H. pylori is a Gram-negative microaerobic bacterium that is spiral in shape and has 2–6 polar flagella for mobility. This bacterium resides between the surface of the gastric mucosa and the mucin layer without evidence of intracellular parasitism.19 H. pylori can only survive at a periplasmic pH of 4.0–8.5 and can only grow at a periplasmic pH of 6.0–8.5. It is difficult to detect H. pylori in the gastric lumen because it is such an acidic environment.
The human stomach is divided into three anatomic regions: the cardia, the fundus/corpus, and the antrum. The antrum secretes alkaline mucus 4–5 cm around the antrum. Therefore, H. pylori is mainly distributed in the antrum.20 H. pylori distribute in two ways: (1) by colonizing the surface of the gastric pit and epithelial cells, and (2) by colonizing above the tissue surface mucus layer. The latter is more common. An animal model revealed that H. pylori colonizes a zone 0–25 μm above the tissue surface mucus layer, to a total thickness of about 100 μm.21 While the gastric lumen has a pH of 1–2, a pH gradient exists across the mucus layer, reaching a pH of 6–7 at the surface of the mucosa.22 Using chemotaxis, H. pylori navigate this pH gradient to reach their niche environment near the host epithelium. 23,24
Research has revealed that the stomach supports a bacterial community comprising hundreds of phylotypes,25, 27 while a pH of < 4 prevents bacterial overgrowth. It was reported that the microbial density in the stomach is 101–103 CFU/g28, 29 This high density of bacteria means that Giemsa staining is not an optimal method for studying H. pylori in the stomach. Therefore, in this study, we employed the RUT, PCR analysis, and culture methods to study H. pylori in gastric juice.
Until now, little is known about the movement characteristics of H. pylori all over the world. We use PPI intervene the patients infected with H. pylori and study the movement characteristics of H. pylori. In this study, the pH of gastric juice in control group patients was range from 1 to 3 with an average of 1.59, which was consistent with normal pH value of gastric juice. The pH of the gastric juice of patients in the intervention group was higher than that in the control group, but H. pylori was detected in both groups. Culture is the gold standard method for detecting the presence of viable H. pylori. In our study, the positive detection rate was significantly higher in the gastric juice of patients in the intervention group than of patients in the control group. The RUT and PCR analysis also indicated that positive detection rates were significantly higher among patients in the intervention group than among those in the control group. The results of culturing, the RUT, and PCR were consistent. Our findings indicated that PPI intervention may induce H. pylori to penetrate across the mucus layer from the surface of the gastric mucosa to the gastric lumen. However, one positive case was detected by the RUT of the gastric fluid from the control group and this sample had a pH value of 1, possibly indicating that the gastric fluid may be mixed with slight bile. In addition, six samples from the control group tested positive by PCR, which might indicate that there was a high load of H. pylori for these bacteria to be detected in the gastric lumen.
H. pylori is a fastidious microorganism that requires complex growth media. The H. pylori living environment is small in the mucus layer and a key feature of this bacterium is its microaerophilicity, with optimal growth at O2 levels of 2% to 5%.30 H. pylori is unable to survival under normal atmospheric conditions or under absolute anaerobic conditions. H. pylori requires complex growth media rich in nutrients. However, the mucus layer has low permeability to most molecules such as protons, O2, and nutrient macromolecules. If the condition of juice in gastric lumen met the qualification mentioned above, H. pylori may penetrate across the mucus layer to the gastric lumen.
It is reported that PPI alone also exerts direct antimicrobial activity against H. pylori with 6%–7.7% eradication rate, 31, 32which was confirmed by Meining and colleagues.33 Iwahi and coworkers34 practiced a more in-depth study of PPI, and surprisingly found that lansoprazole could inhibit the growth of H. pylori in vitro, similar to the antibacterial effects of antibiotics. A series of subsequent studies found that omeprazole, pantoprazole, and rabeprazole have different degrees of inhibitory effects on H. pylori in vitro, with rabeprazole showing the strongest bacteriostatic effect. However, these differing effects of PPIs have not been reported in clinic. According to our research results, we propose that PPI intervention may reduce the pH gradient, disturbing the pH chemotaxis of H. pylori and leading to the penetration of the mucus layer. The flagella of H. pylori often carry a distinctive bulb at the end. The flagella confer motility and allow rapid movement in viscous solutions such as the mucus layer overlying the gastric epithelial cells.35 Motile bacteria sense chemical gradients by means of chemoreceptor proteins, such as BabA, with a pH–sensor mechanism36, and relay the information to the flagellar motor 37 to direct movement toward an environment with optimal concentrations of both electron acceptors and proton/electron donors. Another study reported that among H. pylori exposed to neutral pH, only about 7% of the culture were motile and traveled at an average speed of 10.5 μm per s. By contrast, among cells that were shifted to an acidic pH, 66% were motile with a significantly faster average speed of 24.3 μm per s38. It seems likely that H. pylori uses the pH-sensing mechanism for orientation along the transmucus pH gradient. H. pylori can penetrate across the mucus layer to the gastric lumen when the pH gradient is reduced by PPI intervention. By the results in this study, H. pylori can be more easily detected in whom received intravenous PPI infusion which may imply the H. pylori in gastric lumen following PPI intervention. However, there are several factors involving the motility of H. pylori further investigation may be necessary