Effect of omeprazole therapy on the survival of Helicobacter pylori, urease activity, and antral gastric histology in patients with duodenal ulcer

Phospholipase C: underrated players in microbial infections

During bacterial infections, one or more virulence factors are required to support the survival, growth, and colonization of the pathogen within the host, leading to the symptomatic characteristic of the disease. The outcome of bacterial infections is determined by several factors from both host as well as pathogen origin. Proteins and enzymes involved in cellular signaling are important players in determining the outcome of host-pathogen interactions. phospholipase C (PLCs) participate in cellular signaling and regulation by virtue of their ability to hydrolyze membrane phospholipids into di-acyl-glycerol (DAG) and inositol triphosphate (IP3), which further causes the activation of other signaling pathways involved in various processes, including immune response. A total of 13 PLC isoforms are known so far, differing in their structure, regulation, and tissue-specific distribution. Different PLC isoforms have been implicated in various diseases, including cancer and infectious diseases; however, their roles in infectious diseases are not clearly understood. Many studies have suggested the prominent roles of both host and pathogen-derived PLCs during infections. PLCs have also been shown to contribute towards disease pathogenesis and the onset of disease symptoms. In this review, we have discussed the contribution of PLCs as a determinant of the outcome of host-pathogen interaction and pathogenesis during bacterial infections of human importance.

Evaluation of pharmacokinetic interactions between amoxicillin, clarithromycin, and the potassium-competitive acid blocker YH4808 in healthy subjects

YH4808 is a novel potassium-competitive acid blocker that was developed as a therapeutic agent for gastric acid-related diseases; it may replace proton pump inhibitors, which are widely used in combination with amoxicillin and clarithromycin for Helicobacter pylori eradication. We compared the pharmacokinetic (PK) profiles and safety of amoxicillin, clarithromycin, and YH4808 used as monotherapies or in combination for evaluating potential drug interactions. An open-label, randomized, single-dose, Latin-square (4 × 4) crossover study was conducted in 32 healthy Korean volunteers. Subjects were randomly assigned to one of the 4 treatment sequences that consisted of 4 periods separated by 21-day washout intervals. PK parameters of YH4808, amoxicillin and clarithromycin administered in combination were compared with those of the respective monotherapies. The geometric mean ratios of the maximum concentration (C_max) and the area under the time-concentration curve from time zero to time of the last quantifiable concentration (AUC_last) of YH4808 increased during the triple therapy by 48.6% and 29.1%, respectively. Similarly, the C_max and AUC_last of M3 (active metabolite of YH4808) increased by 23.3% and 16.0%, respectively. The C_max and AUC_last of clarithromycin increased by 27.4% and 30.5%, and those of 14-hydroxyclarithromycin were increased by 23.1% and 32.4%, respectively. The corresponding amoxicillin values decreased during the triple therapy by 21.5% and 15.6%, respectively. There was no clinically significant change in safety assessment related to either monotherapies or triple therapy. In conclusion, amoxicillin, clarithromycin and YH4808 administered as triple therapy did not exhibit significant PK interactions and were not associated with safety issues.

Influence of proton pump inhibitors on gastritis diagnosis and pathologic gastric changes

AIM: To investigate the influence of proton pump inhibitors (PPIs) exposure on the diagnosis of Helicobacter pylori (H. pylori) gastritis and intestinal metaplasia.

METHODS: Chronic PPI use is associated with masking of H. pylori infection. Patients with H. pylori infection are predisposed to gastric and duodenal ulcers, and long-term infection with this organism has been associated with gastric mucosal atrophy and serious long-term complications, such as gastric lymphoma and adenocarcinoma. Three hundred patients diagnosed with gastritis between January 2008 and April 2010 were included in our study. The computerized medical database of these patients was reviewed retrospectively in order to assess whether the type of gastritis diagnosed (H. pylori vs non-H. pylori gastritis) is influenced by PPI exposure. H. pylori density was graded as low, if corresponding to mild density following the Updated Sydney System, or high, if corresponding to moderate or severe densities in the Updated Sydney System.

RESULTS: Patients were equally distributed between males and females with a median age at the time of diagnosis of 50 years old (range: 20-87). The histological types of gastritis were classified as H. pylori gastritis (n = 156, 52%) and non-H. pylori gastritis (n = 144, 48%). All patients with non-H. pylori gastritis had inactive chronic gastritis. Patients with no previous PPI exposure were more likely to be diagnosed with H. pylori gastritis than those with previous PPI exposure (71% vs 34.2%, P < 0.001). Intestinal metaplasia was more likely to be detected in the latter patients (1.4% vs 6.5%, P = 0.023). Multivariate analysis has also demonstrated that in the presence of previous PPI exposure (OR = 0.217, 95%CI: 0.123-0.385), GERD (OR = 0.317, 95%CI: 0.132-0.763, P = 0.01), alcohol intake (OR = 0.396, 95%CI: 0.195-0.804, P = 0.01), the detection of H. pylori was less likely. Chronic use of PPIs may mask H. pylori infections promoting the diagnosis of non-H. pylori gastritis and leads to a significant drop in H. pylori densities and to an increased risk of intestinal metaplasia.

CONCLUSION: The use of PPIs masks H. pylori infection, promotes the diagnosis of non-H. pylori inactive chronic gastritis diagnosis, and increases the incidence of intestinal metaplasia.

Gastric juice for the diagnosis of H pylori infection in patients on proton pump inhibitors

AIM: To determine the efficacy of gastric juice polymerase chain reaction (PCR) for the detection of H pylori infection in comparison with histology and gastric antral biopsy PCR in patients on a proton pump inhibitor (PPI).

METHODS: Eighty-five consecutive patients with dyspeptic symptoms were enrolled. Gastric biopsies for histology, PCR and gastric juice were collected at endoscopy for PCR of the H pylori urease C gene (ure C). Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, positive and negative likelihood ratio for PCR of gastric juice for the H pylori ure C gene was compared to histology and gastric antral biopsy H pylori ure C PCR in patients with and without PPI.

RESULTS: Gastric juice PCR was positive in 66 (78%) patients. Histology showed H pylori associated gastritis in 57 (67%). Gastric biopsy PCR was positive in 72 (85%). In patients not taking PPI, the sensitivity, specificity, PPV, NPV, accuracy and positive and negative likelihood ratio for gastric juice PCR were 89%, 72%, 91%, 67%, 90%, 85%, 3.1 and 0.1 respectively. In patients on PPI these values were 86%, 100%%, 100%, 29%, 86%, 9.5 and 1.4, respectively.

CONCLUSION: Gastric juice PCR for the diagnosis of H pylori infection has increased sensitivity compared to histology with PPI. The use of gastric juice PCR is recommended to confirm H pylori status in patients taking PPIs.

N/A

N/A

False negative urea breath tests with H2-receptor antagonists: interactions between Helicobacter pylori density and pH

BACKGROUND

We studied the effects of famotidine, sodium bicarbonate, and citric acid on the 13C-urea breath test (UBT).

METHODS

Helicobacter pylori-infected volunteers received a UBT, 40 mg of famotidine at bedtime, and a second UBT (pudding test meal, 648 mg NaHCO3 tablet then 125 mg of urea in 200 ml of water containing 650 mg of NaHCO3). Experiment 2 consisted of four UBTs. Two were standard citric acid UBTs with 75 mg of urea and 2 g citric acid and two were sequential bicarbonate-citric acid UBTs. Sequential UBTs consisted of administration of a 648 mg bicarbonate tablet with 50 g of Polycose in 200 ml of water. Five minutes later, 125 mg of 13C-urea was given in 75 ml of water containing 650 mg of NaHCO3. Breath samples were collected after 15 minutes. Then, to acutely acidify the stomach, 4 g of citric acid was given in 200 ml of water. A second breath sample was collected 15 minutes after the citric acid. The standard UBTs were done before and after 6 days of famotidine (40 mg b.i.d.). Sequential UBTs were done after 1 and 6 days of famotidine therapy. Gastric biopsies for histology, culture, and mucosal cytokines were assessed before and after 6 days of famotidine.

RESULTS

Eighteen subjects participated, 10 in each experiment; seven had endoscopy with biopsy. Famotidine/ bicarbonate resulted an approximately 50% fall in UBT values (p = .021) with 10% becoming negative. The gastric pH increased from 5.1 +/- 0.5 to 6.7 +/- 0.2 (p = .03) although no pH value predicted the occurrence of false negative results. Under famotidine acid suppression, NaHCO3 reduced the delta over baseline (DOB) by 63% (p = .021). This was reversed with citric acid. Histology showed a H2-receptor antagonist-associated increase in the depth of gastric corpus inflammation.

CONCLUSIONS

H2-receptor antagonists differ from proton pump inhibitors as high intragastric pH may cause a reduction in urease activity, unrelated to a reduced bacterial load and reversed by citric acid.

Studies regarding the mechanism of false negative urea breath tests with proton pump inhibitors

OBJECTIVE

The mechanism of false negative urea breath tests (UBTs) results among proton pump inhibitor (PPI) users is unknown. We studied the time course of PPI-associated negative UBT, the relation to Helicobacter pylori density, and whether gastric acidification would prevent false negative UBT results.

METHOD

In the UBT experiment, H. pylori-infected volunteers received omeprazole 20 mg b.i.d. for 13.5 days. UBTs with citric acid were done before, after 6.5 days of PPI, and 1, 2, 4, 7, and 14 days after therapy. In the culture and histology experiment, after a wash-out of >5 months, nine of the original subjects were rechallenged with omeprazole for 6.5 days. Antral and corpus biopsies for histology and culture were done before and 1 day after PPI administration.

RESULTS

Thirty subjects (mean age 42 yr) were enrolled. UBTs were significantly reduced on day 6.5 (p = 0.031); 10 subjects (33%) developed transient negative UBTs. The UBT recovered in all but one subject by the fourth day post-PPI and in all subjects by day 14. In the culture and histology experiment, upon PPI rechallenge, three of nine subjects (33%) had negative UBTs. H. pylori density, whether measured by culture or histology, decreased with PPI therapy; antral biopsies became histologically negative in five subjects and corpus biopsies in three subjects.

CONCLUSION

PPI-induced negative UBT results were related to the anti-H. pylori effect of the PPI. Acidification of the stomach did not prevent false negative UBT results. Three days is likely the minimum delay from stopping PPI until one should perform a test for active infection. A delay of 14 days is preferred.

A randomized, double-blind trial of the efficacy and safety of 10 or 20 mg rabeprazole compared with 20 mg omeprazole in the maintenance of gastro-oesophageal reflux disease over 5 years

BACKGROUND

Gastro-oesophageal reflux disease has a chronic course, and often requires long-term treatment. Proton pump inhibitors are the treatment of choice for both acute and maintenance treatment, but little is known from randomized controlled trials of their effects beyond 1 year.

AIM

To compare the efficacy and safety of two doses of rabeprazole with 20 mg omeprazole in the maintenance treatment of erosive gastro-oesophageal reflux disease over 5 years.

METHODS

Two hundred and forty-three patients who had previously responded to acute treatment for erosive gastro-oesophageal reflux disease were prospectively randomized to receive 5 years of treatment with rabeprazole (10 or 20 mg daily) or omeprazole (20 mg daily). The primary outcome measure was endoscopically confirmed relapse of erosive gastro-oesophageal reflux disease.

RESULTS

One hundred and twenty-three patients (51%) completed all 5 years of the study, with similar completion rates in the three groups. Relapses occurred in nine of 78 (11.5%), eight of 82 (9.8%) and 11 of 83 (13.3%) patients in the rabeprazole 20 mg, rabeprazole 10 mg and omeprazole 20 mg groups, respectively. Gastric biopsy showed no evidence of any harmful effects. All treatments were well tolerated.

CONCLUSIONS

Rabeprazole 10 mg, rabeprazole 20 mg and omeprazole 20 mg all had similar efficacy in the maintenance treatment of gastro-oesophageal reflux disease. All three were safe and well tolerated during 5 years of treatment.

Colonisation density and topographic localisation of Helicobacter pylori do not depend on the cagA status

AIMS

To explore the correlation between the cagA status of Helicobacter pylori and the density and topographic localisation of H pylori.

METHODS

Gastric antral biopsy specimens were taken from 716 consecutive patients, including 293 H pylori positive patients (124 men, 169 women; mean age, 52.6 years; range, 12-87). A serum sample was taken for determination of IgG anti-CagA antibodies (sensitivity of 94.4% and specificity of 92.5%). The density of H pylori was assessed semiquantitatively (grades I-IV) in biopsy specimens stained with the modified Giemsa stain. Topographic localisation was classified as follows: score A, H pylori closely attached to the mucosa; score B, H pylori attached to the mucosa and in the mucus; and score C, H pylori solely in the mucus.

RESULTS

CagA antibodies were present in 154 (52.5%) of the patients. There was no significant difference in colonisation density and cagA status: grade I, 23 (14%); grade II, 78 (50.6%); grade III, 42 (27.5%); and grade IV, 11 (7.2%) in the cagA(+) strains and 29 (21.2%), 57 (40.8%), 38 (27%), and 15 (11%), respectively, in the cagA(-) strains. There was no difference in topographic localisation between cagA(+) and cagA(-)H pylori. Mean anti-CagA titres were 0.84, 0.84, 0.89, and 0.73 in patients with grades I-IV bacterial density, respectively.

CONCLUSION

Antibody titres do not correlate with H pylori density and there is no difference in density between cagA(+) and cagA(-)H pylori strains. In addition there is no difference in topographic localisation between cagA(+) and cagA(-) H pylori strains.