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Intestinal bacteria translocate into experimental intra-abdominal abscesses
Abstract:
Experimental intra-abdominal abscesses were initiated by surgical implantation of a fibrin clot contaminated with either Bacteroides fragilis, Bacteroides thetaiotaomicron, or B fragilis-Escherichia coli. Seven days after surgery the numbers of bacteroides (per gram) in B fragilis and B thetaiotaomicron abscesses were typically log10 8.4 +/- 0.5 (n = 6) and log10 6.4 +/- 0.6 (n = 4), respectively; B fragilis-E coli abscesses typically contained log10 8.9 +/- 0.5 B fragilis and log10 7.6 +/- 0.6 E coli (n = 5). Of 38 B fragilis abscesses, 14 B fragilis-E coli abscesses, and nine B thetaiotaomicron abscesses, additional intestinal bacteria were recovered from 21 (55%), 13 (93%), and seven (89%) abscesses, respectively. The additional organisms, in decreasing order of frequency, were enterococci, E coli, staphylococci, alpha-streptococci, lactobacilli, and Proteus species in numbers ranging from 2.5 log10 to 7.9 log10 per gram of abscess. Histologic sections of contaminated abscesses adherent to the intestine, liver, or spleen revealed normal tissue histology and no breakdown of the abscess wall. Thus, intestinal bacteria translocated into intra-abdominal abscesses by a mechanism that did not appear to be surgical soilage.
Insights
Intra-abdominal abscesses in experiments showed significant translocation of intestinal bacteria, suggesting a mechanism beyond simple surgical contamination. This highlights a novel pathway for bacterial invasion in abdominal infections.
Area of Science:
- Microbiology
- Surgical Pathology
- Gastroenterology
Background:
- Intra-abdominal abscesses are complex infections often involving polymicrobial communities.
- The origin and translocation mechanisms of bacteria within these abscesses are not fully understood.
- Bacteroides species are common inhabitants of the gut and frequently implicated in abscess formation.
Purpose of the Study:
- To investigate the bacterial composition and translocation mechanisms in experimentally induced intra-abdominal abscesses.
- To determine the frequency and types of additional intestinal bacteria found within these abscesses.
- To explore the potential role of surgical contamination versus intrinsic translocation.
Main Methods:
- Experimental intra-abdominal abscesses were created using fibrin clots contaminated with specific bacteria (Bacteroides fragilis, Bacteroides thetaiotaomicron, Escherichia coli).
- Bacterial loads within abscesses were quantified using quantitative culture techniques seven days post-surgery.
- Histological examination of abscesses and adjacent organs was performed to assess tissue integrity and potential invasion pathways.
Main Results:
- High bacterial loads of inoculated Bacteroides species and Escherichia coli were confirmed within the abscesses.
- A significant proportion of abscesses contained additional intestinal bacteria, including enterococci and staphylococci.
- Histology revealed intact abscess walls and normal adjacent tissue, refuting direct surgical soiling as the primary translocation route.
Conclusions:
- Intestinal bacteria translocate into experimental intra-abdominal abscesses via a mechanism independent of direct surgical contamination.
- The findings suggest an intrinsic host or bacterial mechanism facilitating bacterial migration into abscess cavities.
- Further research is warranted to elucidate the precise molecular mechanisms underlying this bacterial translocation.