Role of bacterial virulence factors and host factors in the outcome of Escherichia coli bacteraemia

In a study of the role of virulence factors in the outcome of Escherichia c oli bacteraemia, blood isolates from 30 hospitalised patients were characte rised with regard to O and K antigens, P and type 1 fimbriae. haemolysin pr oduction, cytonecrotising factor 1 production, serum resistance, ability to activate neutrophils and resistance to killing. Patients were analysed to identify host factors contributing to morbidity and mortality. In univariat e analyses the presence of a K antigen, type 1 fimbriae. absence of haemoly sin production, serum resistance and resistance to killing were associated with morbidity and mortality. In multivariate analyses only the absence of haemolysin production was associated with morbidity and mortality, after ta king host factors into account. These preliminary findings suggest that hos t factors override bacterial virulence factors in determining the course of Escherichia coli bacteraemia. The negative association between haemolysin production and clinical deterioration during Escherichia coli bacteraemia m ight indicate predominance of less virulent strains in patients with other risk factors for morbidity and mortality or inactivation of neutrophil prod ucts needed for host defence.