Using active methicillin-resistant Staphylococcus aureus surveillance nasal swabs to predict clinical respiratory culture results

Predictive Value of MRSA Nares Colonization in Diabetic Foot Infections: A Systematic Review and Bivariate Random Effects Meta-Analysis

The primary objective of this study was to assess the negative predictive value of methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs in MRSA diabetic foot infections. MEDLINE and Cochrane Library were searched from inception to May 1, 2020. The following search string was used: (methicillin-resistant S. aureus OR MRSA) AND (nasal OR nares) AND (diabetic OR foot OR diabetic foot infections). All studies that contained data comparing MRSA nasal swab positivity to wound cultures from diabetic foot infections and met the inclusion criteria were included. Among the 86 relevant studies, 6 studies with 8706 diabetic patients were included. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline extension for Diagnostic Test Accuracy reviews was followed. The primary meta-analysis outcomes were the negative and positive predictive values of MRSA nasal swabs for MRSA diabetic foot infections. The pooled specificity and pooled sensitivity were determined by generating hierarchical summary receiver characteristic operating curves. In the bivariate meta-analysis, involving the 6 studies, pooled sensitivity and specificity was 41.7% (95% confidence interval = 32.9, 51) and 94.1% (95% confidence interval = 89.5, 96.8), respectively. In low-moderate MRSA prevalence levels (<15%), negative predictive value of MRSA nasal swab was >90% and positive predictive value was <55%. This meta-analysis suggests that in patients with diabetic foot infections, the nasal swab MRSA screen has a poor positive predictive value but an excellent negative predictive value in regions of low to moderate prevalence of MRSA diabetic foot infections.

Evaluation of the reliability of MRSA screens in patients undergoing universal decolonization

PURPOSE

Colonization of methicillin-resistant Staphylococcus aureus (MRSA) can be detected via nasal screens. Evidence indicates that negative MRSA nasal screens may be used to de-escalate anti-MRSA antibiotics in pulmonary infections. In the ICU, universal decolonization with intranasal mupirocin is implemented to reduce MRSA infection risk. This study aimed to determine whether mupirocin administration affects the reliability of MRSA PCR nasal screens.

METHODS

This retrospective study divided subjects based on timing of intranasal mupirocin administration-before and after MRSA screen. Subjects with confirmed pulmonary infection that received vancomycin, blood/respiratory cultures, and had MRSA PCR screen collected were included. Subjects with concurrent infection requiring vancomycin or MRSA infection in prior 30 days were excluded. Primary outcome of this non-inferiority study was the negative predictive value (NPV) of the screen. Secondary outcomes included the positive predictive value (PPV), sensitivity, and specificity of the screen and duration of vancomycin.

RESULTS

Ultimately, 125 subjects were included in each group. The NPV in the group receiving mupirocin before screen was 95.2%, whereas the NPV in the group receiving mupirocin after screen was 99%. The difference between groups was -3.8% (90% CI -7.8%-0.2%; p=0.31), which failed to meet non-inferiority criteria. The secondary outcomes of PPV, sensitivity and specificity of the screen were similar in both groups. The duration of vancomycin was significantly longer in subjects receiving mupirocin before screen (3 days vs. 2 days; p<0.05).

CONCLUSION

Intranasal mupirocin prior to the screen may reduce NPV in pulmonary infections. Approach de-escalation of vancomycin based on screen results with caution.

Accuracy of Molecular Amplification Assays for Diagnosis of Staphylococcal Pneumonia: a Systematic Review and Meta-analysis

Rapid and accurate identification of staphylococcal pneumonia is crucial for effective antimicrobial stewardship. We performed a meta-analysis to evaluate the diagnostic value of nucleic acid amplification tests (NAAT) from lower respiratory tract (LRT) samples from suspected pneumonia patients to avoid superfluous empirical methicillin-resistant Staphylococcus aureus (MRSA) treatment. PubMed, Scopus, Embase, Web of Science, and the Cochrane Library Database were searched from inception to 2 September 2020. Data analysis was carried out using a bivariate random-effects model to estimate pooled sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR). Of 1,808 citations, 24 publications comprising 32 data sets met our inclusion criteria. Twenty-two studies (n = 4,630) assessed the accuracy of the NAAT for methicillin-sensitive S. aureus (MSSA) detection, while 10 studies (n = 2,996) demonstrated the accuracy of the NAAT for MRSA detection. The pooled NAAT sensitivity and specificity (with 95% confidence interval [CI]) for all MSSA detection were higher (sensitivity of 0.91 [95% CI, 0.89 to 0.94], specificity of 0.94 [95% CI, 0.94 to 0.95]) than those of MRSA (sensitivity of 0.75 [95% CI, 0.69 to 0.80], specificity of 0.88 [95% CI, 0.86 to 0.89]) in lower respiratory tract (LRT) samples. NAAT pooled sensitivities differed marginally among different LRT samples, including sputum, endotracheal aspirate (ETA), and bronchoalveolar lavage (BAL) fluid. Noticeably, NAAT pooled specificity against microbiological culture was consistently ≥88% across various types of LRT samples. A meta-regression and subgroup analysis of study design, sample condition, and patient selection method could not explain the heterogeneity (P > 0.05) in the diagnostic efficiency. This meta-analysis has demonstrated that the NAAT can be applied as the preferred initial test for timely diagnosis of staphylococcal pneumonia in LRT samples for successful antimicrobial therapy.

Utility of methicillin-resistant Staphylococcus aureus (MRSA) nasal screening in patients with acute myeloid leukemia (AML)

BACKGROUND

Current literature has demonstrated the utility of the MRSA nasal screen as a de-escalation tool to decrease unnecessary anti-MRSA antibiotic therapy. However, data on the applicability of this test in patients with hematologic malignancy is lacking.

METHODS

This is a single-center, retrospective cohort study of patients with acute myeloid leukemia (AML) with or without a history of hematopoietic cell transplant (HCT), with pneumonia and MRSA nasal screening with respiratory cultures obtained. The primary outcome was to determine the negative predictive value (NPV) of the MRSA nasal screen for MRSA pneumonia. Secondary outcomes included sensitivity, specificity, positive predictive value (PPV) of the MRSA nasal screen and prevalence of MRSA pneumonia.

RESULTS

Of 98 patients with AML and pneumonia, the prevalence of MRSA pneumonia was 4.1% with confirmed positive MRSA respiratory cultures observed in 4 patient cases. In patients with confirmed MRSA pneumonia, 3 had positive MRSA nasal screens while 1 had a false negative result, possibly due to a long lag time (21 days) between MRSA nasal screen and pneumonia diagnosis. Overall, the MRSA nasal screen demonstrated 75% sensitivity and 100% specificity, with a PPV of 100% and a NPV of 98.9%.

CONCLUSIONS

Given the low prevalence, empiric use of anti-MRSA therapy in those AML and HCT patients with pneumonia may not be warranted in clinically stable patients. For patients in whom empiric anti-MRSA antibiotics are initiated, nasal screening for MRSA may be utilized to de-escalate anti-MRSA antibiotics in patients with AML with or without HCT.

Evaluation of the negative predictive value of methicillin-resistant Staphylococcus aureus nasal swab screening in patients with acute myeloid leukemia

OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs are utilized to guide the discontinuation of empiric MRSA therapy. In multiple studies, MRSA nasal swabs have been shown to have a negative predictive value (NPV) of ~99% in non-oncology patients with pneumonia and other infections. We evaluated the performance characteristics of a negative MRSA nasal swab in the acute myeloid leukemia (AML) populaion to determine its NPV.

DESIGN

Retrospective chart review.

PATIENTS

This study included adult AML patients with a suspected infection and a MRSA nasal swab collected between 2013 and 2018.

METHODS

MRSA nasal swab and culture-documented infections were identified to determine the sensitivity, specificity, NPV, and positive predictive value of the MRSA nasal swabs.

RESULTS

In total, 194 patients were identified, and 484 discrete encounters were analyzed. Overall, 468 (97%) encounters had a negative MRSA nasal swab upon admission with no cultured documented MRSA infection during their hospitalization. However, 3 encounters (0.6%) had a negative MRSA nasal swab with a subsequent cultured documented MRSA infection during their admission. Identified infections were bacteremia (n = 2) and confirmed pneumonia (n = 1). MRSA nasal swab had a sensitivity of 62% (95% CI, 0.24-0.91), specificity of 98% (95% CI, 0.96-0.99), positive predictive value of 38% (95% CI, 0.21-0.6), and NPV of 99% (95% CI, 0.98-1).

CONCLUSIONS

A negative MRSA nasal swab has a 99% NPV for subsequent MRSA infections in AML patients with no prior history of MRSA colonization or infection. Based on these findings, a negative MRSA nasal swab can help guide de-escalation of empiric MRSA antibiotic therapy.

Methicillin-resistant Staphylococcus aureus (MRSA) screening upon inpatient hospital admission: Is there concordance between nasal swab results and samples taken from skin and soft tissue?

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) infections are associated with increased mortality and healthcare costs. In 2007, a Veterans' Affairs (VA) hospital implemented a MRSA nasal screening program, following a nationwide VA mandate, in an effort to reduce healthcare-associated MRSA infections.

OBJECTIVE

To evaluate the correlation between the nasal screening results for MRSA and culture results of wound and tissue sites.

METHODS

This retrospective study was conducted on inpatients at our VA hospital. Patients were included if they had undergone nasal screening for MRSA plus culture of a wound or tissue site within 30 days of hospital admission.

RESULTS

In total, 337 patients underwent nasal screening and wound culture and 211 underwent nasal screening and wound and tissue cultures. The prevalence of MRSA nasal colonization was 14.2% for wound samples and 15.2% for tissue samples. The sensitivities of MRSA nasal screening for detecting MRSA were 64.6% for wound cultures and 65.5% for tissue cultures. Specificities were 86.2% and 88.8% for wound and tissue cultures, respectively. The positive predictive values (PPVs) were 43.7% and 51.2% for wound and tissue cultures, respectively, and the negative predictive values (NPVs) were high at 93.6% and 93.5%, respectively.

CONCLUSIONS

In cases of wound or tissue samples for which culture results are pending, a negative MRSA nasal swab may be a component of the decision to withhold or discontinue MRSA-active agents.

Impact of Nasal Swabs on Empiric Treatment of Respiratory Tract Infections (INSERT-RTI)

Methicillin-resistant Staphylococcusaureus (MRSA) polymerase-chain-reaction nasal swabs (PCRNS) are a rapid diagnostic tool with a high negative predictive value. A PCRNS plus education “bundle” was implemented to inform clinicians on the utility of PCRNS for anti-MRSA therapy de-escalation in respiratory tract infections (RTI). The study included patients started on vancomycin with a PCRNS order three months before and after bundle implementation. The primary objective was the difference in duration of anti-MRSA therapy (DOT) for RTI. Secondary objectives included hospital length of stay (LOS), anti-MRSA therapy reinitiation, 30-day readmission, in-hospital mortality, and cost. We analyzed 62 of 110 patients screened, 20 in the preintervention and 42 in the postintervention arms. Mean DOT decreased after bundle implementation by 30.3 h (p = 0.039); mean DOT for patients with a negative PCRNS decreased by 39.7 h (p = 0.014). Median cost was lower after intervention [USD$51.69 versus USD$75.30 (p < 0.01)]. No significant difference in LOS, mortality, or readmission existed. The bundle implementation decreased vancomycin therapy and cost without negatively impacting patient outcomes.

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 Clinical Utility of Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Screening to Rule Out MRSA Pneumonia: A Diagnostic Meta-analysis With Antimicrobial Stewardship Implications

Background

Recent literature has highlighted methicillin-resistant Staphylococcus aureus (MRSA) nasal screening as a possible antimicrobial stewardship program tool for avoiding unnecessary empiric MRSA therapy for pneumonia, yet current guidelines recommend MRSA therapy based on risk factors. The objective of this meta-analysis was to evaluate the diagnostic value of MRSA nasal screening in MRSA pneumonia.

Methods

PubMed and EMBASE were searched from inception to November 2016 for English studies evaluating MRSA nasal screening and development of MRSA pneumonia. Data analysis was performed using a bivariate random-effects model to estimate pooled sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

Results

Twenty-two studies, comprising 5163 patients, met our inclusion criteria. The pooled sensitivity and specificity of MRSA nares screen for all MRSA pneumonia types were 70.9% and 90.3%, respectively. With a 10% prevalence of potential MRSA pneumonia, the calculated PPV was 44.8%, and the NPV was 96.5%. The pooled sensitivity and specificity for MRSA community-acquired pneumonia (CAP) and healthcare-associated pneumonia (HCAP) were 85% and 92.1%, respectively. For CAP and HCAP both the PPV and NPV increased, to 56.8% and 98.1%, respectively. In comparison, for MRSA ventilated-associated pneumonia, the sensitivity, specificity, PPV, and NPV were 40.3%, 93.7%, 35.7%, and 94.8%, respectively.

Conclusion

Nares screening for MRSA had a high specificity and NPV for ruling out MRSA pneumonia, particularly in cases of CAP/HCAP. Based on the NPV, MRSA nares screening is a valuable tool for AMS to streamline empiric antibiotic therapy, especially among patients with pneumonia who are not colonized with MRSA.

Systematic Review of the Clinical Utility of Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Screening for MRSA Pneumonia

Objective: To describe the diagnostic performance characteristics of methicillin-resistant Staphylococcus aureus (MRSA) nasal screening for patients with pneumonia. Data Sources: PubMed and Scopus were searched from 1 January 1990 to 12 December 2018 using terms methicillin-resistant Staphylococcus aureus AND (screening OR active surveillance OR surveillance culture OR targeted surveillance OR chromogenic OR PCR OR polymerase chain reaction OR rapid test) AND (nares OR nasal) AND (pneumonia OR respiratory). Study Selection and Data Extraction: Relevant studies in humans and English were considered. Data Synthesis: In all, 19 studies, including 21 790 patients, were included. Nasal screening for MRSA had a high negative predictive value (NPV; 76% to 99.4% for relevant studies) across all types of pneumonia. Time from nasal screening to culture varied across studies. Relevance to Patient Care and Clinical Practice: MRSA nasal screening has a high NPV for MRSA involvement in pneumonia. Utilizing this test for antimicrobial stewardship program (ASP) purposes can provide a valuable tool for reducing unwarranted anti-MRSA agents and may provide additional cost benefits. A cutoff of 7 days between nasal swab and culture or infection onset seems most appropriate for use of this test for anti-MRSA agent de-escalation for ASP purposes. Conclusions: Consideration for the inclusion of the utility of MRSA nasal screening in MRSA pneumonia should be made for future pneumonia and ASP guidelines. Additional studies are warranted to fully evaluate specific pneumonia classifications, culture types, culture timing, and clinical outcomes associated with the use of this test in patients with pneumonia.

MRSA colonization status as a predictor of clinical infection: A systematic review and meta-analysis

BACKGROUND

Vancomycin is often used as empiric therapy for methicillin-resistant Staphylococcus aureus (MRSA), but can be associated with clinically important adverse events including renal failure. MRSA colonization swabs are primarily used for infection control; their use as a diagnostic test to inform the decision to add empiric vancomycin therapy has not been well elucidated.

METHODS

We performed a Medline and Embase systematic review for peer-reviewed studies reporting the diagnostic accuracy of using MRSA colonization status to predict MRSA infections. Meta-analysis was performed using Cochrane guidelines. Grey literature was excluded.

FINDINGS

29 studies were included involving 24225 patients. In cases where the pathogen is not known to be S. aureus, specificities were greater than 85% for bacteremia, lower respiratory tract infections, skin and soft tissue infections (SSTI), and all infections pooled together. Sensitivities ranged between 54.0% and 77.5%. In cases where the pathogen is known to be S. aureus, we found studies on bacteremia and SSTI and arrived at pooled estimates of sensitivities ranging between 56.6% and 56.9%, and of specificities greater than 91%. Most importantly, for most infections in settings where the prevalence of MRSA as a causative organism is below 15%, the negative predictive value of a negative MRSA colonization swab exceeds 90%.

INTERPRETATIONS

In settings of low-moderate MRSA prevalence, negative MRSA screening swabs may prevent unnecessary vancomycin use. More research is needed to assess if this strategy can mitigate the cost of screening in areas with a low MRSA colonization rate.

Active identification of patients who are methicillin-resistant Staphylococcus aureus colonized is not associated with longer duration of vancomycin therapy

BACKGROUND

Excessive prescribing of vancomycin among patients admitted to inpatient wards is a challenge for antimicrobial stewardship programs, especially in the setting of expanded screening programs for methicillin-resistant Staphylococcus aureus (MRSA). Studies examining factors associated with longer duration of vancomycin use are limited.

METHODS

We conducted a retrospective cohort study to assess the impact of universal MRSA admission screening on duration of vancomycin use at the VA Boston Healthcare System during the period from January 2013-November 2015.

RESULTS

A total of 2,910 patients were administered intravenous vancomycin during the study period. A clinical culture positive for MRSA was strongly associated with vancomycin administration lasting >72 hours (odds ratio [OR], 2.72; 95% confidence interval [CI], 1.86-3.97; P < .001). After controlling for clinical culture results, admission MRSA colonization was not associated with vancomycin use past 72 hours (OR, 0.94; 95% CI, 0.8-1.1). A negative MRSA nasal swab on admission had a high negative predictive value for all MRSA infections evaluated (99.6% for pneumonia, 99.6% for bloodstream infection, and 98.1% for skin and soft tissue infection).

CONCLUSIONS

Admission surveillance for MRSA nasal colonization is not a major driver of prolonged vancomycin use. A negative admission MRSA nasal screen may be a useful tool for antimicrobial stewardship programs to limit vancomycin use, particularly in noncritically ill patients.

Forkhead box protein-3 (Foxp3)-producing dendritic cells suppress allergic response

BACKGROUND

The generation of the tolerogenic dendritic cells (DC) is not fully understood yet. Forkhead box protein-3 (Foxp3) is an important molecule in the immune tolerance. This study tests a hypothesis that DCs express Foxp3, which can be upregulated by Staphylococcal enterotoxin B (SEB).

METHODS

The expression of Foxp3 by DCs was evaluated by real-time RT-PCR, Western blotting, flow cytometry, and chromatin immunoprecipitation assay.

RESULTS

We observed that mice treated with SEB at 0.25-0.5 μg/mouse showed high frequencies of transforming growth factor (TGF)-β-producing CD4⁺ T cells and TGF-β-producing DCs in the intestine, while the IL-4⁺ CD4⁺ T cells and TIM4⁺ DCs were dominated in the intestine in mice treated with SEB at 1-10 μg/mouse. Treating DCs with SEB in the culture induced high levels of Foxp3 at the TGF-β promoter locus. The function of Foxp3 was blocked by STAT6 (signal transducer and activator transcription-6); the latter was induced by exposing DCs to SEB in the culture at doses of 100-400 ng/ml. Treating allergic mice with specific immunotherapy (SIT) together with SEB significantly promoted the therapeutic effects on the allergic responses than treating with SIT alone.

CONCLUSION

Dendritic cells have the capacity to express Foxp3, which can be upregulated by exposure to SEB.