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Biomedical subjects

S C Clarke

Publications and source records attributed to S C Clarke.

At least 19 recordsLinked to original sources
PubMed2003

Analysis of PorA variable region 3 in meningococci: implications for vaccine policy?

Outer membrane protein (OMP) vaccines are being developed against Neisseria meningitidis serogroup B which may provide protection against common circulating serotypes and serosubtypes in some countries. However, limited data is available in Europe from genosubtyping meningococci. We therefore undertook a retrospective analysis of the three main variable regions, VR1, VR2 as well as VR3, of the porA gene from N. meningitidis isolated from different countries, mainly from Scotland and Sweden. Analysis of this gene showed that, amongst 226 strains studied, there were a total of 78 different strains. No new VR1 or VR2 alleles were found but five new VR3 alleles are described. Our data indicates the importance of analysing the VR3 region of PorA in addition to VR1 and VR2 and also highlights, in general terms, the need for genosubtyping meningococci. Such analyses have major implications for the design of new meningococcal vaccines.

Amino Acid Sequence↗
PubMed2003

Cyclospora cayetanensis infection in Lagos, Nigeria.

Although reports of Cyclospora infection continue to increase globally, few cases have been reported from the African continent. We present 11 cases of cyclosporiasis detected from stool samples submitted to seven major hospital laboratories in Lagos, Nigeria between March 1999 and April 2000.

Adult↗
PubMed2003

Detection and genotyping of meningococci using a nested PCR approach.

An effective vaccine against Neisseria meningitidis serogroup B is required. Outer-membrane protein vaccines have been developed, which may provide protection against common circulating serotypes and serosubtypes in some countries. However, limited genosubtyping data are available because most laboratories use mAbs directed against a limited number of specific serotypes and serosubtypes and laboratories do not genosubtype directly from body fluids due to the lack of a sensitive PCR method. A nested PCR was therefore developed that enables the amplification of the porA gene directly from clinical samples and has the required sensitivity for nucleotide sequencing of the three main variable regions, VR1, VR2 and VR3. Data were compared with those from culture-based nucleotide sequencing, and the use of this method increased the availability of genosubtype information by 45 %, thereby indicating the impact that this methodology has on the data provided and the implications for vaccine design.

Genes, Bacterial↗
PubMed2003

Virulence of enteropathogenic Escherichia coli, a global pathogen.

Enteropathogenic Escherichia coli (EPEC) remains an important cause of diarrheal disease worldwide. Research into EPEC is intense and provides a good virulence model of other E. coli infections as well as other pathogenic bacteria. Although the virulence mechanisms are now better understood, they are extremely complex and much remains to be learnt. The pathogenesis of EPEC depends on the formation of an ultrastructural lesion in which the bacteria make intimate contact with the host apical enterocyte membrane. The formation of this lesion is a consequence of the ability of EPEC to adhere in a localized manner to the host cell, aided by bundle-forming pili. Tyrosine phosphorylation and signal transduction events occur within the host cell at the lesion site, leading to a disruption of the host cell mechanisms and, consequently, to diarrhea. These result from the action of highly regulated EPEC secreted proteins which are released via a type III secretion system, many genes of which are located within a pathogenicity island known as the locus of enterocyte effacement. Over the last few years, dramatic increases in our knowledge of EPEC virulence have taken place. This review therefore aims to provide a broad overview of and update to the virulence aspects of EPEC.

Bacterial Adhesion↗
PubMed2003

Comparison of commercial DNA extraction kits for extraction of bacterial genomic DNA from whole-blood samples.

The demand for molecular diagnostic tests in medical microbiology has highlighted the need for efficient methods of DNA extraction. In addition, it is preferable for these methods to be automated. An example of such a requirement is for the confirmation of meningococcal disease where rapid, sensitive, and specific procedures are required for public health management purposes. Previous studies have shown that whole blood is the preferred method for the isolation of bacterial DNA in meningococcal disease, and in this study, we compare five commercially available kits for the extraction of bacterial genomic DNA from whole-blood samples. These include kits in a 96-well binding plate, 96-well filter plate, and metallic bead formats. The method for all five kits is described, and the sensitivity, specificity, ease of automation, and overall efficiency are determined.

Blood↗
PubMed2003

Nucleotide sequence analysis of the sialyltransferase genes of meningococcal serogroups B, C, Y and W135.

A rapid method for serogrouping meningococci is essential for the characterization of phenotypically non-groupable meningococcal isolates and clinical samples, particularly for public health management purposes. The Scottish Meningococcus and Pneumococcus Reference Laboratory (SMPRL) provides serogrouping results of meningococcal isolates and clinical samples using a PCR assay which detects restriction fragment length polymorphisms in meningococcal serogroups B, C, Y and W135. Although this PCR system was invaluable when first introduced, it has several drawbacks and lacks the required sensitivity for detecting DNA in clinical samples. Due to the recent introduction of the meningococcal group C conjugate vaccine and an impending group B vaccine, a more robust and informative method for serogroup determination is required. A protocol was devised allowing PCR amplification of the siaD gene of serogroup B, C, Y and W135 meningococci. This system was multiplexed and allowed serogroup differentiation between serogroups B and C and also between B/C and Y/W135 by product size analysis. A nested stage was incorporated into the system for enhanced detection of meningococci in clinical samples, and finally a sequencing protocol was designed allowing detection of any nucleotide changes within the siaD gene. This system allows rapid serogrouping results for use within an agarose gel system as well as more informative results when used for sequencing within the siaD gene.

Bacterial Typing Techniques↗
PubMed2002

Cyclospora cayetanensis in stools submitted to hospitals in Lagos, Nigeria.

BACKGROUND: Cyclospora cayetanensis is an emerging human pathogen associated with gastrointestinal disease. The epidemiology and biology of the parasite are poorly understood, and numerous outbreaks of cyclosporiasis have been recorded from around the world since 1990, but the incidence of the parasite in Nigeria has not been described. DESIGN AND METHODS: A cross-sectional, laboratory-based study was conducted in Lagos-metropolis state in southwestern Nigeria. All stool samples submitted to the Microbiology and Parasitology Department between March 1999 and April 2000 were processed for the presence of Cyclospora cayetanensis. Data from each patient were obtained from health records and via questionnaires, including age, sex and reason for hospital visit. RESULTS: In total, 1109 stool samples were collected during the period of study. Eleven (0.99%) were confirmed to be positive for Cyclospora cayetanensis oocysts. Other parasites were also detected, including Cryptosporidium sp., Entamoeba sp., Ascaris, Trichuris, Strongyloides sp., and hookworm. CONCLUSIONS: Cyclospora cayetanensis is an infrequent but important cause of gastrointestinal disease in Lagos, Nigeria. This is the first report of Cyclospora infection in Nigeria and suggests that medical practitioners and laboratory scientists should be made more aware of the infection.

Adolescent↗
PubMed2002

Enteropathogenic Escherichia coli infection: history and clinical aspects.

Diarrhoeagenic Escherichia coli remains an important cause of diarrhoeal disease worldwide. In terms of global public health, enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli are the most important. However, enterohaemorrhagic E. coli has emerged as a cause of disease in developed countries in recent years, and a number of large outbreaks have been reported. Therefore, the importance of research into diarrhoeagenic E. coli remains an important issue. EPEC is the most widespread of the diarrhoeagenic E. coli and provides a good virulence model for other E. coli infections, as well as other pathogenic bacteria. Although the virulence mechanisms of E. coli are now better understood, there remains much to be learned before effective treatments can be developed. Type III secretion mechanisms, the locus of enterocyte effacement and various toxins are all involved in the pathogenesis of the various diarrhoeagenic E. coli and may provide targets for future therapies. This review aims to provide an update on the worldwide problem of diarrhoeagenic E. coli by focusing on EPEC, and describes the history of the organism, its incidence and the clinical aspects of infection.

Diarrhea↗
PubMed2002

Semi-automation of the polymerase chain reaction for laboratory confirmation of meningococcal disease.

Demand for accurate high-throughput detection and characterisation of medically important bacteria has increased dramatically within research and clinical laboratories. Liquid-handling robots have been developed to achieve high levels of accuracy and reproducibility. Assay automation can play a key role in the modern diagnostic laboratory and the data presented here shows that automated PCR is comparable with manual methods. Importantly, automation is preferred when high-quality results cannot be guaranteed using manual methods. This is particularly important when results are required quickly for public health management.

Bacteriological Techniques↗
PubMed2002

Clinical aspects of pneumonia.

Pneumonia is a serious medical condition and a major cause of morbidity and mortality worldwide. It has many infectious aetiologies, although bacterial and viral forms are most common. Our understanding of pneumonia has improved significantly during the course of the 20th century but the overall disease burden has changed little. Although antibiotics have helped to reduce the mortality associated with some types of pneumonia, the level of morbidity remains constant. Furthermore, the existence of antibiotic-resistant bacteria worldwide is becoming an increasing problem in treatment. This essay describes the different types of pneumonia from a clinical perspective and highlights the problems associated with the condition.

Diagnosis, Differential↗
PubMed2002

Bioterrorism: an overview.

Bioterrorism has reached the forefront of the public imagination following recent events across the world. The disaster of 11 September 2001, followed by anthrax letters sent via the US postal system and now renewed tension over Iraq have all brought the possibility of bioterrorism closer. A number of biological agents could be used in a terrorist attack, including anthrax, plague, smallpox and botulinum toxin. The serious diseases that these agents produce have been brought under control in the developed world; however, a lack of protective immunity against such diseases could cause considerable morbidity and mortality if used in a terrorist attack. This essay provides a background to bioterrorism, discusses many of the current points of interest and gives an update to the economic consequences of such an attack.

Bioterrorism↗
PubMed2002

A study of hormone replacement therapy in postmenopausal women with ischaemic heart disease: the Papworth HRT atherosclerosis study.

OBJECTIVE: To assess the possible benefit of hormone replacement therapy (HRT) in the secondary prevention of ischaemic heart disease. DESIGN: A prospective randomised trial of transdermal HRT in women with definite ischaemic heart disease. SETTING: A regional cardiac unit. POPULATION: Postmenopausal women with angiographically proven ischaemic heart disease. METHODS: A total of 255 postmenopausal women with angiographically proven ischaemic heart disease were recruited and randomised; 134 were treated with transdermal HRT and 121 acted as controls. The women were seen at six monthly intervals. The primary end points, which were determined by a blinded assessor, were admission to hospital with unstable angina, proven myocardial infarction or cardiac death. A total of 53 (40%) patients withdrew from the HRT group and eight (7%) from the control group. The mean duration of follow up was 30.8 months. MAIN OUTCOME MEASURES: Admission to hospital with unstable angina, proven myocardial infarction or cardiac death. RESULTS: During follow up, there were 53 primary end-point events in the HRT group and 37 in the control group. Using an intention-to-treat analysis, the primary end-point event rate was 15.4 events per 100 patient years for the HRT group compared with 11.9 for the control group (event rate ratio 1.29 (95% CI 0.84-1.95, P = 0.24)). Using a per-protocol analysis, there was an event rate ratio of 1.49 (0.93-2.36, P = 0.11) for the HRT arm compared with the control arm. Particularly during the first two years of follow up, the HRT group had a higher, but not statistically significant, event rate than the control group. CONCLUSION: Our findings suggest that transdermal HRT should not be commenced for the purpose of secondary prevention in postmenopausal women with angiographically proven ischaemic heart disease.

Administration, Cutaneous↗
PubMed2002

Laboratory confirmation of meningococcal disease in Scotland, 1993-9.

AIMS: To describe the laboratory confirmation of meningococcal disease, using culture and non-culture based techniques, between 1993 and 1999 as part of a national service in Scotland. METHODS: Samples from patients with suspected meningococcal disease in Scotland were analysed by culture and non-culture based techniques to gain a laboratory confirmation of disease. Data were analysed to establish the number of disease cases, the serogroups of the organisms involved, and the importance of the techniques used. RESULTS: Between 1993 and 1999, there was a total of 1749 notified cases of meningococcal disease in Scotland. Culture based methods provided a laboratory confirmation of 788 cases whereas non-culture techniques confirmed 461 cases. CONCLUSIONS: Non-culture techniques were a useful addition to culture based techniques in Scotland and improved the dataset required for public health management, disease surveillance, and vaccine policy.

Agglutination Tests↗
PubMed2002

Automated PCR/sequence template purification.

A commercially available filtration method is described for the purification of polymerase chain reaction (PCR) templates and sequence-labeled products. The methodology is described for the automation of this application and its use on a high-throughput liquid handling robot and capillary-based automated DNA sequencer. The application provides good-quality DNA, is relatively cheap, and can be used in either 96- or 384-well format.

Bacterial Typing Techniques↗