Epidemiology and control of an outbreak of vancomycin-resistant enterococci in the intensive care units

PURPOSE

This study was aimed to describe a vancomycin-resistant enterococci (VRE) outbreak across three intensive care units (ICUs) of a Korean hospital from September 2006 to January 2007 and the subsequent control strategies.

MATERIALS AND METHODS

We simultaneously implemented multifaceted interventions to control the outbreak, including establishing a VRE cohort ward, active rectal surveillance cultures, daily extensive cleaning of environmental surfaces and environmental cultures, antibiotic restriction, and education of hospital staff. We measured weekly VRE prevalence and rectal acquisition rates and characterized the VRE isolates by polymerase chain reaction (PCR) of the vanA gene and Sma1-pulsed-field gel electrophoresis (PFGE).

RESULTS

During the outbreak, a total of 50 patients infected with VRE were identified by clinical and surveillance cultures, and 46 had vancomycin-resistant Enterococcus faecium (VREF). PFGE analysis of VREF isolates from initial two months disclosed 6 types and clusters of two major types. The outbreak was terminated 5 months after implementation of the interventions: The weekly prevalence rate decreased from 9.1/100 patients-day in September 2006 to 0.6/100 by the end of January 2007, and the rectal acquisition rates also dropped from 6.9/100 to 0/100 patients-day.

CONCLUSION

Our study suggests that an aggressive multifaceted control strategy is a rapid, effective approach for controlling a VRE outbreak.

Rapid curbing of a vancomycin-resistant Enterococcus faecium outbreak in a nephrology department

BACKGROUND AND OBJECTIVES

Vancomycin-resistant enterococci (VRE) are recovered with increasing frequency among patients with chronic renal failure, making VRE a major concern in nephrology departments, especially for patients who are treated by hemodialysis. We report herein the successful aggressive management of a VRE outbreak in a nephrology department.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

An Enterococcus faecium vanB strain was isolated from a peritoneal dialysis solution from an inpatient. Immediately, infection control measures were enforced and active screening was performed for all contact patients. Carriers were isolated, and patients were divided into three cohorts: Positive, contact, and noncontact patients. We then performed a case-control study to understand risk factors for VRE carriage comparing VRE carriers with contact patients who were negative for VRE.

RESULTS

A total of 14 VRE-positive and 125 VRE-negative contact patients were identified. VRE-positive patients were more likely to receive hemodialysis and have longer hospital stays in nephrology. VRE-positive patients more often had a central venous catheter for a longer period of time and received more antibiotics than VRE-negative patients. Treatment with large-spectrum beta-lactams and number of days in the nephrology ward were significantly associated with a higher risk for VRE carriage by using multivariate analysis.

CONCLUSIONS

These findings suggest that case mix, longer hospital stays, and antibiotic use are major risk factors for VRE acquisition. In addition, it demonstrates that strict enforcement of isolation precautions and cohorting associated with active screening are successful to curb the transmission of VRE in renal units despite continuous colonization pressure.

Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 6. Transmission and survival of pathogens in the food processing and preparation environment

This article, the sixth in a series reviewing the role of food workers in foodborne outbreaks, describes the source and means of pathogen transfer. The transmission and survival of enteric pathogens in the food processing and preparation environment through human and raw food sources is reviewed, with the main objective of providing information critical to the reduction of illness due to foodborne outbreaks. Pathogens in the food preparation area can originate from infected food workers, raw foods, or other environmental sources. These pathogens can then spread within food preparation or processing facilities through sometimes complex pathways and may infect one or more workers or the consumer of foods processed or prepared by these infected workers. The most frequent means of worker contamination is the fecal-oral route, and study results have indicated that toilet paper may not stop transmission of pathogens to hands. However, contact with raw foods of animal origin, worker aerosols (from sneezes), vomitus, and exposed hand lesions also have been associated with outbreaks. Transfer of pathogens has been documented through contaminated fabrics and carpets, rings, currency, skin surfaces, dust, and aerosols and though person-to-person transmission. Results of experiments on pathogen survival have indicated that transmission depends on the species, the inoculum delivery route, the contact surface type, the duration and temperature of exposure, and the relative humidity. Generally, viruses and encysted parasites are more resistant than enteric bacteria to adverse environmental conditions, but all pathogens can survive long enough for transfer from a contaminated worker to food, food contact surfaces, or fellow workers.

Biometric fingerprinting for visa application: device and procedure are risk factors for infection transmission

BACKGROUND

Biometric fingerprint identity verification is currently introduced in visa application and entry screening at border control. The system implies physical contact between the skin and the surface of the fingerprint-capturing and reading devices.

AIM

To assess the risk of infection transmission through fingerprinting.

METHODS

The medical literature was reviewed for the potential of microorganisms to be carried on the skin of hands in the community, to be transferred from hands to inanimate surfaces, to survive on surfaces, and to be transferred in doses exceeding the infectious dose. The fingerprinting procedures as currently applied were reviewed.

RESULTS

Factors that favor transfer of microorganisms are large skin-surface contact between flat fingers (2 x 20 cm(2)) and fingerprint-capturing device, nonporous contact surface, large overlap of contact surface and short turnaround time between successive applicants, high contact pressure, and difficulties to disinfect devices. Transmission risk exists for enteric viruses (rotavirus, norovirus, and hepatitis A virus), respiratory viruses (respiratory syncytial virus, rhinovirus, influenza virus, etc.), and enteropathogenic bacteria with low infectious doses (Shigella dysenteriae, Enterohemorrhagic Escherichia coli, etc.). Using Monte Carlo risk analysis on US data, transmission of human rotavirus is estimated at 191 [95% credible intervals (CI) 0-289] per million fingerprint-capturing procedures. Application of 70% isopropyl hand rub and 85% ethanol hand gel reduces the risk to 77 (95% CI 0-118) and 0.3 (95% CI 0-0.3) transmissions per million procedures, respectively.

CONCLUSIONS

The fingerprinting procedure as currently used is associated with a risk of infection transmission. Simple hygienic measures can considerably reduce this transmission risk.

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.

Evidence-based model for hand transmission during patient care and the role of improved practices

Hand cleansing is the primary action to reduce health-care-associated infection and cross-transmission of antimicrobial-resistant pathogens. Patient-to-patient transmission of pathogens via health-care workers' hands requires five sequential steps: (1) organisms are present on the patient's skin or have been shed onto fomites in the patient's immediate environment; (2) organisms must be transferred to health-care workers' hands; (3) organisms must be capable of surviving on health-care workers' hands for at least several minutes; (4) handwashing or hand antisepsis by the health-care worker must be inadequate or omitted entirely, or the agent used for hand hygiene inappropriate; and (5) the caregiver's contaminated hand(s) must come into direct contact with another patient or with a fomite in direct contact with the patient. We review the evidence supporting each of these steps and propose a dynamic model for hand hygiene research and education strategies, together with corresponding indications for hand hygiene during patient care.

How long do nosocomial pathogens persist on inanimate surfaces? A systematic review

BACKGROUND

Inanimate surfaces have often been described as the source for outbreaks of nosocomial infections. The aim of this review is to summarize data on the persistence of different nosocomial pathogens on inanimate surfaces.

METHODS

The literature was systematically reviewed in MedLine without language restrictions. In addition, cited articles in a report were assessed and standard textbooks on the topic were reviewed. All reports with experimental evidence on the duration of persistence of a nosocomial pathogen on any type of surface were included.

RESULTS

Most gram-positive bacteria, such as Enterococcus spp. (including VRE), Staphylococcus aureus (including MRSA), or Streptococcus pyogenes, survive for months on dry surfaces. Many gram-negative species, such as Acinetobacter spp., Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, Serratia marcescens, or Shigella spp., can also survive for months. A few others, such as Bordetella pertussis, Haemophilus influenzae, Proteus vulgaris, or Vibrio cholerae, however, persist only for days. Mycobacteria, including Mycobacterium tuberculosis, and spore-forming bacteria, including Clostridium difficile, can also survive for months on surfaces. Candida albicans as the most important nosocomial fungal pathogen can survive up to 4 months on surfaces. Persistence of other yeasts, such as Torulopsis glabrata, was described to be similar (5 months) or shorter (Candida parapsilosis, 14 days). Most viruses from the respiratory tract, such as corona, coxsackie, influenza, SARS or rhino virus, can persist on surfaces for a few days. Viruses from the gastrointestinal tract, such as astrovirus, HAV, polio- or rota virus, persist for approximately 2 months. Blood-borne viruses, such as HBV or HIV, can persist for more than one week. Herpes viruses, such as CMV or HSV type 1 and 2, have been shown to persist from only a few hours up to 7 days.

CONCLUSION

The most common nosocomial pathogens may well survive or persist on surfaces for months and can thereby be a continuous source of transmission if no regular preventive surface disinfection is performed.

Sensitivity to detergents and plasmid curing in Enterococcus faecalis

This research reports the sensitivity of a clinical isolate of Enterococcus faecalis to sodium N-lauroylsarcosinate (sarkosyl) and sodium dodecyl sulfate (SDS), as well as the efficiency of these detergents in curing the strain. Compared to Escherichia coli, Enterococcus faecalis was very sensitive to both detergents, with minimum inhibitory concentrations (MIC) for the latter being 100 times lower than for Escherichia coli. The clinical isolate of Enterococcus faecalis used in this study exhibited plasmid-borne resistance to kanamycin (MIC 2 mg/ml) and tetracycline (MIC 50 mug/ml); 3% curing was observed after growth in the presence of sarkosyl but no curing was observed after growth in the presence of either SDS or acridine orange. In contrast, 35% curing of plasmid-bearing Escherichia coli was observed after growth in the presence of either SDS or acridine orange, but none was observed after growth in the presence of sarkosyl.

Vancomycin-resistant enterococcal bacteremia in a hematology unit: molecular epidemiology and analysis of clinical course

An increase in vancomycin-resistant enterococcal (VRE) bacteremia in hemato-oncological patients (n=19) in our institution from 2000 through 2001 led us to analyze the molecular epidemiologic patterns and clinical features unique to our cases. The pulsed field gel electrophoresis of the isolates revealed that the bacteremia was not originated from a single clone but rather showed endemic pattern of diverse clones with small clusters. A different DNA pattern of blood and stool isolates from one patient suggested exogenous rather than endogenous route of infection. Enterococcus faecium carrying vanA gene was the causative pathogen in all cases. Patients with VRE bacteremia showed similar clinical courses compared with those with vancomycin-susceptible enterococcal (VSE) bacteremia. Vancomycin resistance did not seem to be a poor prognostic factor because of similar mortality (5/8, 62.5%) noted in VSE bacteremia. Initial disease severity and neutropenic status may be major determinants of prognosis in patients with VRE bacteraemia.

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.

Epidemiologic background of hand hygiene and evaluation of the most important agents for scrubs and rubs

The etiology of nosocomial infections, the frequency of contaminated hands with the different nosocomial pathogens, and the role of health care workers' hands during outbreaks suggest that a hand hygiene preparation should at least have activity against bacteria, yeasts, and coated viruses. The importance of efficacy in choosing the right hand hygiene product is reflected in the new Centers for Disease Control and Prevention guideline on hand hygiene (J. M. Boyce and D. Pittet, Morb. Mortal. Wkly. Rep. 51:1-45, 2002). The best antimicrobial efficacy can be achieved with ethanol (60 to 85%), isopropanol (60 to 80%), and n-propanol (60 to 80%). The activity is broad and immediate. Ethanol at high concentrations (e.g., 95%) is the most effective treatment against naked viruses, whereas n-propanol seems to be more effective against the resident bacterial flora. The combination of alcohols may have a synergistic effect. The antimicrobial efficacy of chlorhexidine (2 to 4%) and triclosan (1 to 2%) is both lower and slower. Additionally, both agents have a risk of bacterial resistance, which is higher for chlorhexidine than triclosan. Their activity is often supported by the mechanical removal of pathogens during hand washing. Taking the antimicrobial efficacy and the mechanical removal together, they are still less effective than the alcohols. Plain soap and water has the lowest efficacy of all. In the new Centers for Disease Control and Prevention guideline, promotion of alcohol-based hand rubs containing various emollients instead of irritating soaps and detergents is one strategy to reduce skin damage, dryness, and irritation. Irritant contact dermatitis is highest with preparations containing 4% chlorhexidine gluconate, less frequent with nonantimicrobial soaps and preparations containing lower concentrations of chlorhexidine gluconate, and lowest with well-formulated alcohol-based hand rubs containing emollients and other skin conditioners. Too few published data from comparative trials are available to reliably rank triclosan. Personnel should be reminded that it is neither necessary nor recommended to routinely wash hands after each application of an alcohol-based hand rub. Long-lasting improvement of compliance with hand hygiene protocols can be successful if an effective and accessible alcohol-based hand rub with a proven dermal tolerance and an excellent user acceptability is supplied, accompanied by education of health care workers and promotion of the use of the product.

Hemolytic and nonhemolytic vancomycin-resistant Enterococcus faecalis isolated from beef imported to Malaysia

Twenty-two strains of vancomycin-resistant Enterococcus faecalis were isolated from 9 (6%) of 150 samples of frozen beef and beef products imported to Malaysia. The isolates were obtained from eight samples of beef and one sample of minced beef patty. No E. faecalis was isolated from frankfurters. Twelve of the 22 isolates (54.5%) were beta-hemolytic, and all isolates harbored the vanA gene. All vancomycin-resistant isolates were also resistant to streptomycin, erythromycin, kanamycin, bacitracin, ceftazimide, gentamycin, tetracycline, nalidixic acid, and teicoplanin; 95.4% were resistant to trimethoprimsulfamethoxazole; 68.8% were resistant to chloramphenicol; and 41% were resistant to ampicillin and penicillin. Small plasmids ranging in size from 1.5 to 5.8 kb were detected in 8 (36.4%) of 22 strains. The 22 isolates were classified into 20 random amplified polymorphic DNA types. Isolates were divided into two groups, each containing subclusters, that may reflect their clonal lineages. It is concluded that several clones of vancomycin-resistant E. faecalis are represented in the isolates obtained from beef imported to Malaysia.

Enterococcus faecalis and Enterococcus faecium isolates from milk, beef, and chicken and their antibiotic resistance

The occurrence and antibiotic resistance of enterococci, especially Enterococcus faecalis and Enterococcus faecium, in milk, beef, and chicken in Gaborone, Botswana, were studied. Enterococci were isolated from these sources with the use of bile esculin agar and identified with API 20 Strep kits. Antibiotic resistance was determined by the disk diffusion method. The antibiotics tested were vancomycin, teicoplanin, ampicillin, tetracycline, and cephalothin. Among the 1,467 enterococci isolated from the samples, E. faecalis (46.1%) and E. faecium (29.0%) were found to be the predominant species. Other enterococcal species made up 25% of the isolates. More than 96 and 97% of the E. faecalis and E. faecium isolates, respectively, were found to be resistant to ampicillin. Almost 34, 27.3, and 22.4% of the E. faecalis isolates from milk, beef, and chicken, respectively, were also resistant to cephalothin. The percentages of E. faecium isolates that were found to be resistant to cephalothin were 32.8, 16.9, and 17.3% for milk, beef, and chicken, respectively. Resistance to vancomycin was widespread. It was found that 18.8, 7.8. and 13.1% of the E. faecalis isolates from milk, beef, and chicken samples, respectively, were resistant to vancomycin. In contrast, 32.8, 24.7, and 30.7% of the E. faecium isolates from milk, beef, and chicken samples, respectively, were resistant to vancomycin. Isolates that were resistant to multiple drugs were found in relatively large numbers.

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.

Potential impact of increased use of biocides in consumer products on prevalence of antibiotic resistance

There has recently been much controversy surrounding the increased use of antibacterial substances in a wide range of consumer products and the possibility that, as with antibiotics, indiscriminate use of biocides might contribute to the overall pattern of susceptibility in the general environment and in the clinic. Such speculation, based on the isolation of resistant mutants from in vitro monoculture experiments, is not reflected by an emergence of biocide-resistant strains in vivo. This review provides a broad coverage of the biocide and resistance literature and evaluates the potential risks, perceived from such laboratory monoculture experiments, against evidence gathered over 50 years of field studies. An explanation for the continued effectiveness of broad-spectrum biocidal agents against the decline in efficacy of therapeutic agents is provided based on the fitness costs of resistance and the ubiquity of naturally occurring substances that possess antibacterial effect. While we conclude from this review of the literature that the incorporation of antibacterial agents into a widening sphere of personal products has had little or no impact on the patterns of microbial susceptibility observed in the environment, the associated risks remain finite. The use of such products should therefore be associated with a clear demonstration of added value either to consumer health or to the product life. Hygienic products should therefore be targeted to applications for which the risks have been established.

Bacterial contamination of computer keyboards in a teaching hospital

We tested 100 keyboards in 29 clinical areas for bacterial contamination. Ninety five were positive for microorganisms. Streptococcus, Clostridium perfringens, Enterococcus (including one vancomycin-resistant Enterococcus), Staphylococcus aureus, fungi, and gram-negative organisms were isolated. Computer equipment must be kept clean so it does not become another vehicle for transmission of pathogens to patients.

Infection with antimicrobial-resistant microorganisms in dialysis patients

The prevalence of antimicrobial-resistant microorganisms in various health care settings, including outpatient dialysis facilities, has increased dramatically in the last decade. Antimicrobial use and patient-to-patient transmission of resistant strains are the two main factors that have contributed to this rapid increase. Methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci are commonly isolated as a cause of hemodialysis (HD) catheter-related bacteremia and peritoneal dialysis (PD)-related catheter infection and peritonitis. The widespread use of vancomycin in dialysis patients is of concern because of an increase in the prevalence of vancomycin-resistant enterococci (VRE) in dialysis patients. Staphylococci with reduced sensitivity to vancomycin have also appeared in dialysis patients. A more recent problem is the appearance of S. aureus isolates with a high degree of resistance to the topical antimicrobial agent mupirocin. This has been seen in PD patients who have received prophylactic application of mupirocin at the peritoneal catheter exit site. Appropriate antimicrobial use will help protect the efficacy of currently used antibiotics, such as vancomycin. Published guidelines for use of vancomycin should be followed. New antimicrobials such as linezolid and quinupristin/dalfopristin have activity against VRE and MRSA, but resistance to these agents has already occurred. Preventing transmission of antimicrobial-resistant microorganisms in health care settings, including outpatient dialysis facilities, is important in limiting the spread of these resistant organisms.

Comparative surface-to-hand and fingertip-to-mouth transfer efficiency of gram-positive bacteria, gram-negative bacteria, and phage

AIMS

To determine the transfer efficiency of micro-organisms from fomites to hands and the subsequent transfer from the fingertip to the lip.

METHODS AND RESULTS

Volunteers hands were sampled after the normal usage of fomites seeded with a pooled culture of a Gram-positive bacterium (Micrococcus luteus), a Gram-negative bacterium (Serratia rubidea) and phage PRD-1 (Period A). Activities included wringing out a dishcloth/sponge, turning on/off a kitchen faucet, cutting up a carrot, making hamburger patties, holding a phone receiver, and removing laundry from the washing machine. Transfer efficiencies were 38.47% to 65.80% and 27.59% to 40.03% for the phone receiver and faucet, respectively. Transfer efficiencies from porous fomites were <0.01%. In most cases, M.luteus was transferred most efficiently, followed by phage PRD-1 and S. rubidea. When the volunteers' fingertips were inoculated with the pooled organisms and held to the lip area (Period B), transfer rates of 40.99%, 33.97%, and 33.90% occurred with M. luteus, S. rubidea, and PRD-1, respectively.

CONCLUSIONS

The highest bacteral transfer rates from fomites to the hands were seen with the hard, non-porous surfaces. Even with low transfer rates, the numbers of bacteria transferred to the hands were still high (up to 10(6) cells). Transfer of bacteria from the fingertip to the lip is similar to that observed from hard surfaces to hands.

SIGNIFICANCE AND IMPACT OF THE STUDY

Infectious doses of pathogens may be transferred to the mouth after handling an everyday contaminated household object.

A prospective study to determine whether cover gowns in addition to gloves decrease nosocomial transmission of vancomycin-resistant enterococci in an intensive care unit

BACKGROUND

Vancomycin-resistant enterococci (VRE) remain a significant nosocomial pathogen. Current guidelines of the Hospital Infection Control Practices Advisory Committee (HICPAC) of the Centers for Disease Control and Prevention (CDC) recommend the use of gowns and gloves for some interactions with VRE-infected or -colonized patients to prevent nosocomial transmission of VRE.

OBJECTIVE

To assess the effect of disposable cover gowns on preventing nosocomial transmission of VRE.

DESIGN AND SETTING

Prospective study in a 16-bed medical intensive care unit of a university teaching hospital.

PATIENTS

All patients who were at risk to acquire VRE, were admitted to the intensive care unit from August 1998 to January 1999, and had at least two perirectal cultures were included in the analysis of VRE acquisition.

INTERVENTION

VRE isolation precautions were changed from gowns and gloves to gloves alone. MAIN OUTCOME risk factors for VRE acquisition.

RESULTS

The VRE acquisition rate was 1.80 cases per 100 days at risk in the gown and gloves period compared with 3.78 in the gloves only period (P = .04). In a proportional hazards model adjusted for length of stay, gloves only precautions with a hazard ratio of 2.5 (P = .02; 95% confidence interval, 1.2 to 5.3) were the only independent risk factor for VRE acquisition.

CONCLUSION

Our data lend support to current HICPAC recommendations for the use of cover gowns to decrease nosocomial transmission of VRE.

A quantitative study of the survival of two species of Candida on porous and non-porous environmental surfaces and hands

AIMS

In spite of the importance of many species of Candida as human pathogens, little is known about their ability to survive on animate and inanimate surfaces. Such information is essential in understanding the vehicles and modes of their spread, and in designing proper infection control strategies against them. The aim of this study was to generate comparative quantitative data in this regard.

METHODS AND RESULTS

The survival of one clinical isolate each of Candida albicans and C. parapsilosis on two types of hard inanimate surfaces (glass and stainless steel) and two types of fabrics (100% cotton and a blend of 50% cotton and 50% polyester) was evaluated under ambient conditions (air temperature 22 +/- 2 degrees C; relative humidity 45-62%) using quantitative test protocols. The survival of C. albicans was also assessed on human skin, using the fingerpads of adult volunteers as carriers. Each carrier surface received 10 microl of the test suspension containing a soil load to simulate body fluids. When dried on glass and stainless steel carriers, C. albicans and C. parapsilosis remained viable for at least three and 14 days, respectively. Both species could survive for at least 14 days on both types of fabric. On the skin, 20% of the viable C. albicans remained detectable one hour post-inoculation.

SIGNIFICANCE AND IMPACT OF THE STUDY

This quantitative and comparative study demonstrated the potential for, and differences in the ability of clinically significant species of Candida to remain viable on porous and non-porous inanimate surfaces as well as on human hands. These results should help in understanding the epidemiology of nosocomial infections due to Candida, and in designing better prevention and control strategies against them.

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.

Human infections caused by glycopeptide-resistant Enterococcus spp: are they a zoonosis?

Following the detection of glycopeptide-resistant enterococci (GRE) in 1986 and their subsequent global dissemination during the 1990s, many studies have attempted to identify the reservoirs and lines of resistance transmission as a basis for intervention. The eradication of reservoirs and the prevention of GRE spread is of major importance for two reasons: (i) the emergence of high-level glycopeptide resistance in invasive enterococcal clinical isolates that are already multiresistant, has left clinicians with therapeutic options that are only at the experimental stage; and (ii) the resistance genes may spread to more virulent bacterial species such as Staphylococcus aureus, Streptococcus pneumoniae and Clostridium difficile. VanA-type strains, resistant to high levels of both vancomycin and teicoplanin, are the most commonly encountered enterococci with acquired glycopeptide resistance in humans. A widespread VanA-type GRE reservoir was detected early in farm animals that were exposed to the glycopeptide growth-promoter avoparcin. Numerous studies have provided indirect evidence for the transfer of VanA-type GRE and their resistance determinants from animal reservoirs to humans. The data collected have expanded our understanding of the promiscuous nature of antibiotic resistance, and have provided the groundwork for logical decision-making with the objective of deterring the dissemination of resistant bacteria and of their resistance genes.

Nurses' experience with vancomycin-resistant enterococci (VRE)

The emergence and spread of resistant organisms, in particular vancomycin-resistant enterococci (VRE), is an issue facing all staff in acute hospitals. This study explored how nurses coped with the responsibility of halting further spread of this organism during an outbreak. VRE-positive patients were cohorted with nurses who cared for them in an endeavour to contain the spread of VRE. The majority of nurses found the situation extremely stressful because of the need to act as 'gatekeepers' responsible for educating and monitoring the practices of staff and visitors. The nurses reported that they felt they were inadequately supported, were blamed for the outbreak, and that they had an increased workload as they took on duties of other staff. The results reinforce the need for a multidisciplinary team approach to education and control of VRE, more support for nursing staff cohorted with VRE-positive patients, and stringent adherence to infection control measures by all hospital staff.

Contamination of the clinical microbiology laboratory with vancomycin-resistant enterococci and multidrug- resistant Enterobacteriaceae: implications for hospital and laboratory workers

We surveyed environmental surfaces in our clinical microbiology laboratory to determine the prevalence of vancomycin-resistant enterococci (VRE) and multidrug-resistant Enterobacteriaceae (MDRE) during a routine working day. From a total of 193 surfaces, VRE were present on 20 (10%) and MDRE were present on 4 (2%) of the surfaces tested. In a subsequent survey after routine cleaning, all of the 24 prior positive surfaces were found to be negative. Thus, those in the laboratory should recognize that many surfaces may be contaminated by resistant organisms during routine processing of patient specimens.

Vancomycin-resistant enterococci: mechanisms and clinical observations

Enterococci are not generally regarded as highly virulent bacterial pathogens. However, resistance to many antimicrobial drugs complicates treatment of enterococcal infections. Acquired resistance to high concentrations of glycopeptide antibiotics, specifically vancomycin, has exacerbated this problem. This article seeks to concisely review the mechanisms of that resistance and its effects on clinical management of enterococcal infections, as well as clinical microbiology and infection control.

Resistance to linezolid: characterization of mutations in rRNA and comparison of their occurrences in vancomycin-resistant enterococci

To assess the potential for emergence of resistance during the use of linezolid, we tested 10 clinical isolates of vancomycin-resistant enterococci (VRE) (four Enterococcus faecalis, five Enterococcus faecium, and one Enterococcus gallinarum) as well as a vancomycin-susceptible control (ATCC 29212) strain of E. faecalis. The enterococci were exposed to doubling dilutions of linezolid for 12 passes. After the final passage, the linezolid plate growing VRE contained a higher drug concentration with E. faecalis than with E. faecium. DNA sequencing of the 23S rRNA genes revealed that linezolid resistance in three E. faecalis isolates was associated with a guanine to uracil transversion at bp 2576, while the one E. faecium isolate for which the MIC was 16 microg/ml contained a guanine to adenine transition at bp 2505.

Transfer of bacteria from fabrics to hands and other fabrics: development and application of a quantitative method using Staphylococcus aureus as a model

AIMS

To develop and apply a quantitative protocol for assessing the transfer of bacteria from bleached and undyed fabrics of 100% cotton and 50% cotton + 50% polyester (poly cotton) to fingerpads or other pieces of fabric.

METHODS AND RESULTS

Test pieces of the fabrics were mounted on custom-made stainless steel carriers to give a surface area of 1 cm in diameter, and each piece seeded with about 10(5) cfu of Staphylococcus aureus from an overnight broth culture; the inoculum contained 5% fetal bovine serum as the soil load. Transfer from fabric to fabric was performed by direct contact using moist and dry fabrics. Transfers from fabrics to fingerpads of adult volunteers were tested using moist, dry and re-moistened pieces of the fabrics, with or without friction during the contact. Bacterial transfer from fabrics to moistened fingerpads was also studied. All the transfers were conducted under ambient conditions at an applied pressure of 0.2 kg cm(-2). After the transfer, the recipient fingerpads or fabric pieces were eluted, the eluates spread-plated, along with appropriate controls, on tryptic soy agar and the percentage transfer calculated after the incubation of the plates for 24 h at 37 degrees C.

CONCLUSION

Bacterial transfer from moist donor fabrics using recipients with moisture was always higher than that to and from dry ones. Friction increased the level of transfer from fabrics to fingerpads by as much as fivefold. Bacterial transfer from poly cotton was consistently higher when compared with that from all-cotton material.

SIGNIFICANCE AND IMPACT OF THE STUDY

The data generated should help in the development of better models to assess the role fabrics may play as vehicles for infectious agents. Also, the basic design of the reported methodology lends itself to work with other types of human pathogens.

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 the Rodac imprint method to selective enrichment broth for recovery of vancomycin-resistant enterococci and drug-resistant Enterobacteriaceae from environmental surfaces

We compared the Rodac imprint technique to selective enrichment broth for detecting vancomycin-resistant enterococci (VRE) and multidrug-resistant Enterobacteriaceae (MDRE) on surfaces. Rodac plates contained tryptic soy agar with 5% sheep blood, vancomycin (6 microg/ml), ceftazidime (2 microg/ml), amphotericin B (2 microg/ml), and clindamycin (1 microg/ml). Two types of broth were used: brain heart infusion (BHI) and BHI plus vancomycin (6 microg/ml) and ceftazidime (2 microg/ml) (BHIVC). Of the 46 surfaces cultured for VRE, 12 (26%) were positive. Of the 12 VRE-positive surfaces, 11 (92%) grew from Rodac, 8 (67%) grew from BHIVC, and 7 (58%) grew from BHI. A larger study is needed for MDRE, as only 4 of 43 surfaces were MDRE positive. The Rodac imprint technique successfully recovered VRE from environmental surfaces.

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.

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.

Pathogenic Mechanisms of Enterococcal Endocarditis

Enterococci are gram-positive bacteria that are now established as major nosocomial pathogens and have become increasingly important in recent years due to the development and transmission of antibiotic resistance traits. These organisms commonly cause a variety of nosocomial infections, including surgical wound infections and urinary tract infections, as well as cardiovascular infections such as bacteremia and endocarditis. Infective endocarditis is a life-threatening microbial infection of the endothelial surface of the heart, which typically occurs on heart valve tissue. The enterococci are the third most common cause of infective endocarditis, and are becoming increasingly significant in this disease. In this review, we discuss the role of enterococci in infective endocarditis and focus on the current knowledge of enterococcal virulence mechanisms, with specific reference to this disease.

Persistent contamination of fabric-covered furniture by vancomycin-resistant enterococci: implications for upholstery selection in hospitals

Vancomycin-resistant enterococci (VRE) have emerged as important nosocomial pathogens in hospitals throughout the United States. An increasing concern with respect to VRE dissemination is survival on, and potential transmission from, environmental surfaces within health care institutions. Therefore, we assessed survival of VRE on fabric chairs in an attempt to determine the optimal upholstery for the health care setting. VRE was identified on 3 of 10 seat cushions sampled, including 2 chairs in a room of a patient with known VRE. After performing simulated contamination experiments, all samples were positive at 72 hours and 1 week after inoculation. Contamination of the upholstery could be prevented by placing a sheet folded 4 times or a bath blanket folded in half on the seat cushion. In conclusion, VRE are capable of prolonged survival on fabric seat cushions and can be transferred to hands. Environmental surfaces such as chairs may serve as a potential reservoir for nosocomial transmission of VRE, and an easily cleanable, nonporous material is the preferred upholstery in hospitals.

[Problems with gram-positive bacteria: resistance in staphylococci, enterococci, and pneumococci to antimicrobial drugs]

The resistance in staphylococci, enterococci, and pneumococci is reviewed. The author also recalls the first cases, and presents an overview of the distribution of cases in the world, the genetic and molecular mechanisms of resistance, the importance in Brazil and therapeutic alternatives. The factors that contribute to the dissemination of these problem bacteria and the measures for their control are emphasized.

Experience of vancomycin-resistant enterococci in a children's hospital

Vancomycin resistant enterococci (VRE) are increasingly important nosocomial pathogens. This paper describes our experience of the epidemiology and clinical impact of VRE in the two years since the occurrence of our first case of VRE infection. Following introduction of surveillance, gastrointestinal colonization with VRE was detected in 38.3% of Haematology/Oncology and 11.1% of Hepatology/Gastroenterology patients, but in only 2.3% of children in the Paediatric Intensive Care and 1.5% of children in the Renal Unit. Only five patients with gastrointestinal colonization subsequently developed clinical infection with VRE, giving an annual incidence of 7.5%. A further six children were colonized at extra-intestinal sites. Twelve children had clinical infections with VRE, of whom three (25%) died. Contamination of bedspaces was found in association with 2/3 (66.7%) children with extraintestinal colonization and 5/7 (71.4%) children with clinical infections, compared with 6/28 (21.4%) cases of gastrointestinal colonization. In the latter group, bedspace contamination was usually associated with widespread contamination of the ward with VRE and may have been the cause rather than the result of patients acquiring VRE. Originally we employed control measures based closely on the North American HICPAC guidelines, but our control strategy has since evolved in response to epidemiological and clinical observations.

Survival of enterococci and staphylococci on hospital fabrics and plastic

The transfer of gram-positive bacteria, particularly multiresistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE), among patients is a growing concern. One critical aspect of bacterial transfer is the ability of the microorganism to survive on various common hospital surfaces. The purpose of this study was to determine the survival of 22 gram-positive bacteria (vancomycin-sensitive and -resistant enterococci and methicillin-sensitive and -resistant staphylococci) on five common hospital materials: smooth 100% cotton (clothing), 100% cotton terry (towels), 60% cotton-40% polyester blend (scrub suits and lab coats), 100% polyester (privacy drapes), and 100% polypropylene plastic (splash aprons). Swatches were inoculated with 10(4) to 10(5) CFU of a microorganism, assayed daily by placing the swatches in nutritive media, and examining for growth after 48 h. All isolates survived for at least 1 day, and some survived for more than 90 days on the various materials. Smaller inocula (10(2)) survived for shorter times but still generally for days. Antibiotic sensitivity had no consistent effect on survival. The long survival of these bacteria, including MRSA and VRE, on commonly used hospital fabrics, such as scrub suits, lab coats, and hospital privacy drapes, underscores the need for meticulous contact control procedures and careful disinfection to limit the spread of these bacteria.

Vancomycin resistance emerging in a clonal outbreak caused by ampicillin-resistant Enterococcus faecium

OBJECTIVES

To describe the first nosocomial outbreak of ampicillin-resistant Enterococcus faecium (ARE) in Norway, where a few vancomycin-resistant strains have also been identified.

METHODS

All cases of ARE and vancomycin-resistant Enterococcus faecium (VRE) diagnosed by the medical microbiological laboratories in a region inhabited by approximately 1 million people were registered. Isolates obtained during the period 1 January 1995 to 31 December 1996 were characterized by pulsed field-gel electrophoresis and the clinical data were recorded.

RESULTS

One hundred and forty-nine patients (64 males, 85 females, mean age 70.5 years) were infected with ARE. Isolates from 115 cases were genomically related to the outbreak strain. Infections included bacteremia (14), wound infections (31), urinary tract infections (97) and other infections (seven). Most had a severe underlying disease and 93% of the patients had received antibiotics for a mean time of 23 days. Twenty-four patients (16.1%) died during hospitalization. Four infections were caused by a vanB-type VRE that was genomically related to the ARE outbreak strain. The prescription rate for vancomycin was low, but an increase in vancomycin use paralleled the appearance of VRE. The highest monthly incidence rate was 2.5 per 1000 patient admissions in July 1996 declining to 0.5 in December 1996.

CONCLUSIONS

The first nosocomial outbreak caused by ARE was observed in 1995 in Norway and is still ongoing. One year after the onset, VRE occurred in wards which had a relatively high consumption of vancomycin.

Molecular epidemiology of vancomycin-resistant Enterococcus faecium in a large urban hospital over a 5-year period

To investigate the dissemination of vancomycin-resistant Enterococcus faecium (VREF) in a 728-bed tertiary-care hospital, all clinical VREF isolates recovered from June 1992 to June 1997 were typed by pulsed-field gel electrophoresis, and the transfer histories of the patients were documented. A total of 413 VREF isolates from urine (52%), wounds (16%), blood (11%), catheter tips (6%), and other sites (15%) were studied. VREF specimens mostly came from patients on wards (66%) but 34% came from patients in an intensive care unit. The number of VREF isolates progressively increased over time, with higher rates of isolation during the winter months and lower rates in the late summer months. Four distinct banding patterns were detected by pulsed-field gel electrophoresis among 316 samples (76%). Strain A (122 samples; 30%) appeared in June 1992 as the first VREF strain and was found until December 1994 throughout the entire hospital. Type B (92 samples; 22%) was initially detected in January 1994 and disappeared in November 1996. Strain C (10 samples; 2%) was limited to late 1996 and early 1997. Strain D (92 samples; 22%) showed two major peaks during March 1996 to August 1996 and January 1997 to February 1997. Unrelated strains (97 samples; 24%) appeared 1 year after the appearance of the first VREF isolate, and the numbers increased slightly over the years. Nosocomial acquisition (i.e., no known detection prior to admission and first isolation from cultures performed with samples retrieved >/=2 days after hospitalization) was found for 316 (91%) of 347 patients. Despite the implementation of Centers for Disease Control and Prevention guidelines, the proportion of related strains and high number of nosocomial cases of infection indicate a high transmission rate inside the hospital. The results imply an urgent need for stringent enforcement of more effective infection control measures.