GENOTYPIC CHARACTERIZATION OF CLARITHROMYCIN-RESISTANT AND - SUSCEPTIBLE HELICOBACTER-PYLORI STRAINS FROM THE SAME PATIENT DEMONSTRATES EXISTENCE OF 2 UNRELATED ISOLATES

Clarithromycin-susceptible and clarithromycin-resistant Helicobacter p ylori isolates from the same patient were investigated far the mode of development and mechanism of clarithromycin resistance. The clarithro mycin-resistant strain UA1182 harbors homozygous A-to-G mutations at p osition 2143 in both copies of the 23S rRNA gene and has a phenotype o f resistance to clarithromycin and clindamycin best no significant res istance to streptogramin B. Pulsed-field gel electrophoresis patterns of NruI- and NotI-digested genomic DNA from the Cla(s) and Cla(r) isol ates demonstrated that they are genetically distinct, suggesting that the development of clarithromycin resistance is not from the mutation of the existing Clas strain but from a completely new strain.