aureus (MRSA) result in suspected MRSA pneumonia is well established; however, data are limited on the NPV of samples collected prior to hospital admission for critically ill patients. To evaluate the predictive characteristics of MRSA nares screening performed prior to hospital admission in critically ill adult patients diagnosed with pneumonia. A retrospective analysis was conducted in critically ill patients with pneumonia and MRSA nares screening within 60 days of respiratory culture. The primary outcome was NPV of MRSA nares for MRSA pneumonia using samples within 60 days compared to in-hospital respiratory cultures. A sensitivity analysis was performed for samples within 30 days. Secondary outcomes were prevalence, positive predictive value (PPV), sensitivity, specificity, and MRSA pneumonia risk factors. The NPV for MRSA nares screening collected prior to hospital admission was high at 98% (95% CI = 96%-99%) for samples collected within 60 days (n = 243) and 99% (95% CI: 94%-99.9%) for samples within 30 days (n = 119). Specificity for MRSA nares collected 60 days prior to admission (96%, 95% CI: 93-98) and 30 days (96%, 95% CI: 91%-99%) were both high. PPV and sensitivity were lower. Risk factors for MRSA pneumonia were similar. MRSA nares screening within 60 days of intensive care unit admission has a high NPV and specificity for MRSA pneumonia in critically ill patients and may be a powerful stewardship tool for avoidance of empirical anti-MRSA therapy.

Emergency department methicillin-resistant Staphylococcus aureus nare screen effect on pneumonia treatment duration.

The objective of this study was to determine if performing a methicillin-resistant Staphylococcus aureus (MRSA) nasal screen in the emergency department (ED) decreased general medicine patient exposure to anti-MRSA antibiotics for pneumonia. This was a single-center, retrospective study evaluating patients who had a diagnosis of pneumonia and were initiated on anti-MRSA therapy (vancomycin or linezolid) in the ED and subsequently admitted to a general medicine floor. Patients were divided into two groups: 1) did not receive a MRSA nares screen in the ED (No MRSA screen group) or 2) received a MRSA nares screen in the ED (MRSA screen group). The primary outcome was anti-MRSA antibiotic duration. Secondary outcomes included vancomycin level evaluation, hospital survival, and acute kidney injury. Of the 116 patients included, 37 patients received a MRSA nares screen in the ED and 79 patients did not. Median duration of antibiotic exposure was similar for both groups (No MRSA screen, 30.5h [interquartile range (IQR) 20.5-52.5] vs. MRSA screen, 24.5h [IQR 20.6-40.3]; p=0.28). Of patients who were screened, 35 were negative and 2 were positive. Secondary outcomes were similar. Performing a MRSA nares screen in the ED for patients diagnosed with pneumonia, initiated on anti-MRSA antibiotics, and admitted to a general medicine floor did not decrease duration of anti-MRSA antibiotics. At this time, ED providers do not need to consider a MRSA nasal screen in the ED for patients being admitted to general medicine, although larger studies could be considered.

87. Utilization of Methicillin-Sensitive/Resistant Staphylococcus aureus Nares Screen to Decrease Vancomycin and Linezolid Use in Hospitalized Patients with Respiratory Infections

BackgroundPharmacist-driven protocols for utilization of methicillin-resistant Staphylococcus aureus (MRSA) nares screenings have shown to decrease duration of empiric gram-positive therapy and rates of acute kidney injury (AKI) in patients with respiratory infections. This study evaluated the impact of a pharmacist-driven MRSA nares screening protocol on duration of vancomycin or linezolid therapy (DT) in respiratory infections.MethodsPatients aged 18 years and older with a medication order of vancomycin or linezolid for respiratory indication(s) were included. The MRSA nares screening protocol went into effect in October 2019. The protocol allowed pharmacists to order an MRSA nares polymerase chain reaction (PCR) for included patients, while the Antimicrobial Stewardship Program (ASP) made therapeutic recommendations for de-escalation of empiric gram-positive coverage based on negative MRSA nares screenings, if clinically appropriate. Data for the pre-intervention group was collected retrospectively for the months of October 2018 to March 2019. The post-intervention group data was collected prospectively for the months of October 2019 to March 2020.ResultsNinety-seven patients were evaluated within both the pre-intervention group (n = 50) and post-intervention group (n = 57). Outcomes for DT (38.2 hours vs. 30.9 hours, P = 0.601) and AKI (20% vs. 14%, P = 0.4105) were not different before and after protocol implementation. A subgroup analysis revealed a significant reduction in DT within the pre- and post-MRSA PCR groups (38.2 hours vs. 24.8 hours, P = 0.0065) when pharmacist recommendations for de-escalation were accepted.ConclusionA pharmacist-driven MRSA nares screening protocol did not affect the duration of gram-positive therapy for respiratory indications. However, there was a reduction in DT when pharmacist-driven recommendations were accepted.Disclosures All Authors: No reported disclosures

Correlation Between Patients With Methicillin-Resistant Staphylococcus aureus (MRSA) Nares Colonization and MRSA Diabetic Foot Infections.

Infectious Diseases Society of America diabetic foot infection (DFI) guidelines indicate empiric methicillin-resistant Staphylococcus aureus (MRSA) coverage for patients with a history of MRSA infection, when local prevalence of MRSA is high, or infection is clinically severe. These recommendations may lead to overutilization of empiric MRSA coverage, which can result in serious consequences. A strong negative predictive value (NPV) has been reported in literature for pneumonia, and recently, for all anatomical sites of infection. While these findings are promising, further validation is needed before clinicians may confidently use MRSA nares to guide empiric therapy for DFIs. A retrospective electronic medical record review was completed between October 1, 2013 and October 1, 2019. Patients met inclusion criteria if they were at least 18, admitted with a DFI, had MRSA nares test results, and DFI cultures. Patients were excluded if pregnant or MRSA infection within 1 year prior to index admission for DFI. A total of 200 patients met inclusion criteria. The majority of study participants were male with a mean age of 63. NPV of MRSA nares for MRSA DFIs was determined to be 94% and positive predictive value 58%. Sensitivity and specificity were 56% and 94%, respectively. Results of this study are consistent with prior literature supporting strong correlation of NPV for MRSA nares. The DFIs evaluated suggest a strong NPV of MRSA nares for MRSA DFIs, which may allow for faster de-escalation of empiric anti-MRSA antibiotic therapy and lower risk of adverse events associated with anti-MRSA therapy.

Timing and Route of Contamination of Patient Rooms With Healthcare-Associated Pathogens

Background: Transmission of healthcare-associated pathogens such as Clostridioides difficile and methicillin-resistant Staphylococcus aureus (MRSA) is a persistent problem in healthcare facilities despite current control measures. A better understanding of the routes of pathogen transmission is needed to develop effective control measures. Methods: We conducted an observational cohort study in an acute-care hospital to identify the timing and route of transfer of pathogens to rooms of newly admitted patients with negative MRSA nares results and no known carriage of other healthcare-associated pathogens. Rooms were thoroughly cleaned and disinfected prior to patient admission. Interactions of patients with personnel and portable equipment were observed, and serial cultures for pathogens were collected from the skin of patients and from surfaces, including those observed to come in contact with personnel and equipment. For MRSA, spa typing was used to determine relatedness of patient and environmental isolates. Results: For the 17 patients enrolled, 1 or more environmental cultures became positive for MRSA in rooms of 10 patients (59%), for C. difficile in rooms of 2 patients (12%) and for vancomycin-resistant enterococci (VRE) in rooms of 2 patients (12%). The patients interacted with an average of 2.4 personnel and 0.6 portable devices per hour of observation. As shown in Figure 1, MRSA contamination of the floor occurred rapidly as personnel entered the room. In a subset of patients, MRSA was subsequently recovered from patients’ socks and bedding and ultimately from the high-touch surfaces in the room (tray table, call button, bedrail). For several patients, MRSA isolates recovered from the floor had the same spa type as isolates subsequently recovered from other sites (eg, socks, bedding, and/or high touch surfaces). The direct transfer of healthcare-associated pathogens from personnel or equipment to high-touch surfaces was not detected. Conclusions: Healthcare-associated pathogens rapidly accumulate on the floor of patient rooms and can be transferred to the socks and bedding of patients and to high-touch surfaces. Healthcare facility floors may be an underappreciated source of pathogen dissemination not addressed by current infection control measures.Funding: NoneDisclosures: None

Utility of Methicillin-Resistant Staphylococcus aureus Nares Screening for Patients with a Diabetic Foot Infection.

Treatment of suspected methicillin-resistant Staphylococcus aureus (MRSA) is a cornerstone of severe diabetic foot infections; however, antibiotics can be associated with toxicity. The objective of this study was to determine the negative predictive value (NPV) of MRSA nares screening in the determination of subsequent MRSA in patients with a diabetic foot infection. This was a retrospective cohort study across Veterans Affairs (VA) medical centers from 1 January 2007 to 1 January 2018. Data from patients with an International Classification of Diseases (ICD) code for a diabetic foot infection with MRSA nares screening, and subsequent cultures were evaluated for the presence of MRSA. NPVs were calculated for the entire cohort, as well as for a subgroup representing deep cultures. Additionally, the distribution of all pathogens isolated from diabetic foot infections was determined. A total of 8,163 episodes were included in the analysis for NPV. The NPV of MRSA nares screening for MRSA diabetic foot infection was 89.6%. For the deep cultures, the NPV was 89.2%. The NPV for cultures originating from the foot was 89.7%, and the NPV for those originating from the toe was 89.4%. There were 17,822 pathogens isolated from the diabetic foot cultures. MRSA was isolated in 7.5% of cultures, and methicillin-susceptible S. aureus was isolated in 24.8%. Enterococcus was identified in 14.7% of cultures, Proteus in 7.3%, and Pseudomonas in 6.8% of cultures. Given the high NPVs, the use of MRSA nares screening may be appropriate as a stewardship tool for deescalation and avoidance of empirical anti-MRSA therapy in patients who are not nasal carries of MRSA.

571. Determining the Utility of Methicillin-Resistant Staphylococcus aureus Nares Screening in Antimicrobial Stewardship

BackgroundTreatment of suspected Methicillin-resistant Staphylococcus aureus (MRSA) is a cornerstone of many antibiotic regimens; however, some anti-MRSA antibiotics are associated with toxicity. The Veterans Affairs (VA) screens each patient on admission for MRSA nares colonization. The objective of this study was to determine whether MRSA nares screening can be used as a stewardship tool for de-escalation as well as avoidance of anti-MRSA therapy.MethodsThis was a retrospective cohort study across VA medical centers nationwide from January 1, 2007 to January 1, 2018. Data from patients with MRSA nares screening were obtained from the Corporate Data Warehouse. Subsequent clinical cultures within 7 days of the nares swab were evaluated for the presence of MRSA. Sensitivity, specificity, positive predictive values (PPVs), and negative predictive values (NPVs) were calculated for the entire cohort, as well as subgroups for specific culture sites. Cultures were considered to be from a sterile site if they were from a fluid/aspirate, bone, tissue, or blood taken from the periphery. NPVs and PPVs were calculated for each of these sterile sites.ResultsA total of 447,579 clinical cultures were included in the final analysis. The NPV of MRSA nares screening for ruling out MRSA was 95.7% for all cultures submitted. The sensitivity and specificity for positive clinical cultures were 67.4% and 83%, respectively. The NPV for bloodstream infections (n = 64,128) was 96.2% for intra-abdominal cultures (n = 8,071) was 97.9%, for respiratory cultures (n = 75,242) was 95.3%, for wound cultures (n = 95,832) was 90.4%, and for renal cultures (n = 164,330) was 99.1%. NPVs for sterile sites are as follows: intra-abdominal (n = 7,426) was 98.1%, respiratory (n = 15,583) was 95.2%, wound (n = 51,793) was 91%.ConclusionMRSA nares screening has a high NPV and specificity for ruling out potential MRSA infections at a variety of culture sites including bloodstream, intra-abdominal, respiratory, renal, and wounds. MRSA nares screening is a powerful stewardship tool for de-escalation and avoidance of empirical anti-MRSA therapy. Disclosures All authors: No reported disclosures.