Chapter 5 : The bioMérieux BacT/Alert: Automation at Last in the Black Box

Bactec 460 schematic illustrating the complex gas flow, bottle piercing, and analysis of positivity versus the BacT/Alert. Reproduced from ( 1 ), with permission.

Original BacT/Alert media (aerobic at left and anaerobic at right) containing a disk of membrane with bound dye at their bases. Compare with the positive and negative modern emulsion bottles in Figure 3B . The bottle on the right is negative but is gassed with 2.5% CO2, which, combined with a difference in equilibrium from being bound to a membrane, results in a greenish color relative to the bottle at left in Figure 3B . The bottle at left is positive; the increase in reflected red light from the instrument’s LEDs would be interpreted as growth. Image courtesy of bioMérieux, used with permission.

(A) An array of modern BacT/Alert bottles (left to right: SA, SN, FN Plus, FA Plus, PF Plus, and MP). (B) A negative (left) and positive (right) bottle, demonstrating the dye emulsion medium and the color change detected by the BacT/Alert system. Image courtesy of bioMérieux, used with permission.

(A) Mechanism of detection of growth detection in the BacT/Alert from the original patent ( 47 ). 1, vessel; 2, sensor; 3, culture medium; 4, light source; 5, photodetector; and associated electronics including 6, current source; 7, current to voltage converter; and 8, low-pass filter. (B) BacT/Alert reflectance curves for blood with E. coli (red), blood without organisms (blue, demonstrating baseline drift), and an uninoculated bottle (yellow).

The first prototype BacT/Alert, one of two built at Durham, NC, during placement in the laboratory of Barth Reller at Duke. Left to right are James Turner (director of the Durham group), James DiGuiseppi, and Thurman Thorpe. Note the differences in the instrument compared with the production instrument in Fig. 6 . Doors evolved from clear plastic prone to light leakage and interference to clear/dark (but infrared transparent) in initial production, then opaque doors.

Larry Pope (manager of the instrument development group at Organon Teknika, where the production instrument was designed and manufactured), Thurman Thorpe, and James DiGuiseppi at the American Society for Microbiology general meeting, New Orleans, 1989, with a production model of the BacT/Alert. This instrument was produced for more than 10 years before it was succeeded by the BacT/Alert 3D system.

BacT/Alert 3D system in modular form with touchscreen and integrated bar coder (A) and the standalone BacT/Alert/3D 60 system (B). Image used with permission from bioMérieux.

(A) The BacT/Alert VIRTUO system in dual-unit format. The touchscreen at upper left can be used to automatically unload positive bottles (yellow “button” at upper right of screen), which are automatically deposited in the two slots at middle right. Bottles are robotically accessioned in groups of up to 40 at a time (center), and placed in internal racks by a robotic arm (B), allowing the bottles to be rocked (C). Negative bottles are automatically removed and placed in a waste receptacle at the bottom of each unit. Image used with permission from bioMérieux.