Detection of micro-organisms using a two bottle blood culture system: a twelve month study.

Over a twelve month period the isolation rate of pathogens, frequency of isolation of non-significant organisms, and time taken to detect positive cultures from a two-bottle blood culture system were analysed. Of 6916 blood cultures collected, 978 organisms were isolated from 863 cultures, 540 organisms being considered clinically significant and the majority (81%) being isolated within 48 h. Our results showed that use of more than one bottle increased the general isolation rate, with both bottles facilitating growth independently. This situation was particularly apparent in the cases of Haemophilus influenzae and Neisseria meningitidis, which showed that using the system alone only 76% and 33% (respectively) of the total number of strains would have been isolated. The results of this study reinforce the need for a second bottle containing a suitable culture medium.