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Biomedical subjects

John Holton

Publications and source records attributed to John Holton.

14 recordsLinked to original sources
PubMed2006

Human domain antibodies against virulence traits of Candida albicans inhibit fungus adherence to vaginal epithelium and protect against experimental vaginal candidiasis.

Antibody variable domains (domain antibodies [DAbs]) are genetically engineered antibody fragments that include individual heavy-chain (VH) or kappa-chain (Vkappa) variable domains and lack the Fc region. Human DAbs against the 65-kDa mannoprotein (MP65) or the secretory aspartyl proteinase (SAP)-2 of Candida albicans (monospecific DAbs) or against both fungal antigens (heterodimeric, bispecific DAbs) were generated from phage expression libraries. Both monospecific and bispecific DAbs inhibited fungus adherence to the epithelial cells of rat vagina and accelerated the clearance of vaginal infection with the fungus. When heterodimeric DAbs were used, the clearance of infection was at least equivalent to treatment with fluconazole. The in vivo protective effects of DAbs were demonstrated by both pre- and postchallenge schedules of DAb administration and with both fluconazole-susceptible and fluconazole-resistant strains of C. albicans. This is the first demonstration that human DAbs lacking the Fc constituent can efficiently control an infection and can act largely by inhibiting adherence.

Animals↗
PubMed2006

Precise role of H pylori in duodenal ulceration.

The facts that H pylori infection is commoner in duodenal ulcer (DU) patients than in the normal population, and that eradication results in most cases being cured, have led to the belief that it causes DU. However, early cases of DU are less likely than established ones to be infected. H pylori-negative cases are usually ascribed to specific associated factors such as non-steroidal anti-inflammatory drugs (NSAIDs), Crohn's disease, and hypergastrinaemia, but even after excluding these, several H pylori-negative cases remain and are particularly common in areas of low prevalence of H pylori infection. Moreover, this incidence of H pylori negative DU is not associated with a fall in overall DU prevalence when compared with countries with a higher H pylori prevalence. In countries with a high H pylori prevalence there are regional differences in DU prevalence, but no evidence of an overall higher prevalence of DU than in countries with a low H pylori prevalence. There is no evidence that virulence factors are predictive of clinical outcome. After healing following eradication of H pylori infection DU can still recur. Medical or surgical measures to reduce acid output can lead to long-term healing despite persistence of H pylori infection. Up to half of cases of acute DU perforation are H pylori negative. These findings lead to the conclusion that H pylori infection does not itself cause DU, but leads to resistance to healing, i.e., chronicity. This conclusion is shown not to be incompatible with the universally high prevalence of DU compared with controls.

Case-Control Studies↗
PubMed2006

Helicobacter pylori virulence factors in duodenal ulceration: A primary cause or a secondary infection causing chronicity.

Reports from countries with a high prevalence of Helicobacter pylori (H pylori) infection do not show a proportionately high prevalence of duodenal ulceration, suggesting the possibility that H pylori cannot be a primary cause of duodenal ulceration. It has been mooted that this discrepancy might be explained by variations in the prevalence of virulence factors in different populations. The aim of this paper is to determine whether the published literature gives support to this possibility. The relevant literature was reviewed and analyzed separately for countries with a high and low prevalence of H pylori infection and virulence factors. Although virulent strains of H pylori were significantly more often present in patients with duodenal ulcer than without the disease in countries with a low prevalence of H pylori infection in the population, there was no difference in the prevalence of virulence factors between duodenal ulcer, non - ulcer dyspepsia or normal subjects in many countries, where the prevalence of both H pylori infection and of virulence factors was high. In these countries, the presence of virulence factors was not predictive the clinical outcome. To explain the association between virulence factors and duodenal ulcer in countries where H pylori prevalence is low, only two papers were found that give little support to the usual model proposed, namely that organisms with the virulence factors are more likely than those without them to initiate a duodenal ulcer. We offer an alternative hypothesis that suggests virulence factors are more likely to interfere with the healing of a previously produced ulcer. The presence of virulence factors only correlates with the prevalence of duodenal ulcer in countries where the prevalence of H pylori is low. There is very little evidence that virulence factors initiate duodenal ulceration, but they may be related to failure of the ulcer to heal.

Duodenal Ulcer↗
PubMed2005

Bactericidal and anti-adhesive properties of culinary and medicinal plants against Helicobacter pylori.

AIM: To investigate the bactericidal and anti-adhesive properties of 25 plants against Helicobacter pylori (H. pylori). METHODS: Twenty-five plants were boiled in water to produce aqueous extracts that simulate the effect of cooking. The bactericidal activity of the extracts was assessed by a standard kill-curve with seven strains of H. pylori. The anti-adhesive property was assessed by the inhibition of binding of four strains of FITC-labeled H. pylori to stomach sections. RESULTS: Of all the plants tested, eight plants, including Bengal quince, nightshade, garlic, dill, black pepper, coriander, fenugreek and black tea, were found to have no bactericidal effect on any of the isolates. Columbo weed, long pepper, parsley, tarragon, nutmeg, yellow-berried nightshade, threadstem carpetweed, sage and cinnamon had bactericidal activities against H. pylori, but total inhibition of growth was not achieved in this study. Among the plants that killed H. pylori, turmeric was the most efficient, followed by cumin, ginger, chilli, borage, black caraway, oregano and liquorice. Moreover, extracts of turmeric, borage and parsley were able to inhibit the adhesion of H. pylori strains to the stomach sections. CONCLUSION: Several plants that were tested in our study had bactericidal and/or anti-adhesive effects on H. pylori. Ingestion of the plants with anti-adhesive properties could therefore provide a potent alternative therapy for H. pylori infection, which overcomes the problem of resistance associated with current antibiotic treatment.

Anti-Bacterial Agents↗
PubMed2005

Comparison of image analysis software packages in the assessment of adhesion of microorganisms to mucosal epithelium using confocal laser scanning microscopy.

We have compared current image analysis software packages in order to find the most useful one for assessing microbial adhesion and inhibition of adhesion to tissue sections. We have used organisms of different sizes, the bacterium Helicobacter pylori and the yeast Candida albicans. Adhesion of FITC-labelled H. pylori and C. albicans was assessed by confocal microscopy. Four different Image analysis software packages, NIH-Image, IP Lab, Image Pro+, and Metamorph, were compared for their ability to quantify adhesion of the two organisms and several quantification methods were devised for each package. For both organisms, the dynamic range that could be detected by the software packages was 1x10(6)-1x10(9) cells/ml. Of the four software packages tested, our results showed that Metamorph software, using our 'Region of Interest' method, with the software's 'Standard Area Method' of counting, was the most suitable for quantifying adhesion of both organisms because of its unique ability to separate clumps of microbial cells. Moreover, fewer steps were required. By pre-incubating H. pylori with the glycoconjugate Lewis b-HSA, an inhibition of binding of 48.8% was achieved using 250 mug/ml Lewis b-HSA. The method we have devised using Metamorph software, provides a simple, quick and accurate way of quantifying adhesion and inhibition of adhesion of microbial cells to the epithelial surface of tissue sections. The method can be applied to organisms ranging in size from small bacteria to larger yeast cells.

Animals↗
PubMed2004

Are Helicobacter species and enterotoxigenic Bacteroides fragilis involved in inflammatory bowel disease?

The aim of this study was to determine if either Helicobacter or enterotoxigenic Bacteroidesfragilis (ETBF) was linked to inflammatory bowel disease (IBD), using PCR. We analyzed the luminal washings and colonic biopsies of 35 patients with IBD and 37 control patients. The presence of Helicobacter was confirmed in the luminal washing of one IBD patient and three control patients and in the biopsies of two IBD patients. Ten of 28 control patients and 8 of 32 IBD patients had a positive luminal washing for the enterotoxin gene. Six of 33 control patients and 4 of 32 IBD patients had positive biopsies. The prevalence of the enterotoxin gene was higher in IBD patients with active disease compared with patients with inactive disease, although it did not achieve statistical significance. In conclusion, Helicobacter was not associated with IBD in our population of patients, although ETBF may be associated with active disease.

Adult↗
PubMed2004

Helicobacter pylori: current status and future prospects.

Helicobacter pylori is a global pathogen that causes severe gastrointestinal diseases leading to a significant morbidity and mortality. There is an effective treatment for peptic ulcer disease, however, this is being compromised by an increase in the prevalence of antibiotic resistance. Although alternative rescue regimens have been advocated, the best strategy would be to prevent disease, especially in the case of gastric cancer for which there is still no treatment. One approach is to inhibit the first step in the pathogenic process - adhesion of the organism to the host tissue. Another and probably a better approach is vaccination, but clinical trials have so far been unsuccessful. There is still a large uncertainty in relation to how H. pylori causes disease. Knowledge from genomics, proteomics, and the relationship between polymorphism of the bacterium and the host, as well as the continuing investigation of the role played by important virulence factors in the outcome of the disease, will help both in understanding pathogenesis of disease and in the design of the best vaccine.

Animals↗
PubMed2003

Innate immunity and pathogen-host interaction.

The skin and contiguous mucosal surfaces define the primary locus of interaction between host and micro-organisms. In this review, we focus on the innate immune system in the mucosa, which manages to deal with invading pathogens, the mechanisms that organisms have evolved in order to circumvent this primary defensive barrier and, finally, potential therapeutic manipulation of the innate immune system that was the focus of meeting at a Euroconference/Workshop on "Novel Strategies of Mucosal Immunisation through Exploitation of Mechanisms of Innate Immunity in Pathogen-Host Interaction", which was held in Siena, Italy, November 2002.

Animals↗
PubMed2003

Widespread occurrence of Mycobacterium tuberculosis DNA from 18th-19th century Hungarians.

A large number (265) of burials from 1731-1838 were discovered in sealed crypts of the Dominican Church, Vác, Hungary in 1994. Many bodies were naturally mummified, so that both soft tissues and bones were available. Contemporary archives enabled the determination of age at death, and the identification of family groups. In some cases, symptoms before death were described and, occasionally, occupation. Initial radiological examination of a small number of individuals had indicated calcified lung lesions and demonstrable acid-fast bacteria suggestive of tuberculosis infection. Tuberculosis was endemic in 18th-19th century Europe, so human remains should contain detectable Mycobacterium tuberculosis complex (MTB) DNA, enabling comparisons with modern isolates. Therefore, a comprehensive examination of 168 individuals for the presence of MTB DNA was undertaken. Specific DNA amplification methods for MTB showed that 55% of individuals were positive and that the incidence varied according to age at death and sampling site in the body. Radiographs were obtained from 27 individuals and revealed an association between gross pathology and the presence of MTB DNA. There was an inverse relationship between PCR positivity and MTB target sequence size. In some cases, the preservation of MTB DNA was excellent, and several target gene sequences could be detected from the same sample. This information, combined with MTB DNA sequencing data and molecular typing techniques, will enable us to study the past epidemiology of TB infection, and extends the timeframe for studying changes in molecular fingerprints.

Adolescent↗
PubMed2003

Antimicrobial activity of esomeprazole versus omeprazole against Helicobacter pylori.

OBJECTIVE: Esomeprazole is an enantiomorph of omeprazole, which inhibits gastric acid secretion more effectively than omeprazole. As proton pump inhibitors also exert an antibacterial activity, we aimed to compare esomeprazole and omeprazole for their antimicrobial activity against Helicobacter pylori in vitro. METHODS: We studied 52 H. pylori isolates obtained from gastric biopsies and inoculated onto agar plates containing the acid-converted drugs at different concentrations. The minimal concentrations that inhibited the growth of 50% and 90% of isolates were defined as MIC(50) and MIC(90). RESULTS: The MIC(50) and MIC(90) of esomeprazole were 16 and 32 mg/L; and those of omeprazole were 32 and 64 mg/L. Overall, 63.5% of isolates showed the same susceptibility to both drugs; 17 isolates were two- to 64-fold more susceptible to esomeprazole and two isolates were two-fold more susceptible to omeprazole. CONCLUSIONS: The increased antimicrobial activity in vitro of esomeprazole against H. pylori could contribute to improving the outcome of the eradication treatment of such an infection.

Adult↗
PubMed2003

Susceptibility of Helicobacter pylori to metronidazole.

OBJECTIVES: The reliability of the Epsilometer-test (E-Test) and the disk diffusion (DD) method in the assessment of susceptibility of Helicobacter pylori (H. pylori) to metronidazole has recently been questioned, with possible clinical implications for the management of patients undergoing H. pylori eradication. The aims of this study were: 1) to compare the E-Test and disk diffusion methods to the agar dilution method for determining the susceptibility of H. pylori to metronidazole; and 2) to investigate whether potential discrepancies could be caused by the simultaneous presence of metronidazole susceptible and metronidazole resistant bacterial subpopulations. METHODS: A total of 109 H. pylori strains from 121 consecutive patients were examined. All tests were carried out at the same time starting from primary plates. Agar dilution was performed according to National Committee for Clinical Laboratory Standard (NCCLS) standards, the E-Test according to the manufacturer's guidelines, and disk diffusion according to standard procedure using 5-mug metronidazole disks. Isolates were considered to be metronidazole resistant if the minimal inhibitory concentration was >8 mug/ml for the agar dilution and the E-Test, or if the inhibition zone around the disk was <20 mm for disk diffusion. Of 109 isolates, 43 were also investigated to detect mixed infection. Quantities of 100 mul of bacterial suspensions of each strain were seeded onto plain agar plates and plates containing 8 mug/ml of metronidazole. Cultures were considered to be mixed if the number of colonies on agar plates exceeded by at least 30% those on the metronidazole plates. RESULTS: According to agar dilution, 57 strains (52.3%, 95% CI = 43-61.4) were metronidazole resistant. E-Test misdiagnosed two strains that were considered sensitive to metronidazole, but according to the agar dilution test they were resistant. Disk diffusion misdiagnosed three strains. Two of these strains (the same as the E-Test) were sensitive, but according to agar dilution they were metronidazole resistant; the third strain was resistant, but according to agar dilution it was sensitive. The percentages of discordance were 1.9 (95% CI = 0.5-6.6) and 2.8 (95% CI = 0.9-7.8), respectively, when the E-Test and disk diffusion were compared to agar dilution. Intertest variability among agar dilution and the E-Test showed that 39.4% (95% CI = 30.8-48.8) of minimal inhibitory concentrations were equivalent (within +/-1 log(2)), 60.6% (95% CI = 51.2-69.2) were major errors (more than +/-1 log(2)), and 3% (95% CI = 0.8-10.4) were very major errors (change in susceptibility pattern). Mixed infection was found in six of the 43 cases examined (13.9%). In four cases, metronidazole resistant strains were 1 log(10) less numerous than those that were metronidazole susceptible. In the remaining two cases, the metronidazole resistant strains were 2-3 log(10) less numerous, which caused the two misdiagnoses. CONCLUSIONS: The E-Test and disk diffusion method are very good alternatives to agar dilution. Mixed infections are a possible cause of the discrepancies between these tests and the reference method.

Adult↗
PubMed2002

Inflammatory bowel disease: is the intestine a Trojan horse?

Inflammatory bowel disease (IBD) is a chronic relapsing inflammatory condition of the intestines that is clinically heterogenous. The cause(s) of IBD are currently unknown but the mechanisms of injury are immunological. Increasingly there is an emphasis on the study of the complex interactions at the interface of self and non-self--the gastrointestinal epithelial surface--in relationship to the pathogenesis of disease. There is mounting evidence that a lack of tolerance to the normal commensal flora of the intestine may underlie the disease pathogenesis. Several genetic loci that are markers of disease susceptibility have been identified. These loci map to areas of the genome that are concerned with antigen presentation or cytokine secretion and suggest a genetic heterogeneity that underlies the clinical differences. Overall a picture is emerging of defects in epithelial barrier function and, or immunoregulation leading to immune responses that are triggered or exaggerated by the antigenic components of the normal flora.

Epithelium↗
PubMed2002

Helicobacter: a paradigm shift in peptic ulcer disease and more?

There are many diseases where the cause is unknown and this makes a specific treatment difficult. In many cases all that can be achieved is amelioration of the illness. Peptic ulcer disease was one such condition no more that 20 years ago. The management was drastic--either an operation or life-long medication in order to reduce the acid secreted by the stomach. However, the cause of this condition was discovered in 1983. Although initially sceptical, the medical fraternity now almost universally endorse Helicobacter pylori as the cause of the majority of stomach ulcers. Peptic ulcers can now be cured by antibiotics. This is a major shift in medical practice. Continued investigations on Helicobacter pylori are bringing to light other possible associations with disease as well as delineating plausible biological mechanisms for disease pathogenesis.

Autoantibodies↗