Bacteria against bacteria: probiotics can improve H. pylori eradication rates H. pylori is a common pathogen in the gastric mucosa and is closely associated with chronic gastritis, peptic ulcers and gastric cancer. Conventional eradication regimens include proton pump inhibitors, amoxicillin and clarithromycin, with an eradication success rate of 80-85% after 1-2 weeks of treatment. During eradication, a few patients may experience adverse effects such as C. difficile infection, pseudomembranous enteritis and antibiotic resistance, and antibiotic-induced intestinal dysbiosis will also weaken the intestinal barrier, reduce immunity, and even affect metabolic regulation. Probiotics are beneficial to host health and can assist in inhibiting intestinal pathogens, reducing lactose intolerance, and improving constipation. Probiotic supplementation in H. pylori eradication regimens has been shown to improve eradication rates and reduce the incidence of adverse effects, but specific changes in intestinal flora before and after eradication have not been evaluated. To this end, Bumjo et al. from Seoul National University School of Medicine in Korea conducted a randomized controlled trial to confirm that probiotic supplementation reduced antibiotic-related adverse effects such as intestinal flora translocation and growth of drug-resistant bacteria during eradication, thereby improving eradication rates, and the results were published in a recent issue of Helicobacter. The study cases were selected from patients with peptic ulcer who were followed up by gastroscopy. The inclusion criteria were: confirmed diagnosis of peptic ulcer with Hp(+); no renal disease, diabetes and cardiovascular disease; and no history of intestinal surgery. The selected cases were divided into two groups: control group: standard triple therapy, i.e., 500 mg clarithromycin, 1 g amoxicillin, 30 mg lansoprazole twice daily for 2 weeks; probiotic group: probiotics (Medilac-S: Streptococcus faecalis 9×108; Bacillus subtilis 1×108) were added to the former group twice daily for 2 weeks. The results of the study showed that of the 23 patients, 11 were included in the control group (1 lost) and 12 in the probiotic group (2 lost), so that 10 of the final 20 patients were included in each of the two groups. Four weeks after the end of eradication, the eradication success rate was evaluated by rapid urease test (UBT), which was 100% in the probiotic group and 90% in the control group, but there was no significant difference between them due to their small sample size. For adverse reactions, gastrointestinal symptoms, rash, headache/dizziness and esophageal irritation were evaluated, with 4 cases in the control group and 5 cases in the probiotic group, also without significant differences. To assess the changes in intestinal flora before and after the treatment, the number of major intestinal flora, including Bacillus thuringiensis, Bacillus mimicus and Bacillus deformans, was measured from stool specimens. The results showed a decrease in the relative number of Bacillus mimicus and an increase in the relative number of Aspergillus in both groups after treatment. A higher percentage of these changes occurred in the control group than in the probiotic group. This result confirms that probiotics may reduce antibiotic-induced alterations in intestinal flora. To assess the changes in drug-resistant flora before and after treatment, Citrobacter, Klebsiella, Pseudomonas and Escherichia were selected for determination, mainly induced by amoxicillin and clarithromycin. The drug-resistant flora was similar in both groups before treatment (0% to 1.5% of the overall intestinal flora), while the proportion of drug-resistant flora increased significantly in the control group and not significantly in the probiotic group after treatment, and the difference between the two groups was statistically significant. These results suggest that probiotics may inhibit the growth of drug-resistant flora. In conclusion, the investigators concluded that probiotic supplementation in H. pylori eradication protocols can reduce antibiotic-induced intestinal flora translocation and inhibit the growth of drug-resistant flora, thus improving the eradication success rate. This result is significant in guiding H. pylori eradication therapy, and larger studies are needed to confirm these results.