On Wiki it lists the following statement about omeprazole being use WITH antibiotics for Helicobator pylori. I think you must have confused other similar statements, thinking the drug contains the antibiotic, when it's actually just used in conjunction with them.

"As a therapeutic adjuvant in treating Helicobacter pylori related ulcers
Omeprazole is combined with the antibiotics clarithromycin and amoxicillin (or metronidazole in penicillin-hypersensitive patients) in the 7–14 day eradication triple therapy for Helicobacter pylori."

http://en.wikipedia.org/wiki/Omeprazole

The drug is simply a protein pump inhibitor