Prevalence of esp, encoding the enterococcal surface protein, in Enterococcus faecalis and Enterococcus faecium isolates from hospital patients, poultry, and pigs in Denmark.
Prevalence of esp, encoding the enterococcal surface protein, in Enterococcus faecalis and Enterococcus faecium isolates from hospital patients, poultry, and pigs in Denmark.
Project description:The enterococcal surface protein, Esp, is a high-molecular-weight surface protein of unknown function whose frequency is significantly increased among infection-derived Enterococcus faecalis isolates. In this work, a global structural similarity was found between Bap, a biofilm-associated protein of Staphylococcus aureus, and Esp. Analysis of the relationship between the presence of the Esp-encoding gene (esp) and the biofilm formation capacity in E. faecalis demonstrated that the presence of the esp gene is highly associated (P < 0.0001) with the capacity of E. faecalis to form a biofilm on a polystyrene surface, since 93.5% of the E. faecalis esp-positive isolates were capable of forming a biofilm. Moreover, none of the E. faecalis esp-deficient isolates were biofilm producers. Depending on the E. faecalis isolate, insertional mutagenesis of esp caused either a complete loss of the biofilm formation phenotype or no apparent phenotypic defect. Complementation studies revealed that Esp expression in an E. faecalis esp-deficient strain promoted primary attachment and biofilm formation on polystyrene and polyvinyl chloride plastic from urine collection bags. Together, these results demonstrate that (i) biofilm formation capacity is widespread among clinical E. faecalis isolates, (ii) the biofilm formation capacity is restricted to the E. faecalis strains harboring esp, and (iii) Esp promotes primary attachment and biofilm formation of E. faecalis on abiotic surfaces.
Project description:Enterococci have emerged as important nosocomial pathogens with resistance to multiple antibiotics. Adhesion to abiotic materials and biofilm formation on medical devices are considered important virulence properties. A single clonal lineage of Enterococcus faecium, complex 17 (CC17), appears to be a successful nosocomial pathogen, and most CC17 isolates harbor the enterococcal surface protein gene, esp. In this study, we constructed an esp insertion-deletion mutant in a clinical E. faecium CC17 isolate. In addition, initial adherence and biofilm assays were performed. Compared to the wild-type strain, the esp insertion-deletion mutant no longer produced Esp on the cell surface and had significantly lower initial adherence to polystyrene and significantly less biofilm formation, resulting in levels of biofilm comparable to those of an esp-negative isolate. Capacities for initial adherence and biofilm formation were restored in the insertion-deletion mutant by in trans complementation with esp. These results identify Esp as the first documented determinant in E. faecium CC17 with an important role in biofilm formation, which is an essential factor in infection pathogenesis.
Project description:Sixteen isolates of Enterococcus faecalis were recovered from retail poultry samples (seven chickens and nine turkeys) purchased from grocery stores in the greater Washington, D.C., area. PCR for known streptogramin resistance genes identified vat(E) in five E. faecalis isolates (three isolates from chickens and two isolates from turkeys). The vat(E) gene was transmissible on a ca. 70-kb plasmid, along with resistance to erythromycin, tetracycline, and streptomycin, by conjugation to E. faecalis and Enterococcus faecium recipient strains. DNA sequencing showed little variation between E. faecalis vat(E) genes from the chicken samples; however, one E. faecalis vat(E) gene from a turkey sample possessed 5 nucleotide changes that resulted in four amino acid substitutions. None of these substitutions in the vat(E) allele have previously been described. This is the first report of vat(E) in E. faecalis and its transferability to E. faecium, which indicates that E. faecalis can act as a reservoir for the dissemination of vat(E)-mediated streptogramin resistance to E. faecium.
Project description:Enterococci have emerged as one of the leading causes of nosocomial bloodstream, surgical site, and urinary tract infections. More recently, enterococci have been associated with biofilms, which are bacterial communities attached to a surface and encased in an extracellular polymeric matrix. The enterococcal cell surface-associated protein, Esp, enhances biofilm formation by Enterococcus faecalis in a glucose-dependent manner. Mature Esp consists of a nonrepeat N-terminal domain and a central region made up of two types of tandem repeats followed by a C-terminal membrane-spanning and anchor domain. This study was undertaken to localize the specific domain(s) of Esp that plays a role in Esp-mediated biofilm enhancement. To achieve this objective, we constructed in-frame deletion mutants expressing truncated forms of Esp in an isogenic background. By comparing strains expressing the mutant forms of Esp to those expressing wild-type Esp, we found that the strain expressing Esp lacking the N-terminal domain formed biofilms that were quantitatively less in biovolume than the strain expressing wild-type Esp. Furthermore, an E. faecalis strain expressing only the N-terminal domain of Esp fused to a heterologous protein anchor formed biofilms that were quantitatively similar to those formed by a strain expressing full-length Esp. This suggested that the minimal region contributing to Esp-mediated biofilm enhancement in E. faecalis was confined to the nonrepeat N-terminal domain. Expression of full-length E. faecalis Esp in heterologous host systems of esp-deficient Lactococcus lactis and Enterococcus faecium did not enhance biofilm formation as was observed for E. faecalis. These results suggest that Esp may require interaction with an additional E. faecalis-specific factor(s) to result in biofilm enhancement.
Project description:Enterococcus, a Gram-positive facultative anaerobic cocci belonging to the lactic acid bacteria of the phylum Firmicutes, is known to be able to resist a wide range of hostile conditions such as different pH levels, high concentration of NaCl (6.5%), and the extended temperatures between 5(°)C and 65(°)C. Despite being the third most common nosocomial pathogen, our understanding on its virulence factors is still poorly understood. The current study was aimed to determine the prevalence of different virulence genes in Enterococcus faecalis and Enterococcus faecium. For this purpose, 79 clinical isolates of Malaysian enterococci were evaluated for the presence of virulence genes. pilB, fms8, efaAfm, and sgrA genes are prevalent in all clinical isolates. In conclusion, the pathogenicity of E. faecalis and E. faecium could be associated with different virulence factors and these genes are widely distributed among the enterococcal species.
Project description:Enterococcus faecalis harbors a virulence-associated surface protein encoded by the esp gene. This gene has been shown to be part of a 150-kb putative pathogenicity island. A gene similar to esp has recently been found in Enterococcus faecium isolates recovered from hospitalized patients. In the present study we analyzed the polymorphism in the esp gene of E. faecium, and we investigated the association of esp with neighboring chromosomal genes. The esp gene showed considerable sequence heterogeneity in the regions encoding the nonrepeat N- and C-terminal domains of the Esp protein as well as differences in the number of repeats. DNA sequencing of chromosomal regions flanking the esp gene of E. faecium revealed seven open reading frames, representing putative genes implicated in virulence, regulation of transcription, and antibiotic resistance. These flanking regions were invariably associated with the presence or absence of the esp gene in E. faecium, indicating that esp in E. faecium is part of a distinct genetic element. Because of the presence of virulence genes in this gene cluster, the lower G+C content relative to that of the genome, and the presence of esp in E. faecium isolates associated with nosocomial outbreaks and clinically documented infections, we conclude that this genetic element constitutes a putative pathogenicity island, the first one described in E. faecium. Except for the presence of esp and araC, this pathogenicity island is completely different from the esp-containing pathogenicity island previously disclosed in E. faecalis.
Project description:The enterococci comprise a genus of 49 low-GC content Gram-positive commensal species within the Firmicutes phylum that are known to occupy diverse habitats, notably the gastrointestinal core microbiota of nearly every phylum, including human. Of particular clinical relevance are two rogue species of enterococci, Enterococcus faecalis and the distantly related Enterococcus faecium, standing among the nefarious multi-drug resistant and hospital-acquired pathogens. Despite increasing evidence for RNA-based regulation in the enterococci, including regulation of virulence factors, their transcriptome structure and arsenal of regulatory small sRNAs (sRNAs) are not thoroughly understood. Using dRNA-seq, we have mapped at single-nucleotide resolution the primary transcriptomes of E. faecalis V583 and E. faecium AUS0004. We identified 2517 and 2771 transcription start sites (TSS) in E. faecalis and E. faecium, respectively. Based on the identified TSS, we created a global map of s70 promoter motifs. We also revealed features of 5’ and 3’UTRs across the genomes. The transcriptome maps also predicted 150 and 128 sRNA candidates in E. faecalis and E. faecium, respectively, some of which have been identified in previous studies and many of which are new. Finally, we validated several of the predicted sRNAs by Northern Blot in biologically relevant conditions. Comprehensive TSS mapping of two representative strains will provide a valuable resource for the continued development of RNA biology in the Enterococci.
Project description:Nowadays, Enterococcus faecium is one of the leading nosocomial pathogens worldwide. Strains causing clinical infections or hospital outbreaks are enriched in the enterococcal surface protein (Esp) encoding ICEEfm1 mobile genetic element. Previous studies showed that Esp is involved in biofilm formation, endocarditis and urinary tract infections. In this study, we characterized the role of the putative AraC type of regulator (locus tag EfmE1162_2351), which we renamed ebrB and which is, based on the currently available whole genome sequences, always located upstream of the esp gene, and studied its role in Esp surface exposure during growth. A markerless deletion mutant of ebrB resulted in reduced esp expression and complete abolishment of Esp surface exposure, while Esp cell-surface exposure was restored when this mutant was complemented with an intact copy of ebrB. This demonstrates a role for EbrB in esp expression. However, during growth, ebrB expression levels did not change over time, while an increase in esp expression at both RNA and protein level was observed during mid-log and late-log phase. These results indicate the existence of a secondary regulation system for esp, which might be an unknown quorum sensing system as the enhanced esp expression seems to be cell density dependent. Furthermore, we determined that esp is part of an operon of at least 3 genes putatively involved in biofilm formation. A semi-static biofilm model revealed reduced biofilm formation for the EbrB deficient mutant, while dynamics of biofilm formation using a flow cell system revealed delayed biofilm formation in the ebrB mutant. In a mouse intestinal colonization model the ebrB mutant was less able to colonize the gut compared to wild-type strain, especially in the small intestine. These data indicate that EbrB positively regulates the esp operon and is implicated in biofilm formation and intestinal colonization.
Project description:ObjectivesTo evaluate the prevalence of some virulence genes among 510 clinical Enterococcus spp. isolates and to assess the association of those genes with the species, infection site, and patient group (inpatients/outpatients).MethodsAdhesins genes (aggregation substances agg and asa1 of Enterococcus faecalis and Enterococcus faecium, respectively), enterococcal surface protein (esp), endocarditis-specific antigen A (efaA), collagen-binding proteins (ace/acm)); invasins (hyaluronidase (hyl) and gelatinase (gelE)); cytotoxines (activation of cytolysin (cylA) in E. faecalis); and modulators of the host immunity and inflammation (enhanced expression pheromone (eep) in E. faecalis) were detected by polymerase chain reaction.ResultsThe overall prevalence was: esp - 44.3%, agg/asa1 - 38.4%, ace/acm - 64.3%, efaA - 85.9%, eep - 69.4%, gelE - 64.3%, hyl - 25.1%, and cylA - 47.1%. E. faecalis isolates had significantly higher frequency of adhesin genes (esp and agg/asa1) and gelatinase in comparison to E. faecium. Multiple virulence genes in E. faecalis were significantly more prevalent than in E. faecium isolates. Domination of E. faecium with or without only one gene compared to the isolates of E. faecalis were found. Enterococcus spp. isolates obtained from outpatients compared to inpatients isolates had significantly higher frequency of agg/asa1, eep, gelE and cylA. Some adhesins genes (esp, agg/asa1 and efaA) had higher prevalence among the non-invasive Enterococcus spp. isolates compared to those causing invasive bacteremia, while ace/acm revealed higher dissemination in isolates causing invasive infections compared to non-invasive isolates.ConclusionMost E. faecalis attaches to abiotic surfaces in hospital environment, which correlates with higher prevalence of gene encoding for virulence factors involved in biofilm formation, such as enterococcal surface protein, aggregation substance, and gelatinase. The intestinal tract is an important reservoir for opportunistic enterococcal pathogens and allows them to access infectious sites through different virulence factors, demonstrated in outpatient isolates in this study.
Project description:We report the identification of a new cell wall-associated protein of Enterococcus faecalis. Studies on the distribution of the gene encoding this novel surface protein, Esp, reveal a significant (P < 0.001) enrichment in infection-derived E. faecalis isolates. Interestingly, the esp gene was not identified in any of 34 clinical E. faecium isolates or in 4 other less pathogenic enterococcal species tested. Analysis of the structural gene among various E. faecalis isolates reveals the existence of alternate forms of expression of the Esp protein. The deduced primary structure of the Esp protein from strain MMH594, inferred to be 1,873 amino acids (aa) with a predicted mass of approximately 202 kDa, reveals a core region consisting of repeat units that make up 50% of the protein. Esp bears global organizational similarity to the Rib and C alpha proteins of group B streptococci. Identity among Esp, Rib, and C alpha proteins is strikingly localized to a stretch of 13 aa within repeats of similar length. The high degree of conservation of this 13-residue sequence suggests that it plays an important role in the natural selection for this trait among infection-derived E. faecalis and group B streptococcal isolates.