Tropical Plants: Potential Source for Antimicrobial Agents Saleh Naser Molecular Biology and Microbiology University of Central Florida Orlando, Fl 32816 407/823-2382 Paper U-6, Session 42-U Tuberculosis is a highly contagious airborn disease. WHO estimated that over 8 million new cases and 3 million fatalities occur annually. In immunocompromised patients, there has been a marked resurgence of human tuberculosis related to the AIDS epidemic, some of which are multiple drug resistant strains. In addition, a numbe of opportunistic pathogens from the genus Mycobacterium have emerged, most notable the Mycobacterium avium complex infections in AIDS patients. A recent report indicated that 50-70% of individuals with AIDS develop M. avium complex disease symptoms and/or tuberculosis. Current therapy against mycobacterial infections includes the use of Isoniazide (INH), Refabutin, Clarithromycin or combinations of others. Several secondary drugs have also been recommended. However, due to the marked resurgence in multiple drug resistant strains of Mycobacteria, these prescribed antimycobacterial drugs are ineffective for controlling these diseases. Therefore, the need fo! r an alternative drug is urgent. The objective of our investigation is to screen and identify new drug(s) from extracts of tropical plants active against multiple drug resistant pathogens such as tuberculosis and vancomycin-methicillin resistant strains of Staphylococcus aureus. Extracts from over 200 tropical plants were screened for antimicrobial activity against M. tuberculosis strain H37RV. Thirty-five of these plants had a minimum of 80% inhibition using concentraions of 500 micrograms/mL. Additionally, ten of these extracts produced similar activity using a concentration of 100 micrograms/mL. The ten extracts are undergoing further purification and testing. To date, five of the extracts have been further purified with antimicrobial activity similar to those mentioned above using the lower concentration. The pure active compound(s) will be analyzed for cell toxicity, the mechanism of action and for the chemical composition before possible clinical trials. Our preliminary data indicate that the ten plants have great potential for the development of antimicrobial agents. This ongoing study is being carried out in the research laboratory of Dr. Saleh Naser in the Department of Molecular Biology and Microbiology in collaboration with Dr. Howard Miles of the Chemistry Department and the Center for Diagnostics and Drug Development (CD3) at the University of Central Florida. The study is currently funded by the College of Health and Public Affairs and the CD3 of the University of Central Florida. The data will be presented at the 98th General Meeting of the American Society for Microbiology held May 17-21, 1998 in Atlanta, Georgia.