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Translocated intestinal bacteria cause spontaneous bacterial peritonitis in cirrhotic rats: molecular epidemiologic
J M Llovet1, R Bartolí, F March
1Department of Gastroenterology, Hospital Universitari Germans Trias i Pujol, Badalona, Catalonia, Spain.
Background/Aims:
Intestinal bacterial translocation is common in cirrhotic rats with spontaneous bacterial peritonitis, and it is thought to play a major pathogenic role. There has so far been no evidence for clonality between bacteria isolated from intestine and ascites. This study aimed to use molecular epidemiology techniques to show that spontaneous bacterial peritonitis is due to translocated intestinal bacteria.
Methods:
Samples of ascitic fluid, portal blood, mesenteric lymph nodes and ileal contents from healthy (n=10) and ascitic cirrhotic rats with (n=12) or without (n=15) spontaneous bacterial peritonitis were cultured. In six infected rats, DNA macrorestriction fragments of 30 bacterial isolates [Escherichia coli (n=13), Enterococcus faecalis (n=12) and Proteus mirabilis (n=5)] from ascites (n=8), mesenteric lymph nodes (n=7), portal blood (n=6), and ileal flora (n=9) were compared.
Results:
Bacterial translocation was more frequent in animals with (58%) than in those without spontaneous bacterial peritonitis (20%, p=0.049) or controls (10%, p=0.026). The same bacterial strain was simultaneously isolated in ascites and in mesenteric lymph nodes and/or ileum in 7/8 (87%) instances. The identity rate for bacteria present in both ascites and mesenteric lymph nodes was 80% (4/5). Likewise, identity was demonstrated in 3/4 instances of bacteria found in both ascites and portal blood.
Conclusions:
These results indicate that spontaneous bacterial peritonitis in cirrhotic rats is mainly due to intestinal bacteria translocated to mesenteric lymph nodes. Portal blood could be a less frequent route.
Insights
Spontaneous bacterial peritonitis in cirrhotic rats is primarily caused by intestinal bacteria translocating to mesenteric lymph nodes. This study used molecular methods to confirm the intestinal origin of bacteria in ascites, highlighting a key pathogenic pathway.
Area of Science:
- Gastroenterology and Hepatology
- Infectious Diseases
- Microbiology
Background:
- Intestinal bacterial translocation is a common complication in cirrhotic rats with spontaneous bacterial peritonitis (SBP).
- The pathogenic role of bacterial translocation in SBP is suspected but direct evidence linking intestinal bacteria to SBP has been lacking.
- Molecular epidemiology techniques have not been previously used to establish clonality between intestinal and ascites bacteria in this model.
Purpose of the Study:
- To investigate the origin of bacteria causing spontaneous bacterial peritonitis in cirrhotic rats.
- To demonstrate that SBP is a consequence of intestinal bacteria translocating to the peritoneal cavity.
- To utilize molecular epidemiology to confirm clonality between intestinal flora and bacteria isolated from ascites and other internal sites.
Main Methods:
- Cultured samples from ascitic fluid, portal blood, mesenteric lymph nodes, and ileal contents of healthy and cirrhotic rats (with or without SBP).
- Compared DNA macrorestriction fragments of bacterial isolates (Escherichia coli, Enterococcus faecalis, Proteus mirabilis) from ascites, mesenteric lymph nodes, portal blood, and ileal flora in infected rats.
- Analyzed bacterial strains for clonality using molecular techniques.
Main Results:
- Bacterial translocation was significantly more frequent in rats with SBP (58%) compared to those without (20%) or controls (10%).
- The same bacterial strain was identified in ascites and mesenteric lymph nodes/ileum in 87% of cases.
- High identity rates (80% and 75%) were observed for bacteria found simultaneously in ascites and mesenteric lymph nodes or portal blood, respectively.
Conclusions:
- Spontaneous bacterial peritonitis in cirrhotic rats is predominantly caused by intestinal bacteria translocated via mesenteric lymph nodes.
- Mesenteric lymph nodes serve as a primary conduit for bacterial translocation leading to SBP.
- Portal blood represents a less common, but possible, route for bacterial translocation in this condition.