Routine aerobic terminal subculturing of blood cultures in a cancer hospital

Abstract

Routine terminal aerobic subcultures of macroscopically negative blood culture bottles were evaluated over 15 mo. when 30,000 blood cultures were processed. Each blood culture set consisted of a vented and an unvented 50 ml broth bottle. Forty-eight pathogens and 47 contaminants were isolated only from terminal subcultures. Of the significant isolates, 22 were yeasts (usually recovered from ventral bottles) and 10 were Pseudomonas aeruginosa (usually recovered from unvented bottles). Blood cultures that were positive by terminal subculture provided clinically relevant information in many cases, whether other blood cultures were positive or not. Microbiology laboratories, particularly those in hospitals where yeasts and P. aeruginosa are commonly isolated from blood specimens, should evaluate carefully the need for terminal subcultures of blood culture bottles before abandoning their use.