In a retrospective case-control study, intestinal probiotic supplementation played a pivotal role in the treatment of elderly patients (aged 55 to 90 years) suffering from severe pneumonia. The objective of the study was to conduct a prospective investigation among 88 pneumonia patients in the respiratory and intensive care unit, examining the clinical significance of probiotic therapy in pneumonia and its impact on intestinal microbiota. This research aimed to offer fresh perspectives for clinical application.

The study included 59 male and 29 female participants, with an average age of 81.8 years. The enrolled patients were randomly assigned into 2 groups: a probiotic group (n = 40; 29 males and 11 females) and a control group (n = 48; 30 males and 18 females). In the probiotic group, patients received enteric-coated capsules containing live combined Bacillus subtilis and Enterococcus faecium, as well as Bacillus Licheniformis capsules, each administered at a dose of 0.5 g, three times a day. Patients experiencing difficulty with oral intake were administered feeds through an anasointestinal tube after dissolving 25 ml of sterilized water.

Each patient was observed for the duration and peak of fever, gastrointestinal symptoms (diarrhoea or constipation), the presence or absence of mechanical ventilation, the presence or absence of deep venous catheterization, and the presence or absence of sepsis. Patients underwent evaluation of pneumonia severity index (PSI) pneumonia scores both before and 21 days after treatment. Laboratory test results, including, procalcitonin, C-reactive protein (CRP), white blood cell count, Clostridium difficile toxin, and interleukin-6 (IL-6) test results, were collected from the patients. Alterations in the gut microbiota of the patients were evaluated through amplicon sequencing.

In comparison to the control group, the probiotic group exhibited a notable decrease in the frequency of prolonged hospital stays, although there were no significant variances observed in terms of mortality rate, duration of fever, diarrhoea and constipation. Following probiotic treatment, there was a vital drop in procalcitonin, CRP, PSI, and white blood cell count compared to pre-treatment levels. Additionally, the probiotic group demonstrated improved clinical effectiveness in terms of antibiotic treatment duration. Analysis of the gut microbiota indicated a notable surge in the prevalence of opportunistic pathogens, such as Massilia, at the genus level within the control group. However, a significant rise in Erysipelotrichaceae_ge was observed subsequent to the administration of probiotics.

During antibiotic treatment, the control group experienced an escalation in opportunistic pathogens like Citrobacter and Massilia. Probiotic interventions were found to impede the proliferation of opportunistic pathogens. Furthermore, it was discovered that the population of butyrate-producing bacteria, exemplified by Ruminococcaceae UCG-005, expanded following probiotic therapy. Hence, oral probiotic treatment in severe pneumonia patients can reduce hospital stay and inflammation, with a favorable shift in gut microbiota towards beneficial bacteria and decreased opportunistic pathogens.