Control of endemic glycopeptide-resistant enterococci

Legislative mandates for use of active surveillance cultures to screen for methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci: Position statement from the Joint SHEA and APIC Task Force

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

Application of molecular techniques to the study of hospital infection

Nosocomial infections are an important source of morbidity and mortality in hospital settings, afflicting an estimated 2 million patients in United States each year. This number represents up to 5% of hospitalized patients and results in an estimated 88,000 deaths and 4.5 billion dollars in excess health care costs. Increasingly, hospital-acquired infections with multidrug-resistant pathogens represent a major problem in patients. Understanding pathogen relatedness is essential for determining the epidemiology of nosocomial infections and aiding in the design of rational pathogen control methods. The role of pathogen typing is to determine whether epidemiologically related isolates are also genetically related. To determine molecular relatedness of isolates for epidemiologic investigation, new technologies based on DNA, or molecular analysis, are methods of choice. These DNA-based molecular methodologies include pulsed-field gel electrophoresis (PFGE), PCR-based typing methods, and multilocus sequence analysis. Establishing clonality of pathogens can aid in the identification of the source (environmental or personnel) of organisms, distinguish infectious from noninfectious strains, and distinguish relapse from reinfection. The integration of molecular typing with conventional hospital epidemiologic surveillance has been proven to be cost-effective due to the associated reduction in the number of nosocomial infections. Cost-effectiveness is maximized through the collaboration of the laboratory, through epidemiologic typing, and the infection control department during epidemiologic investigations.

Association between antecedent intravenous antimicrobial exposure and isolation of vancomycin-resistant enterococci

Vancomycin-resistant enterococci (VRE) have become important causes of nosocomial infections. This study evaluated the association between a variety of intravenous antimicrobial exposures and the isolation of VRE using two control groups: (1) a vancomycin-susceptible enterococci (VSE) group, to assess factors associated with development of VRE, and (2) a nonenterococci control group, to assess factors associated with positive cultures for enterococci without regard to vancomycin resistance. After adjusting for the effect of other antimicrobials, time at risk, and patient morbidity, compared to vancomycin-susceptible enterococci controls, exposures to imipenem (OR = 4.9, 95% CI = 1.6-14.1) and ceftazidime (OR = 2.6, 95% CI = 1.1-6.1) were significant predictors of VRE. When compared to nonenterococci controls, exposures to ampicillin (OR = 20.1, 95% CI = 1.5-263.1) and imipenem (OR = 5.1, 95% CI = 1.5-17.1) were significantly associated with VRE. Neither piperacillin nor vancomycin was associated with VRE compared to either control group. This study offers further evidence that the replacement of broad-spectrum cephalosporins by extended-spectrum penicillins, specifically piperacillin, may be effective in reducing VRE.

Vancomycin-resistant enterococci: 15 years and counting

We review the history of vancomycin-resistant enterococci (VRE) and propose a causal model illustrating the roles of exposure to VRE reservoirs, patient characteristics, antimicrobial exposure, and prevalence of VRE in the progression from potential VRE reservoirs to active disease in hospitalized patients. Differences in VRE colonization and VRE infection are discussed with respect to hospital surveillance methodology and implications for interventions. We further document clonal transmission of VRE in a large, urban, teaching hospital and demonstrate VRE susceptibility to a wide array of antimicrobial agents. This model can guide the identification of mutable factors that are focal points for intervention.

Persistence of vancomycin-resistant Enterococcus faecium gastrointestinal tract colonization in antibiotic-treated mice

Colonization with vancomycin-resistant Enterococcus faecium (VREF) is strongly associated with previous antimicrobial therapy. The gastrointestinal (GI) tract appears to be the major reservoir for this organism. We used antibiotic-treated Swiss Webster mice to study GI tract colonization with a characterized strain of VREF (E. faecium 228). Mice were pretreated with antibiotics in their daily drinking water and inoculated with 10(9) colony-forming units (CFU) of E. faecium 228 by oral gavage. We were able to establish persistent colonization with high concentrations of E. faecium 228 (> 8.0 log10 CFU/g of feces) in animals treated with 5 mg/ml of streptomycin plus 1 mg/ml of cefotetan. RP 59500, a streptogramin antibiotic with good in vitro activity against VREF, was administered orally in mice (n = 8) colonized with E. faecium 228. After 14 days of treatment VREF was undetectable in feces of all treated mice (< 3.0 CFU/g). Seven days after discontinuation of RP 59500, VREF was present in the feces of all animals. VREF isolates recovered after treatment remained susceptible to RP 59500. Attempts to eradicate E. faecium 228 colonization by oral administration of a vancomycin-sensitive E. faecium strain (SF68) or Lactobacillus spp. were unsuccessful as long as animals continued to receive streptomycin and cefotetan. Recovery of E. faecium 228 from cultures of livers and gallbladders in some animals with persistent GI tract colonization suggests that the organisms may also colonize the hepatobiliary system.

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.

Vancomycin-resistant enterococcus. Detection, epidemiology, and control measures

VRE have spread rapidly since their initial description in 1988. Although much has been learned about the epidemiology of VRE, further studies are needed to establish the reservoirs of the organism and the relative importance of various modes of transmission. There is considerable anecdotal evidence that nosocomial transmission of VRE can be thwarted by using measures such as those recommended by HICPAC, especially if they are implemented promptly after VRE have been introduced into hospitals.