Methicillin-resistant Staphylococcus Aureus Polymerase Chain Reaction Research Articles

Evaluating the Diagnostic Performance of Nasal Methicillin-Resistant Staphylococcus aureus Polymerase Chain Reaction in Hospital-Acquired Pneumonia Within the Intensive Care Unit. A Retrospective Study.

Background: The methicillin-resistant Staphylococcus aureus (MRSA) accounts for 20% to 40% of all hospital-acquired pneumonia (HAP) cases with mortality rates up to 55%. Prompt and accurate diagnosis is essential, especially in intensive care unit (ICU) patients. Nasal MRSA polymerase chain reaction (PCR) diagnostic utility evidence is conflicting in the literature for HAP due to a low number of HAP patients included in prior studies or due to the lack of high-yield gold standard cultures defined for comparisons. Methods: This was a retrospective cohort study conducted in a 65-bed medical ICU, and encompassing all adult patients admitted from January 2015 to March 2023 for HAP. Respiratory cultures included were those obtained by bronchoalveolar lavage or endotracheal suction within 7 days of nasal MRSA PCR testing. Results: The study included 412 patients; 56.8% were males and 65% were Whites. The mean age was 60.5 years. Most patients (82.5%) underwent MRSA-PCR before intubation, and the average time between MRSA-PCR and lower respiratory cultures was 2.15 days. The diagnostic performance of nasal MRSA PCR in diagnosing HAP in the ICU yielded a sensitivity (Sen) of 47.83%, specificity (Sp) of 92.29%, positive predictive value (PPV) of 26.83%, and negative predictive value (NPV) of 96.77%. For nonventilator HAP (nv-HAP) cases sensitivity was at 50%, specificity 92.83%, PPV 28.57%, and NPV at 97.00%. In ventilator-acquired pneumonia (VAP-HAP), the corresponding values were 42.86%, 90.91%, 23.08%, and 96.15%, respectively. Conclusion: The nasal MRSA PCR shows a high NPV and low false negative rate, suggesting it is a reliable tool for ruling out MRSA HAP in ICU patients. Care should be taken into account for disease prevalence and clinical context, as these factors may influence test performance. Further validation through prospective large-sample studies utilizing high-yield lower respiratory tract cultures is necessary to confirm our findings.

Swab Testing to Optimize Pneumonia treatment with empiric Vancomycin (STOP-Vanc): study protocol for a randomized controlled trial.

Background: Vancomycin, an antibiotic with activity against Methicillin-resistant Staphylococcus aureus (MRSA), is frequently included in empiric treatment for community-acquired pneumonia (CAP) despite the fact that MRSA is rarely implicated in CAP. Conducting polymerase chain reaction (PCR) testing on nasal swabs to identify the presence of MRSA colonization has been proposed as an antimicrobial stewardship intervention to reduce the use of vancomycin. Observational studies have shown reductions in vancomycin use after implementation of MRSA colonization testing, and this approach has been adopted by CAP guidelines. However, the ability of this intervention to safely reduce vancomycin use has yet to be tested in a randomized controlled trial. Methods: STOP-Vanc is a pragmatic, prospective, single center, non-blinded randomized trial. Adult patients with suspicion for CAP who are receiving vancomycin and admitted to the Medical Intensive Care Unit at Vanderbilt University Medical Center will be screened for eligibility. Eligible patients will be enrolled and randomized in a 1:1 ratio to either receive MRSA nasal swab PCR testing in addition to usual care (intervention group), or usual care alone (control group). PCR testing results will be transmitted through the electronic health record to the treating clinicians. Primary providers of intervention group patients with negative swab results will also receive a page providing clinical guidance recommending discontinuation of vancomycin. The primary outcome will be vancomycin-free hours alive, defined as the number of hours alive and free of the use of vancomycin within the first seven days following trial enrollment estimated using a proportional odds ratio model. Secondary outcomes include 30-day all-cause mortality and time alive off vancomycin. Discussion: STOP-Vanc will provide the first randomized controlled trial data regarding the use of MRSA nasal swab PCR testing to guide antibiotic de-escalation. This study will provide important information regarding the effect of MRSA PCR testing and antimicrobial stewardship guidance on clinical outcomes in an intensive care unit setting. Trial registration: This trial was registered on ClinicalTrials.gov on February 22, 2024. (ClinicalTrials.gov identifier: NCT06272994).

Evaluation of computerized clinical decision support system to reduce unnecessary nasal methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) testing.

Our health system implemented a novel clinical decision-support system to reduce unnecessary duplicate nasal methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) orders. In an 8-month period, the rate of duplicate MRSA PCR orders within 7 days declined from 4.7% (370 of 7,861) to 1.2% (120 of 9,833).

MRSA PCR improves sensitivity of detection of colonization in neonates

Background: Neonates colonized with methicillin-resistant Staphylococcus aureus (MRSA) are at high risk of developing life-threatening MRSA infection. Due to lack of evidence, national guidelines do not currently recommend a specific methodology for detecting MRSA colonization. We hypothesize that surveillance for MRSA colonization via polymerase chain reaction (PCR) is superior to culture for the detection of colonization. Methods: In this retrospective study, we compared results of MRSA surveillance by 2 methodologies, culture and PCR, after implementation of an MRSA surveillance and decolonization protocol in the Texas Children’s Hospital Pavilion for Women, a 42-bed neonatal intensive care unit. MRSA colonization of 3 body sites via the 2 methodologies was assessed from June 2017 through December 2020. All neonates were screened for MRSA upon admission to the NICU and weekly thereafter until MRSA-positive or discharged. Swab specimens were initially tested by PCR (Xpert MRSA NxG, Cepheid) and when MRSA-positive reflexed to culture to recover the organism for further characterization. This study was approved through the Baylor College of Medicine Institutional Review Board. Results: During the study period, 2,351 neonates were assessed for MRSA colonization by PCR; 81 (3.4%) infants were PCR positive (Fig. 1). Of those 81, 57 (70.4%) had concordant MRSA PCR and culture results, and 24 (29.6%) were MRSA PCR positive but no isolate was recovered in culture. Also, 8 specimens were indeterminate by PCR. However, 1 infant who was negative by culture but was PCR positive developed an MRSA orbital infection. Compared to PCR, the overall sensitivity of MRSA culture was 70.4% (range, 57.7%–80.8%, depending on the year) (Table 1). Conclusions: PCR is more sensitive than culture for detecting MRSA colonization in neonates. Utilizing a PCR method enhances the ability to identify MRSA colonized infants more readily and allows for prompt initiation of infection control interventions including isolation precautions and decolonization strategies. Reflex to culture remains important for strain characterization during outbreak investigations and for additional susceptibility testing. Resource utilization and cost–benefit analyses should be done in future studies to influence changes in national guidelines for the control of Staphylococcus aureus colonization and infection in neonatal intensive care units.Disclosures: None

Evaluation of Anti-Methicillin-Resistant Staphylococcus aureus (MRSA) Prescribing Habits in Patients with a Positive MRSA Nasal Swab in the Absence of Positive Cultures.

Methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) nasal swabs are guideline-recommended de-escalation tools in certain patients with pneumonia. Prior studies have demonstrated reduced anti-MRSA therapy with negative results, but the impact on durations of therapy has been poorly elucidated in patients with positive PCRs. The objective of this review was to evaluate anti-MRSA treatment durations in patients with a positive MRSA PCR in the absence of MRSA growth on culture. This was a single-center, retrospective observational study evaluating 52 hospitalized, adult patients receiving anti-MRSA therapy with positive MRSA PCRs. The overall median duration of anti-MRSA therapy was five days, including a median of four days after PCR results. This was consistent among intensive care unit (ICU) and non-ICU patient populations and in patients with suspected community-acquired pneumonia (CAP). Among patients with hospital-acquired pneumonia (HAP), the median duration of anti-MRSA therapy was seven days, with a median of six days after PCR results. Overall, patients received a median duration of anti-MRSA therapy that would constitute a full treatment course for many respiratory infections, which indicates that providers may equate a positive MRSA nasal PCR with positive culture growth and highlights the need for education on the interpretation of positive tests.

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.

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.

Evaluating Methicillin-Resistant Staphylococcus aureus Polymerase Chain Reaction Nasal Screening as a Tool for Antimicrobial Stewardship

IntroductionInitiation of broad-spectrum empiric antibiotics is common when infection is suspected in hospitalized adults. The benefits of early utilization of effective antibiotics are well documented. However, the negative effects of inappropriate antibiotic use have led to antimicrobial stewardship mandates. Recent data demonstrate the utility of methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) nasal screening to steward anti-MRSA empiric antibiotics in pneumonia. We hypothesize that MRSA PCR nasal swabs would also be effective to rule out other MRSA infection to effectively limit unnecessary antibiotics for any infectious source. MethodsWe performed a single-center retrospective chart review of all adult patient encounters from October 2019-July 2021 with MRSA PCR nasal testing. We then reviewed all charts to evaluate for the presence of infections based on source cultures results, as the gold standard. Sensitivity, specificity, negative predictive value, and positive predictive value were calculated from 2 × 2 contingency tables. ResultsAmong all patients with MRSA nasal screening, 1189 patients had any infection. Prevalence of MRSA nasal carriage among patients screened was 12%. Prevalence of MRSA infection among all infections was 7.5%. MRSA nasal swabs demonstrated a negative predictive value of 100% for MRSA urinary tract infection, 97.9% for MRSA bacteremia, 97.8% for MRSA pneumonia, 92.1% for MRSA wound infection, and 96.6% for other MRSA infections. Overall, MRSA PCR nasal swabs had a sensitivity of 68.5%, specificity of 90.1%, positive predictive value of 23.7%, and negative predictive value of 98.5% for any infections. ConclusionsMRSA PCR nasal swabs have a high negative predictive value for all infections. Our data support the use of MRSA PCR nasal swabs to rule out MRSA infection and thereby allow early de-escalation of MRSA coverage in hospitalized patients requiring empiric antibiotics. Implementation of MRSA screening could decrease antibiotic-associated morbidity, resistance, and costs. More studies should be conducted to validate these results and support these findings.

Correlation of MRSA polymerase chain reaction (PCR) nasal swab in ventilator-associated pneumonia, lung abscess, and empyema

Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogen empirically covered in pulmonary infections. Limited studies evaluate the relationship between the MRSA PCR nasal swab assays and clinically diagnosed ventilator-associated pneumonia (VAP), lung abscess, and empyema. This retrospective, single-center study included 161 patients, which aimed to validate the clinical utility of MRSA PCR nasal swabs in VAP, lung abscess, and empyema through sensitivity, specificity, positive predictive value (PPV), and negative predicative value (NPV) analysis. VAP had a 100% sensitivity, 89% specificity, 67% PPV, and 100% NPV. Lung abscess had a 0% sensitivity, 90% specificity, 0% PPV, 90% NPV.Empyema had a 80% sensitivity, 84% specificity, 42% PPV, and 97% NPV.The study results demonstrate that the MRSA PCR nasal swab assay has the potential to be a vital tool in de-escalating antimicrobial therapy in VAP, lung abscess, and empyema.

Pharmacist-Driven Methicillin-Resistant S. aureus Polymerase Chain Reaction Testing for Pneumonia.

Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) can be detected using nasal swab polymerase chain reaction (PCR) assay and is associated with clinical MRSA infection. The MRSA nasal PCR has a rapid turnaround time and a negative predictive value for MRSA pneumonia of >98%; however, data are limited in critically ill patients. The purpose of this study is to determine the impact of a pharmacist-driven algorithm, utilizing MRSA PCR nasal screening on duration of anti-MRSA therapy in patients admitted to the intensive care unit (ICU) with suspected pneumonia. A single-center pre/post study was conducted in 4 ICUs at a large tertiary care community hospital. Adult patients admitted to the ICU initiated on vancomycin or linezolid for pneumonia managed using a pharmacist-driven MRSA PCR algorithm were included in the algorithm cohort. A historical cohort with standard management was matched 1:1 by age, type of pneumonia, and Acute Physiology and Chronic Health Evaluation II (APACHE II) score. The primary outcome was duration of anti-MRSA therapy. Secondary outcomes included MRSA rates, number of vancomycin levels, new onset of acute kidney injury (AKI), ICU length of stay (LOS), hospital LOS, and mortality. Of the 245 patients screened, 50 patients met inclusion criteria for the algorithm cohort and were matched to 50 patients in the historical cohort. The duration of anti-MRSA therapy was significantly lower compared with the historical cohort (47 vs 95 hours; P < 0.001). Secondary outcomes were similar between groups for MRSA rates, new onset of AKI, LOS, and mortality. There were less vancomycin levels ordered in the algorithm cohort (2 vs 3, P = 0.026). A pharmacist-driven MRSA PCR algorithm significantly reduced anti-MRSA duration of therapy in critically ill patients with pneumonia. Future studies should validate these results in critically ill populations and in settings where MRSA pneumonia is more prevalent.

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.

Evaluation of the timing of MRSA PCR nasal screening: How long can a negative assay be used to rule out MRSA-positive respiratory cultures?

Previous studies indicate that the polymerase chain reaction (PCR) nasal assay for methicillin-resistant Staphylococcus aureus (MRSA) has a consistently high (>95%) negative predictive value (NPV) in ruling out MRSA pneumonia; however, optimal timing of PCR assay specimen and respiratory culture collection is unclear. A study including 736 patients from a community hospital system was conducted. Patients were included if they had undergone MRSA nasal screening with a PCR assay and had documented positive respiratory culture results. In the full cohort, the MRSA PCR nasal screen assay was demonstrated to have an NPV of 94.9% (95% confidence interval [CI], 92.8%-96.5%) in ruling out MRSA-positive respiratory cultures. When evaluating the NPV by level of care (ie, where the MRSA PCR nasal assay sample was collected), no significant difference between values for samples collected in an intensive care unit vs medical/surgical units was identified (NPV [95%CI], 94.9% [92.7%-96.6%] vs 95.3% [88.4%-98.7%]). Additionally, NPV remained high with use of both invasive (NPV [95%CI], 96.8% [92.7%-99.0%]) and noninvasive (NPV [95%CI], 94.5% [91.7%-96.2%]) respiratory sampling methods. Finally, when evaluating the effect of time between MRSA PCR nasal screening and respiratory sample collection, we found high NPVs for all evaluated timeframes: within 24 hours, 93.8% (90.1%-96.4%); within 25 to 48 hours, 98.6% (92.7%-100.0%); within 49 hours to 7 days, 95.7% (91.4%-98.3%); within 8 to 14 days, 92.9% (85.1%-97.3%); and after more than 14 days, 95.5% (84.5%-99.4%). We report high NPVs for up to 2 weeks between specimen collections, which allows clinicians to use a negative MRSA PCR nasal screen assay to rule out MRSA pneumonia, potentially leading to decreased exposure to MRSA-active antibiotics.

79. Outcomes Associated with the Utilization of the Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Polymerase Chain Reaction (PCR) Assay to De-escalate Vancomycin Therapy in Patients with Suspected Pneumonia at a Rural Community Hospital

BackgroundVancomycin is often added to standard inpatient community acquired pneumonia therapy, but the incidence of MRSA pneumonia is relatively low. The MRSA nasal PCR assay is used to detect if a patient’s nares are colonized with MRSA. Studies have found that this test has an excellent negative predictive value at ruling out MRSA pneumonia. In practice, there is reluctance to utilize this data to de-escalate vancomycin, possibly because little data exists investigating clinical outcomes associated with this intervention. The purpose of this study was to evaluate how this assay, in combination with antimicrobial stewardship, impacts de-escalation of vancomycin and consequently, length of stay, days of therapy, readmission, and mortality.MethodsWe performed a cohort study of patients who received vancomycin for pneumonia during the period 2017–2019. In July 2018, we implemented a pharmacy-led process to de-escalate vancomycin in pneumonia patients based on the results of the nasal MRSA PCR. Patient were excluded if they had concomitant skin/skin structure infection, osteomyelitis, were transferred to another facility, signed out against medical advice, or required mechanical ventilation. Data on patient characteristics, disease severity, length of stay, days of therapy, readmission, and mortality were compared between the groups.Figure 1: Patient disposition with reasons for exclusion from study Results101 and 107 patients were included in the before and after group, respectively. The average length of stay was 5.31 (before group) vs 4.33 days (after group), resulting in a 0.98 day decrease (p=0.0095). Days of therapy was 3.16 (before group) vs 1.96 days (after group), resulting in a 1.2 day reduction (p< 0.0001). 30-day mortality was significantly higher in the before group (19.8%) than the after group (9.3%) (RR 0.47, 95% CI 0.23–0.96). 30-day readmission was similar between the two groups (21.8% pre-intervention vs 19.6% post-intervention, p=0.7).Figure 2: Length of Stay and Duration of therapy reductions between the pre- and post-intervention groups. Figure 3: 30-day readmission rate and 30-day mortality rate in the pre- and post-intervention groups. Figure 4: Vancomycin days of therapy per 1000 patient days from July 2017 to May 2020 ConclusionUse of the MRSA nasal PCR to deescalate vancomycin therapy appears to significantly reduce length of stay and days of vancomycin therapy. Use of this assay did not negatively impact readmission but, may have a positive impact on mortality. Further research is needed to determine the impact of this intervention on length of stay and mortality.Disclosures All Authors: No reported disclosures

Pharmacist-Driven MRSA Nasal PCR Screening and the Duration of Empirical Vancomycin Therapy for Suspected MRSA Respiratory Tract Infections.

ObjectiveTo assess the effect of a pharmacist-driven, polymerase chain reaction (PCR)−based nasal screening protocol for methicillin-resistant Staphylococcus aureus (MRSA) on vancomycin therapy duration and on rates of adverse drug events and 30-day hospital readmission.Patients and MethodsFrom July 8, 2017, through January 31, 2019, we performed a retrospective, multicenter, preimplementation-postimplementation study. Patients with a vancomycin order to treat lower respiratory tract infection (LRTI) underwent MRSA PCR screening; tests were ordered by health care providers, including physicians, physician assistants, and advanced practice registered nurses. During the preimplementation period (July 8, 2017, through September 30, 2018), pharmacists could order MRSA PCR screening only after receiving a verbal order from a health care provider. During the postimplementation period (October 1, 2018, through January 31, 2019), a collaborative practice agreement allowed pharmacists to order MRSA PCR screening tests.ResultsThe preimplementation group included 241 patients, and the postimplementation group included 74 patients. Of these patients, 124 in the preimplementation group and 62 in the postimplementation group received MRSA PCR screening. Twenty patients (16.1%) in the preimplementation group and 9 (14.5%) in the postimplementation group had a positive MRSA PCR screening test result (between-group difference, 1.6%; P=.80). Duration of therapy was significantly shorter in the postimplementation group (median [interquartile range], 14.3 [5.0-28.6] hours vs 24.0 [12.4-47.0] hours; P<.001).ConclusionVancomycin therapy carries a risk of adverse events and may increase health care costs. A pharmacist-driven protocol for MRSA nasal swab PCR screening effectively reduces the duration of vancomycin therapy for patients with lower respiratory tract infection.

Impact of a Pharmacist-driven Methicillin-resistant Staphylococcus aureus Polymerase Chain Reaction Nasal Swab Protocol on the De-escalation of Empiric Vancomycin in Patients with Pneumonia in a Rural Healthcare Setting.

IntroductionPneumonia caused by methicillin-resistant Staphylococcus aureus (MRSA) carries a high rate of morbidity and mortality. Many clinicians empirically treat those at risk of developing MRSA pneumonia with vancomycin. Several studies have identified a high negative predictive value of the MRSA polymerase chain reaction (PCR) nasal swab test in lower respiratory tract infections, suggesting it can be used to guide the de-escalation of empiric anti-MRSA therapy.ObjectiveTo evaluate the impact of a pharmacist-driven MRSA PCR nasal swab protocol on the de-escalation of empiric vancomycin in patients with pneumonia in a rural healthcare setting. Secondarily, to assess the rate of hospital length of stay, the rate of vancomycin-associated acute kidney injury, and in-hospital mortality after pharmacist-driven de-escalation of empiric vancomycin in patients with pneumonia. MethodsA retrospective, single-center, pre-post cohort study was conducted in patients after the implementation of a pharmacist-driven protocol allowing pharmacists to obtain nasal swabs and PCR testing for MRSA in those on empiric vancomycin therapy for suspected MRSA pneumonia. Based on negative test results, pharmacists recommended a de-escalation of empiric vancomycin to the physician. Patients were included if they were adults at least 18 years of age, had a physician diagnosis of suspected or confirmed pneumonia, and initiated on at least one dose of intravenous vancomycin within 48 hours of admission.ResultsA total of 79 patients were identified for inclusion in the pre-protocol group (n=32) or post-protocol group (n= 47). The mean duration of vancomycin therapy in the pre-protocol group was 3.1 days as compared to 1.7 days in the post-protocol group for a 1.4 days reduction (p=0.044). There was no significant impact on the number of vancomycin cases de-escalated within 24 hours (p=0.14) but there was a significant reduction at 48 hours (p=0.01). Protocol implementation was associated with a reduction in the average length of hospitalization (8 versus 5.20 days, p=0.006). Neither group had a vancomycin-associated acute kidney injury or in-hospital mortality.ConclusionAmong patients with suspected MRSA pneumonia, a pharmacist-driven MRSA PCR nasal swab protocol resulted in a significant reduction of empiric vancomycin duration of therapy without an adverse impact on clinical outcomes in a rural healthcare setting.

Impact of a pharmacist-driven methicillin-resistant Staphylococcus aureus surveillance protocol.

Results of a study to evaluate the impact of a pharmacist-driven methicillin-resistant Staphylococcus aureus (MRSA) surveillance screening protocol are reported. A retrospective single-center, quasi-experimental, pre-post cohort study was conducted to assess medication-use and clinical outcomes before and after implementation of a protocol allowing pharmacists to order nasal swabs and polymerase chain reaction (PCR) testing for MRSA in selected patients receiving vancomycin for pneumonia or acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Negative assay results were used to guide de-escalation of vancomycin therapy. The primary outcome was vancomycin days of therapy (DOT). Secondary outcomes included hospital length of stay, the rate of vancomycin-associated acute kidney injury, and in-hospital mortality. A total of 300 patients were identified for inclusion in the preprotocol group (n = 150) or postprotocol group (n = 150) through medical records review. Compared with patients in the preprotocol group, those in the postprotocol group had a median 2.1-day reduction in vancomycin DOT (2.1 days versus 4.2 days, p < 0.0001). Protocol implementation was also associated with a decrease in the median number of vancomycin serum levels obtained per patient but did not have a significant impact on other secondary outcomes. Among patients with suspected or confirmed pneumonia or an AECOPD, the expansion of pharmacists' traditional scope of practice to include a surveillance protocol using a MRSA PCR nares assay to guide vancomycin de-escalation resulted in a reduction in vancomycin utilization without compromising clinical outcomes.

Effect of the Methicillin-Resistant Staphylococcus aureus Nasal Polymerase Chain Reaction on Vancomycin Days and Clinical Outcomes in Pneumonia

BackgroundPrevious studies have demonstrated that the methicillin-resistant Staphylococcus aureus(MRSA) nasal polymerase chain reaction (PCR) assay has a high negative predictive value for MRSA pneumonia, and that a negative result may be used to guide antibiotic de-escalation. Despite increasing use in clinical practice, limited data exist regarding the impact of nasal MRSA testing on the duration of MRSA-directed therapy and patient outcomes. This study evaluated the effect of the MRSA nasal PCR result on vancomycin days and clinical outcomes in patients treated for pneumonia with empiric vancomycin therapy.MethodsA retrospective study of adult inpatients with an MRSA nasal PCR assay ordered between January 2015 and September 2015 was conducted. Patients with confirmed or presumed pneumonia and who were treated with empiric vancomycin therapy were included. Outcomes were compared for patients with a negative vs. a positive MRSA nasal PCR result. The primary outcome was the number of days of vancomycin therapy. Secondary outcomes included restart of vancomycin within 7 days, length of hospitalization, 30-day readmission, 30-day mortality, and predictive value of the MRSA PCR assay. Analyses were performed for the overall cohort and a propensity score-matched cohort.Results324 patients were included. In the overall cohort, the median duration of vancomycin therapy was 3 (interquartile range [IQR] 2–6) days in the negative MRSA nasal PCR group (n = 282) and 6 (IQR 4–9) days in the positive nasal PCR group (n = 42), P < 0.01. In the propensity score-matched cohort, the median number of vancomycin days was 3 (IQR 2–5) and 5 (IQR 4–8.5) in the negative (n = 137) and positive (n = 39) nasal PCR groups, respectively, P < 0.01. This difference persisted in an additional analysis of only patients with no positive respiratory cultures. No significant differences were observed in any secondary outcomes. The MRSA PCR assay demonstrated a positive predictive value of 45% and a negative predictive value of 98%.ConclusionA negative MRSA nasal PCR correlated with fewer days of vancomycin therapy without negatively impacting other clinical outcomes. The use of the MRSA nasal PCR assay may reduce the duration of MRSA-active therapy in PCR-negative patients.Disclosures All authors: No reported disclosures.

Rapid MRSA PCR on respiratory specimens from ventilated patients with suspected pneumonia: a tool to facilitate antimicrobial stewardship.

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of pneumonia in ventilated patients. Our objective was to evaluate the GeneXpert MRSA/SA SSTI Assay (Xpert MRSA/SA) (Cepheid, Sunnyvale, CA) for use in lower respiratory tract (LRT) specimens for rapid MRSA detection and to determine the potentially saved antibiotic-days if a culture-based identification method was replaced by this assay. Remnant LRT samples from ventilated patients submitted to the microbiology laboratory for routine culture were tested using conventional culture and Xpert MRSA/SA. One hundred of 310 LRT specimens met the inclusion criteria. Ten samples were positive for MRSA by Xpert MRSA/SA, while six were positive by routine culture methods. Xpert MRSA/SA correctly identified 5/6 positive and 89/94 negative MRSA specimens, for a sensitivity of 83.3%, specificity of 94.7%, positive predictive value of 45.6%, and negative predictive value of 98.9%. The assay also correctly detected 3/3 positive and 90/97 negative methicillin-susceptible S. aureus (MSSA) specimens, for a sensitivity of 100%, specificity of 92.8%, positive predictive value of 30%, and negative predictive value of 100%. A total of 748 vancomycin and 305 linezolid antibiotic-days were associated with the enrolled specimens. Vancomycin and linezolid utilization could decrease by 68.4% and 83%, respectively, if discontinued 1day after negative polymerase chain reaction (PCR) results. The Xpert MRSA/SA SSTI rapid MRSA PCR assay performed well in respiratory samples from ventilated patients with suspected pneumonia and has the potential to facilitate stewardship efforts such as reducing empiric vancomycin and linezolid therapy.

Clinical utility of a nasal swab methicillin-resistant Staphylococcus aureus polymerase chain reaction test in intensive and intermediate care unit patients with pneumonia

This retrospective study aimed to validate the concordance between nasal swab methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) test and respiratory culture and to determine the number of potentially preventable days of anti-MRSA therapy in patients with pneumonia. Two hundred adult inpatients in the intensive and intermediate care units were included. The nasal swab MRSA PCR test was positive in 55 (27.5%) patients. MRSA was isolated from respiratory culture in 21 (10.5%) patients. The nasal swab MRSA PCR test demonstrated 90.5% sensitivity, 79.9% specificity, 34.5% positive predictive value, and 98.6% negative predictive value. Anti-MRSA therapy was initiated in 168 (84%) patients. Patients in the study received a combined 782days of anti-MRSA therapy; 300days were considered potentially preventable. This study suggests that the nasal swab MRSA PCR test may be used to guide discontinuation of anti-MRSA antibiotics in patients with clinically confirmed pneumonia in the intensive or intermediate care units.

Nasal methicillin-resistant Staphylococcus aureus polymerase chain reaction: a potential use in guiding antibiotic therapy for pneumonia.

The role at admission of nasal polymerase chain reaction (PCR) for patients with methicillin-resistant Staphylococcus aureus (MRSA) in guiding antibiotic therapy for lower respiratory tract infection is unknown. To determine whether nasal MRSA PCR at admission can predict the absence of MRSA in lower respiratory tract secretions. We performed a retrospective study of adult patients admitted to a large urban hospital. Patients had a nasal MRSA PCR test and a lower respiratory tract culture obtained within 48 hours of admission and the culture yielded S aureus. Sensitivity, specificity, and positive and negative predictive values. Our results showed high sensitivity (93.3%) and negative predictive value (95.2%) of nasal PCR for MRSA in the lower respiratory tract. With its high sensitivity and negative predictive value, a nasal MRSA PCR test performed within 48 hours of hospital admission could help guide the discontinuation of MRSA-directed empiric antibiotic therapy in patients who are unlikely to be infected with this organism. A prospective study is needed to confirm these findings.