Final answer:
The main culprit in creating peptic ulcers is the bacterium Helicobacter pylori. It is responsible for majority of stomach and duodenal ulcers, and can be transmitted through contaminated food, water, or saliva.
Step-by-step explanation:
The main culprit in creating peptic ulcers is the bacterium Helicobacter pylori. It is a gram-negative bacterium that can survive in the acidic environment of the human stomach. H. pylori is responsible for approximately 80% of stomach ulcers and over 90% of duodenal ulcers. Infection with H. pylori can be transmitted through contaminated food, water, or saliva.