Ten common misconceptions about antibiotic use in the hospital

Antimicrobials are one of the most administered medications in hospitals. Thoughtful and rational antibiotic prescribing by clinicians are important in reducing the adverse effects to both the host that takes the antibiotic and also the individuals in the host's community. Principles informing antibiotic prescribing in the hospital are commonly rooted in misconceptions. We review 10 common myths associated with antibacterial usage in hospitalized patients and share contemporary evidence in hopes of enhancing evidence-informed practice in this patient care setting.

A systematic review of the effectiveness of cohorting to reduce transmission of healthcare-associated C. difficile and multidrug-resistant organisms

BACKGROUND

Cohorting of patients and staff is a control strategy often used to prevent the spread of infection in healthcare institutions. However, a comprehensive evaluation of cohorting as a prevention approach is lacking.

METHODS

We performed a systematic review of studies that used cohorting as part of an infection control strategy to reduce hospital-acquired infections. We included studies published between 1966 and November 30, 2019, on adult populations hospitalized in acute-care hospitals.

RESULTS

In total, 87 studies met inclusion criteria. Study types were quasi-experimental "before and after" (n = 35), retrospective (n = 49), and prospective (n = 3). Case-control analysis was performed in 7 studies. Cohorting was performed with other infection control strategies in the setting of methicillin-resistant Staphylococcus aureus (MRSA, n = 22), Clostridioides difficile infection (CDI, n = 6), vancomycin-resistant Enterococcus (VRE, n = 17), carbapenem-resistant Enterobacteriaceae infections (CRE, n = 22), A. baumannii (n = 15), and other gram-negative infections (n = 5). Cohorting was performed either simultaneously (56 of 87, 64.4%) or in phases (31 of 87, 35.6%) to help contain transmission. In 60 studies, both patients and staff were cohorted. Most studies (77 of 87, 88.5%) showed a decline in infection or colonization rates after a multifaceted approach that included cohorting as part of the intervention bundle. Hand hygiene compliance improved in approximately half of the studies (8 of 15) during the respective intervention.

CONCLUSION

Cohorting of staff, patients, or both is a frequently used and reasonable component of an enhanced infection control strategy. However, determining the effectiveness of cohorting as a strategy to reduce transmission of MDRO and C. difficile infections is difficult, particularly in endemic situations.

Oral Vancomycin May Be Associated With Earlier Symptom Resolution Than Metronidazole for Hospitalized Children With Nonsevere Clostridiodes difficile Infections

OBJECTIVE

National guidelines recommend oral vancomycin over oral metronidazole as first-line treatment for nonsevere Clostridioides difficile infection (CDI) in adults. Guidelines recommend metronidazole for children with nonsevere CDI, emphasizing that comparative effectiveness studies comparing the relative efficacy of vancomycin and metronidazole are lacking in children.

METHOD

We conducted an observational study of hospitalized children with nonsevere CDI treated with metronidazole versus vancomycin using an inverse probability of treatment-weighted propensity-score analysis. All of the following criteria had to be present for children with positive CDI testing for study eligibility: (1) ≥3 new-onset unformed stools within a 24-hour period; (2) 2-17 years of age; (3) hospitalization for ≥48 hours for CDI; (4) no laxative use ≤48 hours; (5) no alternate etiology for diarrhea; (6) no previous episode of CDI ≤3 months; (7) no concurrent non-CDI-targeted antibiotic therapy, and (8) no severe or fulminant CDI.

RESULTS

One hundred ninety-two patients met eligibility criteria; 141 (73.4%) received oral metronidazole and 51 (26.6%) children received oral vancomycin. Baseline characteristics were similar between the 2 groups in the weighted cohort. Of 141 patients, 101 (71.7%) children receiving metronidazole had clinical improvement by day 5, whereas 44 of 51 (86.3%) cases resolved with vancomycin (odds ratio, 0.40; 95% confidence interval, 0.17-0.97; P = .04). The odds of CDI recurrence within 12 weeks were similar between the groups.

CONCLUSIONS

Our study suggests that children with nonsevere CDI have earlier resolution of clinical symptoms when prescribed vancomycin compared with metronidazole. Large interventional studies are necessary to evaluate the reproducibility of our findings.

An outbreak of vanA vancomycin-resistant Enterococcus faecium in a hospital with endemic vanB VRE

BACKGROUND

In Australia, vanB vancomycin-resistant Enterococcus faecium (VREfm) has been endemic for over 20 years, but vanA VREfm isolates have rarely been reported.

METHODS

This outbreak report describes an outbreak of vanA VREfm in the intensive care unit (ICU) and cardiothoracic surgery (CTS) wards of a Melbourne hospital in 2015-2016. After the cluster was initially identified in the ICU ward, an active screening programme was implemented. VRE isolates were typed using in silico multi-locus sequence typing. In addition, to screening, enhanced environmental cleaning, chlorhexidine gluconate body washes, and standardisation of the surgical antibiotic prophylaxis regimen were implemented to control the outbreak.

RESULTS

There were 83 new isolates of vanA VREfm recovered from patients in the ICU (n = 31) and CTS (n = 52) wards. Screening identified 78 (94%) of cases. Three patients required treatment for clinical infection with vanA VREfm during the outbreak. The outbreak was polyclonal with 5 different multilocus sequence types carrying the vanA gene (ST17, ST80, ST203, ST252 and ST1421) detected from a subset of isolates (N = 43). The ST17 isolates all carried both the vanA and vanB gene. The intervention bundle resulted in control of the outbreak after 10 months.

CONCLUSION

Geographically, vanA VREfm has previously been uncommon in the region and this outbreak represents a change in local epidemiology. Few VRE outbreaks have been reported in CTS patients. The infection control responses controlled the outbreak within 10-months and may help guide future management of outbreaks.

Antimicrobial-resistant CC17 Enterococcus faecium: The past, the present and the future

Enterococcus faecium is a robust opportunistic pathogen that is most commonly found as a commensal of the human and animal gut but can also survive in the environment. Since the introduction and use of antimicrobials, E. faecium has been found to rapidly acquire resistance genes that, when expressed, can effectively circumvent the effects of most antimicrobials. The rapid acquisition of multiple antimicrobial resistances has led to the adaptation of specific E. faecium clones in the hospital environment, collectively known as clonal complex 17 (CC17). CC17 E. faecium are responsible for a significant proportion of hospital-associated infections, which can cause severe morbidity and mortality. Here we review the history of E. faecium from commensal to a significant hospital-associated pathogen, its robust phenotypic characteristics, commonly used laboratory typing schemes, and antimicrobial resistances with a focus on vancomycin and its associated mechanism of resistance. Finally, we review the global epidemiology of vancomycin-resistant E. faecium and potential solutions to problems faced in public health.

Infection Prevention and Control Issues After Solid Organ Transplantation

Infections are an important cause of morbidity and mortality in solid organ transplant recipients. Consequently, infection prevention is an essential component of any organ transplant program. Given their frequent and often prolonged contact with the healthcare system, solid organ transplant recipients are at high risk for healthcare-associated infections, including those caused by antibiotic-resistant organisms. In this chapter we review several different healthcare-associated infections of importance to transplant recipients, including those caused by bacterial, viral, and fungal organisms. We also describe infection prevention and control strategies applicable to this patient population. These practices focus on clinical interventions and environmental controls designed to prevent the spread of potentially pathogenic organisms in the healthcare setting. We also describe post-exposure interventions applicable to solid organ transplant recipients exposed to potential pathogens in order to reduce their risk of subsequent infection.

Guideline for Prevention of Intravascular-Device–Related Infections

The “Guideline for Prevention of Intravascular Device-Related Infections” is designed to reduce the incidence of intravascular device-related infections by providing an over view of the evidence for recommendations considered prudent by consensus of Hospital Infection Control Practices Advisor y Committee (HICPAC) members. This two-part document updates and replaces the previously published Centers for Disease Control's (CDC) Guideline for Intravascular Infections (Am J Infect Control1983;11:183-199). Part I, “Intravascular Device-Related Infections: An Over view” discusses many of the issues and controversies in intravascular-device use and maintenance. These issues include definitions and diagnosis of catheter-related infection, appropriate barrier precautions during catheter insertion, inter vals for replacement of catheters, intravenous (IV) fluids and administration sets, catheter-site care, the role of specialized IV personnel, and the use of prophylactic antimi-crobials, flush solutions, and anticoagulants. Part II, “Recommendations for Prevention of Intravascular Device-Related Infections” provides consensus recommendations of the HICPAC for the prevention and control of intravascular device-related infections. A working draft of this document also was reviewed by experts in hospital infection control, internal medicine, pediatrics, and intravenous therapy. However, all recommendations contained in the guideline may not reflect the opinion of all reviewers.

Vancomycin Control Measures at a Tertiary-Care Hospital: Impact of Interventions on Volume and Patterns of use

OBJECTIVE: Evaluate vancomycin prescribing patterns in a tertiary-care hospital before and after interventions to decrease vancomycin utilization.

DESIGN: Before/after analysis of interventions to limit vancomycin use.

SETTING: 420-bed academic tertiary-care center.

INTERVENTIONS: Educational efforts began August 10, 1994, and involved lectures to medical house staff followed by mailings to all physicians and posting of guidelines for vancomycin use on hospital information systems. Active interventions began November 15, 1994, and included automatic stop orders for vancomycin at 72 hours, alerts attached to the medical record, and, for 2 weeks only, computer alerts to physicians following each vancomycin order. Parenteral vancomycin use was estimated from the hospital pharmacy database of all medication orders. Records of a random sample of 344 patients receiving van-comycin between May 1, 1994, and April 30, 1995, were reviewed for an indication meeting published guidelines.

RESULTS: Vancomycin prescribing decreased by 22% following interventions, from 8.5 to 6.8 courses per 100 discharges (P<.05). The estimated proportion of van-comycin ordered for an indication meeting published guidelines was 36.6% overall, with no significant change following interventions. However, during the 2 weeks that computer alerts were in place, 60% of vancomycin use was for an approved indication.

CONCLUSIONS: Parenteral vancomycin prescribing decreased significantly following interventions, but the majority of orders still were not for an indication meeting published guidelines. Further improvement in the appropriateness of vancomycin prescribing potentially could be accomplished by more aggressive interventions, such as computer alerts, or by targeting specific aspects of prescribing patterns.

Legislative Mandates for Use of Active Surveillance Cultures to Screen for Methicillin-ResistantStaphylococcus aureusand Vancomycin-Resistant Enterococci: Position Statement From the Joint SHEA and APIC Task Force

Legislation aimed at controlling antimicrobial-resistant pathogens through the use of active surveillance cultures to screen hospitalized patients has been introduced in at least 2 US states. In response to the proposed legislation, the Society for Healthcare Epidemiology of America (SHEA) and the Association of Professionals in Infection Control and Epidemiology (APIC) have developed this joint position statement. Both organizations are dedicated to combating healthcare-associated infections with a wide array of methods, including the use of active surveillance cultures in appropriate circumstances. This position statement reviews the proposed legislation and the rationale for use of active surveillance cultures, examines the scientific evidence supporting the use of this strategy, and discusses a number of unresolved issues surrounding legislation mandating use of active surveillance cultures. The following 5 consensus points are offered. (1) Although reducing the burden of antimicrobial-resistant pathogens, including methicillin-resistantStaphylococcus aureus(MRSA) and vancomycin-resistant enterococci (VRE), is of preeminent importance, APIC and SHEA do not support legislation to mandate use of active surveillance cultures to screen for MRSA, VRE, or other antimicrobial-resistant pathogens. (2) SHEA and APIC support the continued development, validation, and application of efficacious and cost-effective strategies for the prevention of infections caused by MRSA, VRE, and other antimicrobial-resistant and antimicrobial-susceptible pathogens. (3) APIC and SHEA welcome efforts by healthcare consumers, together with private, local, state, and federal policy makers, to focus attention on and formulate solutions for the growing problem of antimicrobial resistance and healthcare-associated infections. (4) SHEA and APIC support ongoing additional research to determine and optimize the appropriateness, utility, feasibility, and cost-effectiveness of using active surveillance cultures to screen both lower-risk and high-risk populations. (5) APIC and SHEA support stronger collaboration between state and local public health authorities and institutional infection prevention and control experts.

Nosocomial Infection Caused by Antibiotic-Resistant Organisms in the Intensive-Care Unit

Resistance to antimicrobial agents is an evolving process, driven by the selective pressure of heavy antibiotic use in individuals living in close proximity to others. The intensive care unit (ICU), crowded with debilitated patients who are receiving broad-spectrum antibiotics and being cared for by busy physicians, nurses, and technicians, serves as an ideal environment for the emergence of antibiotic resistance. Problem pathogens presently include multiply resistant gram-negative bacilli, methicillin-resistantStaphylococcus aureus, and the recently emerged vancomycin-resistant enterococci. The prevention of antimicrobial resistance in ICUs should focus on recognition via routine unit-based sur veillance, improved compliance with handwashing and barrier precautions, and antibiotic-use policies tailored to individual units within hospitals.

Use of daptomycin in the treatment of vancomycin-resistant enterococcal urinary tract infections: a short case series

Background

Vancomycin-resistant enterococci are a leading cause of hospital-acquired urinary tract infection and a growing concern for the clinician. The aim of this study was to evaluate the effectiveness of daptomycin in the treatment of patients with vancomycin-resistant enterococcal urinary tract infection treated in our 200-bed community-based institution.

Methods

Patients with confirmed symptomatic vancomycin-resistant enterococcal urinary tract infection identified by infectious disease consultation between January 1, 2007, and December 8, 2009, vancomycin-resistant enterococci–positive urine culture, and urinary symptoms and/or pyuria on urinalysis, and treated with daptomycin, were included in this case series. Daptomycin was generally administered at a planned dosage regimen of ≥5 mg/kg every 24 hours in patients with normal to moderately impaired kidney function or every 48 hours in patients with severe kidney disease. Microbiologic cure was defined as eradication of vancomycin-resistant enterococci in urine cultures taken after the completion of daptomycin treatment. Clinical cure was defined by symptom resolution, as assessed by the infectious disease clinician caring for the patient.

Results

Included in this case series are 10 patients who received daptomycin for confirmed vancomycin-resistant enterococcal urinary tract infection. Patients had a history of extensive hospital stays. Chart review revealed that all levels of kidney function (3, 2, 3, and 2 patients with kidney disease classified as normal, mild, moderate, and severe/kidney failure, respectively) were represented in the sample and that patients with (n = 5) or without (n = 5) previous urinary tract infection and with (n = 3) or without (n = 7) Foley catheters were included. Treatment with daptomycin achieved clinical cure and vancomycin-resistant enterococcal eradication in all cases in this series.

Conclusion

Treatment with daptomycin was well tolerated and effective in all patients in this series, regardless of renal function, history of urinary tract infection, or Foley catheter use. This study adds to emerging clinical evidence that daptomycin is a valuable treatment for vancomycin-resistant enterococcal urinary tract infection.

Genetic and phenotypic differences among Enterococcus faecalis clones from intestinal colonisation and invasive disease

This study investigated the differences among Enterococcus faecalis isolates from the intestinal compartment of healthy volunteers (n = 36), intensive care unit (ICU) patients (n = 29) and blood isolates (n = 31) from the same institution, in comparison with seven epidemic clones from other institutions. In general, isolates from colonised ICU patients and from bacteraemic patients showed higher rates of antimicrobial resistance than isolates from colonised healthy volunteers, particularly for erythromycin and aminoglycosides. The proportion of isolates/clone was 1.05 in the community, 2.63 in the ICU, and 1.47 among bacteraemic cases, suggesting low clonal variation in ICUs. Two clones, RENC1 and RENC2, were frequently found as intestinal colonisers of ICU patients, and RENC1 was also found to colonise healthy volunteers. These two clones were a cause of bacteraemia in the institution studied, and RENC2 was also detected in various other Spanish hospitals. Both RENC1 and RENC2 were esp+, bacteriocin producers, and were resistant to all antibiotics tested except vancomycin and ampicillin. RENC1 produced haemolysin whereas RENC2 produced protease. The ace, agg, cylA, esp and gelE genes were more common among colonising strains from ICU patients than among isolates from individuals in the community. In both colonised groups (ICUs and the community), 40-50% of isolates harbouring the gelE and cylA genes did not express the corresponding phenotypes. Thus, the study indicated that particular E. faecalis clones might be well-adapted to hospital environments, and that surveillance should be directed specifically towards rapid detection of these disseminating clones in order to prevent infections and clonal spread.

Typing of vancomycin-resistant Enterococcus faecium strains in a cohort of patients in an Italian intensive care Unit

BACKGROUND

Vancomycin-resistant enterococci (VRE) have become a major cause of nosocomial infections. The increase of vancomycin-resistant Enterococcus faecium (VR-Efm) in an intensive care unit (ICU) of an Italian university hospital from 2003 through 2004, led us to evaluate the phenotypic and genetic features of these strains. The prevalence of different bacterial species in this ICU is described. The antibiotic resistance profiles of VR-Efm strains, their van-genotype and pulsed-field gel electrophoresis (PFGE) profiles were also analyzed.

MATERIALS AND METHODS

From January 2003 to December 2004, VR-Efm strains were collected from several biological samples. Bacteria were identified using standard biochemical reactions and automated systems. Antibiotic susceptibility was evaluated by disk diffusion and microdilution methods. Resistance to glycopeptides was confirmed by the E test. Vancomycin-resistant genotypes (vanA, vanB) were identified by PCR. Strains were typed by PFGE.

RESULTS

Fifty E. faecium strains were isolated from a total of 700 patients. Of these, 26 were vancomycin-resistant and were isolated from 26 different patients. We also found one strain with resistance to linezolid. The vanA genotype was identified in 20/26 strains and vanB in the remaining strains. A major pulsed-field cluster ("A") was identified. In this cluster, 14 strains were identified (A1-A14) and 25 out of 26 VR-Efm belonged to it. Only one strain showed a different pattern (strain type "B"). All isolates with the vanA genotype belonged to cluster "A", therefore five out of six isolates with the vanB genotype belonged to cluster A. The only strain with type B pattern was the vanB genotype.

CONCLUSIONS

Isolation of VR-Efm was very frequent (52%) in our cohort of patients and the vanA genotype was the most frequent (77%). We found 25 out of 26 VR-E. faecium strains to be epidemiologically related by PFGE (cluster A). Strains with distinct genotypes shared closely related PFGE profiles. The occurrence of one major cluster among patients of a single unit indicated intra-facility VRE transmission.

A population-based investigation of invasive vancomycin-resistant Enterococcus infection in metropolitan Atlanta, Georgia, and predictors of mortality

BACKGROUND

Vancomycin-resistant Enterococcus organisms (VRE) have emerged as common nosocomial pathogens, but few population-based data are available on the impact of invasive VRE infections.

METHODS

We assessed the incidence of invasive VRE infections and predictors of mortality among patients identified during prospective, population-based surveillance performed in the metropolitan statistical area (MSA) of Atlanta, Georgia.

RESULTS

From July 1997 through June 2000, a total of 192 patients who resided in the Atlanta MSA developed an invasive VRE infection, for a rate of 1.57 cases per 100,000 person-years. The incidence of invasive VRE disease significantly increased from 0.91 cases per 100,000 person-years during the first year of the study to 1.73 cases per 100,000 person-years during the third year of the study (P<.001). Rates of invasive VRE infection were significantly higher among African American patients than white patients (2.59 vs 0.70 cases per 100,000 person-years; P<.001). Blood was the most common sterile site from which VRE was recovered (161 [83%] of 193 isolates), followed by deep surgical sites (17 [9%]), peritoneal fluid (10 [5%]), pleural fluid (3 [2%]), and cerebrospinal fluid (1 [0.5%]). In multivariate analysis, a Charlson comorbidity index of 5 or greater, previous receipt of antibiotic therapy, having 2 or more sets of blood cultures positive for VRE, and receipt of central parenteral nutrition were independent predictors of mortality, whereas receipt of an antibiotic with in vitro activity against the VRE isolate was associated with a decreased risk of mortality. Molecular typing revealed 38 different pulsed-field gel electrophoresis patterns, but the 2 most common pulsed-field gel electrophoresis types were found at 3 Emory University-affiliated hospitals.

CONCLUSIONS

The incidence of invasive VRE infection significantly increased in the Atlanta MSA during the 3-year study period, with significant racial disparities detected. Receipt of an antimicrobial agent with in vitro activity against VRE was associated with a lower mortality rate. Molecular typing results demonstrated polyclonal emergence of VRE in Atlanta.

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.

Compliance with Institutional Guidelines on the Use of Vancomycin in a Medical Intensive Care Unit

Purpose

The University of Michigan implemented guidelines and restrictions for the use of vancomycin in 1995, based on recommendations from the Centers for Disease Control and Prevention. This study evaluated vancomycin use in the University of Michigan's Medical Intensive Care Unit (MICU), and assessed compliance with these institutional guidelines.

Methods

The primary objective of the study was to assess compliance with institutional guidelines. All patients admitted to the MICU who received vancomycin during the period of October 2002 through January 2003 were included in the study. Patients were identified retrospectively and patient medical records were accessed to gather pertinent information. Approval of the Institutional Review Board was obtained.

Results

Fifty-one patients received a total of 71 courses of vancomycin therapy (55 empiric, 16 definitive). Fifty-five (77.5%) of the 71 total courses of vancomycin therapy met institutional criteria. All courses of definitive therapy met specific criteria. Thirty-nine (71%) of the 55 courses of empiric therapy met criteria. Of the courses of empiric therapy which did not fulfill criteria, 12 were from patients exhibiting signs of sepsis and received vancomycin for more than 72 hours, and nine involved immunocompromised patients.

Conclusions

The implementation of guidelines and restrictions is essential to limiting and preventing resistance, but are only effective if designed with the specific hospital's patient population in mind. The results of this study suggest that immunocompromised patients may require a different approach than what is allowed by existing criteria.

Projected Benefits of Active Surveillance for Vancomycin‐Resistant Enterococci in Intensive Care Units

Hospitals use many strategies to control nosocomial transmission of vancomycin-resistant enterococci (VRE). Strategies include "passive surveillance," with isolation of patients with known previous or current VRE colonization or infection, and "active surveillance," which uses admission cultures, with subsequent isolation of patients who are found to be colonized with VRE. We created a mathematical model of VRE transmission in an intensive care unit (ICU) using data from an existing active surveillance program; we used the model to generate the estimated benefits associated with active surveillance. Simulations predicted that active surveillance in a 10-bed ICU would result in a 39% reduction in the annual incidence of VRE colonization when compared with no surveillance. Initial isolation of all patients, with withdrawal of isolation if the results of surveillance cultures are negative, was predicted to result in a 65% reduction. Passive surveillance was minimally effective. Using the best available data, active surveillance is projected to be effective for reducing VRE transmission in ICU settings.

Control of endemic vancomycin-resistant Enterococcus among inpatients at a university hospital

We sought to determine the ability of surveillance cultures and isolation of vancomycin-resistant Enterococcus (VRE)-colonized patients to control nosocomial VRE infection and colonization during a 5-year period (November 1994 through October 1999). During this period, VRE colonization was limited to 0.82% of admissions. The incidence of VRE infection was 0.12 cases per 1000 patient-days (attack rate, 0.07%). Colonized patients were first identified by surveillance (95%) or routine clinical cultures (5%); 14% of colonized patients had a positive clinical culture a median of 15 days after a positive surveillance culture. Ten percent of colonized patients were identified by surveillance at the time of transfer from another health care facility. Identification of these colonized patients was associated with reduction from a peak incidence rate of 2.07% to a rate of 1.25% and stabilization at this lower level. The use of surveillance cultures to identify and isolate patients with asymptomatic colonization can provide sustained control of the spread of VRE within a health care facility.

SHEA guideline for preventing nosocomial transmission of multidrug-resistant strains of Staphylococcus aureus and enterococcus

BACKGROUND

Infection control programs were created three decades ago to control antibiotic-resistant healthcare-associated infections, but there has been little evidence of control in most facilities. After long, steady increases of MRSA and VRE infections in NNIS System hospitals, the Society for Healthcare Epidemiology of America (SHEA) Board of Directors made reducing antibiotic-resistant infections a strategic SHEA goal in January 2000. After 2 more years without improvement, a SHEA task force was appointed to draft this evidence-based guideline on preventing nosocomial transmission of such pathogens, focusing on the two considered most out of control: MRSA and VRE.

METHODS

Medline searches were conducted spanning 1966 to 2002. Pertinent abstracts of unpublished studies providing sufficient data were included.

RESULTS

Frequent antibiotic therapy in healthcare settings provides a selective advantage for resistant flora, but patients with MRSA or VRE usually acquire it via spread. The CDC has long-recommended contact precautions for patients colonized or infected with such pathogens. Most facilities have required this as policy, but have not actively identified colonized patients with surveillance cultures, leaving most colonized patients undetected and unisolated. Many studies have shown control of endemic and/or epidemic MRSA and VRE infections using surveillance cultures and contact precautions, demonstrating consistency of evidence, high strength of association, reversibility, a dose gradient, and specificity for control with this approach. Adjunctive control measures are also discussed.

CONCLUSION

Active surveillance cultures are essential to identify the reservoir for spread of MRSA and VRE infections and make control possible using the CDC's long-recommended contact precautions.

Vancomycin-resistant enterococci: a road map on how to prevent the emergence and transmission of antimicrobial resistance

Nosocomial acquisition of microorganisms resistant to multiple antibiotics represents a threat to patient safety. Here we review the mechanisms that have allowed highly resistant strains belonging to the Enterococcus genus to proliferate within our health-care institutions. These mechanisms indicate that decreasing the prevalence of resistant organisms requires active surveillance, adherence to vigorous isolation, hand hygiene and environmental decontamination measures, and effective antibiotic stewardship. We suggest how to tailor such a complex, multidisciplinary program to the needs of a particular health-care setting so as to maximize cost-effectiveness.

Emergence of vancomycin-resistant Enterococcus faecium at a tertiary care hospital in Karachi, Pakistan

Vancomycin-resistant enterococcus (VRE) has not been reported previously in Pakistan. This is the first report where in vancomycin-resistant Enterococcus faecium was isolated from the clinical specimens of six patients admitted to the intensive care unit (ICU) and neonatal intensive care unit (NICU) of the Aga Khan University Hospital, Karachi. To identify the extent of the outbreak, rectal swabs were obtained from all the patients admitted to the ICU and NICU at that time. A total of 10 strains of vancomycin-resistant Enterococcus faecium were isolated. All the strains showed high-level resistance to both glycopeptides (vancomycin and teicoplanin) with a vancomycin minimum inhibitory concentration greater than 256 mg/L. All isolates had the vanA gene detected by polymerase chain reaction. The contour-clamped homogeneous electric field (CHEF) pattern demonstrated that all but one of the isolates were of a single clone, suggesting that they were derived from common source. Use of vancomycin and prolonged hospitalization were common features in all cases investigated.

Effect of gastrointestinal bleeding and oral medications on acquisition of vancomycin-resistant Enterococcus faecium in hospitalized patients

There has been minimal investigation of medications that affect gastrointestinal function as potential risk factors for the acquisition of vancomycin-resistant enterococci (VRE). We performed a retrospective case-control study, with control subjects matched to case patients by time and location of hospitalization. Strict exclusion criteria were applied to ensure that only case patients with a known time of acquisition of VRE were included. Control patients were patients with > or =1 culture negative for VRE. The risk factors identified were use of vancomycin (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.7-6.0; P=.0003), presence of central venous lines (OR, 2.2; 95% CI, 1.04-4.6; P=.04), and use of antacids (OR, 2.9; 95% CI, 1.5-5.6; P=.002). Two protective factors included gastrointestinal bleeding (OR, 0.26; 95% CI, 0.08-0.79; P=.02) and use of Vicodin (Knoll Labs; hydrocodone and acetaminophen; OR, 0.93; 95% CI, 0.90-0.97; P=.0003). Changes in gastrointestinal function, whether due to bleeding or to the effects of oral medications, may affect whether patients become colonized with VRE.

Cost-effectiveness of perirectal surveillance cultures for controlling vancomycin-resistant Enterococcus

BACKGROUND

Several hospitals opting not to use active surveillance cultures to identify carriers of vancomycin-resistant Enterococcus (VRE) have reported that adoption of other parts of the Centers for Disease Control and Prevention guideline for controlling VRE has had little to no impact. Because use of surveillance cultures and contact isolation controlled a large outbreak at this hospital, their costs were estimated for comparison with the excess costs of VRE bacteremias occurring at a higher rate at a hospital not employing these measures.

SETTING

Two university hospitals.

METHODS

Inpatients deemed high risk for VRE acquisition at this hospital underwent weekly perirectal surveillance cultures. Estimated costs of cultures and resulting isolation during a 2-year period were compared with the estimated excess costs of more frequent VRE bacteremias at another hospital of similar size and complexity not using surveillance cultures to control spread throughout the hospital.

RESULTS

Of 54,052 patients admitted, 10,400 had perirectal swabs taken. Cultures and isolation cost an estimated $253,099. VRE culture positivity was limited to 193 (0.38%) and VRE bacteremia to 1 (0.002%) as compared with 29 bacteremias at the comparison hospital. The estimated attributable cost of VRE bacteremia at the comparison hospital of $761,320 exceeded the cost of the control program at this hospital by threefold.

CONCLUSIONS

The excess costs of VRE bacteremia may justify the costs of preventive measures. The costs of VRE infections at other body sites, of deaths from untreatable infections, and of dissemination of genes for vancomycin resistance also help to justify the costs of implementing an effective control program.

Prevalence and acquisition of vancomycin-resistant enterococci in a medical intensive care unit

Patients admitted to a medical intensive care unit during 21 days had rectal and urine samples cultured for vancomycin-resistant enterococci (VRE). The prevalence rate was 55.3%. Only enteral feedings were associated with acquisition of VRE. One-quarter of VRE transmission resulted from acquisition in the study unit, 35% arrived from other units, and 15% from other hospitals.

Antecedent treatment with different antibiotic agents as a risk factor for vancomycin-resistant Enterococcus

We conducted a matched case-control study to compare the effect of antecedent treatment with various antibiotics on subsequent isolation of vancomycin-resistant Enterococcus (VRE); 880 in-patients; 233 VRE cases, and 647 matched controls were included. After being matched for hospital location, calendar time, and duration of hospitalization, the following variables predicted VRE positivity: main admitting diagnosis; a coexisting condition (e.g., diabetes mellitus, organ transplant, or hepatobiliary disease); and infection or colonization with methicillin-resistant Staphylococcus aureus or Clostridium difficile within the past year (independent of vancomycin treatment). After controlling for these variables, we examined the effect of various antibiotics. Intravenous treatment with third-generation cephalosporins, metronidazole, and fluoroquinolones was positively associated with VRE. In our institution, when we adjusted the data for temporo-spatial factors, patient characteristics, and hospital events, treatment with third-generation cephalosporins, metronidazole, and fluoroquinolones was identified as a risk factor for VRE. Vancomycin was not a risk factor for isolation of VRE.

Molecular analysis of streptogramin resistance in enterococci

The new semi-synthetic streptogramin antibiotic combination quinupristin/dalfopristin (Synercid) is a promising alternative for a treatment of infections with multiple resistant gram-positive pathogens, e.g. glycopeptide- and multi-resistant Enterococcus faecium. Streptogramins consist of two unrelated compounds, a streptogramin A and B, which act synergistically when given in combination. Mechanisms conferring resistance against both components are essential for resistance against the combination in E. faecium. In this species resistance to streptogramin A compounds is mediated via related acetyltransferases VatD and VatE. Resistance against streptogramins B is either encoded by the widespread ermB gene cluster conferring resistance to macrolide-lincosamide-streptogramin B antibiotics or via expression of the vgbA gene, which encodes a staphylococcal-type lactonase. E. faecalis is intrinsically resistant to streptogramins. Due to a wide use of streptogramins (virginiamycins S/M) in commercial animal farming a reservoir of streptogramin-resistant E. faecium isolates had already been selected. Determinants for streptogramin resistance are localized on plasmids that can be transferred into an E. faecium recipient both in vitro in filter-matings and in vivo in the digestive tracts of rats. Hybridization and sequencing experiments revealed a linkage of resistance determinants for streptogramins A and B on definite plasmid fragments.

Frequent transmission of enterococcal strains between mechanically ventilated patients treated at an intensive care unit

The objectives of this investigation were to study the respiratory tract colonization and transmission of enterococci between 20 patients treated with mechanical ventilation at an intensive care unit (ICU), to compare genotyping with phenotyping, and to determine the antibiotic susceptibilities of the isolated enterococci. Samples were collected from the oropharynx, stomach, subglottic space, and trachea within 24 h of intubation, every third day until day 18, and thereafter every fifth day until day 33. Enterococcal isolates (n = 170) were analyzed by pulsed-field gel electrophoresis and with the PhenePlate (PhP) system. The antimicrobial susceptibilities to five agents were determined. Seventeen of the 20 subjects were colonized with enterococci in the respiratory tract; 12 were colonized in the lower respiratory tract. Genotype analyses suggested that 13 patients were involved in a transmission event, including all patients intubated more than 12 days. In conclusion, colonization of resistant enterococci in the respiratory tract of intubated patients treated at an ICU was common. Transmission of enterococci between patients occurred frequently. Prolonged intubation period seems to be a risk factor for enterococcal cross-transmission.

Duration of colonization with vancomycin-resistant Enterococcus

OBJECTIVE

To determine the duration of colonization with vancomycin-resistant Enterococcus (VRE) and the adequacy of 3 consecutive negative cultures to determine clearance.

DESIGN

Retrospective cohort study.

SETTING

A university hospital.

POPULATION

Patients identified by perirectal cultures as VRE carriers who had follow-up cultures.

METHODS

Follow-up perirectal cultures were collected in inpatient and outpatient settings, at least 1 week apart, when patients were not receiving antibiotics with activity against VRE. The likelihood of culture positivity was analyzed given prior culture results and time from the initial positive culture.

RESULTS

A total of 116 patients colonized with VRE had 423 follow-up cultures, a mean of 204 days (range, 4 to 709 days) after their initial isolate. The first follow-up culture, collected a mean of 125 days after the initial positive isolate, was negative in 64%. After 1 negative follow-up culture, the next one was negative in 92% of the patients. After 2 negative cultures, 95% remained culture-negative. After 3 sequential negative cultures, 35 (95%) of 37 patients remained culture-negative. As the interval between the initial and the follow-up isolates increased, the probability that a subsequent culture would be positive decreased (P < .001, chi square for trend). Prolonged hospitalization, intensive care, and antibiotic use each decreased the likelihood of clearing VRE.

CONCLUSION

These data support the Centers for Disease Control and Prevention criterion of 3 sequential negative cultures, at least 1 week apart, to remove patients from VRE isolation. Nevertheless, this may reflect a decrease in the quantity of VRE to an undetectable level and these patients should be observed for relapse, especially when re-treated with antibiotics.

Comparison of agar-based media for primary isolation of glycopeptide-resistant enterococci

OBJECTIVE: To compare four vancomycin-containing agar media for the isolation of glycopeptide-resistant enterococci (GRE) from clinical fecal specimens: kanamycin---aesculin---azide (KAA) agar; bile---aesculin---polymixin (BAP) agar; aztreonam---amphotericin blood (CBAA) agar; and neomycin blood (CBN) agar. METHODS: Fecal specimens from 125 patients were inoculated onto each medium. Media were examined for enterococci after incubation for up to 48 h. Enterococci were identified to species level, and glycopeptide phenotypes were determined by measuring minimum inhibitory concentrations of vancomycin and teicoplanin. RESULTS: GRE were isolated from 44/125 samples. Enterococcus faecalis and Enterococcus faecium isolates, expressing glycopeptide resistance of the VanA or VanB phenotypes, were recovered from 27/33 (82%) specimens on BAP medium, 26/33 (79%) on KAA medium, and 21/33 (64%) on CBN and CBAA media. Enterococcus gallinarum and Enterococcus casseliflavus isolates expressing low-level glycopeptide resistance (VanC phenotype) were recovered from 14/15 (93%) specimens on CBAA medium, 7/15 (47%) on KAA and CBN media, and 6/15 (40%) on BAP medium. CONCLUSIONS: The media tested in this study, with the exception of CBN medium, detected at least 75% of patients colonized by GRE. Further development of BAP, CBAA and KAA media is warranted to improve growth and selectivity.

The effect of active surveillance for vancomycin-resistant enterococci in high-risk units on vancomycin-resistant enterococci incidence hospital-wide

BACKGROUND

Vancomycin-resistant enterococci (VRE) have become a major cause of nosocomial infections and are now endemic in many geographic areas. The aim of this study was to describe the effect of active surveillance for patients with VRE in high-risk units on the VRE incidence rate hospital-wide.

METHODS

We determined 4 time periods based on the intervention of active surveillance: preactive surveillance (period 1), active surveillance (period 2), no active surveillance (period 3), and reinstutition of active surveillance (period 4). VRE incidence rates based on first clinical culture for VRE per 10,000 patient days for each of these periods and incidence rate ratios were then calculated.

RESULTS

Active surveillance in high-risk units was associated with a significant reduction in VRE incidence hospital-wide in 2 of the 3 comparisons made. The incidence rate ratio when comparing the first period of active surveillance (period 2) to the preactive surveillance period (period 1) was 0.63 (95% CI, 0.38-1.1); it was 0.36 (95% CI, 0.23-0.55) when comparing the first period of active surveillance (period 2) to the subsequent period (period 3) and 0.68 (95% CI, 0.54-0.85) when comparing the second period of active surveillance (period 4) to the prior period without active surveillance periods.

CONCLUSIONS

Active surveillance culturing for VRE in the high risk-units prevented further VRE transmission, as evidenced by a significant increase in hospital-wide incidence rates when active surveillance was discontinued and a significant decrease in incidence rates when it was restarted.

Treatment of vancomycin-resistant Enterococcus faecium infections with quinupristin/dalfopristin

Clinicians caring for patients with vancomycin-resistant Enterococcus faecium (VREF) infections face severe constraints in the selection of treatment. Quinupristin/dalfopristin (Synercid) is active in vitro against VREF, with a MIC(90) of 1.0 microg/mL. We investigated the clinical efficacy and safety of this agent in a multicenter, prospective, noncomparative, emergency-use study of 396 patients. Patients were included if they had signs and symptoms of active infection, including bacteremia of unknown origin, intra-abdominal infection, and skin and skin-structure infection, with no alternative antibiotic therapy available. The mean duration of treatment was 20 days (range, 4-40 days). The clinical response rate was 68.8% in the evaluable subset, and the overall response rate was 65.6%. The most common adverse events related to quinupristin/dalfopristin were arthralgias and myalgias. Related laboratory abnormalities were rare. In this severely ill patient population, quinupristin/dalfopristin was efficacious and demonstrated an acceptable safety profile in the treatment of VREF infection.

Vancomycin-resistant enterococci colonization in patients at seven hemodialysis centers

BACKGROUND

Vancomycin-resistant enterococci (VRE) are increasing in prevalence at many institutions, and are often reported in dialysis patients. We studied the prevalence of and risk factors for VRE at seven outpatient hemodialysis centers (three in Baltimore, MD, USA, and four in Richmond, VA, USA).

METHODS

Rectal or stool cultures were performed on consenting hemodialysis patients during December 1997 to April 1998. Consenting patients were recultured during May to July 1998 (median 120 days later). Clinical and laboratory data and functional status (1 to 10 scale: 1, normal function; 9, home attendant, not totally disabled; 10, disabled, living at home) were recorded.

RESULTS

Of 478 cultures performed, 20 (4.2%) were positive for VRE. Among the seven centers, the prevalence of VRE-positive cultures varied from 1.0 to 7.9%. Independently significant risk factors for a VRE-positive culture were a functional score of 9 to 10 (odds ratio 6.9, P < 0.001), antimicrobial receipt within 90 days before culture (odds ratio 6.1, P < 0.001), and a history of injection drug use (odds ratio 5.4, P = 0.004).

CONCLUSIONS

VRE-colonized patients were present at all seven participating centers, suggesting that careful infection-control precautions should be used at all centers to limit transmission. In agreement with previous studies, VRE colonization was more frequent in patients who had received antimicrobial agents recently, underscoring the importance of judicious antimicrobial use in limiting selection for this potential pathogen.

Contamination of gowns, gloves, and stethoscopes with vancomycin-resistant enterococci

OBJECTIVE

[corrected] To measure directly the rate of contamination, during routine patient examination, of gowns, gloves, and stethoscopes with vancomycin-resistant enterococci (VRE).

SETTING

A large, academic, tertiary-care hospital.

PATIENTS

Between January 1997 and December 1998, 49 patients colonized or infected with VRE were entered in the study.

DESIGN

After routine examination, the examiner's glove fingertips, gown (the umbilical region and the cuffs), and stethoscope diaphragm were pressed onto Columbia colistin-nalidixic acid (CNA) agar plates with 5% sheep blood plus vancomycin 6 pg/mL. The stethoscope diaphragm was sampled again after cleaning with a 70% isopropanol wipe.

RESULTS

VRE were isolated from at least 1 examiner site (gloves, gowns, or stethoscope) in 33 (67%) of 49 cases. Gloves were contaminated in 63%, gowns in 37%, and stethoscopes in 31%. All three items were positive for VRE in 24%. One case each had stethoscope and gown contamination without glove contamination. Only 1 (2%) of 49 stethoscopes was positive after wiping with an alcohol swab. Contamination at any site was more likely when the patient had a colostomy or ileostomy. Patients identified by rectal-swab culture alone were as likely to contaminate their examiners as were those identified by clinical specimens.

CONCLUSIONS

Our study revealed a high rate of examiner contamination with VRE. The similar risk of contamination identified by surveillance and clinical cases reinforces concerns that patients not known to be colonized with VRE could serve as sources for dissemination. Wiping with alcohol is effective in decontaminating stethoscopes.

Acquisition of vancomycin-resistant enterococci during scheduled antimicrobial rotation in an intensive care unit

Scheduled rotation of treatment of gram-negative antimicrobial agents has been associated with reduction of serious gram-negative infections. The impact of this practice on other nosocomial infections has not been assessed. The purpose of this study was to determine if scheduled antimicrobial rotation reduced rates of acquisition of enteric vancomycin-resistant enterococci (VRE) among 740 patients admitted to an intensive care unit (ICU). The preferred gram-negative agent was ceftazidime during rotation 1 and ciprofloxacin during rotation 2. Unadjusted VRE acquisition rates were 8.5 cases per 1000 ICU days and 11.7 cases per 1000 ICU days during rotations 1 and 2, respectively (P<.01). However, scheduled antimicrobial rotation of ceftazidime with ciprofloxacin had no effect on the risk of acquiring VRE in the ICU after adjustment for known risk factors. Independent predictors of acquisition of VRE were enteral feedings, higher colonization pressure, and increased duration of anaerobic therapy. Our findings can confirm no additional beneficial or adverse effect on VRE acquisition among ICU patients as a result of this practice.

Antimicrobial management measures to limit resistance: A process-based conceptual framework

To curb the trend toward increasingly resistant microorganisms, we must at least ensure that antibiotics are used in accordance with the best available scientific evidence. Here we review the control and streamlining measures aimed at optimizing the use of antibiotics, placing an emphasis on their demonstrated effectiveness in the intensive care unit environment. Because of their wide variety, the measures have been organized along the process of choosing, dosing, delivering, and then adjusting the initial antibiotics according to the culture results. By clarifying the range of options available, this process-based conceptual framework assists in best adapting a creative mixture of control measures to a particular healthcare system. The framework also facilitates the overview of a proposed multidisciplinary antibiotic management program, thereby helping to secure the administrative and local provider support necessary for its implementation and continued improvement.

Infection control measures to limit antimicrobial resistance

Increasing antimicrobial resistance has resulted in a rapidly decreasing array of therapeutic options for infections in the critical care setting. Reports of reduced susceptibility to vancomycin in Staphylococcus aureus raise the possibility of patients being infected with a virulent pathogen for which most antibiotics are ineffective. Infection control methods to contain resistance, exclusive of antimicrobial restrictions, focus on surveillance to identify carriers of resistant organisms, prevention of nosocomial infections, adequate hand hygiene, isolation of patients who harbor resistant organisms, and the use of barrier techniques such as gowns and gloves. Surveillance using clinical isolates alone is inadequate for the identification of the majority of patients who carry resistant organisms. However, it is unclear what intensity of surveillance is needed to control the spread of these organisms in the intensive care unit in nonoutbreak situations. Attempts at eradicating carriage are often unsuccessful when there is extranasal colonization with methicillin-resistant S. aureus. Transmission of resistant organisms is primarily the result of transient contamination of healthcare workers' hands. Adequate handwashing, isolation of carriers, and barrier techniques are all necessary for containing resistance within the intensive care unit, however, compliance with these measures can be compromised by high staff turnover and heavy workload.

A hospital epidemic of vancomycin-resistant Enterococcus: risk factors and control

OBJECTIVE

To determine risk factors for vancomycin-resistant Enterococcus (VRE) colonization during a hospital outbreak and to evaluate Centers for Disease Control and Prevention (CDC)-recommended control measures.

DESIGN

Epidemiological study involving prospective identification of colonization and a case-control study.

SETTING

A university hospital.

PARTICIPANTS

Patients on eight wards involved in outbreak from late 1994 through early 1995.

METHODS

Cases were matched by ward and culture date with up to two controls. Risk factors were evaluated with four multivariate models using conditional logistic regression. The first evaluated proximity to other VRE patients and isolation status. The second evaluated proximity to unisolated VRE cases and three variables independently predictive after adjustment for proximity. The third evaluated seven significant univariate predictors in addition to proximity to unisolated VRE in backward, stepwise logistic regression. The fourth assessed proximity to VRE with all other variables collected, clustered in a principal components analysis. Pulsed-field gel electrophoresis was performed to assess clonality of two outbreak strains.

RESULTS

The incidence of transmission declined significantly after CDC guidelines were implemented. Proximity to unisolated VRE cases during the prior week was a significant predictor of acquisition in each of four multivariate models. Other significant risk factors in multivariate models included a history of major trauma and treatment with metronidazole. Pulsed-field gel electrophoresis confirmed the clonality of two outbreak strains.

CONCLUSIONS

VRE was transmitted between patients during a hospital epidemic, with proximity to previously unisolated VRE patients being an important risk factor. Weekly surveillance cultures and contact isolation of colonized patients significantly reduced spread

Comparison of three methods to recover vancomycin-resistant enterococci (VRE) from perianal and environmental samples collected during a hospital outbreak of VRE

OBJECTIVE

To establish an efficient and sensitive technique for recovering vancomycin-resistant enterococci (VRE) from perianal and environmental samples collected during implementation of control measures for an outbreak of VRE.

DESIGN

Perianal and environmental samples were collected in triplicate on sterile swabs. One swab was used to inoculate a selective broth medium containing 6 pg of vancomycin and 8 pg of ciprofloxacin per mL, one to inoculate Campylobacter agar containing 10 microg/mL of vancomycin, and one to inoculate Enterococcosel agar containing 8 microg/mL of vancomycin.

SETTING

Samples were collected in the intensive care units of a 600-bed university hospital over a period of 2 months. SAMPLE SELECTION: Patients and their immediate environment were sampled if they resided in a ward with a patient known to be colonized or infected with VRE.

RESULTS

Of the 88 perianal samples obtained from 63 patients, 37 were positive for VRE by broth culture, with 36 also recovered on both types of solid media (sensitivity, 97.3%; negative predictive value, 98.1%). Of the initial samples collected from each of the 63 patients, 20 were positive for VRE by all methods. Of the 500 environmental samples cultured, 139 were positive for VRE in broth, with only 33 recovered on Campylobacter agar (sensitivity, 23.7%; negative predictive value, 77.2%) and 22 on Enterococcosel agar (sensitivity, 15.8%; negative predictive value, 75.2%).

CONCLUSIONS

Our data indicate that, when performing surveillance cultures during an outbreak of VRE, use of an enrichment broth medium is required to recover VRE contaminating environmental surfaces; however, direct inoculation to selective solid medium is adequate to recover VRE in patient perianal specimens.

Vancomycin-resistant enterococci

After they were first identified in the mid-1980s, vancomycin-resistant enterococci (VRE) spread rapidly and became a major problem in many institutions both in Europe and the United States. Since VRE have intrinsic resistance to most of the commonly used antibiotics and the ability to acquire resistance to most of the current available antibiotics, either by mutation or by receipt of foreign genetic material, they have a selective advantage over other microorganisms in the intestinal flora and pose a major therapeutic challenge. The possibility of transfer of vancomycin resistance genes to other gram-positive organisms raises significant concerns about the emergence of vancomycin-resistant Staphylococcus aureus. We review VRE, including their history, mechanisms of resistance, epidemiology, control measures, and treatment.

Prosthetic biologic valve endocarditis caused by a vancomycin-resistant (vanA) Enterococcus faecalis: case report

We recently observed (February 1999) a 68-year old patient with endocarditis on a prosthetic biologic valve caused by a vancomycin-resistant Enterococcus faecalis. Broth dilution tests showed susceptibility to ampicillin (MIC=0.5 microg/ml), no high resistance to aminoglycosides (MIC for gentamicin <500 microg/ml) and resistance to vancomycin (MIC >256 microg/ml) and teicoplanin (MIC >16 microg/ml). A PCR assay detected vanA gene in this strain. A transthoracic echocardiogram did not show valvular vegetations. A possible endocarditis was diagnosed and the patient received ampicillin for 8 weeks and gentamicin for 6 weeks. The patient remained afebrile after a 4-month follow-up when he underwent surgical replacement of the dysfunctional bioprosthetic valve. Mitral valve was sterile on culture, but histology confirmed the diagnosis of previous endocarditis. This is the third case of endocarditis caused by vancomycin-resistant E. faecalis reported to date.

Relationships between enterococcal virulence and antimicrobial resistance

Enterococci have become a vexing problem in clinical medicine because of their ability to infect patients who are typically receiving antibiotic therapy for unrelated underlying illness. Moreover, the infections have become extremely difficult to manage because of the accumulation of antibiotic resistances among enterococci. The ability of enterococci to cause disease is an intrinsic property of the organism or possibly subpopulations within enterococcal species. The probability of an infection's becoming established, however, is almost certainly in part a function of the enterococcal burden. By altering endogenous bacterial flora, antibiotic therapy promotes increased colonization by antibiotic-resistant organisms. Therefore, antibiotic resistance and intrinsic virulence both contribute to disease, but in separate and complementary ways. We review the virulence of enterococci, as distinct from the acquisition of antimicrobial resistance genes, and identify current gaps in our understanding of enterococcal virulence and the basis for disease.

Insights into the epidemiology and control of infection with vancomycin-resistant enterococci

Despite control efforts, the incidence of nosocomial infections due to vancomycin-resistant enterococci (VRE) continues to increase in the United States. VRE are thought to spread primarily by cross-contamination. Recent molecular epidemiologic studies have refined our understanding of this phenomenon. If VRE are not controlled soon after introduction into a hospital, sporadic cases may evolve into a monoclonal outbreak, which may then evolve to polyclonal endemicity. An intervention that is effective in containing VRE in one setting may be ineffective in another. Control of VRE where they are endemic is particularly challenging. Although eradication of endemic VRE may not be possible, aggressive, multifaceted programs have been successful in diminishing the problem. A mathematical model of transmission of VRE and the effect of infection control measures in settings where they are endemic has been reported. The use of such a model may allow more precise determination of the impact of control strategies in the future.

Outbreak of vancomycin-resistant enterococci in a burn unit

OBJECTIVE

To investigate and control an outbreak of colonization and infection caused by vancomycin-resistant enterococci (VRE) in a burn intensive care unit (BICU).

DESIGN

Epidemiological investigation, including multiple point-prevalence culture surveys of patients and environment, cultures from hands of healthcare workers (HCWs), pulsed-field gel electrophoresis (PFGE) typing of patient and environmental isolates, case-control study, and institution and monitoring of control measures.

SETTING

BICU in an 800-bed university medical center in Galveston, Texas.

RESULTS

Between June 6, 1996, and July 14, 1997, 21 patients were colonized by VRE, and 4 of these patients developed bacteremia. Of 2,844 environmental cultures, 338 (11.9%) were positive, but all hand cultures from HCWs were negative. PFGE typing indicated that the outbreak was clonal, with VRE isolates from patients differing by < or =4 bands from the index case. Thirteen of 14 environmental isolates varied by < or =4 bands from the pattern of the index case. A case-control study analyzed by exact logistic regression identified diarrhea (odds ratio [OR], 43.9; 95% confidence interval [CI95], 5.5-infinity; P=.0001) and administration of an antacid (OR, 24.2; CI95, 2.9-infinity; P=.002) as independent risk factors for acquisition of VRE. During a 5-week period in October and November 1996, all patient and 317 environmental cultures were negative for VRE. The outbreak recurred from a contaminated electrocardiogram lead that had not been identified during the prior 5 weeks. VRE were finally eradicated from the BICU in July 1997, using barrier isolation and a very aggressive environmental decontamination program.

CONCLUSIONS

A VRE outbreak in a BICU over 13 months was caused by a single clone. After apparent eradication of VRE from a BICU, recrudescence of the outbreak occurred, evidently from a small inapparent source of environmental contamination. Changes in gastrointestinal (GI) tract function (motility) and administration of medications, other than antibiotics, that have an effect on the GI tract may increase the risk of GI tract colonization by VRE in burn patients. Application of barrier isolation and an aggressive environmental decontamination program can eradicate VRE from a burn population.