Pathogenic factors in mixed infection due to Bacteroides fragilis and other species of bacteria in mice
Miyazaki, S.; Ishii, T.; Tsuji, A.; Kitaya, S.; Kaneko, Y.; Ogawa, M.; Goto, S.
Nihon Saikingaku Zasshi. Japanese Journal of Bacteriology 41(3): 611-617
1986
ISSN/ISBN: 0021-4930 PMID: 3528556 Document Number: 281978
The present study was undertaken to see whether the virulence of Bacteroides fragilis is enhanced by mixed infection with Escherichia coli. 1. Acceleration of growth of B. fragilis in mixed culture B. fragilis GM7004 (102 CFU/ml) inoculated alone into nutrient broth did not grow at 37.degree. C for 24 hrs. When cultured under the same conditions with 102 CFU/ml of E. coli No. 94, the bacterial cell population increased to 108 CFU/ml or more. This increase was attributed to consumption of the medium-dissolved oxygen by proliferating E. coli and a decreased oxidation-reduction (O-R) potential. B. fragilis GM7004 did not grow in the presence of Pseudomonas aeruginosa E7 and, in this case, O-R potential did not decline though the dissolved oxygen was consumed. Furthermore, O-R potential of both intraperitoneal fluid and serum declined with time when E. coli No. 94 was used for the mixed infection with B. fragilis GM7004. 2. Enhancement of virulence of B. fragilis in mixed infection. When mice were challenged intraperitoneally with a combination of B. fragilis GM7004 and E. coli No. 94 or P. aeruginosa E7, both of which have high superoxide dismutase (SOD) and catalase activities, the virulence of B. fragilis was markedly enhanced in both experiments. On the other hand, the mixed infection with B. fragilis GM7004 and E. coli JC-2 or P. aeruginosa IFO3445, both of which have low SOD and catalase activities, did not enhance the virulence under the same conditions. From the results, it is considered that the pathogenicity of B. fragilis is enhanced in the mixed infection with other species which have the capacity of declining O-R potential in the infected site and high SOD and catalase activities.