Increased detection of polymicrobial septicaemia by repeat subculture.

Repeated subcultures were performed on 572 blood cultures that had yielded single significant organisms and 55 from which contaminants had grown. This yielded 83 more isolates from 71 patients. Only one of the contaminated blood cultures yielded a further significant isolate. Additional antibiotic therapy was indicated in only six patients. Although repeated subculture increased the detection of additional isolates, it did not help in the management of most patients.