Brucella detection in blood: comparison of the BacT/Alert standard aerobic bottle, BacT/Alert FAN aerobic bottle and BacT/Alert enhanced FAN aerobic bottle in simulated blood culture

The objective of this study was to compare the performances of the standard aerobic bottle (StAe), FAN aerobic (FANAe) and enhanced FAN aerobic (E-FANAe) (the charcoal component of the FANAe was revised recently to improve the feasibility of Gram smear interpretation) blood culture bottles for BacT/Alert system for the detection of Brucella melitensis in simulated blood culture. Triplicate strains of eight clinical isolates of B. melitensis were studied. Each bottle was inoculated with 5 mL of freshly collected human blood at three different targeted bacterial inocula (10(1), 10(2) and 10(3) CFU/bottle). All bottles were monitored for up to 21 days or until they became positive. The results of time to detection (TTD) on the eight B. melitensis samples were as follows: at 10(1) CFU/bottle, the E-FANAe had a mean TTD significantly shorter than the StAe (48 h vs. 56.2 h, P < 0.05); and at 10(3) CFU/bottle, the FANAe and E-FANAe had a mean TTD significantly shorter than the StAe (41.2 h and 40 h vs. 45.6 h, P < 0.05). The reproducibilities (no.of positive signals/no.of all bottles) of three bottle systems were as follows: at 10(1) CFU/bottle, the reproducibilities of StAe, FANAe and E-FANAe were 96, 83 and 58%, respectively. At 10(3) CFU/bottle, the reproducibilities of StAe, FANAe and E-FANAe were 95, 95 and 91%, respectively. Positive results for the presence of bacteria in Gram smears were confirmed in 68% of StAe, 54% of FANAe and 90% of E-FANAe. In case of suspected brucellosis, the combination of one StAe bottle and one E-FANAe bottle seems to provide the highest and fastest recovery of the organism