Background: Helicobacter pylori resistance to clarithromycin is relatively
frequent in France and is assumed to be the main cause of failure of the pr
oton pump inhibitor-amoxicillin-clarithromycin (proton pump inhibitor-AC) t
herapy, which is the first-line regimen in France.
Aim: To determine the respective effects of clarithromycin primary and seco
ndary resistances on efficacy of the proton pump inhibitor-AC regimen and t
o determine whether failures are associated with persistence of the same st
rain or with emergence of a new one.
Methods: A total of 123 H. pylori-infected patients were treated for 7 days
with omeprazole 20 mg b.d., amoxicillin 1 g b.d., and clarithromycin 500 m
g b.d. Eradication was assessed by breath test in 102 patients. Minimal inh
ibitory concentrations of clarithromycin were determined by E-test. Strain
genotyping was performed by random amplified polymorphic DNA.
Results: The pre-treatment and post-treatment prevalences of clarithromycin
resistance were 19% (23 out of 123) and 69% (nine out of 13), respectively
, The rates of eradication were 68% (69 out of 102), 79% (67 out of 85), an
d 12% (two out of 17) for all, susceptible and resistant strains, respectiv
ely. The post-treatment isolate was available for six patients with a susce
ptible pretreatment isolate and a persistent infection. Resistance emerged
in two patients and was associated with persistence of the pre-treatment st
rain in one and with selection of a new strain in the other.
Conclusions: In our hospital, failures of the proton pump inhibitor-AC ther
apy are related to both clarithromycin primary and secondary resistances, b
ut the emergence of secondary resistance does not explain all of the failur
es in the initial clarithromycin-susceptible group. In that group a new str
ain can emerge after failure.