M. Sparrius

Pathogenic synergy between Escherichia coli and Bacteroides fragilis or B. vulgatus in experimental infections: a non-specific phenomenon.

The virulence of Bacteroides fragilis and B. vulgatus for mice was compared in a skin-infection model. These strains were also tested for pathogenic synergy in mixed infections with Escherichia coli. Strains of B. fragilis were generally more virulent than strains of B. vulgatus and, with one exception, the effect of Bacteroides strains in mixed infections merely reflected their inherent virulence.

K ANTIGENS OF ESCHERICHIA COLI AND VIRULENCE IN URINARY-TRACT INFECTION: STUDIES IN A MOUSE MODEL

The importance of K antigens of Escherichia coli as virulence factors was studied by comparing groups of mice given either strains of E. coli isolated from urinary tract infection in humans or mutant strains differing only in the absence of the K antigen. K antigens proved to be of minor importance for mouse nephropathogenicity; however, with the exception of the K(A) antigen, they contributed substantially to deaths attributed to more general infection. Possible mechanisms for the virulence of strains with K antigens are discussed in terms of the bactericidal effect of serum and phagocytosis.

Pathogenic synergy between Escherichia coli and Bacteroides fragilis: studies in an experimental mouse model

An animal model is described for quantitative evaluation of pathogenic synergy between Escherichia coli and Bacteroides fragilis in which adjuvants were not required for abscess formation. Two sets of strains of E. coli and B. fragilis isolated from human wound infections were tested. Pathogenic synergy was observed in only one of the two combinations and was dependent on properties of E. coli.

Influence of rosmarinic acid on opsonization and intracellular killing ofEschericha coli andStaphylococcus aureus by porcine and human polymorphonuclear leucocytes

The influence of rosmarinic acid on the function of porcine and human polymorphonuclear leucocytes was tested. Rosmarinic acid inhibited the chemiluminescence of PMNL, induced by preopsonized Zymosan or phorbol myristate acetate. The killing ofEscherichia coli was inhibited by rosmarinic acid at a concentration of 2 mM, but not that ofStaphylococcus aureus. The inhibition of the killing was due to an impaired opsonization, caused by an adverse influence of rosmarinic acid on complement activation. Direct effects of rosmarinic acid on the killing mechanisms of PMNL were not observed.

The role of different K antigens of Escherichia coli in phagocytosis by polymorphonuclear leukocytes

The importance of K antigens from six strains of Escherichia coli for the interaction with polymorphonuclear leukocytes (PMNL) was studied. The major factor influencing this interaction was the ability of strains to activate complement by the classical route during opsonisation, this process being reduced for most K-positive strains. Interference of K antigens with the functioning of common pili as adhesions of eukaryotic cells was not observed nor a toxic effect of K antigens on PMNL.

Loss of viability ofBacteroides fragilis andBacteroides vulgatus in different media

(The antiserum was prepared against isolate 25862 because the reference strain was delayed for several months.) The antiserum revealed two antigens in the LiC1 extracted preparation of the homologous strain (25862) and two antigens as well in strain 15883. One was definitely identical, the other probably, to the corresponding antigens of isolate 25862. The reference strain (100113)yielded only one line of partial identity to the major antigen of isolates 25862 and 15883. This serological diversity of different strains of the same Neisseria species is a well known phenomenon. Neisseria flavescens and Neisseria sicca differed from the reference strain of Neisseria polysacchareae and our isolates by sugar degradation (with the exception of strain 15883 which behaved like Neisseria sicca), the lectin agglutination spectrum (under identical conditions they were agglutinated only by the lectin of Limax flavus), the pigment curve (peaks at 3 4 0 341, 356 and 376 nm, pigment group II (5)) and serology (minor cross-reactions in gel precipitation, no lines of identity).