Replication of Enterococcus faecalis pheromone-responding plasmid pAD1: location of the minimal replicon and oriV site and RepA involvement in initiation of replication

The hemolysin-determining plasmid pAD1 is a member of a widely disseminated family of highly conjugative elements commonly present in clinical isolates of Enterococcus faecalis. The determinants repA, repB, and repC, as well as adjacent iteron sequences, are believed to play important roles in pAD1 replication and maintenance. The repA gene encodes an initiator protein, whereas repB and repC encode proteins related to stability and copy number. The present study focuses specifically on repA and identifies a replication origin (oriV) within a central region of the repA determinant. A small segment of repA carrying oriV was able to support replication in cis of a plasmid vector otherwise unable to replicate, if an intact RepA was supplied in trans. We demonstrate that under conditions in which RepA is expressed from an artificial promoter, a segment of DNA carrying only repA is sufficient for stable replication in E. faecalis. We also show that RepA binds specifically to oriV DNA at several sites containing inverted repeat sequences (i.e., IR-1) and nonspecifically to single-stranded DNA, and related genetic analyses confirm that these sequences play an important role in replication. Finally, we reveal a relationship between the internal structure of RepA and its ability to recognize oriV. An in-frame deletion within repA resulting in loss of 105 nucleotides, including at least part of oriV, did not eliminate the ability of the altered RepA protein to initiate replication using an intact origin provided in trans. The relationship of RepA to other known initiator proteins is also discussed.     

Anti-alpha-fodrin antibodies do not add much to the diagnosis of Sjögren's syndrome

The presence of anti-alpha-fodrin autoantibodies has been reported to be a highly specific and sensitive test for the diagnosis of Sj?gren's syndrome (SjS). We looked (in Nijmegen) for anti-alpha-fodrin, anti-Ro60, and anti-La autoantibodies in a cohort of 51 patients with rheumatic diseases (primary SjS [21], secondary SjS 6, rheumatoid arthritis [RA] 12, systemic lupus erythematosus [SLE] 6, and scleroderma 6) and in 28 healthy subjects, using ELISA, immunoblotting, and immunoprecipitation. The same samples were analyzed with an alternative anti-alpha-fodrin ELISA in Hanover. The Nijmegen ELISA of the sera from primary SjS showed sensitivities of 43% and 48% for IgA- and IgG-type anti-alpha-fodrin antibodies, respectively. The Hanover ELISA showed sensitivities of 38% and 10% for IgA- and IgG-type anti-alpha-fodrin antibodies, respectively. The ELISAs for alpha-fodrin showed six (Nijmegen) and four (Hanover) anti-alpha-fodrin-positive RA sera. IgA and IgG anti-fodrin antibodies were also present in four patients with secondary SjS. The sensitivities of Ro60 and La-antibodies in the Nijmegen ELISA were 67% and 62%, respectively. Unlike anti-alpha-fodrin antibodies, all anti-Ro60 and anti-La positive sera could be confirmed by immunoblotting or RNA immunoprecipitation. Thus, anti-Ro and anti-La autoantibodies were more sensitive than anti-alpha-fodrin autoantibodies in ELISA and were more frequently confirmed by other techniques. Anti-La antibodies appear to be more disease-specific than anti-alpha-fodrin antibodies, which are also found in RA sera. Therefore, the measurement of anti-alpha-fodrin autoantibodies does not add much to the diagnosis of Sj?gren's syndrome.     

Identification of the cAD1 sex pheromone precursor in Enterococcus faecalis

The Enterococcus faecalis virulence plasmid pAD1 encodes a mating response induced by exposure to an octapeptide sex pheromone, cAD1, secreted by plasmid-free enterococci. The determinant for the pheromone in E. faecalis FA2-2, designated cad, was found to encode a 309-amino-acid lipoprotein precursor with the last 8 residues of its 22-amino acid signal sequence representing the cAD1 moiety. The lipoprotein moiety contained two 77-amino-acid repeats (70% identity) separated by 45 residues. The nonisogenic E. faecalis strain V583 determinant encodes a homologous precursor protein, but it differs at two amino acid positions, both of which are located within the pheromone peptide moiety (positions 2 and 8). Construction of a variant of strain FA2-2 containing the differences present in V583 resulted in cells that did not produce detectable cAD1. The mutant appeared normal under laboratory growth conditions, and while significantly reduced in recipient potential, when carrying pAD1 it exhibited a normal mating response. A mutant of FA2-2 with a truncated lipoprotein moiety appeared normal with respect to recipient potential and, when carrying plasmid DNA, donor potential. A gene encoding a protein designated Eep, believed to be a zinc metalloprotease, had been previously identified as required for pheromone biosynthesis and was believed to be involved in the processing of a pheromone precursor. Our new observation that the pAD1-encoded inhibitor peptide, iAD1, whose precursor is itself a signal sequence, is also dependent on Eep is consistent with the likelihood that such processing occurs at the amino terminus of the cAD1 moiety.     

Clinical and angiographic results with the ACS MULTI-LINK DUET trade mark Coronary Stent System - the DUET Study

BACKGROUND: The DUET Study is a multicenter prospective efficacy and safety evaluation of the ACS MULTI-LINK DUET coronary stainless steel balloon-expandable stent. AIMS: The primary objective was to determine the one-month incidence of MACE (major adverse cardiac events). The secondary objectives were the acute success rate, the restenosis and reocclusion rates (assessed by quantitative coronary angiography (QCA)) at six months and the occurrence of MACE in hospital and at six months. METHODS: Two hundred and ten patients were enrolled between February and June 1998 in 18 European centers. Successful stent placement was achieved in 209 patients. All patients were treated with ticlopidine 500 mg/day for one month and with aspirin >/=100 mg/day. To allow the investigators to gain familiarity with the stent system, the first one to three patients per center formed a separate lead-in population leaving an intention-to-treat population of 157 patients. The majority of the intention-to-treat population were male (79%); 28% had unstable angina, 69% had stable angina, 44% had had a previous myocardial infarction, 15% had had a previous percutaneous transluminal coronary angioplasty, and 3% had a history of stroke. The target vessel was 38.5% left anterior descending artery, 20.5% left circumflex artery and 41.0% right coronary artery. RESULTS: All but one of the intention-to-treat patients were effectively stented (17 required multiple stents). Six-month angiographic follow-up was available in 90% of the intention-to-treat population. Minimal lumen diameter (MLD) postprocedure was 2.61 +/- 0.33 mm, with a residual diameter stenosis of 16%. Six-month follow-up data showed an MLD of 1.87 +/- 0.56 mm with a residual diameter stenosis of 36%. The binary restenosis rate (>/=50% residual stenosis) was 15.6%. Up to one month following the procedure 94.9% of the population was MACE-free, with two subacute occlusions. At six months all patients were alive, of whom 82.8% were MACE-free, and 73% were free of anginal complaints. CONCLUSION: The results observed in the current DUET registry are comparable to data of other balloon-expandable-stent trials, with a low incidence of clinical events at follow-up.     

Regulation of transfer of the Enterococcus faecalis pheromone-responding plasmid pAD1: temperature-sensitive transfer mutants and identification of a new regulatory determinant, traD.

The enterococcal, conjugative, cytolysin plasmid pAD1 confers a mating response to the peptide sex pheromone cAD1 secreted by plasmid-free strains of Enterococcus faecalis. Cells carrying pAM714, a pAD1::Tn917 derivative with wild-type conjugation properties, were mutagenized with ethyl methanesulfonate to obtain variants that were induced (in the absence of pheromone) to transfer plasmid DNA upon shifting from 32 to 42 degrees C. Of 31 such mutants generated, the results of analyses of 7 are presented in detail. All seven strains were thermosensitive in the E. faecalis host FA2-2; colony morphology, clumping, and DNA transfer correlated well with each other at the two temperatures. In the nonisogenic host E. faecalis OG1X, however, only one derivative (pAM2725) exhibited correlation of all three traits at both temperatures. Three (pAM2700, pAM2703, and pAM2717) clumped and had colonies characteristic of pheromone-induced cells at 32 degrees C but transferred plasmid DNA at a higher frequency only at the elevated temperature. The other three (pAM2708, pAM2709, and pAM2712) were derepressed at both temperatures for all three characteristics. Four of the mutations, including that of pAM2725, mapped within the traA determinant, whereas two mapped identically in a previously unnoted open reading frame (designated traD) putatively encoding a short (23-amino-acid) peptide downstream of the inhibitor peptide determinant iad and in the opposite orientation. One mutant could not be located in the regions sequenced. Studies showed that the traA and traD mutations could be complemented in trans with a DNA fragment carrying the corresponding regions.     

Purification and substrate specificity of a strongly hydrophobic extracellular metalloendopeptidase ("gelatinase") from Streptococcus faecalis (strain 0G1-10)

An extracellular Zn-endopeptidase was purified to homogeneity from the culture filtrates of Streptococcus faecalis (human oral strain 0G1-10) by a procedure that comprised concentration in an Amicon Hollow Fiber System, ammonium sulfate precipitation, gel permeation chromatography, hydrophobic interaction chromatography (batch operation on phenyl-sepharose Cl-4B), followed by fast protein liquid chromatography (FPLC) on a phenyl-Superose HR 5/5 column, and finally FPLC on a Superose 12 HR 10/30 column. The enzyme is a 31.5-kDa strongly hydrophobic protein with an isoelectric point of 4.6 and a broad pH optimum of 6 to 8. The substrate specificity of the enzyme is similar to that of the mammalian membrane endopeptidase-24.11 and Streptococcus thermophilus thermolysin (EC 3.4.24.4) in hydrolyzing preferentially the Phe24-Phe25 bond in insulin B-chain, followed by cleavage of the His5-Leu6 bond. The enzyme was especially active on Azocoll and gelatin; soluble and insoluble collagens were hydrolyzed at a lower rate. S. faecalis sex pheromone-related peptides and several mammalian bioactive peptides were cleaved at sites involving pronounced hydrophobicity. The enzyme did not hydrolyze small synthetic peptide derivatives (phenylazobenzyloxycarbonyl-L-Pro-L-Leu-Gly-L-Pro-D-Arg and 2-furylacryloyl-L-Leu-Gly-L-Ala) that are typically attacked by "true" bacterial collagenases. Chemical modification indicated the importance of histidyl, carboxyl, and tyrosyl groups in enzyme activity, suggesting that this enzyme may thus be classified as a metalloprotease II (EC 3.4.24.4). The enzyme is strongly inhibited by a 720-kDa factor present in rat inflammatory exudate. The pronounced ability of the enzyme to attack collagenous materials and certain bioactive peptides suggests its participation in inflammatory processes involving the presence of S. faecalis.     

Streptococcus faecalis sex pheromone (cAM373) also produced by Staphylococcus aureus and identification of a conjugative transposon (Tn918).

Streptococcus faecalis RC73 was found to harbor a conjugative plasmid (pAM373) which confers a mating response to a sex pheromone (cAM373) excreted by plasmid-free members of the same species. The pheromone was also detected in culture filtrates of all of 23 Staphylococcus aureus strains but in only 2 of 22 coagulase negative staphylococcus strains. Streptococcus sanguis Challis and G9B also produced the activity, but 10 other Streptococcus sanguis strains did not. The activity was also produced by Streptococcus faecium 9790. A tetracycline resistance (Tc) determinant present in S. faecalis RC73 was not associated with pAM373 but served as a useful marker in efforts to identify pAM373 among other plasmids present in the strain. Analyses of the Tc determinant showed that it was located on a conjugative transposon very similar to Tn916. Designated Tn918, the transposon could insert into pAM373 as well as into two other hemolysin plasmids. Whereas pAM373 derivatives transferred very well between strains of Streptococcus faecalis, the plasmid would not establish in Staphylococcus aureus or Streptococcus sanguis. However, a derivative of pAM373 carrying Tn918 proved to be a useful delivery vehicle for generating transposon insertions into multiple sites on the staphylococcal chromosome.