Biomedical subjects

D Y Graham

Publications and source records attributed to D Y Graham.

At least 109 records · Page 6Linked to original sources

PubMed2000

Frameshift mutations in rdxA and metronidazole resistance in North American Helicobacter pylori isolates.

In Helicobacter pylori, the oxygen-insensitive nitroreductase RdxA is likely to activate metronidazole (Mtz) by reduction and formation of cytotoxic intermediates. Mutations in rdxA have been associated with Mtz resistance in H. pylori. In vitro Mtz susceptibilities of 17 randomly selected H. pylori isolates were determined by the agar dilution method. DNA sequence analysis of rdxA alleles of eight susceptible isolates (MIC range: 0.25-1.0 mg/L) and nine resistant isolates (MIC range: 16-256 mg/L) showed that six of nine Mtz-resistant H. pylori isolates contained insertion or deletion mutations ('indel' mutations). One isolate contained a substitution mutation at codon position 148 that resulted in the introduction of a premature stop codon. Creation of stop codons within the rdxA coding sequence by either frameshift or substitution mutations resulted in premature translation termination and expression of putatively truncated RdxA polypeptides.

Anti-Bacterial Agents↗

PubMed2000

Helicobacter pylori infection in children of Texas.

BACKGROUND: Acquisition of the Helicobacter pylori infection usually occurs in childhood. The prevalence of infection differs among ethnic groups and in adults is inversely related to the socioeconomic status of the individual's family during childhood. This study investigates the seroprevalence of H. pylori infection in children of different ethnic groups in relation to socioeconomic class and investigates the prevalence of acute H. pylori infection among children who have had recent onset of abdominal pain. METHODS: Serum samples were collected from 797 children, aged 6 months to 18 years, of various socioeconomic and ethnic backgrounds, at a large urban children's hospital. H. pylori status was determined by an anti-H. pylori immunoglobulin (Ig)G enzyme-linked immunosorbent assay (ELISA) validated for pediatric use. To determine the prevalence of acute H. pylori infection, children brought to the emergency center with abdominal symptoms without diarrhea and overt signs of acute abdomen were evaluated with both serology and the 13C-urea breath test. Acute H. pylori was defined as a positive 13C-urea breath test result and negative IgG serology for H. pylori. RESULTS: The overall seroprevalence of H. pylori was 12.2% and increased with age (e.g., 8.3% at 6-11.9 months and 17.9% at 13 years). The prevalence was inversely related to socioeconomic status (6.6%, moderate to high vs. 15%, low socioeconomic status). The difference in seroprevalence among blacks (16.8%), Hispanics (13.3%), and whites (8.3%; P < 0.01) could be accounted for by differences in socioeconomic status. Eighteen percent of children who were evaluated at the emergency center for recent-onset abdominal pain had acute H. pylori infections. CONCLUSIONS: Socioeconomic status, not ethnic group, is the more important risk factor for acquisition of H. pylori infection during childhood. Acute H. pylori infection was a relatively common cause of recent-onset, nonsurgical abdominal pain.

Abdominal Pain↗

PubMed2000

H. pylori in the pathogenesis of duodenal ulcer: interaction between duodenal acid load, bile, and H. pylori.

OBJECTIVE: Helicobacter pylori (H. pylori) growth is inhibited by bile yet it can grow in the duodenal bulb and cause ulcer disease. The aim of this study was to test the effect of bile on H. pylori viability and growth and to determine whether acidification of bile reduces its inhibitory activity. METHODS: Fresh human bile was collected at laparotomy and tested for inhibitory activity of H. pylori using broth dilution assays. Six clinical isolates of H. pylori obtained from patients with duodenal ulcer were used for each experiment. The bile was diluted from 1:3 to 1:192; its inhibitory effect on H. pylori was tested before and after acidification, treatment with cholestyramine, or chloroform. Bile was acidified to a pH of 2-6, centrifuged at 8000 rpm for 20 min to remove precipitated bile acids, and the supernatant pH readjusted. Controls included BHI broth without bile (positive control) and bile that was acidified to pH 2 and neutralized without centrifugation. RESULTS: Human bile inhibited H. pylori growth in a dose dependent manner. Growth of all strains was supported for all strains only at a dilution of 1:192. In contrast, after acidification to pH < or =5 and centrifugation to remove precipitated bile acids, all strains grew at a bile dilution of 1:12. Neither chloroform extraction of lipids, nor acidification without centrifugation removed the inhibitory action of bile. In contrast, cholestyramine sequestration of bile acids completely removed all inhibitory activity. CONCLUSIONS: The duodenal acid load may be the critical factor to explain the ability of H. pylori to colonize the duodenal bulb by precipitating glycine-conjugated bile salts. The combination of a high duodenal acid load and H. pylori infection is likely the critical event in the pathogenesis of H. pylori-related duodenal ulcer disease.

Bile↗

PubMed2000

Sustained increase in gastric antral epithelial cell proliferation despite cure of Helicobacter pylori infection.

OBJECTIVE: Studies of the effect of Helicobacter pylori treatment on gastric mucosa proliferation have yielded inconsistent results. We compared gastric mucosa cell proliferation posttherapy and in uninfected controls. METHODS: Biopsies were obtained from patients with H. pylori infection before treatment and at intervals for up to 33 months. Epithelial cell proliferation was determined using Ki-67 immunostaining. The labeling index (LI) is the proportion of positively labeled cells with respect to the total number of cells. The proliferative index was calculated by multiplying the labeling index (LI) and the proliferation zone PZ (PZ = length of the area between the uppermost and lowest labeled cells). RESULTS: The study included 27 patients with H. pylori gastritis and 35 controls. Epithelial cell proliferation (LI) was greater with H. pylori infection than without in both the antrum and corpus (65+/-5 vs 91+/-8 in the antrum and 44+/-4 vs 72+/-8 in the corpus, for uninfected controls vs H. pylori gastritis, respectively) (p = 0.0001). In the antrum there was no significant decrease in epithelial cell proliferation after cure of the H. pylori infection despite follow-up for >2 yr (labeling index = 83+/-10). In contrast, epithelial cell proliferation decreased in the corpus and became similar to that in controls after 7-13 months. CONCLUSIONS: Patients with H. pylori infection have sustained high epithelial cell proliferation in the antrum compared to that in uninfected subjects. A continued increase in proliferation in the antrum after cure of H. pylori infection suggests continuing damage.

Anti-Ulcer Agents↗

PubMed2000

Topographic patterns of intestinal metaplasia and gastric cancer.

OBJECTIVE: The role of intestinal metaplasia in gastric oncogenesis has been demonstrated by both cross-sectional and longitudinal studies. This study was designed to determine whether, in a population at high risk for gastric cancer, different topographical patterns and phenotypes of intestinal metaplasia were associated with different degrees of cancer risk. METHODS: A total of 68 Colombian patients with gastric cancer and 67 controls with nonulcer dyspepsia were studied by an extensive biopsy protocol. Intestinal metaplasia was assessed semiquantitatively by histology and was characterized histochemically. In both patients and controls, the Spearman's correlation test was applied to the test if the gastric distribution of metaplastic lesions resulted in specific topographical patterns associated with different risks for cancer. RESULTS: Four topographical patterns of intestinalization emerged: 1) "Focal," in 14 cancer patients and 16 controls; 2) "Antrum-predominant," in seven cancer patients and six controls; 3) "Magenstrasse" (involving the lesser curvature from cardia to pylorus) in 25 cancer patients and four controls. This pattern was associated with higher cancer risk (OR = 5.7; 95% CI: 1.3-26) than were the two less extensive patterns; and 4) "Diffuse," involving essentially the entire gastric mucosa with the exception of the fundus, was unique to 13 cancer patients. The OR for cancer was 12.2; 95% CI: 2.0-72.9. Incomplete-type metaplasia significantly correlated with the extent of total metaplasia and was also associated with greater cancer risk. CONCLUSIONS: In a population with high risk for gastric cancer, the extension of intestinal metaplasia correlates with the extent of its "incomplete" phenotype and is significantly associated with increased cancer risk. Both the extent and location of intestinal metaplasia along the lesser curvature (from the cardia to the prepyloric zones) identify patients with the highest cancer risk.

Adenocarcinoma↗

PubMed2000

An endoscopic comparison of the effects of alendronate and risedronate on upper gastrointestinal mucosae.

OBJECTIVES: The nitrogen-containing bisphosphonates alendronate and risedronate have been reported to have upper gastrointestinal (GI) safety and tolerability profiles comparable to those of placebo. Nevertheless, both agents have demonstrated similar potential for irritation of gastric mucosa at high doses in preclinical studies. The present study compared the potential for alendronate and risedronate to produce endoscopic upper GI mucosal irritation using the highest approved dosage regimens for the two agents. METHODS: This was a multicenter, randomized, parallel-group, double-blind, placebo-controlled trial in which a total of 235 patients (men or postmenopausal women, aged 45-80 yr) with normal upper GI endoscopy at baseline received 28-day treatments with the following: alendronate 40 mg/day (N = 90), risedronate 30 mg/day (N = 89), placebo (N = 36), or placebo with aspirin 650 mg q.i.d. for the last 7 days (N = 20). Endoscopy was repeated on day 29 using standardized scoring scales. RESULTS: After 28 days of treatment, the alendronate and risedronate groups had comparable mean gastric and duodenal erosion scores that were significantly lower than those of the aspirin group. Esophageal scores were comparable in all groups. Gastric ulcers and/or large numbers of gastric erosions occurred in approximately 3% of alendronate and risedronate patients versus 60% with aspirin. Both bisphosphonates were clinically well tolerated. CONCLUSIONS: The potential for gastroduodenal irritation is similar for alendronate and risedronate and is markedly less than for aspirin. The findings of this study, together with the large placebo-controlled clinical trial experience with both agents and extensive epidemiological data for alendronate, suggest that the risk for clinically important gastric irritation with these bisphosphonates is very low, even at the highest available doses.

Aged↗

PubMed2000

Isolation and characterization of tetracycline-resistant clinical isolates of Helicobacter pylori.

Tetracycline is an important component of combination therapies for Helicobacter pylori eradication. Twenty-nine tetracycline-resistant isolates requiring MICs ranging from 4 to 16 microgram/ml were isolated from Korean (22 of 460) and Japanese (7 of 105) patients. Interestingly, all of the 29 tetracycline-resistant isolates exhibited cross-resistance to metronidazole, and the cross-resistance was transferred to tetracycline-sensitive H. pylori strains.

Drug Resistance, Multiple↗

PubMed2000

Analysis of rdxA and involvement of additional genes encoding NAD(P)H flavin oxidoreductase (FrxA) and ferredoxin-like protein (FdxB) in metronidazole resistance of Helicobacter pylori.

Metronidazole (Mtz) is a critical ingredient of modern multidrug therapies for Helicobacter pylori infection. Mtz resistance reduces the effectiveness of these combinations. Although null mutations in a rdxA gene that encodes oxygen-insensitive NAD(P)H nitroreductase was reported in Mtz-resistant H. pylori, an intact rdxA gene has also been reported in Mtz-resistant H. pylori, suggesting that additional Mtz resistance mechanisms exist in H. pylori. We explored the nature of Mtz resistance among 544 clinical H. pylori isolates to clarify the role of rdxA inactivation in Mtz resistance and to identify another gene(s) responsible for Mtz resistance in H. pylori. Mtz resistance was present in 33% (181 of 544) of the clinical isolates. There was marked heterogeneity of resistance, with Mtz MICs ranging from 8 to >/=256 microg/ml. rdxA inactivation resulted in Mtz MICs of up to 32 microg/ml for 6 Mtz-sensitive H. pylori strains and 128 microg/ml for one Mtz-sensitive strain. Single or dual (with rdxA) inactivation of genes that encode ferredoxin-like protein (designated fdxB) and NAD(P)H flavin oxidoreductase (frxA) also increased the MICs of Mtz for sensitive and resistant strains with low to moderate levels of Mtz resistance. fdxB inactivation resulted in a lower level of resistance than that from rdxA inactivation, whereas frxA inactivation resulted in MICs similar to those seen with rdxA inactivation. Further evidence for involvement of the frxA gene in Mtz resistance included the finding of a naturally inactivated frxA but an intact rdxA in an Mtz-resistant strain, complementation of Mtz sensitivity from an Mtz-sensitive strain to an Mtz-resistant strain or vice versa by use of naturally inactivated or functional frxA genes, respectively, and transformation of an Mtz-resistant Escherichia coli strain to an Mtz sensitive strain by a naturally functional frxA gene but not an inactivated frxA gene. These results are consistent with the hypothesis that null mutations in fdxB, frxA, or rdxA may be involved in Mtz resistance.

Amino Acid Sequence↗

PubMed2000

Regional differences in metronidazole resistance and increasing clarithromycin resistance among Helicobacter pylori isolates from Japan.

The patterns of antibiotic resistance in Helicobacter pylori were assessed in two different regions in Japan. Overall, prevalences of resistance to metronidazole and clarithromycin were 12.4 and 12.9%, respectively. While there was no difference in clarithromycin resistance, the prevalence of metronidazole resistance was significantly higher in Kyoto (23.8%) than in Sapporo (8.1%). From 1996 to 1999, the prevalence of metronidazole resistance did not change but the prevalence of clarithromycin resistance doubled (from 9.1 to 18.7%).

Adult↗

PubMed2000

Use of a dry-plasma collection device to overcome problems with storage and transportation of blood samples for epidemiology studies in developing countries.

Studies are difficult in areas lacking modern facilities due to the inability to reliably collect, store, and ship samples. Thus, we sought to evaluate the use of a dry plasma collection device for seroepidemiology studies. Plasma was obtained by fingerstick using a commercial dry plasma collection device (Chemcard Plasma Collection Device) and serum (venipuncture) from individuals in Kazakhstan. Plasma samples were air dried for 15 min and then stored desiccated in foil zip-lock pouches at 4 to 6 degrees C and subsequently shipped to the United States by air at ambient temperature. Serum samples remained frozen at -20 degrees C until assayed. Helicobacter pylori status was determined by enzyme-linked immunosorbent assay (HM-CAP EIA) for the dry plasma and the serum samples. The results were concordant in 250 of the 289 cases (86.5%). In 25 cases (8.6%), the dry plasma samples gave indeterminate results and could not be retested because only one sample was collected. Five serum samples were positive, and the corresponding dry plasma samples were negative; one serum sample was negative, and the corresponding plasma sample was positive. The relative sensitivity and specificity of the Chemcard samples to serum were 97.6 and 97.9%, respectively, excluding those with indeterminate results. Repeated freeze-thawing had no adverse effect on the accuracy of the test. We found the dry plasma collection device to provide an accurate and practical alternative to serum when venipuncture may be difficult or inconvenient and sample storage and handling present difficulties, especially for seroepidemiologic studies in rural areas or developing countries and where freeze-thawing may be unavoidable.

Blood Preservation↗

PubMed2000

Evidence from a nine-year birth cohort study in Japan of transmission pathways of Helicobacter pylori infection.

We examined the longitudinal changes of Helicobacter pylori infection within 46 families with children and 48 couples without children living in Japan. The study cohort was monitored from 1986 to 1994. H. pylori status was assessed by the presence of anti-H. pylori immunoglobulin G antibodies. At study entry, H. pylori prevalence in children with positive mothers was 23% versus 5% in children with negative mothers (odds ratio = 5.3; 95% confidence interval = 0.6 to 42.8). Seroconversion (rate of 1.5%/year) was evident only among children living with positive mothers and did not differ among adults living with or without children. These data strongly support the cluster phenomenon of H. pylori infection among families, the key role of the infected mothers in the transmission within families, and the importance of adult-child transmission and not vice versa.

Adult↗

PubMed2000

The gastric cardia in gastro-oesophageal disease.

BACKGROUND: There have been conflicting reports concerning the use of cardia biopsies in screening patients for gastro-oesophageal disease. AIM: To define the histopathological changes in the gastric cardia of patients with and without gastro-oesophageal disease. METHODS: Topographically mapped gastric biopsy specimens were obtained from patients with gastro-oesophageal disease and from controls. Biopsies were scored on a visual analogue scale of 0 to 5 for Helicobacter pylori, intestinal metaplasia, pancreatic metaplasia, foveolar hyperplasia, and active inflammation. The presence or absence of cardiac glands was recorded. RESULTS: Sixty-five patients with gastro-oesophageal disease and 71 controls were examined. Intestinal metaplasia was present in cardia biopsies of 10 patients with gastro-oesophageal disease and 11 controls. Only two patients with gastro-oesophageal disease and intestinal metaplasia in the cardia had no evidence of exposure to H pylori. Intestinal metaplasia was not found in the cardia of those with long segment Barrett's oesophagus. Carditis was strongly associated with active H pylori infection (p = 0.000) and resolved after treatment of the infection. A negative association was present between gastro-oesophageal disease and the presence of cardiac glands in cardiac biopsies (p = 0.003). Pancreatic metaplasia was found in 15 of 65 and foveolar hyperplasia in 19 of 65 cases but neither was related to gastro-oesophageal disease. CONCLUSION: Intestinal metaplasia in the cardia is uncommon in gastro-oesophageal disease in the absence of H pylori infection. With chronic H pylori infection the junction between the cardia and corpus expands in a cardia-corpal direction.

Adult↗

PubMed2000

Antibiotics as primary therapy for Crohn's disease.

Crohn's disease, an inflammatory bowel disease of unknown cause, was initially considered to have an infectious etiology. As the infectious agent could not be identified, it was grouped among the immune disorders. As a result, research and clinical trials were directed towards the autoimmune theory and patients were treated with steroids, immunomodulators, aminosalicylates and, most recently, anti-tumor necrosis factor-alpha. Because of the inconsistency of treatment success and the failure to cure Crohn's disease, many physicians turned to antibiotics in search for alternative solutions, especially when other regimens failed. Attention has recently been directed toward possible infectious causes of Crohn's disease. Although it is still unknown whether microbial agents are etiologically involved in the pathogenesis of Crohn's disease, there has been a growing interest in trying antibiotics in the management of Crohn's disease. This review summarizes the data available regarding antibiotic treatment of Crohn's disease in relation to a possible mycobacterial etiology. Multidrug therapies are in clinical trials and the results of these randomized, controlled, double-blind studies are needed before guidelines about whether to include antibiotics as part of the treatment of Crohn's disease management can be made.

Journal Article↗

PubMed2000

Clarithromycin for Helicobacter pylori infection.

Helicobacter pylori, a Gram-negative organism that survives in the deep mucus layer and attaches to the gastric surface cells, is estimated to be present in up to one-half of the US population. Chronic H. pylori infection causes chronic gastritis, peptic ulcer diseases and even gastric cancer. Cure of the infection leads to healing of gastric inflammation, prevention of development of peptic ulcer, as well as accelerated healing of peptic ulcers, and prevention of ulcer recurrence. Treatment of H. pylori has undergone substantial evolution over the past decade. Despite the in vitro susceptibility, results from single or even dual drug therapy is typically unsatisfactory and the best therapy is yet to be defined. The best current therapies for H. pylori infection consist of a proton pump inhibitor (PPI) or ranitidine bismuth citrate and two antibiotics (triple therapies), or bismuth, tetracycline, metronidazole and a PPI (quadruple therapy). Clarithromycin is one of the most useful antimicrobials against H. pylori. It is an acid-stable macrolide with a broad spectrum of antibacterial activity, well absorbed with a wide tissue distribution and with mild side effects. Clarithromycin has a low minimum inhibitory concentration (MIC50) for H. pylori and its effect is potentiated by acid inhibition. When combined with a PPI or ranitidine bismuth citrate and amoxicillin or metronidazole, eradication rates of more than 95% can be achieved with susceptible organisms. However, the prevalence of primary and acquired clarithromycin resistance, which is due to mutations within a conserved loop of 23S rRNA of H. pylori, is increasing. In practice, the presence of clarithromycin resistance usually implies reduced success when clarithromycin-containing regimes are used. There is a need for improved therapies for H. pylori where antibiotic resistance is less of a problem.

Anti-Bacterial Agents↗

PubMed2000

Strategy for treatment of Helicobacter pylori infection in adults. II. Practical policy in 2000.

The approach to the patient with suspected H. pylori infection consists of an adequate indication to test for the presence of the infection, choice of an appropriate antimicrobial regimen, and education about its use and side effects, followed by post-therapy testing to confirm cure. We review the drugs and regimens for H. pylori eradication and present a strategy for treating the infection. The major factor in choosing an antibiotic regimen is the pattern of antibiotic resistance in the community. Triple therapy with a proton pump inhibitor (PPI) or ranitidine bismuth citrate (RBC) and two antimicrobials is recommended as the first choice regimen. In regions where metronidazole and clarithromycin resistance are common, initial therapy with quadruple therapy consisting of bismuth, metronidazole, tetracycline, and a PPI is recommended. In general, higher doses and longer durations are associated with better outcomes. For this reason we recommend that the minimum duration of 10 days and we prefer 14 days. The actual choice of the antimicrobial combination will also be influenced by the drugs approved by the local regulatory bodies. Side effects, eradication failure and current as well as future designs of eradication therapies are also discussed.

Amoxicillin↗

PubMed2000

Antibiotic-resistant H. pylori infection and its treatment.

Helicobacter pylori infection causes progressive damage to gastric mucosa and results in serious disease such as peptic ulcer disease, MALT lymphoma, or gastric adenocarcinoma in 20% to 30% of patients. The current approach is to make a firm diagnosis, give combination antibiotic and antisecretory therapy, and confirm that the infection has been cured 4 to 6 weeks later. Antimicrobial resistance is largely responsible for treatment failures. Resistance to metronidazole can frequently be overcome by increasing the dose and duration of treatment with acid suppression. Clarithromycin is the most effective antibiotic against H. pylori but, unfortunately, resistance to it is increasing and can not be overcome by increasing the dose or duration of therapy with clarithromycin. The choice of therapy should be based on local susceptibility patterns. Re-treatment regimens for treatment failure should exclude antibiotics where acquired resistance is expected (i.e., clarithromycin and possibly metronidazole). Where available, treatment failure should prompt endoscopy and culture and susceptibility testing. Overall, higher doses and longer durations of treatment result in the best cure rates. When multiple treatment regimens fail, salvage therapy regimens such as bismuth or furazolidone quadruple therapy (a bismuth and tetracycline HCl 4 times a day along with a proton pump inhibitor twice a day, and either metronidazole 400 or 500 mg three times daily or furazolidone 100 mg three times daily for 14 days) can be used. Newer agents are needed to cope with the increasing prevalence of antibiotic resistance among H. pylori.

Drug Resistance, Microbial↗

PubMed2000

Strategy for treatment of Helicobacter pylori infection in adults. I. Updated indications for test and eradication therapy suggested in 2000.

Since the report of culture of Helicobacter pylori in 1983, there has been increasing agreement that H. pylori infection is etiologically associated with a number of important diseases including chronic active gastritis, peptic ulcer disease, mucosa-associated lymphoid tissue (MALT) lymphoma, gastric polyps, gastric cancer, as well as suggestions that it may be involved in diseases outside the upper gastrointestinal tract. There have been a number of national and international consensus meetings to propose guidelines to treat H. pylori infection. The recommendations of these conferences are reviewed here and updated to include new indications and concepts regarding H. pylori eradication therapy. Eradication therapy is considered the standard of care for active or inactive peptic ulcer patients including those who use non-steroidal anti-inflammatory drugs (NSAIDs). Other strong indications include MALT lymphoma, hyperplastic polyps, hyperplastic gastropathy, post-endoscopic resection for gastric malignancy, and acute H. pylori gastritis. Other considerations include plan to use chronic NSAID therapy, plan for chronic anti-secretory therapy, and some extra-gastroduodenal diseases such as chronic ureterica. Non-investigated dyspepsia is an indication for diagnostic evaluation and eradication therapy for those with H. pylori infection, whereas non-ulcer dyspepsia (NUD) in which peptic ulcer disease has been excluded is not an indication for evaluation per se. Intervention studies are now in progress to test the hypothesis that prevention of gastric malignancy is an outcome of H. pylori eradication. Because the prevalence of H. pylori infection and the associated diseases such as peptic ulcer or gastric cancer differ among countries as well as different approvals for treatment are required by governments or insurance agencies, the acceptable indications of eradication therapy will, by necessity, vary among countries.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2000

Quantitative and bioluminescent assay to measure efficacy of conventional and DNA vaccinations against Helicobacter pylori.

Vaccination against Helicobacter pylori using DNA sequences encoding Urease A and B subunits was compared to immunization with urease antigen and MTP-PE in a liposome formulation. To determine the effectiveness of a vaccine against H. pylori in a mouse model it is essential to quantify the number of H. pylori remaining in the stomachs following challenge with an inoculum of live bacteria. Culture assays and enzymatic assays produce inconsistent results often unsuitable to conclude if vaccine candidates are protective. To overcome this problem, we developed two assays: 1) a competitive quantitative PCR using a colorimetric readout and 2) a non-competitive direct quantitative PCR using a highly sensitive bioluminescent readout. The competitive PCR requires coamplification of a segment of the urease C sequence and an internal control standard in a competitive manner using a single set of primers. PCR products were quantified colorimetrically by an enzyme-linked immunosorbent assay and compared with known quantities of the internal control standard added to the PCR reaction. The highly sensitive, bioluminescent assay measures the amplified DNA directly using a flash-type luminescent tag and a specific probe. The Sydney strain of H. pylori was used for the mouse infection model. Quantification of H. pylori by either the bioluminescent assay or the competitive PCR was reliable, specific and sensitive compared to quantitative growth assays which often gave false results. The bioluminescent assay was much more sensitive and less labor/time intensive than the competitive PCR. The bioluminescent assay was able to quantitate as few as 100 bacteria, while the competitive assay could not detect less than 10(3) bacteria per mouse stomach. Quantification of H. pylori by bioluminescent assay was superior to the competitive assay and may be used for research applications, such as the development of vaccines, pathogenesis of gastric disease and monitoring of antibiotic treatment.

Animals↗