Brucella detection in blood: comparison of the BacT/Alert standard aerobicbottle, 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-FAN Ae) (the charcoal component of the FANAe was revised recently to improve th e feasibility of Gram smear interpretation) blood culture bottles for BacT/ Alert system for the detection of Brucella melitensis in simulated blood cu lture. Triplicate strains of eight clinical isolates of B. melitensis were studied. Each bottle was inoculated with 5 mL of freshly collected human bl ood at three different targeted bacterial inocula (10(1), 10(2) and 10(3) C FU/bottle). All bottles were monitored for up to 21 days or until they beca me positive. The results of time to detection (TTD) on the eight B. meliten sis samples were as follows: at 10(1) CFU/bottle, the E-FANAe had a mean TT D significantly shorter than the StAe (48 h vs. 56.2 h, P < 0.05); and at 1 0(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 reproducibilitie s (no.of positive signals/no.of all bottles) of three bottle systems were a s 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 reproduci bilities of StAe, FANAe and E-FANAe were 95, 95 and 91%, respectively. Posi tive 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 brucello sis, the combination of one StAe bottle and one E-FANAe bottle seems to pro vide the highest and fastest recovery of the organism.