Bioconversion of Tyrosine- and Tryptophan-Derived Biogenic Amines by Neuropathogenic Bacteria

The biochemical potential of pathogenic bacteria may cause alteration in the neurophysiological environment; consequently, neuroendocrine and immune responses of the host are modulated by endogenously produced metabolic products of neuropathogenic bacteria. The present study was designed to detect the derived biogenic amines in spent culture media of Bacillus cereus (Bc), Clostridium tetani (Ct), Listeria monocytogenes (Lm), and Neisseria meningitidis (Nm). Overnight grown culture in different culture media i.e., Nutrient broth (NB), Luria basal broth (LB), Brain Heart Infusion broth (BHI), and human serum supplemented RPMI 1640 medium (RPMI) were used to prepare filter-sterilized, cell-free cultural broths (SCFBs) and subjected to high performance liquid chromatography with electrochemical detection (HPLC-EC) along with the control SCFBs. Comparative analysis of biogenic amines in neuropathogenic bacterial SCFBs with their respective control (SCFB) revealed the complete degradation of dopamine (DA) into its metabolic products by Bc, Ct, and Nm, whereas Lm showed negligible degradation of DA. A relatively high concentration of 5-hydroxyindol acetic acid (5HIAA) by Bc in NB and LB indicated the tryptophan metabolism by the serotonin (5HT) pathway. Our study suggests that microbial endocrinology could help unravel new perspectives to the progression of infectious diseases.