Molecular characterization of a widespread, pathogenic, and antibiotic resistance-receptive Enterococcus faecalis lineage and dissemination of its putative pathogenicity island.

Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, 6431 Fannin Street, MSB 2.112, Houston, TX 77030, USA.
Journal of Bacteriology (Impact Factor: 2.69). 09/2005; 187(16):5709-18. DOI: 10.1128/JB.187.16.5709-5718.2005
Source: PubMed

ABSTRACT Enterococcus faecalis, a common cause of endocarditis and known for its capacity to transfer antibiotic resistance to other pathogens, has recently emerged as an important, multidrug-resistant nosocomial pathogen. However, knowledge of its lineages and the potential of particular clones of this species to disseminate and cause disease is limited. Using a nine-gene multilocus sequence typing (MLST) scheme, we identified an evolving and widespread clonal complex of E. faecalis that has caused outbreaks and life-threatening infections. Moreover, this unusual clonal complex was found to contain isolates of unexpected relatedness, including the first known U.S. vancomycin-resistant enterococcus (E. faecalis strain V583), the first known penicillinase-producing (Bla(+)) E. faecalis isolate, and the previously described widespread clone of penicillinase producers, a trait found in <0.1% of E. faecalis isolates. All members of this clonal cluster (designated as BVE for Bla(+) Van(r) endocarditis) were found to contain a previously described putative pathogenicity island (PAI). Further analysis of this PAI demonstrated its dissemination worldwide, albeit with considerable variability, confirmed its association with clinical isolates, and found a common insertion site in different clonal lineages. PAI deletions, MLST, and the uncommon resistances were used to predict the evolution of the BVE clonal cluster. The finding of a virulent and highly successful clonal complex of E. faecalis with different members resistant to the primary therapies of choice, ampicillin and vancomycin, has important implications for the evolution of virulence and successful lineages and for public health monitoring and control.

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    ABSTRACT: Background Scientific interest in Enterococcus faecalis has increased greatly over recent decades. Some strains are involved in food fermentation and offer health benefits, whereas others are vancomycin-resistant and cause infections that are difficult to treat. The limited availability of vectors able to express cloned genes efficiently in E. faecalis has hindered biotechnological studies on the bacterium¿s regulatory and pathogenicity-related genes. The agmatine deiminase (AGDI) pathway of E. faecalis, involved in the conversion of agmatine into putrescine, is driven by a response inducer gene aguR.ResultsThis study describes that the exposure to the induction factor (agmatine) results in the transcription of genes under the control of the aguB promoter, including the aguBDAC operon. A novel E. faecalis expression vector, named pAGEnt, combining the aguR inducer gene and the aguB promoter followed by a cloning site and a stop codon was constructed. pAGEnt was designed for the overexpression and purification of a protein fused to a 10-amino-acid His-tag at the C-terminus. The use of GFP as a reporter of gene expression in E. faecalis revealed that under induction with 60 mM agmatine, fluorescence reached 40 arbitrary units compared to 0 in uninduced cells.ConclusionpAGEnt vector can be used for the overexpression of recombinant proteins under the induction of agmatine in E. faecalis, with a close correlation between agmatine concentration and fluorescence when GFP was used as reporter.
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    ABSTRACT: The diversity of enterococcal populations from fecal samples of hospitalized (n=133) and non-hospitalized individuals (n=173) of different age groups (I:0-19y; II:20-59y; III:≥60y) was analyzed. Enterococci were recovered at similar rates among hospitalized and non-hospitalized persons (77.44%-79.77%) of all age groups (75.0%-82.61%). Enterococcus faecalis (Efc) and Enterococcus faecium (Efm) were predominant although seven other Enterococcus species were identified. Efc and Efm (including ampicillin-resistant-Efm, AREfm) colonization rates in non-hospitalized persons were age-independent. For inpatients, Efc colonization rates were age-independent, but Efm rates (particularly AREfm) significantly increased with age. The population structure of Efm and Efc was determined by superimposing goeBURST and Bayesian Analysis of Population Structure (BAPS). Most Efm STs (150, 75 STs) were linked to BAPS groups 1 (22.0%), 2 (31.3%) and 3 (36.7%). Positive association was found between hospital isolates and BAPS 2.1a and 3.3a (which included major AREfm human lineages), and between community-based ASEfm isolates and BAPS 1.2 and 3.3b. Most Efc isolates (130, 58 STs) were grouped in 3 BAPS: 1 (36.9%), 2 (40.0%) and 3 (23.1%), each one comprising widespread lineages. No positive associations with age or hospitalization were established. The diversity and dynamics of enterococcal populations in fecal microbiota of healthy humans is largely unexplored, available knowledge being fragmented and contradictory. The study offers a novel and comprehensive analysis of enterococcal population landscapes and suggests that Efm populations from hospitalized patients and from community-based individuals differ, with predominance of certain clonal lineages in the hospital setting, often associated with elderly. Copyright © 2014, American Society for Microbiology. All Rights Reserved.
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    ABSTRACT: Enterococcus faecalis (E. faecalis) is a common cause of nosocomial infection in immunocompromised patients. The presence and dissemination of high-risk clonal complexes, such as CC2, is an ongoing problem in hospitals. The aim of this work was to characterize 24 E. faecalis isolates from ICU patients undergoing selective decontamination of the digestive tract (SDD) by phenotypical (antimicrobial susceptibility) and genotypical (presence of virulence genes, RAPD-PCR and MLST) methods. Our results showed high prevalence of the ST6 E. faecalis clone (91.6%), especially adapted to the hospital environment, with a multidrug resistance pattern and a multitude of putative virulence genes. In addition, ST179 (4.2%) and ST191 (4.2%) were detected. By RAPD-PCR analysis, the 22 isolates identified as ST6 showed six different DNA patterns, while the two remaining isolates, ST179 and ST191, showed two additional profiles. CC2 is a known clonal complex with high adaptability to hospital environment and worldwide distribution. The high prevalence of the ST6 clone in the studied population could be related to the presence of gentamicin in the SDD mixture since most strains were gentamicin resistant. Consequently, strict surveillance should be applied for rapid detection and control of this clone to prevent future spread outside the ICU. © 2015 APMIS. Published by John Wiley & Sons Ltd.
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