Background The aim of this study was to identify risk factors for Clostridium difficile infection (CDI) and its attributable mortality and to propose methods to prevent CDI and improve patients’ outcomes. Methods CDI was defined as diarrheal patients with stool samples that were positive for C. difficile toxin. Clinical presentations of all patients with CDI and two times as many age- and sex-matched culture-negative controls at the Chang Gung Memorial Hospital in 2014 were identified and compared by multivariate, nonparametric, and Kaplan–Meier survival analysis. Results There were no significant differences in ages, sex, or Charlson comorbidity indexes between the CDI group (n = 42) and the control group (n = 86). The multivariate analysis indicated that underlying peptic ulcer disease and previous use of gastric acid inhibitors or third-generation cephalosporins for at least 3 days were significantly more common in patients with CDI than in the controls. Charlson scores were associated with mortality due to CDI. Recommended treatment using oral vancomycin to treat patients with Charlson score ≥ 5 and oral metronidazole or vancomycin to treat those with moderate underlying disease (Charlson score ≥ 2 and ≤ 5) significantly increased survival in these patients ( p = 0.001). Conclusions Oral vancomycin given to patients with high Charlson scores and oral metronidazole or vancomycin to patients with moderate Charlson scores decreased mortality due to CDI. Restricting the use of third-generation cephalosporins and gastric acid inhibitors is recommended to prevent CDI in hospitalized patients.

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What is known and objective Gut microbiota plays an important role in shaping immune responses. Several studies have reported that antibiotics may alter gut microbiota diversity and compromise the therapeutic response to immune checkpoint inhibitors (ICIs). Nevertheless, the impact of a specific class of antibiotics on ICIs therapy is still not known. The aim of this study was to analyse the influence of antibiotics on the clinical outcomes of non‐small cell lung cancer (NSCLC) patients treated with ICIs and to compare the effects of fluoroquinolones vs. other broad‐spectrum antibiotics. Methods This retrospective cohort study (n = 340) analysed data from Chang Gung Research Database, which comprises work from seven medical institutions in Taiwan. Patients with NSCLC who received ICIs between January 2016 and March 2019 were evaluated. The data of patients who received antibiotics (ie fluoroquinolone) within 30 days prior to ICIs therapy were analysed. Overall survival (OS) was the goal of our study and was calculated from the time the ICIs therapy start. Survival analysis was estimated using the Kaplan‐Meier and Cox statistics. Results A total of 340 patients were identified for analysis. Of the 340 patients, only over one third (38%) of patients received antibiotics 30 days prior to ICI therapy. These patients exhibited a shorter OS compared with those not receiving antibiotics (median OS, 266 days vs. 455 days; hazard ratio (HR), 2.9; 95% confidence interval (CI), 1.1–8.1, p = 0.003). In this study, 127 out of 128 patients who were exposed to antibiotics had received at least one broad‐spectrum antibiotic. We observed patients who had received fluoroquinolone had a shorter OS compared with those receiving other broad‐spectrum antibiotics (median OS, 121 days vs. 370 days; HR, 1.582; 95% CI 1.007–2.841; p = 0.047). What is new and conclusion Antibiotic treatment, especially fluoroquinolone, prior to ICIs therapy was associated with poorer clinical efficacy in NSCLC patients. Antibiotics should not be withheld when there is a clear need for them despite the possibility of interfering with the microbiome, which may, in turn, adversely affect the ICI’s effectiveness. However, one should consider avoiding the use of fluoroquinolones antibiotics.