Hospital outbreak of vancomycin-resistant enterococci caused by a single clone of Enterococcus raffinosus and several clones of Enterococcus faecium

Non-faecium non-faecalis enterococci: a review of clinical manifestations, virulence factors, and antimicrobial resistance

SUMMARYEnterococci are a diverse group of Gram-positive bacteria that are typically found as commensals in humans, animals, and the environment. Occasionally, they may cause clinically relevant diseases such as endocarditis, septicemia, urinary tract infections, and wound infections. The majority of clinical infections in humans are caused by two species: Enterococcus faecium and Enterococcus faecalis. However, there is an increasing number of clinical infections caused by non-faecium non-faecalis (NFF) enterococci. Although NFF enterococcal species are often overlooked, studies have shown that they may harbor antimicrobial resistance (AMR) genes and virulence factors that are found in E. faecium and E. faecalis. In this review, we present an overview of the NFF enterococci with a particular focus on human clinical manifestations, epidemiology, virulence genes, and AMR genes.

Spontaneous resolution or antibiotic effectiveness? Reflection on a case of pediatric urinary tract infections caused by Enterococcus raffinosus

Enterococcus raffinosus, named by Collins et al. in 1989, is a cocci-shaped bacterium that typically appears in pairs or short chains. As a Gram-positive and non-motile bacterium, it grows at 10°C-45°C, exhibiting negative peroxidase activity [1]. It is a normal flora in the oropharynx and gastrointestinal tract of domestic cats [2] and can also be isolated from human rectal swabs [3], it belongs to the same genus Enterococcus as Enterococcus faecalis and Enterococcus faecium. Enterococcus faecalis and Enterococcus faecium constitute 90% of clinically isolated strains. However, the incidence of other enterococci, excluding E. faecalis and E. faecium, is on the rise [4]. In this case report, a patient with pediatric urinary tract infections caused by E. raffinosus was presented, and a summary of relevant literature was provided.

Antibiotic Resistance in Bacteria—A Review

Background: A global problem of multi-drug resistance (MDR) among bacteria is the cause of hundreds of thousands of deaths every year. In response to the significant increase of MDR bacteria, legislative measures have widely been taken to limit or eliminate the use of antibiotics, including in the form of feed additives for livestock, but also in metaphylaxis and its treatment, which was the subject of EU Regulation in 2019/6. Numerous studies have documented that bacteria use both phenotypis and gentic strategies enabling a natural defence against antibiotics and the induction of mechanisms in increasing resistance to the used antibacterial chemicals. The mechanisms presented in this review developed by the bacteria have a significant impact on reducing the ability to combat bacterial infections in humans and animals. Moreover, the high prevalence of multi-resistant strains in the environment and the ease of transmission of drug-resistance genes between the different bacterial species including commensal flora and pathogenic like foodborne pathogens (E. coli, Campylobacter spp., Enterococcus spp., Salmonella spp., Listeria spp., Staphylococcus spp.) favor the rapid spread of multi-resistance among bacteria in humans and animals. Given the global threat posed by the widespread phenomenon of multi-drug resistance among bacteria which are dangerous for humans and animals, the subject of this study is the presentation of the mechanisms of resistance in most frequent bacteria called as “foodborne pathoges” isolated from human and animals. In order to present the significance of the global problem related to multi-drug resistance among selected pathogens, especially those danger to humans, the publication also presents statistical data on the percentage range of occurrence of drug resistance among selected bacteria in various regions of the world. In addition to the phenotypic characteristics of pathogen resistance, this review also presents detailed information on the detection of drug resistance genes for specific groups of antibiotics. It should be emphasized that the manuscript also presents the results of own research i.e., Campylobacter spp., E. coli or Enetrococcus spp. This subject and the presentation of data on the risks of drug resistance among bacteria will contribute to initiating research in implementing the prevention of drug resistance and the development of alternatives for antimicrobials methods of controlling bacteria.

Enterococcus raffinosus, Enterococcus durans and Enterococcus avium Isolated from a Tertiary Care Hospital in Romania-Retrospective Study and Brief Review

(1) Background: This paper aims to provide a description of non-faecalis non-faecium enterococci isolated from a tertiary care hospital in Romania and to briefly review the existing literature regarding the involvement of Enterococcus raffinosus, Enterococcus durans and Enterococcus avium in human infections and their antimicrobial resistance patterns; (2) Methods: We retrospectively analyzed all Enteroccocus species isolated from the “Prof. Dr. O. Fodor” Regional Institute of Gastroenterology and Hepatology from Cluj-Napoca during one year focusing on non-faecalis non-faecium Enterococci. A brief review of the literature was performed using case reports involving Enterococcus raffinosus, Enterococcus durans and Enterococcus avium; (3) Results: Only 58 out of 658 Enteroccocus isolates were non-faecalis non-faecium and met the inclusion criteria. These species were isolated more often (p < 0.05) from the surgical ward from mixed etiology infections with E. coli. In our review, we included 39 case reports involving E. raffinosus, E. durans and E. avium; (4) Conclusions: Isolation of non-faecalis non-faecium enterococci displays an emerging trend with crucial healthcare consequences. Based on the analysis of the case reports, E. avium seems to be involved more often in neurological infections, E. durans in endocarditis, while E. raffinosus displays a more heterogenous distribution.

Enterococcus raffinosus bacteremia: clinical experience with 49 adult patients

This study is to evaluate the clinical characteristics and outcomes of Enterococcus raffinosus bacteremia in adults. We analyzed the medical records of adult patients with E. raffinosus bacteremia who were diagnosed and treated between 1997 and 2020 at a tertiary care teaching hospital in Seoul, Republic of Korea. The demographic, clinical, and laboratory data were collected and assessed. A total of 49 cases of E. raffinosus bacteremia were identified. E. raffinosus accounted for 0.6% of all enterococcal bacteremia events, and the incidence was 0.02 cases per 1,000 admissions. Of the 49 cases of E. raffinosus bacteremia, 35 (71.4%) had underlying malignancy. The biliary tract was the most common source of infection (81.6%, 40/49) and polymicrobial bacteremia was found in 25 cases (51.0%). The resistance rates of E. raffinosus bacteremia cases to penicillin, ampicillin, vancomycin, and linezolid were 61.2%, 49.0%, 2.0%, and 0%, respectively. In our case series, there was one case of vanA-type vancomycin-resistant E. raffinosus. The all-cause 60-day mortality rate was 22.4% (11/49), and the E. raffinosus bacteremia-related mortality rate was 4.1% (2/49). Cases of E. raffinosus bacteremia mainly originated from biliary tract infection and had a low rate of bacteremia-related mortality.

First Report of the Local Spread of Vancomycin-Resistant Enterococci Ascribed to the Interspecies Transmission of a vanA Gene Cluster-Carrying Linear Plasmid

Increasing multidrug resistance, including vancomycin resistance, in enterococci is a major concern in clinical settings. Horizontal gene transfer, such as via plasmids, has been shown to play a crucial role in the acquisition of vancomycin resistance. Among vancomycin resistance types, the VanA type is one of the most prevalent, and outbreaks caused by VanA-type vancomycin-resistant enterococci (VRE) have occurred worldwide. Here, we describe an enterococcal linear plasmid responsible for multispecies local spread of VanA-type VRE. Such a study is important because although hospital outbreaks caused by mixed enterococcal species have been reported, this particular spread indicates plasmid transfer across species. This is a crucial finding because the high risk for such a spread of antimicrobial resistance calls for regular monitoring and surveillance.

Vancomycin-resistant enterococci pose a threat in the clinical setting and have been linked to hospital outbreaks worldwide. In 2017, a local spread of VanA-type vancomycin-resistant enterococci (VRE) occurred in Japan, and 25 enterococcal isolates, including 14 Enterococcus faecium, 8 E. raffinosus, and 3 E. casseliflavus isolates, were identified from four inpatients. Molecular analysis of the multispecies of VanA-type VRE revealed the involvement of both the dissemination of clonally related VRE strains between patients and the horizontal transfer of plasmids harboring the vanA gene cluster between Enterococcus spp. Pulsed-field gel electrophoresis showed that the plasmid DNAs without S1 nuclease treatment were able to migrate into the gel, suggesting that the topology of the plasmid was linear. Whole-genome sequencing revealed that this plasmid, designated pELF2, was 108,102 bp long and encoded multiple antimicrobial resistance genes, including ermA and ant(9). The amino acid sequences of putative replication- and transfer-related genes were highly conserved between pELF2 and pELF1, the latter of which was the first identified enterococcal conjugative linear plasmid. On comparing the genomic structure, pELF2 showed the presence of a backbone similar to that of pELF1, especially with respect to the nucleotide sequences of both terminal ends, indicating a hybrid-type linear plasmid, possessing two different terminal structures. pELF2 possessed a broad host range and high conjugation frequencies for enterococci. The easy transfer of pELF2 to different Enterococcus spp. in vitro might explain this local spread of multiple species, highlighting the clinical threat from the spread of antimicrobial resistance by an enterococcal linear plasmid.

IMPORTANCE Increasing multidrug resistance, including vancomycin resistance, in enterococci is a major concern in clinical settings. Horizontal gene transfer, such as via plasmids, has been shown to play a crucial role in the acquisition of vancomycin resistance. Among vancomycin resistance types, the VanA type is one of the most prevalent, and outbreaks caused by VanA-type vancomycin-resistant enterococci (VRE) have occurred worldwide. Here, we describe an enterococcal linear plasmid responsible for multispecies local spread of VanA-type VRE. Such a study is important because although hospital outbreaks caused by mixed enterococcal species have been reported, this particular spread indicates plasmid transfer across species. This is a crucial finding because the high risk for such a spread of antimicrobial resistance calls for regular monitoring and surveillance.

High Phenotypic and Genotypic Diversity of Enterococcus faecium from Clinical and Commensal Isolates in Third Level Hospital

Background: The use of antimicrobials and myeloablative chemotherapy regimens has promoted multiresistant microorganisms to emerge as nosocomial pathogens, such as vancomycin-resistant Enterococcus faecium (VREfm). We described a polyclonal outbreak of bloodstream infection caused by Efm in a hemato-oncological ward in Mexico. Our aim was to describe the clonal complex (CC) of the Efm strains isolated in the outbreak in comparison with commensal and environmental isolates. Methodology: Sixty Efm clinical, environmental, and commensal strains were included. We constructed a cladogram and a phylogenetic tree using Vitek and Multilocus sequence typing data, respectively. Results: We reported 20 new sequence types (ST), among which 17/43 clinical isolates belonged to CC17. The predominant ST in the clinical strains were ST757, ST1304, ST412, and ST770. Neither environmental nor commensal isolates belonged to CC17. The phylogeny of our collection shows that the majority of the clinical isolates were different from the environmental and commensal isolates, and only a small group of clinical isolates was closely related with environmental and commensal isolates. The cladogram revealed a similar segregation to that of the phylogeny. Conclusions: We found a high diversity among clinical, environmental, and commensal strains in a group of samples in a single hospital. Highest diversity was found between commensal and environmental isolates.

Using groEL as the target for identification of Enterococcus faecium clades and 7 clinically relevant Enterococcus species

BACKGROUND/PURPOSE

Accurate identification is important for effective treatment because Enterococcus species have talents to cope with various antibiotics either by intrinsic resistance or by acquisition of mobile genetic elements. The groEL gene is a permissive target in identification of bacteria. We aimed to develop simple assays based on groEL for identification of enterococci.

RESULTS

We continued our previous work and determined groEL gene sequences of Enterococcus species isolated from clinical specimens. Phylogenetic analysis based on groEL revealed that each strain clustered well with their reference strains (bootstrap value 100%), in which Enterococcusfaecium and Enterococcusgallinarum could be split into two clades. The divergence of E. faecium was coincident with hospital-associated clade, known as clade A, and community-associated clade, known as clade B. A PCR-restriction fragment length polymorphism (PCR-RFLP) assay was therefore designed to differentiate the two E. faecium clades, based on the specific RsaI cutting sites present in the two clades. To differentiate 7 clinical relevant Enterococcus species, the multiplex PCR assay was designed to identify Enterococcusavium, Enterococcuscasseliflavus, Enterococcusfaecalis, E. faecium, E. gallinarum, Enterococcushirae and Enterococcusraffinosus. Specificity was tested with other Enterococcus species including Enterococcuscecorum, Enterococcusdurans and Enterococcusmundtii. None of these bacterial species generated products of similar size to those of the seven Enterococcus species.

CONCLUSION

The simple PCR-RFLP and multiplex PCR assays on the basis of groEL gene provided an alternative way to identify Enterococcus species.

Outbreaks caused by vancomycin-resistant Enterococcus faecium in hematology and oncology departments: A systematic review

Background

Vancomycin-resistance in Enterococcus faecium (VRE) poses a major threat in health care settings. It is well known that patients in hematology and oncology departments are especially at risk of nosocomial VRE acquisition. This systematic review of the literature provides data on the main sources, transmission modes and potential risk factors for VRE acquisition as well as appropriate infection control measures in order to terminate such nosocomial outbreaks.

Methods

Data on nosocomial VRE outbreaks on hematology and oncology wards was retrieved from the Outbreak Database and PubMed.

Results

A total of 35 VRE outbreaks describing 757 affected patients and 77 deaths were included in this review. The most frequent site of pathogen detection were stool samples or rectal swabs (57% of all isolation sites), followed by blood cultures (30%). The most common outbreak source was an index patient. The main modes of transmission were 1) hands of health care workers, 2) contact to a contaminated environment and 3) patient-to-patient contact. The most common risk factor for VRE positivity was prior antibiotic treatment. The most common infection control measures performed were screening and isolating or cohorting of patients.

Conclusion

A rational use of antibiotics in hematology and oncology units is recommended in order to reduce selection pressure on resistant pathogens such as VRE. In addition the importance of hand hygiene should be stressed to all staff whenever possible.

Where is the difference between an epidemic and a high endemic level with respect to nosocomial infection control measures? An analysis based on the example of vancomycin-resistant Enterococcus faecium in hematology and oncology departments

Some infection control recommendations distinguish epidemic and endemic levels for infection control. However, it is often difficult to separate long lasting outbreaks from high endemic levels and it remains open, if this distinction is really useful. Aim: To compare infection control measures in endemic and epidemic outbreaks. Methods: The example of vancomycin-resistant Enterococcus faecium outbreaks in haematology or oncology departments was used to analyse differences in infection control measures between outbreaks and high endemic levels. The outbreak database and PubMed, including long lasting outbreaks, were used for this analysis. Two time limits were used for separation: 6 and 12 months. In addition, monoclonal and polyclonal outbreaks were distinguished. Findings: A total of 36 outbreaks were included. 13 outbreaks lasted 6 months or less, 9 outbreaks more than 6 months but at maximum 12 months and 9 more than 12 months. For the remaining outbreaks, no information about their duration was available. Altogether, 11 outbreaks were monoclonal and 20 polyclonal. Considering infection control measures, there were almost no differences between the different groups compared. Patient screening was given up in 37.5% of long lasting outbreaks (>12 months) and hand hygiene not reported in the majority of polyclonal outbreaks (77.8%). Conclusion: Despite many institutions trying to add further infection control measures in case of an outbreak, evidence based infection control measures should be implemented in endemic and epidemic situations. The crucial aspect is probably the degree of implementation and its control in both situations.

Diversity of plasmids and Tn1546-type transposons among VanA Enterococcus faecium in Poland

The objective of this study was to investigate the antimicrobial resistance, Tn1546 transposon variability and plasmid diversity among Polish vancomycin-resistant Enterococcus faecium (VREfm) isolates of VanA phenotype in the context of their clonal structure. Two hundred sixteen clinical VREfm isolates collected between 1997 and 2010 were studied by antimicrobial susceptibility testing, MLST, MLVA and detection of IS16, esp _Efm, pilA, intA and plasmid-specific genes by PCR. Tn1546 structure was revealed by overlapping PCR and sequencing. Selected isolates were subjected to PFGE-S1 and Southern hybridization analyses. The vast majority of the isolates (95.8 %) belonged to lineages 17/18 (during the whole study period 1997-2010) and 78 (mostly in 2006-2010) of hospital-adapted meroclone of E. faecium. All isolates displayed a multi-drug resistance phenotype. Twenty-eight Tn1546 types (including 26 novel ones) were associated with eight different ISs (IS1216, IS1251, ISEfa4, ISEfa5, ISEfm2, ISEf1, IS3-like, ISEfm1-like). The vanA-determinant was typically located on plasmids, which most commonly carried rep2_pRE25, rep17_pRUM, rep18_pEF418, rep1_pIP501, ω-ε-ζ and axe-txe genes. VanA isolates from 1997-2005 to 2006-2010 differed in clonal composition, prevalence of gentamicin- and tetracycline-resistance and plasmidome. Our analysis revealed high complexity of Tn1546-type transposons and vanA-plasmids, and suggested that diverse genetic events, such as conjugation transfer, recombination, chromosomal integration and DNA mutations shaped the structure of these elements among Polish VREfm.

A decade of genomic history for healthcare-associated Enterococcus faecium in the United Kingdom and Ireland

Vancomycin-resistant Enterococcus faecium (VREfm) is an important cause of healthcare-associated infections worldwide. We undertook whole-genome sequencing (WGS) of 495 E. faecium bloodstream isolates from 2001-2011 in the United Kingdom and Ireland (UK&I) and 11 E. faecium isolates from a reference collection. Comparison between WGS and multilocus sequence typing (MLST) identified major discrepancies for 17% of isolates, with multiple instances of the same sequence type (ST) being located in genetically distant positions in the WGS tree. This confirms that WGS is superior to MLST for evolutionary analyses and is more accurate than current typing methods used during outbreak investigations. E. faecium has been categorized as belonging to three clades (Clades A1, hospital-associated; A2, animal-associated; and B, community-associated). Phylogenetic analysis of our isolates replicated the distinction between Clade A (97% of isolates) and Clade B but did not support the subdivision of Clade A into Clade A1 and A2. Phylogeographic analyses revealed that Clade A had been introduced multiple times into each hospital referral network or country, indicating frequent movement of E. faecium between regions that rarely share hospital patients. Numerous genetic clusters contained highly related vanA-positive and -negative E. faecium, which implies that control of vancomycin-resistant enterococci (VRE) in hospitals also requires consideration of vancomycin-susceptible E. faecium Our findings reveal the evolution and dissemination of hospital-associated E. faecium in the UK&I and provide evidence for WGS as an instrument for infection control.

Molecular analysis of vanA outbreak of Enterococcus faecium in two Warsaw hospitals: the importance of mobile genetic elements

Vancomycin-resistant Enterococcus faecium represents a growing threat in hospital-acquired infections. Two outbreaks of this pathogen from neighboring Warsaw hospitals have been analyzed in this study. Pulsed-field gel electrophoresis (PFGE) of SmaI-digested DNA, multilocus VNTR analysis (MLVA), and multilocus sequence typing (MLST) revealed a clonal variability of isolates which belonged to three main lineages (17, 18, and 78) of nosocomial E. faecium. All isolates were multidrug resistant and carried several resistance, virulence, and plasmid-specific genes. Almost all isolates shared the same variant of Tn1546 transposon, characterized by the presence of insertion sequence ISEf1 and a point mutation in the vanA gene. In the majority of cases, this transposon was located on 50 kb or 100 kb pRUM-related plasmids, which lacked, however, the axe-txe toxin-antitoxin genes. 100 kb plasmid was easily transferred by conjugation and was found in various clonal backgrounds in both institutions, while 50 kb plasmid was not transferable and occurred solely in MT159/ST78 strains that disseminated clonally in one institution. Although molecular data indicated the spread of VRE between two institutions or a potential common source of this alert pathogen, epidemiological investigations did not reveal the possible route by which outbreak strains disseminated.

Vancomycin-resistant enterococci: Troublemaker of the 21st century

The emergence of multidrug-resistant and vancomycin-resistant enterococci during the last decade has made it difficult to treat nosocomial infections. Although various enterococcal species have been identified, only two (Enterococcus faecalis and Enterococcus faecium) are responsible for the majority of human infections. Vancomycin is an important therapeutic alternative against multidrug-resistant enterococci but is associated with a poor prognosis. Resistance to vancomycin dramatically reduces the therapeutic options for enterococcal infections. The bacterium develops resistance by modifying the C-terminal d-alanine of peptidoglycan to d-lactate, creating a d-Ala-d-Lac sequence that effectively reduces the affinity of vancomycin for the peptidoglycan by 1000-fold. Moreover, the resistance genes can be transferred from enterococci to Staphylococcus aureus, thereby posing a threat to patient safety and also a challenge for treating physicians. Judicious use of vancomycin and broad-spectrum antibiotics must be implemented, but strict infection control measures must also be followed to prevent nosocomial transmission of these organisms. Furthermore, improvements in clinical practice, rotation of antibiotics, herbal drugs, nanoantibiotics and the development of newer antibiotics based on a pharmacogenomic approach may prove helpful to overcome dreadful vancomycin-resistant enterococcal infections.

Occurrence of Enterococcus species with virulence markers in an urban flow-influenced tropical recreational beach

Median enterococci counts of beach water samples gradually increased at statistically significant levels (χ2: 26.53, df: 4; p<0.0001) with increasing proximity to river influx. The difference in proportion of antibiotic resistant enterococci in beach water and river water samples was statistically significant (p<0.05) for the tested antibiotics with river isolates generally presenting higher resistance frequencies. Virulence genes cyl, esp, gelE and asa were detected at varying frequencies (7.32%, 21.95%, 100% and 63.41% respectively) among river isolates. On the other hand, the prevalence of these genes was lower (0%, 20%, 67.27% and 41.82% respectively) among beach water isolates. Multi-Locus-Sequence-Typing analysis of Enterococcus faecalis presented four sequence types (ST) one of which shared six out of seven tested loci with ST6, a member of the clonal complex of multi-drug resistant strains associated with hospital outbreaks.

High abundance and diversity of antimicrobial resistance determinants among early vancomycin-resistant Enterococcus faecium in Poland

The purpose of this study was to investigate the clonal structure, antimicrobial resistance phenotypes and their determinants among early vancomycin-resistant Enterococcus faecium (VREm) isolates in Poland. Two hundred and eighty-one VREm isolates collected between 1997 and 2005 were studied. VREm isolates were characterised by multilocus sequence typing (MLST). The presence of antimicrobial resistance determinants, transposon-specific genes, IS16 and esp Efm was checked by polymerase chain reaction (PCR). Ciprofloxacin and ampicillin resistance determinants were investigated by sequencing. Two hundred and twenty-two (79 %) and 59 (21 %) VREm isolates were vanA- and vanB-positive, respectively. Among 135 representative isolates, MLST yielded 33 different sequence types (STs), of which 29 were characteristic of hospital-associated E. faecium; 128 (94.8 %) and 123 (91.1 %) isolates harboured the IS16 and esp Efm genes, and all 135 isolates were resistant to ciprofloxacin and ampicillin. Resistance to tetracycline (71.1 % isolates) was mostly associated with tetM (75.0 %) and the concomitant presence of the Tn916 integrase gene. High-level resistance to streptomycin (93.3 % of isolates) and high-level resistance to gentamicin (94.1 % of isolates) were due to ant(6')-Ia and aac(6')-Ie-aph(2″) genes, respectively, the latter of which is known to be located on various Tn4001-type transposons. Fifteen combinations of mutations in the quinolone-determining regions of GyrA and ParC were identified, including changes not previously reported, such as S83F and A84P in GyrA. Twenty-three variants of the penicillin-binding protein PBP5 occurred in the studied group, and novel insertions at amino acid positions 433 and 568 were identified. This analysis revealed the predominance of hospital-associated strains of E. faecium, carrying an abundant and divergent range of resistance determinants among early VREm isolates in Poland.

Dissemination of antibiotic-resistant enterococci within the ward environment: the role of airborne bacteria and the risk posed by unrecognized carriers

BACKGROUND

Colonized or infected patients pose a significant risk to noncolonized patients occupying the same room. The aim of this study was to investigate how far Enterococcus spp can spread from isolated and nonisolated patients.

METHODS

Conventional microbiological methods were used to recover enterococci from the air and from 62 high-contact sites located within the near-patient and wider ward environment. Samples were collected twice weekly for 17 weeks. The similarity between isolates was determined via pulsed-field gel electrophoresis.

RESULTS

Vancomycin-susceptible enterococci (VSE) were recovered from 352 of 2,046 environmental surfaces (17.2%) and from 27 of 66 air samples (40.9%). During study week 14, VSE was recovered from 75 of the 124 surfaces sampled, representing 21.3% of all VSE-positive sites. A gentamicin-resistant VS Enterococcus faecium clone was recovered in high numbers from the air (>100 cfu/m(3)) and from surfaces throughout a 4-bed bay. The same clone was recovered from an adjacent isolation room as well. A total of 55 surfaces were contaminated with vancomycin-resistant enterococci (VRE). The environment of 2 isolated patients accounted for 85% of contaminated sites. Neither patient was known to be VRE-positive.

CONCLUSIONS

Unrecognized colonization and/or the aerosolization of enterococci together with inadequate cleaning can lead to heavy, widespread, and persistent environmental contamination. All pose a significant risk for acquisition of antibiotic-resistant enterococci.

Molecular characterization of vancomycin-resistant enterococci in a Chinese hospital between 2003 and 2009

From June 2003 to December 2009, 98 isolates of vancomycin-resistant enterococci (VRE) were cultured from clinical specimens taken from patients admitted to a 1,500-bed tertiary-care teaching hospital in Beijing, China. Isolates were characterized by pulsed-field gel electrophoresis and multilocus sequence typing. We investigated the structure of the vanA gene cluster and the distribution of the virulence markers esp, hyl, gelE, asa1, and cylA by polymerase chain reaction. Our results indicate that multilocus sequence typing revealed five novel sequence types and one new allele. VRE faecium (VREfm) isolates were heterogeneous in their vanA cluster types and in the presence of virulence genes. We also observed inconsistency between genotype and phenotype in VREfm isolates. The outbreak with VREfm in our hospital appears polyclonal, whereas VRE faecalis characterization indicated dissemination of a particular clone. After 2007, VRE faecalis was completely replaced by VREfm, which has since been the predominant species in our hospital. VRE appears to be in an evolutionary flux in our hospital.

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.

Traumatic endophthalmitis caused by Enterococcus raffinosus and Enterobacter gergoviae

We report a rare case of polymicrobial traumatic endophthalmitis caused by Enterococcus raffinosus and Enterobacter gergoviae with successful interventions of complete pars plana vitrectomy with intravitreal injections of vancomycin and amikacin. In addition, the patient achieved a favourable visual acuity of 20/200.

New selective and differential chromogenic agar medium, chromID VRE, for screening vancomycin-resistant Enterococcus species

This study aimed to evaluate the usefulness of a novel differential culture medium, chromID VRE agar, for the isolation of VRE in a clinical laboratory. It was shown that ChromID VRE agar may be useful for rapid and selective isolation of VRE especially after inclusion of broth enrichment step.

Diversity of Tn1546 and its role in the dissemination of vancomycin-resistant enterococci in Portugal

We characterized the molecular diversity of vanA vancomycin-resistant enterococci (VRE; 176 isolates/87 pulsed-field gel electrophoresis types) from different sources and cities in Portugal (1996 to 2004): (i) food animals (FA; n = 38 isolates out of 31 samples), hospitalized humans (HH; n = 101/101), healthy human volunteers (HV; n = 7/4), and environmental sources (n = 30/10). Some strains were isolated from different hosts and persistently recovered for years. Twenty-four Tn1546 variants were identified, all located on plasmids (30 to 250 kb). Some Tn1546 variants were associated with specific sources such as FA (3 types), HH (11 types), or HV (1 type), while others were recovered from isolates of different origins (8 types). Polymorphisms in the central vanRSHA region of Tn1546 were scarcely detected, while alterations upstream of vanR and downstream of vanA were frequently identified involving mutations (vanS and vanX), deletions (vanY), insertions (IS1216V, ISEf1, and IS19; sequences with or without homology with others available in GenBank databases), and different genetic rearrangements. Most Tn1546 variants contained IS1216V (14 types) or ISEf1 (6 types). IS1216V was found alone or associated with an IS3-like element at different orientations and positions in Tn1546 from human, animal, and environmental samples. ISEf1 was located within vanX-vanY region at nucleotide 9044 of Tn1546 variants mostly associated with clinical isolates, suggesting a common genetic platform. IS19 was observed within the vanX-vanY region in one Tn1546 variant from poultry. Recent spread of VRE in Portugal reflects a complex epidemiology involving both clonal spread and plasmid dissemination containing a variety of Tn1546 types. Apparent Tn1546 heterogeneity among enterococci from human, animal, and environmental sources might reflect frequent genetic exchange events and evolution of particular widely disseminated genetic elements.