Recurrence of dual-strain Clostridium difficile infection in an in vitro human gut model.
BACKGROUND
Clostridium difficile infection (CDI) is still a major challenge to healthcare facilities. The detection of multiple C. difficile strains has been reported in some patient samples during initial and recurrent CDI episodes. However, the behaviour of individual strains and their contribution to symptomatic disease is unclear.


METHODS
An in vitro human gut model was used to investigate the germination and proliferation of two distinct C. difficile strains during initial and recurrent simulated CDI, as well as their response to vancomycin treatment. The gut model was inoculated with a pooled human faecal emulsion and indigenous gut microbiota, C. difficile populations (vegetative and spore forms), cytotoxin levels and antimicrobial activity were monitored throughout the experiment.


RESULTS
Both C. difficile strains germinated and proliferated in response to ceftriaxone instillation, with cytotoxin detected during the peak vegetative growth. Vancomycin instillation resulted in a rapid decline in the vegetative forms of both strains, with only spores remaining 2 days after the start of dosing. A recrudescence of both strains occurred following the cessation of vancomycin installation, although this was observed more quickly, and to a greater extent, in one strain than the other.


CONCLUSIONS
Within a human gut model, multiple C. difficile strains are able to germinate and proliferate concurrently in response to antibiotic challenge (the onset of simulated CDI). Similarly, more than one strain can proliferate during simulated recurrent CDI, although with differences in germination and growth rate and timing. It appears probable that multiple strains can contribute to CDI within an individual patient, with possible implications for management and bacterial transmission.
Leeds Institute of Biomedical and Clinical Sciences, Faculty of Medicine and Health, University of Leeds, Leeds, UK.
Grace S
GS
Crowther
Leeds Institute of Biomedical and Clinical Sciences, Faculty of Medicine and Health, University of Leeds, Leeds, UK.
Caroline H
CH
Chilton
Leeds Institute of Biomedical and Clinical Sciences, Faculty of Medicine and Health, University of Leeds, Leeds, UK.
Sharie L
SL
Todhunter
Leeds Institute of Biomedical and Clinical Sciences, Faculty of Medicine and Health, University of Leeds, Leeds, UK.
Scott
S
Nicholson
Department of Microbiology, Leeds Teaching Hospitals NHS Trust, The General Infirmary, Leeds, UK.
Jane
J
Freeman
Leeds Institute of Biomedical and Clinical Sciences, Faculty of Medicine and Health, University of Leeds, Leeds, UK Department of Microbiology, Leeds Teaching Hospitals NHS Trust, The General Infirmary, Leeds, UK mark.wilcox@nhs.net.
Mark H
MH
Wilcox
D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D016360:Clostridioides difficile / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification*; D003015:Clostridium Infections / Q000382:microbiology*; D041981:Gastrointestinal Tract / Q000382:microbiology*; D006801:Humans; D008875:Middle Aged; D008962:Models, Theoretical; D012008:Recurrence; D016896:Treatment Outcome; D014640:Vancomycin / Q000008:administration & dosage*
D000900:Anti-Bacterial Agents; D014640:Vancomycin
antibiotics; chemostat; mixed infections