High percentage of clarithromycin and metronidazole resistance in Helicobacter pylori clinical isolates obtained from Spanish children

Abstract

Objective: To determine the primary and secondary resistance to several antimicrobial agents in Spanish Helicobacter pylori clinical isolates obtained from paediatric patients from January 2002 to June 2006.

Methods: Samples were collected from gastric biopsies of symptomatic paediatric patients and H. pylori cultured according to standard microbiological procedures. Resistance was determined by E-test. Strains were considered resistant if minimal inhibitory concentration (MIC) > or = 2 mg/l for amoxycillin, > or = 4 mg/l for tetracycline, > or = 8 mg/l for metronidazole, > or = 1 mg/l for clarithromycin, MIC > or = 4 mg/l for ciprofloxacin, MIC > or = 32 mg/l for rifampicin and intermediate if MIC = 0.5 mg/l for clarithromycin, and MIC = 2 mg/l for ciprofloxacin.

Results: A total of 101 patients were included: 38 males and 63 females (sex ratio M/F: 0.6). Average age was 10 years (range: 4-18 years). All strains were susceptible to amoxycillin, tetracycline and rifampicin, 35.7% were resistant to metronidazole, 54.6% to clarithromycin and 1.8% to ciprofloxacin. 2.0% were intermediate to clarithromycin and 1.8% to ciprofloxacin. Double resistance to metronidazole and clarithromycin rated at 17.2%. Thirty-five patients (34.7%) had a history of treatment failure, and were considered as secondary H. pylori. Primary resistance rates to metronidazole and clarithromycin were 32.8% and 49.2%, respectively, and secondary resistance rates were 41.2% and 70.6%, respectively.

Conclusions: Resistance to clarithromycin (56.6%) was higher than to metronidazole (35.7%) in the H. pylori strains studied. Clarithromycin resistance was very high even in strains from paediatric patients not previously treated for H. pylori infection.