USDA Creates Two Systems for Counting Pathogens

06/11/06 Recognizing that there were no reliable methods to count pathogens in samples collected from beef-processing plants, a team of researchers at the U.S. Department of Agriculture’s Agriculture Research Service (ARS) developed two methods for counting bacterial pathogens – on cattle hides and carcasses and in feces and ground beef.

According to an ARS news release, in addition to enabling beef processors to evaluate the effectiveness of the methods they’ve adopted to reduce pathogen levels, the counting – or enumeration – system provides information that can be used for making risk assessments for public health.

One of the enumeration methods that the research team – led by Dr. Mohammad Koohmaraie -- at the ARS Meat Animal Research Center (MARC) developed uses a “spiral plater,” a special instrument that is similar to a Petri dish on a turntable. Spiral plating works best on samples where a high pathogen load could be expected, such as fecal matter or hides. The test uses a calibrated syringe to distribute the sample through a stylus onto an agar plate. The plate rotates as the stylus distributes the sample from the center of the plate to the edges.

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