The antidepressants effect on the opportunistic microorganisms virulence

Introduction. The increasing use of antidepressants in clinical practice determines relevance of investigating their related "side" effect spectrum on opportunistic pathogens. Apart from modulating human neurotransmitter cascades, antidepressants markedly affect intestinal microbiota, however, such impact has not been fully assessed. Aim. Investigating an effect of antidepressants on virulence of opportunistic microorganisms. Materials and methods. The study examined clinical isolates of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. Bacterial biomass accumulation and polysaccharide matrix (biofilm formation) production as well as the rate of adhesion and metabolic activity upon exposure to main antidepressant groups were evaluated. The studied drugs were as follows: selective serotonin reuptake inhibitors (fluoxetine, sertaline), a serotonin and norepinephrine reuptake inhibitor (venflaxine), and a tricyclic antidepressant (amitriptyline) that inhibits monoamines neuronal reuptake. To assess formation of biomass and extracellular matrix, gentian purple and Congo red staining, respectively, were carried out. Bacterial adhesion was assessed following 30 minutes, 1h, 2h, 3h and 6 hours post-exposure. The metabolic activity was assessed by using colorimetric MTT test. Results. Antidepressants have a differentiated effect on bacterial growth and biofilm formation. In particular, fluoxetine significantly stimulated E. coli replication while reducing matrix synthesis. Venlafaxine accelerated P. aeruginosa replication and activated matrix production in S. aureus. Amitriptyline activated the growth of both P. aeruginosa and S. aureus; however, matrix production remained unchanged. Zoloft (sertalin) significantly reduced matrix production in E.coli and activated matrix synthesis in S. aureus. Fluoxetine, amitriptyline and venlafaxine had a significant effect on E.coli adhesion. Increased metabolic activity was noted for P. aeruginosa and E. coli exposed to the studied antidepressants, amitriptyline also activated K.pneumoniae. Conclusion. Thus, antidepressants can have a "side effect" on opportunistic pathogens virulence. Stimulation of replication of specific bacterial members can cause dysbiosis, and activation of adhesion, whereas biofilm formation may result in chronic course of infectious process. Altogether, the findings presented here highlight a need to further seek out for means for lowering risks associated with antidepressant intake.