Quantification of Helicobacter pylori Load in an Infected Mouse Stomach

To count the number of viable H. pylori in the stomach post-infection, homogenize stomach samples stored in BHI, and perform duplicate serial dilutions of the resulting gastric homogenates in fresh sterile broth.

Divide pre-dried horse blood agar, or HBA plates, supplemented with additional antibiotics into three or four segments, and using an adaptation of the Miles and Misra technique, add 10 to 100 microliters of each stomach homogenate dilution onto a segment of each agar plate. Spread the homogenates with sterile plastic loops and allow the plates to dry. Then, place the plates in an inverted position in anaerobic gas jars containing a Petri dish of water and a gas pack, then, incubate the jars at 37 degrees Celsius for four to seven days.

When colonies can be observed, enumerate the segments containing between 10 and 100 isolated colonies.