Hunting Down Anthrax


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.