Clarithromycin resistance stability in Helicobacter pylori: influence of the MIC and type of mutation in the 23S rRNA.
Thirty clarithromycin-resistant Helicobacter pylori strains (MIC range 8-64 mg/L) were subcultured in a drug-free medium and the MIC was determined every five passages to detect in vitro stability of resistance. Three out of the 30 (10%) lost their resistance after 10, 13 or 18 subcultures (MIC decrease from 8 to 0.008, from 16 to 0. 064 and from 32 to 0.016 mg/L). The effect of four macrolides at subinhibitory concentrations on the development of resistance was studied in H. pylori NCTC 11638 and TIGR 26695. A change in the MIC was observed only when NCTC11638 was exposed to 0.5 x MIC of erythromycin for 20 days.
Alarcón
T
T
Department of Microbiology, Hospital Universitario de la Princesa, Diego de León 62, 28006 Madrid, Spain. talacron@helicobacterspain.com
Domingo
D
D
Prieto
N
N
López-Brea
M
M
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D017291:Clarithromycin / Q000494:pharmacology*; D003470:Culture Media; D004352:Drug Resistance, Microbial / Q000235:genetics; D016480:Helicobacter pylori / Q000187:drug effects* / Q000235:genetics; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D009154:Mutation / Q000187:drug effects* / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000187:drug effects* / Q000235:genetics
D000900:Anti-Bacterial Agents; D003470:Culture Media; D012338:RNA, Ribosomal, 23S; D017291:Clarithromycin