News & Politics

Hunting Down Anthrax

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Though an anxious public might wish for a simple scanner to guard
against terrorists spreading anthrax through the mail, the testing
done today on suspicious powders is still based upon some of
microbiology’s oldest techniques.

Anthrax itself was one of the first bacteria to be linked directly to a
particular illness. Robert Koch, an East Prussian doctor, was acutely
interested in anthrax in the 1870s as a cause of disease in farm animals.
With painstaking work in his home laboratory, Koch injected the blood from
diseased sheep and cattle into mice. He sampled the bacterial rods of
Bacillus anthracis from mice infected in this manner and cultured the
organism within the sterile humour of an ox eyeball. Koch subsequently
watched the organism multiply and form spores. The spores were isolated,
put on slivers of wood, injected into healthy mice, and observed to
multiply and cause the symptoms of anthrax.

This original laboratory work became known as Koch’s
postulates—subsequently adopted as one of the foundations for tying
specific microorganisms to specific diseases. Eventually, Koch won the
Nobel prize for his work on tuberculosis.

Despite the passage of more than 100 years, there still are no magical
devices available to scientists, no electronic boxes to which one can turn
and say, “Jim, my tricorder says that parcel is filled with deadly spores!”
Nor are there likely to be such things anytime soon.

Instead, infectious disease specialists are still dependent on contemporary
versions of Koch’s postulates. The anthrax bacillus must be cultured from
sick or colonized individuals. The cultures must be compared to each other
and to well-characterized strains already in the books. Samples, if and
when they arrive, recovered from areas or objects already found to be
contaminated by anthrax spores go through the same process. Even the
logistical effort is challenging.

Antibiotic sensitivity testing must be done on pure cultures. There are no
instant answers. False negatives are a constant in laboratory science, so
work must be checked and double-checked, results reconciled. A bacterial
culture dish or slant sampled from one item which yields no growth may be
mocked a few hours later by one that does. Results will arrive in a stream
of indeterminate length.

The minute focus of the news media, the constant search for an immediate
and definitive answer, will continue to collide with this process.

Approximately 20,000 people die in the United States each year due to
influenza. About 600 people developed necrotizing fasciitis (the
“flesh-eating
bacteria”) in 1999—a rare consequence of infection by Group A streptococci,
a not uncommon microorganism that causes strep throat and impetigo, both of
which affect several million each year. A mere 30 people a year succumb to
systemic Vibrio vulnificus infections, an even more rare disease.
With only a handful of confirmed cases so far, the anthrax numbers speak
loudly for the relative risks.

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