Clostridium difficile infection and composition of gut microbiota in hospitalized elderly: case-control study

Objectives– To compare the composition of gut microbiota in hospitalized elderly with and without Clostridium difficile infection (CDI). Methods– 31 patients who developed CDI during hospital stay, 40 CDI-negative matched inpatients under antibiotic treatment and 36 CDI-negative matched inpatients without antibiotic were consecutively enrolled (107 subjects, 53 M, age 81±9). A fecal sample was obtained for each participant under controlled dietary regimen, and subsequently processed for microbiota DNA extraction through a culture-independent polymerase-chain reaction approach. Partial sequencing of 16S rRNA gene and subsequent amplification were carried out to allow DNA concentration calculation and taxonomic classification of microbiota composition. Results- As compared to CDI-negative patients, in silico analyses revealed a marked decrease in microbial diversity and species richness in CDI-positive patients, mainly due to a paucity of phylotypes within the Bacteroides phylum. The Firmicutes/Bacteroides ratio was increased significantly in patients with CDI but not in controls, possibly indicating a close association between CDI and faecal microbiota dysbiosis. CDI was also associated to depletion of normally abundant gut commensal organisms, such as the Ruminococcaceae, Bacteroidaceae and Lachnospiraceae families. In controls, antibiotic treatment was associated to a higher degree of fecal microbiota dysbiosis than no-antibiotic group, although much less significant than in CDI subjects. Conclusions- In hospitalized elderly, CDI development is associated to significant alterations of gut microbiota composition. A better understanding of these issues could prompt new strategies of bacteriotherapy for both prevention and treatment of CDI.