Using extracts from a common Chesapeake Bay sponge, Professor Leleng To of Goucher College and Dr. Salman Siddiqi of Becton Dickinson successfully stopped or slowed the growth of a strain of the tuberculosis-causing bacteria--suggesting possibilities for creating novel drugs to treat the deadly disease.
Funded by Goucher College, the National Institutes of Health, and Becton Dickinson, Isaacs prepared the extracts at Goucher College and tested them on the H37RV strain of Mycobacteria tuberculosis with Siddiqi in a Biosafety Level Three laboratory at Becton Dickinson. Matthew Warns, Rose Wolford, and Sheryl Douglas, who work in the tuberculosis R & D lab at Becton Dickinson, assisted in the collection of data. Isaacs and Siddiqi will present their results at the 105th General Meeting of the American Society for Microbiology in Atlanta, GA, on June 8, 2005.
Isaacs obtained more than 150 bacterial isolates from winter samples of Microciona prolifera, a sponge found widely in the Chesapeake Bay. Isaacs and Siddiqi tested 30 on the tuberculosis-causing bacterium by preparing ground extracts in hexane, butanol, and a water-based buffer and adding them to media containing fresh cultures of the H37RV bacterial strain. Measuring growth by monitoring carbon dioxide levels, Isaacs and Siddiqi found that all of the extracts inhibited the growth of H37RV. To determine whether the bacterium had been killed, they placed the cultures used in the experiments in fresh media without sponge extracts--and concluded that some of the extracts had killed the tuberculosis bacilli entirely.
Isaacs and Siddiqi also tested another species of mycobacteria, M. avium, for acid-fastness in the presence of sponge extracts. Acid-fastness is an indication of the presence of mycolic acid in the cell wall of bacteria; the anti-tubercular drug isoniazid causes a loss of it. They found that M. avium lost its acid-fastness in the presence of sponge extracts--an important observation because any substance that causes such a loss is a potential candidate for treating tuberculosis.
Isaacs and Siddiqi focused their next studies on finding microbial isolates that might be responsible for inhibiting growth in the H37RV strain of Mycobacterium tuberculosis. Through a rapid stamp plate assay, they found five such isolates. The tuberculosis bacterium could not grow next to three of the isolates and showed almost no growth next to the other two.
Next to HIV and AIDS, tuberculosis is the leading cause of death in the world. About one-third of the world population is thought to be infected with Mycobacterium tuberculosis, and the disease is responsible for as many as two million deaths each year worldwide. The emergence of multiple drug-resistant strains makes the discovery of new drugs imperative.
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