Helicobacter pylori: Primary Susceptibility to Clarithromycin in vitro in Nova Scotia

Abstract

Resistance to antimicrobial agents is a major determinant of the efficacy of regimens to eradicateHelicobacter pylori. Clarithromycin (CLA) has become one of the most commonly used antibiotics for treatment ofH pyloriinfection. In this study, the rate of primary resistance to CLA inH pyloriisolated from patients was determined. One hundred sixty-two strains were recovered from patients before treatment. Strains were grown and inoculated onto Mueller-Hinton agar with 7% sheep blood. CLA epsilometer gradient agar diffusion test (E test) strips were used to test for susceptibility. Appropriate control organisms were tested to validate the assay. Plates were incubated at 37°C in a microaerophilic atmosphere for up to five days. E test results were easy to interpret. Strains were considered resistant if the minimum inhibitory concentration (MIC) was 2 µg/mL or greater. Three strains were resistant (two strains with MIC 8 µg/mL and one strain with MIC 12 µg/mL), and 159 strains were sensitive (MICs ranged from less than 0.016 to 0.38 µg/mL). Ninety per cent of the strains had MICs of 0.023 µg/mL. Primary resistance was 1.8%. These susceptibility data support the use of CLA for the treatment ofH pyloriin the Nova Scotia population.