Comparison of the Isolator 1.5 Microbial Tube with a conventional blood culture broth system for detection of bacteremia in children.

A lysis direct plating technique, utilizing the Isolator 1.5 Microbial Tube (Du Pont Company) was compared to a conventional two-bottle culture system during a prospective study conducted in a children's hospital. Specimens were processed so that the amounts of blood allocated to each conventional blood culture bottle and the Isolator tube were as equivalent as possible. Of the 1,823 specimens enrolled, 93 (5.1%) yielded growth of 102 clinically significant isolates. Lysis direct plating and conventional blood culture bottles detected 85 and 89 of the isolates, respectively. No statistically significant differences were observed between the two methods in the overall efficiency of organism recovery or in the detection of any specific organism. Contamination rates during the entire study were 14.1% and 3.6% for lysis direct plating and conventional blood culture bottles, respectively. The mean time to availability of colonies of clinically significant isolates from specimens positive by both methods was 29 hr and 35 hr for lysis direct plating and conventional blood culture bottles, respectively. We conclude that lysis direct plating offers an attractive alternative to conventional blood culture bottles for the processing of blood cultures from pediatric patients.