title: Lethal microbial synergism in intra-abdominal infections. Escherichia coli and Bacteroides fragilis.
abstract: The ability of Bacteroides fragilis and Escherichia coli to produce synergistic mortality when mixed into intraperitoneal (IP) fibrin clots was tested in rats. The addition of B fragilis (2 X 10(9) colony-forming units/clot) to E coli (2 X 10(8) colony-forming units/clot) in the clot significantly enhanced both early and late mortality rates when compared to either E coli or B fragilis alone. Multiple washings of B fragilis prior to mixing with E coli in the clot delayed the enhancement of lethality from 24 to 48 hours. By seven days, washed B fragilis was as synergistic with E coli as unwashed B fragilis plus E coli. Furthermore, unwashed killed B fragilis was as synergistic when mixed with E coli in the fibrin clot as unwashed living B fragilis. However, washed dead B fragilis plus E coli produced no greater mortality than E coli alone. The lethality of an IP clot containing E coli was significantly increased when B fragilis was mixed with it in the same clot, injected free IP, and or implanted into a separate IP clot. Intraperitoneal E coli-fibrin clot lethality was not increased by subcutaneous B fragilis and was only slightly enhanced by intravenous B fragilis inoculation. The strain of B fragilis used in these studies did not produce fibrinolysins at any concentration. The data support the idea that synergistic mortality between E coli and B fragilis in this model is caused by a heat-stable surface factor produced by B fragilis, which acts to increase the lethal effects of E coli.
authors.forename: O D
authors.initials: OD
authors.lastname: Rotstein
authors.forename: T L
authors.initials: TL
authors.lastname: Pruett
authors.forename: R L
authors.initials: RL
authors.lastname: Simmons
mesh_terms: D000038:Abscess / Q000473:pathology; D000818:Animals; D001442:Bacteroides Infections / Q000382:microbiology; D001441:Bacteroides fragilis / Q000472:pathogenicity* / Q000502:physiology; D004926:Escherichia coli / Q000472:pathogenicity* / Q000502:physiology; D004927:Escherichia coli Infections / Q000382:microbiology; D005341:Fibrinolysin / Q000096:biosynthesis; D010538:Peritonitis / Q000382:microbiology; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D014774:Virulence
chemical_list: D005341:Fibrinolysin