Clostridium difficile carriage in elderly subjects and associated changes in the intestinal microbiota

Abstract

Clostridium difficile is an important nosocomial pathogen associated particularly with diarrheal disease in elderly individuals in hospitals and long-term care facilities. We examined the carriage rate of Clostridium difficile by culture as a function of fecal microbiota composition in elderly subjects recruited from the community, including outpatient, short-term respite, and long-term hospital stay subjects. The carriage rate ranged from 1.6% (n = 123) for subjects in the community, to 9.5% (n = 43) in outpatient settings, and increasing to 21% (n = 151) for patients in short- or long-term care in hospital. The dominant 072 ribotype was carried by 43% (12/28) of subjects, while the hypervirulent strain R027 (B1/NAP1/027) was isolated from 3 subjects (11%), 2 of whom displayed C. difficile associated diarrhea (CDAD) symptoms at the time of sampling. Emerging ribotypes with enhanced virulence (078 and 018) were also isolated from two asymptomatic subjects. Pyrosequencing of rRNA gene amplicons was used to determine the composition of the fecal microbiota as a surrogate for the microbial population structure of the distal intestine. Asymptomatic subjects (n = 20) from whom C. difficile was isolated showed no dramatic difference at the phylum or family taxonomic level compared to those that were culture negative (n = 252). However, in contrast, a marked reduction in microbial diversity at genus level was observed in patients who had been diagnosed with CDAD at the time of sampling and from whom C. difficile R027 was isolated.

Fig 1

Bar chart of interindividual variability of C. difficile-negative (A) and C. difficile-positive (B) subjects. The color-coding is defined at the bottom of the figure.

Fig 2

Family level assignments of gut communities of C. difficile culture-positive subjects (A [n = 22]) compared to C. difficile culture-negative controls (B [n = 252]) expressed as a percentage of assignable tags.

Fig 3

Genus level assignments of gut communities in 252 C. difficile-negative subjects (A), 18 asymptomatic carriers of C. difficile (B), individual subjects with previous documented incidence of C. difficile infection (C and D), and individual subjects with active C. difficile infection at the time of sampling (E and F).

Fig 4

MEGAN comparison of three (EM011, EM304, and EM306) subjects harboring C. difficile strain R027. This MEGAN illustration provides a comparison view in which each node shows the number of reads assigned to it for each of the data sets. Pie charts at each node display the relative abundance for each taxonomic level. Reads are assigned according to BLAST assignments. EM304 and EM306 were diagnosed with CDAD at the time of sampling. EM3011 was an asymptomatic carrier with no history of CDAD.