Participation of S. Typhimurium cysJIH Operon in the H2S-mediated Ciprofloxacin Resistance in Presence of Sulfate as Sulfur Source

Ricardo Álvarez,Iván Calderón,Fernando Gil,Daniel Paredes-Sabja,Jorge Frávega,Paula Rodas,Juan Fuentes

doi:10.3390/antibiotics4030321

Abstract

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.

Highlights

In prokaryotes, sulfur can be assimilated into sulfur-containing amino acids through enzymatic fixation from inorganic sources such as sulfate [1], or from organic sources such as cysteine [2,3,4]
We reported that cysJIH contributes to diminish reactive oxygen species (ROS) levels induced by the exposure to antimicrobial agents such as menadione and ceftriaxone by increasing the Superoxide Dismutase (SOD) activity, the levels of reduced thiols, and H2S
This effect was only observed when bacteria were cultured with sulfate as the sole source of sulfur [12], strongly suggesting that cysJIH contribute to CIP resistance by diminishing ROS

Summary

Introduction

Sulfur can be assimilated into sulfur-containing amino acids through enzymatic fixation from inorganic sources such as sulfate [1], or from organic sources such as cysteine [2,3,4]. Since H2S is considered a gasotransmitter that protects neurons and cardiac muscle from oxidative stress [5,6,7], it has been hypothesized that bacterial H2S likewise acts as a cellular protector In this sense, bacteria with mutations that suppress H2S production are sensitive to several antimicrobial compounds that exert their bactericidal activity via oxidative stress, like β-lactam antibiotics [8,9,10]. We found that the products of the cysJIH operon are involved in CIP-resistance by increasing both the levels of H2S and reduced thiols, apparently counteracting the ROS induced by this kind of antimicrobial agents. This protective effect was observed only when bacteria were cultured in sulfate, but not with cysteine, as the sole sulfur source

Bacterial Strains and Growth Conditions

Determination of Intracellular ROS Levels

Determination of Reduced Thiols

H2S Production

Results and Discussion