Multicenter retrospective observational study on the clinical effectiveness of butyrate-producing Clostridium butyricum containing probiotics in patients with COVID-19

(CB)-containing probiotics in patients with coronavirus disease 2019 (COVID-19) remains unclear. We investigated the in-hospital mortality, period of mechanical ventilation, and incidence of secondary bacterial pneumonia in patients with COVID-19 from 2020 to 2021. The patients were divided into the probiotic (27) and non-probiotic (256) groups. The two groups did not show a significant difference in the SOFA scores (probiotic vs. non-probiotic, 2.1 ± 2.3 vs. 2.1 ± 2.9). Additionally, all patients received antiviral agents to treat COVID-19; however, the two groups did not show significant difference in their distribution. However, patients receiving CB preparations showed the shorter periods of mechanical ventilation (1.1 ± 2.5 days vs. 3.9 ± 9.4 days). Although not statistically significant, they also showed lower incidence of secondary bacterial pneumonia (7.4% vs. 15.6%) and the lower in-hospital mortality (3.7% vs. 15.2%) compared to the non-probiotic group. This retrospective clinical study revealed that the administrations of CB preparations might attenuate clinical symptoms related to COVID-19 and improve mortality. However, further clinical and basic studies are required to validate our findings.