Clarithromycin-Based Triple Therapy is Still Useful as an Initial Treatment for Infection in the Dominican Republic.

Abstract antibiotic susceptibility in the Dominican Republic has not been monitored. We assessed antibiotic susceptibility in the Dominican Republic, and analyzed mutations associated with antibiotic resistance. We recruited 158 dyspeptic patients in Santo Domingo and used agar dilution to test susceptibility to five antibiotics. Polymerase chain reaction-based sequencing was used to assess , , , , and 23S rRNA mutations; next-generation sequencing was used to identify other metronidazole resistance-associated genes. Among 64 strains isolated, we identified two (3.1%), one (1.6%), and no strains with clarithromycin, amoxicillin, and tetracycline resistance, respectively. Moreover, high frequency of metronidazole resistance (53/64, 82.8%) was observed, whereas levofloxacin resistance is emerging (23/64, 35.9%). We identified many and mutations in metronidazole-resistant strains, but no synergistic effect was apparent. We revealed novel mutations in , , , and , irrespective of and mutations. Novel mutations at Ser-14 of and Arg-221 of were associated with different levels of metronidazole resistance. Most levofloxacin-resistant strains had a substitution at Asn-87 of , including the strain with the highest levofloxacin resistance, whereas only three substitutions were found at Ser-479 of with no synergistic effect. Besides the 23S rRNA A2142G mutation, we observed another mutation at T1958G in both clarithromycin-resistant strains. We confirmed high metronidazole and levofloxacin resistance associated with genetic mutations in the Dominican Republic. However, prevalence of clarithromycin resistance was low, suggesting that standard clarithromycin-based triple therapy remains useful as initial treatment of infection.