Vancomycin-resistant Enterococci Surveillance Research Articles

Politically Incorrect: Legislation Must Not Mandate Specific Healthcare Epidemiology and Infection Prevention and Control Practices

In this issue of the journal, Dr. Farr offers his perspective on the recent position statement from the Joint SHEA and APIC Task Force regarding legislative mandates for use of active surveillance cultures to screen for methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). The position statement specifically addresses the issue of whether the use of MRSA and VRE surveillance cultures in healthcare settings should be mandated by legislation. It does not attempt to address whether or not, when, or for whom active surveillance cultures should be performed. A broad range of experts and the Boards of Directors of the Society for Healthcare Epidemiology (SHEA) and the Association of Professionals in Infection Control (APIC) reviewed this position statement, which summarizes the effectiveness of active surveillance culturing as it pertains to potential legislation. Both Boards agree the position statement represents a well-reasoned, systematic, and fair review of the literature. Of course, no single document, group, or individual should ever be viewed as having the final word on this or any subject. Thoughtful debate regarding the scientific evidence, when conducted in a professional and constructive manner, is a critical and necessary step in the translation of research and clinical observations into bedside practices. Such debate should also lead to a research agenda that will help fill gaps in knowledge that become apparent in the discussion.

Vancomycin-Resistant Enterococcus (VRE) Colonization Is Associated with a High Rate of Bacteremia and Early Mortality in Transplant/Leukemia Patients.

Background: Vancomycin-resistant enterococci (VRE) have become increasingly important nosocomial pathogens in very ill and immunocompromised hospitalized patients (pts). Due to an increase in VRE clinical cultures including bacteremias on our institutional transplant/leukemia service in early 2004, active surveillance for VRE among this population was instituted in June 2004. We describe here the incidence and prevalence of VRE colonization and infection in this population over a two year study period, as well as selected pt demographics and mortality associated with VRE bacteremia.Methods: Between June 2004 and July 2006, active surveillance for VRE on inpatients on the transplant/leukemia service was performed by acquiring perirectal or stool swabs for VRE culture on hospital admission and on a weekly basis while inpatient. Acquisition of VRE was determined to be nosocomial if the initial culture was negative followed by a positive culture at any time during the hospital stay. Multiple sequential interventions as recommended by the Society for Healthcare and Epidemiology (SHEA) guidelines were implemented. Pt census data and daily isolation indicators were used to help determine VRE colonization rates and the prevalence of VRE on the units. Chart reviews were performed to obtain information on clinical pts related features and mortality of bacteremic pts.Results: Nineteen percent (193/1019) of pts screened were colonized with VRE with the monthly nosocomial colonization rate ranging from 2–12% (rate/1000 patient days). Eighteen percent (31/189) of pts newly colonized with VRE became bacteremic, including 7/31 who had bacteremia as their primary presentation. Of the bacteremic pts, 24 (77.4%) died at a median of 20 days (range 2–208 days), 18 (75%) dying during their bacteremic hospitalization of multiple causes. Sixteen had acute leukemia, 11 non-Hodgkin's lymphoma, and 3 other malignancies. Eighteen bacteremic pts had undergone allogeneic transplant & 5 autologous transplant. Fourteen of 18 allogeneic transplant pts had active GVHD and all 18 were on immune suppression therapy. Of all allogeneic transplants performed during the study period, 13% (18/140) were complicated by VRE bacteremia. Sixteen bacteremic pts required ICU stays, while 6 had C. difficile colitis and 5 mucositis during the same hospital stay. SHEA recommended interventions instituted at various times (e.g. enhanced contact and barrier precautions for colonized pts, “supercleans” of unit, written communication to staff, pts and families, gloving for all pt contacts) did not have a durable effect on these rates. However, the ratio of new nosocomial cases/overall prevalence of VRE in the units decreased 20% over the study period, suggesting some measure of control despite high colonization pressure. Assessment of response to intensive control strategies as well as delineation of risk factors for bacteremia and death in this population are ongoing and will be presented.Conclusion: Despite application of standardized guidelines for VRE control, affecting a marked and durable decrease in endemic VRE colonization on a complicated transplant/leukemia service is difficult. VRE bacteremia following colonization in transplant/leukemia pts is common and is associated with early mortality. VRE control remains critical, and new modalities and approaches are essential.

Emergence of VanB phenotype-vanA genotype in vancomycin-resistant enterococci in Brazilian hospital

In Brazil, vancomycin-resistant enterococci (VRE) have been reported as nosocomial pathogens since 1998. Recently, in a VRE surveillance in a hospital, we detected two Enterococcus faecalis isolates with vanA genotype and susceptible to teicoplanin. This is the first report of VanB phenotype-vanA genotype enterococci isolated from humans in Brazil.

New Investigator Award

BACKGROUND/OBJECTIVES: The Special Care Nursery (SCN) notified Infection Control that two infants who had been transferred to a children's hospital were positive for Vancomycin-Resistant Enterococcus (VRE) upon admission screening. Active surveillance for enteric VRE was performed on the remaining SCN infants at our facility. METHODS: All infants in the SCN had stool sent for VRE culture. Observations were conducted to assess infection control practices. A multidisciplinary team was formed consisting of the Infection Control Practitioners, Medical Director of Infection Control, Chief Medical Officer, Medical Director of SCN, SCN nurse manager, SCN clinical nurse educator, Director of Women and Infant's Services, Housekeeping and Microbiology. Interventions consisted of immediate implementation of contact precautions, enhanced hand hygiene practices, cohorting of infants and nursing staff, and extensive cleaning of the SCN. Parents of VRE positive infants entered and left the SCN cohort area through a separate door. Education was provided to nursing staff, physicians and parents of SCN infants regarding modes of VRE transmission and means of prevention, hand hygiene, environmental contributions to VRE transmission, environmental cleanliness and cohorting measures. New admissions were geographically cohorted to a separate ancillary nursery until all VRE positive infants had been discharged home. RESULTS: Eight of the eleven (11) remaining SCN infants were positive for VRE by stool culture for a total of 10/13 (77%) VRE positive infants. After the interventions were implemented, no new cases of VRE were identified. Since the cluster, one hundred twelve (112) infants have been screened weekly during SCN admission and upon discharge home. To date, eighty-five (85) infants have been screened with at least one (1) stool culture, seventeen (17) received two (2) screens and ten (10) received three (3) screens. All screens have been negative for a statistically significant decrease in proportion of infants colonized with VRE admitted after the intervention (10/13 versus 0/112; p CONCLUSIONS: A multidisciplinary intervention consisting of active surveillance screening, cohorting, contact precautions, environmental cleaning and education resulted in rapidly abating this outbreak.

Three Surveillance Strategies for Vancomycin-Resistant Enterococci in Hospitalized Patients: Detection of Colonization Efficiency and a Cost-Effectiveness Model

To evaluate the cost-effectiveness and detection sensitivity associated with three active surveillance strategies for the identification of patients harboring vancomycin-resistant enterococci (VRE) to determine which is the most medically and economically useful. Culture for VRE from 200 consecutive stool specimens submitted for Clostridium difficile culture. Following this, risk factors were assessed for patients whose culture yielded VRE, and a cost-effectiveness evaluation was performed using a decision analytic model with a probabilistic analysis. A 688-bed, tertiary-care facility in Chicago, Illinois, with approximately 39,000 annual admissions, 7,000 newborn deliveries, 56,000 emergency department visits, and 115,000 home care and 265,000 outpatient visits. All stool specimens submitted to the clinical microbiology laboratory for C. difficile culture from hospital inpatients. From 200 stool samples submitted for C. difficile testing, we identified 5 patients with VRE in non-high-risk areas not screened as part of our routine patient surveillance. Medical record review revealed that all 5 had been hospitalized within the prior 2 years. Three of 5 had a history of renal impairment. The strategy that would involve screening the greatest number of patients (all those with a history of hospital admission in the prior 2 years) resulted in highest screening cost per patient admitted (dollars 2.48), lower per patient admission costs (dollars 480), and the best survival rates. An expanded VRE surveillance program that encompassed all patients hospitalized within the prior 2 years was a cost-effective screening strategy compared with a more traditional one focused on high-risk units.

Impact of a formulary switch from ticarcillin-clavulanate to piperacillin-tazobactam on colonization with vancomycin-resistant enterococci

The prevalence of vancomycin-resistant enterococci (VRE) is increasing, despite infection control measures. Limited data link ticarcillin-clavulanate to higher VRE prevalence. Active surveillance for VRE was conducted before and after a formulary switch from ticarcillin-clavulanate to piperacillin-tazobactam. Rectal swabs were obtained serially in 863 adult patients admitted to intensive care units (ICUs) between November 1, 2000 and September 30, 2004. In the postswitch period, 38 of 497 (7.6%) patients acquired VRE versus 42 of 366 (11.5%) patients in the preswitch period. Survival analysis showed an overall hazard ratio (HR) of .68 postswitch versus preswitch ( P = .07), with the greatest change in the surgical ICU (HR = .17, P = .006). Multivariate analysis showed an overall HR = .51 ( P = .004). Hospital-wide, nonstool VRE clinical cultures fell from 39 (.58/1000 patient days) in the 10-month preswitch period to 27 (.33/1000 patient days) in the 12-month postswitch period. Infection control practices and use of other antibiotics remained stable. VRE acquisition appeared to decrease in association with a formulary change from ticarcillin-clavulanate to piperacillin-tazobactam.

Emergence of vancomycin-resistant enterococci in San Francisco Bay area hospitals during 1994 to 1998.

To determine the magnitude of vancomycin-resistant enterococci (VRE) in three counties in the San Francisco Bay area. Active laboratory-based surveillance for VRE from January 1995 through December 1996 and a laboratory-based and hospital-based questionnaire survey for 1993 to 1994 and 1997 to 1998. All 33 general acute care hospitals in three counties in the San Francisco Bay area. Laboratories and infection control professionals serving these hospitals, and staff of the California Emerging Infections Program. The number of hospitals reporting 1 or more patient clinical VRE isolates was 1 (3%) in 1993, 7 (21%) in 1994, 31 (94%) in 1995, and 33 (100%) in 1996 to 1998. The number of patient isolates increased from 1 in 1993 to 24 in 1994, 176 in 1995, 429 in 1996, 730 in 1997, and 864 in 1998. Most VRE isolates in 1995 and 1996 were from urine and were not associated with serious clinical disease. However, the number of isolates from blood increased from 9 (6% of total) in 1995 to 44 (12% of the total) in 1996, 90 (14%) in 1997, and 100 (13%) in 1998. Our data document the rapid emergence and increase of VRE in all hospitals in three counties in the San Francisco Bay area during 1994 to 1998. Infection control measures for VRE together with antibiotic utilization programs should be implemented to limit further spread.

Incidence and clinical complications of vancomycin-resistant enterococcus in pediatric stem cell transplant patients.

Vancomycin-resistant enterococcus (VRE) are increasingly important pathogens in stem cell transplant (SCT). In all, 61 pediatric SCT patients had surveillance stool cultures for VRE between July 1999 and November 2002. When VRE was identified, the patients were placed on strict contact isolation. VRE was detected in 15 patients (24.6%). The median age was 3.6 years (range 0.6-18.5 years). Of the 15, 13 (87%) received an allogeneic transplant (six unrelated and seven related). Five of the 15 (33%) colonized patients developed VRE bacteremia. The bacteremia resolved in all five patients after therapy with quinupristin/dalfopristin; three patients required central line removal. Four patients died (38-153 days) post-SCT due to relapse or transplant complication not related to VRE. Of the 11 surviving patients, seven cleared the colonization at a median of 144 days (range 61-198 days) postcolonization. Four patients remain colonized at 68-702 days after the first positive culture. Intestinal colonization with VRE occurred commonly in pediatric SCT patients. Although the morbidity from VRE was not substantial, transplant patients were colonized for prolonged periods. Our results indicate that surveillance for VRE is an effective way to identify colonized patients and may lead to a decrease in transmission to other patients.

Co-carriage rates of vancomycin-resistant Enterococcus and extended-spectrum beta-lactamase-producing bacteria among a cohort of intensive care unit patients: implications for an active surveillance program.

To assess the co-colonization rates of extended-spectrum beta-lactamase (ESBL)-producing bacteria and vancomycin-resistant Enterococcus (VRE) obtained on active surveillance cultures. Prospective cohort study. Medical and surgical intensive care units (ICUs) of a tertiary-care hospital. Patients admitted between September 2001 and November 2002 to the medical and surgical ICUs at the University of Maryland Medical System had active surveillance perirectal cultures performed. Samples were concurrently processed for VRE and ESBL-producing bacteria. Of 1,362 patients who had active surveillance cultures on admission, 136 (10%) were colonized with VRE. Among these, 15 (positive predictive value, 11%) were co-colonized with ESBL. Among the 1,226 who were VRE negative, 1,209 were also ESBL negative (negative predictive value, 99%). Among the 1,362 who had active surveillance cultures on admission, 32 (2%) were colonized with ESBL. Among these, 15 (47%) were co-colonized with VRE. Of the 32 patients colonized with ESBL, 10 (31%) had positive clinical cultures for ESBL on the same hospital admission. For these 10 patients, the surveillance cultures were positive an average of 2.7 days earlier than the clinical cultures. Patients who are colonized with VRE can also be co-colonized with other antibiotic-resistant bacteria such as ESBL-producing bacteria. Our study is the first to measure co-colonization rates of VRE and ESBL-producing bacteria. Isolating VRE-colonized patients would isolate 47% of the ESBL-colonized patients without the need for further testing. Hence, active surveillance for VRE should also theoretically diminish the amount of patient-to-patient transmission of ESBL-producing bacteria.

Vancomycin-resistantEnterococcus faecalisin Serbia

To the Editor: First isolated in France (1), vancomycin-resistant enterococci (VRE) have become pathogens of major importance, particularly in the United States (2). Infections due to VRE are still uncommon in most European countries (3). We report the first isolation of high-level vancomycin-resistant Enterococcus faecalis in Serbia. A 55-year-old woman was admitted to the Clinic for Cardiovascular Diseases, Belgrade, on April 1, 2002, for aortobifemoral bypass surgery. Three weeks after she was admitted to the hospital, an infection developed in the surgical wound and treatment with sulfamethoxazole-trimethoprim (160/800 mg q 12 h) was empirically introduced. Bacteriologic analysis of the wound swab sample showed a methicillin-resistant strain of Staphylococcus aureus, a multiresistant strain of Acinetobacter sp., a commonly susceptible strain of Enterococcus sp., and a VRE strain. According to the results of susceptibility testing, imipenem (1 g q 6 h) was added to the patient’s treatment protocol. VRE were not isolated from subsequent wound samples or any other sample submitted for microbiologic analysis. The patient was discharged at the end of the 14-day treatment period. The isolate was identified as E. faecalis by biochemical characterization, as recommended by Facklam and Collins (4) and confirmed by API 20 Strep (bioMerieux, Marcy-l’Etoile, France). Susceptibility testing, performed by the disk diffusion method, showed that the isolate was resistant to vancomycin, teicoplanin, gentamicin, streptomycin, tetracycline, and ciprofloxacin, while susceptible to ampicillin, amoxicillin, amoxicillin and clavulanic acid, and imipenem. Resistance to vancomycin, teicoplanin, gentamicin, and streptomycin was confirmed by the broth dilution method, according to the National Committee for Clinical Laboratory Standards (NCCLS) recommendations (5). The obtained MICs were 256 μg/mL for vancomycin, 64 μg/mL for teicoplanin, >4,000 μg/mL for gentamicin, and >2,000 μg/mL for streptomycin. This phenotype, with high-level resistance to vancomycin and teicoplanin, is typical for the vanA genotype (2). The strain was subsequently genotyped by pulsed-field gel electrophoresis, using previously described methods (6). The presence of the vanA gene was confirmed by polymerase chain reaction assay, according to a previously described procedure (7). E. faecium EF228 was used as the positive control. The enterococci are among the most frequent causes of nosocomial infections, particularly in intensive care units, and present a major therapeutic challenge (2). While the emergence of VRE strains in the United States is probably associated with extensive use of vancomycin, the occurrence of VRE in Europe is possibly due to application of avoparcin (glycopeptide analog) as a growth promoter in animal husbandry (3). However, avoparcin has not been used in Serbia, and vancomycin application has been restricted to hospitalized patients and quite limited due to its high cost. Thus, emergence of VRE strains in Serbia has not been likely. The origin of this VRE isolate is unknown: the strain may have been imported or may have originated from the hospital environment. The first prospective pan-European VRE surveillance study (January–April 1997) showed VanA-VRE strains in only eight European countries, with isolates numbering from one to four per country (3). No epidemiologic relations were established among the VanA isolates, and only 2 out of 18 isolates (11%) were identified as E. faecalis (3). Since our patient-case had no history of travel outside Serbia, we assumed that the VRE isolate originated from the hospital environment. However, a study investigating the occurrence of VRE strains in Belgrade, the capital of Serbia, detected no such isolates in five different hospitals (8). Although the study did not analyze samples from the Clinic for Cardiovascular Diseases, it did include samples from the Clinic for General Surgery, which is located within the same building. The susceptibility of 191 isolates of enterococci to vancomycin was tested by agar dilution method according to NCCLS recommendations. Of the 191 isolates, 159 were classified as susceptible and 32 as intermediately susceptible. This report of the first isolation of VRE in Serbia, as well as the previously shown presence of enterococci displaying intermediary susceptibility to vancomycin, provides the rationale for future active screening for VRE in hospital environments in the region.

Applying social and behavioral theory as a template in containing and confining VRE.

Infection control professionals play several important roles--surveyors, educators, and ultimately change agents--in the identification and prevention of nosocomial infections in hospitals. The medical and surgical intensive care units (ICUs) in a large inner-city teaching hospital experienced an increased patient colonization rate with vancomycin-resistant enterococcus (VRE). Intervening in this problem required a multifaceted approach to control the spread of VRE and to change behavior by shifting social norms at multiple levels throughout the ICU community. The success of the interventions could be best explained by applying the use of several behavioral science models. The Ecological Model of Behavior Change, the Health Belief Model, and Social Cognitive Theory can be applied and are consistent with the successful interventions. This multifaceted approach to intervening in this problem consists of five levels of influence: (1) intrapersonal or individual factors, (2) interpersonal factors, (3) institutional factors, (4) community factors, and (5) public factors. We implemented educational inservices and developed references, policies, and programs directed at each of the five levels of influence. The Health Belief Model and Social Cognitive Theory were employed for intervention, and behavior change was based on modeling, observational learning, and vicarious reinforcement. Within six months of initial implementation, the number of positive VRE surveillance cultures and positive clinical isolates decreased significantly in both the medical and surgical ICUs. Two years later, there continues to be a marked reduction of VRE.

Surveillance strategies and impact of vancomycin-resistant enterococcal colonization and infection in critically ill patients.

To determine the optimal site and frequency for vancomycin-resistant enterococci (VRE) surveillance to minimize the number of days of VRE colonization before identification and subsequent isolation. The increasing prevalence of VRE and the limited therapeutic options for its treatment demand early identification of colonization to prevent transmission. The authors conducted a 3-month prospective observational study in medical and surgical intensive care unit (ICU) patients with a stay of 3 days or more. Oropharyngeal and rectal swabs, tracheal and gastric aspirates, and urine specimens were cultured for VRE on admission to the ICU and twice weekly until discharge. Of 117 evaluable patients, 23 (20%) were colonized by VRE. Twelve patients (10%) had VRE infection. Of nine patients who developed infections after ICU admission, eight were colonized before infection. The rectum was the first site of colonization in 92% of patients, and positive rectal cultures preceded 89% of infections acquired in the ICU. This was supported by strain delineations using pulsed-field gel electrophoresis. Twice-weekly rectal surveillance alone identified 93% of the maximal estimated VRE-related patient-days; weekly or admission-only surveillance was less effective. As a test for future VRE infection, rectal surveillance culture twice weekly had a negative predictive value of 99%, a positive predictive value of 44%, and a relative risk for infection of 34. Twice-weekly rectal VRE surveillance of critically ill patients is an effective strategy for early identification of colonized patients at increased risk for VRE transmission, infection, and death.

Epidemiological study of vancomycin-resistant enterococcus isolated from a single medical university hospital in Japan.

Since 1998 more than 50 reports have described the isolation of high-level vancomycin-resistant enterococci (VRE) in Japan. Here, we report on our clinical isolates of VRE and an epidemiological study carried out using chemical and genetic techniques. VRE isolates were screened for high resistance to vancomycin (VCM) with a cutoff value of 6 microg/ml and VCM-resistant gene was confirmed by polymerase chain reaction (PCR). The epidemiological studies used pulsed-field gel electrophoresis (PFGE) and plasmid analysis. Six strains of VRE were isolated from six different patients on two wards during a 3-months period. All of the isolates possessed vanA on their plasmid, and the isolates were divided into two similar groups. Furthermore, three different patterns were defined by PFGE. Although all of the asymptomatic carriers were hospitalized for more than 3 months, we were able to prevent an outbreak of VRE in our hospital by using our guidelines for infection control, which are stricter than those for methicillin-resistant Staphylococcus aurens. From the results of this epidemiological study, we propose that there was a possibility of contamination in this hospital, and that three of the six isolates may have acquired vanA independently. In this study, we demonstrated that infection control, according to appropriate prevention guidelines, as well as regular surveillance for VRE, are essential for designing interventions to prevent the further spread of VRE.

VRE in the Republic of Ireland: clinical significance, characteristics and molecular similarity of isolates

There have been increasing reports worldwide of vancomycin resistant enterococci (VRE) since they were first noted over ten years ago. This study sought to investigate the clinical significance of VRE in Ireland and to compare the phenotypic, genotypic and molecular characteristics of isolates recovered from patients in different institutions. The relative contribution of inter-hospital transmission of strains to the dissemination of VRE in Ireland was assessed. Hospital surveillance for VRE is not well established in Ireland. The organism has been detected in seven hospitals. Detection has been predominantly in oncology inpatients in large tertiary referral hospitals in the Dublin metropolitan area in whom strains generally represent asymptomatic gastrointestinal tract colonization. The predominant species is E. faecium with the Van A resistance phenotype. Twenty-seven (87) of 31 isolates from one unit were shown to be of the same or closely related strain as were 10 (63%) of 16 from another unit, indicating significant nosocomial transmission within institutions. There was no evidence for inter-hospital transmission of VRE. VRE is established in Ireland and nosocomial transmission readily occurs. Regular surveillance for VRE is indicated in high-risk populations in large institutions, specific risk factors for the acquisition of VRE need to be defined and optimal control and preventative strategies need to he instituted to detect and preempt the spread of this organism.

Direct detection of vanA and vanB genes in clinical specimens for rapid identification of vancomycin resistant enterococci (VRE) using multiplex PCR

Surveillance for vancomycin resistant enterococci (VRE) by culture can be labour intensive and time consuming. We have developed a multiplex polymerase chain reaction (MPCR) which can be performed directly on the clinical specimen. The assay allows sensitive detection of enterococci with vanA - and vanB -mediated resistance to vancomycin. DNA was purified from stool and rectal specimens using the XTRAXTMDNA Extraction Kit (Gull Labs). Multiplex PCR amplifiedvanA and vanB targets were detected using a microtiter plate EIA. Two-hundred specimens were tested by routine culture and MPCR. Culture identified 44 VRE isolates and MPCR detected 38 of the 44 culture positives. Multiplex PCR detected three additional positive VRE specimens missed by culture for a sensitivity and specificity of 86·4 and 98·1%, respectively. When the presence of PCR inhibitors was addressed in the six culture positive/MPCR negative specimens, four additional VRE positive specimens were detected. Performing MPCR on the original specimens and on a 1:10 dilution of all specimens to minimize the effect of inhibitors gave a sensitivity and specificity of 95·5 and 98·1%, respectively. Multiplex PCR with confirmation by microtiter plate hybridization could be completed in 8 h compared with 24–48 h required for culture.

Failure to eradicate vancomycin-resistant enterococci in a university hospital and the cost of barrier precautions.

To describe the effect of infection control interventions on the incidence of vancomycin-resistant enterococci (VRE), the utility of pharyngeal cultures for surveillance for VRE colonization, and the cost of barrier precautions. Evaluation of the occurrence of VRE infection or colonization, rates of vancomycin use, results of surveillance cultures before and after interventions, and the cost of increased barrier precautions. University of Massachusetts Medical Center, a 347-bed tertiary-care teaching hospital with eight intensive-care units, one burn unit, and one bone marrow transplant unit. Patients in the intensive-care units and staff who were involved with patients colonized or infected with VRE. Infection control interventions included placement of patients with VRE in private rooms, strict contact isolation, cohorting of patient and nursing staff, prohibiting of equipment sharing, and monitoring of compliance with the vancomycin restriction policy, with hand washing, and of the adequacy of environmental cleaning. Both rectal and pharyngeal cultures were obtained from patients at the beginning of the outbreak, and the utility of pharyngeal cultures was evaluated. The cost of barrier precautions was estimated by comparing the cost of glove and gown use before and after the outbreak began. The interventions decreased the number of new cases of VRE, but total eradication of VRE was not achieved. Compliance with the room-cleaning protocol was 91% (141/155 observations). Hand washing following interaction with patients who were not in isolation was 51%, vs 100% for patients in isolation. Overall, handwashing compliance was 71% (319/449): 56% (130/231) for physicians and 86% (187/218) for nurses (P<.0001). The mean number of doses of vancomycin dispensed per 1,000 patient days decreased from 145 to 114 per 1,000 patient days (P<.001). Compliance with vancomycin-use guidelines was 85%. Forty-six (77%) of 60 surveillance rectal swabs yielded enterococci, as compared to only 4 (11%) of 36 pharyngeal cultures (P<.0001). Expenses on glove and gowns alone increased by over $11,000 per year since the epidemic began. Implementation of the various infection control measures did not eradicate VRE cases from the hospital. Rectal cultures were more useful than pharyngeal cultures for surveillance of VRE. Controlling VRE epidemics can be costly.

Detection of vancomycin-resistant enterococci in fecal samples by PCR.

Surveillance cultures for vancomycin-resistant enterococci (VRE) are time-consuming and expensive for the laboratory to perform. Therefore, we investigated the use of PCR as an alternative method of detecting and identifying VRE directly in fecal samples. PCR primers directed to vanA, vanB, vanC1, vanC2, and enterococcal ligase genes were used to detect and identify VRE in fecal material obtained by rectal or perirectal swabbing. Although PCR-inhibitory substances were present in DNA prepared directly from the swabs, the inhibitory substances could be reduced by processing the nucleic acid with two commercially available DNA preparation columns. Fecal material from 333 swabs was cultured on several selective agar media before and after broth enrichment. DNA was extracted from the fecal material and was analyzed by PCR. By using all four primer sets, only 59 (67.8%) of the samples were positive for vanA. However, after retesting the negative samples with only the vanA primer set, 77 (88.5%) of 87 specimens that were culture positive for Enterococcus faecium containing vanA were positive by PCR. One specimen was PCR positive for the vanA gene but culture negative for enterococci. The specificity of the vanA assay was 99.6%. PCR analysis of enrichment broth samples with all four primers sets after 15 to 18 h of incubation detected 74 (85.1%) of the 87 culture-positive specimens. The specificity of the vanA assay after the enrichment step was 100%. No vanB-containing enterococci were recovered by culture. Since 16 samples can be tested by PCR in 4 h (including electrophoresis), identification of VRE is possible within 8 h of specimen submission at a cost of approximately $10.12/assay. Thus, PCR may be a cost-effective alternative to culture for surveillance of VRE in some hospitals.

Emergence of vancomycin resistance in the genus Streptococcus: characterization of a vanB transferable determinant in Streptococcus bovis

Streptococcus bovis NEM760 was isolated from a stool swab collected on admission from a patient as surveillance for vancomycin-resistant enterococci. Strain NEM760 was identified as S. bovis by conventional biochemical methods and partial sequence analysis of its 16S rRNA. This strain was resistant to a low level of vancomycin (MIC, 64 micrograms/ml) but was susceptible to teicoplanin (MIC, 1 micrograms/ml), and vancomycin induced resistance to both glycopeptides. The presence of a vanB-related gene in NEM760 was demonstrated in a PCR assay which enabled specific amplification of a 635-hp internal segment of vanB. Sequence analysis of the corresponding PCR product revealed that it was highly homologous (96% identity) to the prototype vanB sequence of Enterococcus faecalis V583. The VanB resistance of determinant of S. bovis NEM760 was transferred by conjugation to E. faecalis and Enterococcus faecium at a similar frequency of 2 x 10(-5) per donor. SmaI-digested genomic DNAs of independently obtained transconjugants of E. faecalis and E. faecium were analyzed by pulsed-field gel electrophoresis and Southern hybridization with a vanB DNA probe. The electrophoretic and hybridization patterns obtained with all transconjugants of the same species were indistinguishable and revealed vanB-containing chromosomal insertions of approximately 100 kb. These results suggest that the genes mediating VanB-type resistance in S. bovis NEM760 are part of large transferable genetic elements. The results presented in the report demonstrate for the first time the role of streptococci in the dissemination of vancomycin resistance among gram-positive bacteria.