Rapid diagnostic testing of methicillin-resistant Staphylococcus aureus carriage at different anatomical sites: costs and benefits of less extensive screening regimens

Trends in Molecular Diagnosis of Nosocomial Pneumonia Classic PCR vs. Point-of-Care PCR: A Narrative Review

Nosocomial pneumonia is one of the most frequent hospital-acquired infections. One of the types of nosocomial pneumonia is ventilator-associated pneumonia, which occurs in endotracheally intubated patients in intensive care units (ICU). Ventilator-associated pneumonia may be caused by multidrug-resistant pathogens, which increase the risk of complications due to the difficulty in treating them. Pneumonia is a respiratory disease that requires targeted antimicrobial treatment initiated as early as possible to have a good outcome. For the therapy to be as specific and started sooner, diagnostic methods have evolved rapidly, becoming quicker and simpler to perform. Polymerase chain reaction (PCR) is a rapid diagnostic technique with numerous advantages compared to classic plate culture-based techniques. Researchers continue to improve diagnostic methods; thus, the newest types of PCR can be performed at the bedside, in the ICU, so-called point of care testing-PCR (POC-PCR). The purpose of this review is to highlight the benefits and drawbacks of PCR-based techniques in managing nosocomial pneumonia.

Development and validation of a time and motion guide to assess the costs of prevention and control interventions for nosocomial infections: A Delphi method among experts

BACKGROUND

Nosocomial infections place a heavy burden on patients and healthcare providers and impact health care institutions financially. Reducing nosocomial infections requires an integrated program of prevention and control using key clinical best care practices. No instrument currently exists that measures these practices in terms of personnel time and material costs.

OBJECTIVE

To develop and validate an instrument that would measure nosocomial infection control and prevention best care practice costs, including estimates of human and material resources.

METHODS

An evaluation of the literature identified four practices essential for the control of pathogens: hand hygiene, hygiene and sanitation, screening and additional precaution. To reflect time, materials and products used in these practices, our team developed a time and motion guide. Iterations of the guide were assessed in a Delphi technique; content validity was established using the content validity index and reliability was assessed using Kruskall Wallis one-way ANOVA of rank test.

RESULTS

Two rounds of Delphi review were required; 88% of invited experts completed the assessment. The final version of the guide contains eight dimensions: Identification [83 items]; Personnel [5 items]; Additional Precautions [1 item]; Hand Hygiene [2 items]; Personal Protective Equipment [14 items]; Screening [4 items]; Cleaning and Disinfection of Patient Care Equipment [33 items]; and Hygiene and Sanitation [24 items]. The content validity index obtained for all dimensions was acceptable (> 80%). Experts statistically agreed on six of the eight dimensions.

DISCUSSION/CONCLUSION

This study developed and validated a new instrument based on expert opinion, the time and motion guide, for the systematic assessment of costs relating to the human and material resources used in nosocomial infection prevention and control. This guide will prove useful to measure the intensity of the application of prevention and control measures taken before, during and after outbreak periods or during pandemics such as COVID-19.

Economic analysis of healthcare-associated infection prevention and control interventions in medical and surgical units: systematic review using a discounting approach

Nosocomial or healthcare-associated infections (HCAIs) are associated with a financial burden that affects both patients and healthcare institutions worldwide. The clinical best care practices (CBPs) of hand hygiene, hygiene and sanitation, screening, and basic and additional precautions aim to reduce this burden. The COVID-19 pandemic has confirmed these four CBPs are critically important prevention practices that limit the spread of HCAIs. This paper conducted a systematic review of economic evaluations related to these four CBPs using a discounting approach. We searched for articles published between 2000 and 2019. We included economic evaluations of infection prevention and control of Clostridioides difficile-associated diarrhoea, meticillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and carbapenem-resistant Gram-negative bacilli. Results were analysed with cost-minimization, cost-effectiveness, cost-utility, cost-benefit and cost-consequence analyses. Articles were assessed for quality. A total of 11,898 articles were screened and seven were included. Most studies (4/7) were of overall moderate quality. All studies demonstrated cost effectiveness of CBPs. The average yearly net cost savings from the CBPs ranged from $252,847 (2019 Canadian dollars) to $1,691,823, depending on the rate of discount (3% and 8%). The average incremental benefit cost ratio of CBPs varied from 2.48 to 7.66. In order to make efficient use of resources and maximize health benefits, ongoing research in the economic evaluation of infection control should be carried out to support evidence-based healthcare policy decisions.

Performance of the Hologic Panther Fusion® MRSA Assay for the nasal screening of methicillin-sensitive and methicillin-resistant Staphylococcus aureus carriage

Staphylococcus aureus (SA) nasal carriage screening is usually based on either culture or molecular biology. The aim of the study was to evaluate the performance of the Panther Fusion® MRSA Assay (PF) that proposes a complete automation of the molecular screening for MSSA and MRSA carriage. Four hundred thirty-four nasal samples collected on ESwab™ were screened using PF. Results were compared with standard culture on BBL™ CHROMagar™ Staph aureus and chromID® MRSA agar. Discordant results were analyzed with additional techniques: Xpert SA Nasal Complete on GeneXpert (GX), culture on selective agar after 24 h in broth enrichment, and, if necessary, characterization of mec gene and SCCmec cassette using DNA microarray. The PF presented an overall agreement of 97.5% for SA detection and 97.9% for MRSA detection. Furthermore, 7.1% (31/434) of the samples were SA-negative in primary culture but SA-positive using PF and GX, confirming the greater sensitivity of molecular tests compared with culture. Of note, 4 out of 30 MRSA-positive samples were not detected due to an atypical SCCmec cassette, while 2 samples were falsely detected as MRSA due to co-colonization with a MSSA drop-out strain and a methicillin-resistant coagulase-negative staphylococcal strain. Considering all results, the PF instrument appears as a reliable and rapid (< 3 h) package for MSSA/MRSA nasal screening. This technology using random access capability and direct sampling of the primary container is innovative and corresponds therefore to a new step in complete molecular biology automation in bacteriology.

Emerging strategies for the noninvasive diagnosis of nosocomial pneumonia

Introduction: Hospital-acquired pneumonia is a common and therapeutically challenging diagnosis that can lead to severe sepsis, critical illness, and respiratory failure. In this review, we focus on efforts to enhance microbiological diagnosis of hospital-acquired pneumonia, including ventilator-associated pneumonia.

Areas covered: A systematic literature review was conducted by searching Medline from inception to December 2018, including hand-searching of the reference lists for additional studies. The search strategy comprised the following common search terms: hospital pneumonia OR nosocomial pneumonia OR noninvasive OR molecular diagnostic tests (OR point-of-care systems OR VOC [i.e. volatile organic compounds]) OR rapid (or simple or quick test), including brand names for the most common commercial tests.

Expert opinion: In recent years, the microbiological diagnosis of respiratory pathogens has improved significantly by the development and implementation of molecular diagnostic tests for pneumonia. Real-time polymerase chain reaction, hybridization, and mass spectrometry-based platforms dominate the scene, with microarray-based assays, multiplex polymerase chain reaction, and MALDI-TOF mass spectrometry capable of detecting the determinants of antimicrobial resistance (mainly β-lactamase genes). Introducing these assays into routine clinical practice for rapid identification of the causative microbes and their resistance patterns could transform the care of pneumonia, improving antimicrobial selection, de-escalation, and stewardship.

A Discrete Event Simulation Model of Patient Flow in a General Hospital Incorporating Infection Control Policy for Methicillin-Resistant Staphylococcus Aureus (MRSA) and Vancomycin-Resistant Enterococcus (VRE)

BACKGROUND

Hospitalized patients are assigned to available staffed beds based on patient acuity and services required. In hospitals with double-occupancy rooms, patients must be additionally matched by gender. Patients with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant Enterococcus (VRE) must be bedded in single-occupancy rooms or cohorted with other patients with similar MRSA/VRE flags.

METHODS

We developed a discrete event simulation (DES) model of patient flow through an acute care hospital. Patients are matched to beds based on acuity, service, gender, and known MRSA/VRE colonization. Outcomes included time to bed arrival, length of stay, patient-bed acuity mismatches, occupancy, idle beds, acuity-related transfers, rooms with discordant MRSA/VRE colonization, and transmission due to discordant colonization.

RESULTS

Observed outcomes were well-approximated by model-generated outcomes for time-to-bed arrival (6.7 v. 6.2 to 6.5 h) and length of stay (3.3 v. 2.9 to 3.0 days), with overlapping 90% coverage intervals. Patient-bed acuity mismatches, where patient acuity exceeded bed acuity and where patient acuity was lower than bed acuity, ranged from 0.6 to 0.9 and 8.6 to 11.1 mismatches per h, respectively. Values for observed occupancy, total idle beds, and acuity-related transfers compared favorably to model-predicted values (91% v. 86% to 87% occupancy, 15.1 v. 14.3 to 15.7 total idle beds, and 27.2 v. 22.6 to 23.7 transfers). Rooms with discordant colonization status and transmission due to discordance were modeled without an observed value for comparison. One-way and multi-way sensitivity analyses were performed for idle beds and rooms with discordant colonization.

CONCLUSIONS

We developed and validated a DES model of patient flow incorporating MRSA/VRE flags. The model allowed for quantification of the substantial impact of MRSA/VRE flags on hospital efficiency and potentially avoidable nosocomial transmission.

Nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) at a palliative care unit: A prospective single service analysis

BACKGROUND

The emergence of multidrug-resistant bacterial microorganisms is a particular challenge for the health care systems. Little is known about the occurrence of methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Gram-negative bacteria (MDRGNB) in patients of palliative care units (PCU).

AIM

The primary aim of this study was to determine the carriage of MRSA among patients of a PCU at a German University Hospital and to assess whether the positive cases would have been detected by a risk-factor-based screening-approach.

DESIGN

Between February 2014 and January 2015 patients from our PCU were tested for MRSA carriage within 48 hours following admission irrespective of pre-existing risk factors. In addition, risk factors for MRSA colonization were assessed. Samples from the nostrils and, if applicable, from pre-existing wounds were analysed by standardized culture-based laboratory techniques for the presence of MRSA and of other bacteria and fungi. Results from swabs taken prior to admission were also recorded if available.

RESULTS

297 out of 317 patients (93.7%) fulfilled one or more MRSA screening criteria. Swabs from 299 patients were tested. The detection rate was 2.1% for MRSA. All MRSA cases would have been detected by a risk-factor-based screening-approach. Considering the detected cases and the results from swabs taken prior to admission, 4.1% of the patients (n = 13) were diagnosed with MRSA and 4.1% with MDRGNB (n = 13), including two patients with MRSA and MDRGNB (0.6%). The rate of MRSA carriage in PCU patients (4.1%) was elevated compared to the rate seen in the general cohort of patients admitted to our University Hospital (2.7%).

CONCLUSIONS

PCU patients have an increased risk to carry MRSA compared to other hospitalized patients. Although a risk factor-based screening is likely to detect all MRSA carriers amongst PCU patients, we rather recommend a universal screening to avoid the extra effort to identify the few risk factor-negative patients (<7%). As we did not perform a systematic MDRGNB screening, further studies are needed to determine the true prevalence of MDRGNB amongst PCU patients.

Predicting Multidrug-Resistant Gram-Negative Bacterial Colonization and Associated Infection on Hospital Admission

OBJECTIVE

Isolation of multidrug-resistant gram-negative bacteria (MDR-GNB) from patients in the community has been increasingly observed. A prediction model for MDR-GNB colonization and infection risk stratification on hospital admission is needed to improve patient care.

METHODS

A 2-stage, prospective study was performed with 995 and 998 emergency department patients enrolled, respectively. MDR-GNB colonization was defined as isolates resistant to 3 or more classes of antibiotics, identified in either the surveillance or early (≤48 hours) clinical cultures.

RESULTS

A score-assigned MDR-GNB colonization prediction model was developed and validated using clinical and microbiological data from 995 patients enrolled in the first stage of the study; 122 of these patients (12.3%) were MDR-GNB colonized. We identified 5 independent predictors: age>70 years (odds ratio [OR], 1.84 [95% confidence interval (CI), 1.06–3.17]; 1 point), assigned point value in the model), residence in a long-term-care facility (OR, 3.64 [95% CI, 1.57–8.43); 3 points), history of cerebrovascular accidents (OR, 2.23 [95% CI, 1.24–4.01]; 2 points), hospitalization within 1 month (OR, 2.63 [95% CI, 1.39–4.96]; 2 points), and recent antibiotic exposure (OR, 2.18 [95% CI, 1.16–4.11]; 2 points). The model displayed good discrimination in the derivation and validation sets (area under ROC curve, 0.75 and 0.80, respectively) with the best cutoffs of<4 and ≥4 points for low- and high-risk MDR-GNB colonization, respectively. When applied to 998 patients in the second stage of the study, the model successfully stratified the risk of MDR-GNB infection during hospitalization between low- and high-risk groups (probability, 0.02 vs 0.12, respectively; log-rank test, P<.001).

CONCLUSION

A model was developed to optimize both the decision to initiate antimicrobial therapy and the infection control interventions to mitigate threats from MDR-GNB.

Infect Control Hosp Epidemiol 2017;38:1216–1225

Impact of rapid screening for discontinuation of methicillin-resistant Staphylococcus aureus contact precautions

BACKGROUND

A history of methicillin-resistant Staphylococcus aureus (MRSA) is a determinant of inpatient bed assignment.

METHODS

We assessed outcomes associated with rapid testing and discontinuation of MRSA contact precautions (CP) in a prospective cohort study of polymerase chain reaction (PCR)-based screening in the Emergency Department (ED) of Massachusetts General Hospital. Eligible patients had a history of MRSA and were assessed and enrolled if documented off antibiotics with activity against MRSA and screened for nasal colonization (subject visit). PCR-negative subjects had CP discontinued; the primary outcome was CP discontinuation. We identified semiprivate rooms in which a bed was vacant owing to the CP status of the study subject, calculated the hours of vacancy, and compared idle bed-hours by PCR results. Program costs were compared with predicted revenue.

RESULTS

There were 2864 eligible patients, and 648 (22.6%) subject visits were enrolled. Of these, 65.1% (422/648) were PCR-negative and had CP discontinued. PCR-negative subjects had fewer idle bed-hours compared with PCR-positive subjects (28.6 ± 25.2 vs 75.3 ± 70.5; P < .001). The expected revenues from occupied idle beds and averted CP costs ranged from $214,160 to $268,340, and exceeded the program costs.

CONCLUSION

A program of targeted PCR-based screening for clearance of MRSA colonization resulted in expected revenues and decreased CP costs that outweighed programmatic costs.

Carriage, Clinical Microbiology and Transmission of Staphylococcus aureus

Staphylococcus aureus is one of the most important bacterial pathogens in clinical practice and a major diagnostic focus for the routine microbiology laboratory. It is carried as a harmless commensal in up to two-thirds of the population at any one time predominantly not only in the anterior nares, but also in multiple other sites such as the groin, axilla, throat, perineum, vagina and rectum. It colonizes skin breach sites, such as ulcers and wounds, and causes superficial and deep skin and soft tissue infections and life-threatening deep seated infections particularly endocarditis and osteomyelitis. S. aureus is constantly evolving through mutation and uptake of mobile genetic elements that confer increasing resistance and virulence. Since the 1960s, hospitals have had to contend with emergence of methicillin-resistant S. aureus (MRSA) strains that spread better in hospitals than methicillin-susceptible S. aureus (MSSA) and are harder to treat. Since the 1980s, distinct community MRSA strains have also emerged that cause severe skin and respiratory infections. Conventional identification of MSSA and MRSA in the microbiology laboratory involves microscopy, culture and biochemical analysis that for most samples is straightforward but slow, taking at least 48 h. This delay has significant consequences for individual patient care and public health, through inadequate or excessive empiric antibiotic use, and failure to implement appropriate infection control measures for MRSA-colonized patients during those first 48 h. This unmet need has driven development of rapid molecular diagnostics that either complement or replace conventional culture techniques in the laboratory, or can be placed in the clinical environment as point-of-care (POC) devices. These new technologies provide results to clinicians anything from within an hour to 24 h, depending on sample and clinical setting, and should transform management of patients with S. aureus and other bacterial diseases; however, uptake is often slow due to the disruptive effect of new technologies, costs of transition and uncertainty of the optimal solution given successive advances. More evidence of the health economic, clinical and antimicrobial resistance benefit will help support introduction of these new technologies. Finally, preventing MRSA transmission has been a priority for healthcare organizations for many years. There have been significant recent reductions in transmission following local and national campaigns to re-enforce basic and heightened infection control interventions such as universal hand hygiene, barrier nursing, decolonization and isolation of MRSA-colonized patients detected through routine culture or screening policies. Developments in whole genome sequencing are providing greater insight into reservoirs and routes of transmission that should help better target interventions to ensure sustainable control of endemic strains and to identify and prevent emergence of new strains.

The Current State of Screening and Decolonization for the Prevention of Staphylococcus aureus Surgical Site Infection After Total Hip and Knee Arthroplasty

The most common pathogens in surgical site infections after total hip and knee arthroplasty are methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), and coagulase-negative staphylococci. Patients colonized with MSSA or MRSA have an increased risk for a staphylococcal infection at the site of a total hip or knee arthroplasty. Most colonized individuals who develop a staphylococcal infection at the site of a total hip or total knee arthroplasty have molecularly identical S. aureus isolates in their nares and wounds. Screening and nasal decolonization of S. aureus can potentially reduce the rates of staphylococcal surgical site infection after total hip and total knee arthroplasty.

Detailed contact data and the dissemination of Staphylococcus aureus in hospitals

Close proximity interactions (CPIs) measured by wireless electronic devices are increasingly used in epidemiological models. However, no evidence supports that electronically collected CPIs inform on the contacts leading to transmission. Here, we analyzed Staphylococcus aureus carriage and CPIs recorded simultaneously in a long-term care facility for 4 months in 329 patients and 261 healthcare workers to test this hypothesis. In the broad diversity of isolated S. aureus strains, 173 transmission events were observed between participants. The joint analysis of carriage and CPIs showed that CPI paths linking incident cases to other individuals carrying the same strain (i.e. possible infectors) had fewer intermediaries than predicted by chance (P < 0.001), a feature that simulations showed to be the signature of transmission along CPIs. Additional analyses revealed a higher dissemination risk between patients via healthcare workers than via other patients. In conclusion, S. aureus transmission was consistent with contacts defined by electronically collected CPIs, illustrating their potential as a tool to control hospital-acquired infections and help direct surveillance.

Recent advances in communication technologies allow monitoring high-resolution contact networks. Close proximity interactions (CPIs) measured by wireless sensors are increasingly used to inform contact networks for the dissemination of pathogens in computational models, although empirical justification is lacking. Here, we conducted a longitudinal prospective study for four months in a hospital, including both patients and healthcare workers (HCWs). High-resolution CPIs were recorded continuously, and participants undertook weekly nasal swabs to detect S. aureus carriage. We set out to test whether the contact network measured by CPIs supported observed transmission episodes. A simulation study was first conducted to choose a test statistic for the association of CPI paths with transmission, showing that CPI path length from transmitter to incident case was the most powerful. Then, we selected patients presenting incident S. aureus colonization in the data. We showed that CPI paths existed to carriers of the same strain, with path lengths significantly shorter than between random pairs of participants, in agreement with the transmission hypothesis. In-hospital contact networks measured by CPIs inform on opportunities for pathogen transmission. These could be used in surveillance systems to help prevent the spread of nosocomial pathogens.

Recurrent furunculosis caused by a community-acquired Staphylococcus aureus strain belonging to the USA300 clone

BACKGROUND

A 24-year-old female with recurrent skin and soft tissue infections (SSTI) was enrolled as part of a multicenter observational cohort study conducted by a practice-based research network (PBRN) on community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA).

METHODS

Strains were characterized by pulsed-field gel electrophoresis (PFGE), spa typing, and multilocus sequence typing. MRSA strains were analyzed for SCCmec type and the presence of the Panton-Valentine leukocidin (PVL) and arginine catabolic mobile element (ACME) using PCR.

RESULTS

In the first episode, S. aureus was recovered from the wound and inguinal folds; in the second, S. aureus was recovered from a lower abdomen furuncle, inguinal folds, and patellar fold. Molecular typing identified CA-MRSA clone USA300 in all samples as spa-type t008, ST8, SCCmecIVa, and a typical PFGE pattern. The strain carried virulence genes pvl and ACME type I. Five SSTI episodes were documented despite successful resolution by antibiotic treatment, with and without incision and drainage.

CONCLUSIONS

The source of the USA300 strain remains unknown. The isolate may represent a persistent strain capable of surviving extensive antibiotic pressure or a persistent environmental reservoir may be the source, possibly in the patient's household, from which bacteria were repeatedly introduced into the skin flora with subsequent infections.

"Bringing down the flag": removing the contact precautions label for non-hospitalized patients with prior methicillin-resistant Staphylococcus aureus infection or colonization

A policy consensus has not been reached regarding discontinuing contact precautions in patients with a history of methicillin-resistant Staphylococcus aureus (MRSA). We found that as many as 72% of outpatients flagged for past MRSA were no longer carriers, and a single nasal PCR test provided a reasonable negative predictive value for removing contact precautions.

Follow-up cultures for MRSA after eradication therapy: are three culture-sets enough?

OBJECTIVES

We compared the standard procedure of three MRSA follow-up culture sets to six to determine the number of recurrences detected between the third and sixth follow-up culture-set, and studied possible risk factors for MRSA recurrence.

METHODS

A retrospective carrier cohort (2005-2010) was studied. Data was collected on MRSA culture-sets, follow-up, risk factors and outcome (recurrences during follow-up). We compared outcome between three and six follow-up MRSA culture sets, between HCWs and patients groups for complicated or uncomplicated carriers, and between nose-throat carriers and other carriers.

RESULTS

Of 406 MRSA carriers, 179 had received eradication therapy and had a negative first follow-up MRSA culture-set. Between the third and sixth follow-up culture-set 54% (35/65) of total recurrences occurred. Over 88% of all recurrences were detected within two months. Combined nose and throat carriage OR 25.5 (1.6-419.1)) and intravascular lines (OR 13.6 (1.2-156.2)) were risk factors for early recurrence.

CONCLUSIONS

We recommend five culture-sets till one year after successful eradication therapy with a distinction between those at risk for early recurrence and HCWs who require frequent culturing in the beginning and those not at risk for early recurrence. This recommendation is a balance between the need for swift detection of MRSA recurrence and the patients' burden.

Impact of rapid molecular screening at hospital admission on nosocomial transmission of methicillin-resistant Staphylococcus aureus: cluster randomised trial

Design

Cluster randomised crossover trial with seven wards randomly allocated to intervention or control arm.

Setting

Medical and surgical wards of a university hospital with active MRSA control programme.

Participants

All patients hospitalized >48 h in study wards and screened for MRSA on admission and discharge Intervention: Rapid PCR-based screening test for MRSA compared with control screening test by enrichment culture using chromogenic agar.

Objective

We determined the benefit of PCR-detection versus culture-based detection of MRSA colonisation upon patient admission on early implementation of isolation precautions and reduction of hospital transmission of MRSA.

Main outcome

Cumulative rate of MRSA hospital acquisition of in patients screened negative on admission.

Randomization

The sequential order of inclusion of study wards in each arm was randomised by assigning a number to each ward and using a computer generated list of random numbers.

Findings

Of 3704 eligible patients, 67.8% were evaluable for the study. Compared with culture, PCR-screening reduced the median test reporting time from admission from 88 to 11 hours (p<0.001) and the median time from admission to isolation from 96 to 25 hours (p<0.001). MRSA acquisition was detected in 36 patients (3.2%) in the control arm and 34 (3.2%) in the intervention arm. The incidence density rate of hospital acquired MRSA was 2.82 and 2.57/1,000 exposed patient-days in the control and intervention arm, respectively (risk ratio 0.91 (95% confidence interval, 0.60–1.39). Poisson regression model adjusted for colonisation pressure, compliance with hand hygiene and antibiotic use indicated a RR 0.99 (95% CI, 0.69 to 1.44).

Interpretation

Universal PCR screening for MRSA on admission to medical and surgical wards in an endemic setting shortened the time to implement isolation precautions but did not reduce nosocomial acquisition of MRSA.

Trial registration

clinicaltrials.gov NCT00846105

All purulence is local - epidemiology and management of skin and soft tissue infections in three urban emergency departments

BACKGROUND

Skin and soft tissue infection (SSTIs) are commonly treated in emergency departments (EDs). While the precise role of antibiotics in treating SSTIs remains unclear, most SSTI patients receive empiric antibiotics, often targeted toward methicillin-resistant Staphylococcus aureus (MRSA). The goal of this study was to assess the efficiency with which ED clinicians targeted empiric therapy against MRSA, and to identify factors that may allow ED clinicians to safely target antibiotic use.

METHODS

We performed a retrospective analysis of patient visits for community-acquired SSTIs to three urban, academic EDs in one northeastern US city during the first quarter of 2010. We examined microbiologic patterns among cultured SSTIs, and relationships between clinical and demographic factors and management of SSTIs.

RESULTS

Antibiotics were prescribed to 86.1% of all patients. Though S. aureus (60% MRSA) was the most common pathogen cultured, antibiotic susceptibility differed between adult and pediatric patients. Susceptibility of S. aureus from ED SSTIs differed from published local antibiograms, with greater trimethoprim resistance and less fluoroquinolone resistance than seen in S. aureus from all hospital sources. Empiric antibiotics covered the resultant pathogen in 85.3% of cases, though coverage was frequently broader than necessary.

CONCLUSIONS

Though S. aureus remained the predominant pathogen in community-acquired SSTIs, ED clinicians did not accurately target therapy toward the causative pathogen. Incomplete local epidemiologic data may contribute to this degree of discordance. Future efforts should seek to identify when antibiotic use can be narrowed or withheld. Local, disease-specific antibiotic resistance patterns should be publicized with the goal of improving antibiotic stewardship.

Screening cultures for detection of methicillin-resistant Staphylococcus aureus in a population at high risk for MRSA colonisation: identification of optimal combinations of anatomical sites

This retrospective study analysed the diagnostic yield of single-site, two-site, and three-site anatomical surveillance cultures in a population of 4,769 patients at high risk for methicillin-resistant Staphylococcus aureus (MRSA) colonisation. Cultures of seven anatomical sites were used as the gold standard against which to measure the sensitivity of MRSA detection. Detection rates for the seven single-sites, 21 two-site, and 35 three-site combinations are presented. Single-site swabbing only detected 50.5% (nose) of total cases, while three-site surveillance achieved a 92% (groin + nose + throat) sensitivity of detection at best. It is recommended that at least three anatomical sites should be screened for MRSA colonisation in these high-risk patients.

Dutch guideline on the laboratory detection of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) has rapidly emerged worldwide, affecting both healthcare and community settings, and intensive livestock industry. The efficient control of MRSA strongly depends on its adequate laboratory detection. This guideline provides recommendations on the appropriate use of currently available diagnostic laboratory methods for the timely and accurate detection of MRSA in patients and healthcare workers. Herewith, it aims to standardise and improve the diagnostic laboratory procedures that are used for the detection of MRSA in Dutch medical microbiology laboratories.

Discontinuation of contact precautions for methicillin-resistant staphylococcus aureus: a randomized controlled trial comparing passive and active screening with culture and polymerase chain reaction

BACKGROUND

There have been no randomized controlled trials comparing active and passive screening for documenting clearance of colonization with methicillin-resistant Staphylococcus aureus (MRSA). We compared the efficacy of active and passive screening using both culture and commercial polymerase chain reaction (PCR) for documentation of MRSA clearance and discontinuation of MRSA contact precautions (CPs).

METHODS

Inpatients with a history of MRSA infection or colonization enrolled between December 2010 and September 2011 were randomized to either passive (nonintervention arm; n = 202; observation with local standard of care) or active screening (intervention arm; n = 405; study staff screened using culture and commercial PCR). The primary outcome was discontinuation of CPs by trial arm based on 3 negative cultures. In the intervention arm, sensitivity, specificity, and positive and negative predictive values of the first PCR were compared to cultures.

RESULTS

CPs were discontinued significantly more often (rate ratio [RR], 4.1; 95% confidence interval [CI], 2.3%-7.1%) in the intervention arm, including in an intent-to-screen analysis (RR, 2.6; 95% CI, 1.5%-4.7%). The first PCR, compared to 3 cultures, detected MRSA with a sensitivity of 93.9% (95% CI, 85.4%-97.6%), a specificity of 92.0% (95% CI, 85.9%-95.6%), a positive predictive value of 86.1% (95% CI, 75.9%-93.1%), and a negative predictive value of 96.6% (95% CI, 91.6%-99.1%).

CONCLUSIONS

Compared to passive screening using culture methods, active screening resulted in discontinuation of MRSA CPs at a significantly higher frequency. Active screening with a single PCR would significantly increase the completion of the screening process. Clinical Trials Registration. NCT01234831.

MRSA screening by the Xpert MRSA PCR assay: pooling samples of the nose, throat, and groin increases the sensitivity of detection without increasing the laboratory costs

The performance of the Xpert MRSA polymerase chain reaction (PCR) assay on pooled nose, groin, and throat swabs (three nylon flocked eSwabs into one tube) was compared to culture by analyzing 5,546 samples. The sensitivity [0.78, 95 % confidence interval (CI) 0.73-0.82] and specificity (0.99, 95 % CI 0.98-0.99) were similar to the results from published studies on separated nose or other specimens. Thus, the performance of the Xpert MRSA assay was not affected by pooling the three specimens into one assay, allowing a higher detection rate without increasing laboratory costs, as compared to nose samples alone.

Costs and benefits of rapid screening of methicillin-resistant Staphylococcus aureus carriage in intensive care units: a prospective multicenter study

INTRODUCTION

Pre-emptive isolation of suspected methicillin-resistant Staphylococcus aureus (MRSA) carriers is a cornerstone of successful MRSA control policies. Implementation of such strategies is hampered when using conventional cultures with diagnostic delays of three to five days, as many non-carriers remain unnecessarily isolated. Rapid diagnostic testing (RDT) reduces the amount of unnecessary isolation days, but costs and benefits have not been accurately determined in intensive care units (ICUs).

METHODS

Embedded in a multi-center hospital-wide study in 12 Dutch hospitals we quantified cost per isolation day avoided using RDT for MRSA, added to conventional cultures, in ICUs. BD GeneOhm™ MRSA PCR (IDI) and Xpert MRSA (GeneXpert) were subsequently used during 17 and 14 months, and their test characteristics were calculated with conventional culture results as reference. We calculated the number of pre-emptive isolation days avoided and incremental costs of adding RDT.

RESULTS

A total of 163 patients at risk for MRSA carriage were screened and MRSA prevalence was 3.1% (n=5). Duration of isolation was 27.6 and 21.4 hours with IDI and GeneXpert, respectively, and would have been 96.0 hours when based on conventional cultures. The negative predictive value was 100% for both tests. Numbers of isolation days were reduced by 44.3% with PCR-based screening at the additional costs of €327.84 (IDI) and €252.14 (GeneXpert) per patient screened. Costs per isolation day avoided were €136.04 (IDI) and €121.76 (GeneXpert).

CONCLUSIONS

In a low endemic setting for MRSA, RDT safely reduced the number of unnecessary isolation days on ICUs by 44%, at the costs of €121.76 to €136.04 per isolation day avoided.

Methicillin-resistant Staphylococcus aureus carriage at ICU admission: to screen (rapidly) or not to screen?

The study by Wassenberg and colleagues shows that rapid diagnostic testing, although not cost-saving, reduces the number of unnecessary isolation days at ICU admission. Here, the strengths and limitations and the usefulness of rapid diagnostic testing are discussed from the collective and individual perspectives.