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PubMed2002

Clinical outcomes for patients with bacteremia caused by vancomycin-resistant enterococcus in a level 1 trauma center.

To assess the degree of morbidity and mortality attributable to vancomycin resistance in enterococcal bacteremia (EB), a matched case-control study was conducted. Patients with bacteremia due to vancomycin-resistant enterococcus (VRE) were matched to control patients with bacteremia due to vancomycin-susceptible enterococcus. During 1996--2000, 65 patients with cases of clinically significant VRE bacteremia were identified, and 53 of these patients were successfully matched. In this group of patients, VRE bacteremia was found to be an independent predictor of crude mortality (odds ratio [OR], 4.0; 95% confidence interval [CI], 1.2--13.3) and the infection-related mortality rate (OR, 5.2; 95% CI, 1.4--20.0). It was also an independent predictor of the rate of clinical failure at day 7 after the onset of EB (OR, 4.6; 95% CI, 1.2--17.3) and overall clinical failure (OR, 4.3; 95% CI, 1.3--14.5) and was associated with a longer mean length of hospitalization after the onset of EB, compared with that for control patients (22.7plus minus1.88 vs. 15.9 +/- 1.7, P=.006). These observations indicate that vancomycin resistance in EB independently affects outcomes.

Analysis of Variance↗
PubMed2005

Pleiotrophic effects of 2 Enterococcus faecalis sagA-like genes, salA and salB, which encode proteins that are antigenic during human infection, on biofilm formation and binding to collagen type i and fibronectin.

BACKGROUND: We have shown previously that Enterococcus faecium SagA has broad-spectrum binding to extracellular matrix (ECM) proteins. In the present study, 2 sagA-like genes, salA and salB, were identified in Enterococcus faecalis. METHODS: We compared the salA and salB mutants; their parental strain, OG1RF; and the salB-complemented strain for binding to ECM proteins and biofilm formation. RESULTS: The salB mutant (TX5123) grew more slowly but showed greater binding (approximately 10%-20% of cells bound) to fibronectin (FN) and collagen type I (CI) than did OG1RF (approximately 1% of cells bound) (P<.001). Although TX5123 showed decreased biofilm formation in tryptic soy broth plus 0.25% glucose (TSBG) (P<.001 vs. OG1RF), a marked increase in biofilm formation was shown by TX5123 but not by OG1RF when they were grown in TSBG plus horse serum (HS) or TSBG plus FN, and the increase was coincident with increased attachment and hydrophobicity of TX5123. Complementation of the salB mutant restored the wild-type phenotypes. CONCLUSIONS: Whether SalB expression is ever sufficiently low in vivo to enhance adherence to ECM proteins or the serum-elicited increase in biofilm formation seen with the salB mutant in vitro is not currently known, but it is a potential way in which this organism could increase its adherence and biofilm formation during infection.

Bacterial Adhesion↗
PubMed2000

Evidence of delays in transferring patients with methicillin-resistant Staphylococcus aureus or vancomycin-resistant Enterococcus to long-term-care facilities.

This retrospective case-control study examined whether there was a difference in length of time awaiting long-term-care placement for patients identified as having methicillin-resistant Staphylococcus aureus or vancomycin-resistant Enterococcus compared to controls. Thirty-nine patients with methicillin-resistant Staphylococcus aureus or vancomycin-resistant Enterococcus waited for placement an average of 61 days longer than controls (P<.0002). The average number of requests for placement was 2.5 compared to 1.7 for controls (P=.015).

Aged↗
PubMed2006

Outbreak of colonization and infection with vancomycin-resistant Enterococcus faecium in a French university hospital.

An outbreak of infection with vancomycin-resistant Enterococcus faecium occurred at Hotel-Dieu Hospital (Clermont-Ferrand, France). A case-control study was performed in the infectious diseases and hematology units of the hospital. Urinary catheter use (odds ratio [OR], 12 [95% confidence interval {CI}, 1.5-90]; P<.02), prior exposure to a third-generation cephalosporin (OR, 22 [95% CI, 3-152]; P=.002), and prior exposure to antianaerobials (OR, 11 [95% CI, 1.5-88]; P<.02) were independently predictive of vancomycin-resistant Enterococcus faecium carriage.

Disease Outbreaks↗
PubMed2004

Vancomycin-resistant enterococcus (VRE) carriage and infection in intensive care units.

From July, 1997, through December, 2001, patients who were admitted to intensive care units (ICUs) were enrolled in the study of vancomycin resistance enterococcus (VRE) colonization. Among 4,538 patients admitted to the ICUs, 363 (8.0%) patients were found to have positive culture of VRE at the day of admission to the ICUs and 453 (10.0%) of patients were negative to the first day of admission but became colonized with VRE during the stay in ICU. Among 816 patients, 9 (1.1%) with VRE isolated from sterile sites were selected for further analysis. Pulsed-field gel electrophoresis (PFGE) revealed a total of four PFGE banding patterns in the colonized and infected Enterococcus faecium isolates. Six of nine 9 were found to have an identical PFGE type Ia, suggesting the circulation of an endemic strain. All of these type Ia isolates also contained two potential virulence genes, the esp and hly genes and were first identified in Asia. After the further typing of 540 isolates that were randomly selected from each month, the endemic strain was not identified before the first patient was colonized and infected with this strain in November, 1998, but was isolated from other ICU patients during each month thereafter throughout the remainder of the study period. Although colonization of VRE is the first step toward infection, a low infection rate was observed, except in patients with prolonged hospitalization and severe illness. Use of the isolation room and reminders regarding hand hygiene failed to prevent the circulation of endemic strain. Thus, the SHEA guideline (Muto et al., Infect. Control Hosp. Epidemiol. 2003;24:362-386) for preventing nosocomial transmission of VRE should be enforced.

Bacterial Proteins↗
PubMed1995

Conjugative mobilization of a vancomycin resistance plasmid by a putative Enterococcus faecium sex pheromone response plasmid.

Recent epidemiological evidence suggests that horizontal gene transfer may be an important mechanism for dissemination of vancomycin resistance. A filter mating survey of 21 VanA Enterococcus faecium isolates from The New York Hospital showed that 14 of these isolates transferred vancomycin resistance (Vmr) to the plasmid-free reference strain Enterococcus faecalis JH2-2. One isolate, E. faecium R7, was selected for further study based on its ability to transfer Vmr to strain JH2-2 in liquid culture. Analysis of the plasmid content of transconjugants revealed three general classes. The predominant class (28 of 47 transconjugants) contained two separate plasmids: pHKK702 and pHKK703. pHKK702 is a 41-kb plasmid that contains an element indistinguishable from the Vmr transposon Tn1546 and an element that hybridizes with an ermB probe from the Staphylococcus aureus erythromycin resistance transposon Tn551. pHKK703 is a 55-kb plasmid that hybridizes with probes for the sex pheromone response genes prgA, prgB, and prgX derived from the E. faecalis plasmid pCF10. The second group of transconjugants (18 of 47) contained various recombinant forms of pHKK702 and pHKK703, whereas a third transconjugant class contained only pHKK702 (1 of 47). Transconjugants that contained both pHKK702 and pHKK703 were able to efficiently transfer Vmr to recipient strains in broth or on filters. However, no transfer of Vmr was detected using the donor containing only pHKK702. The transfer of Vmr from the recombination-deficient derivative of E. faecalis JH2-2 [strain UV202(pHKK702, pHKK703)] was reduced 600-fold compared to that of JH2-2(pHKK702, pHKK703). We propose that pHKK703 functions as an E. faecium sex pheromone response plasmid that conjugatively mobilizes pHKK702, and that a major pathway for this mobilization may require donor-mediated recombination proficiency. This report provides the first example in which a plasmid containing a Tn1546-related element is conjugatively mobilized.

Anti-Bacterial Agents↗
PubMed1996

Multiplicity of genetic backgrounds among vancomycin-resistant Enterococcus faecium isolates recovered from an outbreak in a New York City hospital.

A total of 182 vancomycin-resistant Enterococcus faecium and 6 Enterococcus faecalis inpatient isolates recovered during a 2-year period (1990-1992) in a New York City hospital were analyzed by molecular fingerprinting techniques, pulsed-field gel electrophoresis (PFGE), of chromosomal SmaI digests combined with Southern hybridization using vanA and vanB2-specific DNA probes. Of the 180 isolates hybridizing with these probes, 153 carried the vanA and 27 the vanB gene. As many as 21 different PFGE types and a total of 54 subtypes were identified among the isolates, and the size of vanA and vanB-hybridizing DNA fragments also showed a wide range of sizes, from about 37 to over 280 kb (in vanA) or 140 kb (in vanB), suggesting extensive recombination, including chromosomal integration, of the resistance genes in the isolates. Close to one-third, 46, of the 148 isolates from 1992 belonged to two closely related PFGE subtype variants, each of which carried a 48 kb vanA hybridizing DNA fragment. Spread of this clone appears to be mainly responsible for the substantial increase in the prevalence of vancomycin-resistant E. faecium in early 1992.

Anti-Bacterial Agents↗
PubMed1992

Antibiotic resistance of clinical isolates of Enterococcus in Italy.

Alarming reports from various parts of the world of an increase in multiple-drug resistance among enterococci have prompted the Italian Association of Clinical Microbiologists to sponsor a nationwide study aimed at assessing the magnitude of this problem in Italy. During the last 3 months of 1988, technicians from a total of 162 general and teaching hospitals, in 16 of the 20 Italian regions and covering 89,061 beds, isolated 58,886 bacterial strains from inpatients and outpatients. Enterococci (4,879) represented 8.3% of all microorganisms identified, with Enterococcus faecalis accounting for 4,554 strains and Enterococcus faecium for the remaining 316 (6.5% of all enterococci analyzed). Enterococci were recovered most frequently from urine (62.5%) and genitourinary samples (13.7%). Only 58 strains (1.2%) were associated with bacteremia. The in vitro susceptibility of these organisms to 21 commonly used antibiotics is reported and compared with the susceptibility of isolates from a smaller epidemiologic study conducted in Italy in 1986 as well as with more recent findings from individual laboratories.

Drug Resistance, Microbial↗
PubMed1996

Risk factors associated with vancomycin-resistant Enterococcus faecium infection or colonization in 145 matched case patients and control patients.

Risk factors and mortality associated with vancomycin-resistant Enterococcus faecium (VREF) infection or colonization were examined at a tertiary care hospital by comparing 145 patients who had VREF isolates (cases) to 145 patients with vancomycin-susceptible Enterococcus faecium (VSEF) isolates (controls). The number of deaths per 100 person-days of hospitalization after diagnosis did not differ significantly between VREF patients (1.2) and VSEF patients (0.8). Multivariate analyses found that the duration of hospitalization ( > or = 7 days), intrahospital transfer between floors, use of antimicrobials (i.e., vancomycin and third-generation cephalosporins), and duration of vancomycin use ( > or = 7 days) was independently associated with VREF infection or colonization. This study, which has a large sample size, confirms some earlier observations regarding risks for VREF infection or colonization and identifies factors that may be potentially exploited to develop interventional strategies for the control of this emerging nosocomial problem.

Adolescent↗
PubMed1991

High-level gentamicin resistance in Enterococcus faecalis bacteremia.

In a retrospective analysis, patients with bacteremia due to Enterococcus faecalis with and without high-level gentamicin resistance (GRE; MIC greater than 2000 micrograms/ml) were compared. Bacteremic patients with GRE (n = 32) had significantly higher rates of nosocomial acquisition and bladder catheterization, longer hospitalizations, and more frequent prior treatment with cephalosporins than did bacteremic patients without high-level resistance (n = 19). Overall mortality was significantly associated with septic shock, high-risk source (intraabdominal, wound, respiratory tract, multiple, unknown), and polymicrobial bacteremia. Higher mortality was observed in GRE bacteremia (47%) than in bacteremia without high-level resistance (37%), but this difference was not statistically significant. For patients with monomicrobial bacteremia, low-risk source (genitourinary tract, intravascular), or treatment with antibiotics appropriate for the enterococcus, higher mortality with GRE bacteremia approached statistical significance. These results suggest that high-level resistance adversely affects survival with a pure E. faecalis bacteremia or low-risk bacteremic source. Also, response to antibiotic therapy may be diminished by high-level resistance.

Adult↗
PubMed1992

High-level resistance to gentamicin in Enterococcus faecium.

During a six-month period in a hospital in Ireland, four patients were infected (isolation from blood cultures) and two were colonized (isolation from rectal swabs) with strains of Enterococcus faecium highly resistant to gentamicin. MICs of gentamicin were greater than 1000 mg/L for all six strains, and each possessed a plasmid of approximately 50 MDa. Resistance to gentamicin was transferable by conjugation from two of the six strains, and was associated with transfer of the 50 MDa plasmid. This plasmid hybridized with a DNA probe specific for the bifunctional AAC(6')-APH(2") aminoglycoside-modifying enzyme. The mechanism of high-level gentamicin resistance in these strains appeared therefore, to be identical to that encountered in Enterococcus faecalis strains worldwide and reported in E. faecium strains in the USA.

Conjugation, Genetic↗
PubMed1995

Linkage of vancomycin and high-level gentamicin resistance genes on the same plasmid in a clinical isolate of Enterococcus faecalis.

A transferable 55-MDa plasmid which encoded resistance to both vancomycin and high concentrations of gentamicin was identified in a clinical isolate of Enterococcus faecalis. The plasmid hybridized with probes for the vanB and aac6'aph2" resistance genes. This is the first report of linkage of glycopeptide and high-level aminoglycoside resistance genes in an Enterococcus sp.

Base Sequence↗
PubMed1995

Characterization of vancomycin resistance in Enterococcus durans.

During investigation of an outbreak of vancomycin resistant Enterococcus faecium in a paediatric hospital, an isolate of Enterococcus durans resistant to vancomycin, teicoplanin, ampicillin and highly resistant to gentamicin and streptomycin was found in the stools of a patient also colonized with a strain of E. faecium with the same resistance pattern. Minimal inhibitory concentrations of vancomycin and teicoplanin were 512 and 64 mg/mL, respectively. Resistance to vancomycin as well as high-level resistance to gentamicin was transferable to an E. faecium recipient strain. Both multiresistant E. faecium and E. durans isolates as well as the transconjugant presented only one plasmid. The vanA gene was detected and localized to the high molecular weight plasmid by DNA hybridization with a vanA gene probe. Growth in vancomycin resulted in induction of an approximately 40 kDa protein visible in membrane preparations from these cells. Genetic linkage between vancomycin and gentamicin resistance genes in the same plasmid is suggested.

Anti-Bacterial Agents↗
PubMed1997

In-vitro bactericidal activity of quinupristin/dalfopristin alone and in combination against resistant strains of Enterococcus species and Staphylococcus aureus.

In-vitro activities of quinupristin/dalfopristin, a semisynthetic injectable streptogramin, and vancomycin were compared against multidrug-resistant Enterococcus faecium and Enterococcus faecalis, methicillin-susceptible Staphylococcus aureus ATCC 25923 and a methicillin-resistant S. aureus (MRSA). Combinations of quinupristin/dalfopristin and/or vancomycin with ofloxacin or gentamicin were evaluated using the chequerboard technique. The only synergy observed was that between quinupristin/dalfopristin plus vancomycin and quinupristin/dalfopristin plus gentamicin against E. faecium (FIC index < 0.5). Time-kill curves were performed over 24 h with an inoculum of 1 x 10(7) cfu/mL and clinically achievable concentrations of quinupristin/dalfopristin, vancomycin, ofloxacin and gentamicin (6, 30, 5 and 5 mg/L, respectively). In time-kill studies, combinations of quinupristin/dalfopristin plus vancomycin and quinupristin/dalfopristin plus gentamicin were additive, not synergic, against E. faecium and achieved 99.9% killing in 21.2 h and 19.6 h, respectively. None of the combination regimens suppressed the regrowth of E. faecalis. Quinupristin/dalfopristin combined with vancomycin demonstrated consistent synergy against ATCC 25923 and the MRSA, achieving 99.9% killing in 12.1 h and 11.9 h, respectively. Overall, quinupristin/dalfopristin alone demonstrated inhibitory activity against E. faecium, but not against E. faecalis, and bactericidal activity was achieved only with quinupristin/dalfopristin in combination with vancomycin or gentamicin against E. faecium. Quinupristin/dalfopristin plus vancomycin was the most potent and reliable combination against both strains of S. aureus in time-kill studies.

Anti-Bacterial Agents↗
PubMed1997

Molecular genetic analysis of high-level gentamicin resistance in Enterococcus hirae.

High-level resistance to gentamicin was studied in seven clinical isolates of Enterococcus hirae. In common with other members of the genus Enterococcus, such resistance in E. hirae was associated with single, large, conjugative plasmids. Molecular genetic analysis revealed five distinct plasmid types amongst the seven isolates. The determinant mediating high-level gentamicin resistance in E. hirae was also shown to be homologous to that already characterized for other enterococcal species.

Anti-Bacterial Agents↗
PubMed1999

Plasmid heterogeneity and identification of a Tn5281-like element in clinical isolates of high-level gentamicin-resistant Enterococcus faecium isolated in the UK.

Ten clinical isolates of high-level gentamicin-resistant (HLGR) Enterococcus faecium, collected from six hospitals throughout the UK, were studied to determine whether HLGR was attributed to widespread dissemination of a single plasmid or whether different plasmid types were implicated in the dissemination of this phenotype. HLGR was attributed to the presence of the AAC6'-APH2" bifunctional aminoglycoside modifying enzyme. The aac6'-aph2" gene was present on a 70 kb plasmid in all ten isolates. Conjugation studies indicated that the HLGR marker could transfer with varying frequency, with or without the associated 70 kb plasmid. Detailed molecular genetic analysis suggested that four of the isolates harboured a transposon similar to Tn5281, originally identified in Enterococcus faecalis strain HH22 isolated in the USA. The UK transposon, however, lacked the two symmetrically located HaeIII sites found in Tn5281. The six remaining isolates appeared to have a Tn5281-truncated structure in which the aac6'-aph2" gene is flanked by an IS256 element at the 5' end. Further studies with nine restriction endonucleases showed that the aac6'-aph2" gene was associated with two different plasmid types in E. faecium. Pulsed-field gel electrophoresis (PFGE) analysis identified three different patterns. The four E. faecium isolates harbouring the Tn5281-like structure were indistinguishable from each other, while the remaining six isolates exhibited two distinct PFGE patterns. This is the first study to indicate that there is heterogeneity among the plasmids that confer the HLGR phenotype in E. faecium isolates in the UK and to report on the presence of a transposon, similar to Tn5281, in E. faecium harbouring the aac6'-aph2" gene.

Acetyltransferases↗
PubMed2001

Effect of LY333328 against vancomycin-resistant Enterococcus faecium in a rat central venous catheter-associated infection model.

A rat central venous catheter (CVC) infection model was used to assess the activity of LY333328 against vancomycin-resistant Enterococcus faecium (VRE). Via the CVC, animals were challenged with 10(6) cfu of Enterococcus faecium with the VanA phenotype. Eight rats received a single dose of LY333328 and eight rats received saline. Seventy-five per cent of control animals had peripheral bacteraemia and 87.5% had VRE recovered from explanted CVCs at the time they were killed, as compared with 0 and 12.5%, respectively, of the LY333328-treated animals (P < 0.01). All animals in the control group had evidence of metastatic disease compared with none of the treated group (P < 0.01). LY333328 was effective against the strain of VRE tested in this model.

Animals↗
PubMed2026

Narasin used as a feed additive in conventional rearing of broilers can co-select for vancomycin-resistant Enterococcus faecium through the NarAB ionophore resistance mechanisms.

OBJECTIVES: To investigate the role of the NarAB resistance mechanism in the selection of vancomycin-resistant Enterococcus faecium (VREfm) and assess the impact of ionophore feed additives, particularly narasin, on the emergence of VREfm in broiler chickens. MATERIALS AND METHODS: Three isogenic E. faecium strains with different antimicrobial resistance determinants were created by mutagenesis and conjugation and used in a controlled animal experiment. Ross 308 broiler chickens were inoculated with either a rifampicin-resistant, a rifampicin- and vancomycin-resistant or a rifampicin-, vancomycin- and narasin-resistant strain and fed diets supplemented with selected ionophores. Bacterial populations were analysed on selective Slanetz and Bartley agar to determine the presence and selection of VREfm and other vancomycin-resistant species. Bacterial inoculation strains and isolates were whole genome sequenced for species identification and to identify genetic resistance mechanisms. RESULTS: Narasin was shown to select for VREfm in broilers, with NarAB being essential for co-selection. Intrinsically vancomycin-resistant Pediococcus acidilactici and Enterococcus gallinarum were identified as part of the broilers' vancomycin-resistant resident microbiota. Notably, among the P. acidilactici isolates that were susceptibility tested, strains resistant to both vancomycin and narasin were only found in broilers fed narasin, supporting that narasin promotes the growth of narasin-resistant populations. CONCLUSION: Narasin use in broiler feed can co-select for vancomycin-resistant bacteria, including VREfm, through the NarAB mechanism. These findings emphasize the concerns associated with the use of particular ionophores in poultry and suggest that vancomycin and narasin resistance may be more widespread in the broiler microbiota than previously recognized. Further research is needed to understand the implications for antimicrobial resistance and human health.

Animals↗