MACROLIDE RESISTANCE IN HELICOBACTER-PYLORI - MECHANISM AND STABILITYIN STRAINS FROM CLARITHROMYCIN-TREATED PATIENTS

Helicobacter pylori strains from seven patients treated with clarithro mycin were investigated for development, mechanism, and stability of r esistance. Genetic relatedness between pre- and posttreatment isolates was shown by arbitrary primed PCR. Clarithromycin resistance was asso ciated with A-to-G transitions at either position 2143 or 2144 or at b oth positions 2116 and 2142. In four cases, the mutations were homozyg ous. The Cla(r) phenotype was stable after 50 subcultivations in vitro . No erythromycin-modifying enzymes or rRNA methylases were found by b iological assays, PCR and sequencing, or cloning methods.