Clostridium difficile toxins may augment bacterial penetration of intestinal epithelium.
BACKGROUND
Clostridium difficile can be recovered from many high-risk hospitalized patients receiving broad-spectrum antibiotic therapy. Clostridium difficile toxins A and B have been associated with increased intestinal permeability in vitro and there is growing evidence that increased intestinal permeability may be a common mechanism whereby enteric bacteria penetrate the intestinal epithelium.


OBJECTIVE
Clostridium difficile-induced alterations in the intestinal barrier facilitate microbial penetration of the intestinal epithelium, which in turn facilitates the translocation of intestinal bacteria.


METHODS
Mature Caco-2 enterocytes were pretreated with varying concentrations of toxin A or toxin B followed by 1 hour of incubation with pure cultures of either Salmonella typhimurium, Escherichia coli, or Proteus mirabilis. The effects of toxins A and B on enterocyte viability, cytoskeletal actin, and ultrastructural topography were assessed using vital dyes, fluorescein-labeled phalloidin, and scanning electron microscopy, respectively. The toxins' effects on bacterial adherence and bacterial internalization by cultured enterocytes were assessed using enzyme-linked immunosorbent assay and quantitative culture, respectively. Epithelial permeability was assessed by changes in transepithelial electrical resistance and by quantifying paracellular bacterial movement through Caco-2 enterocytes cultivated on permeable supports.


RESULTS
Neither toxin A nor toxin B had a measurable effect on the numbers of enteric bacteria internalized by Caco-2 enterocytes; however, both toxins were associated with alterations in enterocyte actin, decreased transepithelial electrical resistance, and increased bacterial adherence and paracellular transmigration.


CONCLUSIONS
Clostridium difficile toxins A or B may facilitate bacterial adherence and penetration of the intestinal epithelial barrier.
Feltis
B A
BA
Department of Surgery, University of Minnesota, Minneapolis 55455, USA. felti001@tc.umn.edu
Kim
A S
AS
Kinneberg
K M
KM
Lyerly
D L
DL
Wilkins
T D
TD
Erlandsen
S L
SL
Wells
C L
CL
D001422:Bacterial Adhesion; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D018988:Bacterial Translocation / Q000502:physiology*; D016360:Clostridioides difficile / Q000502:physiology*; D020895:Enterocytes / Q000502:physiology / Q000648:ultrastructure; D004768:Enterotoxins / Q000502:physiology*; D006801:Humans; D007413:Intestinal Mucosa / Q000382:microbiology*
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004768:Enterotoxins; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile