Outcomes Associated With Vancomycin-Resistant Enterococci: A Meta-Analysis

Analyzing pathogen transmission in the dialysis unit: time for a (schedule) change?

BACKGROUND AND OBJECTIVES

Infectious diseases and antimicrobial-resistant microorganisms are a growing problem for the dialysis population. The frequency of patient visits and intimate, prolonged physical contact with the inanimate environment during dialysis treatments make these facilities potentially efficient venues for nosocomial pathogen transmission. Isolation measures and infection control practices can be inconvenient and consume limited resources. Quantitative tools for analyzing the effects of different containment strategies can help to identify optimal strategies for further study. However, spatial and temporal considerations germane to the dialysis unit greatly complicate analyses relying on conventional mathematical approaches.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A stochastic, individual-based, Monte Carlo simulation tool that predicts the effects of various infection control strategies on pathogen dissemination through the dialysis unit in the face of diagnostic uncertainty was developed. The model was configured to emulate a medium-sized dialysis unit. The predicted consequences of various policies for scheduling patients who were suspected of being infectious were then explored, using literature-based estimates of pathogen transmissibility, prevalence, and diagnostic uncertainty.

RESULTS

Environmental decontamination was predicted to be of paramount importance in limiting pathogen dissemination. Temporal segregation (scheduling patients who were suspected of being infectious to dialysis shifts that are later in the day) was predicted to have the greatest effectiveness in reducing transmission, given adequate environmental decontamination between successive days.

CONCLUSIONS

Decontamination of the patient's environment (chair) can markedly attenuate pathogen dissemination. Temporal segregation could be a simple, low-cost, system-level intervention with significant potential to reduce nosocomial transmission in the dialysis unit.

Rapid control of an outbreak of vancomycin-resistant enterococci in a French university hospital

Vancomycin-resistant enterococci (VRE) are emerging in French hospitals. A VRE outbreak occurred in our hospital, prompting efforts to eradicate the organism. The following interventions were implemented simultaneously to control the outbreak: (1) creation of a VRE control committee; (2) cohorting of VRE carriers in a dedicated ward; (3) extensive screening of contact patients; (4) use of a sensitive technique for detecting VRE in rectal samples; (5) intervention of a dedicated team to reduce consumption of selected antibiotics; (6) information for, and education of, all hospital staff; and (7) electronic tracking of in-hospital transfer and readmission of VRE carriers and contact patients. Over a four-week period following admission of the index case, 37 carriers of a single strain of vanA vancomycin-resistant Enterococcus faecium were identified across seven units. A single additional readmitted contact patient was identified later. Of the 39 VRE-positive patients, two had urinary tract infections and 37 were colonised. Of the 32 patients with known VRE stool concentrations, 23 had low and nine high concentrations. One low-concentration patient precipitated transmission in another unit. This aggressive, co-ordinated, multifaceted strategy was successful in halting a widespread VRE outbreak in our hospital.

Does vancomycin prescribing intervention affect vancomycin-resistant enterococcus infection and colonization in hospitals? A systematic review

Background

Vancomycin resistant enterococcus (VRE) is a major cause of nosocomial infections in the United States and may be associated with greater morbidity, mortality, and healthcare costs than vancomycin-susceptible enterococcus. Current guidelines for the control of VRE include prudent use of vancomycin. While vancomycin exposure appears to be a risk factor for VRE acquisition in individual patients, the effect of vancomycin usage at the population level is not known. We conducted a systematic review to determine the impact of reducing vancomycin use through prescribing interventions on the prevalence and incidence of VRE colonization and infection in hospitals within the United States.

Methods

To identify relevant studies, we searched three electronic databases, and hand searched selected journals. Thirteen studies from 12 articles met our inclusion criteria. Data were extracted and summarized for study setting, design, patient characteristics, types of intervention(s), and outcome measures. The relative risk, 95% confidence interval, and p-value associated with change in VRE acquisition pre- and post-vancomycin prescription interventions were calculated and compared. Heterogeneity in study results was formally explored by stratified analysis.

Results

No randomized clinical trials on this topic were found. Each of the 13 included studies used a quasi-experimental design of low hierarchy. Seven of the 13 studies reported statistically significant reductions in VRE acquisition following interventions, three studies reported no significant change, and three studies reported increases in VRE acquisition, one of which reported statistical significance. Results ranged from a reduction of 82.5% to an increase of 475%. Studies of specific wards, which included sicker patients, were more likely to report positive results than studies of an entire hospital including general inpatients (Fisher's exact test 0.029). The type of intervention, endemicity status, type of study design, and the duration of intervention were not found to significantly modify the results. Among the six studies that implemented vancomycin reduction strategies as the sole intervention, two of six (33%) found a significant reduction in VRE colonization and/or infection. In contrast, among studies implementing additional VRE control measures, five of seven (71%) reported a significant reduction.

Conclusion

It was not possible to conclusively determine a potential role for vancomycin usage reductions in controlling VRE colonization and infection in hospitals in the United States. The effectiveness of such interventions and their sustainability remains poorly defined because of the heterogeneity and quality of studies. Future research using high-quality study designs and implementing vancomycin as the sole intervention are needed to answer this question.

Prävention und Kontrolle der Ausbreitung von Vancomycin-resistenten Enterokokken

The incidence of vancomycin-resistant enterococci (VRE), especially E. faecium, is increasing in several German hospitals and some facilities have experienced VRE outbreaks. The German National Nosocomial Infection Surveillance System has also noticed a sharp increase in the incidence of nosocomial VRE infections per 10,000 patients from 0.5 in 2003 to 11.0 in 2005 accompanied by a rise in VRE-associated mortality. However, the reasons of this increase remain unknown. As VRE may cause severe nosocomial infections, transmission must be restricted. This article provides the guidelines as defined by the workshop of the German Society for Hygiene and Microbiology for the prevention of VRE transmission in both, endemic and epidemic, settings. The following topics are discussed: indication for VRE screening, microbiological diagnostics, general infection control measures (isolation precautions and use of protective clothing) and additional hygiene measures in the nosocomial VRE outbreak setting.

Daptomycin in the treatment of vancomycin-resistant Enterococcus faecium bacteremia in neutropenic patients

OBJECTIVE

Vancomycin resistant enterococcal (VRE) blood stream infection (BSI) in neutropenic patients is associated with poor outcome. We report our experience in treating VRE BSI in febrile, neutropenic patients with daptomycin, a recently licensed lipopeptide with bactericidal activity against VRE.

PATIENTS AND METHODS

Patients with fever, neutropenia and VRE BSI were treated with more than one dose of daptomycin (either 6 mg/kg/day or 4 mg/kg/day) in an open label, emergency-use trial. Patients were then assessed for clinical and microbiological cures and survival. MIC's of isolates to daptomycin were determined.

RESULTS

Nine febrile, neutropenic patients with VRE BSI received daptomycin. Four of 9 courses (44%) had clinical and/or microbiologic cure. Two of the 5 who failed cure died within 3 days of initiation of daptomycin. Five subjects survived to 30 days after the onset of BSI.

CONCLUSIONS

Use of daptomycin in neutropenic patients with VRE BSI deserves further study as a treatment for VRE BSI in neutropenic patients.

Molecular epidemiology of hospital-acquired vancomycin-resistant enterococci

Vancomycin-resistant Enterococcus faecium strains are a significant cause of nosocomial infections in predisposed patients. Multiple-locus variable-number tandem repeat analysis (MLVA) has been validated recently by use of a global strain collection. In this report, we applied MLVA together with multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) to type 14 isolates from three clusters of patients colonized or infected with vancomycin-resistant Enterococcus faecium and another 10 epidemiologically unrelated isolates from the same hospital. The clusters could be distinguished by all three typing methods, which proved to be concordant. PFGE patterns provided the highest resolution. We observed seven sequence types (ST), six MLVA types (MT), and nine distinct ST/MT combinations. The combination of MLST and MLVA may be an alternative to PFGE in hospital epidemiology, providing the benefits of high accuracy, reproducibility, and portability.

Systemic inflammatory response syndrome in adult patients with nosocomial bloodstream infections due to enterococci

BACKGROUND

Enterococci are the third leading cause of nosocomial bloodstream infection (BSI). Vancomycin resistant enterococci are common and provide treatment challenges; however questions remain about VRE's pathogenicity and its direct clinical impact. This study analyzed the inflammatory response of Enterococcal BSI, contrasting infections from vancomycin-resistant and vancomycin-susceptible isolates.

METHODS

We performed a historical cohort study on 50 adults with enterococcal BSI to evaluate the associated systemic inflammatory response syndrome (SIRS) and mortality. We examined SIRS scores 2 days prior through 14 days after the first positive blood culture. Vancomycin resistant (n = 17) and susceptible infections (n = 33) were compared. Variables significant in univariate analysis were entered into a logistic regression model to determine the affect on mortality.

RESULTS

60% of BSI were caused by E. faecalis and 34% by E. faecium. 34% of the isolates were vancomycin resistant. Mean APACHE II (A2) score on the day of BSI was 16. Appropriate antimicrobials were begun within 24 hours in 52%. Septic shock occurred in 62% and severe sepsis in an additional 18%. Incidence of organ failure was as follows: respiratory 42%, renal 48%, hematologic 44%, hepatic 26%. Crude mortality was 48%. Progression to septic shock was associated with death (OR 14.9, p < .001). There was no difference in A2 scores on days -2, -1 and 0 between the VRE and VSE groups. Maximal SIR (severe sepsis, septic shock or death) was seen on day 2 for VSE BSI vs. day 8 for VRE. No significant difference was noted in the incidence of organ failure, 7-day or overall mortality between the two groups. Univariate analysis revealed that AP2>18 at BSI onset, and respiratory, cardiovascular, renal, hematologic and hepatic failure were associated with death, but time to appropriate therapy >24 hours, age, and infection due to VRE were not. Multivariate analysis revealed that hematologic (OR 8.4, p = .025) and cardiovascular failure (OR 7.5, p = 032) independently predicted death.

CONCLUSION

In patients with enterococcal BSI, (1) the incidence of septic shock and organ failure is high, (2) patients with VRE BSI are not more acutely ill prior to infection than those with VSE BSI, and (3) the development of hematologic or cardiovascular failure independently predicts death.

Validation of VITEK 2 version 4.01 software for detection, identification, and classification of glycopeptide-resistant enterococci

We evaluated the ability of the new VITEK 2 version 4.01 software to identify and detect glycopeptide-resistant enterococci compared to that of the reference broth microdilution method and to classify them into the vanA, vanB, vanC1, and vanC2 genotypes. Moreover, the accuracy of antimicrobial susceptibility testing with agents with improved potencies against glycopeptide-resistant enterococci was determined. A total of 121 enterococci were investigated. The new VITEK 2 software was able to identify 114 (94.2%) enterococcal strains correctly to the species level and to classify 119 (98.3%) enterococci correctly to the glycopeptide resistance genotype level. One Enterococcus casseliflavus strain and six Enterococcus faecium vanA strains with low-level resistance to vancomycin were identified with low discrimination, requiring additional tests. One of the vanA strains was misclassified as the vanB type, and one glycopeptide-susceptible E. facium wild type was misclassified as the vanA type. The overall essential agreements for antimicrobial susceptibility testing results were 94.2% for vancomycin, 95.9% for teicoplanin, 100% for quinupristin-dalfopristin and moxifloxacin, and 97.5% for linezolid. The rates of minor errors were 9% for teicoplanin and 5% for the other antibiotic agents. The identification and susceptibility data were produced within 4 h to 6 h 30 min and 8 h 15 min to 12 h 15 min. In conclusion, use of VITEK 2 version 4.01 software appears to be a reliable method for the identification and detection of glycopeptide-resistant enterococci as well as an improvement over the use of the former VITEK 2 database. However, a significant reduction in the detection time would be desirable.

Preventing Transmission of Multidrug-Resistant Bacteria in Health Care Settings: A Tale of Two Guidelines

Two guidelines for the control of multidrug-resistant organisms in health care facilities have appeared during the past 3 years--one from the Society for Healthcare Epidemiology of America and one, in draft form, from the Healthcare Infection Control Practices Advisory Committee of the Centers for Disease Control and Prevention. These guidelines reflect universal concern in the infection-control community about today's unprecedented levels of activity of multidrug-resistant organisms and about inadequate or inconsistent application of potentially effective control measures. The 2 guidelines provide detailed reviews of pertinent issues and evidence-based, rated recommendations, which overlap considerably. Recommendations regarding indications for active surveillance cultures and the extent of their use constitute the major divergence. Although implementation of comprehensive control plans for multidrug-resistant organisms advocated by both guidelines will require health care facilities to confront difficult programmatic issues, aggressive and widespread adoption of control measures for multidrug-resistant organisms is urgently needed.

Tigecycline and the Need for a New Broad-Spectrum Antibiotic Class

BACKGROUND

Lack of progress in developing new antimicrobials, particularly new classes, as opposed to variants of existing agents, has contributed to the emergence of antibiotic-resistant pathogens.

METHODS

Data synthesis after review of pertinent English-language literature.

RESULTS

The development of new classes of antimicrobial agents is crucial, considering the increasing prevalence of nosocomial pathogens resistant to empiric as well as second- and third-line antibiotic choices. Tigecycline has recently been approved for the treatment of complicated skin and skin structure as well as intra-abdominal infections. Published data on the in vitro and in vivo properties of tigecycline, the first-in-class glycylcycline, are reviewed.

CONCLUSION

It is plausible that tigecycline could to some extent replace available broadspectrum agents for approved indications and thereby reduce the selective pressure for some currently prevalent multi-resistant pathogens in the hospital setting.

Clinical outcomes of penicillin skin testing

BACKGROUND

Penicillin or cephalosporin allergy is a common problem with antibiotic drug prescribing in hospitalized patients.

OBJECTIVES

To study the various clinical outcomes of penicillin skin testing (PST) in a community teaching hospital and to determine the percentage of patients who have an antibiotic drug modification after PST.

METHODS

This study was a retrospective medical record review of all inpatients who underwent PST in 6.6 years. Information was collected on 101 patients using a detailed data collection form. Data were summarized using descriptive statistics, including frequencies and percentages.

RESULTS

Of the 101 patients who underwent PST, 92 had a negative result and 5 had a positive result; in 4 patients the test result was indeterminate. There was a 96% (67/70) reduction in the use of vancomycin and a 96% (23/24) reduction in the use of fluoroquinolones after PST in patients with negative results. Forty-nine percent of patients with negative PST results were administered a penicillin-based drug, and 48% were given a cephalosporin. Cultures were positive most commonly for Staphylococcus aureus and enterococcus. There were no serious adverse reactions to PST or to the use of penicillins or cephalosporins after a negative PST result.

CONCLUSIONS

Penicillin skin testing lowered the use of vancomycin and fluoroquinolones and increased the use of penicillin-based drugs and cephalosporins in patients with a history of beta-lactam drug allergies.

Knowledge, attitudes, and practices of contact precautions among Iranian nurses

BACKGROUND

Knowledge, attitudes, and contact precaution practices were surveyed in nurses at Shiraz University of Medical Sciences.

METHODS

Two hundred seventy nurses, midwives, and auxiliary nurses completed a questionnaire consisting of 8 knowledge items with corresponding attitudes and practices items.

RESULTS

Compliance with precaution practices was low, 19.5%, and little more than half, 51.8%, held positive attitudes toward the guidelines, whereas 65.5% could correctly answered all precaution knowledge items. Nurses with correct knowledge were 11.3 times more likely (P < .0001) to hold positive attitudes toward the guidelines and 14.2 times more likely (P < .0001) to comply with all 8 precaution practices, and compliers were 6.3 times more likely (P < .0001) to hold positive attitudes than noncompliers.

CONCLUSION

Although correct knowledge was associated with compliance and positive attitudes, the proportion of nurses who held positive attitudes also had good knowledge, and compliance with practices was not abundant. Better training coverage may result in compliance with precaution practices becoming the norm.

Comparison of Mortality Associated with Vancomycin-Resistant and Vancomycin-Susceptible Enterococcal Bloodstream Infections: A Meta-analysis

BACKGROUND

Whether vancomycin resistance is independently associated with mortality among patients with enterococcal bloodstream infection (BSI) is controversial. To address this issue, we performed a systematic literature review with meta-analysis.

METHODS

Data sources were studies identified using the MEDLINE database (for articles from 1988 through March 2003), the Cochrane Library (for articles published up to March 2003), and bibliographies of identified articles. Inclusion criteria were that the study assessed mortality after enterococcal BSI, compared mortality after vancomycin-resistant enterococci (VRE) BSI with that after vancomycin-susceptible enterococci (VSE) BSI, and adjusted for severity of illness. Study exclusion criteria were as follows: no report of the adjusted measure of effect (adjusted odds ratio [OR], adjusted hazard ratio, or adjusted relative risk) of vancomycin resistance on mortality available and/or its adjusted 95% confidence interval (95% CI). Data in the tables, figures, or text were independently extracted by 2 of the authors. Individual weights were calculated using the 95% CI of the adjusted measures of effect performing both fixed-effect and random-effects models.

RESULTS

Nine studies were eligible (11 studies met the inclusion criteria, and 2 were excluded), with a total of 1614 enterococcal BSI episodes (683 VRE episodes and 931 VSE episodes). Patients with bacteremia caused by VRE were more likely to die than were those with VSE bacteremia (summary OR, 2.52; 95% CI, 1.9-3.4).

CONCLUSIONS

Vancomycin resistance is independently associated with increased mortality among patients with enterococcal bloodstream infection.

An agent-based and spatially explicit model of pathogen dissemination in the intensive care unit*

OBJECTIVE

To develop and disseminate a spatially explicit model of contact transmission of pathogens in the intensive care unit.

DESIGN

A model simulating the spread of a pathogen transmitted by direct contact (such as methicillin-resistant Staphylococcus aureus or vancomycin-resistant Enterococcus) was constructed. The modulation of pathogen dissemination attending changes in clinically relevant pathogen- and institution-specific factors was then systematically examined.

SETTING AND PATIENTS

The model was configured as a hypothetical 24-bed intensive care unit. The model can be parameterized with different pathogen transmissibilities, durations of caregiver and/or patient contamination, and caregiver allocation and flow patterns.

INTERVENTIONS

Pathogen- and institution-specific factors examined included pathogen transmissibility, duration of caregiver contamination, regional cohorting of contaminated or infected patients, delayed detection and isolation of newly contaminated patients, reduction of the number of caregiver visits, and alteration of caregiver allocation among patients.

MEASUREMENTS AND MAIN RESULTS

The model predicts the probability that a given fraction of the population will become contaminated or infected with the pathogen of interest under specified spatial, initial prevalence, and dynamic conditions. Per-encounter pathogen acquisition risk and the duration of caregiver pathogen carriage most strongly affect dissemination. Regional cohorting and rapid detection and isolation of contaminated patients each markedly diminish the likelihood of dissemination even absent other interventions. Strategies reducing "crossover" between caregiver domains diminish the likelihood of more widespread dissemination.

CONCLUSIONS

Spatially explicit discrete element models, such as the model presented, may prove useful for analyzing the transmission of pathogens within the intensive care unit.

Epidemiology and control of antibiotic resistance in the intensive care unit

PURPOSE OF REVIEW

Resistance to antibiotics is very high in the intensive care units of many countries, although there are several exceptions. Some infections are becoming extremely difficult to treat. The risk of cross-transmission of those strains is very high. This review focuses on recent data (2003 to the present) that may help understanding and dealing with this serious public health problem.

RECENT FINDINGS

Intensive care units can be considered as 'factories' for creating, disseminating and amplifying resistance to antibiotics, for many reasons: importation of resistant microorganisms at admission, selection of resistant strains with an extensive use of broad-spectrum antibiotics, cross-transmission of resistant strains via the hands or the environment. Some national programs can be considered as failures, as in the UK and the USA. Other countries have been able to maintain a low level of resistance (Scandinavian countries, Netherlands, Switzerland, Germany, Canada). There is clearly an 'inoculum effect' above which preventive measures become poorly efficient. Several preventive measures have been proposed including preventive isolation, systematic screening at admission, local, national or international antibiotic guidelines, antibiotic prescriptions advice by infectious-disease teams, antibiotic prevention with selective digestive decontamination, antibiotic strategies such as 'cycling', or rather, for some authors, the use of an 'à la carte' antibiotic strategy which could be considered as a 'patient-to-patient antibiotic rotation'.

SUMMARY

There is obviously an international concern regarding the level of resistance to antibiotics in the intensive-care-unit setting. A strong program including prevention of cross-transmission and better usage of antibiotics seems to be needed in order to be successful. We do not know if this kind of program will enable countries with a very high endemic level of resistance to decrease the level in future years.