People taking the ulcer drug omeprazole face a 10 fold increased risk of developing gastroenteritis caused by the bug campylobacter, now a more common stomach infection than salmonella.
Researchers who made the discovery suggest that the drug may lower stomach acid, which, in turn, could change the bacterial flora in the stomach that protects against infections such as salmonella and campylobacter.
Another factor, although less extreme, is the use of antibiotics, which may also affect the stomach flora.
Researchers from the University of Nottingham analyzed 211 cases of campylobacter reported to the Nottingham Health Authority between 1992 and 1994. They found that patients who had taken omeprazole for a month before the infection were associated with a 10 fold increased risk. The risks reduce to nothing once the patient comes off the drug, they also found.
The drug may also increase the severity of infection because it makes the stomach less effective in killing organisms.