Virulence factors and biofilm production by isolates of Bacteroides fragilis recovered from dog intestinal tracts

Bacteroides fragilis colonizes dog guts both as a commensal and as an opportunistic pathogen. This study aims to evaluate virulence factors of 13 B. fragilis strains isolated from dog intestinal tracts and their ability for biofilm formation. Capsules were detected in all the evaluated strains. A total of 61.5% of all strains were biofilm producers. These attributes most likely play an important role in B. fragilis persistent colonization in the gut.

Expression of Monocyte Chemotactic Protein-1 and Macrophage Inflammatory Protein-1alpha in Intraabdominal Abscess Induced by Bacteroides fragilis Infection

OBJECTIVE: Bacteroides fragilis is the most frequently isolated anaerobes in tissue of intraabdominal infection, particularly in intraabdominal sepsis or abscess. In acute experimental model with an intraabdominal infection, the response to B. fragilis is characterized by infiltration of neutrophils and monocytes. To understand the pathogenesis of B. fragilis infection, it is important to explore the mechanism for inflammatory signals such as chemokines induced by this bacteria. The goal of this study was to determine whether peritoneal monocytes or fibroblasts surrounding with intraabdominal abscess induced by B. fragilis could express chemokines such as monocyte chemotactic protein-1 (MCP-1) or macrophage inflammatory protein-1a (MIP-1a). METHODS: 1) After C57BL/6 mice were intraperitoneally inoculated with abscess-inducing agents containing B. fragilis, RNA was extracted from the intraperitoneal tissues of the mice using Ottawa sand and the guanidinium thiocyanate-phenol-chloroform method in 3 days later. 2) After C57BL/6 mouse peritoneal monocytes were infected with B. fragilis for 1, 4 and 9 hours, cellular RNA was extracted from the cells. 3) Fibroblasts isolated from intraabdominal abscess nodules induced by B. fragilis infection were growth in tissue culture for 3 to 4 weeks. After the fibroblasts were stimulated with IL-1alpha (0.1-10 ng/ml) or TNFalpha (0.1-10 ng/ml) for 24 hours, total cellular RNA was extracted. MCP-1 or MIP-1alpha mRNA expression was assessed using RTPCR. MCP-1 or MIP-1alpha proteins in cluture supernatants or tissue extracts were also measured by ELISA. RESULTS: 1) MCP-1 or MIP-1alpha mRNA was highly expressed in peritoneal tissue of C57BL/6 mice bearing with intraabdominal abscess induced by B. fragilis. 2) Expression of MCP-1 mRNA increased at 9 hours in mouse peritoneal monocytes infected with B. fragilis. MIP-1alpha mRNA was initially expressed and perisisted in the monocytes infected with B. fragilis for 9 hours. MCP-1 or MIP-1alpha proteins was also parallel to the expression of those chemokines. 3) The fibroblasts isolated from intraabdominal abscess nodules by B. fragilis infection constitutively expressed MCP-1, MIP-1alpha, production in the fibroblasts was significantly upregulated in response to proinflammatory cytokines produced in the monocytes, including IL-1alpha and TNFalpha, but MCP-1 production were not. The normal fibroblasts from uninfected mice didnot show significant production of MCP-1 or MIP-1a in response to IL-1a or TNFalpha. CONCLUSION: These results suggest that peritoneal monocytes and fibroblasts surrounding with abscesses induced by B. fragilis produce MCP-1 or MIP-1a. Furthermore, it could be extrapolated that those effects may play a role in the formation of intraabdominal abscess nodules.

STRUCTURAL PROPERTIES OF THE LIPID A COMPONENT OF THE LIPOPOLYSACCHARIDE (ENDOTOXIN) ISOLATED FROM BACTERIODES FRAGILIS NCTC 9343 / 第二军医大学学报

Various chemical and gas-liquid chromatographic analyses indicate that the lipid A backbone of the lipopolysaccharide (LPS) isolated from Bacteriodes fragilis NCTC 9343 is chemically constituted by a ?1, 6-interlinked D-gluco-samine disaccharide. It is phosphorylated at its 1-position by a glycosidic-linkage while the ester-bound phosphate present generally in other lipid A is depleted. The lipid A is lower fatty acylated in the amount of 5.2 fatty acids per lipid A molecule (of which 0.73 forms 3-acyloxyacyl groups). The LPS containing such a lipid A component has been shown endowing with a weaker endotoxicity.

PHYSICO-CHEMICAL CHARACTERIZATION OF THE LIPOPOLYSACCHARIDE (ENDOTOXIN) FROM BACTER10DES FRAGILIS NCTC 9343 / 第二军医大学学报

0), 3-hydroxy-15-methyl-hexadecanoic (3-OH-l5-Me-l6 : 0) and 13-methyl-tetradecanoic acid(13-Me-14 s 0).Approximately one mole of 2-keto-3-deoxy-D-mannooctonate was detected after treatment of LPS with 48% hydrofluoric acid, indicating it was present as a phosphorylated molecule.