The causative organisms of septicaemia and their epidemiology.

During the 20 years, 1969-88, nearly 4000 episodes of septicaemia were studied prospectively at St. Thomas' Hospital. Forty percent were community-acquired and 60% hospital-acquired. Overall the commonest isolate was Escherichia coli (22%). In community-acquired bacteraemias, Esch. coli, Streptococcus pneumoniae and Staphylococcus aureus accounted for almost 60% of episodes, and the commonest foci of infection were the urinary tract (Esch. coli) and the respiratory tract (Str. pneumoniae). Esch. coli was particularly common in diabetic patients and Str. pneumoniae in alcoholics. In hospital-acquired septicaemia, Esch. coli and Staph. aureus accounted for 40% of episodes, but a further 30% were caused by enterobacteria other than Esch. coli, and Pseudomonas aeruginosa. The commonest foci of infection were the urinary tract, often with catheterization or instrumentation, and intravascular access sites, from which episodes of septicaemia were increasingly caused by coagulase-negative staphylococci.