Changes in incidence and aetiology of bacteraemia arising in hospital practice.

Since the introduction of antibiotic therapy many authors have recorded an increased incidence of bacteraemia arising in hospital practice. Emphasis has been placed on a marked rise in staphylococcal and Gram-negative bacteraemia, with a concomi-tant fall in potentially fatal infections due to the pneumococcus and Streptococcus pyogenes (Finland et al., 1959 ; Rogers, 1959; Faber et al., 1960). Factors other than antibiotics are involved in these changes; McHenry et al. (1962a) listed the ageing population, the widespread use of precipitating surgical and instrumental procedures, the prolongation of life in seriously ill patients with limited ability to resist infection, and the use of immune-suppressing drugs as factors in the increase of Gram-negative bacteraemia. This report reviews the experience of bacteraemia at Hammersmith Hospital over the past eight years, and assesses some factors involved in an increasing incidence. surveyed, and cases having potentially pathogenic organisms isolated from two or more consecutive blood cultures were accepted for further study. Solitary blood cultures were accepted as positive if a pure growth of a recognized pathogen was present in all bottles. Blood cultures were inoculated into two Castaneda bottles (Ruiz Castaneda, 1947) containing glucose broth with added " liquoid " and penicillinase, and into a bottle of cooked meat broth for the isolation of anaerobic organisms. Cultures were examined for a minimum period of 10 days. Besides the limitations of a retrospective study some of our findings are biased by the numbers of patients referred to this centre with uraemia, blood dyscrasia, and malignant disease. Results During the period of this study there were 316 patients with positive blood cultures, Gram-negative rods accounting for 128 while the average number of blood cultures taken from a suspected case rose from 2.0 to 3.7. Table I lists the annual number of positive blood cultures according to the causative organisms, and shows a progressive rise in all bacteraemia, with a sudden increase in the isolation of Gram-negative rods in 1960. During this period no particular species of Gram-negative bacterium has become predominant , nor has the average age of the infected patients risen. Gram-negative rods 8 8 15 15 19 20 19 24 128 Staph. aureus 9 5 7 7 10 10 13 1 2 73 ,albus 0 0 1 1 0 1 2 3 8 Haemolytic 1 streptococci 0 1 1 2 1 3 4 2 11 Enterococci 1 2 3 2 3. 4 6 3 24 …