Effects of Antibiotic Treatment for Helicobacter pylori on Normal Bowel Bacteria

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The summary below is from the full report titled "Long-Term Persistence of Resistant Enterococcus Species after Antibiotics To Eradicate Helicobacter pyori." It is in the 16 September 2003 issue of Annals of Internal Medicine (volume 139, pages 483-487). The authors are M. Sjölund, K. Wreiber, D.I. Andersson, M.J. Blaser, and L. Engstrand.

What is the problem and what is known about it so far?

Dyspepsia is stomach pain or discomfort. It may occur in patients with sores in the stomach lining (ulcers) or in patients who do not have ulcers. Sometimes tests show that patients with dyspepsia or ulcers have a common bacterial infection known as Helicobacter pylori infection. A combination of drugs that treat infection (antibiotics) and drugs that block stomach acid is widely used to treat H. pylori infections. The antibiotics usually rid the body of the H. pylori infection within 2 weeks. However, they also could affect other bacteria in the body. For example, bacteria sometimes develop an ability to thwart the action of antibiotics (resistance). Bacteria that are normally found in the body can develop resistance to antibiotics, even if the antibiotics are given to fight different bacteria that cause infection. This might cause problems later if a patient gets an infection with bacteria similar to those normally found in the body.

Why did the researchers do this particular study?

To learn whether a combination of drugs (clarithromycin, metronidazole, and omeprazole) widely used to kill H. pylori affects antibiotic resistance of a normal species of bacteria (Enterococcus) in the colon.

Who was studied?

10 patients who had endoscopy to evaluate dyspepsia.

How was the study done?

Doctors treated 5 of the patients, who had ulcers and H. pylori infection, with antibiotics (clarithromycin and metronidazole). They did not give the 5 patients without ulcers antibiotics. The researchers collected fecal samples from all patients at the beginning of the study and then several days and 1 and 3 years later. They cultured enterococci from the samples and did special tests (DNA fingerprints, gene tests, and minimal inhibitory concentration) to see whether the enterococci were resistant to clarithromycin.

What did the researchers find?

All enterococci that were found in feces several days after treatment with antibiotics were highly resistant to clarithromycin. In 3 of the treated patients, resistance persisted for 1 to 3 years. No enterococci in untreated patients were resistant to clarithromycin.

What were the limitations of the study?

The number of patients was small. The long-term implications of having enterococci in the colon that were resistant to commonly used antibiotics were not studied.

What are the implications of the study?

Short-term treatment of H. pylori infection with a commonly used antibiotic leaves behind bacteria in the colon that are resistant to that antibiotic. Whether and how this resistance will eventually lead to clinical problems is not yet clear.