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DECREASED PRODUCTION OF EXOTOXIN A DURING ENHANCED GROWTH OF Pseudomonas aeruginosa IN SERUM-SAPI MEDIUM SUPPLEMENTED WITH NOREPINEPHRINE.  T. Belay¹, H. Aviles¹, B. Pyle², G. Sonnenfeld¹. ¹Department of Microbiology, Biochemistry and Immunology, Morehouse School of Medicine Atlanta, GA; ²Department of Microbiology, University of Montana, Bozeman, MN.

   Pseudomonas aeruginosa is an opportunistic pathogen that has been shown to cause infections in immunosuppressed individuals.  Infection with P. aeruginosa has occurred in astronauts during space flight.  Catecholamines, norepinephrine (NE) in particular, enhance the growth and increases expression of virulence factors of bacteria cultured in minimal SAPI medium supplemented with 30% serum. The objective of this study was to investigate whether NE influences the production of exotoxin A (EA) by P. aeruginosa cultured in SAPI medium supplemented with 30% serum. About a 100 colonies  of P.aeruginosa  were inoculated into 10 ml of serum-supplemented SAPI medium, Tryptic  Soy broth (TSB), simpler defined medium1 (SDM1), and modified simpler defined medium 2 (MSDM2)  with or without a 100 ?l of 10^-4 M NE for 72 h. Samples were obtained at 24, 48 and 72 h for EA level determination by ELISA and for colony counts. The level of EA production was not detected in the serum-supplemented SAPI medium containing NE despite 2-3 log enhanced growth compared to growth in control cultures.  Decreased EA production was observed in TSB, SDM1 and MSDM2 cultures supplemented with serum only.  The mechanism of the effects of NE on EA production remains to be established. This work was supported by NASA through NASA Cooperative Agreement NCC 9-58 with the National Space Biomedical Research Institute.