Effect of varying pH on the susceptibility of Campylobacter pylori to antimicrobial agents.

The susceptibility of 22 clinical isolates of Campylobacter pylori to eight antimicrobial agents was studied under varying pH conditions. Macrolides (erythromycin, dirythromycin), clindamycin and to a lesser extent quinolones lost efficacy at lowered pH. The activity of ampicillin and metronidazole remained relatively stable throughout the pH range tested. The effect of pH an antimicrobial efficacy may warrant consideration when selecting an antibiotic to clear Campylobacter pylori in vivo, since the pH of the gastric submucous environment is not known for certain.