Anthrax Test by Army and CDC Receives FDA Approval

Photo: Bacillus anthracis under microscope

The test, known as the Gamma Phage Assay, was modified by scientists at the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) to improve its performance and reliability when used with clinical specimens. The original form of the Gamma Phage Assay was first developed by the Centers for Disease Control and Prevention (CDC) in the mid-1950s.

The modified gamma phage method is the first diagnostic test to gain FDA approval for human use within the Laboratory Response Network (LRN). This network, established by the CDC, is charged with maintaining an integrated system of state and local public health, federal, military, and international laboratories that can respond to bioterrorism, chemical terrorism and other public health emergencies.

According to USAMRIID senior scientist John W. Ezzell, the Gamma Phage Assay is a classical bacteriological method that has been used at USAMRIID and other laboratories for years as part of an extensive array of methods used to identify B. anthracis. The gamma phage is a virus capable of entering bacterial cells and causing cell destruction, or lysis - and it is specific to B. anthracis.

"Because of that specificity, the gamma phage gives a highly readable result," Ezzell explained. "Wherever the virus is added to the surface of a culture plate that has been inoculated with suspicious anthrax colony growth, you can see clear zones where the B. anthracis cells have been destroyed - whereas other bacterial cells grow unaffected."

"This is a big first step in helping to provide the LRN labs with FDA cleared assays," said Judy Sheldon, a regulatory affairs microbiologist with the CDC's Bioterrorism Preparedness and Response Program. "The work done at USAMRIID and here at CDC provided a solid scientific basis for FDA to evaluate the assay performance. This work has set a high bar for other tests to meet."; Source: U.S. Army Medical Research Institute of Infectious Diseases