Background:Helicobacter pylori (Hp)infection is correlated with the development of chronic gastritis,peptic ulcer, mucosa-associated lymphoid tissue lymphoma and gastric cancer.Studies showed that Lactobacillus acidophilus could improve the eradication rate of Hp and reduce the occurrence of side-effects.Aims:To evaluate the efficacy of compound Lactobacillus acidophilus tablets combined with bismuth-containing quadruple therapy for the treatment of failed eradiction of Hp infection.Methods:One hundred and eighty patients with Hp-positive peptic ulcer in whom standard triple therapy failed were enrolled and then randomly assigned into experimental group and control group.Patients in experimental group received compound Lactobacillus acidophilus tablets 1 g tid for 14 days,followed by rabeprazole 10 mg bid +amoxicillin 1 000 mg bid +furazolidone 100 mg bid +bismuth 300 mg qid for 10 days.Patients in control group received rabeprazole 10 mg bid +amoxicillin 1 000 mg bid +furazolidone 100 mg bid +bismuth 300 mg qid for 10 days.13 C-urea breath test was conducted at least 4 weeks after completion of the course,Hp eradication rate and side-effects were evaluated. Results:No significant differences in PP eradication rate and ITT eradication rate were found between experimental group and control group (PP:81.2% vs.78.2%,χ2 =0.241,P =0.623;ITT:76.7% vs.75.6%,χ2 =0.031,P =0.861).Incidences of nausea and vomiting (2.4% vs.11.5%),diarrhea (0 vs.9.2%)in experimental group were significantly decreased than those in control group (P <0.05).Conclusions:Compound Lactobacillus acidophilus tablets combined with bismuth-containing quadruple therapy is efficient for Hp-positive patients with failed standard triple therapy and can reduce side-effects.