Can Nasal Methicillin-Resistant Staphylococcus aureus Screening Be Used to Avoid Empiric Vancomycin Use in Intra-Abdominal Infection?

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).

Use of nares swab to de-escalate vancomycin for patients with suspected methicillin-resistant Staphylococcus aureus

Introduction

According to the US Center for Disease Control and Prevention, 30%-50% of antibiotic use in hospitals is unnecessary or inappropriate. The coronavirus disease 2019 pandemic further complicates antibiotic use leading to greater initiation of empiric antibiotics. The result is antibiotic overuse and increased duration of unnecessary therapy. Vancomycin is a drug of last resort, primarily relegated to the treatment of Methicillin-Resistant Staphylococcus aureus (MRSA). De-escalating vancomycin can mean waiting on MRSA culture results, which may take up to 96 h. Nares screening for MRSA is shown to possess high negative predictive value for ruling out suspected MRSA pneumonia, intra-abdominal infections, and bacteremia.

Methods

This before-and-after study examines the impact of vancomycin therapy de-escalation due to absence of MRSA colonization detected via PCR assay of nares swabs. An intervention with providers using SMART goals was designed to increase nasal swabbing for MRSA and ultimately decrease vancomycin use at a large, tertiary-care urban hospital.

Results

There was a significant increase in use of vancomycin nares swabs (28/150 vs 48/100, p = 0.040) in the immediate pre/postintervention period, and significant decreases in vancomycin usage days/1,000 patient days of 2.34% per month (p = 0.039) over a two year period after the intervention.

Conclusion

An intervention using PCR nares swabs to detect MRSA led to significant, lasting decreases in vancomycin usage at this hospital. Similar interventions should be planned at hospitals experiencing overuse of this antibiotic.

Methicillin-Resistant Staphylococcus aureus Nasal Swab Is Insufficient to Withhold Empiric Methicillin-Resistant Staphylococcus aureus Pneumonia Coverage in a Trauma Population

INTRODUCTION

Methicillin-resistant staphylococcus aureus (MRSA) nasal colonization is a predictor of MRSA pneumonia in intensive care unit (ICU) patients. Negative nasal swabs have shown up to a 97% negative predictive value for MRSA pneumonia in nontrauma populations, though little investigation has been pursued in trauma patients.

MATERIALS AND METHODS

All trauma patients admitted to the ICU from April 2018 to February 2019 were screened for MRSA colonization by nasal swab. Patients with suspicion for pneumonia underwent bronchoalveolar lavage or quantitative sputum culture and were started on empiric antibiotic therapy based on the swab result. Swab-positive patients were started on empiric MRSA coverage and swab-negative patients were not.

RESULTS

MRSA nasal swab screening was performed in 601 trauma ICU patients. Ninety-six patients subsequently underwent pneumonia workup and were started on an empiric antibiotic regimen based on nasal swab results. Seventeen (17.7%) patients were MRSA nasal swab positive on screening, and 22 (22.9%) patients subsequently had significant growth of MRSA on quantitative respiratory culture. The sensitivity of nasal swab was 50.0% and the specificity was 91.9%. Eleven patients had a negative MRSA nasal swab but a positive MRSA pneumonia (11.5%). Patients with inadequate antibiotic coverage had statistically longer hospital length of stay, ICU length of stay, ventilator days, and rates of unplanned intubation compared to patients with adequate antibiotic coverage.

CONCLUSIONS

Nasal swab screening was not sensitive enough in a trauma population with a high endemic incidence of MRSA colonization to warrant withholding empiric antibiotic MRSA coverage in patients with suspected pneumonia.

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.

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.

Performance of nasal methicillin-resistant Staphylococcus aureus screening for intra-abdominal infections in critically ill adult patients

STUDY OBJECTIVE

Intra-abdominal infections (IAIs) are a common reason for intensive care unit (ICU) admissions, and methicillin-resistant Staphylococcus aureus (MRSA) is an uncommon pathogen in IAIs. Although more data are available in the setting of non-abdominal sources, there are limited data on the performance of nasal MRSA screening for MRSA IAIs. The primary objective of this study was to evaluate the performance of nasal MRSA screening for MRSA IAIs in critically ill adult patients.

DESIGN

This was a multicenter, retrospective, cohort study.

SETTING

A 14-hospital healthcare system between January 1, 2014, and August 31, 2019.

PATIENTS

Adult patients admitted to an ICU for at least 24 h with a diagnosis code for an IAI, a nasal MRSA surveillance screen within 30 days, and an intra-abdominal culture were eligible for inclusion.

INTERVENTION

The primary outcome was to evaluate the performance of nasal MRSA screening for MRSA IAIs by calculating the accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

MEASUREMENTS AND MAIN RESULTS

Out of 863 patients randomly screened, a total of 192 patients were included. The study population had a mean age of 60 (SD ±15) years, and 101 (53%) patients were male. Six (3.1%) patients were positive for an MRSA IAI, of which four (66.7%) demonstrated a positive nasal MRSA screen. A total of 186 (96.8%) patients were negative for a MRSA IAI, of which 19 (10.2%) were nasal MRSA-positive and 167 (89.8%) were nasal MRSA-negative. Nasal MRSA screening demonstrated the following performance: accuracy 89.1% (95% CI: 83.8%-93.1%), sensitivity 66.7% (95% CI: 22.3%-95.7%), specificity 89.8% (95% CI: 84.5%-93.7%), PPV 17.4% (95% CI: 9.4%-30.0%), and NPV 98.8% (95% CI: 96.4%-99.6%). There were no significant differences in clinical outcomes, including renal replacement-free days, ICU and hospital length of stay, and in-hospital mortality.

CONCLUSIONS

Among critically ill adult patients with IAIs, a negative nasal MRSA screen within 30 days may help to empirically exclude MRSA as a causative pathogen.

Collaborative Antimicrobial Stewardship for Surgeons

Antimicrobial stewardship efforts that include surgeons rely on healthy and open communications between surgeons, infectious diseases specialists, and pharmacists. These efforts most frequently are related to surgical prophylaxis, the management of surgical infections, and surgical critical care. Policy should be based on best evidence and timely interactions to develop consensus on how to develop appropriate guidelines and protocols. Flexibility on all sides leads to increasingly strong relationships over time.

Multidisciplinary Tool Kit for Febrile Neutropenia: Stewardship Guidelines, Staphylococcus aureus Epidemiology, and Antibiotic Use Ratios

PURPOSE

Inappropriate vancomycin for febrile neutropenia (FN) is an ideal antimicrobial stewardship target. To improve vancomycin prescribing, we instituted a multifaceted intervention, including an educational guideline with audit for compliance; an antibiotic use audit; and an assessment of local burden of methicillin-resistant Staphylococcus aureus (MRSA) colonization and infection.

MATERIALS AND METHODS

We conducted a quasi-experimental pre-post intervention review of vancomycin initiation for FN on a 32-bed hematology/oncology unit. A retrospective chart review was conducted from November 2015 to May 2016 (preintervention period). In January 2017, we implemented an institutional FN guideline emphasizing criteria for appropriate use. Vancomycin audit was conducted from February 2017 to October 2017 (postintervention period). The primary outcome was appropriateness of vancomycin initiation. We then compared average antibiotic use (days of therapy per 1,000 patient days) for vancomycin and cefepime before and after intervention. Finally, unit-wide MRSA screening cultures were obtained upon admission and bimonthly for 6 weeks (October 2, 2017, to November 9, 2017). Screened patients were followed for 12 months for clinical MRSA infection.

RESULTS

Forty-three (49%) of 88 preintervention patients were started on empiric vancomycin appropriately, compared with 59 (66%) of 90 postintervention patients (P = .02). There was a significant decrease in vancomycin use after intervention. Six (7.1%) of 85 patients screened positive for MRSA colonization. During the 12-month follow-up, no colonized patients developed clinical MRSA infections (positive predictive value, 0.0%). Of the 79 noncolonized patients, 2 developed a clinically significant infection (negative predictive value, 97.5%).

CONCLUSION

Guideline-focused education can improve vancomycin appropriateness in FN and should be bundled with education and feedback about local MRSA epidemiology and antibiotic use rates for maximal stewardship impact.

The prevalence of methicillin-resistant Staphylococcus aureus among diabetic patients: a meta-analysis

AIMS

Diabetic patients have multiple risk factors for colonisation with methicillin-resistant Staphylococcus aureus (MRSA), a nosocomial pathogen associated with significant morbidity and mortality. This meta-analysis was conducted to estimate the prevalence of MRSA among diabetic patients.

METHODS

The MEDLINE, Embase, BIOSIS, and Web of Science databases were searched for studies published up to May 2018 that reported primary data on the prevalence of MRSA in 10 or more diabetic patients. Two authors independently assessed study eligibility and extracted the data. The main outcomes were the pooled prevalence rates of MRSA colonisation and infection among diabetic populations.

RESULTS

Eligible data sets were divided into three groups containing data about the prevalence of MRSA colonisation or in diabetic foot or other infections. From 23 data sets, the prevalence of MRSA colonisation among 11577 diabetics was 9.20% (95% CI, 6.26-12.63%). Comparison of data from 14 studies that examined diabetic and non-diabetic patients found that diabetics had a 4.75% greater colonisation rate (P < 0.0001). From 41 data sets, the prevalence of MRSA in 10994 diabetic foot infection patients was 16.78% (95% CI, 13.21-20.68%). Among 2147 non-foot skin and soft-tissue infections, the MRSA prevalence rate was 18.03% (95% CI, 6.64-33.41).

CONCLUSIONS

The prevalence of MRSA colonisation among diabetic patients is often higher than among non-diabetics; this may make targeted screening attractive. In the UK, many diabetic patients may already be covered by the current screening policies. The prevalence and impact of MRSA among diabetic healthcare workers requires further research. The high prevalence of MRSA among diabetic foot infections may have implications for antimicrobial resistance, and should encourage strategies aimed at infection prevention or alternative therapies.

Clinical Utility of Methicillin-Resistant Staphylococcus aureus Nasal Screening for Antimicrobial Stewardship: A Review of Current Literature

Significant clinical and financial consequences are associated with both inadequate and unnecessary exposure to broad-spectrum antibiotics. As such, antimicrobial stewardship programs seek objective, reliable, and cost-effective tests to identify patients at highest or lowest risk for drug-resistant organisms to guide empirical antimicrobial selection. Use of methicillin-resistant Staphylococcus aureus (MRSA) nasal screening to rule out MRSA in lower respiratory tract infections has led to significant reductions in duration of vancomycin therapy. The clinical utility of MRSA nasal screening in other types of infection remains less clear. This review describes the performance of MRSA nasal screening in predicting MRSA infection, highlights practical considerations for use of MRSA nasal screening, and provides guidance for incorporating MRSA nasal screening into clinical practice. With a high negative predictive value when the prevalence of MRSA is low, MRSA nasal screening is a valuable antimicrobial stewardship tool with potential applications beyond lower respiratory tract infections. In appropriately selected patients, negative MRSA nasal screening can prevent initiation or guide discontinuation of anti-MRSA therapy. Antimicrobial stewardship programs should develop institutional guidelines to promote proper use of MRSA nasal screening. Pharmacists are well positioned to assist with education, interpretation, and application of MRSA nasal screening results.

Nasal-Swab Results for Methicillin-Resistant Staphylococcus aureus and Associated Infections

BACKGROUND

Nasal-swab screening for methicillin-resistant Staphylococcus aureus (MRSA) has a quicker turnaround time than other bacterial culture methods, with results available within 24 h. Although MRSA nasal-swab screening is not intended to guide antimicrobial therapy, this method may give clinicians additional information for earlier tailoring of empiric antimicrobial agents.

OBJECTIVE

To describe the diagnostic characteristics of nasal-swab screening in predicting MRSA infections in hospitalized patients receiving empiric treatment with IV vancomycin.

METHODS

A retrospective observational chart review was conducted for newly admitted adult patients of the Peter Lougheed Centre in Calgary, Alberta, who were treated empirically with IV vancomycin from January to October 2015 and who underwent nasal-swab screening for MRSA. The diagnostic characteristics of nasal-swab screening were calculated in relation to corresponding culture results for samples collected on admission.

RESULTS

For the 273 patients included in this study, nasal-swab screening for MRSA showed the following diagnostic characteristics in relation to bacterial culture results: sensitivity 58.3% (95% confidence interval [CI] 28.6%-83.5%), specificity 93.9% (95% CI 90.0%-96.3%), positive predictive value 30.4% (95% CI 14.1%-53.0%), negative predictive value 98.0% (95% CI 95.1%-99.3%), positive likelihood ratio 9.5 (95% CI 4.9-18.7), and negative likelihood ratio 0.4 (95% CI 0.2-0.9).

CONCLUSIONS

Given the high specificity of this rapid method, clinicians should ensure that patients who are receiving empiric treatment for MRSA infection and who have a positive result on nasal-swab screening continue to receive MRSA coverage until culture results are available. In addition, the high negative predictive value and positive likelihood ratio for nasal-swab screening in a low-prevalence setting suggest that a negative result significantly reduces the probability of MRSA infection. Although nasal-swab screening for MRSA is currently used for determining isolation precautions, this method also had utility in helping clinicians to predict the probability of MRSA infection and in guiding decisions about antimicrobial therapy.

Using MRSA Screening Tests To Predict Methicillin Resistance in Staphylococcus aureus Bacteremia

Bloodstream infections with Staphylococcus aureus are clinically significant and are often treated with empirical methicillin resistance (MRSA, methicillin-resistant S. aureus) coverage. However, vancomycin has associated harms. We hypothesized that MRSA screening correlated with resistance in S. aureus bacteremia and could help determine the requirement for empirical vancomycin therapy. We reviewed consecutive S. aureus bacteremias over a 5-year period at two tertiary care hospitals. MRSA colonization was evaluated in three ways: as tested within 30 days of bacteremia (30-day criterion), as tested within 30 days but accounting for any prior positive results (ever-positive criterion), or as tested in known-positive patients, with patients with unknown MRSA status being labeled negative (known-positive criterion). There were 409 S. aureus bacteremias: 302 (73.8%) methicillin-susceptible S. aureus (MSSA) and 107 (26.2%) MRSA bacteremias. In the 167 patients with MSSA bacteremias, 7.2% had a positive MRSA test within 30 days. Of 107 patients with MRSA bacteremia, 68 were tested within 30 days (54 positive; 79.8%), and another 21 (19.6%) were previously positive. The 30-day criterion provided negative predictive values (NPV) exceeding 90% and 95% if the prevalence of MRSA in S. aureus bacteremia was less than 33.4% and 19.2%, respectively. The same NPVs were predicted at MRSA proportions below 39.7% and 23.8%, respectively, for the ever-positive criterion and 34.4% and 19.9%, respectively, for the known-positive criterion. In MRSA-colonized patients, positive predictive values exceeded 50% at low prevalence. MRSA screening could help avoid empirical vancomycin therapy and its complications in stable patients and settings with low-to-moderate proportions of MRSA bacteremia.

Inclusion of Vancomycin as Part of Broad-Spectrum Coverage Does Not Improve Outcomes in Patients with Intra-Abdominal Infections: A Post Hoc Analysis

BACKGROUND

Management of complicated intra-abdominal infections (cIAIs) includes broad-spectrum antimicrobial coverage and commonly includes vancomycin for the empiric coverage of methicillin-resistant Staphylococcus aureus (MRSA). Ideally, culture-guided de-escalation follows to promote robust antimicrobial stewardship. This study assessed the impact and necessity of vancomycin in cIAI treatment regimens.

PATIENTS AND METHODS

A post hoc analysis of the Study to Optimize Peritoneal Infection Therapy (STOP-IT) trial was performed. Patients receiving piperacillin-tazobactam (P/T) and/or a carbapenem were included with categorization based on use of vancomycin. Univariate and multivariable analyses evaluated effects of including vancomycin on individual and the composite of undesirable outcomes (recurrent IAI, surgical site infection [SSI], or death).

RESULTS

The study cohort included 344 patients with 110 (32%) patients receiving vancomycin. Isolation of MRSA occurred in only eight (2.3%) patients. Vancomycin use was associated with a similar composite outcome, 29.1%, vs. no vancomycin, 22.2% (p = 0.17). Patients receiving vancomycin had (mean [standard deviation]) higher Acute Physiology and Chronic Health Evaluation II scores (13.1 [6.6] vs. 9.4 [5.7], p < 0.0001), extended length of stay (12.6 [10.2] vs. 8.6 [8.0] d, p < 0.001), and prolonged antibiotic courses (9.1 [8.0] vs. 7.1 [4.9] d, p = 0.02). After risk adjustment in a multivariate model, no significant difference existed for the measured outcomes.

CONCLUSIONS

This post hoc analysis reveals that addition of vancomycin occurred in nearly one third of patients and more often in sicker patients. Despite this selection bias, no appreciable differences in undesired outcomes were demonstrated, suggesting limited utility for adding vancomycin to cIAI treatment regimens.