Diminishing Efficacy of Second-Line Levofloxacin-Based Quadruple Therapy in Eradication: A Prospective Real-World Study in Vietnam Amid Rising Antibiotic Resistance.

() infection remains highly prevalent in Vietnam, associated with chronic gastritis, peptic ulcers, and gastric cancer. This study aimed to evaluate the real-world eradication rate of levofloxacin-based bismuth quadruple therapy (PALB) as second-line treatment, assess adherence, and identify associated factors with treatment success. We conducted a prospective cohort study including 225 patients with confirmed failure of classical bismuth-based quadruple therapy. All received a 14-day PALB regimen. eradication was assessed using 13C-urea breath test and/or rapid urease test 4-12 weeks after treatment. Eradication rates were 78.2% (mITT) and 78.6% (PP), with 95% CIs overlapping the 80% benchmark. Adherence was high (91.6%) and significantly associated with success (OR = 2.93; 95% CI: 1.11-7.74; = 0.039). No other factors were significantly associated. While PALB remains a valid second-line therapy, its efficacy may be declining, though not statistically inferior to 80%. Improving adherence and strengthening stewardship are essential.