Catecholamine enhancement ofAeromonas hydrophilagrowth

Several species of bacteria have been shown to respond to the administration of norepinephrine and other catecholamines with increased growth (in culture) and virulence. In this study, we examined the effects of catecholamines on the growth of cultures ofAeromonas hydrophila, a Gram-negative bacillus found in brackish water. Bacterial cultures were maintained in tryptic soy both, then washed free of medium and transferred to a bovine serum-supplemented minimal salts medium. Treatment ofA. hydrophilacultures with 10−3to 10−5M norepinephrine resulted in dramatic increases in growth at 24 h and longer, as assessed by spot plate analysis on tryptic soy agar plates. Norepinephrine-treated cultures had 4.5 log greater bacterial numbers than control cultures. Epinephrine, dopamine and isoproterenol were shown to be similarly effective in enhancing growth ofA. hydrophila, over narrower concentration ranges. Acetylcholine supplementation of cultures did not alter the growth ofA. hydrophila.Serotonin slightly enhancedAeromonasgrowth when administered at very high concentrations (10−3M). The increased growth observed after catecholamine administration may alter the capacity to infect an animal under stressful conditions, and is another potential mechanism by which a stress response can affect susceptibility to disease.