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PubMed2004

Inhibition of vancomycin-resistant enterococcus by continuous-flow cultures of human stool microflora with and without anaerobic gas supplementation.

A continuous-flow competitive exclusion (CFCE) culture model of human stool microflora was used to examine whether supplemental anaerobic gas is necessary for maintenance of anaerobes and inhibition of vancomycin-resistant Enterococcus (VRE). CFCE cultures of human stool microflora were maintained with supplemental nitrogen, without supplemental nitrogen, or with percolated room air. Cultures with or without supplemental nitrogen maintained >9 log(10) CFU mL(-1) of obligate anaerobes and eliminated 10(6) CFU mL(-1) of VRE. When room air was percolated into the culture, anaerobes were detected at < or =2 log(10) CFU mL(-1), and the same VRE inoculum was not eliminated ( P < 0.001). These data demonstrate that human stool CFCE cultures maintain high levels of obligate anaerobes and inhibit VRE without the addition of supplemental anaerobic gas.

Aerobiosis↗
PubMed2005

Atypical genetic locus associated with the zwf gene encoding the glucose 6-phosphate dehydrogenase from Enterococcus mundtii CRL35.

The zwf gene encoding glucose 6-phosphate dehydrogenase (G6PD, EC.1.1.1.49) from Enterococcus mundtii CRL35 was cloned as a 4921 bp EcoRI fragment and analyzed. The predicted zwf gene product consists of 506 residues with a molecular mass of 58.4 kDa, and is fully active in Escherichia coli as demonstrated by its heterologous expression in the zwf-negative mutant E. coli Su294. It shows a high degree of sequence identity (40-60%) to G6PDs described in other bacteria. Upstream of the zwf gene, a homolog of the DtxR family was identified (ORF D). Analysis of the 5' sequence of ORF D revealed a potential promoter sequence, which would suggest the presence of an operon-like structure between ORF D and the zwf gene. Finally, it was found that Fe2+ levels have an important role as a modulator of G6PD activity. This is the first report of this type of regulation of G6PD activity. A possible involvement in oxidative stress is discussed.

Enterococcus↗
PubMed2006

Adhesion of vancomycin-resistant enterococcus to human intestinal mucus.

The intestinal mucus layer provides a potential niche for colonization by vancomycin-resistant Enterococcus faecium (VREF). We therefore examined the ability of six VREF strains to adhere to human intestinal mucus and determined binding kinetics. Four of six (67%) VREF strains demonstrated significant adhesion to immobilized intestinal mucus compared with a Salmonella typhimurium-negative control strain, but the level of adherence was low compared with Lactobacillus rhamnosus GG. Binding kinetics studies demonstrated that the maximum number of these four VREF strains that could adhere to a unit surface area of immobilized mucus was similar to or higher than the maximum number of L. rhamnosus GG that could adhere; however, L. rhamnosus GG demonstrated 20- to 130-times higher affinity than the VREF strains. These results demonstrate that VREF strains may adhere to human intestinal mucus and suggest that L. rhamnosus GG might be able to displace VREF strains.

Bacterial Adhesion↗
PubMed2005

Anti-Listeria monocytogenes bacteriocin-like inhibitory substances from Enterococcus faecium UQ31 isolated from artisan Mexican-style cheese.

Artisan fresh Mexican-style cheeses are commonly made from raw milk that provides not only rich flavors, but also a diversity of associated lactic acid bacteria (LAB) strains. Enterococcus faecium UQ31 was isolated from panela cheese and produced bacteriocin-like inhibitory substances (BLIS) with a strong anti-Listeria activity. A modified pH-mediated adsorption-desorption purification process resulted in (after SDS-PAGE) two bands showing antimicrobial activities, where most of the activity corresponded to the band with an estimated molecular weight of 7.5 kDa. The BLIS produced by E. faecium UQ31 were heat resistant, stable at ambient storage conditions, and active in the pH range 5--9. The BLIS antimicrobial activities were detected during logarithmic growth phase and remained constant until the end of incubation time (19 h). These BLIS showed a wide anti-Listeria monocytogenes spectra. The E. faecium UQ31 strain or their BLIS represent a promising potential as antimicrobial food preservatives.

Animals↗
PubMed2000

pS86, a new theta-replicating plasmid from Enterococcus faecalis.

The complete nucleotide sequence of the small (5149 bp) and cryptic plasmid pS86 from Enterococcus faecalis ssp. faecalis S-86 has been determined. Sequence analysis revealed six putative open reading frames (ORFs) encoding polypeptides of 28.3, 11.5, 8.4, 65.1, 7.3, and 11.96 kDa each. Based on sequence similarity, two cassettes have been identified in pS86: ORF1 codes for the replication initiation protein (Rep); ORF4 codes for a putative mobilization protein that shows similarities to Mob/Pre proteins from plasmids of Gram-positive bacteria. No function could be assigned to the other putative ORFs found. According to our results, pS86 plasmid could use a theta-mode of replication, similar to the recently described theta-type replicons from pUCL287 (Tetragenococcus halophila) and pLA1 or pLA105 (Lactobacillus acidophilus) plasmids.

Bacterial Proteins↗
PubMed2000

The rpoN gene of Enterococcus faecalis directs sensitivity to subclass IIa bacteriocins.

The final sigma 54 factor has been previously described to be involved in Listeria monocytogenes sensitivity to mesentericin Y105, a subclass IIa bacteriocin. Here, we identified the rpoN gene, encoding final sigma 54, of Enterococcus faecalis JH2-2 and showed that its interruption leads to E. faecalis resistance to different subclass IIa bacteriocins. Moreover, this rpoN mutant remained sensitive to nisin, a class I bacteriocin, suggesting that final sigma 54 is especially involved in sensitivity to subclass IIa bacteriocins.

Bacteriocins↗
PubMed2001

Expression of the major heat shock proteins DnaK and GroEL in Streptococcus pyogenes: a comparison to Enterococcus faecalis and Staphylococcus aureus.

One of the outstanding problems in the field of heat shock response has been to elucidate the mechanism underlying the induction of heat shock proteins (HSPs). In this work, we initiate an analysis of the expression of heat shock groEL and dnaK genes and their promoters in S. pyogenes. The synthesis of total cellular proteins was studied upon transfer of a log-phase culture from 37 degrees C to 42 degrees C by performing 5-min pulse-labeling experiments with (35)S-Met. The heat shock responses in the pathogenic Gram-positive cocci, Enterococcus faecalis and Staphylococcus aureus, were also analyzed.

Bacterial Proteins↗
PubMed1996

Starvation-induced multiresistance in Enterococcus faecalis JH2-2.

Compared with growing bacteria, carbohydrate-starved cells of Enterococcus faecalis show development of a multiresistance state against heat, H2O2, acid, and ethanol, but not against UV irradiation. The kinetics of acquisition of resistance is different according to the stress. Three hours of starvation provide maximal resistance against ethanol, while the tolerance to heat, H2O2, and acid increases progressively with the duration of starvation. Chloramphenicol treatment does not abolish the ethanol tolerance. Protein synthesis inhibition during the transitional growth phase and the first hours of starvation partially inhibit the acquisition of heat and oxidative resistances. Antibiotic treatment after 3 h of starvation does not affect the increase of these resistances. We suggest that synthesis of specific proteins revealed by 2-D gel analysis in the first 3 h of starvation, followed by a second mechanism related to protein degradation or alteration, is necessary for acquisition of maximal resistance towards heat and oxidative stresses.

Bacterial Proteins↗
PubMed1998

Relationship of K+-uptaking system with H+-translocating ATPase in Enterococcus hirae, grown at a high or low alkaline pH.

Potassium ion pool was studied in glycolyzing Enterococcus hirae, grown at high or low alkaline pH (pH 9.5 and 8.0, respectively). Energy-dependent increase of K+ pool was lower for the wild-type cells, grown at pH 9.5, than that for the cells grown at pH 8.0. It was inhibited by N,N'-dicyclohexylcarbodiimide (DCCD). The stoichiometry of DCCD-inhibited K+ influx to DCCD-inhibited H+ efflux for the wild-type cells, grown at pH 9.5 or 8.0, was fixed for different K+ external activity. DCCD-inhibited ATPase activity of membrane vesicles was significantly stimulated by K+ for the wild-type cells grown at pH 9.5, and required K+ for the wild-type cells grown at pH 8.0, while the levels of alpha and beta subunits of the F1 and b subunit of the F0 were lower for the cells grown at pH 9.5 than that for the cells grown at pH 8.0. Such an ATPase activity was residual in membrane vesicles from the atpD mutant with a nonfunctional F0F1. ATPase activity of membrane vesicles from the mutant with defect in Na+-ATPase was higher for the cells grown at pH 9.5 than that for the cells grown at pH 8.0, and was inhibited by DCCD. An energy-dependent increase of K+ pool in this bacterium, grown at a high or low alkaline pH, is assumed to occur through a K+ uptaking system, most probably the Trk. The latter functions in a closed relationship with the H+-translocating ATPase F0F1.

Enterococcus↗
PubMed1999

Biochemical and genetic evidence of enterocin P production by two Enterococcus faecium-like strains isolated from fermented sausages.

Two bacteriocin-producing Enterococcus faecium-like strains were independently isolated from fermented sausages. Bacteriocins were purified to homogeneity by ammonium sulfate precipitation, gel filtration, cationic exchange, hydrophobic interaction, and reverse-phase liquid chromatography. Two peptide inhibitory fractions were purified from each strain, denominated A and B for E. faecium AA13, and C and D for E. faecium G16. Fraction B was blocked for amino acid sequencing by Edman degradation, while the amino acid sequences obtained from peptides A, C, and D contained the YGNGV consensus motif in positions 5 to 9, and the ATRS sequence in positions 1 to 4. By use of PCR techniques and nucleotide sequencing, the structural gene of enterocin P was found both in E. faecium AA13 and E. faecium G16. Metabolic and genetic features of the two strains suggest that they are slightly different, they may produce more than one bacteriocin, and both produce enterocin P.

Amino Acid Sequence↗
PubMed2001

Enterococcus spp. produces slime and survives in rat peritoneal macrophages.

Enterococcal clinical isolates were investigated for the ability to form biofilm on inert surfaces, as a measure of slime production, in an attempt to find new possible virulence factors for these microorganisms. This property was commonly found among Enterococcus faecalis. Also E. faecium isolates were able to form biofilm, although to a lesser extent; for this species, however, biofilm formation seemed more frequently associated with isolates from infection rather than with environmental strains or isolates from healthy individuals. Biofilm formation was strongly affected by the presence of an additional carbohydrate source in the medium, or by iron deprivation, indicating a role of slime for survival in stressful conditions. Slime-producing E. faecalis were able to survive inside peritoneal macrophages for extended periods compared to slime-negative strains or to slime-positive bacteria grown in conditions depressing slime production. In particular, slime-producing and slime-negative cells showed a decrease of 1 and 2 log units, respectively, at 1 h after infection; slime-negative cells were then rapidly killed, with clearance of bacterial cells at 24 h. Slime-producing bacteria persisted up to 48 h, which was the last time point examined, as after that time viability of both infected and non-infected macrophages started to decline. Scanning electron microscopy observations showed the presence of abundant amorphous extracellular material, of possible polysaccharide nature, embedding bacterial cells to form a multilayered biofilm. Even in conditions not supporting biofilm formation, bacterial cells appeared capsulated, suggesting that capsule and slime might represent different structures. Genes belonging to the epa locus or to a putative icaA homolog did not seem to be involved in synthesis and export of slime.

Animals↗
PubMed2002

Invasion of HeLa cells by Enterococcus faecalis clinical isolates.

We examined the in vitro ability of Enterococcus faecalis clinical isolates to adhere to and to invade HeLa cells, suggested to be a valuable model system to study bacteria-directed endocytosis. Using a variety of compounds that act on eukaryotic cell structures, both microtubules and microfilaments were found to be involved in enterococcal entry into cells. Two distinct modes of interaction were observed: in one, a close proximity of bacteria with the cell membrane was observed, possibly leading to direct engulfment of the bacterial cell. In the other mode, cellular pseudopodal formation seemed to be stimulated by vicinity of bacterial cells; in some cases, such associations involved formation of clathrin-coated-like vesicles before internalizing enterococci. The above-mentioned experimental data together with the use of monodansylcadaverine, amiloride and NH4Cl, all involved in cytosol acidification and inhibition of receptor-mediated endocytosis (RME), led us to conclude that E. faecalis is internalized within HeLa cells by more than one invasion pathway. One, sensitive to amiloride, is most likely a macropinocytic, actin-dependent uptake mechanism, which determines the production of large smooth-membrane vacuoles engulfing enterococci. The other is RME, in which entry is dependent on both microfilament and microtubule structural integrity.

Acids↗
PubMed2003

Cytolysin gene expression in Enterococcus faecalis is regulated in response to aerobiosis conditions.

Here we investigate the expression of cylL(L)and cylL(S), the genes that encode the structural subunits of the cytolysin/haemolysin of Enterococcus faecalis, in response to aerobiosis conditions. Haemolysis assays of E. faecalis strains cultured under aerobic and anaerobic conditions revealed three different haemolytic phenotypes, one of which exhibited greater haemolysis under anaerobic conditions than under aerobic conditions, and was shown to be associated with the presence of the cyl genes. Reporter gene studies revealed that cylL(L) L(S) promoter activity was significantly greater (up to 8.6-fold) under anaerobic compared to aerobic conditions throughout batch growth, demonstrating that these genes are regulated in response to the degree of aerobiosis. Band shift assays confirmed the binding of a protein factor to the region between 202 and 37 bp upstream of the cylL(L)start codon, and a higher level of binding was observed with anaerobically derived cell-free extracts than with extracts of aerobically grown cells. This is the first report of an oxygen-regulated virulence factor in E. faecalis (that is distinct from the quorum-sensing regulatory system reported previously), and may be of in vivo relevance for the bacterium in biofilms and other environments characterised by oxygen gradients.

Aerobiosis↗
PubMed2005

Prevention of febrile neutropenia in cancer patients by probiotic strain Enterococcus faecium M-74. Phase II study.

Febrile neutropenia (FN) remains a potentially life-threatening complication of anticancer chemotherapy. Bacterial translocation via intestinal mucosa is a significant mechanism of FN development. Competitive inhibition of bowel colonization by pathogenic microorganisms by lactic acid bacteria could be a useful prevention of FN. The aim of the study was the prevention of FN by probiotic strain Enterococcus faecium M-74 enriched with selenium in leukemic patients. Fourteen (six males/eight females) patients with myelogenous leukemia treated by induction or consolidation chemotherapy were included in the study. Patients received prophylaxis with E. faecium M-74 during one cycle of chemotherapy. The daily dose was 36 x 10(9) CFU tid. Prophylaxis started between day -2 and day +2 of chemotherapy and continued until the absolute neutrophile count (ANC) was >1,000/microl. All patients experienced febrile neutropenia. During 231 days of severe neutropenia, 30 febrile episodes occurred. No any febrile episode or infection provoked by the strain tested was noticed. Tolerance of therapy was excellent without significant adverse effects. Our results demonstrate the safety of the probiotic strain E. faecium M-74 enriched with selenium in leukemic patients with severe neutropenia. However, its administration was not effective in the prevention of febrile neutropenia, but this does not preclude the protective effect of other probiotic strains.

Adult↗
PubMed2004

Interaction kinetics of the copper-responsive CopY repressor with the cop promoter of Enterococcus hirae.

In Enterococcus hirae, copper homeostasis is controlled by the cop operon, which encodes the copper-responsive repressor CopY, the copper chaperone CopZ, and two copper ATPases, CopA and CopB. The four genes are under control of CopY, which is a homodimeric zinc protein, [Zn(II)CopY]2. It acts as a copper-responsive repressor: when media copper is raised, CopY is released from the DNA, allowing transcription to proceed. This involves the conversion of [Zn(II)CopY]2 to [Cu(I)2CopY]2, which is no longer able to bind to the promoter. Binding analysis of [Zn(II)CopY]2 to orthologous promoters and to control DNA by surface plasmon resonance analysis defined the consensus sequence TACAnnTGTA as the repressor binding element, or " cop box", of Gram-positive bacteria. Association and dissociation rates for the CopY-DNA interaction in the absence and presence of added copper were determined. The dissociation rate of [Zn(II)CopY]2 from the promoter was 7.3 x 10(-6) s(-1) and was increased to 5 x 10(-5) s(-1) in the presence of copper. This copper-induced change may be the underlying mechanism of copper induction. Induction of the cop operon was also assessed in vivo with a biosensor containing a lux reporter system under the control of the E. hirae cop promoter. Half-maximal induction of this biosensor was observed at 5 microM media copper, which delineates the ambient copper concentration to which the cop operon responds in vivo.

Bacterial Proteins↗
PubMed2004

Are there patients with peritonitis who require empiric therapy for enterococcus?

Enterococci are an increasingly important cause of nosocomial infections. While the clinical impact of enterococci in cases of bacteremia and super-infections in selected patient populations has been well-established, their role as primary pathogens in polymicrobial intra-abdominal infections remains controversial. While it has been suggested that the presence of enterococci increases the rate of infectious post-operative complication, it has also been demonstrated that polymicrobial intra-abdominal infections involving enterococci can be treated successfully with appropriate surgical drainage and antibiotics, such as cephalosporins, that are not active against enterococci. Therefore, the question arises of whether or not antibiotic coverage against enterococci should be included in the empirical treatment of peritonitis in certain high-risk patient populations. An extensive literature review revealed some evidence arguing in favour of using empirical therapy with enterococcal coverage for intra-abdominal infections in the following cases: (i) immunocompromised patients with nosocomial, post-operative peritonitis; (ii) patients with severe sepsis of abdominal origin who have previously received cephalosporins and other broad-spectrum antibiotics selecting for Enterococcus spp.; (iii) patients with peritonitis and valvular heart disease or prosthetic intravascular material, which place them at high risk of endocarditis. The ideal therapeutic regimen for these high-risk patients remains to be determined, but empirical therapy directed against enterococci should be considered.

Anti-Bacterial Agents↗
PubMed2005

Spread of ampicillin/vancomycin-resistant Enterococcus faecium of the epidemic-virulent clonal complex-17 carrying the genes esp and hyl in German hospitals.

The incidence of vancomycin-resistant Enterococcus faecium isolation was low (<or=5%) in German hospitals before 2003. Within the second half of 2003 and the first half of 2004, however, increasing frequencies of up to 14% were noticed in several hospitals in southwestern Germany. This increase was attributed mainly to the occurrence and spread of epidemic-virulent ampicillin/vancomycin-resistant, vanA- and vanB-positive E. faecium clones, most of which exhibited the virulence factors enterococcal surface protein (esp) and bacteriocin activity and some which exhibited hyaluronidase (hyl). E. faecium possessing hyaluronidase was initially found in U.S. hospitals and recently detected in several European hospitals and, subsequently, in German hospitals as well. Ampicillin/vancomycin-resistant E. faecium clones originating mainly from southwestern German hospitals were characterized by multilocus sequence typing since different sequence types (STs) belonging to the clonal complex-17 are currently disseminated worldwide. Multilocus sequence typing revealed that, in 1998 and 1999, ampicillin/vancomycin-resistant E. faecium clone ST-117 was prevalent in various German hospitals, while in 2003 and 2004, clone ST-203 dominated in several hospitals located in southwestern Germany. Both sequence types display single-locus variants of ST-78, which was frequently recorded in various Italian hospitals between 2000 and 2003, and all of these STs belong to the clonal complex-17. Expression of linezolid resistance was observed in ampicillin/glycopeptide-resistant E. faecium strains (VanA type) from two tertiary hospitals in southwestern Germany due to mutations in domain V of the 23S rDNA (G2576T). While in one hospital the resistance emerged during linezolid therapy, in the other hospital resistance was caused by transfer of an identical linezolid/ampicillin/glycopeptide-resistant E. faecium strain. In conclusion, it is very important to monitor the occurrence of epidemic-virulent clonal complex-17 strains of E. faecium to prevent their spread in hospitals, especially if they are resistant to glycopeptides and linezolid.

Acetamides↗