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1 – Introduction
1.1 Intended Use
The BD BACTEC™ FX instrument is designed for the rapid detection of bacteria and fungi in clinical
specimens, blood, and blood products. Samples are drawn from patients or bagged blood/blood
products and injected directly into BD
BACTEC culture vials, which are placed into the instrument for
incubation and testing.
1.2 Principles of the Procedure
When microorganisms are present in culture vials, they metabolize nutrients in the culture medium,
releasing carbon dioxide into the medium. A dye in the sensor at the bottom of the vial reacts with
CO
2
. This modulates the amount of light that is absorbed by a fluorescent material in the sensor. A
photo detector at each station measures the level of fluorescence, which corresponds to the amount of
CO
2
released by organisms. Then the measurement is interpreted by the system according to
preprogrammed positivity parameters.
At system start-up, the onboard computer performs self-diagnostics and downloads operating
instructions to the drawer rows. Then the instrument(s) automatically begin testing. Light Emitting
Diodes (LEDs) behind the vials illuminate the rows, activating the vials’ fluorescent sensors. After a
warm-up period, the instrument’s photo detectors then take the readings. A test cycle of all rows is
completed every ten minutes. Positive cultures are immediately flagged by an indicator light on the
front of the instrument, an audible alarm, and are displayed on the LCD display.
When positive vials are identified, the lab technologist pulls them from the instrument for confirmation
of results, and for isolation and identification of the organism.
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