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We report a case of isolated pulmonary native valve infectious endocarditis due to Enterococcus faecalis in a patient without predisposing factors. The early diagnostic suspicion plays a pivotal role in this entity. An individual clinical and echocardiographic management is mandatory in these patients.
Data from culture studies have revealed that Enterococcus faecalis is occasionally isolated from primary endodontic infections but frequently recovered from treatment failures. This molecular study was undertaken to investigate the prevalence of E. faecalis in endodontic infections and to determine whether this species is associated with particular forms of periradicular diseases. Samples were taken from cases of untreated teeth with asymptomatic chronic periradicular lesions, acute apical periodontitis, or acute periradicular abscesses, and from root-filled teeth associated with asymptomatic chronic periradicular lesions. DNA was extracted from the samples, and a 16S rDNA-based nested polymerase chain reaction assay was used to identify E. faecalis. This species occurred in seven of 21 root canals associated with asymptomatic chronic periradicular lesions, in one of 10 root canals associated with acute apical periodontitis, and in one of 19 pus samples aspirated from acute periradicular abscesses. Statistical analysis showed that E. faecalis was significantly more associated with asymptomatic cases than with symptomatic ones. E. faecalis was detected in 20 of 30 cases of persistent endodontic infections associated with root-filled teeth. When comparing the frequencies of this species in 30 cases of persistent infections with 50 cases of primary infections, statistical analysis demonstrated that E. faecalis was strongly associated with persistent infections. The average odds of detecting E. faecalis in cases of persistent infections associated with treatment failure were 9.1. The results of this study indicated that E. faecalis is significantly more associated with asymptomatic cases of primary endodontic infections than with symptomatic ones. Furthermore, E. faecalis was much more likely to be found in cases of failed endodontic therapy than in primary infections.
We report a linezolid-resistant Enterococcus faecalis infection in a cord blood stem cell transplant recipient previously treated with linezolid for bloodstream infections by vancomycin-resistant enterococci. Sequencing showed a G2576U mutation in the 23S rRNA gene. Because of the important niche of linezolid in cancer treatment, linezolid-resistant E. faecalis is noteworthy.
Expression of virulence-related extracellular proteases, gelatinase, and serine protease of Enterococcus faecalis is regulated by a quorum-sensing system encoded by the fsr gene cluster. In this study, a 23.9-kb chromosomal deletion containing the fsr gene cluster region was found to be present in the majority (79%) of gelatinase-negative clinical isolates of E. faecalis from urine.
Pheromone-responsive plasmids are common to Enterococcus faecalis, transfer at high frequency in vitro, and carry cytolysin and other gene products implicated in the pathogenesis of enterococcal infection. A Syrian hamster model of enterococcal intestinal overgrowth was used to test for transfer of three isogenic plasmids differing in conjugative and cytolytic phenotypes. Transconjugants were found in 8 (44%) of 18 and 6 (35%) of 17 hamsters given donor strains containing cytolytic (pAM714) and noncytolytic (pAM771) pheromone-responsive plasmids. Of the 14 hamsters from which transconjugants were isolated from stool, 9 (64%) had transconjugants 1 day after donor strain inoculation. The frequency of transfer (mean +/- SD) for pAM714 and pAM771 was 1.4 +/- 2.2 x 10(-1) and 2.9 +/- 4.2 x 10(-2) transconjugants/donor, respectively (P > .20). Transconjugants were not recovered from hamsters receiving a cytolytic, nonconjugative plasmid (pAM930; transfer frequency < 2 x 10(-5) transconjugants/donor). Pheromone-responsive plasmid transfer between E. faecalis strains occurs at high frequency in the gastrointestinal tract of hamsters and may be one means by which enterococcal resistance and virulence factors disseminate.
This study investigated the differences among Enterococcus faecalis isolates from the intestinal compartment of healthy volunteers (n = 36), intensive care unit (ICU) patients (n = 29) and blood isolates (n = 31) from the same institution, in comparison with seven epidemic clones from other institutions. In general, isolates from colonised ICU patients and from bacteraemic patients showed higher rates of antimicrobial resistance than isolates from colonised healthy volunteers, particularly for erythromycin and aminoglycosides. The proportion of isolates/clone was 1.05 in the community, 2.63 in the ICU, and 1.47 among bacteraemic cases, suggesting low clonal variation in ICUs. Two clones, RENC1 and RENC2, were frequently found as intestinal colonisers of ICU patients, and RENC1 was also found to colonise healthy volunteers. These two clones were a cause of bacteraemia in the institution studied, and RENC2 was also detected in various other Spanish hospitals. Both RENC1 and RENC2 were esp+, bacteriocin producers, and were resistant to all antibiotics tested except vancomycin and ampicillin. RENC1 produced haemolysin whereas RENC2 produced protease. The ace, agg, cylA, esp and gelE genes were more common among colonising strains from ICU patients than among isolates from individuals in the community. In both colonised groups (ICUs and the community), 40-50% of isolates harbouring the gelE and cylA genes did not express the corresponding phenotypes. Thus, the study indicated that particular E. faecalis clones might be well-adapted to hospital environments, and that surveillance should be directed specifically towards rapid detection of these disseminating clones in order to prevent infections and clonal spread.
The recA gene of the recombination deficient Enterococcus faecalis strain UV202 was sequenced and found to encode a glycine to aspartic acid mutation at amino acid 265. Both the UV sensitive and recombination deficient phenotypes of the UV202 strain were complemented by expression of the wild-type recA gene cloned under the control of the nisin-inducible promoter of an expression vector.
Enterococcus faecalis (Ef) dnaE and polC, the respective genes encoding the DNA replication-specific DNA polymerase III E and DNA polymerase III C, were cloned and engineered for expression in Escherichia coli as hexahistidine (his6)-tagged recombinant proteins. Each gene expressed a catalytically active DNA polymerase of the expected molecular weight. The recombinant polymerases were purified and each was characterized with respect to catalytic properties, inhibitor sensitivity, and recognition by specific antibody raised against the corresponding DNA polymerase III of the model Gram-positive (Gr(+)) organism, Bacillus subtilis (Bs). In conclusion, the properties of each Enterococcus polymerase enzymes were similar to those of the respective B. subtilis enzymes.
Synergy of 14 Enterococcus faecalis strains displaying moderately high-level aminoglycoside resistance (MICs, 500 and 256 to 1,000 micrograms/ml for gentamicin and streptomycin, respectively) was characterized by time-kill studies. All strains proved resistant to penicillin plus the respective aminoglycoside. Strains with moderately high-level aminoglycoside resistance should be considered to exhibit high-level resistance in severe infections.
A 16S rDNA real-time PCR method was developed to detect Enterococcus faecalis in water samples. The dynamic range for cell detection spanned five logs and the detection limit was determined to be 6 cfu/reaction. The assay was capable of detecting E. faecalis cells added to biofilms from a simulator of a water distribution system and in freshwater samples. Nucleic acid extraction was not required, permitting the detection of E. faecalis cells in less than 3 h.
Strains of Enterococcus faecalis carrying the bacteriocinogenic plasmids pMB1 or pMB1.1 exhibit a clumping response to culture supernatants of different enterococcal strains. Antibodies raised against cells induced by a homologous pheromone recognize two surface proteins of 152 and 72.5 kDa (the second one is possibly the degradation product of the first), respectively. These antigens are very similar to those found in induced cells of E. faecalis OGIRF(pAM211) as shown by the cross-reaction of the immune sera obtained in this work. We propose that the 152-kDa protein corresponds to the aggregation substance coded by plasmids pMB1 and pMB1.1. Moreover, antibodies raised against induced cells are able to block the pheromone-induced clumping response. When the cells induced to form aggregates by pheromones were examined under a scanning electron microscope they showed a surface layer of hairlike structures.
This study assessed the effect of bacteriophages on the viability of Enterococcus faecalis. Human dental roots were inoculated with a suspension of E. faecalis at three different multiplicities of infection - 0.1, 1.0 and 10.0. The phage lysate was able to significantly inhibit bacteria growth when incubated at the multiplicities of infection of 1.0, 10.0 and 0.1. The dental roots were also inoculated with bacteria for 6 days to allow bacterial penetration into the teeth tubules. Addition of the phage lysate to the roots following the 6-day incubation period led to a substantial reduction in bacteria viability. Phage therapy may be an important alternative for the treatment of root canal infections refractory to conventional endodontic therapy.
Atrazine solutions (0.1, 1, 10 and 100 microg/L) inoculated with Escherichia coli and Enterococcus faecalis under natural conditions significantly increased (p < or = 0.05) the population levels of both test bacteria; it indicates the ability of bacterial cells to degrade atrazine and to use the original compound or its degradation products as nutrient(s). In some cases, alterations in the morphology of the colonies were also observed on selective solid media. Biochemical differentiation was also found and, on the other hand, a loss of culturability was recorded; this suggests that bacteria have entered in a viable but nonculturable state. A re-appearance of the colonies occurred after inoculation on tryptone-soy agar with atrazine.
From Enterococcus faecalis cells containing random chromosomal insertions of Tn916, strains resistant to a lytic phage were selected and tested for conjugal mating ability. The phage-resistant strains all showed decreased recipient ability (Con-) in broth matings with donors carrying pheromone-inducible plasmids. These strains were normal with respect to donor ability in broth matings and recipient ability in filter matings. The data suggest that the mutants are deficient in the binding substance receptor for the pheromone-induced donor aggregation substance. These mutants contained multiple insertions of Tn916, and none of the individual insertions from the mutant strains were capable of generating the phenotype. Analysis of cell envelope lipoteichoic acids and protein revealed changes in both associated with the Con- phenotype.
The gene coding for gelatinase (also called metalloendopeptidase II; microbial proteinase, EC 3.4.24.4) of Enterococcus faecalis subsp. liquefaciens strain OG1-10 was cloned in an Escherichia coli-Enterococcus shuttle vector, and its nucleotide sequence was determined. The DNA sequence encodes one large open reading frame (ORF) with 509 amino acid residues. The ORF contains a signal sequence in its N-terminal region, whereas the N-terminal amino acid sequence determined from the purified extracellular proteinase starts at residue 192 deduced from the ORF. This implies that the gelatinase is synthesized as a prepropolypeptide or prezymogen. The mature gelatinase contains 318 amino acid residues (molecular weight, 34,582) and has significant homology with neutral proteinases from Bacillus species and elastase from Pseudomonas aeruginosa.
The high transfer frequency of pheromone-inducible conjugative plasmids of Enterococcus faecalis in liquid culture is due in part to the formation of mating aggregates. These aggregates result from the interaction of two surface components, aggregation substance (AS), which is plasmid encoded, and the chromosomally encoded binding substance (BS). In the accompanying paper (S.-M. Kao, S. B. Olmsted, A. S. Viksnins, J.C. Gallo, G. M. Dunny, J. Bacteriol, 173:7650-7664, 1991), the sequence of the prgB gene encoding the AS molecule (Asc10) produced by pheromone-induced cells carrying plasmid pCF10 is presented. Here we report the results of genetic and immunological experiments which define the role of Asc10 in aggregation and plasmid transfer. These data indicate expression of AS on the surface of an E. faecalis cell and its binding to BS expressed on a second cell are required for the formation of a mating pair and the efficient transfer of pCF10 in liquid matings. However, the orientation of the receptors was not critical for transfer; ie., AS expressed on recipient cells could facilitate plasmid transfer via binding to BS on the donor. Our results suggest that additional (as yet unidentified) products are involved in forming the channel that ultimately serves to transfer the DNA, with AS-BS binding serving primarily to generate the initial attachment between cells. The putative prgC gene product, identified by DNA sequencing (data presented in the accompanying paper), could be involved in transfer events occurring subsequent to aggregation.
Hybridization of EcoRI- and HindIII-digested chromosomal DNAs from 41 isolates of Enterococcus faecalis with probes for rRNA genes was performed (ribotyping). The ability of ribotyping to distinguish strains at the subspecies level was compared with results previously determined by pulsed-field gel electrophoresis (PFGE). With EcoRI, seven ribopatterns (usually differing by only one band) were found, while PFGE had previously shown 25 clearly different patterns plus six related variants. Digestion with HindIII generated a few additional patterns but still failed to differentiate some strains that had very different PFGE patterns. Ribotyping with BscI has also been reported to be inadequate for subspecies strain differentiation (L. M. Hall, B. Duke, M. Guiney, and R. Williams, J. Clin. Microbiol. 30:915-919, 1992). Although ribotyping with other restriction endonucleases may perform better in distinguishing different strains, at present PFGE appears to be superior for strain differentiation.
Inactivation of ccpA in Enterococcus faecalis leads to reduction of the growth rate, derepression of the galKETR operon in the presence of a mixture of glucose and galactose, and reduction of transcription of ldh in the presence of glucose. Moreover, the E. faecalis ccpA gene fully complements a Bacillus subtilis ccpA mutant, arguing for similar functions of these two homologous proteins. Protein comparison on two-dimensional gels from the wild-type cells and the ccpA mutant cells revealed a pleiotropic effect of the mutation on gene expression. The HPr protein of the carbohydrate-phosphotransferase system was identified by microsequencing, and a modification of its phosphorylation state was observed between the wild-type and the mutant strains. Moreover, at least 16 polypeptides are overexpressed in the mutant, and 6 are repressed. Interestingly, 13 of the 16 polypeptides whose synthesis is enhanced in the mutant were also identified as glucose starvation proteins. The N-terminal amino acid sequences of four of them match sequences deduced from genes coding for L-serine dehydratase, dihydroxyacetone kinase (two genes), and a protein of unknown function from Deinococcus radiodurans.