First cluster of vancomycin-resistant Enterococcus faecalis isolates in Cyprus.

This report describes the first patient in Cyprus to be infected with a vancomycin-resistant enterococcus, as well as the microbiological characteristics of a cluster of vancomycin-resistant enterococcus isolates from the intensive care unit where the index case was hospitalised. All isolates were identified as Enterococcus faecalis, belonged to the same clone, and contained the vanA gene cluster. Transfer of glycopeptide resistance to a susceptible strain of E. faecalis could not be detected.

Colorectal polyp detection with virtual colonoscopy (computed tomographic colonography); the reliability of the method.

BACKGROUND/AIMS: The aim of this study was to compare the reliability of virtual colonoscopy with conventional colonoscopy in detection of colorectal polyps. METHODOLOGY: Between November 1997 and February 2000, 23 patients (14 males, 9 females) aged 43-86 years (mean: 63) with colorectal polyps who underwent colonoscopy in our endoscopy unit, were referred for virtual colonoscopy. The colon was distended with an enema tube for rectal insufflation and subsequently was scanned by helical CT (Toshiba X-vision) using the following parameters: KV 120, mAs 200, table feed 5 mm/sec, slice thickness 5 mm and reconstruction intervals 2.5 mm. Using SPARC Station 20, virtual colonoscopy was generated. RESULTS: A total of 30 polyps (19 with diameter 8-15 mm and 11 larger than 15 mm) were detected with conventional colonoscopy. Virtual colonoscopy visualized 27 polyps (17 with diameter 8-15 mm and 10 with diameter > 15 mm). CONCLUSIONS: Virtual colonoscopy is a non-invasive, well-tolerated, safe technique and can be useful for detection of colorectal polyps. Weaknesses of the method are the inability to detect small lesions and to perform biopsies.

Crystal structure of Fab198, an efficient protector of the acetylcholine receptor against myasthenogenic antibodies.

The crystal structure of the Fab fragment of the rat monoclonal antibody 198, with protective activity for the main immunogenic region of the human muscle acetylcholine receptor against the destructive action of myasthenic antibodies, has been determined and refined to 2.8 A resolution by X-ray crystallographic methods. The mouse anti-lysozyme Fab D1.3 was used as a search model in molecular replacement with the AMORE software. The complementarity determining regions (CDR)-L2, CDR-H1 and CDR-H2 belong to canonical groups. Loops CDR-L3, CDR-H2 and CDR-H3, which seem to make a major contribution to binding, were analyzed and residues of potential importance for antigen-binding are examined. The antigen-binding site was found to be a long crescent-shaped crevice. The structure should serve as a model in the rational design of very high affinity humanized mutants of Fab198, appropriate for therapeutic approaches in the model autoimmune disease myasthenia gravis.

Primary melanoma of the oesophagus treated endoscopically. A case report.

Primary melanoma is a rare neoplasm of the oesophagus, with dismal outcome in most cases. We report a case of primary melanoma of the oesophagus treated endoscopically, as coexisting illness prohibited surgical resection of the tumour. A review of the literature is made.

Multicentre surveillance of antibiotic resistance in nosocomial Staphylococcus aureus in Cyprus.

Four general hospitals in Cyprus evaluated the incidence of methicillin-resistant Staphylococcus aureus (MRSA) strains in positive cultures of staphylococci among inpatients from September 1999 to March 2000. One hundred and ninety three (193) strains were isolated from cultures of respiratory secretions, skin and mucous membrane lesions, blood and urine. Of the S. aureus strains studied, 80 (41.45%) were MRSA and 113 (58.55%) were methicillin sensitive S. aureus (MSSA). More than 78.75% of the MRSA were resistant to erythromycin and 18.75% to gentamicin. Of the MSSA, 17.69% were resistant to erythromycin and 7.08% to gentamicin. None of the MRSA and MSSA strains showed reduced sensitivity to vancomycin.

Multicentre surveillance of antibiotic resistance in nosocomial Staphylococcus aureus in Cyprus

Four general hospitals in Cyprus evaluated the incidence of methicillin-resistant Staphylococcus aureus [MRSA] strains in positive cultures of staphylococci among inpatients from September 1999 to March 2000. One hundred and ninety three [193 strains were isolated from cultures of respiratory secretions, skin and mucous membrane lesions, blood and urine. Of the S. aureus strains studied, 80 [41.45%] were MRSA and 113 [58.55%] were methicillin sensitive S. aureus [MSSA]. More than 78.75% of the MRSA were resistant to erythromycin and 18.75% to gentamicin. Of the MSSA, 17.69% were resistant to erythromycin and 7.08% to gentamicin. None of the MRSA and MSSA strains showed reduced sensitivity to vancomycin

The crystal structure of the Fab fragment of a rat monoclonal antibody against the main immunogenic region of the human muscle acetylcholine receptor.

The crystal structure of the Fab fragment of a rat monoclonal antibody, number 192, with a very high affinity (Kd = 0.05 nM) for the main immunogenic region of the human muscle acetylcholine receptor (AChR), has been determined and refined to 2.4 A resolution by X-ray crystallographic methods. The overall structure is similar to a Fab (NC6.8) from a murine antibody, used as a search model in molecular replacement. Structural comparisons with known antibody structures showed that the conformations of the hypervariable regions H1, H2, L1, L2, L3 of Fab192 adopt the canonical structures 1, 1, 2, 1, and 1, respectively. The surface of the antigen-binding site is relatively planar, as expected for an antibody against a large protein antigen, with an accessible area of 2865 A2. Analysis of the electrostatic surface potential of the antigen-binding site shows that the bottom of the cleft formed in the center of the site appears to be negatively charged. The structure will be useful in the rational design of very high affinity humanized mutants of Fab192, appropriate for therapeutic approaches of the model autoimmune disease myasthenia gravis.

A novel arginine vasopressin-neurophysin II mutation causes autosomal dominant neurohypophyseal diabetes insipidus and morphologic pituitary changes.

To determine the genetic basis of autosomal dominant neurohypophyseal diabetes insipidus (ADNDI) in a Cypriot family, we ascertained and studied a large, four-generation kindred in which all participating family members had arginine vasopressin-neurophysin II (AVP-NP-II) gene analyses done. A G to A transition was found by DNA sequence analysis at position 1773 (G1773A) of the AVP-NPII gene which is predicted to encode a substitution of tyrosine for cysteine in codon 59 (CYS59TYR). The mutation was confirmed by restriction endonuclease analysis of PCR amplification products that contain the corresponding segment of the AVP-NPII gene. To clarify the morphologic status of the pituitaries of family members, 12 affected and 3 nonaffected members had magnetic resonance imaging (MRI) studies. The bright spot of the posterior pituitary lobe was completely absent in 75% and faintly identified in 25% of the affected members who were examined with MRI. We conclude that (1) a novel G1773A transition in exon 2 of the AVP-NPII gene causes ADNDI in the large Cypriot kindred studied, (2) this mutation is predicted to encode a CYS59TYR substitution in NPII, and (3) MRI studies of the posterior pituitary lobes of affected family members show either a decreased intensity or a complete absence of the bright spot in all cases studied.

Characterisation, crystallisation and preliminary X-ray diffraction analysis of a Fab fragment of a rat monoclonal antibody with very high affinity for the human muscle acetylcholine receptor.

The Fab fragment of a rat monoclonal antibody (no. 192) with very high affinity for the main immunogenic region of the human muscle nicotinic acetylcholine receptor (AChR) has been purified, characterised and crystallised using vapour diffusion techniques. Its Kd for human AChR was determined to be 5 X 10(-11) M. Its cross-reactivity pattern suggests that residue alpha23 of the AChR strongly affects its epitope. Crystals suitable for X-ray analysis, obtained by micro- and macroseeding techniques, belong to the orthorhombic space group C222(1) and they diffract to 2.8 A resolution using synchrotron radiation. The unit cell dimensions are alpha=83.4 A, b=110.0 A and c=212.2 A and there are two Fab molecules per asymmetric unit.

N-acetyl-beta-D-glucopyranosylamine: a potent T-state inhibitor of glycogen phosphorylase. A comparison with alpha-D-glucose.

Structure-based drug design has led to the discovery of a number of glucose analogue inhibitors of glycogen phosphorylase that have an increased affinity compared to alpha-D-glucose (Ki = 1.7 mM). The best inhibitor in the class of N-acyl derivatives of beta-D-glucopyranosylamine, N-acetyl-beta-D-glucopyranosylamine (1-GlcNAc), has been characterized by kinetic, ultracentrifugation, and crystallographic studies. 1-GlcNAc acts as a competitive inhibitor for both the b (Ki = 32 microM) and the a (Ki = 35 microM) forms of the enzyme with respect to glucose 1-phosphate and in synergism with caffeine, mimicking the binding of glucose. Sedimentation velocity experiments demonstrated that 1-GlcNAc was able to induce dissociation of tetrameric phosphorylase a and stabilization of the dimeric T-state conformation. Co-crystals of the phosphorylase b-1-GlcNAc-IMP complex were grown in space group P4(3)2(1)2, with native-like unit cell dimensions, and the complex structure has been refined to give a crystallographic R factor of 18.1%, for data between 8 and 2.3 A resolution. 1-GlcNAc binds tightly at the catalytic site of T-state phosphorylase b at approximately the same position as that of alpha-D-glucose. The ligand can be accommodated in the catalytic site with very little change in the protein structure and stabilizes the T-state conformation of the 280s loop by making several favorable contacts to Asn 284 of this loop. Structural comparisons show that the T-state phosphorylase b-1-GlcNAc-IMP complex structure is overall similar to the T-state phosphorylase b-alpha-D-glucose complex structure. The structure of the 1-GlcNAc complex provides a rational for the biochemical properties of the inhibitor.

Glucose analogue inhibitors of glycogen phosphorylase: from crystallographic analysis to drug prediction using GRID force-field and GOLPE variable selection.

Several inhibitors of the large regulatory enzyme glycogen phosphorylase (GP) have been studied in crystallographic and kinetic experiments. GP catalyses the first step in the phosphorylysis of glycogen to glucose-l-phosphate, which is utilized via glycolysis to provide energy to sustain muscle contraction and in the liver is converted to glucose. alpha-D-Glucose is a weak inhibitor of glycogen phosphorylase form b (GPb, K(i) = 1.7 mM) and acts as a physiological regulator of hepatic glycogen metabolism. Glucose binds to phosphorylase at the catalytic site and results in a conformational change that stabilizes the inactive T state of the enzyme, promoting the action of protein phosphatase 1 and stimulating glycogen synthase. It has been suggested that in the liver, glucose analogues with greater affinity for glycogen phosphorylase may result in a more effective regulatory agent. Several N-acetyl glucopyranosylamine derivatives have been synthesized and tested in a series of crystallographic and kinetic binding studies with GPb. The structural results of the bound enzyme-ligand complexes have been analysed together with the resulting affinities in an effort to understand and exploit the molecular interactions that might give rise to a better inhibitor. Comparison of the N-methylacetyl glucopyranosylamine (N-methylamide, K(i) = 0.032 mM) with the analogous beta-methylamide derivative (C-methylamide, K(i) = 0.16 mM) illustrate the importance of forming good hydrogen bonds and obtaining complementarity of van der Waals interactions. These studies also have shown that the binding modes can be unpredictable but may be rationalized with the benefit of structural data and that a buried and mixed polar/non-polar catalytic site poses problems for the systematic addition of functional groups. Together with previous studies of glucose analogue inhibitors of GPb, this work forms the basis of a training set suitable for three-dimensional quantitative structure-activity relationship studies. The molecules in the training set are void of problems and potential errors arising from the alignment and bound conformations of each of the ligands since the coordinates were those determined experimentally from the X-ray crystallographic refined ligand-enzyme complexes. The computational procedure described in this work involves the use of the program GRID to describe the molecular structures and the progam GOLPE to obtain the partial least squares regression model with the highest prediction ability. The GRID/GOLPE procedure performed using 51 glucose analogue inhibitors of GPb has good overall predictivity [standard deviation of error predictions (SDEP) = 0.98 and Q(2) = 0.76] and has shown good agreement with the crystallographic and kinetic results by reliably selecting regions that are known to affect the binding affinity.

The design of potential antidiabetic drugs: experimental investigation of a number of beta-D-glucose analogue inhibitors of glycogen phosphorylase.

alpha-D-glucose is a weak inhibitor (Ki = 1.7 mM) of glycogen phosphorylase (GP) and acts as physiological regulator of hepatic glycogen metabolism; it binds to GP at the catalytic site and stabilizes the inactive T state of the enzyme promoting the action of protein phosphatase 1 and stimulating glycogen synthase. The three-dimensional structures of T state rabbit muscle GPb and the GPb-alpha-D-glucose complex have been exploited in the design of better regulators of GP that could shift the balance between glycogen synthesis and glycogen degradation in favour of the former. Close examination of the catalytic site with alpha-D-glucose bound shows that there is an empty pocket adjacent to the beta-1-C position. beta-D-glucose is a poorer inhibitor (Ki = 7.4 mM) than alpha-D-glucose, but mutarotation has prevented the binding of beta-D-glucose in T state GP crystals. A series of beta-D-glucose analogues has been designed and tested in kinetic and crystallographic experiments. Several compounds have been discovered that have an increased affinity for GP than the parent compound.

Design of inhibitors of glycogen phosphorylase: a study of alpha- and beta-C-glucosides and 1-thio-beta-D-glucose compounds.

alpha-D-Glucose is a weak inhibitor of glycogen phosphorylase b (Ki = 1.7 mM) and acts as a physiological regulator of hepatic glycogen metabolism. Glucose binds to phosphorylase at the catalytic site and results in a conformational change that stabilizes the inactive T state of the enzyme, promoting the action of protein phosphatase 1 and stimulating glycogen synthase. It has been suggested that, in the liver, glucose analogues with greater affinity for glycogen phosphorylase may result in a more effective regulatory agent. Several alpha- and beta-anhydroglucoheptonic acid derivatives and 1-deoxy-1-thio-beta-D-glucose analogues have been synthesized and tested in a series of crystallographic and kinetic binding studies with glycogen phosphorylase. The structural results of the bound enzyme-ligand complexes have been analyzed, together with the resulting affinities, in an effort to understand and exploit the molecular interactions that might give rise to a better inhibitor. This work has shown the following: (i) Similar affinities may be obtained through different sets of interactions. Specifically, in the case of the alpha- and beta-glucose-C-amides, similar Ki's (0.37 and 0.44 mM, respectively) are obtained with the alpha-anomer through interactions from the ligand via water molecules to the protein and with the beta-anomer through direct interaction from the ligand to the protein. Thus, hydrogen bonds through water can contribute binding energy similar to that of hydrogen bonds directly to the protein. (ii) Attempts to improve the inhibition by additional groups did not always lead to the expected result. The addition of nonpolar groups to the alpha-carboxamide resulted in a change in conformation of the pyranose ring from a chair to a skew boat and the consequent loss of favorable hydrogen bonds and increase in the Ki. (iii) The addition of polar groups to the alpha-carboxamide led to compounds with the chair conformation, and in the examples studied, it appears that hydration by a water molecule may provide sufficient stabilization to retain the chair conformation. (iv) The best inhibitor was N-methyl-beta-glucose-C-carboxamide (Ki = 0.16 mM), which showed a 46-fold improvement in Ki from the parent beta-D-glucose. The decrease in Ki may be accounted for by a single hydrogen bond from the amide nitrogen to a main-chain carbonyl oxygen, an increase in entropy through displacement of a water molecule, and favorable van der Waals contacts between the methyl substituent and nonpolar protein residues.(ABSTRACT TRUNCATED AT 250 WORDS)