Commensal bacteria do translocate across the intestinal barrier in surgical patients.
BACKGROUND
The "gut origin of sepsis" hypothesis proposes that enteric bacteria may cause sepsis at distant extra-intestinal sites. Whilst there is much circumstantial evidence to support this hypothesis, there is no conclusive proof in humans. The nature of translocating bacteria remains unclear. The aim of this study was to establish the origin of Escherichia coli (E. coli) cultured from mesenteric lymph nodes (MLN) and determine if they belonged to any recognized pathotypes known to cause infections in humans.


METHODS
MLN and faecal samples were obtained from 98 patients undergoing colonic resection. E. coli were isolated from 9/98 MLN samples. DNA fingerprints of MLN isolates were compared with faecal isolates from the same patient. MLN isolates were tested for adherence and invasion using HEp-2 epithelial cells, and screened for DNA markers indicative of different pathotypes of E. coli. MLN isolates were also tested for internalisation into Caco-2 cells.


RESULTS
All the nine E. coli cultured from MLNs were found to have identical DNA fingerprints to at least one and often several E. coli isolates cultured from faecal samples of the same patient. 8/9 (89%) MLN isolates were weakly adherent and 2/9 (22.2%) were invasive. 8/9 (89%) tested negative for DNA markers. All the nine MLN strains were internalised by Caco-2 cells.


CONCLUSIONS
This study confirms the gut origin of translocating bacteria. Most translocating E. coli do not belong to any recognised pathotype and are therefore normal commensal microflora. Our results suggest that bacterial translocation is more dependent upon the gut epithelium rather than the virulence properties of resident enteric bacteria.
Reddy
Bala S
BS
Combined Gastroenterology Research Unit, Scarborough Hospital, Woodlands Drive, Scarborough, YO12 6QL, UK.
MacFie
John
J
Gatt
Marcel
M
Macfarlane-Smith
Louissa
L
Bitzopoulou
Kalliopi
K
Snelling
Anna M
AM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001422:Bacterial Adhesion; D018988:Bacterial Translocation; D018938:Caco-2 Cells / Q000382:microbiology; D003106:Colon / Q000382:microbiology* / Q000601:surgery*; D016172:DNA Fingerprinting; D004847:Epithelial Cells; D004926:Escherichia coli / Q000145:classification / Q000302:isolation & purification / Q000472:pathogenicity / Q000502:physiology*; D004927:Escherichia coli Infections / Q000382:microbiology*; D005243:Feces / Q000382:microbiology; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000276:immunology / Q000382:microbiology; D008198:Lymph Nodes / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies