The role of Escherichia coli haemolysin in the pathogenic synergy of colonic bacteria in subcutaneous abscess formation in mice.

The growth of nine species of colonic bacteria--Escherichia coli, Enterococcus faecalis, Bacteroides ovatus, Fusobacterium varium, Clostridium perfringens, Klebsiella pneumoniae, Proteus vulgaris, Staphylococcus aureus and Bifidobacterium adolescentis--was examined after concomitant injection to form experimental subcutaneous abscesses in mice. Injection of a mixture of c. 10(5) cfu of each of the first five strains (E. coli, Ent. faecalis, B. ovatis, F. varium and C. perfringens) resulted in abscess formation in all mice tested when the E. coli strain was haemolytic. E. coli and B. ovatus multiplied and reached a maximum population of c. 10(8) cfu/abscess. When non-haemolytic E. coli was used, injection of greater than or equal to 10(7) cfu was required for abscess formation. The inclusion of partially purified E. coli haemolysin (125 HU50) with c. 10(5) cfu of bacteria including non-haemolytic E. coli resulted in abscess formation in most mice tested. These results indicate that E. coli haemolysin is one factor that may potentiate pathogenic synergy among colonic bacteria especially between E. coli and B. ovatus, during abscess formation.