Agroterrorism - University of Georgia College of Veterinary Medicine

mycobacteria have been aseptically isolated fromthe spleens of >70% of the striped bass, and >70%of these isolates have been type M175. It has beenproposed that M175 isolates be designated as a newspecies, Mycobacterium shottsii sp. nov. and thus wehave used this name for M175 in this proposal. Thesignificance of heavy mycobacterial infections innative striped bass from coastal waters of the easternU.S. is currently unknown.Based on sequence analyses of 16S rRNA gene andphenotypic characteristics, M. shottsii is closely relatedto M. marinum and M. ulcerans. The former isconsidered one of the primary etiologic agents of fishmycobacteriosis associated with tubercle granulomasin aquarium, cultured, and wild fish populations.M. marinum is also capable of producing diseasein humans with the primary clinical syndromesincluding skin and soft tissue infections, cervicallymphadenitis, and pulmonary disease. Disseminatedinfections due to M. marinum are often limited toimmunocompromised persons. M. ulcerans producesnecrotic skin lesions (Buruli ulcers) in humans andis considered the third most prevalent mycobacterialdisease in humans. The high prevalence of M.shottsii infections in striped bass could potentiallycause human infection in people that handle theseinfected fish. This proposed research will define thevirulence mechanisms associated with this new andemerging pathogen. In association with ongoingepidemiological studies that will define the extent ofthe spread of this agent along the eastern U.S. coast,the work described here may indicate a directiontowards appropriate treatment and preventionstrategies for afflicted fish and potentially humanpopulations.The primary mission of this laboratory is to identifyvirulence factors from pathogenic mycobacteria, andwith this information, devise methods for treatmentand disease prevention. To these ends, virulencestudies using mammalian cells and pathogenic speciesof Mycobacterium are routinely performed. Thesestudies will now be extended to include fish-derivedcell culture lines and the newly discovered pathogen,M. shottsii. We expect these studies to providenew information that will further define the pathogenesisof this emerging species and lead to bettercontrol strategies. The specific objectives, using fishmonocyte/macrophage, epithelial and fibroblastcell monolayers, will be to: 1) measure intracellularor extracellular bacterial growth, and 2) perform anecrosis/apoptosis analysis of culture filtrate from M.shottsii.At the completion of this study we will have: 1) determinedif M. shottsii is pathogenic for fish cells and ifthe organism possesses “intracellular” or “extracellular”virulence traits, and 2) determined if M. shottsiicauses cellular destruction through necrotic or apoptoticmechanisms.These findings will be made available to ecologists,fish health specialists, and human public health officialsfor further investigation of the threat to commercialfish by this putative pathogen.PI: Dr. Frederick D. Quinn (fquinn@vet.uga.edu)FishVeterinary Medical Experiment Station13