This article describes the establishment of a Helicobacter pylori infection model in mice. The procedure involves intragastric gavage to deliver bacterial suspensions directly into the stomach, allowing for the study of bacterial colonization and its effects on gastric tissue.
To establish a Helicobacter pylori infection model, begin with an anesthetized, pathogen-free mouse. Restrain the mouse firmly to minimize movement during the procedure.
Take a syringe filled with a bacterial suspension. Connect a polyethylene catheter to the needle of the syringe for intragastric gavage — a technique of delivering the suspension directly into the stomach.
Insert the catheter into the center of the open mouth to access the esophagus, a muscular tube connecting the mouth to the stomach. Gently guide the catheter through the esophagus until it reaches the stomach, and deliver the bacterial suspension directly into its acidic environment.
The inoculated bacteria secrete urease, an enzyme that converts urea into ammonia and carbon dioxide. The ammonia raises the pH of the stomach, neutralizing the acidity and enabling the bacteria to survive.
These bacteria utilize their flagella to traverse through the protective mucus layer, allowing them to reach the gastric epithelium, where they adhere to cells using adhesin proteins. Upon attachment, these bacteria release virulence factors that disrupt the tight junctions between the epithelial cells.
This structural disruption promotes bacterial invasion and colonization in deeper tissues, ultimately establishing a controlled infection in the stomach.
Add bacterial suspensions to 15-milliliter polystyrene tubes, and use a plastic loop to transfer one 10- to 20-microliter droplet from each culture onto individual glass microscope slides. Then, assess the viability and motility of the bacteria under phase contrast microscopy at a 100 times magnification.
Only use the H. pylori inocula if the majority of the bacteria have a bacillary shape. H. felis inocula should primarily contain helical-shaped bacteria, and load the inocula into individual disposable 1-milliliter syringes. Equip each syringe with a 23-gauge needle and use plastic paraffin film to attach a disposable polyethylene catheter to each needle.
Next, manually restrain a 6- to 8-week-old specific pathogen-free and Helicobacter-free mouse by the scruff of the neck and tail and insert one catheter into the center of the open jaw. Guide the catheter in a caudal direction toward the esophagus, extending the neck of the mouse to allow ease of access to the stomach through the esophagus and away from the trachea until most or all of the catheter is no longer visible and a resistance is felt. Then, deliver at least 1 x 105 bacteria to ensure an optimal colonization in disease pathology.
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