Biomedical subjects

M S Osato

Publications and source records attributed to M S Osato.

At least 37 records · Page 2Linked to original sources

PubMed2000

Molecular epidemiology of Helicobacter pylori: separation of H. pylori from East Asian and non-Asian countries.

The predominant H. pylori strain circulating among geographic locations differs with regard to the genomic structure. This study determined whether structural subtypes of the cagA 3' repeat region could be used to identify the population of origin of H. pylori isolates. We examined 600 cagA-positive H. pylori (Colombia, 100; USA, 100; France, 100; Canada, 20; Italy, 20; Korea, 100; Japan, 100; Hong Kong, 20; Taiwan, 20; Vietnam, 20). The cagA 3' region was amplified by PCR using primers specific to Japanese and Western 3' cagA gene sequences. PCR using Japanese cagA primers resulted in PCR products in 99-6 % of strains from East Asia but no non-Asian strains. Conversely, PCR using Western cagA primers resulted in amplicons in 100% of non-Asian strains, and only one from East Asia. cagA genotyping is useful for molecular epidemiological studies as strains can be completely separated by differences in the cagA 3' region.

Adult↗

PubMed2000

Furazolidone combination therapies for Helicobacter pylori infection in the United States.

BACKGROUND: Antibiotic resistance has begun to impair the ability to cure Helicobacter pylori infection. AIM: To evaluate furazolidone as a component of combination therapies for treatment of H. pylori infection in the United States. METHODS: Patients with active H. pylori infection received furazolidone combination therapy for 14 days (furazolidone 100 mg and tetracycline 500 mg t.d.s.; omeprazole 20 mg o.d. in the morning and, depending on the pre-treatment antimicrobial susceptibility pattern, 500 mg of metronidazole or clarithromycin t.d.s.). RESULTS: A total of 27 patients received the metronidazole containing combination (cure rate 100%) and seven received the clarithromycin combination (cure rate 86%). Overall the cure rates for intention-to-treat was 97% (95% CI: 85% to 100%). The single failure took the clarithromycin containing combination for only 2 days (per protocol cure rate = 100%). Side-effects were common and led to discontinuation of therapy in 26% of patients. An attempt to eliminate metronidazole and clarithromycin and use furazolidone, tetracycline, and lansoprazole b.d. produced an unsatisfactory cure rate of 72%. CONCLUSION: Furazolidone combination therapy appears to be effective. Additional studies with different antimicrobial combinations and duration of therapy are warranted.

Anti-Ulcer Agents↗

PubMed2000

Metronidazole containing quadruple therapy for infection with metronidazole resistant Helicobacter pylori: a prospective study.

BACKGROUND: Metronidazole remains a key component of H. pylori infection therapy. It has been suggested that despite resistance, metronidazole may be effective when given at high dose with bismuth, tetracycline, and a proton pump inhibitor (quadruple therapy). AIM: To prospectively evaluate metronidazole quadruple therapy for treatment of metronidazole resistant H. pylori infection in the United States. METHODS: Patients infected with metronidazole resistant H. pylori were prospectively prescribed 14 days of quadruple therapy consisting of metronidazole 500 mg t.d.s., tetracycline 500 mg q.d.s., two bismuth subsalicylate tablets q.d.s., and omeprazole 20 mg o.d. RESULTS: A total of 26 patients were entered into the study; 22 for their first treatment and four as re-treatment for failed therapy. Of the 26 patients, 24 were cured (cure rate 92%; 95% CI: 78-99%). Both treatment failures reported full compliance to 14 days of therapy. Side-effects were common and resulted in premature discontinuation of therapy in 31%. Premature discontinuation did not reduce the cure rate. CONCLUSION: Quadruple metronidazole combination therapy is effective despite the presence of metronidazole resistance and should be considered as either first line therapy or for failures of twice-a-day combination therapies.

Aged↗

PubMed2000

Characterization of a culture method to recover Helicobacter pylori from the feces of infected patients.

BACKGROUND: Helicobacter pylori is difficult to culture from stool. Multiple efforts from multiple laboratories have been unsuccessful, and the optimal conditions to recover H. pylori from stool are still not known. Recovery of H. pylori from feces of infected individuals is important for the performance of molecular epidemiological investigations, especially in children, where their symptoms do not warrant endoscopy to recover the organism. METHODS: Fresh fecal specimens (noncathartic) were obtained from 19 known H. pylori-infected patients and were processed to recover the organism. Fresh fecal specimens (noncathartic) were also obtained from three known H. pylori-negative individuals (controls) to determine whether H. pylori could be isolated from stools seeded with known concentrations of the organism. Treatment of the fecal suspensions with cholestyramine, a basic anion exchange resin that binds bile acids, was used in an attempt to enhance recovery of H. pylori by sequestering bile acids that are inhibitory to H. pylori growth. H. pylori was identified based on colony morphology, cell morphology, Gram's stain, biochemical reactions, and polymerase chain reaction for two H. pylori genes. RESULTS: Among 19 patients, H. pylori was cultured at least once from 3 and three times from 2 (5 of 19). Feces that were seeded with H. pylori and obtained from three H. pylori-negative volunteer controls yielded positive recovery in all instances. CONCLUSION: We have confirmed that it is possible to culture H. pylori from human stool, but the procedure for optimal recovery has still not been defined.

Bacteriological Techniques↗

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

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

Antimicrobial susceptibility testing for Helicobacter pylori: sensitivity test results and their clinical relevance.

There are multiple test methodologies to determine the antibiogram of an organism. Standardized susceptibility test methods are based upon rapidly growing, aerobic microorganisms in which overnight incubation results in definitive endpoints. In vitro susceptibility testing for fastidious organisms that require complex media for growth, require incubation in atmospheres other than ambient air, or are slow-growing (anaerobes, mycobacteria, filamentous fungi) are problematic and in general are not standardized. H. pylori falls into this category of troublesome organisms. For the microaerobic organism H. pylori, testing is challenging because the organism grows slowly even under optimal culture conditions. Recently the National Committee for Clinical Laboratory Standards (NCCLS) approved the agar dilution method as the test of choice for testing H. pylori. While not entirely reliable in predicting the outcome of treatment for metronidazole resistant organisms, the resistance determined for clarithromycin by this method generally predicts treatment failure. Quality control breakpoints for H. pylori ATCC 43504 were established and breakpoints for clarithromycin were approved by the NCCLS in 1999. Breakpoints are minimum inhibitory concentrations (MIC) of a drug at which an organism is deemed either susceptible or resistant to the antibiotic using standard dosing regimens containing that drug. Significant progress has been made with respect to development of tests to detect antimicrobial resistance, but there still remains no consensus as to the breakpoints for agents used in the treatment of H. pylori infection other than clarithromycin. This article will address the controversies associated with the reporting of antibiotic resistance data and the interpretation of these data.

Cost-Benefit Analysis↗

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↗

PubMed1999

Helicobacter pylori in sheep milk.

Helicobacter pylori was recovered from sheep milk, suggesting a role for animals in transmission. H. pylori may be a commensal in the sheep, which may be H. pylori's ancestral host.

Animals↗

PubMed1999

Influence of endoscopic biopsy forceps characteristics on tissue specimens: results of a prospective randomized study.

BACKGROUND: A large variety of endoscopic biopsy forceps are commercially available. However, little is known regarding the influence of forceps characteristics such as disposability, size, shape, and presence of a needle on the adequacy of the specimens for histologic diagnosis. Our aim was to analyze in a prospective, randomized, pathologist-blinded study the performance of different biopsy forceps. METHODS: Twelve biopsy forceps were tested, 6 each at upper endoscopy and colonoscopy. Two biopsy specimens were obtained with each forceps, for a total of 12 specimens per patient. The tissue samples were examined for the following parameters: weight (mg), size (mm3), depth, crush artifact, sheering effect, and adequacy of the specimens for histologic information (0 = inadequate, 1 = suboptimal, and 2 = adequate). RESULTS: Fifty-five patients undergoing routine upper or lower gastrointestinal endoscopy were included in the study, and a total of 624 tissue samples were available for analysis. Overall, disposable forceps provided specimens of greater size and depth. At upper endoscopy, alligator-shaped forceps improved the depth of the sample as did the absence of a needle within the cup. These factors, however, had no impact on the specimens obtained at colonoscopy. When the adequacy of the specimens was assessed for histologic diagnosis, no significant difference was noted between any of the individual forceps, although collectively oval-shaped forceps were superior to alligator-shaped forceps at colonoscopy. CONCLUSIONS: The biopsy forceps currently available in the market are equally efficient in providing histologic diagnosis. The primary consideration when selecting an endoscopic biopsy forceps, therefore, should be the cost and ease of use and not any perceived advantage in performance.

Adult↗

PubMed1999

Metronidazole and clarithromycin resistance amongst Helicobacter pylori isolates from a large metropolitan hospital in the United States.

BACKGROUND: Metronidazole and clarithromycin-based therapies are among the most efficacious treatment regimens for H. pylori infection. Resistance to metronidazole or clarithromycin is associated with impaired therapy with these agents. We conducted a retrospective review of susceptibility data to determine the frequency of primary metronidazole and clarithromycin resistance among H. pylori isolates from a single metropolitan hospital in the United States. The database comprised 933 patients who presented at the Digestive Diseases Clinic at the Veterans Affairs Medical Center in Houston between September 1988 and January 1997 with complaints of dyspepsia, abdominal pain and peptic ulcer disease. One hundred and seventy-nine of these patients had both pharmaceutical records available for evaluation and culture and antimicrobial susceptibility data for analysis. The MICs were determined by both E-test and broth microdilution tests. The frequency of primary metronidazole resistance was 37.4% (67/179). The level of primary clarithromycin resistance was 6.1%. Dual metronidazole and clarithromycin resistance was present in approx. 3%. The high level of primary metronidazole and clarithromycin resistance in H. pylori isolates from this metropolitan hospital is such that antimicrobial susceptibility data should be available so that informed choice can be made for specific eradication therapies, especially in patients who fail treatment.

Anti-Bacterial Agents↗

PubMed1999

Osmotic effect of honey on growth and viability of Helicobacter pylori.

Honey from New Zealand and Saudi Arabia at concentrations approximating 20% (v/v) inhibit the growth of H. pylori in vitro. The anti-H. pylori effect involves both hydrogen peroxide- and non-peroxide-mediated killing mechanisms. This study was designed to determine whether the anti-H. pylori activity of honey differed regionally (honey from Texas, Iowa, and New Zealand) and to determine whether this activity was due to the presence of hydrogen peroxide. Broth dilution susceptibility tests were performed using solutions of honey prepared in BHI broth ranging in concentration from 5 to 35% (v/v) in 5% increments. Control solutions containing glucose, fructose, and combined glucose/fructose solutions in ratios of 1:1.23 were also prepared. Paired catalase controls were included in all tests. Twenty-eight clinical isolates of H. pylori were tested. Growth was determined on the basis of a plus/minus grading score. All of the solutions containing either fructose, glucose, glucose and fructose combinations, or honey were equally effective in inhibiting the growth of H. pylori. All of the isolates were inhibited by solutions containing 15% (w/v) carbohydrate. Honey solutions, with or without catalase, inhibited 24/28 isolates at a concentration of 10%, and 28/28 isolates at a concentration of 15%. In conclusion, regional differences in honey activity against H. pylori were not detected, nor was the effect of killing related to the presence of hydrogen peroxide in the honey samples. Osmotic effects were shown to be the most important parameter for killing H. pylori as all carbohydrate solutions > or = 15% (v/v) inhibited 100% of the H. pylori.

Anti-Infective Agents, Local↗

PubMed1999

Novel therapies for Helicobacter pylori infection.

BACKGROUND: Increasing antibiotic resistance has begun to impair our ability to cure Helicobacter pylori infection. AIM: To evaluate orally administered novel therapies for the treatment of H. pylori infection. METHODS: Healthy H. pylori infected volunteers received: (a) hyperimmune bovine colostral immune globulins, (b) an oligosaccharide containing an H. pylori adhesion target, Neu5Aca2-3Galb1-4Glc-(3'-sialyllactose), or (c) recombinant human lactoferrin. Outcome was assessed by urea breath test or histological assessment of the number of H. pylori present. RESULTS: None of the novel therapies appeared effective and no adverse events occurred. CONCLUSION: Although in vitro data appeared promising, in vivo results were disappointing. Higher doses, longer duration of therapy, adjunctive acid suppression, or a combination could possibly yield better results.

Adjuvants, Immunologic↗