Participation of S. Typhimurium _cysJIH operon in the H₂S-mediated ciprofloxacin resistance in presence of sulfate as sulfur source

H₂S production has been proposed as a mechanism to explain bacterial resistance to antibiotics. In this work, we present evidence for the role of the cysJIH operon in resistance to ciprofloxacin mediated by H₂S production with different sulfate as the only sulfur source. We found that the products of the cysJIH operon are involved in ciprofloxacin resistance by increasing both, the levels of H₂S and reduced thiols apparently counteracting antimicrobial-induced reactive oxygen species (ROS). This protective effect was observed only when bacteria were cultured in the presence of sulfate, but not with cysteine, as the sole sulfur source.