In vitro antagonism of rabeprazole and metronidazole upon clinical isolates of Helicobacter pylori.
BACKGROUND
Rabeprazole inhibits Helicobacter pylori in vitro. This property could influence the antibacterial activity of metronidazole or amoxicillin. Our goal was to evaluate in vitro the effect of rabeprazole upon the antibacterial activity of metronidazole and amoxicillin.


METHODS
The minimal inhibitory concentration (MIC) was determined by agar dilution upon 30 clinical isolates, and the antibacterial effect of the combined drugs was estimated by calculating the fractional inhibitory concentration index (FICI).


RESULTS
Nine strains (30%) were resistant to metronidazole (MIC 8-256 mg/l) while only 1 strain was resistant to amoxicillin (MIC 1.0 mg/l). Rabeprazole also inhibited H. pylori (MIC 0.125-1.0 mg/l). The association of metronidazole and rabeprazole showed synergism in 30% of the strains (FICI < or =0.25), but also antagonism in 23.3% of the clinical isolates (FICI > or =4.0). Mostly, amoxicillin-rabeprazole showed an effect of synergism (53.3%).


CONCLUSIONS
The results presented suggest the need to keep in mind that failure in eradication therapies based on metronidazole and rabeprazole could be due to an antagonism of the drugs.
Soto
Alejandra
A
Departamento de Microbiología, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile.
García
Apolinaria
A
González
Carlos L
CL
D053799:2-Pyridinylmethylsulfinylbenzimidazoles / Q000494:pharmacology*; D000658:Amoxicillin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D016481:Helicobacter Infections / Q000188:drug therapy; D016480:Helicobacter pylori / Q000187:drug effects* / Q000302:isolation & purification; D006801:Humans; D008795:Metronidazole / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D064750:Rabeprazole
D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D000900:Anti-Bacterial Agents; D008795:Metronidazole; D064750:Rabeprazole; D000658:Amoxicillin