`Fingerprints' For Food Poisoning

MILLIONS OF PEOPLE FALL ill each year from salmonella and other bacterial pests. In one outbreak in the mid-1980s, listeria in Mexican cheese killed 47 Californians. Tests to detect the bugs exist, but they're time-consuming and inexact.

DuPont Co. is developing new technologies that could help. The company's RiboPrinter, which went on sale to food-processing companies earlier this year for $175,000, scans a colony of bacteria taken from a food sample, extracts a DNA "fingerprint" through a technique called electrophoresis, and compares it in a computer with hundreds of similar bacterial patterns. The old way of identifying bacteria involved culling samples, growing them in lab dishes, and studying their behavior--a routine that took up to five days. The RiboPrinter can do it in as little as eight hours and also helps tell if the bugs snuck in through raw food materials or spread from contaminated processing equipment, says DuPont scientist Scott L. Rakestraw.

DuPont's gene sleuths will now go a step further. They have begun to commercialize a variant of polymerase chain reaction (PCR)--made famous in the O.J. Simpson trial--that can quickly multiply minute quantities of suspect bacterial DNA fragments on food samples. For just $10 per test, the technology, which DuPont licensed from Hoffmann-LaRoche Inc. and Perkin-Elmer Corp., can positively identify traces of salmonella in one day. Similar tests for troubling types of E. coli and listeria are under development.

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