Effect of interspecies signaling molecule indole and its derivatives on the virulence of acinetobacter baumannii and its persistence against fluoroquinolones

Abstract

Acinetobacter baumannii is a nosocomial pathogen associated with high fatality due to multidrug resistance. In this study, indole and its derivatives (3-indoleacetonitrile, indole-3-carbinol, indole-3-propionic acid, isatin, and 7-fluoroindole) at sub-inhibitory concentration significantly reduced surface motility, biofilm formation, antioxidant enzymes, and siderophore production in A. baumannii ATCC 17978. 3-indoleacetonitrile was most effective in reducing virulence factor production. It inhibited the quorum sensing system which regulates virulence. There was decrease in the synthesis of the quorum sensing signal 3-OH-C12-HSL due to the downregulation of abaI autoinducer synthase gene. It also reduced the minimum inhibitory concentration of imipenem, ofloxacin, ciprofloxacin, tobramycin, and levofloxacin against A. baumannii. newline