Methicillin-resistant Staphylococcus Aureus Nasal Swab Research Articles

513 Predictive Values of MRSA Nasal Swabs for Pneumonia in Burn ICU Patients

Abstract Introduction Sepsis in burn-injured patients remains a leading cause of mortality in those who survive initial resuscitation. Methicillin-resistant Staphylococcus aureus (MRSA) is a common causative pathogen for pneumonia in burn-injured patients. Studies evaluating the predictive value of MRSA nasal swabs for pneumonia have largely excluded the burn-injured population. Methods Patients 18 years or older admitted to the Burn ICU at a tertiary medical center from 2016 to 2021 were included if they had any burns, a pneumonia ICD-10 code, an MRSA nasal swab obtained during admission, and any respiratory cultures associated with at least five consecutive days of antibiotics. Results There were 267 instances of pneumonia across 136 patients included. MRSA nasal swabs had an overall sensitivity of 39%, specificity of 98.7%, positive predictive value (PPV) of 84.2%, and negative predictive value (NPV) of 89.9%. MRSA nasal swabs obtained less than seven days from antibiotic initiation had a specificity of 98.6% and NPV of 98.6%; meanwhile, swabs obtained at least seven days from antibiotic initiation had a specificity of 98.7% and NPV of 86.4%. Conclusions The high specificity and NPV indicate that negative MRSA nasal swabs obtained less than seven days from antibiotic initiation may be used to de-escalate anti-MRSA antibiotics in clinically stable burn-injured patients with suspicion of pneumonia. The decrease in NPV suggests that it may be beneficial to obtain a repeat swab periodically or upon suspicion of pneumonia. Applicability of Research to Practice This study is the first to measure the sensitivity, specificity, PPV, and NPV of the MRSA PCR nasal swab in a cohort comprised only of patients admitted to a burn intensive care unit. The findings support the use of the MRSA nasal swab as a tool to aid in the decision to initiate or de-escalate anti-MRSA antimicrobials for pneumonia.

Predictive Value of Methicillin-Resistant Staphylococcus aureus Nasal Swab PCR Assay for MRSA Infection in Critically Ill Pediatric Patients.

Critically ill pediatric patients are frequently initiated methicillin-resistant Staphylococcus aureus (MRSA) active antibiotics during infection evaluation even though MRSA infections are rare in many patient populations. The MRSA nasal swab polymerase chain reaction assay (MRSA-NS-PCR) is a test that has been shown to have a high negative predictive value (NPV) for MRSA infection in adults. This study evaluated the diagnostic test characteristics of the MRSA-NS-PCR in predicting the presence of MRSA infection in critically ill pediatric patients. A retrospective cohort study was performed in a 44-bed pediatric intensive care unit (PICU) between 2013 and 2017. 3860 pediatric patients (54% male, median age 4 years [IQR 1-11 years]) admitted to the PICU who met pediatric systemic inflammatory response syndrome (pSIRS) criteria, were screened with a MRSA-NS-PCR, and had cultures obtained within seven days of MRSA-NS-PCR collection were included. Predictive values and post-test probabilities of the MRSA-NS-PCR for MRSA infection were calculated. MRSA-NS-PCR was positive in 8.6% of patients. MRSA infection was identified in 40 patients, equaling an incidence rate of 2 per 1000 patient days. The MRSA-NS-PCR demonstrated a positive predictive value (PPV) of 9.7%, a NPV of 99.8%, and a post-test probability for a negative test of 0.2% for MRSA infection. The MRSA-NS-PCR has a poor PPV but a high NPV for MRSA infection in PICU patients when the incidence of MRSA infection is low. Creation of protocols to guide antimicrobial selection based on MRSA-NS-PCR results may lead to improved antimicrobial stewardship and significant risk reduction.

1223. Utilizing Multiple Antimicrobial Stewardship Metrics to Trend Vancomycin Use in an Implementation Study

Abstract Background Inpatient IV vancomycin use is often inappropriately prolonged. Methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) nares swabs have shown high negative predictive values for many infections and can guide appropriate vancomycin de-escalation. Antibiotic stewardship programs (ASPs) often monitor vancomycin use in days of therapy (DoT) per 1000 patient days present (PDP). This measure can be affected, especially for smaller facilities, by changes in bed capacity and prolonged stays and thus may not accurately reflect vancomycin use. We evaluated whether alternative metrics of vancomycin use would show different impacts during a multi-step ASP intervention to reduce inappropriate vancomycin use at Veterans Affairs Tennessee Valley Healthcare System. Figure 1 Run chart of vancomycin DoT/1000 PDP at the Tennessee Valley Healthcare System (TVHS) in two years prior to intervention. Methods In September 2021, the ASP, with multiple stakeholders, initiated use of MRSA nasal swabs to inform vancomycin de-escalation. From 7/2022 to 3/2023, we performed iterative Plan-Do-Study-Act intervention cycles including educating medicine and surgical divisions on MRSA swab result interpretation, educating nurses on timely swab collection, replacing MRSA culture swabs with PCR swabs, and adding MRSA swab orders to vancomycin order sets. In April 2022, in addition to DoT/1000 PDP, we began measuring mean, median, and mode DoT per vancomycin course initiated by start week. Results Despite multiple interventions beginning July 2022, vancomycin use in DoT/1000 PDP increased to a peak of 106 DoT/1000 PDP in September 2022. In that same period, median and mode DoT per vancomycin initiation remained steady at 2 days and 1 day, respectively. Figure 2 Run chart of vancomycin DoT/1000 PDP at the TVHS from April 2022 to March 2023. Specific ASP interventions are annotated on the dates they occur. Figure 3 Run chart of mean, median, and mode days of vancomycin therapy per vancomycin course initiated at the TVHS from April 2022 to March 2023. Specific ASP interventions are annotated on the dates they occur. Conclusion DoT/1000 PDP may not be the best metric to evaluate efforts to reduce inappropriate vancomycin use. By tracking mean, median, and mode of DoT per individual vancomycin course, we determined that most providers already practice rapid de-escalation, minimizing patient vancomycin exposure. This method also allows us to quickly detect changes in prescribing patterns and determine whether interventions were warranted. More evaluation of antibiotic use metric appropriateness based on desired outcome is needed in ASPs. Disclosures Milner Staub, MD, MPH, Gilead: Stocks/Bonds|Johnson & Johnson: Stocks/Bonds

Predictive value of methicillin-resistant staphylococcus aureus nasal swab in patients with COVID-19 pneumonia and secondary bacterial pneumonia

ObjectiveTo determine the performance measures of admission methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs for MRSA bacterial pneumonia in patients co-infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). MethodsThe study included patients admitted with SARS-CoV-2-positive nasopharyngeal specimens, MRSA nasal screens, and bacterial cultures to assess secondary MRSA pneumonia. Results293 patients and 662 microbiological cultures evaluated. Overall, the specificity (91.8% [95% CI 88.6% to 95%]) and negative predictive value (NPV 97.4% [95% CI 95.4% – 99.3%]) of MRSA nasal swabs was high. However, the sensitivity (46.2%; 95% CI 19.1% to 73.3%) and positive predictive value (PPV 20.7%; 95% CI 59.5 – 35.4%) were low. Those patients in the MRSA nasal swab negative group had a shorter median duration of linezolid therapy. ConclusionsSARS-CoV-2 infection doesn't reduce the specificity or negative predictive value of MRSA nasal swabs for secondary MRSA pneumonia.

Pediatric Utilization of Methicillin-resistant Staphylococcus aureus Nasal Swabs for Antimicrobial Stewardship.

Methicillin-resistant Staphylococcus aureus (MRSA) can cause serious infections and empiric treatment regimens in children frequently include an anti-MRSA antibiotic. Studies in adults have demonstrated a high negative predictive value (NPV) of MRSA nasal swabs (MNS) in a variety of infectious syndromes. Negative MNS have been utilized as a tool to guide de-escalation of anti-MRSA antibiotics in adults, especially in those with lower respiratory tract infections, but data in children is minimal. The primary objective of this study was to determine the NPV and positive predictive value (PPV) of MNS in children hospitalized for treatment of an infection. This was a single-site, retrospective cohort study of pediatric patients admitted with a suspected infectious diagnosis who had an MNS performed during their hospitalization between June 1, 2018 and November 25, 2022. This study identified 172 patients who met the inclusion criteria. Eleven (6.4%) nasal swabs were positive for MRSA and 10 (5.8%) microbiological cultures from suspected sources of infection were identified to be positive for MRSA. The MNS was found to have a sensitivity of 20%, specificity of 94%, PPV of 18% and NPV of 95% for all sites of infection. MNS has a high NPV and low PPV in children. MNS can be utilized as an antimicrobial stewardship tool to guide the safe de-escalation of anti-MRSA antibiotics in children.

Ventilator-Associated Methicillin-Resistant Staphylococcus aureus (MRSA) Pneumonia in a Patient with a Negative MRSA Nasal Swab.

BACKGROUND Methicillin-resistant Staphylococcus aureus (MRSA) pneumonia is associated with high morbidity and mortality. Recently, MRSA testing by nasal swab has been utilized to "exclude" pneumonia caused by MRSA, given its high negative-predictive value (NPV). We present, however, a case of MRSA pneumonia diagnosed by endotracheal aspirate culture (EAC) in a patient with a negative MRSA nasal swab. CASE REPORT A 58-year-old woman presented with septic shock and respiratory failure. Chest X-ray (CXR) on admission was unrevealing; however, computed tomography (CT) revealed multifocal pneumonia. Intensive Care Unit (ICU)-level care was required for mechanical ventilation and vasopressors. She initially improved with treatment of community-acquired pneumonia (CAP) and was extubated on hospital day 6; however, she then developed a fever, tachycardia, and respiratory distress necessitating re-intubation later that day. Repeat CXR demonstrated a new left lower lobe infiltrate. Blood cultures were drawn and vancomycin and cefepime were started to cover for ventilator-associated pathogens. An EAC and nasal swab were collected to test for MRSA. The next day (day 7), the MRSA nasal swab returned negative, and vancomycin was discontinued. Our patient continued to experience fevers, worsening leukocytosis, and ongoing vasopressor need. On hospital day 9, the EAC results were obtained, and were positive for MRSA. Vancomycin was restarted and our patient recovered. CONCLUSIONS Negative MRSA nasal screening may be considered grounds to de-escalate empiric MRSA antibiotics if MRSA prevalence is low. However, in critically ill patients with high risk and suspicion for MRSA pneumonia, discontinuing empiric MRSA coverage should be done with caution or clinicians should wait until respiratory culture results are obtained before de-escalating antibiotics.

The Clinical Utility of MRSA Nasal Surveillance Swabs in Ruling-Out MRSA Infections in Children.

The utility of methicillin-resistant Staphylococcus aureus (MRSA) nasal surveillance swabs has not been well-described in children. This retrospective, cohort study yielded a negative predictive value of 99.4% for an initial negative MRSA nasal surveillance swab in 165 hospitalized children with a suspected infection and clinical cultures obtained from a likely site of infection.

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...

Implementation of MRSA Nasal Swabs as an Antimicrobial Stewardship Intervention to Decrease Anti-MRSA Therapy in COVID-19 Infection.

In the early stages of treating patients with SARS-CoV-2, limited information was available to guide antimicrobial stewardship interventions. The COVID-19 Task Force and Antimicrobial Stewardship Committee, at a 988-bed academic medical center, implemented the use of methicillin-resistant Staphylococcus aureus (MRSA) nasal swab polymerase chain reaction (PCR) testing to assist with the de-escalation of anti-MRSA therapy in patients with suspected superimposed bacterial pneumonia in COVID-19. A retrospective study was conducted to evaluate the impact of MRSA nasal swab PCR testing on the rate of anti-MRSA therapy between 13 April 2020 and 26 July 2020. A total of 122 patients were included in the analysis. Of the patients included in the final analysis, 58 (47.5%) had anti-MRSA therapy discontinued and 41 (33.6%) avoided anti-MRSA therapy completely due to a negative swab result. With the implementation of MRSA nasal swab PCR testing in COVID-19 patients, anti-MRSA therapy was reduced in 81% of patients in this study. In patients who continued with anti-MRSA therapy, nasal swabs were either positive for MRSA or an alternative indication for anti-MRSA therapy was noted. Only three patients in the cohort had MRSA identified in a sputum culture, all of whom had anti-MRSA therapy continued. MRSA nasal swab PCR testing may serve as an effective antimicrobial stewardship tool in COVID-19 pneumonia.

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.

Ventilator-Associated Pneumonia Due to MRSA vs. MSSA: What Should Guide Empiric Therapy?

The guidelines on ventilator-associated pneumonia (VAP) recommend an empiric therapy against methicillin-resistant Staphylococcus aureus (MRSA) according to its prevalence rate. Considering the MRSA and MSSA VAP prevalence over the last 9 years in our tertiary care hospital, we assessed the clinical value of the MRSA nasal-swab screening in either predicting or ruling out MRSA VAP. We extracted the data of 1461 patients with positive bronchoalveolar lavage (BAL). Regarding the MRSA nasal-swab screening, 170 patients were positive for MRSA or MSSA. Overall, MRSA had a high prevalence in our ICU. Despite the COVID-19 pandemic, there was a significant downward trend in MRSA prevalence, while MSSA remained steady over time. Having VAP due to MRSA did not have any impact on LOS and mortality. Finally, the MRSA nasal-swab testing demonstrated a very high negative predictive value for MRSA VAP. Our results suggested the potential value of a patient-centered approach to improve antibiotic stewardship.

Evaluation of the Negative Predictive Value of Methicillin-Resistant Staphylococcus aureus Nasal Swab Screening in the Medical Intensive Care Units and Its Effect on Antibiotic Duration

BackgroundIn addition to active surveillance of methicillin-resistant Staphylococcus aureus (MRSA) carrier, MRSA nasal screening can be valuable for antibiotic de-escalation. This study aimed to assess the correlations between the MRSA nasal swab and subsequent culture results in patients admitted to medical intensive care units (MICU). The impact of MRSA nasal swab on the antibiotic duration was also evaluated.Materials and MethodsThis retrospective study enrolled patients who received glycopeptides in the MICU of a medical center in 2019. Patients treated with glycopeptides for over 2 days before MICU admission were excluded. The associated data were collected through the electronic medical record system. The negative predictive value (NPV) of MRSA nasal swabs for MRSA infection was calculated, and their influence on empirical glycopeptide treatment duration was analyzed.ResultsOf the 338 patients who met the inclusion criteria, 277 underwent MRSA nasal screening. The NPV of MRSA-negative nasal swab for subsequent MRSA infection was 98.4%. The glycopeptide treatment duration of the patients with and without nasal screening was not significantly different (4.2 ± 2.8 vs 4.4 ± 3.0 days, p = 0.577). Of the 120 patients with MRSA-negative nasal swab and no subsequent MRSA infection, 75 continued empirical glycopeptides therapy. The additional treatment time was 3 days (interquartile range: 2–6 days).ConclusionThe MRSA nasal swabs have high NPV for MRSA infection in critically ill patients. However, it has no impact on the empirical glycopeptide treatment duration. The value of MRSA nasal swabs should be advocated to optimize antibiotic therapy.

Evaluation of the impact of nasal colonization with methicillin-resistant Staphylococcus aureus on left ventricular assist device infections.

In this retrospective cohort study, we evaluated the predictive value of methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs for the development of MRSA infections in patients with left ventricular assist devices. In 106 patients, the MRSA nasal swab had a negative predictive value of 92.9% demonstrating a potential role in antibiotic de-escalation.

Effectiveness of an electronic health system-based best-practice advisory to enhance the time to de-escalation of vancomycin for respiratory indications.

Methicillin-resistant Staphylococcus aureus (MRSA) infection is highly unlikely when nasal-swab results are negative. We evaluated the impact of an electronic prompt regarding MRSA nasal screening on the length of vancomycin therapy for respiratory indications. Retrospective, single-center cohort study. Tertiary-care academic medical center (Mayo Clinic) in Jacksonville, Florida. Eligible patients received empiric treatment with vancomycin for suspected or confirmed respiratory infections from January through April 2019 (preimplementation cohort) and from October 2019 through January 2020 (postimplementation cohort). The electronic health system software was modified to provide a best-practice advisory (BPA) prompt to the pharmacist upon order verification of vancomycin for patients with suspected or confirmed respiratory indications. Pharmacists were prompted to order a MRSA nasal swab if it was not already ordered by the provider. We reviewed patient records to determine the time from vancomycin prescription to de-escalation. The secondary end point was incidence of acute kidney injury. The study included 120 patients (preimplementation, n = 61; postimplementation, n = 59). Median time to de-escalation was significantly shorter for the postimplementation cohort: 76 hours (interquartile range [IQR], 52-109) versus 42 hours (IQR, 37-61; P = .002). Acute kidney injury occurred in 11 patients (18%) in the preimplementation cohort and in 3 patients (5%) in the postimplementation cohort (P = .01; number needed to treat, 8). Implementation of a BPA notification for MRSA nasal screening helped decrease the time to de-escalation of vancomycin.

Clinical utility of negative methicillin-resistant Staphylococcus aureus (MRSA) nasal surveillance swabs in skin and skin structure infections

BackgroundNegative methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs have a high negative predictive value of approximately 99% in respiratory infections. There is, however, a lack of data evaluating its use beyond respiratory infections. MethodsWe conducted a retrospective analysis to determine the clinical utility of MRSA swabs for identifying MRSA-associated skin and skin structure infections (SSSIs) and the potential effects on antimicrobial stewardship efforts. Baseline characteristics, culture data, and antibiotic data were collected to determine the difference in duration of vancomycin therapy. Positive predictive value, negative predictive value, sensitivity, and specificity were secondary outcomes. ResultsA total of 473 patients were included, of which 156 patients had a positive MRSA nasal swab and 317 patients had a negative swab. The median duration of vancomycin was 4 days in the positive group and 3 days in the negative group (P = .01). The positive predictive value and negative predictive value were 22.4% and 97.5%. The sensitivity and specificity were 81.4% and 71.9%. ConclusionPatients with a negative MRSA nasal swab received approximately 1 day less of vancomycin, which represented a decrease in drug administered. The negative predictive value for SSSIs is promising, showing potential for the role of MRSA nasal swabs in de-escalating therapy.

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

The evaluation of five commercial bacteriophage cocktails against methicillin-resistant Staphylococcus aureus isolated from nasal swab samples.

Infections due to methicillin-resistant Staphylococcus aureus (MRSA) are a growing concern for public health resulting in increase in morbidity, length of hospital stay, and cost of treatment. MRSA nasal swab screening may give clinicians additional information for decision of empiric antimicrobial agents. While increasing antibiotic resistance leads to new treatment approaches, bacteriophages are one of the most promising methods for these alternatives. It was aimed to determine the effectiveness of bacteriophages against MRSA isolates. Nasal swab samples were collected from outpatients without any evidence of infection who applied to Hatay, Mersin and Gaziantep family and immigration health centers. A series (35) were isolated from Turkish patients, and G series (64) were isolated from Syrian immigrants. Methicillin resistance was determined phenotypically and genotypically. Also, antibiotic susceptibilities of all isolates were determined against erythromycin, clindamycin, gentamicin, linezolid, rifampicin, and mupirocin. The total antimicrobial resistance rates of isolates were found to be 11%, 28%, 8%, 5%, 16%, 19%, and 29% respectively. The high susceptibility rate against ciprofloxacin (88.8%) was remarkable. The overall susceptibility of MRSA strains to ENKO, INTESTI, PYO, SES, and staphylococcal bacteriophages was 67.7%, 55.5%, 53.5%, 61.6% and 44.4%, respectively.The antibiotic susceptibility rates (except erythromycin) and efficacy of bacteriophages were higher in group A. Considering that high efficacy rates were not achieved in the study and the sensitivity rates of Turkish isolates to all phages were found to be higher than those of Syrian isolates, searching for phages in the geographic regions where the pathogen is common may be helpful to obtain suitable phages for treatment.

Predictive Value of the Methicillin-Resistant Staphylococcus aureus Nasal Swab for Methicillin-Resistant Staphylococcus aureus Ventilator-Associated Pneumonia in the Trauma Patient.

Background: Many trauma centers have empiric treatment algorithms for ventilator-associated pneumonia (VAP) treatment prior to culture results that include antibiotic agents for methicillin-resistant Staphylococcus aureus (MRSA) coverage that can have adverse effects. This is the only study to evaluate risk factors and MRSA nasal swabs to risk-stratify trauma patients for MRSA VAP, thereby potentially limiting the need for empiric vancomycin. Patients and Methods: This was a single institution retrospective cohort study. Adult patients admitted to the trauma intensive care unit (ICU) between January 2013 and December 2017 who had a MRSA nasal swab and subsequently met criteria for VAP were included. Demographics, risk factors for MRSA pneumonia, and culture results were collected. Results: A total of 140 patients met inclusion criteria. The negative predictive value (NPV) of MRSA nasal swab at predicting subsequent MRSA pneumonia was 97%. The sensitivity, specificity, and positive predictive value were 50.0%, 96.2%, and 44.4%, respectively. Smokers were more likely to develop MRSA pneumonia, odds ratio: 7.0 (p = 0.02). When considering non-smokers with a negative MRSA nasal swab, NPV was 100%. Conclusions: This is the only study to date that assesses the utility of MRSA nasal swab and risk factor data to guide empiric VAP antibiotic therapy in trauma patients. Smoking was found to be a risk factor for MRSA pneumonia. The use of MRSA nasal swabs in combination with smoking status to guide empiric use of MRSA coverage antibiotic agents is recommended because of a 100% NPV. When utilized, as many as 68% of patients may safely be spared MRSA coverage antibiotic agents and the related adverse effects.

Sensitivity and Specificity of prior Methicillin-Resistant Staphylococcus aureus Nasal Swab Results for Predicting Methicillin-Resistant Staphylococcus aureus Infections in Intensive Care Unit Admissions Over a 1-Year Period: A Pilot Study.

Objective:Methicillin-resistant Staphylococcus aureus (MRSA) continues to be a pathogen worldwide. Empiric anti-MRSA therapy is often prescribed in hospital inpatients with potential infection. Recent studies have suggested, particularly for respiratory infections, that MRSA colonization as determined by nasal swab has a high negative predictive value (NPV) for MRSA infections during the index hospitalization. We examined the predictive value of a prior intensive care unit (ICU) MRSA nasal swab on the results from a subsequent ICU admission in the same patient and the results of the latter admission MRSA nasal swab.Methods:A retrospective chart review of patients 18 years or older admitted to a large tertiary care hospital in the Midwest of the United States in 2016 who had a MRSA nasal swab performed and had an ICU admission stay of over 24 h was conducted. This group of patients was matched to a patient list of subjects who were admitted as an inpatient to the same ICU at least once during the following year. Data were collected on demographic and clinical information, as well as the results of MRSA swabs and the presence of a MRSA infection during both hospitalizations. Predictive values were calculated using 2 × 2 tables including sensitivity and specificity of a first MRSA swab result with a MRSA infection during the subsequent ICU stay.Findings:Seventy-seven patients were matched who had MRSA swabs performed on two separate ICU admissions. The negative predictive value of the first MRSA swab result on a MRSA infection during the second ICU stay was 96%.Conclusion:In this pilot study, a previous negative MRSA nasal swab may predict a lack of a MRSA infection in a subsequent infection during a 1-year period.

21. Association of MRSA Prevalence and Hospital-level Antibiotic Use: A Retrospective Study Across 122 Acute-care Hospitals

BackgroundThe prevalence of methicillin-resistant Staphylococcus aureus (MRSA), varies across geographic regions, which could contribute to regional variation in antibiotic use. In this study, we evaluated whether local MRSA prevalence rates were associated with hospital-level antibiotic use across the Veterans Health Administration (VHA).MethodsThis retrospective cohort included all acute-care patients admitted in VHA hospitals during 2016. Anti-MRSA antibiotics were identified per National Healthcare Safety Network definitions and use was quantified as days-of-therapy (DOT) per 1000 days-present. Hospital-level MRSA prevalence (colonization and/or infection) was determined by calculating the proportion of admissions with a positive MRSA nasal swab and/or a MRSA-positive clinical culture obtained ≤1 day before or ≤2 days after admission. Negative binomial regression models were used to determine the association between a hospital’s MRSA prevalence and its antibiotic use, after accounting for intra-hospital clustering, patient case-mix, month of admission, and use of hospital-based stewardship strategies.ResultsThere were 548,476 admissions across 122 hospitals. The median rate of MRSA prevalence at admission was 8.0% (IQR 6.7–9.7%). Hospital level median use of anti-MRSA and total antibiotics was 96.5 (interquartile range [IQR] 81.1–116.9) and 562.1 (IQR 505.9–631.6) DOT per 1,000 days-present, respectively. In a hospital-level risk adjusted analysis, a hospital’s MRSA prevalance was significantly associated with its monthly use of both anti-MRSA and total antibiotics (IRR=1.05, 95% 1.02–1.07; IRR=1.02, 95% CI, 1.01–1.03). A 5% increase in the hospital’s MRSA prevalence was associated with an increase in the monthly use of anti-MRSA antibiotics and total antibiotics by 23.6 and 8.3 DOT per 1,000 days-present, respectively.ConclusionHigher hospital-level MRSA prevalence was associated with significantly higher rates of antibiotic utilization, even after adjusting for case-mix and reported antibiotic stewardship strategies. Future benchmarking of anti-MRSA antibiotic use across hospitals may need to risk-adjust using baseline rates of MRSA prevalence.Disclosures Daniel J. Livorsi, MD, MSc, Merck and Company, Inc (Research Grant or Support) Rajeshwari Nair, PhD, Merck and Company, Inc. (Research Grant or Support)