DEVELOPMENT OF O.A.S.I.S., A NEW AUTOMATED BLOOD CULTURE SYSTEM IN WHICH DETECTION IS BASED ON MEASUREMENT OF BOTTLE HEADSPACE PRESSURE CHANGES

o.a.s.i.s. (Unipath Ltd., Basingstoke, United Kingdom) is a new automa ted blood culture system. The metabolism of microorganisms is detected by measuring changes in the pressure of the headspace of blood cultur e bottles. These changes are measured by monitoring the position of a flexible sealing septum, every 5 min, with a scanning laser sensor. Th is noninvasive system can detect both gas absorption and production an d does not rely solely on measuring increasing carbon dioxide levels. A research prototype instrument was used to carry out an evaluation of the media, the detection system, and its associated detection algorit hm. In simulated blood cultures, o.a.s.i.s. supported growth and detec ted a range of clinical isolates. Times to positivity were significant ly shorter in o.a.s.i.s. than in the BACTEC 460 system. Results of a c linical feasibility study, with a manual blood culture system as a con trol, confirmed that o.a.s.i.s. was able to support the growth and det ection of a variety of clinically significant organisms. On the basis of these findings, full-scale comparative clinical trials of o.a.s.i.s . with other automated blood culture systems are warranted.