PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Enterococcus faecalis”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed1997

Molecular typing of Enterococcus faecalis strains resistant to high levels of gentamicin and isolated in Romania.

Sixteen Enterococcus faecalis strains resistant to high levels of gentamicin, 15 of which were isolated in the same year in a Romanian hospital, harboured conjugative gentamicin resistance (Gm(r)) plasmids ranging from 55 to 85 kilobases. On the basis of restriction enzyme and DNA-DNA hybridization profiles of these plasmids, as well as of chromosomal SmaI macrorestriction and Tn916 hybridization patterns, clonal relationship was established for seven strains whereas the other strains were considered to be independent. Nine and seven of the Gm(r) plasmids carried Tn4001-like and Tn4001-truncated structures, respectively; the latter structures were truncated in the right-hand flanking extremity of the element.

Chromosomes, Bacterial↗
PubMed2001

Antimicrobial activity of Ca(OH)2 containing pastes with Enterococcus faecalis in vitro.

Sixty-eight standardized human root specimens were infected with Enterococcus faecalis for 3 wk after removal of the smear layer. After 3 wk of infection, the smear layer was reformed and in half of the specimens, the smear layer was again removed. Aqueous Ca(OH)2 paste and silicone oil based Ca(OH)2 paste were used as the test medications. The specimens were divided into four groups (i.e. (a) nonsmeared aqueous calcium hydroxide group, (b) nonsmeared silicon oil-based calcium hydroxide group, (c) smeared aqueous calcium hydroxide group, and (d) smeared silicon oil-based calcium hydroxide group. Medications were placed in the canals for 7 days. After removal of medications dentin chips were collected and incubated. The quantity of bacteria present was assessed. All calcium hydroxide pastes were effective in the elimination of bacteria in the dentinal tubules, except in the smeared group with silicone oil-based calcium hydroxide.

Calcium Hydroxide↗
PubMed2004

Antisense RNA regulation by stable complex formation in the Enterococcus faecalis plasmid pAD1 par addiction system.

The par stability determinant, encoded by the Enterococcus faecalis plasmid pAD1, is the only antisense RNA regulated postsegregational killing system identified in gram-positive bacteria. Because of the unique organization of the par locus, the par antisense RNA, RNA II, binds to its target, RNA I, at relatively small, interspersed regions of complementarity. The results of this study suggest that, rather than targeting the antisense bound message for rapid degradation, as occurs in most other antisense RNA regulated systems, RNA I and RNA II form a relatively stable, presumably translationally inactive complex. The stability of the RNA I-RNA II complex would allow RNA I to persist in an untranslated state unless or until the encoding plasmid was lost. After plasmid loss, RNA II would be removed from the complex, allowing translational activation of RNA I. The mechanism of RNA I activation in vivo is unknown, but in vitro dissociation experiments suggest that active removal of RNA II, for example by a cellular RNase, may be required.

Amino Acid Sequence↗
PubMed2004

Expression cloning and demonstration of Enterococcus faecalis lipoamidase (pyruvate dehydrogenase inactivase) as a Ser-Ser-Lys triad amidohydrolase.

Enterococcus faecalis lipoamidase was discovered almost 50 years ago (Reed, L. J., Koike, M., Levitch, M. E., and Leach, F. R. (1958) J. Biol. Chem. 232, 143-158) as an enzyme activity that cleaved lipoic acid from small lipoylated molecules and from pyruvate dehydrogenase thereby inactivating the enzyme. Although the partially purified enzyme was a key reagent in proving the crucial role of protein-bound lipoic acid in the reaction mechanism of the 2-oxoacid dehydrogenases, the identity of the lipoamidase protein and the encoding gene remained unknown. We report isolation of the lipoamidase gene by screening an expression library made in an unusual cosmid vector in which the copy number of the vector is readily varied from 1-2 to 40-80 in an appropriate Escherichia coli host. Although designed for manipulation of large genome segments, the vector was also ideally suited to isolation of the gene encoding the extremely toxic lipoamidase. The gene encoding lipoamidase was isolated by screening for expression in E. coli and proved to encode an unexpectedly large protein (80 kDa) that contained the sequence signature of the Ser-Ser-Lys triad amidohydrolase family. The hexa-histidine-tagged protein was expressed in E. coli and purified to near-homogeneity. The purified enzyme was found to cleave both small molecule lipoylated and biotinylated substrates as well as lipoic acid from two 2-oxoacid dehydrogenases and an isolated lipoylated lipoyl domain derived from the pyruvate dehydrogenase E2 subunit. Lipoamidase-mediated inactivation of the 2-oxoacid dehydrogenases was observed both in vivo and in vitro. Mutagenesis studies showed that the residues of the Ser-Ser-Lys triad were required for activity on both small molecule and protein substrates and confirmed that lipoamidase is a member of the Ser-Ser-Lys triad amidohydrolase family.

Amidohydrolases↗
PubMed1999

Vancomycin-dependent Enterococcus faecalis clinical isolates and revertant mutants.

Three vancomycin-dependent clinical isolates of Enterococcus faecalis of the VanB type were studied by determining (i) the sequence of the ddl gene encoding the host D-Ala:D-Ala ligase and the vanSB-vanRB genes specifying the two-component regulatory system that activates transcription of the vanB operon, (ii) the level of expression of resistance genes by using DD-dipeptidase activity as a reporter, and (iii) the proportions of the peptidoglycan precursors synthesized. Each strain had a mutation in ddl leading to an amino acid substitution (D295 to V; T316 to I) or deletion (DAK251-253 to E) at invariant positions in D-Ala:D-Ala, D-Ala:D-Lac, and D-Ala:D-Ser ligases. These mutations resulted in impaired host D-Ala:D-Ala ligases since only precursors terminating in D-Ala-D-Lac were synthesized under vancomycin-inducing conditions. Two types of vancomycin-independent revertants of one isolate were obtained in vitro after growth in the absence of vancomycin: (i) vancomycin-resistant, teicoplanin-susceptible mutants had a 6-bp insertion in the host ddl gene, causing the E251-to-EYK change that restored D-Ala:D-Ala ligase activity, (ii) constitutive vancomycin-resistant, teicoplanin-resistant mutants had substitutions (S232 to F or E247 to K) in the vicinity of the autophosphorylation site of the VanSB sensor and produced exclusively precursors ending in D-Ala-D-Lac. Vancomycin- and teicoplanin-dependent mutants obtained by growth in the presence of teicoplanin had an 18-bp deletion in VanSB, affecting residues 402 to 407 and overlapping the G2 ATP binding domain. The rapid emergence of vancomycin-independent revertants in vitro suggests that interruption of vancomycin therapy may not be sufficient to cure patients infected with vancomycin-dependent enterococci.

Anti-Bacterial Agents↗
PubMed1996

Glycopeptide susceptibility among Danish Enterococcus faecium and Enterococcus faecalis isolates of animal and human origin and PCR identification of genes within the VanA cluster.

The MICs of vancomycin and avoparcin were determined for isolates of Enterococcus faecium and isolates of Enterococcus faecalis recovered from the feces of humans and animals in Denmark. Two hundred twenty-one of 376 (59%) isolates of E. faecium and 2 of 133 (1.5%) isolates of E. faecalis were resistant to vancomycin (MICs, 128 to > or = 256 micrograms/ml), and all vancomycin-resistant isolates were resistant to avoparcin (MICs, 64 to > or = 256 micrograms/ml). All vancomycin-resistant isolates examined carried the vanA, vanX, and vanR genes, suggesting that a gene cluster similar to that of the transposon Tn1546 was responsible for the resistance.

Animals↗
PubMed2000

Isolation of Enterococcus faecalis in previously root-filled canals in a Lithuanian population.

The occurrence of Enterococcus faecalis in root canals of previously root filled teeth with apical periodontitis requiring retreatment was studied in Lithuanian patients. Twenty-five asymptomatic teeth were included in the study. Avoiding contamination microbiological samples were taken from the canals before and after preparation and irrigation with sodium hypochlorite and EDTA. Microbes were isolated from 20 of 25 teeth. E. faecalis was isolated from 14 of those 20 culture positive teeth, usually in pure culture or as a major component of the flora. Second samples taken after preparation revealed growth in 7 of the 20 teeth. Five of the seven cases were E. faecalis in pure culture. Isolation of E. faecalis was not related to the use of any particular root filling material in the original root filling. The results indicate that, rather than previous chemical treatment, it is the ecological conditions present in the incompletely filled root canal that are important for the presence of E. faecalis in these teeth.

Bacteriological Techniques↗
PubMed1994

The sex pheromone system of Enterococcus faecalis. More than just a plasmid-collection mechanism?

The sex pheromone system of Enterococcus faecalis was discovered by observing a clumping reaction of E. faecalis strains during conjugative transfer of plasmids. It was found that only a special type of E. faecalis plasmids, the so-called sex pheromone plasmids, are transferred via this mechanism. Various experiments, especially by the group of D. B. Clewell, led to the formulation of a model describing how the sex pheromone system works. Small linear peptides, the so-called sex pheromones, are excreted by strains not possessing the corresponding sex pheromone plasmid. Donor strains harboring the plasmid do not produce the corresponding sex pheromone; they react to the presence of the peptide by production of a plasmid-encoded adhesin, the so-called aggregation substance. This adhesin allows contact between the non-motile mating partners; after conjugative transfer of the plasmid, the former recipient possesses and replicates the new plasmid. Thereby the population of E. faecalis strains is shifted to a high percentage of donor strains. This is especially true because a donor strain will still excrete sex pheromones corresponding to plasmids it does not harbor; therefore, such a strain can also function as recipient for other sex pheromone plasmids it does not possess. Various aspects of this unique plasmid collection mechanism have been studied during the last few years. The data indicate that, with the exception of pAM373, all sex pheromone plasmids possess one DNA region which is highly similar to and codes for the adhesin. It is also becoming more and more clear that regulatory functions/proteins are not conserved between different sex pheromone plasmids. Induction of adhesin synthesis needs the action of a regulatory cascade composed of unique features; at the moment we are just beginning to understand this cascade. By sequencing the first structural gene for one of those adhesins, we realized that the aggregation substance might act also as an adhesin for eucaryotic cells, probably by interaction with integrins. At least in the case of the in vitro cultured pig kidney tubulus cell line LLC-PK1 this idea could be verified. An interesting aspect of the sex pheromone system of E. faecalis is its evolution. I will discuss the idea that two different components, both of which well might contribute to virulence of the opportunistic pathogenic bacterium, were combined in the species E. faecalis to result in this unique plasmid collection system.

Adhesins, Bacterial↗
PubMed2005

Fsr-independent production of protease(s) may explain the lack of attenuation of an Enterococcus faecalis fsr mutant versus a gelE-sprE mutant in induction of endocarditis.

An Enterococcus faecalis gelE insertion disruption mutant (TX5128), which produces neither gelatinase (GelE) nor the cotranscribed (in the wild type) serine protease (SprE), was found to be attenuated in a rat endocarditis model with a significant decrease in the endocarditis induction rate versus wild-type E. faecalis OG1RF (GelE(+), SprE(+)). TX5266, which has a nonpolar deletion in fsrB and, like TX5128, is phenotypically GelE(-) under usual conditions, was also studied; fsrB is a homologue of agrB of staphylococci and participates in regulation of gelE-sprE expression. Unexpectedly, TX5266 approximated wild-type OG1RF in the endocarditis model and was significantly less attenuated than TX5128. This is in contrast to other models which have found fsr mutants to be as or more attenuated than TX5128. Further study found that the fsrB mutant produced very low levels of gelatinase activity after prolonged incubation in vitro versus no gelatinase activity with TX5128 and did not show the extensive chaining characteristic of TX5128. Reverse transcription-PCR confirmed that gelE was expressed in TX5266 at a very low level versus wild-type OG1RF and was not expressed at all in TX5128. Possible explanations for the increased induction of endocarditis by TX5266 versus TX5128 include the production of low levels of protease(s) or some other effect(s) of the inactivation of the E. faecalis fsr regulator. The equivalent ability of OG1RF and its fsr mutant to initiate endocarditis may explain why we did not find naturally occurring fsr mutants, which account for ca. 35% of E. faecalis isolates, unrepresented in endocarditis versus fecal isolates.

Animals↗
PubMed1992

Teicoplanin versus vancomycin for prophylaxis of experimental Enterococcus faecalis endocarditis in rats.

Teicoplanin was compared with vancomycin for the prophylaxis of experimental Enterococcus faecalis endocarditis in rats. Single intravenous doses of teicoplanin (7 mg/kg of body weight) or vancomycin (15 mg/kg) were given 30 min before bacterial challenge. Two strains of E. faecalis (309 and 1209) isolated from patients with endocarditis were tested. Bacterial inocula ranged from 10(4) (i.e., the inoculum infecting 90% of the control rats [ID90]) to 10(7) CFU/ml. The MICs and MBCs of teicoplanin and vancomycin were, respectively, 0.25 to greater than 128 mg/liter and 2 to greater than 128 mg/liter for strain 309 and 0.5 to greater than 128 mg/liter and 0.5 to greater than 128 mg/liter for strain 1209. Vancomycin prevented endocarditis only in 60% (strain 309) and in 87% (strain 1209) of rats challenged with the smallest bacterial-inoculum size (ID90), whereas teicoplanin prevented endocarditis in 100% of rats challenged with the same inoculum (strain 309; P = 0.05), in 87% of rats challenged with 10 times the ID90 (strain 309; P = 0.02), and in 95% of rats challenged with 100 times the ID90 (strain 1209; P = 0.0003). The combination of teicoplanin plus gentamicin (4 mg/kg) extended the protection to inocula 100 times the ID90 (strain 309; 96% of sterile animals) and 1,000 times the ID90 (strain 1209; 100% of sterile animals). Prevention of endocarditis was likely to be due to a prolonged inhibition of bacterial growth by sustained levels of teicoplanin in serum and not to bacterial killing. Indeed, teicoplanin did not exhibit any bactericidal activity either in vitro (time-kill curves) or in vivo (serum bactericidal activity). Teicoplanin proved to be superior to vancomycin in the prophylaxis of experimental E. faecalis endocarditis in rats.

Animals↗
PubMed1991

The fluoroquinolones exert a reduced rate of kill against Enterococcus faecalis.

The bactericidal activities of ciprofloxacin, ofloxacin and DR-3355 have been investigated against Enterococcus faecalis, Staphylococcus aureus and Staphylococcus epidermidis over 24 h. The three fluoroquinolones were found to be rapidly bactericidal against the staphylococci, killing over 99% of the bacteria during the first 3 h of exposure with a further reduction in viability of approximately one logarithm occurring over the next 21 h. In contrast, the fluoroquinolones displayed a much slower rate of kill against E. faecalis, as little or no bactericidal activity was detected over the first 3 h for both E. faecalis ATCC19433 and a clinical isolate. At 6 h all three of the drugs were bactericidal against the enterococci although the amount of kill was not as great as against the staphylococci. However, at 24 h the amount of kill obtained with all three drugs was similar to that obtained for staphylococci exposed to these drugs. Ciprofloxacin, ofloxacin and DR-3355 were not active against E. faecalis ATCC19433 in phosphate buffered saline and therefore require cell division for their bactericidal activity against this species.

Anti-Infective Agents↗
PubMed1993

Cytotoxic effect of hemolytic culture supernatant from Enterococcus faecalis on mouse polymorphonuclear neutrophils and macrophages.

We reconfirmed that the LD50s of hemolytic Enterococcus faecalis strains were significantly less than those of nonhemolytic E. faecalis strains in normal mice. Hemolysin produced by E. faecalis lysed human, horse, rabbit, and mouse erythrocytes, but not cow and sheep erythrocytes. Sphingomyelin comprises a part of the lipid composition of the erythrocyte membrane of all mammalian species tested. But phosphatidylcholine exists only in human, horse, rabbit, and mouse. These two lipids inhibited lysis of horse erythrocytes by hemolytic E. faecalis. Phosphatidylcholine is probably the binding component on the membrane of erythrocytes for E. faecalis hemolysin. The hemolytic culture supernatant lysed not only erythrocytes but also mouse polymorphonuclear neutrophils (PMNs) and macrophages.

Animals↗
PubMed1988

Impact of LY146032 on Streptococcus (Enterococcus) faecalis translocation in mice.

The susceptibility of Swiss White mice to colonization with Streptococcus (Enterococcus) faecalis was greatly increased when the animals were given 5 mg of streptomycin sulfate per ml in their drinking water. One week after initiation of streptomycin treatment, the mice were challenged orogastrically with graded doses of streptomycin-resistant S. faecalis. The number of S. faecalis cells required to implant the intestinal tract of 50% of untreated mice was 2.9 X 10(9), but was only 4.8 X 10(3) for streptomycin-treated animals. When both groups of mice were challenged orogastrically with 4.6 X 10(6) viable S. faecalis cells, the cecum and small intestine of 100% of the streptomycin-treated animals, but only 10% of the untreated animals, were colonized with the organism. Similarly, translocation of S. faecalis to extraintestinal sites occurred in a majority of streptomycin-treated mice, but in only a small number of untreated mice. Subcutaneous administration of the experimental antibiotic LY146032 (Eli Lilly & Co., Indianapolis, Ind.) to streptomycin-treated mice concomitant with orogastric challenge with 5.5 X 10(5) viable S. faecalis cells resulted in a significant decrease in the incidence of intestinal colonization by the organism, a significant reduction in S. faecalis populations, and the absence of the organism in the liver, spleen, and heart. However, once intestinal colonization had occurred and extraintestinal infections were established, LY146032 did not significantly reduce S. faecalis populations or ameliorate the infections. We conclude that LY146032 effectively prevents translocation of S. faecalis from the intestinal tract of mice but does not resolve established extraintestinal infections.

Animals↗
PubMed2003

Intravenous mouse infection model for studying the pathology of Enterococcus faecalis infections.

An intravenous mouse infection model was used to compare the virulence of Enterococcus faecalis strains, to study bacterial localization and organ histopathology, and to examine the effects of Nramp1 and gamma interferon (IFN-gamma) on the course of infection. Infection of BALB/c mice with 5 x 10(8) CFU of E. faecalis JH2-2, MGH-2, 418, DS16C2, or OG1X revealed the following virulence ranking (from highest to lowest): MGH-2, 418, DS16C2, JH2-2, and OG1X. Discernible differences in the number of MGH-2 and JH2-2 bacteria were observed at 7 days (168 h) in the blood (P = 0.037), at 72 h in the liver (P = 0.002), and at 8 h in the spleen (P = 0.036). At these time points, the number of MGH-2 bacteria was higher in the blood and liver while the number of JH2-2 bacteria was higher in the spleen. At 72 h, livers from MGH-2-infected mice had higher numbers of coalescing aggregates of leukocytes and a greater degree of caseous necrosis than those from JH2-2-infected mice. These results indicate a correlation between the virulence of the E. faecalis strain, the number of bacteria in the liver, and the degree of histopathology of the liver at 72 h postinfection. IFN-gamma was important in E. faecalis infection, since IFN-gamma gene knockout mice had reduced mortality and massive coagulative necrosis was observed in wild-type mice. The contribution of Nramp1 was unclear, since Nramp1(-/-) mice and the respective control mice were innately resistant to E. faecalis. The mortality of mice in this model is probably due to induction of cytokine release and massive coagulative necrosis.

Animals↗
PubMed1996

Comparison of the bile salts and sodium dodecyl sulfate stress responses in Enterococcus faecalis.

The resistance to detergents and detergent-induced tolerance of a gastrointestinal organism, Enterococcus faecalis ATCC 19433, were examined. The most remarkable observation was the rapid response of cells in contact with bile salts and sodium dodecyl sulfate (SDS). The killing by high concentrations of detergents was nearly instantaneous. A 5-s adaptation with moderate sublethal concentrations of bile salts or SDS (0.08 or 0.01%, respectively) was sufficient to induce significant adaptation against homologous lethal conditions (0.3% bile salts or 0.017% SDS). However, resistance to a subsequent lethal challenge progressively increased further to a maximum reached after 30 min of adaptation. Furthermore, extremely strong cross-resistances were observed with bile salts- and SDS-adapted cells. However, no relationship seems to exist between levels of tolerance and de novo-synthesized proteins, since blockage of protein synthesis during adaptation had no effect on induction of resistance to bile salts and SDS. We conclude that this induced tolerance to detergent stress is independent of protein synthesis. Nevertheless, the stress-induced protein patterns of E. faecalis ATCC 19433 showed significant modifications. The rates of synthesis of 45 and 34 proteins were enhanced after treatments with bile salts and SDS, respectively. In spite of the overlap of 12 polypeptides, the protein profiles induced by the two detergents were different, suggesting that these detergents trigger different responses in E. faecalis. Therefore, bile salts cannot be substituted for SDS in biochemical detergent shock experiments with bacteria.

Adaptation, Physiological↗
PubMed2005

Clinical implications of biofilm formation by Enterococcus faecalis in the urinary tract.

The potential relationships between biofilm formation and pathogenicity of Enterococcus faecalis in urinary tract infections (UTI) were investigated. Over a 12-year period from 1991 through 2002, a total of 352 E.faecalis isolates were collected from patients with complicated UTI (one isolate per patient) at the urology ward of Okayama University Hospital. We analyzed the prevalence and transferability of genes encoding virulence factors(asa1, esp, cylA, gelE /sprE )and antimicrobial resistance(aac(6') /aph(2'')). The production of biofilm, hemolysin and gelatinase by these isolates was also examined and the associated medical records of patients were retrospectively reviewed. Of 352 E. faecalis isolates, 315 possessed and/or genes. Of the 63 hemolysin- and 167 gelatinase-producing isolates, 59 and 94 isolates, respectively, possessed both asa1 and esp genes. E. faecalis isolates with both asa1 and esp genes formed biofilms at significantly higher rates than those with neither gene (P=0.038). The genes encoding asa1, cylA , and aac(6') /(aph(2'') were transferable and appeared to have accumulated in these isolates. The E. faecalis isolates possessing asa1 and/or esp genes were found from both catheter-related or -unrelated UTI. Our study indicates that E. faecalis isolates that have accumulated virulence genes are apt to form persistent biofilms in the urinary tracts.

Adolescent↗