Effect of agitation and frequent subculturing on recovery of aerobic and facultative pathogens by Roche Septi-Chek and BACTEC blood culture systems

Publisher Website
Google Scholar
Abstract
The positivity rate and time to recovery of pathogens were compared in Roche Septi-Chek (RSC-TSB) and BACTEC radiometric systems on 3,539 paired blood cultures. Both systems were steadily agitated, with frequent subculturing or processing of the RSC-TSB agar slides and BACTEC bottles, respectively, during the first 24 h of incubation. The RSC-TSB system recovered 249 pathogens (7.0% positivity rate), compared with 234 (6.6% positivity rate) isolates recovered from BACTEC. For the most common isolates, Staphylococcus aureus and the Enterobacteriaceae, the median time to detection was 15.8 h for BACTEC and 18.6 h for the RSC-TSB system. No statistically significant difference was observed in recovery of organisms from the two systems, except for S. aureus (P < 0.05). In the RSC-TSB system, 42% of S. aureus, 58% of the Enterobacteriaceae, and 45% of Pseudomonas aeruginosa isolates had sufficient growth on the agar slant to allow performance o rapid standardized identification and susceptibility studies. In comparison with other studies using static incubation, it appears that agitation and frequent subculturing of the RSC-TSB system during the first 24 h of incubation decreased the time to detection for the majority of significant blood culture isolates.