Colonization with methicillin-resistant Staphylococcus aureus in ICU patients: morbidity, mortality, and glycopeptide use

Timing of antibiotic therapy in the ICU

Severe or life threatening infections are common among patients in the intensive care unit (ICU). Most infections in the ICU are bacterial or fungal in origin and require antimicrobial therapy for clinical resolution. Antibiotics are the cornerstone of therapy for infected critically ill patients. However, antibiotics are often not optimally administered resulting in less favorable patient outcomes including greater mortality. The timing of antibiotics in patients with life threatening infections including sepsis and septic shock is now recognized as one of the most important determinants of survival for this population. Individuals who have a delay in the administration of antibiotic therapy for serious infections can have a doubling or more in their mortality. Additionally, the timing of an appropriate antibiotic regimen, one that is active against the offending pathogens based on in vitro susceptibility, also influences survival. Thus not only is early empiric antibiotic administration important but the selection of those agents is crucial as well. The duration of antibiotic infusions, especially for β-lactams, can also influence antibiotic efficacy by increasing antimicrobial drug exposure for the offending pathogen. However, due to mounting antibiotic resistance, aggressive antimicrobial de-escalation based on microbiology results is necessary to counterbalance the pressures of early broad-spectrum antibiotic therapy. In this review, we examine time related variables impacting antibiotic optimization as it relates to the treatment of life threatening infections in the ICU. In addition to highlighting the importance of antibiotic timing in the ICU we hope to provide an approach to antimicrobials that also minimizes the unnecessary use of these agents. Such approaches will increasingly be linked to advances in molecular microbiology testing and artificial intelligence/machine learning. Such advances should help identify patients needing empiric antibiotic therapy at an earlier time point as well as the specific antibiotics required in order to avoid unnecessary administration of broad-spectrum antibiotics.

Staphylococcal Biofilms: Challenges and Novel Therapeutic Perspectives

Staphylococci, like Staphylococcus aureus and S. epidermidis, are common colonizers of the human microbiota. While being harmless in many cases, many virulence factors result in them being opportunistic pathogens and one of the major causes of hospital-acquired infections worldwide. One of these virulence factors is the ability to form biofilms-three-dimensional communities of microorganisms embedded in an extracellular polymeric matrix (EPS). The EPS is composed of polysaccharides, proteins and extracellular DNA, and is finely regulated in response to environmental conditions. This structured environment protects the embedded bacteria from the human immune system and decreases their susceptibility to antimicrobials, making infections caused by staphylococci particularly difficult to treat. With the rise of antibiotic-resistant staphylococci, together with difficulty in removing biofilms, there is a great need for new treatment strategies. The purpose of this review is to provide an overview of our current knowledge of the stages of biofilm development and what difficulties may arise when trying to eradicate staphylococcal biofilms. Furthermore, we look into promising targets and therapeutic methods, including bacteriocins and phage-derived antibiofilm approaches.

Bacterial Anti-adhesives: Inhibition of Staphylococcus aureus Nasal Colonization

Bacterial adhesion to the skin and mucosa is often a fundamental and early step in host colonization, the establishment of bacterial infections, and pathology. This process is facilitated by adhesins on the surface of the bacterial cell that recognize host cell molecules. Interfering with bacterial host cell adhesion, so-called anti-adhesive therapeutics, offers promise for the development of novel approaches to control bacterial infections. In this review, we focus on the discovery of anti-adhesives targeting the high priority pathogen Staphylococcus aureus. This organism remains a major clinical burden, and S. aureus nasal colonization is associated with poor clinical outcomes. We describe the molecular basis of nasal colonization and highlight potentially efficacious targets for the development of novel nasal decolonization strategies.

The impact of a multimodal approach to vancomycin discontinuation in hematopoietic stem cell transplant recipients (HSCT) with febrile neutropenia (FN)

BACKGROUND

Current guidelines recommend adding vancomycin to empiric treatment of FN in patients who meet specific criteria. After 48 hours, the guidelines recommend discontinuing vancomycin if resistant Gram-positive organisms are not identified. Based on these recommendations, a vancomycin stewardship team defined criteria for discontinuation of vancomycin at 48 hours and increased surveillance of vancomycin usage through a multimodal approach. The purpose of this retrospective analysis is to assess the impact of this multimodal approach on the discontinuation of empiric vancomycin at 48 hours in FN.

METHODS

This retrospective analysis included a pre- and post-intervention cohort of 200 HSCT recipients with FN from 2015 to 2018. Criteria for continued vancomycin use beyond 48 hours included culture-documented resistant Gram-positive infection, positive Methicillin-Resistant S aureus (MRSA) nasal swab with evidence of pneumonia, or hemodynamic instability with concern for sepsis. The following patient characteristics were collected: previous MRSA infection, MRSA nasal swab collection and results, culture results, duration of vancomycin use, rationale for continuation of vancomycin beyond 48 hours, and re-initiation of vancomycin.

RESULTS

In the post-intervention cohort, vancomycin discontinuation at 48 hours increased from 31% (95% CI 21.94-40.05) to 70% (95% CI 61.02-78.97; P < 0.0001). An additional 23% of vancomycin orders were discontinued at 72 hours. Off criteria vancomycin use decreased from 33% in pre to 1% in the post-implementation cohort.

CONCLUSION

Establishing define criteria for vancomycin use in FN patients with a multimodal approach of physicians from hematology and infectious diseases, clinical pharmacists and the antibiotic stewardship team significantly improved vancomycin discontinuation.

Staphylococcus aureus Nasal Colonization: An Update on Mechanisms, Epidemiology, Risk Factors, and Subsequent Infections

Up to 30% of the human population are asymptomatically and permanently colonized with nasal Staphylococcus aureus. To successfully colonize human nares, S. aureus needs to establish solid interactions with human nasal epithelial cells and overcome host defense mechanisms. However, some factors like bacterial interactions in the human nose can influence S. aureus colonization and sometimes prevent colonization. On the other hand, certain host characteristics and environmental factors can predispose to colonization. Nasal colonization can cause opportunistic and sometimes life-threatening infections such as surgical site infections or other infections in non-surgical patients that increase morbidity, mortality as well as healthcare costs.

Factors associated with bacteraemia due to multidrug-resistant organisms among bacteraemic patients with multidrug-resistant organism carriage: a case control study

Background

Infections caused by multidrug-resistant organisms (MDRO) are emerging worldwide. Physicians are increasingly faced with the question of whether patients need empiric antibiotic treatment covering these pathogens. This question is especially essential among MDRO carriers. We aim to determine the occurrence of MDRO bacteraemia among bacteraemic patients colonized with MDRO, and the associated factors with MDRO bacteraemia among this population.

Methods

We performed a retrospective monocentric study among MDRO carriers hospitalized with bacteraemia between January 2013 and August 2016 in a French hospital. We compared characteristics of patients with MDRO and non-MDRO bacteraemia.

Results

Overall, 368 episodes of bacteraemia were reviewed; 98/368 (26.6%) occurred among MDRO carriers.

Main colonizing bacteria were extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (40/98; 40.8%), ESBL-producing Klebsiella pneumoniae (35/98; 35.7%); methicillin-resistant Staphylococcus aureus (26/98; 26.5%) and multidrug-resistant Pseudomonas aeruginosa (PA) (12/98; 12.2%).

There was no significant difference considering population with MDRO bacteraemia vs. non-MDRO bacteraemia, except for immunosuppression [OR 2.86; p = 0.0207], severity of the episode [OR 3.13; p = 0.0232], carriage of PA [OR 5.24; p = 0.0395], and hospital-acquired infection [OR 2.49; p = 0.034].

In the multivariate analysis, factors significantly associated with MDRO bacteraemia among colonized patient were only immunosuppression [OR = 2.96; p = 0.0354] and the hospital-acquired origin of bacteraemia [OR = 2.62; p = 0.0427].

Conclusions

According to our study, occurrence of bacteraemia due to MDRO among MDRO carriers was high. Factors associated with MDRO bacteraemia were severity of the episode and hospital-acquired origin of the bacteraemia. Thus, during bacteraemia among patients colonized with MDRO, if such characteristics are present, broad-spectrum antimicrobial treatment is recommended.

Pathogen colonization of the gastrointestinal microbiome at intensive care unit admission and risk for subsequent death or infection

PURPOSE

Loss of colonization resistance within the gastrointestinal microbiome facilitates the expansion of pathogens and has been associated with death and infection in select populations. We tested whether gut microbiome features at the time of intensive care unit (ICU) admission predict death or infection.

METHODS

This was a prospective cohort study of medical ICU adults. Rectal surveillance swabs were performed at admission, selectively cultured for vancomycin-resistant Enterococcus (VRE), and assessed using 16S rRNA gene sequencing. Patients were followed for 30 days for death or culture-proven bacterial infection.

RESULTS

Of 301 patients, 123 (41%) developed culture-proven infections and 76 (25%) died. Fecal biodiversity (Shannon index) did not differ based on death or infection (p = 0.49). The presence of specific pathogens at ICU admission was associated with subsequent infection with the same organism for Escherichia coli, Pseudomonas spp., Klebsiella spp., and Clostridium difficile, and VRE at admission was associated with subsequent Enterococcus infection. In a multivariable model adjusting for severity of illness, VRE colonization and Enterococcus domination (≥ 30% 16S reads) were both associated with death or all-cause infection (aHR 1.46, 95% CI 1.06-2.00 and aHR 1.47, 95% CI 1.00-2.19, respectively); among patients without VRE colonization, Enterococcus domination was associated with excess risk of death or infection (aHR 2.13, 95% CI 1.06-4.29).

CONCLUSIONS

Enterococcus status at ICU admission was associated with risk for death or all-cause infection, and rectal carriage of common ICU pathogens predicted specific infections. The gastrointestinal microbiome may have a role in risk stratification and early diagnosis of ICU infections.

Methicillin-resistant Staphylococcus aureus nasal colonization and infection in an intensive care unit of a university hospital in China

Objective This study was performed to determine the prevalence and risk factors associated with nasal methicillin-resistant Staphylococcus aureus (MRSA) colonization upon intensive care unit (ICU) admission and during the ICU stay in mainland China. Methods A prospective observational study was performed in a 50-bed general ICU of a 4300-bed teaching hospital in China from 2011 to 2013. Nasal swabs for MRSA detection were obtained upon ICU admission and at discharge for patients having stayed in the ICU for longer than 3 days. Results In total, 115 patients (4.1%; 95% confidence interval [CI], 3.4-4.9) were already colonized with MRSA on ICU admission, and another 185 patients (10.7%; 95% CI, 9.3-12.2) acquired MRSA during their ICU stay. Development of an MRSA infection was significantly more likely in patients with than without MRSA colonization on ICU admission (odds ratio [OR], 2.8; 95% CI, 1.1-7.3). Patients who acquired MRSA had significantly prolonged lengths of stay in the ICU (23.3 days) and higher hospital bills (135,171 RMB; about 19,590 USD) than those who tested negative for MRSA. Conclusion The MRSA colonization rate among ICU patients in mainland China is high. Patients with MRSA-positive nasal swabs are more likely to develop MRSA infections.

Risk of Surgical Site Infection in Elective Hip and Knee Replacements After Confirmed Eradication of MRSA in Chronic Carriers

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is globally endemic and is a leading cause of surgical site infection (SSI). The purpose of this study was to evaluate the incidence of SSI in MRSA carriers undergoing elective hip or knee arthroplasty, who had confirmed eradication and to compare it with incidence of SSI in non-MRSA carriers.

METHODS

This is a retrospective analysis of 6613 patients who underwent elective total hip arthroplasty (THA; n = 3347) and total knee arthroplasty (TKA; n = 3266) at our institution. A cohort of patients who were preoperatively colonized with MRSA was identified. We compared the infection rates with non-MRSA carriers.

RESULTS

We had a colonization rate of 1.3% (83 patients). A total of 79 patients had confirmed eradication of carrier status before surgical intervention. Of these, 38 were THAs and 41 were TKAs. Five of 79 patients (6.32%; 95% confidence interval [CI]: 2.35%-14.79%) had "deep SSI" within 1 year of surgery. There were 2 MRSA infections in THAs (relative risk 4.46; 95% CI: 1.12-17.82). There were 2 MRSA and 1 methicillin-sensitive Staphylococcus aureus infections in TKAs (relative risk 5.61; 95% CI: 1.81-17.38). A significant statistical difference in infection rates from MRSA negative control group was noted, which had a deep sepsis rate of 1.17% in THAs and 1.3% in TKAs over the same period.

CONCLUSION

In spite of a selective treatment program for carriers and confirmed eradication, there is still a significantly increased risk of SSI in MRSA-colonized patients undergoing hip or knee arthroplasties.

Impact of Probiotics for Reducing Infections in Veterans (IMPROVE): Study protocol for a double-blind, randomized controlled trial to reduce carriage of Staphylococcus aureus

BACKGROUND

Staphylococcus aureus (S. aureus) is an organism of great public health importance, causing 20,000 deaths annually. Decolonization of patients with S. aureus may prevent infections, yet current options are limited to antimicrobials that promote antibiotic resistance and can cause adverse side effects. Probiotics have potential to reduce colonization of pathogenic bacteria, representing a promising alternative for S. aureus decolonization, but thus far lack rigorous evaluation.

METHODS

Potential subjects were recruited from inpatient and outpatient settings within a VA medical center and screened for S. aureus gastrointestinal (GI) or extra-GI colonization using swabs at multiple body sites. Positive, eligible, consenting participants were stratified by colonization site and randomized in a 1:1 ratio to 4-weeks of daily placebo or Lactobacillus rhamnosus (L. rhamnosus) HN001 probiotic treatment. Blood and stool samples, and treatment adherence reports were collected from each subject throughout the study, along with a final set of swabs at study completion to detect S. aureus carriage. The outcomes of this study are GI or extra-GI carriage by S. aureus at the end of 4weeks of therapy, change in phagocytic activity of polymorphonuclear cells from pre-intervention to post-intervention, and symptomatic S. aureus infection at any site during the study period.

CONCLUSION

114 participants have been recruited for this study. Analysis of outcomes is underway. This is the first clinical trial to examine the efficacy of L. rhamnosus HN001 for decolonization of S. aureus, and investigates the mechanism by which L. rhamnosus HN001 mediates its effect on S. aureus colonization. ClinicalTrials.govIdentifier NCT01321606.

Strategies to Prevent Methicillin-ResistantStaphylococcus aureusTransmission and Infection in Acute Care Hospitals: 2014 Update

Previously published guidelines are available that provide comprehensive recommendations for detecting and preventing healthcare-associated infections (HAIs). The intent of this document is to highlight practical recommendations in a concise format designed to assist acute care hospitals in implementing and prioritizing their methicillin-resistantStaphylococcus aureus(MRSA) prevention efforts. This document updates “Strategies to Prevent Transmission of Methicillin-ResistantStaphylococcus aureusin Acute Care Hospitals,” published in 2008. This expert guidance document is sponsored by the Society for Healthcare Epidemiology of America (SHEA) and is the product of a collaborative effort led by SHEA, the Infectious Diseases Society of America (IDSA), the American Hospital Association (AHA), the Association for Professionals in Infection Control and Epidemiology (APIC), and The Joint Commission, with major contributions from representatives of a number of organizations and societies with content expertise. The list of endorsing and supporting organizations is presented in the introduction to the 2014 updates.

Economic Analysis of Veterans Affairs Initiative to Prevent Methicillin-Resistant Staphylococcus aureus Infections

INTRODUCTION

In an effort to reduce methicillin-resistant Staphylococcus aureus (MRSA) transmission through universal screening and isolation, the Department of Veterans Affairs (VA) launched the National MRSA Prevention Initiative in October 2007. The objective of this analysis was to quantify the budget impact and cost effectiveness of this initiative.

METHODS

An economic model was developed using published data on MRSA hospital-acquired infection (HAI) rates in the VA from October 2007 to September 2010; estimates of the costs of MRSA HAIs in the VA; and estimates of the intervention costs, including salaries of staff members hired to support the initiative at each VA facility. To estimate the rate of MRSA HAIs that would have occurred if the initiative had not been implemented, two different assumptions were made: no change and a downward temporal trend. Effectiveness was measured in life-years gained.

RESULTS

The initiative resulted in an estimated 1,466-2,176 fewer MRSA HAIs. The initiative itself was estimated to cost $207 million during this 3-year period, while the cost savings from prevented MRSA HAIs ranged from $27 million to $75 million. The incremental cost-effectiveness ratios ranged from $28,048 to $56,944/life-years. The overall impact on the VA's budget was $131-$179 million.

CONCLUSIONS

Wide-scale implementation of a national MRSA surveillance and prevention strategy in VA inpatient settings may have prevented a substantial number of MRSA HAIs. Although the savings associated with prevented infections helped offset some but not all of the cost of the initiative, this model indicated that the initiative would be considered cost effective.

Risk Factors of Methicillin-Resistant Staphylococcus aureus Infection and Correlation With Nasal Colonization Based on Molecular Genotyping in Medical Intensive Care Units: A Prospective Observational Study

Methicillin-resistant Staphylococcus aureus (MRSA) is a common and important cause of colonization and infection in medical intensive care units (ICU). The aim of this study was to assess association factors between MRSA nasal colonization and subsequent infections in medical ICU patients by clinical investigation and molecular genotyping. A prospective cohort observational analysis of consecutive patients admitted to medical ICUs between November 2008 and May 2010 at a tertiary teaching hospital were included. To detect MRSA colonization, the specimens from the nares were obtained within 3 days of admission to the ICU and again 1 week following admission to the ICU. Genetic relatedness for colonized and clinical isolates from each study patient with MRSA infection were analyzed and compared. A total of 1266 patients were enrolled after excluding 195 patients with already present MRSA infections. Subsequent MRSA infection rates were higher in patients with nasal colonization than in those without (39.1% versus 14.7%, respectively). Multivariate Poisson regression analysis demonstrated that nasal MRSA colonization (relative risk [RR]: 2.50; 95% confidence interval [CI]: 1.90-3.27; P < 0.001) was independent predictors for subsequent MRSA infections. History of tracheostomy, however, was a protective predictor in all patients (RR: 0.38; 95% CI: 0.18-0.79; P = 0.010) and in patients with MRSA nasal colonization (RR: 0.22; 95% CI: 0.55-0.91; P = 0.037). Molecular genetics studies revealed that most MRSA isolates were healthcare-associated clones and that nasal and clinical isolates exhibited up to 75% shared identity. Methicillin-resistant S. aureus nasal colonization was significantly associated with subsequent MRSA infection among medical ICU patients. Previous MRSA infection was associated with subsequent MRSA infections, and history of tracheostomy associated with reducing this risk. Most MRSA isolates were healthcare-associated strains that were significantly correlated between nasal and clinical isolates.

Tolerability of a probiotic in subjects with a history of methicillin-resistant Staphylococcus aureus colonisation

Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogen of major public health importance. Colonisation precedes infection; thus reducing MRSA carriage may be of benefit for reducing infection. Probiotics represent a novel approach to reducing MRSA carriage. We undertook a pilot feasibility randomised controlled trial of the tolerability and acceptability of probiotics for reducing nasal and intestinal carriage of MRSA. In addition, subjects were screened for vancomycin-resistant enterocococci (VRE). Subjects with a history of MRSA were recruited from a large, academic medical center and randomised to take either a placebo or probiotic (Lactobacillus rhamnosus HN001). Subjects returned to the clinic after four weeks for further testing to determine adherence to the probiotic regimen and colonisation of MRSA. 48 subjects were enrolled and randomised. Nearly 25% were transplant recipients and 30% had diabetes. The probiotic was well tolerated in the study population though minor side effects, such as nausea and bloating, were observed. A majority of the subjects randomised to HN001 had good adherence to the regimen. At the four week time point among subjects randomised to the probiotic, MRSA was detected in 67 and 50% of subjects colonised in the nares and the gastrointestinal tract, respectively. Three subjects who initially tested positive for VRE were negative after four weeks of probiotic exposure. Probiotics were well tolerated in our study population of largely immunocompromised subjects with multiple comorbidities. Adherence to the intervention was good. Probiotics should be studied further for their potential to reduce colonisation by multidrug resistant bacteria.

Duration of Colonization and Determinants of Earlier Clearance of Colonization With Methicillin-Resistant Staphylococcus aureus

BACKGROUND

The duration of colonization and factors associated with clearance of methicillin-resistant Staphylococcus aureus (MRSA) after community-onset MRSA skin and soft-tissue infection (SSTI) remain unclear.

METHODS

We conducted a prospective cohort study of patients with acute MRSA SSTI presenting to 5 adult and pediatric academic hospitals from 1 January 2010 through 31 December 2012. Index patients and household members performed self-sampling for MRSA colonization every 2 weeks for 6 months. Clearance of colonization was defined as negative MRSA surveillance cultures during 2 consecutive sampling periods. A Cox proportional hazards regression model was developed to identify determinants of clearance of colonization.

RESULTS

Two hundred forty-three index patients were included. The median duration of MRSA colonization after SSTI diagnosis was 21 days (95% confidence interval [CI], 19-24), and 19.8% never cleared colonization. Treatment of the SSTI with clindamycin was associated with earlier clearance (hazard ratio [HR], 1.72; 95% CI, 1.28-2.30; P < .001). Older age (HR, 0.99; 95% CI, .98-1.00; P = .01) was associated with longer duration of colonization. There was a borderline significant association between increased number of household members colonized with MRSA and later clearance of colonization in the index patient (HR, 0.85; 95% CI, .71-1.01; P = .06).

CONCLUSIONS

With a systematic, regular sampling protocol, duration of MRSA colonization was noted to be shorter than previously reported, although 19.8% of patients remained colonized at 6 months. The association between clindamycin and shorter duration of colonization after MRSA SSTI suggests a possible role for the antibiotic selected for treatment of MRSA infection.

Strategies to Prevent Transmission of Methicillin-ResistantStaphylococcus aureusin Acute Care Hospitals

Previously published guidelines are available that provide comprehensive recommendations for detecting and preventing healthcare-associated infections (HAIs). Our intent in this document is to highlight practical recommendations in a concise format to assist acute care hospitals in their efforts to prevent transmission of methicillin-resistantStaphylococcus aureus(MRSA). Refer to the Society for Healthcare Epidemiology of America/Infectious Diseases Society of America “Compendium of Strategies to Prevent Healthcare-Associated Infections” Executive Summary, Introduction, and accompanying editorial for additional discussion.

1. Burden of HAIs caused by MRSA in acute care facilities

a. In the United States, the proportion of hospital-associatedS. aureusinfections that are caused by strains resistant to methicillin has steadily increased. In 2004, MRSA accounted for 63% ofS. aureusinfections in hospitals.

b. Although the proportion ofS. aureus–associated HAIs among intensive care unit (ICU) patients that are due to methicillin-resistant strains has increased (a relative measure of the MRSA problem), recent data suggest that the incidence of central line–associated bloodstream infection caused by MRSA (an absolute measure of the problem) has decreased in several types of ICUs since 2001. Although these findings suggest that there has been some success in preventing nosocomial MRSA transmission and infection, many patient groups continue to be at risk for such transmission.

c. MRSA has also been documented in other areas of the hospital and in other types of healthcare facilities, including those that provide long-term care.

Is Methicillin-Resistant Staphylococcus Aureus Colonization Associated with Worse Outcomes in COPD Hospitalizations?

BACKGROUND

Although methicillin-resistant Staphylococcus aureus (MRSA) colonization is common in chronic obstructive pulmonary disease (COPD) patients, its effect on the course of COPD hospitalization remains unknown.

METHODS

Records of 160 patients hospitalized at our institution January 1, 2008 to May 1, 2010 with acute exacerbations of COPD who were screened for MRSA were examined and outcomes from their hospitalizations were quantified.

RESULTS

Of the 160 patients, 33 (20.6%) were MRSA colonized on screening. These patients had similar demographics, spirometry, Charlson Indexes, and APACHE-II scores when compared to patients who were not MRSA colonized (n=127), but MRSA colonized patients had more hospitalizations within the 2 years prior to admission (2 [1-4.8] versus 1 [0-3], p = 0.03). While hospitalized, MRSA colonized patients had a longer length of stay (9 [5.3-15.5] versus 5 [3-7.8] days, p = 0.01) and more antibiotic days (7 [5-10.8] versus 5 [0-7] days, p = 0.01). They were also more likely to receive intensive care (51.5% versus 23.6%, p = 0.01) and to develop respiratory failure that required noninvasive ventilation (56.3% versus 38.2%, p = 0.05). Trends towards increased use of invasive mechanical ventilation and readmission within 30 days were also present.

CONCLUSIONS

COPD patients colonized with MRSA have longer hospitalizations, require longer courses of antibiotics, and are more likely to require intensive care.

Methicillin-resistant Staphylococcus aureus bloodstream infections are associated with a higher energy deficit than other ICU-acquired bacteremia

PURPOSE

Caloric insufficiency during the first week of intensive care unit (ICU) stay was reported to be associated with increased infection rates, especially ICU-acquired bloodstream infection (ICU-BSI). However, the predisposition to ICU-BSI by a given pathogen remains not well known. We aimed to determine the impact of early energy-calorie deficit on the pathogens responsible for ICU-BSI.

DESIGN

Prospective, observational, cohort study in a 18-bed medical ICU of a tertiary care hospital.

METHODS

Daily energy balance (energy-calorie intakes minus calculated energy-calorie expenditure) was compared according to the microbiological results of the blood cultures of 92 consecutive prolonged (at least 96 h) acute mechanically ventilated patients who developed a first episode of ICU-BSI.

RESULTS

Among the 92 ICU-BSI, nine were due to methicillin-resistant Staphylococcus aureus (MRSA). The cumulated energy deficit of patients with MRSA ICU-BSI was greater than those with ICU-BSI caused by other pathogens (-1,348 ± 260 vs -1,000 ± 401 kcal/day from ICU admission to day of ICU-BSI, p = 0.008). ICU admission, risk factors for nosocomial infections, nutritional status, and conditions potentially limiting feeding did not differ significantly between the two groups. Patients with MRSA ICU-BSI had lower delivered energy and similar energy expenditure, causing higher energy deficits. More severe energy deficit and higher rate of MRSA blood cultures (p = 0.01 comparing quartiles) were observed.

CONCLUSIONS

Early in-ICU energy deficit was associated with MRSA ICU-BSI in prolonged acute mechanically ventilated patients. Results suggest that limiting the early energy deficit could be a way to optimize MRSA ICU-BSI prevention.

The prevalence and significance of methicillin-resistant Staphylococcus aureus colonization at admission in the general ICU Setting: a meta-analysis of published studies

OBJECTIVE

To estimate the prevalence and significance of nasal methicillin-resistant Staphylococcus aureus colonization in the ICU and its predictive value for development of methicillin-resistant S. aureus infection.

DATA SOURCES

MEDLINE and EMBASE and reference lists of all eligible articles.

STUDY SELECTION

Studies providing raw data on nasal methicillin-resistant S. aureus colonization at ICU admission, published up to February 2013. Analyses were restricted in the general ICU setting. Medical, surgical, and interdisciplinary ICUs were eligible. ICU studies referring solely on highly specialized ICUs populations and reports on methicillin-resistant S. aureus outbreaks were excluded.

DATA EXTRACTION

Two authors independently assessed study eligibility and extrapolated data in a blinded fashion. The two outcomes of interest were the prevalence estimate of methicillin-resistant S. aureus nasal colonization at admission in the ICU and the sensitivity/specificity of colonization in predicting methicillin-resistant S. aureus-associated infections.

DATA SYNTHESIS

Meta-analysis, using a random-effect model, and meta-regression were performed. Pooled data extracted from 63,740 evaluable ICU patients provided an estimated prevalence of methicillin-resistant S. aureus nasal colonization at admission of 7.0% (95% CI, 5.8-8.3). Prevalence was higher for North American studies (8.9%; 95% CI, 7.1-10.7) and for patients screened using polymerase chain reaction (14.0%; 95% CI, 9.6-19). A significant per year increase in methicillin-resistant S. aureus colonization was also noted. In 17,738 evaluable patients, methicillin-resistant S. aureus infections (4.1%; 95% CI, 2.0-6.8) developed in 589 patients. The relative risk for colonized patients was 8.33 (95% CI, 3.61-19.20). Methicillin-resistant S. aureus nasal carriage had a high specificity (0.96; 95% CI, 0.90-0.98) but low sensitivity (0.32; 95% CI, 0.20-0.48) to predict methicillin-resistant S. aureus-associated infections, with corresponding positive and negative predictive values at 0.25 (95% CI, 0.11-0.39) and 0.97 (95% CI, 0.83-1.00), respectively.

CONCLUSIONS

Among ICU patients, 5.8-8.3% of patients are colonized by methicillin-resistant S. aureus at admission, with a significant upward trend. Methicillin-resistant S. aureus colonization is associated with a more than eight-fold increase in the risk of associated infections during ICU stay, and methicillin-resistant S. aureus infection develops in one fourth of patients who are colonized with methicillin-resistant S. aureus at admission to the ICU.

Predictive value of methicillin-resistant Staphylococcus aureus (MRSA) nasal swab PCR assay for MRSA pneumonia

Pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA) is associated with poor outcomes and frequently merits empirical antibiotic consideration despite its relatively low incidence. Nasal colonization with MRSA is associated with clinical MRSA infection and can be reliably detected using the nasal swab PCR assay. In this study, we evaluated the performance of the nasal swab MRSA PCR in predicting MRSA pneumonia. A retrospective cohort study was performed in a tertiary care center from January 2009 to July 2011. All patients with confirmed pneumonia who had both a nasal swab MRSA PCR test and a bacterial culture within predefined time intervals were included in the study. These data were used to calculate sensitivity, specificity, positive predictive value, and negative predictive value for clinically confirmed MRSA pneumonia. Four hundred thirty-five patients met inclusion criteria. The majority of cases were classified as either health care-associated (HCAP) (54.7%) or community-acquired (CAP) (34%) pneumonia. MRSA nasal PCR was positive in 62 (14.3%) cases. MRSA pneumonia was confirmed by culture in 25 (5.7%) cases. The MRSA PCR assay demonstrated 88.0% sensitivity and 90.1% specificity, with a positive predictive value of 35.4% and a negative predictive value of 99.2%. In patients with pneumonia, the MRSA PCR nasal swab has a poor positive predictive value but an excellent negative predictive value for MRSA pneumonia in populations with low MRSA pneumonia incidence. In cases of culture-negative pneumonia where initial empirical antibiotics include an MRSA-active agent, a negative MRSA PCR swab can be reasonably used to guide antibiotic de-escalation.

Clinical significance of methicillin-resistant Staphylococcus aureus colonization on hospital admission: one-year infection risk

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization among inpatients is a well-established risk factor for MRSA infection during the same hospitalization, but the long-term risk of MRSA infection is uncertain. We performed a retrospective cohort study to determine the one-year risk of MRSA infection among inpatients with MRSA-positive nasal polymerase chain reaction (PCR) tests confirmed by positive nasal culture (Group 1), patients with positive nasal PCR but negative nasal culture (Group 2), and patients with negative nasal PCR (Group 3).

METHODOLOGY/PRINCIPAL FINDINGS

Subjects were adults admitted to a four-hospital system between November 1, 2006 and March 31, 2011, comprising 195,255 admissions. Patients underwent nasal swab for MRSA PCR upon admission; if positive, nasal culture for MRSA was performed; if recovered, MRSA was tested for Panton-Valentine Leukocidin (PVL). Outcomes included MRSA-positive clinical culture and skin and soft tissue infection (SSTI). Group 1 patients had a one-year risk of MRSA-positive clinical culture of 8.0% compared with 3.0% for Group 2 patients, and 0.6% for Group 3 patients (p<0.001). In a multivariable model, the hazard ratios for future MRSA-positive clinical culture were 6.52 (95% CI, 5.57 to 7.64) for Group 1 and 3.40 (95% CI, 2.70 to 4.27) for Group 2, compared with Group 3 (p<0.0001). History of MRSA and concurrent MRSA-positive clinical culture were significant risk factors for future MRSA-positive clinical culture. Group 1 patients colonized with PVL-positive MRSA had a one-year risk of MRSA-positive clinical culture of 10.1%, and a one-year risk of MRSA-positive clinical culture or SSTI diagnosis of 21.7%, compared with risks of 7.1% and 12.5%, respectively, for patients colonized with PVL-negative MRSA (p = 0.04, p = 0.005, respectively).

CONCLUSIONS/SIGNIFICANCE

MRSA nasal colonization is a significant risk factor for future MRSA infection; more so if detected by culture than PCR. Colonization with PVL-positive MRSA is associated with greater risk than PVL-negative MRSA.

Risk factors for development of methicillin-resistant Staphylococcus aureus infection among colonized patients

BACKGROUND

This study was conducted to identify clinical factors associated with development of infection caused by methicillin-resistant Staphylococcus aureus (MRSA) among hospitalized patients with nasal MRSA colonization.

METHODS

We conducted a prospective cohort with nested case-control study at a 672-bed, public, academic hospital in Dallas, Texas. The study duration was from January 1, 2008, to July 28, 2009. From the cohort of patients who had presence of nasal colonization with MRSA at admission, we identified patients who developed subsequent infection with MRSA during a 3-month period. We compared these patients (cases) with colonized patients who remained uninfected (controls; 2 controls per case). We collected demographic and clinical data and performed statistical analyses.

RESULTS

During the 19-month study period, 426 patients were found to have nasal colonization with MRSA. Of these, 36 (8.5%) developed a subsequent infection with MRSA within 3 months. When these 36 cases were compared with 72 controls, the factors independently associated with the development of subsequent infection were development of pressure ulcer during hospital stay (adjusted odds ratio, 5.82; 95% confidence interval: 2.21-15.31; P value=.000) and preadmission steroid therapy (adjusted odds ratio, 13.2; 95% confidence interval: 2.44-70.97; P value=.003).

CONCLUSION

History of steroid therapy prior to admission and development of pressure ulcer are associated with increased risk of subsequent MRSA infection in patients nasally colonized with MRSA.

Multiple site surveillance cultures as a predictor of methicillin-resistant Staphylococcus aureus infections

OBJECTIVE

To determine the relationship between methicillin-resistant Staphylococcus aureus (MRSA) colonization density, colonization site, and probability of infection in a frequently screened cohort of intensive care unit (ICU) patients.

METHODS

Patients had swab samples tested for MRSA at admission to the ICU, discharge from the ICU, and twice weekly during their ICU stay, and they were followed up for development of MRSA infection. Swab test results were analyzed to determine the proportion of patients colonized and the proportion colonized at each screening site. Hazard of MRSA infection (rate of infection per day at risk) was calculated using a Cox proportional hazards analysis, and risk factors for MRSA infection, including presence of MRSA, degree of colonization, and pattern of colonization were determined.

RESULTS

Among the 4,194 patient episodes, 238 (5.7%) had screening results that were positive for MRSA, and there were 34 cases of MRSA infection. The hazard ratio (HR) for developing an infection increased as more sites were colonized (HR, 3.4 for being colonized at more than 1 site compared with colonization at 1 site [95% confidence interval, 1.2-9.9]). Colonization site was predictive of developing infection (HR for nose or throat colonization compared with no colonization, 168 [95% confidence interval, 69-407]).

CONCLUSION

This study demonstrated that the hazard of developing an infection was higher when more sites were colonized and that certain sites were more predictive of infection than others. These results may be useful for predicting infection in ICU patients and may influence treatment.

Identification of nasal bacterial flora profile and carriage rates of methicillin-resistant Staphylococcus aureus in patients with allergic rhinitis

The aim of the present study was to evaluate the effect of allergic rhinitis (AR) on the nasal flora and colonization rates of resistant microorganisms in comparison to healthy individuals. This colonization may be important in terms of AR-related disorders, the resistant microorganisms' carriage, and its complications and co-morbidities. The study was performed with two groups. The study group was composed of 54 adult patients with AR. The control group was composed of 50 healthy individuals. None of the individuals in both groups have used any antibiotics, local or systemic steroid within the last month. Composition of bacterial nasal flora and carriage rates of methicillin-resistant Staphylococcus aureus (MRSA) were evaluated with conventional methods by taking nasal smears with a swab. In the study group, methicillin-sensitive coagulase-negative staphylococci (MRCNS) were detected in 30%; whereas diphtheroids in 25%, methicillin-resistant coagulase-negative staphylococci in 13%, methicillin-sensitive S. aureus in 9%, methicillin-resistant S. aureus in 3.7%, and extended-spectrum beta lactamases-positive gram-negative bacilli (GR-ESBL+) in 3.7% were detected. In the control group, methicillin-sensitive coagulase-negative staphylococci were detected in 54%; whereas diphtheroids in 21%, methicillin-resistant coagulase-negative staphylococci in 1.5%, methicillin-sensitive S. aureus in 16%, methicillin-resistant S. aureus in 1.5%, Gr-ESBL(-) in 4%, and viridians streptococci in 3% were detected. It is found that the MRSA and MRCNS colonization is higher in patients with AR. This colonization may be important in terms of AR-related disorders, the resistant microorganisms' carriage, and its complications and co-morbidities in comparison to healthy subjects.

Long-term risk for readmission, methicillin-resistant Staphylococcus aureus (MRSA) infection, and death among MRSA-colonized veterans

While numerous studies have assessed the outcomes of methicillin-resistant S. aureus (MRSA) colonization over the short term, little is known about longer-term outcomes after discharge. An assessment of long-term outcomes could provide information about the utility of various MRSA prevention approaches. A matched-cohort study was performed among Veterans Affairs (VA) patients screened for MRSA colonization between the years 2007 and 2009 and followed to evaluate outcomes until 2010. Cox proportional-hazard models were used to evaluate the association between MRSA colonization and long-term outcomes, such as infection-related readmission and crude mortality. A total of 404 veterans were included, 206 of whom were MRSA carriers and 198 of whom were noncarriers. There were no culture-proven MRSA infections on readmission among the noncarriers, but 13% of MRSA carriers were readmitted with culture-proven MRSA infections on readmission (P < 0.01). MRSA carriers were significantly more likely to be readmitted, to be readmitted more than once due to proven or probable MRSA infections, and to be readmitted within 90 days of discharge than noncarriers (P < 0.05). Infection-related readmission (adjusted hazard ratio [HR] = 4.07; 95% confidence interval [CI], 2.16 to 7.67) and mortality (adjusted HR = 2.71; 95% CI, 1.87 to 3.91) were significantly higher among MRSA carriers than among noncarriers after statistically adjusting for potential confounders. Among a cohort of VA patients, MRSA carriers are at high risk of infection-related readmission, MRSA infection, and mortality compared to noncarriers. Noncarriers are at very low risk of subsequent MRSA infection. Future studies should address whether interventions such as nasal or skin decolonization could result in improved outcomes for MRSA carriers.

Methicillin-resistant Staphylococcus aureus infection and hospitalization in high-risk patients in the year following detection

BACKGROUND

Many studies have evaluated methicillin-resistant Staphylococcus aureus (MRSA) infections during single hospitalizations and subsequent readmissions to the same institution. None have assessed the comprehensive burden of MRSA infection in the period after hospital discharge while accounting for healthcare utilization across institutions.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a retrospective cohort study of adult patients insured by Harvard Pilgrim Health Care who were newly-detected to harbor MRSA between January 1991 and December 2003 at a tertiary care medical center. We evaluated all MRSA-attributable infections associated with hospitalization in the year following new detection, regardless of hospital location. Data were collected on comorbidities, healthcare utilization, mortality and MRSA outcomes. Of 591 newly-detected MRSA carriers, 23% were colonized and 77% were infected upon detection. In the year following detection, 196 (33%) patients developed 317 discrete and unrelated MRSA infections. The most common infections were pneumonia (34%), soft tissue (27%), and primary bloodstream (18%) infections. Infections occurred a median of 56 days post-detection. Of all infections, 26% involved bacteremia, and 17% caused MRSA-attributable death. During the admission where MRSA was newly-detected, 14% (82/576) developed subsequent infection. Of those surviving to discharge, 24% (114/482) developed post-discharge infections in the year following detection. Half (99/185, 54%) of post-discharge infections caused readmission, and most (104/185, 55%) occurred over 90 days post-discharge.

CONCLUSIONS/SIGNIFICANCE

In high-risk tertiary care patients, newly-detected MRSA carriage confers large risks of infection and substantial attributable mortality in the year following acquisition. Most infections occur post-discharge, and 18% of infections associated with readmission occurred in hospitals other than the one where MRSA was newly-detected. Despite gains in reducing MRSA infections during hospitalization, the risk of MRSA infection among critically and chronically ill carriers persists after discharge and warrants targeted prevention strategies.

Successful control of methicillin-resistant Staphylococcus aureus in endemic neonatal intensive care units--a 7-year campaign

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is among the most important nosocomial pathogens in the intensive care unit (ICU) worldwide, including Taiwan. Since 1997, our neonatal ICUs (NICUs) had become endemic for MRSA.

Methodology/Principal Findings

To control MRSA spread in our NICUs, we implemented a series of infection control measures stepwise, including reinforcement of hand hygiene since January 2000, augmentation of aseptic care over the insertion site of central venous catheter since July 2001, introduction of alcohol-based handrubs since April 2003, surveillance culture for MRSA and cohort care for the colonized patients between March 2003 and February 2004, and surveillance culture with subsequent decolonization of MRSA between August 2005 and July 2006. After implementation of these measures, MRSA healthcare-associated infection (HAI) density reduced by 92%, from 5.47 episodes per 1000 patient-days in 1999 to 0.45 episodes per 1000 patient-days in 2006; MRSA bloodstream infection reduced from 40 cases in 1999 to only one case in 2006. Compared to those obtained during the period of surveillance culture without decolonization, both rates of MRSA colonization (8.6% vs. 41%, p<0.001) and infection (1.1% vs. 12%, p<0.001) decreased significantly during the period of surveillance and decolonization. Molecular analysis of the clinical isolates during the study period showed that the endemic clone, which dominated between 1998 and 2005, almost disappeared in 2006, while the community clones increased significantly in 2006–2007.

Conclusion/Significance

Through infection control measures, MRSA HAIs can be successfully controlled, even in areas with high levels of endemic MRSA infections such as our NICUs.

Molecular epidemiologic analysis of methicillin-resistant Staphylococcus aureus isolates from bacteremia and nasal colonization at 10 intensive care units: multicenter prospective study in Korea

We investigated molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) isolated at 10 intensive care units (ICUs) in Korea. MRSA isolates from bacteremia and nasal colonization were collected prospectively from October 2008 through May 2009 at 10 University-affiliated hospital ICUs. A total of 83 and 175 MRSA strains were isolated from bacteremia and nasal colonization, respectively. Acquired group accounted for 69.9% (n = 58) of bacteremia and 73.1% (n = 128) of nasal colonization. Pulsed-field gel electrophoresis (PFGE) type B (SCCmec type II/ST5) was dominant in the acquired group followed by PFGE type D (SCCmec type IVA/ST72; a community genotype). Seven of 58 (12.1%) acquired bacteremia and 15 of 128 (11.8%) acquired nasal colonizations had SCCmec type IVA/ST72 genotype, which indicated that the community genotype had already emerged as a cause of ICU acquired MRSA infection or colonization. Antibiotic resistance rates to ciprofloxacin, tetracycline, clindamycin and trimethoprim/ sulfamethoxazole were 84.4%, 67.1%, 78.1%, and 12.0%, respectively. Susceptibility to ciprofloxacin best predicted a community genotype (sensitivity 96.5%; specificity 96.9%; odds ratio 861; 95% confidence interval 169-4,390, P < 0.001) and the positive predictive value was 90.2%. Among 23 nasal re-colonized strains, 7 MRSA strains (30.4%) were different from the originally colonized strains on the basis of PFGE types.

Nasal swabs collected routinely to screen for colonization by methicillin-resistant Staphylococcus aureus in intensive care units are a sensitive screening test for the organism in clinical cultures

BACKGROUND

Many hospitals screen patients for methicillin-resistant Staphylococcus aureus (MRSA) on admission to the intensive care unit (ICU). We hypothesized that this screening information could be used to assist with empiric antibiotic decisions.

METHODS

The medical records of patients admitted to a university-affiliated community hospital as well as a tertiary-care university hospital were reviewed. Patients admitted to the ICU were screened for MRSA colonization with a nasal swab that was analyzed with either chromogenic medium (hospital 1) or polymerase chain reaction (PCR) (hospital 2). The results of the nasal swab were compared with clinical culture results.

RESULTS

There were 141 patients, and 167 cultures were obtained. The majority of the cultures (70%) were performed on sputum specimens in an effort to diagnose pneumonia. The remaining cultures were performed on blood (10.1%), incisions (21.5%), and urine (3.4%). The overall sensitivity of nasal swab results was 69.5%. However, the sensitivity was significantly higher for nasal swab screening performed within six days of clinical cultures compared with screening performed seven days or more before cultures were obtained. (79% vs. 46%; p < 0.0001). Sensitivity also differed significantly depending on the surveillance method, being significantly higher among patients screened with PCR within six days of developing an infection than in patients screened with chromogenic medium (88% vs. 65.5%; p = 0.006).

CONCLUSION

Screening with PCR analysis of nasal swab specimens is a highly sensitive test for MRSA in clinical cultures. Clinicians may be able to use the swab results to tailor more appropriate empiric antimicrobial regimens. The results with chromogenic medium screening are markedly poorer, which suggests that clinicians should view them with caution.

Methicillin-resistant staphylococcus aureus screening and eradication in the surgical intensive care unit: Is it worth it?

BACKGROUND

The problem of intensive care unit methicillin-resistant Staphylococcus aureus (MRSA) infections has led to routine surveillance and eradication strategies.

METHODS

Our surgical intensive care unit (SICU) admissions receive MRSA nares cultures and if positive are isolated followed by eradication treatment. This strategy was retrospectively reviewed.

RESULTS

Our nares-positive culture rate was 21% (30/145), and the sputum positive (sputum+) rate was 18% (26/145). Positive nares culture (Nares+) was eradicated in 63%. The rate of sputum+ in Nares+ patients was 36% (9/25). The rate of sputum+ in Nares- was 10% (12/115; P = .003). The sputum+ SICU length of stay (LOS) (18 ± 12 days in 23 S+ patients) is longer than in sputum- (10 ± 9 days in 69 S-patients, P = .0002).

CONCLUSIONS

This SICU has high rates of both nares and sputum MRSA cultures. Our data suggest eradicating nares colonization may prevent pneumonia and might decrease SICU LOS.

The economic effect of screening orthopedic surgery patients preoperatively for methicillin-resistant Staphylococcus aureus

BACKGROUND AND OBJECTIVE

Patients undergoing orthopedic surgery are susceptible to methicillin-resistant Staphylococcus aureus (MRSA) infections, which can result in increased morbidity, hospital lengths of stay, and medical costs. We sought to estimate the economic value of routine preoperative MRSA screening and decolonization of orthopedic surgery patients.

METHODS

A stochastic decision-analytic computer simulation model was used to evaluate the economic value of implementing this strategy (compared with no preoperative screening or decolonization) among orthopedic surgery patients from both the third-party payer and hospital perspectives. Sensitivity analyses explored the effects of varying MRSA colonization prevalence, the cost of screening and decolonization, and the probability of decolonization success.

RESULTS

Preoperative MRSA screening and decolonization was strongly cost-effective (incremental cost-effectiveness ratio less than $6,000 per quality-adjusted life year) from the third-party payer perspective even when MRSA prevalence was as low as 1%, decolonization success was as low as 25%, and decolonization costs were as high as $300 per patient. In most scenarios this strategy was economically dominant (ie, less costly and more effective than no screening). From the hospital perspective, preoperative MRSA screening and decolonization was the economically dominant strategy for all scenarios explored.

CONCLUSIONS

Routine preoperative screening and decolonization of orthopedic surgery patients may under many circumstances save hospitals and third-party payers money while providing health benefits.

Impact of results of methicillin-resistant Staphylococcus aureus surveillance culture of nasal specimens on subsequent antibiotic prescribing patterns

We studied the potential impact of results of methicillin-resistant Staphylococcus aureus (MRSA) surveillance culture of nasal specimens on physicians' vancomycin-prescribing habits. We compared 116 case patients who had positive results with 116 matched control subjects who had negative results. On multivariate analyses, a positive MRSA carrier status remained strongly predictive of vancomycin use within the subsequent 12 weeks.

Methicillin-resistant Staphylococcus aureus nasal colonization is a poor predictor of intensive care unit-acquired methicillin-resistant Staphylococcus aureus infections requiring antibiotic treatment

OBJECTIVE

To test whether intensive care unit (ICU) nasal screening for methicillin-resistant Staphylococcus aureus (MRSA) predicts the presence or absence of MRSA infections requiring antimicrobial treatment.

DESIGN

A prospective cohort study.

SETTING

Medical ICU at Barnes-Jewish Hospital, a 1252-bed urban teaching hospital.

PATIENTS

Seven hundred forty-nine consecutive patients admitted to the medical ICU over a 7-mo period (November 2007 through June 2008).

INTERVENTIONS

Nasal swabs were obtained at ICU admission and weekly thereafter for MRSA detection by using polymerase chain reaction. All subjects were followed for the development of MRSA infection during their ICU stay.

MEASUREMENTS AND MAIN RESULTS

One hundred sixty-four (21.9%) patients had positive nasal colonization with MRSA at the time of ICU admission. The predictive accuracy of MRSA nasal colonization for ICU-acquired MRSA infections, either lower respiratory tract infection or bloodstream infection, was poor (lower respiratory tract infection: sensitivity, 24.2%; specificity, 78.5%; positive predictive value, 17.7%; and negative predictive value, 84.4%; and bloodstream infection: sensitivity, 23.1%; specificity, 78.2%; positive predictive value, 11.0%; and negative predictive value, 89.7%). Addition of nasal-colonization results obtained during the ICU stay did not appreciably change the predictive accuracy of this test for identification of subsequent lower respiratory tract infections and bloodstream infections attributed to MRSA requiring antimicrobial treatment.

CONCLUSIONS

In this analysis, nasal colonization with MRSA was found to be a poor predictor for the subsequent occurrence of MRSA lower respiratory tract infections and MRSA bloodstream infections requiring antimicrobial treatment. Clinicians should be cautious in using the results of nasal-colonization testing to determine the need for MRSA treatment among patients with ICU-acquired infections.

Staphylococcus aureus nasal colonization and subsequent infection in intensive care unit patients: does methicillin resistance matter?

BACKGROUND

Staphylococcus aureus is an important cause of infection in intensive care unit (ICU) patients. Colonization with methicillin-resistant S. aureus (MRSA) is a risk factor for subsequent S. aureus infection. However, MRSA-colonized patients may have more comorbidities than methicillin-susceptible S. aureus (MSSA)-colonized or noncolonized patients and therefore may be more susceptible to infection on that basis.

OBJECTIVE

To determine whether MRSA-colonized patients who are admitted to medical and surgical ICUs are more likely to develop any S. aureus infection in the ICU, compared with patients colonized with MSSA or not colonized with S. aureus, independent of predisposing patient risk factors.

DESIGN

Prospective cohort study.

SETTING

A 24-bed surgical ICU and a 19-bed medical ICU of a 1,252-bed, academic hospital.

PATIENTS

A total of 9,523 patients for whom nasal swab samples were cultured for S. aureus at ICU admission during the period from December 2002 through August 2007.

METHODS

Patients in the ICU for more than 48 hours were examined for an ICU-acquired S. aureus infection, defined as development of S. aureus infection more than 48 hours after ICU admission.

RESULTS

S. aureus colonization was present at admission for 1,433 (27.8%) of 5,161 patients (674 [47.0%] with MRSA and 759 [53.0%] with MSSA). An ICU-acquired S. aureus infection developed in 113 (2.19%) patients, of whom 75 (66.4%) had an infection due to MRSA. Risk factors associated with an ICU-acquired S. aureus infection included MRSA colonization at admission (adjusted hazard ratio, 4.70 [95% confidence interval, 3.07-7.21]) and MSSA colonization at admission (adjusted hazard ratio, 2.47 [95% confidence interval, 1.52-4.01]).

CONCLUSION

ICU patients colonized with S. aureus were at greater risk of developing a S. aureus infection in the ICU. Even after adjusting for patient-specific risk factors, MRSA-colonized patients were more likely to develop S. aureus infection, compared with MSSA-colonized or noncolonized patients.

A European survey of antibiotic management of methicillin-resistant Staphylococcus aureus infection: current clinical opinion and practice

Although the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) varies across Europe, healthcare-associated MRSA infections are common in many countries. Despite several national guidelines, the approach to treatment of MRSA infections varies across the continent, and there are multiple areas of management uncertainty for which there is little clinical evidence to guide practice. A faculty, convened to explore some of these areas, devised a survey that was used to compare the perspectives of infection specialists from across Europe on the management of MRSA infections with those of the faculty specialists. The survey instrument, a web-based questionnaire, was sent to 3840 registered delegates of the 19th European Congress of Clinical Microbiology and Infectious Diseases, held in April 2009. Of the 501 (13%) respondents to the survey, 84% were infection/microbiology specialists and 80% were from Europe. This article reports the survey results from European respondents, and shows a broad range of opinion and practice on a variety of issues pertaining to the management of minor and serious MRSA infections, such as pneumonia, bacteraemia, and skin and soft tissue infections. The issues include changing epidemiology, when and when not to treat, choice of treatment, and duration and route of treatment. The survey identified areas where practice can be improved and where further research is needed, and also identified areas of pan-European consensus of opinion that could be applied to European guidelines for the management of MRSA infection.

Staphylococcus aureus vaccine for orthopedic patients: an economic model and analysis

To evaluate the potential economic value of a Staphylococcus aureus vaccine for pre-operative orthopedic surgery patients, we developed an economic computer simulation model. At MRSA colonization rates as low as 1%, a $50 vaccine was cost-effective [<or=$50,000 per quality-adjusted life year (QALY) saved] at vaccine efficacy >or=30%, and a $100 vaccine at vaccine efficacy >or=70%. High MRSA prevalence (>or=25%) could justify a vaccine price as high as $1000. Our results suggest that a S. aureus vaccine for the pre-operative orthopedic population would be very cost-effective over a wide range of MRSA prevalence and vaccine efficacies and costs.

Staphylococcus aureus nasal colonization and colonization or infection at other body sites in patients on a burn trauma unit

OBJECTIVE

To determine whether Staphylococcus aureus isolates from the nares of patients on a burn trauma unit were related to isolates colonizing or infecting other body sites.

DESIGN

Active surveillance for S. aureus, a case-control study, and pulsed-field gel electrophoresis of S. aureus isolates.

SETTING

A burn trauma unit of a Midwestern university teaching hospital.

PATIENTS

Patients admitted from February 1, 2002, through March 30, 2007, who had S. aureus isolated either from a nasal culture and from another body site (case patients) or from a nasal culture alone (control subjects).

RESULTS

Nineteen patients met the case patient definition and had paired isolates from the nares and an additional site available for typing. Of the 19 case patients, 8 had infections, 7 of which were caused by methicillin-resistant S. aureus (5 USA100 strain and 2 USA300 strain). A total length of stay of more than 3 weeks (odds ratio [OR], 8.75 [95% confidence interval {CI}, 2.2-34.6]; P = .002), residence in a long-term care facility (OR, 9.4 [95% CI, 2.1-42.5]; P = .004), and diabetes (OR, 3.2 [95% CI, 1.0-10.0]; P = .05) were associated with the isolation of S. aureus from the nares and other sites. Seventeen case patients (89.5%) had closely related isolates obtained from culture of samples from the nares and from other sites.

CONCLUSIONS

Prolonged length of stay, diabetes, or residing in a long-term care facility increased the risk of having S. aureus at sites other than the nares. S. aureus isolates from other body sites usually were closely related to nasal isolates. Most case patients had colonized or infected wounds that could be a source of S. aureus for other patients.

Nasal decolonization of Staphylococcus aureus with mupirocin: strengths, weaknesses and future prospects

Staphylococcus aureus in the nose is a risk factor for endogenous staphylococcal infection. UK guidelines recommend the use of mupirocin for nasal decolonization in certain groups of patients colonized with methicillin-resistant S. aureus (MRSA). Mupirocin is effective at removing S. aureus from the nose over a few weeks, but relapses are common within several months. There are only a few prospective randomized clinical trials that have been completed with sufficient patients, but those that have been reported suggest that clearance of S. aureus from the nose is beneficial in some patient groups for the reduction in the incidence of nosocomial infections. There is no convincing evidence that mupirocin treatment reduces the incidence of surgical site infection. New antibiotics are needed to decolonize the nose because bacterial resistance to mupirocin is rising, and so it will become less effective. Furthermore, a more bactericidal antibiotic than mupirocin is needed, on the grounds that it might reduce the relapse rate, and so clear the patient of MRSA for a longer period of time than mupirocin.

Contribution of acquired meticillin-resistant Staphylococcus aureus bacteraemia to overall mortality in a general intensive care unit

During a period of 11 years, 77 patients had meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia > or =5 days after admission to the intensive care unit (ICU). Ten had no prior growth of MRSA, 13 had positive screens on admission and 54 initially tested negative for MRSA in ICU before positive blood culture. These 54 constituted 20.2% [95% confidence interval (CI): 15.6-25.0] of 267 who acquired MRSA > or =5 days after admission. Mortality among 77 patients with MRSA bacteraemia was 57.1% (46.0-68.2). Nineteen of these 77 patients with MRSA bacteraemia had growth of a second pathogen from blood. Those with only MRSA bacteraemia were each matched with five controls by diagnosis and initial Acute Physiological and Chronic Health Evaluation II score. Mortality was greater in bacteraemic patients [53.6% (40.5-66.7)] than in controls [31.8% (26.3-37.3)] [relative risk (RR) 1.69 (1.25-2.26), P < 0.01], implying an additional absolute mortality of 21.8% (8.0-40.1). Application of this estimate to all 77 patients suggests that ICU-acquired MRSA bacteraemia caused 17 (6-31) deaths, adding 0.3% (0.1-0.6) to the 30.1% hospital mortality of all admissions. Incidence of MRSA bacteraemia increased with length of stay, contributing an estimated 3.1% (1.1-5.7) towards 37.9% mortality of the 198 patients remaining > or =25 days. These data emphasise the importance of preventing initial MRSA colonisation/infection of long-stay patients.