5 Million Lives Campaign. Case study: an MRSA intervention at Evanston Northwestern Healthcare

Antimicrobial Stewardship Lessons From Mupirocin Use and Resistance in Methicillin-Resitant Staphylococcus Aureus

Background

The quantitative relationship between antimicrobial agent consumption and rise or fall of antibiotic resistance has rarely been studied. We began all admission surveillance testing for methicillin-resistant Staphylococcus aureus (MRSA) in August 2005 with subsequent contact isolation and decolonization using nasally applied mupirocin ointment for those colonized. In October 2012, we discontinued decolonization of medical (nonsurgical service) patients.

Methods

We conducted a retrospective study from 2007 through 2014 of 445680 patients; 35235 were assessed because of mupirocin therapy and positive test results for MRSA. We collected data on those patients receiving 2% mupirocin ointment for decolonization to determine the defined daily doses (DDDs). A nonparametric regression technique was used to quantitate the effect of mupirocin consumption on drug resistance in MRSA.

Results

Using regressive modeling, we found that, when consumption was consistently >25 DDD/1000 patient-days, there was a statistically significant increase in mupirocin resistance with a correlating positive rate of change. When consumption was ≤25 DDD/1000 patient-days, there was a statistically significant decrease in mupirocin resistance with a correlating negative rate of change. The scatter plot of fitted versus observed mupirocin resistance values showed an R² value of 0.89—a high correlation between mupirocin use and resistance.

Conclusions

Use of the antimicrobial agent mupirocin for decolonization had a threshold of approximately 25 DDD/1000 patient-days that separated a rise and fall of resistance within the acute-care setting. This has implications for how widely mupirocin can be used for decolonization, as well as for setting consumption thresholds when prescribing antimicrobials as part of stewardship programs.

Methicillin-Resistant Staphylococcus aureus Control in the 21st Century: Laboratory Involvement Affecting Disease Impact and Economic Benefit from Large Population Studies

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a global health care problem. Large studies (e.g., >25,000 patients) show that active surveillance testing (AST) followed by contact precautions for positive patients is an effective approach for MRSA disease control. With this approach, the clinical laboratory will be asked to select what AST method(s) to use and to provide data monitoring outcomes of the infection prevention interventions. This minireview summarizes evidence for MRSA disease control, reviews the involvement of the laboratory, and provides examples of how to undertake a program cost analysis. Health care organizations with total MRSA clinical infections of >0.3/1,000 patient days or bloodstream infections of >0.03/1,000 patient days should implement a MRSA control plan.

Amplification efficiency and thermal stability of qPCR instrumentation: Current landscape and future perspectives

Quantitative polymerase chain reaction (qPCR) is a method of amplifying and detecting small samples of genetic material in real time and is in routine use across many laboratories. Speed and thermal uniformity, two important factors in a qPCR test, are in direct conflict with one another in conventional peltier-driven thermal cyclers. To overcome this, companies are developing novel thermal systems for qPCR testing. More recently, qPCR technology has developed to enable its use in point-of-care testing (POCT), where the test is administered and results are obtained in a single visit to a health provider, particularly in developing countries. For a system to be suitable for POCT it must be rapid and reliable. In the present study, the speed and thermal uniformity of four qPCR thermal cyclers currently available were compared, two of which use the conventional peltier/block heating method and two of which use novel heating and cooling methods. The time required to complete 40 cycles varied between 12 and 58 min, and the C_t values were comparable, ranging between 13.6 and 16.8. Therefore, the novel technologies investigated in the present study for qPCR instrumentation performed equally well compared with conventional qPCR instruments, in terms of amplification efficiency and thermal uniformity.

Evaluation of BD Max StaphSR and BD Max MRSAXT Assays Using ESwab-Collected Specimens

The BD Max MRSAXT and the BD Max StaphSR assays were validated for the detection of methicillin-resistant Staphylococcus aureus (MRSA) in ESwab samples. In addition, the BD Max StaphSR assay was evaluated for its ability to detect and differentiate S. aureus and MRSA in the same sample. A total of 255 ESwab samples collected from the anterior nares of patients were tested by each of three BD Max assays, including the BD Max MRSA first-generation assay. The results were compared to those of direct and enrichment culture. Additionally, a challenge panel comprising 14 control strains was evaluated to determine the ability of these assays to correctly identify MRSA and also appropriately differentiate S. aureus by the BD Max StaphSR assay. Out of 255 clinical samples tested, 161 were negative and 30 were positive for MRSA, and 45 were positive for S. aureus (by BD Max StaphSR) and negative for MRSA by all three PCR assays and culture. Nineteen samples had discrepant results; all of them were retested by additional laboratory testing. All strains from the challenge panel were correctly identified or excluded by the BD Max MRSAXT and BD Max StaphSR assays. The results showed that the BD Max StaphSR and the BD MRSAXT assays have excellent sensitivity (94.3%) and specificity (97.7%) for detecting MRSA. The BD Max StaphSR assay demonstrated excellent sensitivity (96.4%) and specificity (93.6%) for detecting S. aureus.

Evaluation of multiple real-time PCR tests on nasal samples in a large MRSA surveillance program

OBJECTIVES

We evaluated the LightCycler MRSA Advanced Test (Roche Molecular Diagnostics, Pleasanton, CA), the BD MAX MRSA assay (Becton Dickinson, Franklin Lakes, NJ), and the Xpert MRSA assay (Cepheid, Sunnyvale, CA) on nasal samples using the same population.

METHODS

Admission and discharge nasal swabs were collected from inpatients using a double-headed swab. One swab was plated onto CHROMagar MRSA (CMA; Becton Dickinson, Sparks, MD) and then broken off into tryptic soy broth (TSB) for enrichment. TSB was incubated for 24 hours and then plated to CMA. The molecular tests were performed on the second swab. We analyzed the cost benefit of testing to evaluate what parameters affect hospital resources.

RESULTS

A total of 27,647 specimens were enrolled. The sensitivity/specificity was 98.3%/98.9% for the LightCycler MRSA Advanced Test and 95.7%/98.8% for the Xpert MRSA assay, but the difference was not significant. The positive predictive value was 86.7% for the LightCycler MRSA Advanced Test, 82.7% for the Xpert MRSA assay (P > .1), and 72.2% and for the BD MAX MRSA test (P < .001 compared with the LightCycler MRSA Advanced Test). All three assays were cost-effective, with the LightCycler MRSA Advanced Test having the highest economic return.

CONCLUSIONS

Our results suggest that the performance of the three commercial assays is similar. When assessing economic cost benefit of methicillin-resistant Staphylococcus aureus screening, the two measures with the most impact are the cost of the test and the specificity of the assay results.

Decolonisation of MRSA and its effect on surgical site infections--a study in a tertiary care institute

BACKGROUND

Two-thirds of surgical site infections (SSI) because of Staphylococcus aureus are caused by Methicillin resistant Staphylococcus aureus (MRSA). This study was done to assess the efficacy of topical 2% mupirocin with 2% chlorhexidine gluconate body wash in decolonizing MRSA and its impact in preventing SSI because of MRSA. The various risk factors associated with MRSA carriers and SSI were also studied because of paucity of data in the developing world.

METHODS

We did a non-randomised interventional trial in 602 patients undergoing elective general surgical operations. All patients in case (297) group were screened for MRSA and those positive were decolonised with topical 2% mupirocin calcium ointment and daily baths with 2% chlorhexidine antiseptic solution for 5 days. Control (305) group patients underwent surgery without decolonisation. Postoperatively, all patients were followed up for SSI for 30 days.

RESULTS

Prevalence of MRSA carriers was 7.5% with decolonisation rate of 95.2%. The SSI incidence was 21.3%. The significant risk factors for SSI were type of anaesthesia (p = 0.002), duration of surgery (p = 0.001) and preoperative hospital stay (p = 0.001). There was a significant association between MRSA carrier positivity at the time of surgery and SSI (p = 0.041).

CONCLUSIONS

There was no reduction in rate of SSI or other nosocomial infections in patients undergoing elective general surgical operations following preoperative MRSA decolonisation with 2% mupirocin and 2% chlorhexidine gluconate in MRSA carriers. MRSA carrier status was a significant risk factor for SSI but not for other nosocomial infections.

Assessment of the Influence of Test Characteristics on the Clinical and Cost Impacts of Methicillin-ResistantStaphylococcus aureusScreening Programs in US Hospitals

Objective.

To compare the impacts of different methicillin-resistantStaphylococcus aureus(MRSA) screening test options (eg, polymerase chain reaction [PCR], rapid culture) and program characteristics on the clinical outcomes and budget of a typical US hospital.

Methods.

We developed an Excel-based decision-analytic model, using published literature to calculate and compare hospital costs and MRSA infection rates for PCR- or culture-based MRSA screening and then used multivariate sensitivity analysis to evaluate key variables. Same-day PCR testing for a representative 370-bed teaching hospital in the United States was assessed in different populations (high-risk patients, intensive care unit [ICU] patients, or all patients) and compared with other test options.

Results.

Different screening program populations (all patients, high-risk patients, ICU patients, or patients with previous MRSA colonization or infection only) represented a potential savings of $12,158-$76,624 per month over no program ($188,618). Analysis of multiple test options in high-risk population screening indicated that same-day PCR testing of high-risk patients resulted in fewer infections over 1,720 patient-days (2.9, compared with 3.5 for culture on selective media and 3.8 for culture on nonselective media) and the lowest total cost ($112,012). The costs of other testing approaches ranged from $113,742 to $123,065. Sensitivity analysis revealed that variations in transmission rate, conversion to infection, prevalence increases, and hospital size are important to determine program impact. Among test characteristics, turnaround time is highly influential.

Conclusion.

All screening options showed reductions in infection rates and cost impact improvement over no screening program. Among the options, same-day PCR testing for high-risk patients slightly edges out the others in terms of fewest infections and greatest potential cost savings.

Laboratory evaluation of the BD MAX MRSA assay

A comparison between the BD MAX MRSA and Xpert MRSA assays was performed using 239 nares samples. A 97.9% overall agreement between the two molecular assays was observed. The BD MAX MRSA assay proved to be a reliable alternative for a highly automated system to detect methicillin-resistant Staphylococcus aureus (MRSA) in patient nares samples.

Staphylococcal phenotypes induced by naturally occurring and synthetic membrane-interactive polyphenolic β-lactam resistance modifiers

Galloyl catechins, in particular (-)-epicatechin gallate (ECg), have the capacity to abrogate β-lactam resistance in methicillin-resistant strains of Staphylococcus aureus (MRSA); they also prevent biofilm formation, reduce the secretion of a large proportion of the exoproteome and induce profound changes to cell morphology. Current evidence suggests that these reversible phenotypic traits result from their intercalation into the bacterial cytoplasmic membrane. We have endeavoured to potentiate the capacity of ECg to modify the MRSA phenotype by stepwise removal of hydroxyl groups from the B-ring pharmacophore and the A:C fused ring system of the naturally occurring molecule. ECg binds rapidly to the membrane, inducing up-regulation of genes responsible for protection against cell wall stress and maintenance of membrane integrity and function. Studies with artificial membranes modelled on the lipid composition of the staphylococcal bilayer indicated that ECg adopts a position deep within the lipid palisade, eliciting major alterations in the thermotropic behaviour of the bilayer. The non-galloylated homolog (-)-epicatechin enhanced ECg-mediated effects by facilitating entry of ECg molecules into the membrane. ECg analogs with unnatural B-ring hydroxylation patterns induced higher levels of gene expression and more profound changes to MRSA membrane fluidity than ECg but adopted a more superficial location within the bilayer. ECg possessed a high affinity for the positively charged staphylococcal membrane and induced changes to the biophysical properties of the bilayer that are likely to account for its capacity to disperse the cell wall biosynthetic machinery responsible for β-lactam resistance. The ability to enhance these properties by chemical modification of ECg raises the possibility that more potent analogs could be developed for clinical evaluation.

Predictors of methicillin-resistant Staphylococcus aureus colonization at hospital admission

BACKGROUND

The best strategy for active surveillance for methicillin-resistant Staphylococcus aureus (MRSA) remains unclear. We attempted to identify a risk factor score to predict MRSA colonization at hospital admission.

METHODS

Data on 9 variables reported as risk factors for MRSA colonization were analyzed, and a risk factor score to predict MRSA colonization was generated using multivariable logistic regression and receiver operating characteristic curve analyses. This risk score was then prospectively validated.

RESULTS

Four risk factors (nursing home residence, diabetes, hospitalization in the past year, and chronic skin condition/infection) were significantly associated with MRSA colonization (c-statistic = 0.846). A cut-off score of 8 or greater would result in screening 20% of admissions and would detect 71% of MRSA-colonized patients. In the prospective validation study, a cut-off score of 8 or greater required screening 21% of admissions and detected 54% of MRSA. Nursing home residence was the best predictor of MRSA colonization.

CONCLUSION

A similar risk factor-based screening strategy could be used to predict MRSA colonization in other institutions. Our data support routine screening of nursing home patients at hospital admission.

Detection of methicillin-resistant Staphylococcus aureus in healthcare workers using real-time polymerase chain reaction

Healthcare-associated infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have recently become an important issue for healthcare facilities due to high rates of infection, mortality, and high treatment costs. We investigated the frequency of MRSA in healthcare workers (HCWs) via nasal carriage and assessed the performance of the LightCycler® MRSA Advanced test. We tested nasal swabs from the anterior nares of participating HCWs at an intensive care unit. Nasal swabs were identified as S. aureus, methicillin-sensitive or methicillin-resistant coagulase-negative staphylococci (MSCoNS or MRCoNS), or MRSA by using conventional culture and the LightCycler® MRSA Advanced test. Of the 142 HCWs who participated in this study, only 11 participants (7.8%) were MRSA-positive by conventional culture and MRSA ID, and 24 (16.9%) were positive for mecA by real time polymerase chain reaction (PCR). In terms of diagnostic performance, the LightCycler® MRSA Advanced test had a sensitivity of 100%, a specificity of 90.1%, a positive predictive value of 45.8%, and a negative predictive value of 100% compared with conventional culture method. The detection limit of the LightCycler® MRSA Advanced test was 10(3) colony/mL. We concluded that real-time PCR was able to rapidly and sensitively detect MRSA in HCWs. However, MRSA must be confirmed by culture due to false positivity.

Detection of methicillin-resistant Staphylococcus aureus by a duplex droplet digital PCR assay

Health care-associated infections with methicillin-resistant Staphylococcus aureus (MRSA) contribute to significant hospitalization costs. We report here a droplet digital PCR (ddPCR) assay, which is a next-generation emulsion-based endpoint PCR assay for high-precision MRSA analysis. Reference cultures of MRSA, methicillin-susceptible S. aureus (MSSA), and confounders were included as controls. Copan swabs were used to sample cultures and collect specimens for analysis from patients at a large teaching hospital. Swab extraction and cell lysis were accomplished using magnetic-driven agitation of silica beads. Quantitative PCR (qPCR) (Roche Light Cycler 480) and ddPCR (Bio-Rad QX100 droplet digital PCR system) assays were used to detect genes for the staphylococcal protein SA0140 (SA) and the methicillin resistance (mecA) gene employing standard TaqMan chemistries. Both qPCR and ddPCR assays correctly identified culture controls for MRSA (76), MSSA (12), and confounder organisms (36) with 100% sensitivity and specificity. Analysis of the clinical samples (211 negative and 186 positive) collected during a study of MRSA nasal carriage allowed direct comparison of the qPCR and ddPCR assays to the Cepheid MRSA GeneXpert assay. A total of 397 clinical samples were examined in this study. Cepheid MRSA GeneXpert values were used to define negative and positive samples. Both the qPCR and ddPCR assays were in good agreement with the reference assay. The sensitivities for the qPCR and ddPCR assays were 96.8% (95% confidence interval [CI], 93.1 to 98.5%) and 96.8% (95% CI, 93.1 to 98.5%), respectively. Both the qPCR and ddPCR assays had specificities of 91.9% (95% CI, 87.5 to 94.9%) for qPCR and 91.0% (95% CI, 86.4 to 94.2%) for ddPCR technology.

Patient safety in the critical care environment

Improving the quality and safety of intensive care unit (ICU) care in the United States is a significant challenge for the future. Obtaining improvement in systems of care is difficult given the reactionary mode physicians tend to enter when dealing with moment-to-moment crises. It will be important to implement quality and safety measures that are already supported by evidence. Improvement of device safety will be critical to reducing the large number of device-related complications that occur in US ICUs. Prospective collection of adverse events with rigorous analysis will be important to allow systematic errors to be exposed and corrected.

Electronic surveillance for infectious disease trend analysis following a quality improvement intervention

OBJECTIVE

Interventions for reducing methicillin-resistant Staphylococcus aureus (MRSA) healthcare-associated disease require outcome assessment; this is typically done by manual chart review to determine infection, which can be labor intensive. The purpose of this study was to validate electronic tools for MRSA healthcare-associated infection (HAI) trending that can replace manual medical record review.

DESIGN AND SETTING

This was an observational study comparing manual medical record review with 3 electronic methods: raw culture data from the laboratory information system (LIS) in use by our healthcare organization, LIS data combined with admission-discharge-transfer (ADT) data to determine which cultures were healthcare associated (LIS + ADT), and the CareFusion MedMined Nosocomial Infection Marker (NIM). Each method was used for the same 7-year period from August 2003 through July 2010.

PATIENTS

The data set was from a 3-hospital organization covering 342,492 admissions.

RESULTS

Correlation coefficients for raw LIS, LIS + ADT, and NIM were 0.976, 0.957, and 0.953, respectively, when assessed on an annual basis. Quarterly performance for disease trending was also good, with R(2) values exceeding 0.7 for all methods.

CONCLUSIONS

The electronic tools accurately identified trends in MRSA HAI incidence density when all infections were combined as quarterly or annual data; the performance is excellent when annual assessment is done. These electronic surveillance systems can significantly reduce (93% [in-house-developed program] to more than 99.9999% [commercially available systems]) the personnel resources needed to monitor the impact of a disease control program.

Clinical effectiveness and cost benefit of universal versus targeted methicillin-resistant Staphylococcus aureus screening upon admission in hospitals

OBJECTIVE

To conduct an exploratory study to evaluate the clinical effectiveness and cost benefit of universal versus targeted screening for methicillin-resistant Staphylococcus aureus (MRSA) to prevent hospital-acquired MRSA infections.

DESIGN

Prospective, interventional study, using a case-control design, difference-in-differences, and cost-benefit analyses.

SETTING

Two community hospitals in Wisconsin.

PATIENTS

Consecutive sample of 15,049 adult admissions from April 2009 to July 2010.

INTERVENTIONS

MRSA surveillance performed by polymerase chain reaction (PCR) on samples collected from all adult patients (aged over 18 years) within 30 days before or upon an admission to the hospital. During a 9-month baseline period, targeted screening was conducted at both hospitals. During the 5-month intervention period, all patients admitted to the intervention hospital were screened for MRSA. Infection control measures were consistent at both hospitals.

RESULTS

Universal screening was associated with an increase in admission screening of 43.58 percentage points (P< .01), an increase in MRSA detection of 2.95 percentage points (P< .01), and a small, nonsignificant decline in hospital-acquired MRSA infections of 0.12 percentage points (P< .01). The benefit-to-cost ratio was 0.50, indicating that for every dollar spent on universal versus targeted screening, only $0.50 is recovered in avoided costs of hospital-acquired MRSA infection.

CONCLUSION

Compared with targeted screening, universal screening increased the rate of detection of MRSA upon hospital admission but did not significantly reduce the rate of hospital-acquired MRSA infection. Universal screening was associated with higher costs of care and was not cost beneficial.

Laboratory diagnosis of Clostridium difficile infection can molecular amplification methods move us out of uncertainty?

The laboratory diagnosis of Clostridium difficile infection (CDI) continues to be challenging. Recent guidelines from professional societies in the United States note that enzyme immunoassays for toxins A and B do not have adequate sensitivity to be used alone for detecting CDI, yet the optimal method for diagnosing this infection remains unclear. Nucleic acid amplification tests (NAATs) that target chromosomal toxin genes (usually the toxin B gene, tcdB) show high sensitivity and specificity, provide rapid results, and are amenable to both batch and on-demand testing, but these tests were not universally recommended for routine use in the recent guidelines. Rather, two-step algorithms that use glutamate dehydrogenase (GDH) assays to screen for C. difficile in stool specimens, followed by either direct cytotoxin testing or culture to identify toxin-producing C. difficile isolates, were recommended in one guideline and either GDH algorithms or NAATs were recommended in another guideline. Unfortunately, neither culture nor direct cytotoxin testing is widely available. In addition, this two-step approach requires 48 to 92 hours to complete, which may delay the initiation of therapy and critical infection control measures. Recent studies also show the sensitivity of several GDH assays to be <90%. This review considers the role of NAATs for diagnosing CDI and explores their potential advantages over two-step algorithms, including shorter time to results, while providing comparable, if not superior, accuracy.

Active surveillance culturing impacts methicillin-resistant Staphylococcus aureus acquisition in a pediatric intensive care unit

OBJECTIVE

To determine whether active surveillance culturing for methicillin-resistant Staphylococcus aureus (MRSA) decreases nosocomial MRSA acquisition in the pediatric intensive care unit.

DESIGN

Before and after observational study.

SETTING

A tertiary care, 20-bed, pediatric intensive care unit.

PATIENTS

All patients admitted to the pediatric intensive care unit.

INTERVENTIONS

Anterior nares cultures for MRSA were obtained on admission and weekly in the pediatric intensive care unit from January 2007 to December 2009 as part of a hospital quality improvement project.

MEASUREMENTS AND MAIN RESULTS

MRSA admission prevalence and nosocomial incidence density were determined retrospectively for 2006 and prospectively for 2007-2009. Nosocomial MRSA incidence density during the intervention period was determined monthly and analyzed by trend analysis by using a general linear model. The correlation of active surveillance culturing compliance with nosocomial acquisition of MRSA was analyzed. Possible confounding by healthcare worker hand hygiene compliance observed during the intervention period was also analyzed by multivariate linear regression analysis. The yearly MRSA incidence density significantly decreased from 2006 to 2009 (6.88 per 1,000 patient days to 1.45 per 1,000 patient days, p < .001) and from 2007 to 2009 (7.32 per 1,000 patient days to 1.45 per 1,000 patient days, p < .001). Trend analysis demonstrated a significant decline in MRSA acquisition over time following the introduction of active surveillance culturing (p < .001). Surveillance culturing was significantly associated with the decline in MRSA acquisition observed in the pediatric intensive care unit by multivariate regression analysis when controlling for hand hygiene (p = .01).

CONCLUSIONS

Active surveillance culturing resulted in significantly decreased nosocomial acquisition of MRSA in a pediatric intensive care unit setting. Admission and weekly active surveillance culturing appears to be an effective tool to decrease the spread of MRSA in the pediatric intensive care unit, independent of improvement in hand hygiene compliance. The impact on hospital-acquired MRSA infections and the cost benefit of active surveillance culturing require further study.

Molecular laboratory tests for the diagnosis of respiratory tract infection due to Staphylococcus aureus

When Staphylococcus aureus is the cause of ventilator-associated pneumonia or a bacterial infection following influenza, the infections are devastating if not treated promptly. Disease due to methicillin-resistant S. aureus (MRSA) continues to be of concern throughout most of the United States. Currently, the U.S. Food and Drug Administration (FDA) has cleared polymerase chain reaction tests for detection of MRSA in nasal swab specimens; however, there are no FDA-cleared tests for identifying S. aureus in purulent respiratory secretions. The real-time polymerase chain reaction tests for S. aureus (primarily MRSA) in nares provide results in <2 h and have sensitivities ranging from 95% to 100%, with specificities of 96%-99%; these results are comparable to that of standard cultures, which can take up to 3-4 days for final results. The FDA is encouraged to work closely with industry providers to expedite the evaluation and clearance process for molecular diagnostic devices detecting S. aureus (including MRSA) in the diagnosis of respiratory tract infection.

Performance of the BD GeneOhm MRSA achromopeptidase assay for real-time PCR detection of methicillin-resistant Staphylococcus aureus in nasal specimens

We evaluated the BD GeneOhm MRSA achromopeptidase (ACP) assay, which incorporates a new specimen preparation approach. A total of 1,216 leftover nasal samples were tested; using culture as the gold standard, the sensitivity and specificity were 92% and 94.6%, respectively. The new lysis method provides good sensitivity and simplifies specimen preparation.

Survey of employee knowledge and attitudes before and after a multicenter Veterans' Administration quality improvement initiative to reduce nosocomial methicillin-resistant Staphylococcus aureus infections

BACKGROUND

Although guidelines currently recommend prevention practices to decrease in-hospital transmission of infections, increasing adherence to the practices remains a challenge. This study assessed the effect of a multicenter methicillin-resistant Staphylococcus aureus (MRSA) prevention initiative on changes in employees' knowledge, attitudes, and practices.

METHODS

Two cross-sectional surveys were distributed at baseline (October 2006) and follow-up (July 2007) at 17 medical centers participating in the Veterans' Administration (VA) MRSA initiative.

RESULTS

Surveys were completed by 1362 employees at baseline and 952 employees at follow-up (representing 57% and 56% of eligible respondents, respectively). Respondents included physicians (9%), nurses (38%), allied health professionals (30%), and other support staff (24%). Of the 5 knowledge items, the mean proportion answered correctly increased slightly from baseline to follow-up (from 71% to 73%; P = .07). The percentage of respondents who believed that MRSA was a problem on their unit increased over time (from 56% to 65%; P < .001). Respondents also reported increased comfort with reminding other staff about proper hand hygiene (from 61% to 70%; P < .001) and contact precautions (from 63% to 70%; P < .002). The percentage of respondents reporting at least one barrier to proper hand hygiene decreased over time (from 25% to 20%; P = .003).

CONCLUSIONS

In this multicenter study of VA employees, implementation of a MRSA quality improvement initiative was associated with temporal improvements in knowledge and perceptions regarding MRSA prevention.

Multicenter evaluation of the LightCycler methicillin-resistant Staphylococcus aureus (MRSA) advanced test as a rapid method for detection of MRSA in nasal surveillance swabs

The rate of methicillin-resistant Staphylococcus aureus (MRSA) infection continues to rise in many health care settings. Rapid detection of MRSA colonization followed by appropriate isolation can reduce transmission and infection. We compared the performance of the new Roche LightCycler MRSA advanced test to that of the BD GeneOhm MRSA test and culture. Double-headed swabs were used to collect anterior nasal specimens from each subject. For both tests, DNA was extracted and real-time PCR was performed according to manufacturer's instructions. For culture, one swab of the pair was plated directly to CHROMagar MRSA. The swab paired with the BD GeneOhm MRSA test was also placed into an enrichment broth and then plated to CHROMagar MRSA. Colonies resembling staphylococci were confirmed as S. aureus by standard methods. Discrepant specimens had further testing with additional attempts to grow MRSA as well as sample amplicon sequencing. Agreement between results for the two swabs was 99.3% for those with valid results. A total of 1,402 specimens were tested using direct culture detection of MRSA as the gold standard; 187 were culture positive for MRSA. The LightCycler MRSA advanced test had relative sensitivity and specificity of 95.2% (95% confidence interval [CI]: 91.1% to 97.8%) and 96.4% (95% CI: 95.2% to 97.4%), respectively. The BD GeneOhm assay had relative sensitivity and specificity of 95.7% (95% CI: 91.7% to 98.1%) and 91.7% (95% CI: 90.0% to 93.2%), respectively. Following discrepancy analysis, the relative sensitivities of the LightCycler MRSA advanced test and the BD GeneOhm MRSA assay were 92.2 and 93.2%, respectively; relative specificities were 98.9 and 94.2%, respectively. Specificity was significantly better (P<0.001) with the LightCycler MRSA advanced test. The sensitivity of direct culture was 80.4%. The LightCycler MRSA advanced test is a useful tool for sensitive and rapid detection of MRSA nasal colonization.

To screen or not to screen for methicillin-resistant Staphylococcus aureus

There are few more compelling questions in clinical microbiology today than the issue of whether or not to screen for the presence of methicillin-resistant Staphylococcus aureus (MRSA), with the results being used to institute infection control interventions aimed at preventing transmission of MRSA in health care environments. Numerous different matters must be addressed when considering a screening program. Who is to be screened, what method is to be employed to detect MRSA, and what sites should be sampled? When and how often should the screening be performed? Who is going to pay for the screening, and, finally and perhaps most importantly, how are screening results to be communicated to health care providers and what kind of interventions are best undertaken based on the results? Numerous governmental agencies have mandated MRSA screening programs, and yet several authorities in infection control organizations have questioned the appropriateness of mandated screening. In this Point-Counterpoint feature, Dr. Lance Peterson of Evanston Hospital (Evanston, IL) offers his perspective on why screening for MRSA is to be encouraged. Dr. Daniel Diekema of the University of Iowa Carver College of Medicine (Iowa City, IA) offers an opposing view.

Comparison of the BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) PCR assay to culture by use of BBL CHROMagar MRSA for detection of MRSA in nasal surveillance cultures from intensive care unit patients

This study compared the BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) real-time PCR assay to culture by the use of BBL CHROMagar MRSA for the detection of MRSA in 627 nasal surveillance specimens collected from intensive care unit (ICU) patients. The PCR assay had a sensitivity, specificity, positive predictive value, and negative predictive value of 100%, 96.7%, 70.3%, and 100%, respectively. Nine of 19 false-positive PCR specimens grew methicillin-susceptible S. aureus (MSSA) from broth enrichment culture, of which two demonstrated evidence of mecA gene dropout. Compared to culture by the use of BBL CHROMagar MRSA, the BD GeneOhm MRSA PCR assay demonstrated sensitivity and specificity above 95% for the detection of MRSA nasal colonization and provided shorter turnaround time in generating positive and negative final results.

Implementation of a universal admission surveillance and decolonization program for methicillin-resistant staphylococcus aureus (MRSA) reduces the number of MRSA and total number of S. aureus isolates reported by the clinical laboratory

Our three-hospital system began active surveillance for methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization, with decolonization of positive patients, on all admissions starting 1 August 2005. A question not previously addressed is whether reduction of the incidence of MRSA disease would lower the total number of S. aureus clinical isolates recovered by the microbiology laboratory that are reported to health care providers. The decreases in the numbers of MRSA and total S. aureus clinical isolates for each year after August 2005 were highly statistically significant compared to the numbers in each of the prior 3 years (P < 0.0001).

Chromogenic media vs real-time PCR for nasal surveillance of methicillin-resistant Staphylococcus aureus: impact on detection of MRSA-positive persons

Surveillance for methicillin-resistant Staphylococcus aureus (MRSA) colonization can be an important element for infection control programs when managing a multidrug-resistant pathogen such as MRSA. The sensitivity and speed of laboratory testing affects the proportion of appropriate isolation days captured, which determines the success or failure of a MRSA control program. Chromogenic culture, CHROMagar MRSA (BBL, Becton Dickinson, Sparks, MD) and MRSASelect (Bio-Rad, Hercules, CA), with and without broth enrichment and real-time polymerase chain reaction (PCR; BD GeneOhm MRSA, BD Diagnostics, San Diego, CA), were compared and found to have a wide range of sensitivities (78.5%-98.2%), specificities (91.6%-100.0%), and turnaround times (2-72 hours). Real-time PCR provided the most rapid results and demonstrated the highest sensitivity followed by broth-enriched culture and then direct plating for MRSA detection in nasal swabs. There was no substantial difference in the labor required for any of the 3 approaches.

Molecular diagnostics of infectious diseases

PURPOSE OF REVIEW

The purpose of this article is to review the molecular methods commonly used in medical microbiology as well as to update the clinician as to newer molecular technologies that show promise in the identification of microorganisms as well as evaluation of the presence of virulence factors and antibiotic resistance determinants.

RECENT FINDINGS

Numerous molecular assays have been developed recently using a variety of technologies. Direct hybridization techniques have allowed analysis of blood culture bottles for organisms such as methicillin-resistant Staphylococcus aureus. Target amplification methods allow postamplification analysis using a variety of technologies depending on the clinical needs for the assay. Postamplification analysis includes methods such as Sanger sequencing, pyrosequencing, reverse hybridization, and Luminex analysis, which are becoming more widely utilized. In the future, whole genome sequencing, mass spectrometry, and microarray analysis may provide a wealth of information that can be used to specifically tailor the treatment of infectious diseases.

SUMMARY

The implications of current trends in molecular infectious diseases are moving towards high-throughput, simple, array-type technologies that will provide a wealth of data regarding types of organisms present in a sample and the virulence factors/resistance determinants that influence the severity of disease. As a result of these developments, infectious diseases will be more accurately and effectively treated.

Multicenter evaluation of the Cepheid Xpert methicillin-resistant Staphylococcus aureus (MRSA) test as a rapid screening method for detection of MRSA in nares

The first U.S. multicenter clinical trial to assess the performance of the Cepheid Xpert MRSA assay (Xpert MRSA) was conducted. The assay is a qualitative test designed for the rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) directly from nares swabs. This novel test combines integrated nucleic acid extraction and automated real-time PCR for the detection of a MRSA-specific signature sequence. A total of 1,077 nares specimens were collected from seven geographically distinct health care sites across the United States with prevalence rates ranging from 5.2% to 44%. Nares specimens were tested by (i) the Xpert MRSA assay, (ii) direct culture on CHROMagar MRSA medium (direct CM culture), and (iii) broth-enriched culture (Trypticase soy broth with 6.5% sodium chloride) followed by plating onto CHROMagar MRSA medium (broth-enriched CM culture). When direct CM culture was designated the reference method, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the Xpert MRSA assay were 94.3%, 93.2%, 73.0%, and 98.8%, respectively. When broth-enriched CM culture was used as the reference method, the clinical sensitivity, specificity, PPV, and NPV of the Xpert MRSA assay were 86.3%, 94.9%, 80.5%, and 96.6%, respectively. The BD GeneOhm MRSA (BDGO) assay was performed as a comparative molecular method. No statistical performance differences were observed between the Xpert MRSA and BDGO assays when they were compared to culture methods. From this large-scale, multicenter clinical comparison, we conclude that the Xpert MRSA assay is a simple, rapid, and accurate method for performing active surveillance for MRSA in a variety of health care populations.

Staphylococcus aureus nasal decolonization in joint replacement surgery reduces infection

Surgical site infections (SSIs) with Staphylococcus aureus are a recognized adverse event of hip and knee replacements. We evaluated the impact of a program to detect S. aureus nasal carriers before surgery with preoperative decolonization (using mupirocin twice daily for 5 days prior to surgery) of carriers. Nasal swab samples were obtained from patients prior to surgery from 8/1/2003 through 2/28/2005. Samples were tested using real-time PCR technology to detect S. aureus. The group that developed S. aureus SSI was compared to a combined concurrent and historical control for one year following the operation. S. aureus caused 71% of SSIs in the combined control groups. Of the 1495 surgical candidates evaluated, 912 (61.0%) were screened for S. aureus; 223 of those screened (24.5%) were positive and then decolonized with mupirocin. Among the 223 positive and decolonized patients, three (1.3%) developed a SSI. Among the 689 screen-negative patients, four (0.6%) developed SSIs for an overall rate of 0.77%. Among the 583 control patients who were not screened or decolonized, 10 (1.7%) developed S. aureus SSIs. SSIs from other organisms were 0.44% and 0.69%, respectively.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Optimization of a laboratory-developed test utilizing roche analyte-specific reagents for detection of Staphylococcus aureus, methicillin-resistant S. aureus, and vancomycin-resistant Enterococcus species

Nasal and perianal swab specimens were tested for detection of Staphylococcus aureus and vancomycin-resistant Enterococcus species (VRE) using a laboratory-developed real-time PCR test and microbiological cultures. The real-time PCR and culture results for S. aureus were similar. PCR had adequate sensitivity, but culture was more specific for the detection of VRE.

5 Million Lives Campaign. Reducing methicillin-resistant Staphylococcus aureus (MRSA) infections

BACKGROUND

Hospital-acquired infections from methicillin-resistant Staphylococcus aureus (MRSA) now account for more than 60% of S. aureus infections in intensive care patients reported to the Centers for Disease Control and Prevention (CDC). Media stories have raised the profile of this problem, and several states have moved toward legislative action regarding screening of hospital patients or mandatory reporting of infections. Guidelines from clinical expert organizations, including the CDC, the Association for Professionals in Infection Control and Epidemiology (APIC), and the Society for Healthcare Epidemiology of America (SHEA), recommend the use of basic prevention practices to avoid transmission in the hospital setting, yet concerns persist that compliance with these practices is neither consistent nor reliable.

INTERVENTION

The campaign's MRSA intervention recommends five key components of care. These are not intended to be an all-inclusive list but rather have been recommended by experts as the minimum necessary components: (1) hand hygiene, (2) decontamination of the environment and equipment, (3) active surveillance, (4) contact precautions for infected and colonized patients, and (5) device bundles (central line bundle and ventilator bundle).

CONCLUSION

The IHI's 5 Million Lives Campaign considers all hospital-acquired infections as harm to patients, and reduction of MRSA is one of the areas of focus.