Published Date: 2008-09-24 16:00:32
Subject: PRO/AH> Anthrax, human, 2001 - USA (11): review
Archive Number: 20080924.3019
ANTHRAX, HUMAN, 2001 - USA (11): REVIEW
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Thu 18 Sep 2008
Source: Analytical Chemistry [summarized, edited]
Tracing killer spores: the science behind the anthrax investigation
[This is a referenced review of the microbial forensics involved in
the FBI investigation. It is fully referenced and clarifies many of
the confusions engendered in past weeks. If you have been following
the news and scientific journal reports it will not contain much that
it is new but it is straightforward. - Mod.MHJ]
The FBI conclusions about the anthrax letter spores attributed
primarily or solely to scientific analyses:
1. They were produced in recent times (ca. 1999-2001).
2. They were grown in 2 different batches.
3. No substances were added to the spores postproduction to make them
4. Silicon and oxygen were present on the inside (coat) of the
spores, not the outside (exosporium).
5. They contained mostly the wild-type _Bacillus anthracis_ 'Ames'
but had significant numbers of phenotypic variants or substrains.
6. The unique phenotypic variants could be detected by a combination
of assays for 4 different insertion/deletion polymorphisms.
7. Out of the 1070 samples collected in the repository of Ames
samples, 8 contained all 4 of the polymorphisms; none contained 3 out
of 4 mutations, and a few contained 1 or 2 of the mutations.
[There are points where one might disagree with the authors. For
example an FBI laboratory individual is quoted as saying: "It was
noteworthy that the anthrax powders that were in the letters had
discernible numbers of phenotypic variants, and this was unusual for
anthrax, and, in particular, unusual for Ames." In my SPL (Special
Pathogens Laboratory) we saw this frequently and especially in
relation to isolates from food-borne anthrax outbreaks which are, in
retrospect, commonly made up of multiple strains. It is a reliable
epidemiologic marker for such events.
The paper does not clarify how silicon got to be in the spore coat in
the high levels found though the FBI claims it is a "natural
occurrence" but one which could not be replicated. While there were
defined genetic variants in the RMR-1029 stock there is no
information on their frequency in that singular flask. This is of
relevance when claims are made as to their presence or absence in
subcultures. The nature of the _Bacillus subtilis_ found in the 1st
batch of letters is not defined. Knowing this in relation to other
_B. subtilis_ cultures in circulation would add or subtract from
claims as to the location of the culturing of the letter batches. And
on a personal note I do wonder why if the simple spore-washed letter
batches were so very dispersible, why have we been researching spore
additives for the past 70 years? [Obviously the additives make it
more efficient and reliable, but one may still ponder the question.]
This may be relevant to the expectations of the perpetrator and
constraints on how the letters were loaded.
Mueller, head of the FBI, has proposed that an NAS (National Academy
of Sciences) committee of experts should examine the FBI scientific
evidence. What the latter will include and not is still unclear. - Mod.MHJ]
Dr. Med. Vet. Pia Zimmermann
Bavarian Food and Health Safety Authority