Promoting effect of Fe3+ on gentamicin resistance in Escherichia coli

Abstract

Kinds of antibiotics are used to prevent and control bacteria infections, unfortunately, the overuse and misuse of antibiotic have promoted the emergence and spread of antibiotic-resistant bacteria. Therefore, understanding the mechanism of antibiotic resistance is very important. This study explores the combined effection of metal ions and antibiotic to the drug resistance of Escherichia coli. Our results found that the minimum inhibitory concentration (MIC) increased as the ammonium ferric citrate concentration increased, especially for gentamicin antibiotic. When the Fe³⁺ concentration reached 300 μM, the survival of E. coli was stably restored with the increased gentamicin concentration. Exogenous Fe³⁺ could decrease intracellular gentamicin concentration. On the other hand, Fe³⁺ treatment together with gentamicin could reduce reactive oxygen species (ROS) production, characterized by decreased levels of NADH and ATP. Furthermore, ROS-scavenging enzymes of superoxide dismutase (SOD) and catalase (CAT) were up-regulated and H₂O₂ plus gentamicin-mediated killing was restored by Fe³⁺. These results may have significant implications in understanding bacterial antibiotic-resistant mechanisms based on the external Fe³⁺ concentration.

Keywords: Antibiotic resistance; Escherichia coli; Fe(3+); Gentamicin.