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Biomedical subjects

A J Fox

Publications and source records attributed to A J Fox.

At least 91 records · Page 5Linked to original sources
PubMed1998

Epidemiological characterization of methicillin-resistant Staphylococcus aureus isolated in the North West of England by protein A (spa) and coagulase (coa) gene polymorphisms.

In a comparative study, isolates of methicillin-resistant Staphylococcus aureus (MRSA) with known pulsed-field gel electrophoresis (PFGE) and bacteriophage type were analysed by polymerase chain reaction (PCR) and restriction fragment length polymorphisms (RFLP) for additional discriminatory subtyping information. PFGE was previously performed using standardized, commercially available kits and pre-programmed software. Isolates were examined for coagulase (coa) and protein A (spa) gene polymorphisms following PCR amplification of the coa hypervariable and spa repeat regions. Coa gene RFLPs produced a total of 38 distinct combined patterns after digestion with HaeIII and AluI and identified the predominant epidemic (EMRSA) types 15 and 16. A unique HaeIII restriction site was identified by RFLP and sequence analysis in the coa gene for EMRSA 15 but not EMRSA 16. The spa gene PCR yielded a total of 14 different profiles ranging from 3-18 repeats with the 2 predominant EMRSA types falling into 2 distinct groups. PCR detection of coa and spa polymorphisms offer a rapid preliminary strain identification and discriminatory subtyping information for surveillance of MRSA.

Bacteriophage Typing↗
PubMed1998

Amplification of the meningococcal porB gene for non-culture serotype characterization.

Since 1992, the proportion of culture-confirmed meningococcal infections compared with numbers of notified cases of meningococcal disease has decreased in England and Wales. As most meningococcal strain characterization methods depend on a clinical isolate, this has resulted in a loss of epidemiological information. To address this problem, and to aid nonculture diagnosis, a semi-nested PCR protocol for the amplification of the meningococcal porB gene from clinical specimens was developed. This gene encodes the meningococcal serotyping antigen; strain typing data was provided by hybridization of allele-specific oligonucleotide probes to the digoxigenin-labelled porB amplicon in a 'PCR ELISA'. This assay was specific for meningococcal DNA and sensitivities of 0.81 for cerebrospinal fluid (CSF), 0.57 for serum, and 0.62 for whole blood taken from patients with proven meningococcal infection were obtained.

Bacterial Outer Membrane Proteins↗
PubMed1998

Molecular variation of meningococcal serotype 4 antigen genes.

Changes in the frequency of serogroup B non serotypable (B:NT) meningococci isolated in England and Wales were investigated by T-track fingerprint analysis, DNA nucleotide sequence determination, and serotyping by whole cell ELISA and dot blot assay. Seventy-three per cent of the isolates designated as B:NT by the Meningococcal Reference Unit (MRU) dot blot assay during 1993-4, expressed variants of the serotyping antigen, PorB, that were serotype 4 by whole cell ELISA. T-track fingerprint patterns of these and other 'serotype 4' isolates revealed five distinct porB alleles which were shown by nucleotide sequence determination to encode different peptide sequences. Differential binding of the 'serotype 4' mAbs MN14G21 and 5DC4C8G8 in whole cell ELISA and dot blot assays was the result, (i) of differences in the peptide sequence of predicted surface loop I and (ii) an amino acid deletion in predicted loop VI of the PorB protein.

Amino Acid Sequence↗
PubMed1998

Characterisation of 16 Campylobacter jejuni and C. coli typing bacteriophages.

Taxonomic classification of bacteriophages specific for Campylobacter jejuni and C. coli has not been reported previously. A set of 16 virulent phages, distinguishable by their lytic spectra, has been used extensively for epidemiological typing of C. jejuni and C. coli at Preston Public Health Laboratory. These phages were investigated by electron microscopy, pulsed-field gel electrophoresis and restriction endonuclease analysis. All phages had icosahedral heads and long contractile tails. Accordingly, they were classified as members of the Myoviridae family. These phages could be subdivided into three groups according to genome size and head diameter: group I, two phages with head diameters of 140.6 and 143.8 nm and genome sizes of 320 kb; group II, five phages with average head diameters of 99 nm and average genome sizes of 184 kb; and group III, nine phages with average head sizes of 100 nm and average genome sizes of 138 kb. Phages NCTC12676 and NCTC12677 of group I had unusually large genomes of c. 320 kb which are two of the largest phage genomes to be described. Restriction endonuclease analysis demonstrated that DNA from the 16 phages was refractory to digestion by a number of restriction enzymes.

Bacteriophage Typing↗
PubMed1998

Heterogeneity of the PorB protein in serotype 22 Neisseria meningitidis.

The genetic diversity of porB genes from meningococcal isolates characterized as serotype 22 was investigated by gene sequencing. This procedure identified seven distinct porB sequences, demonstrating variation in the PorB protein recognized by the serotype 22 monoclonal antibody. This is consistent with the genetic heterogeneity of serotype 22 meningococci reported previously.

Amino Acid Sequence↗
PubMed1998

Associations between heat-stable (O) and heat-labile (HL) serogroup antigens of Campylobacter jejuni: evidence for interstrain relationships within three O/HL serovars.

A comparative examination of the heat-stable (O) and heat-labile (HL) serogrouping results for 9,024 sporadic human isolates of Campylobacter jejuni revealed conserved associations between specific O and HL antigens (O/HL serovars). Forty-nine percent of the isolates which grouped for both O and HL antigens belonged to one of three serovars: O 4 complex/HL 1 (17.9%), O 1/HL 2 (16.8%), or O 50/HL 7 (14.5%). Other common serovars were O 2/HL 4 (8.3%), O 6/HL 6 (8.1%), O 53/HL 11 (4.5%), O 19/HL 17 (3.3%), O 5/HL 9 (3.3%), O 9/HL 9 (3.2%), and O 23/HL 5 (3.1%). These 10 serovars accounted for 83.1% of the serogroupable isolates. A large number of strains (41.3%) could be typed by only one of the two methods or could not be serogrouped (11%). Strains belonging to three serovars, O 2/HL 4, O 50/HL 7, and O 23/HL 5, were further characterized by combining data from expressed features (O/HL serogroups, phage groups, and biotypes) with restriction fragment length polymorphism genotypes. These polyphasic data demonstrated that within each serovar, individual isolates showed substantial conservation of both genomic and phenotypic characteristics. The essentially clonal nature of the three serovars confirmed the potential of combined O and HL serogrouping as a practical and phylogenetically valid method for investigating the epidemiology of sporadic C. jejuni infection.

Animals↗
PubMed1998

PCR-ELISA for the early diagnosis of invasive pulmonary aspergillus infection in neutropenic patients.

AIM: To evaluate a newly developed aspergillus mitochondrial gene PCR-ELISA assay for the early diagnosis of invasive pulmonary aspergillosis (IPA) in neutropenic patients. METHODS: The aspergillus mitochondrial gene was chosen for the amplification target for use with a solution hybridisation assay with colorimetric end stage detection in microtitre plate format (PCR-ELISA). The study group comprised neutropenic patients undergoing febrile episodes not responding to standard antibacterial antibiotics. Patients underwent computed tomography and bronchoscopy. Bronchoalveolar lavage (BAL) fluids were examined by culture and PCR. RESULTS: The aspergillus mitochondrial gene PCR-ELISA was both sensitive (100%) and specific (100%) for IPA in neutropenic patients. All 12 patients with definite or probable IPA had PCR positive BAL fluids. None of the patients with undiagnosed or confirmed infections of other aetiologies were mitochondrial PCR positive. Speciation based upon amplicon size difference was possible. CONCLUSIONS: Aspergillus mitochondrial DNA PCR-ELISA on BAL fluid is useful in the early diagnosis of IPA in neutropenic patients alone or, potentially, as an indication for thoracic computed tomography.

Adolescent↗
PubMed1998

Molecular characterisation of methicillin resistant Staphylococcus aureus.

Finer discrimination between strains of methicillin resistant Staphylococcus aureus (MRSA) than phage typing can provide is needed to identify and characterise spread of infection in outbreaks. This study compares three molecular methods with each other and with phage typing. Pulsed field gel electrophoresis provides the greatest discrimination, but finer discrimination is obtainable by combining methods.

Bacterial Typing Techniques↗
PubMed1998

Thromboembolic events associated with the treatment of cerebral aneurysms with Guglielmi detachable coils.

BACKGROUND AND PURPOSE: The purpose of this study was to document the prevalence, radiologic appearance, and treatment of thromboembolic events related to GDC embolization of cerebral aneurysms. METHODS: The clinical and radiologic records of all patients undergoing GDC treatment of intracranial aneurysms at our institution were reviewed. All cases in which unexpected complications occurred were selected. Those complications related to presumed thromboembolic events were analyzed. RESULTS: Of 59 patients (60 aneurysms) treated with GDCs, 17 (28%) experienced thromboembolic events. Seven patients had transient ischemic attacks and 10 had strokes. In 10 patients, the deficits occurred during or immediately after the procedure; in the rest, the complications were delayed. In six patients, all radiologic investigations were negative for infarction and in seven patients, CT scans showed new ischemic lesions. In four patients, MR imaging alone showed infarcts, and in four of nine patients who underwent subsequent angiography, acute ischemic findings were demonstrated. Eight patients were treated with volume expansion, eight with full heparinization, and one patient underwent intraarterial thrombolysis. Clinical outcome was excellent or good in 14 of 17 patients, with only three patients (5%) incurring permanent neurologic deficits. CONCLUSION: Thromboembolic events related to GDC treatment may be more common than has been reported in the literature. In our experience, this rate was 28%, with persisting deficits in 5%. These events can occur after uncomplicated procedures and may be unaccompanied by radiologic findings. Clinical outcome is usually favorable.

Adult↗
PubMed1997

Synchronized overproduction of AMPA, kainate, and NMDA glutamate receptors during human spinal cord development.

Quantitative receptor autoradiography was used to map the distribution in the developing human spinal cord of the three types of ionotropic glutamate receptors. N-methyl-D-Aspartate (NMDA) receptors were labeled with [3H]glutamate, kainic acid (KA) receptors were labeled with [3H]KA, and alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionate (AMPA) receptors were labeled with [3H]AMPA. In the adult, labeling of all three receptor subtypes is largely restricted to the substantia gelatinosa (SG) in the dorsal horn, with very low level labeling elsewhere in the spinal gray matter. In marked distinction, in late fetal life, high level ligand binding is seen throughout the spinal gray matter. In early postnatal life, binding sites diminish in all regions, but least so in the SG, until the adult pattern emerges. Thus a coordinated transient high level of ionotropic glutamate receptor expression occurs within the developing spinal cord. Saturation analysis of ligand binding shows that the affinity of [3H]KA and [3H]AMPA binding is not developmentally regulated. In contrast, the affinity of [3H]glutamate binding to the NMDA receptor in the fetal ventral horn is three-fold greater than in the adult ventral horn. Thus, in addition to quantitative changes in glutamate receptor expression, qualitative changes occur in the expression of NMDA receptors during development. The distinct glutamate receptor phenotype of fetal and early postnatal spinal cord cells suggests that alterations in the excitable properties of these cells plays an important role in activity-dependent development and in susceptibility to excitotoxic injury.

Adolescent↗
PubMed1997

Activation of large conductance potassium channels inhibits the afferent and efferent function of airway sensory nerves in the guinea pig.

Sensory nerves play an important role in airway disease by mediating central reflexes such as cough, and local axon reflexes resulting in the peripheral release of neuropeptides. We have tested whether the benzimidazolone compound, NS1619, an opener of large conductance calcium-activated potassium (BK Ca) channels, inhibits the activity of sensory fibers, and central and local airway reflexes in guinea pig airways. In in vitro single fiber recording experiments, NS1619 applied to identified receptive fields in the trachea inhibited the firing of A(delta)-fibers evoked by hypertonic saline and distilled water, and bradykinin-evoked firing of C-fibers. Electrically evoked nonadrenergic noncholinergic contractions of isolated bronchi mediated by the release of neurokinin A (NKA) from C-fibers, but not those elicited by exogenous NKA, were inhibited by NS1619. These effects of NS1619 were prevented by iberiotoxin, a selective blocker of BK Ca channels. In conscious guinea pigs, cough evoked by aerosolized citric acid was also inhibited by NS1619. These data show that BK Ca channel activation inhibits sensory nerve activity, resulting in a reduction of both afferent and efferent function. BK Ca channel openers may therefore be of potential benefit in reducing neurogenic inflammation and central reflexes seen during inflammatory conditions of the airways, and may represent a new class of antitussive drug.

Afferent Pathways↗
PubMed1997

Intracranial dural arteriovenous fistulae with pial venous drainage: combined endovascular-neurosurgical therapy.

BACKGROUND: Intracranial dural arteriovenous fistula with pial venous drainage may present with hemorrhage or focal neurologic deficit and may be difficult to treat. We wish to summarize the therapeutic approaches to these potentially dangerous lesions and to demonstrate how endovascular and neurosurgical therapies may have complimentary roles in their management. METHODS: The clinical and radiological records of all patients who presented to our institution with intracranial dural arteriovenous fistula over the last 5 years were reviewed. In those cases demonstrating pial venous drainage, details of presentation, imaging features, endovascular and surgical therapy and outcome were analyzed. RESULTS: We identified 13 patients with these lesions, 7 of whom presented with intracranial hemorrhage. Six patients were treated with embolization alone. Angiographic cure was achieved in 4. There was one complication in this group, a subarachnoid hemorrhage following glue injection. Four patients were treated with embolization followed by surgical occlusion of the pial venous drainage. Angiographic cure was achieved in all 4. There was one complication in this group, a facial nerve palsy following glue injection. Three patients were treated by surgery alone, with no complications and complete cure in all. CONCLUSION: Endovascular therapy of intracranial dural arteriovenous fistula may be curative but is often complex and carries definite risks. Neurosurgical ligation of pial draining veins, with pre-operative embolization when safe, may be a relatively more controlled method to achieve complete cure.

Adult↗
PubMed1997

Non-culture diagnosis and serogroup determination of meningococcal B and C infection by a sialyltransferase (siaD) PCR ELISA.

Rapid, non-culture, serogroup determination of meningococcal infection is important in contact management where vaccination may be possible. The impending availability of polysaccharide-protein conjugate vaccines for serogroup C disease requires maximal case ascertainment, with serogroup determination, at a time when the number of culture confirmed meningococcal infections is decreasing. A polymerase chain reaction assay (PCR), based on a restriction fragment length polymorphism (RFLP) in the meningococcal serogroup B and C sialytransferase (siaD) gene, was developed to combine the non-culture diagnosis of meningococcal infection from CSF, whole blood and serum with serogroup (B and C) identification. The PCR assay was adapted to an ELISA format incorporating hybridization with serogroup-specific B and C oligonucleotide probes. Specificity for CSFs was 100% and sensitivities were respectively 81, 63 and 30% for CSFs, whole blood and sera. The serogroup-specific PCR ELISA is a significant addition to currently available tests for non-culture diagnosis of meningococcal infection and outbreak investigation.

Base Sequence↗
PubMed1997

Genotype analysis of human blood isolates of Campylobacter jejuni in England and Wales.

Genomic profiles were obtained for 76 strains of Campylobacter jejuni isolated from bacteraemic patients in England and Wales over the period 1981-94. Genotyping was performed by restriction fragment length polymorphism (RFLP) analysis using a random cloned DNA probe, and by ribotyping with a PCR-generated C. jejuni 16S ribosomal DNA probe. Phenotypic characterization was achieved by heat-stable (HS) and heat-labile (HL) serogrouping, and Preston phagetyping and biotyping. The blood isolates were genomically heterogenous, with 24 RFLP/16S profiles occurring within the 76 strains. Forty-four percent of isolates belonged to one of three RFLP/16S genotypes, reflecting the patterns seen in faecal isolates, except that genotypes usually associated with the HS 1 antigen were uncommon. The two most prevalent genotypes, characteristic of HS 2 and HS 4 strains, showed similarity by cluster analysis. Further evidence was seen of associations between phenotypic and genotypic characters within some HS serogroups. Chromosomal profiling by RFLP analysis does not indicate that particular genotypes have a predisposition to invade the bloodstream.

Bacteremia↗
PubMed1997

Analysis of the human Ig isotype response to individual transferrin binding proteins A and B from Neisseria meningitidis.

Subcapsular antigens, including transferrin binding proteins, are being considered as potential vaccines against serogroup B meningococci. This study examined the human isotype antibody responses in cases of meningococcal disease to meningococcal TbpA (transferrin binding protein A) and TbpB (transferrin binding protein B) from two strains (SD and B16B6) expressing high and low molecular mass TbpB respectively. TbpA isolated from both strains were recognised more frequently and higher durable ELISA absorbance values were detected than those detected against TbpB from either strain. These antibody responses to Tbps were independent of the infecting meningococcal strain type. The antibody response to the four proteins was highly variable between individuals and differed significantly against all four antigens. The variability of immune responses to each Tbp from the two strains suggests that a successful vaccine would need to include TbpA and TbpB from a number of strains.

Antibodies, Bacterial↗
PubMed1997

Carotid artery stenosis: external validity of the North American Symptomatic Carotid Endarterectomy Trial measurement method.

PURPOSE: To assess the generalizability of the North American Symptomatic Carotid Endarterectomy Trial method for determining the degree of stenosis on angiograms. MATERIALS AND METHODS: Six good-quality, baseline angiograms of carotid arteries that were less than 70% stenosed were reviewed by 14 experienced neuroradiologists at different academic institutions. All reviewers determined the degree of stenosis by calculating the ratio of the diameter of the artery at the point of maximal narrowing to the normal diameter distal to the stenosis (well beyond the carotid artery bulb). The reviewers marked the location of their measurements on the angiogram. Comparisons were performed among the reviewers' results and with the reference measurements. RESULTS: Interobserver agreement was 0.84 (95% confidence interval = 0.65, 0.97). The average interobserver disagreement of +/-7% was comparable with that reported in the literature. The overall bias was 6%, which indicated a tendency of the reviewers to overestimate the degree of stenosis in comparison with the reference determination. CONCLUSION: The North American Symptomatic Carotid Endarterectomy Trial reference measurements can be generalized beyond the bounds of this clinical trial, provided that attention is paid to details of the measurement method.

Angiography↗