Prospective Nasal Screening for Methicillin-Resistant Staphylococcus aureus in Critically Ill Patients With Suspected Pneumonia

Negative Nasal Methicillin-Resistant Staphylococcus aureus (MRSA) Polymerase Chain Reaction Rules Out Future MRSA Infections in Severely Injured Trauma Patients

Introduction: Studies have shown that methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) swabs aid in de-escalating and decreasing the duration of antibiotic use in respiratory infections. However, the utility of MRSA PCR swabs is unknown for severely injured trauma patients. The aim of this study is to determine if negative MRSA PCR nasal swabs are associated with future MRSA infections in trauma patients admitted to the intensive care unit (ICU). Methods: Trauma patients admitted to the ICU that had a nasal MRSA PCR from July 2022 to March 2024 were evaluated. Demographics, as well as complication rates (including myocardial infarction, stroke, venous thromboembolism, acute respiratory distress syndrome, acute kidney injury), number and site of cultures obtained, days from MRSA PCR to culture, and positivity of a MRSA infection in those cultures, were evaluated. Results: In the study period, 65 severely injured patients were identified with an infection and nasal MRSA PCR. Most patients were male (74%), suffered a blunt mechanism (85%), and had a 28-day mortality rate of 36.9%. The median injury severity score was 26. Of the 65 injured patients, 7 (10.8%) had a positive MRSA PCR. There were 142 cultures obtained. No patient that had a negative PCR had a positive MRSA infection. The performance characteristics of a MRSA PCR swab included sensitivity (100%), specificity (92%), positive predictive value (29%), and negative predictive value (NPV, 100%). Conclusion: The incidence of MRSA-positive infections in trauma patients is low with a negative MRSA PCR swab, NPV of 100%. On the basis of these findings, there should be consideration of withholding empiric MRSA coverage in trauma ICU patients with a negative MRSA PCR. This may aid in reducing unnecessary antibiotic initiation and healthcare costs. Larger studies are needed to validate these findings and help delineate patients for which empiric MRSA coverage can be withheld.

Antibiotic De-Escalation in the Intensive Care Unit: Rationale and Potential Strategies

Antibiotic de-escalation (ADE) is important to help optimize antibiotic use and balance the positive and negative effects of antimicrobial therapy. ADE should be performed promptly, and infections should be treated with the shortest course of antimicrobials as clinically feasible to avoid unnecessary use of broad-spectrum antimicrobials. Several tools have been developed to increase efficient ADE, including rapid diagnostic tests (ex. multiplex PCR), MRSA nasal PCR/culture, and biomarkers. Multiplex PCR and MRSA nasal PCR/culture have been associated with reductions in inappropriate antibiotic use. Procalcitonin, a biomarker, has been associated with shorter antimicrobial durations in some studies; however, widespread use may be limited by lack of specificity for bacterial infections, cost, and lack of set cut-off points. Additional biomarkers such as IL-6, HMGB1, presepsin, sTREM-1, CD64, PSP, proadrenomedullin, and pentraxin-3 are currently being studied. As technology improves, additional tools may be leveraged to better optimize ADE even better, such as antimicrobial spectrum scoring tools and artificial intelligence (AI). Spectrum scores, which quantify antibiotic activity using specific numeric values, could be incorporated into electronic health records to identify patients on unnecessarily broad antibiotics. AI modeling has the potential to predict personal antibiograms or provide the probability that an empiric regimen may cover a particular infection, among other potential applications. This review will discuss the literature associated with ADE in the ICU, selected tools to help guide ADE, and perspectives on how to implement ADE into clinical practice.

Methicillin-Resistant Staphylococcus aureus Nasal Screening With Polymerase Chain Reaction for Early De-escalation of Empiric Vancomycin in the Treatment of Suspected/Confirmed Respiratory Infection in Critically Ill Patients

BACKGROUND

Vancomycin empirically for methicillin-resistant Staphylococcus aureus (MRSA) pneumonia coverage often is prolonged. With high negative predictive value for MRSA pneumonia, we evaluated the efficacy of MRSA nasal screening with polymerase chain reaction for early de-escalation of empiric vancomycin for treatment of respiratory infections in patients admitted to the intensive care units.

STUDY QUESTION

The impact of MRSA nasal screening on early de-escalation of vancomycin for respiratory infections.

STUDY DESIGN

A retrospective, single-center cohort study was conducted to evaluate the outcomes of vancomycin therapy in patients admitted to the intensive care units with diagnosis of pneumonia before (control group) and after (study group) implementation of MRSA nasal screening.

MEASURES AND OUTCOMES

The primary end point was the difference in duration of vancomycin drug therapy in patients with suspected/confirmed pneumonia between the control and study groups. Secondary end points included the number of vancomycin trough levels obtained, discordance between polymerase chain reaction and sputum culture results, and clinical outcomes.

RESULTS

In total, 123 patients (control: n = 76; study: n = 47) were included. The median vancomycin duration in the control group and the study group was 73.3 hours (54.3-110.6) and 30.2 hours (20.3-39.7), respectively, P < 0.0001. The control group had 2.73 times (95% CI: 2.15-3.45, P < 0.0001) longer vancomycin duration than the study group. There was a significant difference in the number of trough levels obtained between the 2 groups. The median in the control and study groups were 1 (1-3) and 1 (0-1), respectively, P < 0.0001. There was no difference between groups for length of stay, 30-day readmission for MRSA infection, reinitiation of anti-MRSA therapy for infection, vancomycin-resistant enterococci infection within 30 days, acute kidney injury, and in-hospital all-cause mortality.

CONCLUSION

The implementation of a MRSA nasal screening for critically ill patients treated with vancomycin for pneumonia resulted in a significantly shorter duration of vancomycin treatment without negatively affecting patient outcomes.

Impact of a Multiplex PCR Assay for Rapid Diagnosis and Antibiotic Utilization in Trauma Intensive Care Unit Patients with Ventilator-Acquired Pneumonia

Background: Ventilator-associated pneumonia (VAP) is a frequent complication in injured patients. Multiplex polymerase chain reaction (PCR) facilitates rapid identification of many respiratory pathogens prior to formal culture results. Our objective was to evaluate the effect of multiplex PCR implementation in a trauma intensive care unit (TICU) on antibiotic utilization and de-escalation. Patients and Methods: Injured adult patients admitted to the TICU with quantitative respiratory cultures were included. Patients were dichotomized into two groups, before (PRE) or after (POST) implementation of the pneumonia (PNA) panel. The PRE cohort included all patients meeting study criteria from January to June 2021, and the POST cohort included all patients meeting study criteria from January to June 2022, Patients were excluded if there was any documented infection requiring antibiotics other than a respiratory source. Results: During the study period, 60 patients met criteria for inclusion, 30 PRE and 30 POST. Diagnosis of VAP was confirmed in 43.3% PRE and 50% POST patients. The time to antibiotic change was substantially shorter in the POST group (23 h vs. 61 h, p < 0.001). In the POST cohort, 83% of initial antibiotic regimens were eligible for change on the basis of PNA panel. Of these, 88% were changed in a median time of 15.4 h. In all patients, total days of antibiotic therapy (DOT) were not different (9 vs. 10, p = 0.207); however, vancomycin DOT was less in the POST group (2 d vs. 3 d, p ≤ 0.001). In those patients diagnosed with VAP, the total antibiotic (10 vs. 12 d p = 0.008), vancomycin (2 vs. 3 d p = 0.003), and cefepime DOT (3 vs. 4 d 0.029) were substantially less in the POST group. Conclusions: Utilization of multiplex PCR in addition to bacterial culture substantially reduced time to achieve targeted antibiotic therapy in suspected pneumonia. Furthermore, it reduced the number of days of vancomycin therapy.

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. The objective of this study is to test whether the use of MRSA PCR testing can safely reduce inappropriate vancomycin use in an intensive care setting. 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 expected number of hours alive and free of the use of vancomycin within the first 7 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

ClinicalTrials.gov NCT06272994. Registered on February 22, 2024.

Impact of stewardship pharmacist driven MRSA nasal surveillance and de-escalation of anti-MRSA therapy (STEW PHARM MRSA NASAL SURVEILLANCE)

Objective

To determine if implementing stewardship pharmacist-driven methicillin-resistant Staphylococcus aureus (MRSA) nasal surveillance increases use of the test and reduces the inappropriate use of vancomycin for MRSA coverage in patients with pneumonia.

Design

Retrospective pre-/post-intervention study.

Setting

Large teaching acute care hospital.

Participants

Adult patients receiving vancomycin therapy for treatment of pneumonia.

Methods

A stewardship pharmacist ran a report of admitted patients receiving vancomycin and reviewed the patients' records. If the patient's indication was pneumonia and a MRSA nasal swab had not been ordered, the pharmacist contacted the patient's provider and requested an order for it. Upon receipt of a negative MRSA nasal swab result, the pharmacist recommended discontinuation of vancomycin if appropriate.The control group was four weeks prior to the stewardship intervention, where there was no dedicated stewardship pharmacist reviewing MRSA swab utilization. The primary outcome was percentage of patients who had a MRSA swab ordered. Secondary outcomes included percentage of patients who had vancomycin appropriately de-escalated based on MRSA nasal swab results and length of vancomycin therapy.

Result

Percentage of swabs ordered increased from 36.1% (22/61) to 83.7% (41/49) with pharmacist intervention (P < 0.0001). The rate of vancomycin de-escalation following a negative MRSA swab increased from 19.7% (12/61) to 61.2% (30/49) with pharmacist intervention (P < 0.0001).

Conclusion

The results suggest implementing a pharmacist driven MRSA nasal surveillance program into practice could increase the number of MRSA nasal swabs ordered and promote timely de-escalation of vancomycin in patients with pneumonia.

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).

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.

Comparison of Methicillin-Resistant Staphylococcus aureus Nasal Screening Predictive Value in the Intensive Care Unit and General Ward

BACKGROUND

The clinical utility of methicillin-resistant Staphylococcus aureus (MRSA) nasal screening appears promising for antimicrobial stewardship programs. However, a paucity of data remains on the diagnostic performance of culture-based MRSA screen in the intensive care unit (ICU) for pneumonia and bacteremia.

OBJECTIVE

The objective of this study was to compare the predictive value of culture-based MRSA nasal screening for pneumonia and bacteremia in ICU and general ward patients.

METHODS

This multicenter, retrospective study was conducted over a 23-month period. Adult patients with MRSA nasal screening ≤48 hours of collecting a respiratory and/or blood culture with concurrent initiation of anti-MRSA therapy were included. The primary endpoint was to compare the negative predictive value (NPV) associated with culture-based MRSA nasal screening between ICU and general ward patients with suspected pneumonia.

RESULTS

A total of 5106 patients representing the ICU (n = 2515) and general ward (n = 2591) were evaluated. The NPV of the MRSA nares for suspected pneumonia was not significantly different between ICU and general ward patient populations (98.3% and 97.6%, respectively; P = 0.41). The MRSA nares screening tool also had a high NPV for suspected bacteremia in ICU (99.8%) and general ward groups (99.7%) (P = 0.56). The overall positive MRSA nares rates in the ICU and general ward patient populations were 9.1% and 8.2%, respectively (P = 0.283). Moreover, MRSA-positive respiratory and blood cultures among ICU patients were 5.8% and 0.8%, respectively.

CONCLUSION AND RELEVANCE

Our findings support the routine use of MRSA nasal screening using the culture-based method in ICU patients with pneumonia. Further research on the clinical performance for MRSA bacteremia in the ICU is warranted.

Should a MRSA Nasal Swab Guide Empiric Antibiotic Treatment?

MRSA Nasal Swab and Empiric Antibiotic TreatmentMRSA nasal screening has emerged as a potential antimicrobial stewardship tool to guide empiric use of anti-MRSA therapy. The authors address diagnostic considerations when performing MRSA nasal screening and clinical situations in which its results may be used to guide empiric antibiotic therapy in hospitalized patients.

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

BACKGROUND

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.

OBJECTIVE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.