The current MLVA typing scheme for Enterococcus faecium is less discriminatory than MLST and PFGE for epidemic-virulent, hospital-adapted clonal types

An epidemiological and molecular study regarding the spread of vancomycin-resistant Enterococcus faecium in a teaching hospital in Bogotá, Colombia 2016

Background

Enterococcus faecium is ranked worldwide as one of the top ten pathogens identified in healthcare-associated infections (HAI) and is classified as one of the high priority pathogens for research and development of new antibiotics worldwide. Due to molecular biology techniques’ higher costs, the approach for identifying and controlling infectious diseases in developing countries has been based on clinical and epidemiological perspectives. Nevertheless, after an abrupt vancomycin-resistant Enterococcus faecium dissemination in the Méderi teaching hospital, ending up in an outbreak, further measures needed to be taken into consideration. The present study describes the vancomycin-resistant Enterococcus faecium pattern within Colombian’s largest installed-bed capacity hospital in 2016.

Methods

Thirty-three vancomycin-resistant Enterococcus faecium isolates were recovered during a 5-month period in 2016. Multilocus variable-number tandem-repeat analysis was used for molecular typing to determine clonality amongst strains. A modified time-place-sequence algorithm was used to trace VREfm spread patterns during the outbreak period and estimate transmission routes.

Results

Four clonal profiles were identified. Chronological clonal profile follow-up suggested a transitional spread from profile “A” to profile “B”, returning to a higher prevalence of “A” by the end of the study. Antibiotic susceptibility indicated high-level vancomycin-resistance in most isolates frequently matching vanA gene identification.

Discussion

Transmission analysis suggested cross-contamination via healthcare workers. Despite epidemiological control of the outbreak, post-outbreak isolates were still being identified as having outbreak-related clonal profile (A), indicating reduction but not eradication of this clonality. This study supports the use of combined molecular and epidemiological strategies in an approach to controlling infectious diseases. It contributes towards a more accurate evaluation of the effectiveness of the epidemiological measures taken regarding outbreak control and estimates the main cause related to the spread of this microorganism.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-3877-7) contains supplementary material, which is available to authorized users.

Invasive enterococcal infections in Poland: the current epidemiological situation

The aim of this study was to investigate human invasive isolates of enterococci, obtained through prospective surveillance in Poland. The consecutive enterococcal isolates were collected in 30 hospitals between May 2010 and June 2011, and studied by species identification, antimicrobial susceptibility testing and, for Enterococcus faecium by detection of markers specific for the hospital meroclone, multilocus VNTR analysis (MLVA) and multilocus sequence typing (MLST). Additionally, the genomic difference regions (GDRs) characteristic for lineage 78 were searched by PCR. Among 259 isolates, a nearly equal number of Enterococcus faecalis (n = 140; 54.1 %) and E. faecium (n = 112; 43.2 %) was found. The observed 14-day mortality rate of infected patients reached 18.1 %. All isolates were susceptible to linezolid and daptomycin. High-level aminoglycoside resistance occurred in over 50 % of isolates. Vancomycin resistance mediated by vanA or vanB was detected in 7.1 % of E. faecium; 71.4 % of isolates were multidrug resistant. E. faecium isolates ubiquitously carried molecular markers of hospital-associated meroclone (IS16, esp(Efm), intA of ICEEfm1) and multilocus sequence typing showed the domination of representatives of lineages 78 and 17/18 (52.7 % and 46.4 %, respectively). Isolates of lineage 78 were significantly enriched in all the GDRs studied. The recent spread of E. faecium from this lineage contributed to the observed increase of E. faecium in enterococcal invasive infections in hospitals in Poland.

Core Genome Multilocus Sequence Typing Scheme for High-Resolution Typing of Enterococcus faecium

Enterococcus faecium , a common inhabitant of the human gut, has emerged in the last 2 decades as an important multidrug-resistant nosocomial pathogen. Since the start of the 21st century, multilocus sequence typing (MLST) has been used to study the molecular epidemiology of E. faecium . However, due to the use of a small number of genes, the resolution of MLST is limited. Whole-genome sequencing (WGS) now allows for high-resolution tracing of outbreaks, but current WGS-based approaches lack standardization, rendering them less suitable for interlaboratory prospective surveillance. To overcome this limitation, we developed a core genome MLST (cgMLST) scheme for E. faecium . cgMLST transfers genome-wide single nucleotide polymorphism (SNP) diversity into a standardized and portable allele numbering system that is far less computationally intensive than SNP-based analysis of WGS data. The E. faecium cgMLST scheme was built using 40 genome sequences that represented the diversity of the species. The scheme consists of 1,423 cgMLST target genes. To test the performance of the scheme, we performed WGS analysis of 103 outbreak isolates from five different hospitals in the Netherlands, Denmark, and Germany. The cgMLST scheme performed well in distinguishing between epidemiologically related and unrelated isolates, even between those that had the same sequence type (ST), which denotes the higher discriminatory power of this cgMLST scheme over that of conventional MLST. We also show that in terms of resolution, the performance of the E. faecium cgMLST scheme is equivalent to that of an SNP-based approach. In conclusion, the cgMLST scheme developed in this study facilitates rapid, standardized, and high-resolution tracing of E. faecium outbreaks.

Characterization of Enterococcus faecium with macrolide resistance and reduced susceptibility to quinupristin/dalfopristin in a Japanese hospital: detection of extensive diversity in erm(B)-regulator regions

Cross-resistance to macrolide, lincosamide, and streptogramin B (MLSB) antibiotics is mainly mediated by the erm (erythromycin ribosome methylation) genes that encode 23S rRNA methylases in enterococi, and various mechanisms are involved in the streptogramin B resistance. Prevalence of MLSB resistance and its genetic mechanisms were analyzed for a total of 159 strains of Enterococcus faecium isolated from clinical specimens in a university hospital in Japan from 1997 to 2006. Resistance to erythromycin (EM) and clindamycin was detected in 88.1% and 89.9% of all the strains examined, respectively, and expression of resistance was totally constitutive. Although none of the strain was resistant to quinupristin/dalfopristin (Q/D), 28 strains (17.6%) showed intermediate resistance to Q/D (MIC: 2 μg/ml). The erm(B) gene was detected in 139 strains (87.4%), and msrC was found in all the strains examined, whereas no other known MLSB resistance genes were identified. The erm(B) regulator region (RR) containing a coding region of the leader peptide was classified into 13 genetic variations (L1-L3, M, S1-S7, D, and R genotypes) in 56 strains. However, no relatedness was identified between the erm(B) RR genotype and EM resistance, or reduced susceptibility to Q/D, although most of Q/D-intermediate strains were assigned to the L1, L2, and S1 genotypes. Q/D-intermediate strains were classified into five multiple-locus variable-number tandem-repeat analysis (MLVA) types, including four types of clonal complex (CC)-C1, five sequence types (STs), including four STs of CC-17, and several resistance gene/virulence factor profiles. The present study revealed the occurrence of Q/D-intermediate E. faecium, which are composed of heterogeneous strains in Japan, and more genetic diversity in the erm(B) RRs than those reported previously.

Dynamics of ampicillin-resistant Enterococcus faecium clones colonizing hospitalized patients: data from a prospective observational study

Background

Little is known about the dynamics of colonizing Enterococcus faecium clones during hospitalization, invasive infection and after discharge.

Methods

In a prospective observational study we compared intestinal E. faecium colonization in three patient cohorts: 1) Patients from the Hematology Unit at the University Hospital Basel (UHBS), Switzerland, were investigated by weekly rectal swabs (RS) during hospitalization (group 1a, n = 33) and monthly after discharge (group 1b, n = 21). 2) Patients from the Intensive Care Unit (ICU) at the University Medical Center Utrecht, the Netherlands (group 2, n = 25) were swabbed weekly. 3) Patients with invasive E. faecium infection at UHBS were swabbed at the time of infection (group 3, n = 22). From each RS five colonies with typical E. faecium morphology were picked. Species identification was confirmed by PCR and ampicillin-resistant E. faecium (ARE) isolates were typed using Multiple Locus Variable Number Tandem Repeat Analysis (MLVA). The Simpson's Index of Diversity (SID) was calculated.

Results

Out of 558 ARE isolates from 354 RS, MT159 was the most prevalent clone (54%, 100%, 52% and 83% of ARE in groups 1a, 1b, 2 and 3, respectively). Among hematological inpatients 13 (40%) had ARE. During hospitalization, the SID of MLVA-typed ARE decreased from 0.745 [95%CI 0.657-0.833] in week 1 to 0.513 [95%CI 0.388-0.637] in week 3. After discharge the only detected ARE was MT159 in 3 patients. In the ICU (group 2) almost all patients (84%) were colonized with ARE. The SID increased significantly from 0.373 [95%CI 0.175-0.572] at week 1 to a maximum of 0.808 [95%CI 0.768-0.849] at week 3 due to acquisition of multiple ARE clones. All 16 patients with invasive ARE were colonized with the same MLVA clone (p < 0.001).

Conclusions

In hospitalized high-risk patients MT159 is the most frequent colonizer and cause of invasive E. faecium infections. During hospitalization, ASE are quickly replaced by ARE. Diversity of ARE increases on units with possible cross-transmission such as ICUs. After hospitalization ARE are lost with the exception of MT159. In invasive infections, the invasive clone is the predominant gut colonizer.

Genomic diversification of enterococci in hosts: the role of the mobilome

Enterococci are ubiquitous lactic acid bacteria, possessing a flexible nature that allows them to colonize various environments and hosts but also to be opportunistic pathogens. Many papers have contributed to a better understanding of: (i) the taxonomy of this complex group of microorganisms; (ii) intra-species variability; (iii) the role of different pathogenicity traits; and (iv) some markers related to the character of host-specificity, but the reasons of such incredible success of adaptability is still far from being fully explained. Recently, genomic-based studies have improved our understanding of the genome diversity of the most studied species, i.e., E. faecalis and E. faecium. From these studies, what is becoming evident is the role of the mobilome in adding new abilities to colonize new hosts and environments, and eventually in driving their evolution: specific clones associated with human infections or specific hosts can exist, but probably the consideration of these populations as strictly clonal groups is only partially correct. The variable presence of mobile genetic elements may, indeed, be one of the factors involved in the evolution of one specific group in a specific host and/or environment. Certainly more extensive studies using new high throughput technologies are mandatory to fully understand the evolution of predominant clones and species in different hosts and environments.

Enterococcus faecium of the vanA genotype in rural drinking water, effluent, and the aqueous environment

Total enterococci and vancomycin-resistant enterococci (VRE) were enumerated in samples of effluent (n = 50) and water (n = 167) from a number of sources. VRE were detected in the outflow of a wastewater treatment plant and in a single rural drinking water supply, suggesting potential for transmission to humans through environmental contamination.

Intra- and interspecies genomic transfer of the Enterococcus faecalis pathogenicity island

Enterococci are the third leading cause of hospital associated infections and have gained increased importance due to their fast adaptation to the clinical environment by acquisition of antibiotic resistance and pathogenicity traits. Enterococcus faecalis harbours a pathogenicity island (PAI) of 153 kb containing several virulence factors including the enterococcal surface protein (esp). Until now only internal fragments of the PAI or larger chromosomal regions containing it have been transferred. Here we demonstrate precise excision, circularization and horizontal transfer of the entire PAI element from the chromosome of E. faecalis strain UW3114. This PAI (ca. 200 kb) contained some deletions and insertions as compared to the PAI of the reference strain MMH594, transferred precisely and integrated site-specifically into the chromosome of E. faecalis (intergenic region) and Enterococcus faecium (tRNAlys). The internal PAI structure was maintained after transfer. We assessed phenotypic changes accompanying acquisition of the PAI and expression of some of its determinants. The esp gene is expressed on the surface of donor and both transconjugants. Biofilm formation and cytolytic activity were enhanced in E. faecalis transconjugants after acquisition of the PAI. No differences in pathogenicity of E. faecalis were detected using a mouse bacteraemia and a mouse peritonitis models (tail vein and intraperitoneal injection). A 66 kb conjugative pheromone-responsive plasmid encoding erm(B) (pLG2) that was transferred in parallel with the PAI was sequenced. pLG2 is a pheromone responsive plasmid that probably promotes the PAI horizontal transfer, encodes antibiotic resistance features and contains complete replication and conjugation modules of enterococcal origin in a mosaic-like composition. The E. faecalis PAI can undergo precise intra- and interspecies transfer probably with the help of conjugative elements like conjugative resistance plasmids, supporting the role of horizontal gene transfer and antibiotic selective pressure in the successful establishment of certain enterococci as nosocomial pathogens.

Tn1546 is part of a larger plasmid-encoded genetic unit horizontally disseminated among clonal Enterococcus faecium lineages

OBJECTIVES

To determine the genetic composition of the first VanA-type plasmid (pIP816) reported, which was isolated from a clinical Enterococcus faecium (BM4147) strain in France in 1986, and to reveal the genetic units responsible for the dissemination of the vanA gene cluster by comparisons with current, published and additionally generated vanA-spanning plasmid sequences obtained from a heterogeneous E. faecium strain collection (n = 28).

METHODS

Plasmid sequences were produced by shotgun sequencing using ABI dye chemistry and primer walking, and were subsequently annotated. Comparative sequence analysis of the vanA region was done with published plasmids, with a partial vanA plasmid (pVEF4) reported here and to >140 kb of sequence obtained from a collection of vanA-harbouring plasmid fragments.

RESULTS

Bioinformatic analyses revealed that pIP816 from 1986 and contemporary vanA plasmids shared a conserved genetic fragment of 25 kb, spanning the 10.85 kb vanA cluster encoded by Tn1546, and that the larger unit is present in both clinical and animal complexes of E. faecium. A new group II intron in pVEF4 was characterized.

CONCLUSIONS

Comparative DNA analyses suggest that Tn1546 disseminates in and between clonal complexes of E. faecium as part of a larger genetic unit, possibly as a composite transposon flanked by IS1216 elements.

Global spread of the hyl(Efm) colonization-virulence gene in megaplasmids of the Enterococcus faecium CC17 polyclonal subcluster

Enterococcus faecium has increasingly been reported as a nosocomial pathogen since the early 1990s, presumptively associated with the expansion of a human-associated Enterococcus faecium polyclonal subcluster known as clonal complex 17 (CC17) that has progressively acquired different antibiotic resistance (ampicillin and vancomycin) and virulence (esp(Efm), hyl(Efm), and fms) traits. We analyzed the presence and the location of a putative glycoside hydrolase hyl(Efm) gene among E. faecium strains obtained from hospitalized patients (255 patients; outbreak, bacteremic, and/or disseminated isolates from 23 countries and five continents; 1986 to 2009) and from nonclinical origins (isolates obtained from healthy humans [25 isolates], poultry [30], swine [90], and the environment [55]; 1999 to 2007). Clonal relatedness was established by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Plasmid analysis included determination of content and size (S1-PFGE), transferability (filter mating), screening of Rep initiator proteins (PCR), and location of vanA, vanB, ermB, and hyl(Efm) genes (S1/I-CeuI hybridization). Most E. faecium isolates contained large plasmids (>150 kb) and showed variable contents of van, hyl(Efm), or esp(Efm). The hyl(Efm) gene was associated with megaplasmids (170 to 375 kb) of worldwide spread (ST16, ST17, and ST18) or locally predominant (ST192, ST203, ST280, and ST412) ampicillin-resistant CC17 clones collected in the five continents since the early 1990s. All but one hyl(Efm)-positive isolate belonged to the CC17 polyclonal subcluster. The presence of hyl(Efm) megaplasmids among CC17 from Europe, Australia, Asia, and Africa since at least the mid-1990s was documented. This study further demonstrates the pandemic expansion of particular CC17 clones before acquisition of vancomycin resistance and putative virulence traits and describes the presence of megaplasmids in most of the contemporary E. faecium isolates with different origins.

Molecular epidemiology of vancomycin-resistant enterococci in Singapore

AIMS

To characterise the mechanism of glycopeptide resistance, genetic relatedness, and pathogenicity factors in isolates of vancomycin-resistant enterococci (VRE) in Singapore.

METHODS

A total of 292 Enterococcus faecium and 17 Enterococcus faecalis were isolated from humans, and five E. faecium, two Enterococcus durans, two Enterococcus flavescens, one Enterococcus casseliflavus, and one Enterococcus gallinarum from chickens. The mechanism of glycopeptide resistance and pathogenicity factors were studied by PCR and the genetic relatedness determined by pulsed-field gel electrophoresis (PFGE), multi-locus variable number tandem repeat analysis (MLVA), and Tn1546 analysis.

RESULTS

There were five outbreak clones among the vancomycin-resistant E. faecium with one clone predominant. Four of the clones were vanB positive, and only one clone carried vanA. All outbreak clones were esp gene positive. Sporadic human isolates and chicken isolates were vanA positive and did not contain any pathogenicity genes. The situation was reversed in vancomycin-resistant E. faecalis where almost all isolates were vanA positive.

CONCLUSIONS

Most VRE in Singapore is hospital associated with a small number of clones of esp-positive vanB E. faecium responsible for the majority of isolates.

Dogs are a reservoir of ampicillin-resistant Enterococcus faecium lineages associated with human infections

Ampicillin resistance is a marker for hospital-associated Enterococcus faecium. Feces from 208 dogs were selectively screened for the occurrence of ampicillin-resistant E. faecium (AREF). AREF was detected in 42 (23%) of 183 dogs screened in a cross-sectional study in the United Kingdom and in 19 (76%) of 25 dogs studied longitudinally in Denmark. AREF carriage was intermittent in all dogs studied longitudinally. Multilocus sequence typing of 63 canine AREF isolates revealed the presence of 13 distinct sequence types. Approximately 76% of the isolates belonged to hospital-adapted clonal complex 17 (CC17), including those of sequence types ST-78 and ST-192, which are widespread in European and Asian hospitals. Longitudinal screening of 18 healthy humans living in contact with 13 of the dogs under study resulted in the identification of a single, intermittent CC17 carrier. This person carried one of the sequence types (ST-78) recovered from his dog. Based on PCR and Southern hybridization analyses, the putative virulence gene cluster from orf903 to orf907 was widespread in canine AREF isolates (present in 97%), whereas orf2351 (present in 26% of isolates) and orf2430 (present in 31%) were strongly associated with CC17-related sequence types (P<0.05). Surprisingly, esp and hyl were not detected in any of the isolates. The antimicrobial resistance profiles of canine AREF isolates generally differed from those previously described for clinical human isolates. The results indicate that dogs are frequent carriers of CC17-related lineages and may play a role in the spread of this nosocomial pathogen. The distinctive virulence and antimicrobial resistance profiles observed among canine AREF isolates raise interesting questions about the origin and evolution of the strains causing human infections.

Streptococcal Infections

The streptococci are a large heterogeneous group of gram-positive spherically shaped bacteria widely distributed in nature. They include some of the most important agents of human disease as well as members of the normal human flora. Some streptococci have been associated mainly with disease in animals, while others have been domesticated and used for the culture of buttermilk, yogurt, and certain cheeses. Those known to cause human disease comprise two broad categories: First are the pyogenic streptococci, including the familiar β-hemolytic streptococci and the pneumococcus. These organisms are not generally part of the normal flora but cause acute, often severe, infections in normal hosts. Second are the more diverse enteric and oral streptococci, which are nearly always part of the normal flora and which are more frequently associated with opportunistic infections.

A simple scoring system to differentiate between relapse and re-infection in patients with recurrent melioidosis

BACKGROUND

Melioidosis is an important cause of morbidity and mortality in East Asia. Recurrent melioidosis occurs in around 10% of patients following treatment either because of relapse with the same strain or re-infection with a new strain of Burkholderia pseudomallei. Distinguishing between the two is important but requires bacterial genotyping. The aim of this study was to develop a simple scoring system to distinguish re-infection from relapse.

METHODS

In a prospective study of 2,804 consecutive adult patients with melioidosis presenting to Sappasithiprasong Hospital, NE Thailand, between 1986 and 2005, there were 141 patients with recurrent melioidosis with paired strains available for genotyping. Of these, 92 patients had relapse and 49 patients had re-infection. Variables associated with relapse or re-infection were identified by multivariable logistic regression and used to develop a predictive model. Performance of the scoring system was quantified with respect to discrimination (area under receiver operating characteristic curves, AUC) and categorization (graphically). Bootstrap resampling was used to internally validate the predictors and adjust for over-optimism.

FINDINGS

Duration of oral antimicrobial treatment, interval between the primary episode and recurrence, season, and renal function at recurrence were independent predictors of relapse or re-infection. A score of < 5 correctly identified relapse in 76 of 89 patients (85%), whereas a score > or = 5 correctly identified re-infection in 36 of 52 patients (69%). The scoring index had good discriminative power, with a bootstrap bias-corrected AUC of 0.80 (95%CI: 0.73-0.87).

CONCLUSIONS

A simple scoring index to predict the cause of recurrent melioidosis has been developed to provide important bedside information where rapid bacterial genotyping is unavailable.

Comparison of multiple-locus variable-number tandem repeat analysis and pulsed-field gel electrophoresis in a setting of polyclonal endemicity of vancomycin-resistant Enterococcus faecium

In order to assess whether multiple-locus-variable number tandem repeat analysis (MLVA) could replace pulsed-field gel electrophoresis (PFGE) for genotyping vancomycin-resistant isolates of Enterococcus faecium (VREF), this study compared the typeability, discriminatory power, concordance and costs of these methods for VREF isolates obtained from patients, environmental samples and the hands of healthcare workers (HCWs) in a medical intensive care unit (ICU) where VREF was endemic. Over a 58-day period, 393 VREF isolates (373 vanA, one vanA/B, 19 vanB) were cultured from patient rectal swabs (n = 76), the environment (n = 270) and the hands of HCWs (n = 47). PFGE was able to divide 358 (91.1%) isolates into 19 PFGE types (>six bands different) and 24 subtypes (one to three bands different). MLVA was able to type 391 (99.5%) isolates into 11 genotypes. The discriminatory power of PFGE subtypes was 83%, as compared to 68% for MLVA. Concordance between the two methods, based on matched or mismatched MLVA types and PFGE types or subtypes, was 67.5% and 82.8%, respectively. Using PFGE, 13 isolates could be genotyped in 3 days; MLVA genotyped 94 isolates in 2 days. For both methods, the estimated costs were Euro 7 ($10)/isolate. PFGE and MLVA produced highly concordant results when assigning genotypes to nosocomial VREF isolates. MLVA was faster, but PFGE subtyping was more discriminatory.

Dépistage des entérocoques résistants aux glycopeptides: six ans d'étude dans trois services de réanimation au CHU de Montpellier

AIM OF THE STUDY

The aim of this study was to evaluate the rate of glycopeptides-resistant enterococci (GRE) fecal carriage (species and resistance determinants). Strains isolated between 1999 and 2005 during systematic screening for multiresistant bacteria in patients hospitalized in 3 intensive care units (ICU) of the University Hospital of Montpellier were studied.

METHODS

The systematic screening was weekly performed. Rectal swabs were cultured on D-Coccosel agar medium containing 4 mg/l vancomycin and MICs for vancomycin and teicoplanin were determined by E-test. Strains were subjected to both phenotypic and genotypic identification and vanA, vanB and vanC genes were detected by PCR.

RESULTS

We analyzed 13003 samples for 5113 patients. Among them, 401 (7.84%) patients were GRE carriers with 280 Enterococcus gallinarum (vanC(1)), 102 Enterococcus casseliflavus-flavescens (vanC(2)-C(3)), 5 Enterococcus faecalis (3 vanA, 2 vanB), and 14 Enterococcus faecium (10 vanA, 4 vanB). A unique case of cross contamination between two patients was observed. During the same time, only one strain of GRE was isolated during an infectious process in another unit. Carriage rate of E. faecium and E. faecalis vanA or vanB was 0.37%: 68.4, 21 and 10.6% in the gastrointestinal, in the polyvalent and the respiratory ICU, respectively.

CONCLUSION

Our results were in agreement with national data showing a relatively low GRE fecal carriage rate in ICUs, E. faecium vanA being the mainly encountered GRE. Since 2004, GRE detection is increasingly reported in France and an emerging E. faecium vanA clone has been identified during outbreaks. In contrast, only one E. faecium vanB strain has been isolated in our institution since this date and a unique strain of E. faecalis vanA was isolated during an infectious process since 1999. These data underlined the efficacy of transmission prevention measures established when GRE are identified.

Increasing rates of vancomycin resistance among Enterococcus faecium isolated from German hospitals between 2004 and 2006 are due to wide clonal dissemination of vancomycin-resistant enterococci and horizontal spread of vanA clusters

Results of national and international surveillance studies revealed increasing rates of vancomycin-resistant Enterococcus faecium (VREF) among German hospital patients since 2003. To investigate the molecular background of vanA-type glycopeptide resistance, 51 clinical VREF isolated between 2004 and 2006 and originating from 19 German hospitals representing 10 Federal States have been investigated. Isolates were characterised by multi-locus sequence typing (MLST), SmaI macrorestriction analysis in pulsed-field gel electrophoresis (PFGE), and multiple-locus variable-number tandem repeat analysis (MLVA). Phylogenetic relatedness between strains was identified using BioNumerics and eBURST software. Distribution of virulence markers esp and hyl(Efm) was investigated by PCR. The structure of the vanA gene clusters was investigated by PCR, long-template PCR, sequencing and Southern hybridisations. The 51 VREF were rather diverse constituting different strain types, different virulence markers and vanA clusters. Within this diversity we found supportive data for a dissemination of related--already vancomycin-resistant--E. faecium among various hospitals and Federal States and for spread of identical vanA gene clusters among clonally different strain types within single hospitals. In conclusion, the increase in the rates of VREF among German hospital patients within the last 2 years might be rather complex and due to different molecular events and scenarios.