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[Detection of resistance to clarithromycin in clinical isolates of Helicobacter pylori from children and adults].

Several methods have been used to detect clarithromycin resistance. Agar dilution is now recommended by the NCCLS (susceptible to clarithromycin: MIC<=0.25 mg/l; intermediate resistance: MIC=0.5 mg/l; resistant: MIC>=1 mg/l), and the detection of mutations involved in resistance is used in many laboratories. We analyzed 36 clarithromycin-resistant strains isolated from children and 30 from adults. In vitro susceptibility to clarithromycin was determined by an agar dilution method. DNA from the isolates was extracted using the method published by Ge and Taylor. A2142G and A2143G mutations were identified by PCR-RFLP. A 1.4 Kpb of the 23S rRNA gene was amplified and digested using MboII or BsaI restriction enzymes to detect mutations. The prevalence of the A-G transition mutation at position 2143 was higher in the children (80.55%) than in the adult patients (46.66%) (p<0.05); however, the prevalence of the mutation at position 2142 was higher in adults than in children (36.66% vs. 5.55%; p<0.05). In children, a higher MIC (2-64 mg/l) was observed when the A-G mutation was detected at position 2143. However, in adult patients higher MICs were observed when the A-G mutation was detected at position 2142.