Long-term persistence of resistant Enterococcus species after antibiotics to eradicate Helicobacter pylori

Antibiotic treatment selects for resistance not only in the pathogen to which it is directed but also in the indigenous microflora.

To determine whether a widely used regimen (clarithromycin, metronidazole, and omeprazole) for Helicobacter pylori eradication affects resistance development in enterococci.

Cohort study.

Endoscopy units at 3 community hospitals in Sweden.

5 consecutive dyspeptic patients who were colonized with H. pylori, had endoscopy-confirmed duodenal ulcer, and received antibiotic treatment, and 5 consecutive controls with dyspepsia but no ulcer who did not receive treatment.

Fecal samples were obtained from patients and controls before, immediately after, 1 year after, and 3 years after treatment. From each patient and sample, enterococci were isolated and analyzed for DNA fingerprint, clarithromycin susceptibility, and presence of the erm(B) gene.

In treated patients, all enterococci isolated immediately after treatment showed high-level clarithromycin resistance due to erm(B). In 3 patients, resistant enterococci persisted for 1 to 3 years after treatment. No resistance developed among controls.

A common H. pylori treatment selects for highly resistant enterococci that can persist for at least 3 years without further selection.