[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Fwd: [Fwd: [riskanal] RE: Anthrax testing]]



There has been so much interest in anthrax that the following email from

the Risk Analysis listserv seemed especially helpful regarding anthrax

testing. My thanks to Dr. Betty Jensen and the Risk Analysis

professional

Sincerely,

Maury Siskel       maury@webtexas.com

================================



-------- Original Message --------

Subject: [riskanal] RE: Anthrax testing

Date: Wed, 17 Oct 2001 09:12:21 -0400

From: "Jensen, Betty K." <Betty.Jensen@pseg.com>

Reply-To: "Jensen, Betty K." <Betty.Jensen@pseg.com>

To: "Mailing List for Risk Professionals" <riskanal@lyris.pnl.gov>



Below are excerpts from today's (10/17/2001) WSJ which sheds some light

on the issue.  You can probably get the entire article from the web.



Questions of Security: Nevada Case Illustrates Difficulty in Identifying

Anthrax --- CDC's Preliminary Tests on Microsoft Letter Are Negative,

Contradicting State Results 

By Laura Johannes and Rebecca Buckman 

  

10/17/2001 

The Wall Street Journal 

A6 



"The doubt over the Nevada case highlights the resulting confusion when

harried labs struggle with a suddenly expanded workload. It also

illustrates what some experts have been saying privately for weeks: 

Testing for anthrax isn't always a black-and-white matter. The anthrax 

bacteria, Bacillus anthracis, looks, and often behaves in tests, a lot 

like its harmless cousins, B. cereus, B. subtilis and B. thuriengensis"



"As many as a dozen tests can be needed just to determine whether

anthrax is present, let alone identify the specific strain. No single 

test alone can identify anthrax but "a decision tree with other events 

allows you to start to narrow it down," said Calvin Chue, a research 

scientist at the Johns Hopkins Center for Civilian Biodefense Studies."



"Dr. Todd said tests done at the Nevada State Health Laboratory 

included a "capsular staining test," which uses a special dye to 

illuminate a distinctive sugar found on the outside of anthrax, and 

the "gamma phage test," in which the sample is subjected to a virus 

that has the ability to cut up anthrax but not many other types of 

bacteria." 



"However, Dr. Chue, who served as a consultant to the U.S. government 

in the mid-1990s testing soil in Iraq for evidence of biological 

weapons, said those tests alone may not be enough. "I wouldn't be 

at all certain right now," Dr. Chue said." "Michael Osterholm, a 

bioterrorism expert at the University of Minnesota, added, "I'd 

reserve judgment before I said `yes,' " to the presence of anthrax 

in Reno."



"Adding to doubts, even the Reno sample that was viewed as an 

overall positive by state officials failed an important "fluorescent 

antibody" test, in which a protein known to bind to anthrax is 

dyed green, then applied to the sample to see if it sticks. That 

test is very hard to read, but is considered a critical part of 

identifying anthrax. Officials at Nevada's lab couldn't be reached 

for comment." 



"The CDC spokesman was unable to provide detailed information about 

its testing procedures yesterday. However, experts familiar with 

its labs say technicians there will likely perform more 

sophisticated tests, such as an Elisa test, which uses antibodies 

that bind to anthrax. The lab also will likely do a test called a 

"polymerase chain reaction," which is considered a gold standard 

for identifying anthrax; that test compares known genetic 

sequences of anthrax to DNA in the sample."



                   "Identifying Anthrax

  A battery of tests are needed to confirm the presence of anthrax. A

mystery sample is first put on a nutrient plate and given eight to 12

hours or more to grow. Then an initial set of basic tests can

determine the probability of anthrax, but some combination of further

tests is needed for confirmation.

  Basic Tests

  -- Eyeball test: Anthrax looks like a bunch of rods linked 

together like cars in a train. But other bacteria look like this too.

  -- Gram-Positive: Anthrax has a particular type of cell-wall

structure that shows up purple on a simple dye test. Again, many 

other bacteria will show up purple.

  -- Gamma Phage: A type of virus, called gamma phage, can easily cut

apart anthrax. The phage leaves many types of bacteria alone.

  -- Capsular Staining: Anthrax is surrounded by a sugar capsule 

which shows up as smooth and glassy when treated with a special dye. 

Many other bacteria look rough and jagged along the edges.

  -- Motility: Many types of bacteria tend to swim around in 

liquids, but anthrax generally stays put.

  -- Beta Hemolysis: Some bacteria cut up blood cells taken from 

sheep, but anthrax doesn't do this.

  Antibody Tests

  -- Fluorescent Antibody: The sample is flooded with an antibody,

which has been dyed fluorescent green, then washed; if it sticks, 

it's likely anthrax. But this test can sometimes be hard to read.

  -- Elisa (Enzyme-linked immunosorbent assay): Uses two separate

antibodies to test the sample. It also uses numerous "controls," in

which known anthrax and other bacteria are subjected to the test.

  Genetic Tests

  -- PCR (Polymerase chain reaction): Involves testing short 

stretches of genetic material to compare with the known genetic 

sequences in anthrax. Only certain labs can do this test, including 

the Centers for Disease Control and Prevention.  It's considered 

the "gold standard" and is rarely wrong.

  -- DNA Sequencing: This is one of the best tests, but very few 

labs can do it; the CDC and the U.S. Army lab at Fort Detrick, Md., 

can, however.



  Sources: Johns Hopkins Center for Civilian Biodefense Studies,

Southern Research Institute."



----------------

You are currently subscribed to riskanal as: maury@webtexas.com

To unsubscribe send a blank email to leave-riskanal-8628N@lyris.pnl.gov

************************************************************************

You are currently subscribed to the Radsafe mailing list. To unsubscribe,

send an e-mail to Majordomo@list.vanderbilt.edu  Put the text "unsubscribe

radsafe" (no quote marks) in the body of the e-mail, with no subject line.