Susceptibility of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae to Roundup

Abstract

Bacteria and other microorganisms have several mechanisms to react to stress in the environment. Exposure of bacteria to antibiotics, biocides, or selective pressure may favor the emergence of antimicrobial resistance by several mechanisms as an evolution principle. Bacteria may possess cross-tolerance or cross-resistance to other environmental toxic substances present in soil, water, foods, and feeds. Glyphosate (N-phosphonomethylglycine), one of these substances used in modern agriculture might change the susceptibility of bacteria to antibiotics. The present study aimed to investigate the tolerance of extended-spectrum ß-lactamases (ESBL)-producing Enterobacteriaceae isolated from patients with nosocomial infections to glyphosate. Therefore, the minimum inhibitory concentrations of glyphosate-based herbicides (Roundup) of ESBL-positive and ESBL-negative Enterobacteriaceae were determined. Results showed that ESBL-producing Enterobacteriaceae exhibited a higher tolerance to Roundup compared with non-ESBL. To investigate the putative link between ESBL-producing Enterobacteriaceae and the resistance to glyphosate, a non-ESBL E. coil strain was used for development of glyphosate-resistant mutants using high concentrations of Roundup. Nine Roundup-resistant mutants were developed and characterized using Matrix-Assisted Laser Desorption/Ionization-Time of Flight. One Roundup-resistant mutant (Mut-A) exhibited different antibiotic susceptibility profiles compared with wild type strain. The Mut-A developed resistance to ampicillin/sulbactam, piperacillin, and streptomycin. Overall herbicides resistant Enterobacteriaceae might render resistant to β-lactam antibiotics as well. Further studies are urgently needed to investigate the mechanism of the putative link between antibiotic resistance and the herbicide-based glyphosate