Evaluation of the string test for the detection of Helicobacter pylori

Aim: Helicobacter pylori can be diagnosed by invasive or non-invasive tests but to obtain bacteria for culture and antibiotic susceptibility testing, an upper GI endoscopy is often required. The string test may be a minimally-invasive alternative method of obtaining H. pylori samples. This study evaluates the sensitivity and specificity of the string test in the diagnosis of H. pylori in comparison with endoscopic means of diagnosis. Methods: This was a prospective open comparative study of patients with dyspepsia with endoscopy-based tests as gold standard (defined as a positive CLO test and antral histology). Fasting patients swallowed the encapsulated-string (Entero-test Hp), which was withdrawn after 1 hour. The gastric juice from the string was plated onto H. pylori-selective media for culture. Helicobacter pylori was identified by typical colony morphology, gram stain and biochemical test results. Results: Thirty dyspeptic patients were recruited of whom 21 (70 %) were positive for H. pylori according to the gold standard. The sensitivity, specificity, positive predictive value, and negative predictive value for the string test were 38 %, 100 %, 100 % and 41 % respectively, and for endoscopic biopsies 81 %, 100 %, 100 %, 69 % respectively (P=0.004). Logistic regression showed that only abundant growth density from endoscopic biopsy cultures to be a predictor of a positive string test (P=0.018). Conclusion: The string test is an alternative method to endoscopy in obtaining H. pylori but has a low sensitivity compared to endoscopic biopsies.published_or_final_versio

Tie-2 regulates the stemness and metastatic properties of prostate cancer cells.

Ample evidence supports that prostate tumor metastasis originates from a rare population of cancer cells, known as cancer stem cells (CSCs). Unfortunately, little is known about the identity of these cells, making it difficult to target the metastatic prostate tumor. Here, for the first time, we report the identification of a rare population of prostate cancer cells that express the Tie-2 protein. We found that this Tie-2High population exists mainly in prostate cancer cell lines that are capable of metastasizing to the bone. These cells not only express a higher level of CSC markers but also demonstrate enhanced resistance to the chemotherapeutic drug Cabazitaxel. In addition, knockdown of the expression of the Tie-2 ligand angiopoietin (Ang-1) led to suppression of CSC markers, suggesting that the Ang-1/Tie-2 signaling pathway functions as an autocrine loop for the maintenance of prostate CSCs. More importantly, we found that Tie-2High prostate cancer cells are more adhesive than the Tie-2Low population to both osteoblasts and endothelial cells. Moreover, only the Tie-2High, but not the Tie-2Low cells developed tumor metastasis in vivo when injected at a low number. Taken together, our data suggest that Tie-2 may play an important role during the development of prostate tumor metastasis.published_or_final_versio

Does the use of chopsticks for eating transmit Helicobacter pylori? [4]

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Use of chopsticks for eating and Helicobacter priori infection

Epidemiological data suggests that ethnic groups using chopsticks for eating have a higher prevalence of H. pylori infection. This study investigated the carriage of H. pylori in chopsticks after eating. Used chopsticks and saliva were collected from asymptomatic individuals whose H. pylori status was determined by [ 13C]urea breath test and serology. Both the saliva specimens and chopsticks were cultured and processed by polymerase chain reaction (PCR) for the detection of H. pylori. Furthermore, chopsticks used by hospital staff in the cafeteria were pooled for the detection of H. pylori by bacteriologic culture and PCR. Sixty-nine volunteers were recruited in the first study and 45 (65%) were diagnosed to have H. pylori infection. While all cultures were negative, H. pylori was detected by PCR in the saliva from 15 (33%) infected subjects and in the chopsticks from one (2%). Among the 12 sets of pooled chopstick-washing studied, H. pylori was detected by PCR in two sets. This study showed that H. pylori was rarely detected in chopsticks after eating and hence, the risk of contracting this infection via the use of chopsticks is low.link_to_subscribed_fulltex

False-negative biopsy urease test in bleeding ulcers caused by the buffering effects of blood

Objectives: A false-negative biopsy urease test (BUT) is common in Helicobacter pylori-associated bleeding peptic ulcers. Although blood in the stomach is thought to interfere with the biopsy urease test, the underlying mechanism remains unknown. This in vitro experiment sought to identify the blood component(s) that interfere with the biopsy urease test, and delineate the mechanism of inhibition. Methods: The modified Hazell's microtiter test was used to detect the urease activity of H. pylori. A positive result was indicated by a color change of the pH indicator, bromothymol blue, at 630 μm. Human whole blood, sera with and without anti-H. pylori antibody, electrolytes, and enzymes were incubated with H. pylori to identify the blood component(s) causing the inhibition of urease activity. In addition, any interference of the pH color indicator was tested by adding different concentrations of serum albumin to the urease reagent that contained a fixed quantity of ammonia in the absence of H. pylori. Results: The color change of the microtiter urease test was significantly reduced by blood (p < 0.0001), regardless of the presence of anti-H. pylori antibody. Electrolytes and serum enzymes did not interfere with the urease test. The color change of the pH indicator was progressively suppressed by higher concentrations of serum albumin. Conclusions: Blood adversely affects the performance of the BUT. This is mediated by the buffering effect of serum albumin on the pH indicator, rather than by a direct inhibition on the urease activity.link_to_subscribed_fulltex

Molecular interaction of flagellar export chaperone FliS and cochaperone HP1076 in Helicobacter pylori

Flagellar export chaperone FliS prevents premature polymerization of flagellins and is critical for flagellar assembly and bacterial colonization. Previously, a yeast 2-hybrid study identified various FliS-associated proteins in Helicobacter pylori, but the implications of these interactions are not known. Here we demonstrate the biophysical interaction of FliS (HP0753) and the uncharacterized protein HP1076 from H. pylori. HP1076 possesses a cochaperone activity that promotes the folding and chaperone activity of FliS. We further determined the crystal structures of FliS, HP1076, and the binary complex at 2.7, 1.8, and 2.7 Å resolution, respectively. HP1076 adopts a helix-rich bundle structure and interestingly shares a similar fold with a flagellin homologue, hook-associated protein, and FliS. The FliS-HP1076 complex revealed an extensive electrostatic and hydrophobic binding interface, which is distinct from the flagellin binding pocket in FliS. The helical stacking interaction between HP1076 and FliS suggests that HP1076 stabilizes 2 α helices of FliS and therefore the overall structure of the bundle. Our findings provide new insights into flagellar export chaperones and may have implications for other secretion chaperones in the type III secretion system. © FASEB.link_to_subscribed_fulltex

The antimicrobial susceptibility of Helicobacter pylori in Hong Kong (1997-2001) [1]

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One-week use of ranitidine bismuth citrate, amoxycillin and clarithromycin for the treatment of Helicobacter pylori-related duodenal ulcer

Background: Proton pump inhibitors have been widely used in combination with amoxycillin, clarithromycin or metronidazole for the treatment of Helicobacter pylori infection. Aim: To study the effects of 1-week ranitidine bismuth citrate (RBC)-based triple therapy in the treatment of H. pylori-related duodenal ulcers. Method: Patients with duodenal ulcers and II. pylori infection were prospectively randomized to receive either RBC with amoxycillin and clarithromycin for 1 week (RAC), or omeprazole with amoxycillin and clarithromycin for 1 week (OAC). No additional ulcer healing drug was used after the 1-week medication. Patients were assessed for H. pylori eradication, ulcer healing and side-effects after receiving the therapies. Results: One hundred consecutive patients were recruited to this study, with 50 patients randomized to each treatment group. In the intention-to-treat analysis, duodenal ulcers were completely healed in 45 (90%) patients in the RAC group and 43 (89.6%) in the OAC group (P = 1.0). H. pylori eradication was confirmed in 47 (94%) in the RAC group and 42 (87.5%) in the OAC group (P = O.31). There was no significant difference in the severity of side-effects experienced by the two treatment groups. Conclusion: One-week RBC-based triple therapy is an effective treatment for H. pylori-related duodenal ulcers. The therapeutic effects are comparable to a 1-week course of proton pump inhibitor-based triple therapy.link_to_subscribed_fulltex