A review of positive blood cultures: identification and source of microorganisms and patterns of sensitivity to antibiotics.

All strains of bacteria and fungi isolated from blood cultures of patients hospitalized in a large primary and tertiary care center were studied prospectively for determination of their clinical significance and probable source. In some instances the immediate mortality rate was also determined. The sensitivity patterns of all aerobic organisms to antibiotics were studied in relation to the role of antibiotic therapy. A positive culture was obtained from 6.8% of all blood specimens cultured and these positive cultures represented 639 episodes of bacteremia or fungemia. The organism isolated most of ten was Escherichia coli, and the most common known source was the urinary tract. Anaerobic organisms were isolated from 9.2% of the episodes of bacteremia, with the bowel being the most common probable source of infection. Antibiotic sensitivity testing revealed that all staphylococci were sensitive to methicillin, but only 22% were sensitive to penicillin. No penicillin-resistant pneumococci were encountered. The Enterobacteriaceae exhibited such a high sensitivity to gentamicin that comparison of its activity with that of other, newer aminoglycosides was impossible.