Identification of the molecular mechanisms of heavy metals driven antimicrobial resistance in Acinetobacter Baumannii Isolates originating from conflict areas

Abstract

Background: Wars have been a great burden on humanity for a long period of time. The high medical costs of wars particularly those incurred in treating patients with multi-drug resistant infections is probably one of its most adverse effects. Acinetobacter baumannii is one of those superbugs which has gained much notoriety during times of wars for causing multi-drug resistant infections among injured military and civilian personnel. The rapidly evolving resistance of this bacterium particularly during this incidence hints out the role of bacterial milieu in promoting the emergence of this highly resistant pathogen. Since military regions are considered hot spots for heavy metals contamination, we hypothesize that exposure of A. baumannii to heavy metals coming from shelling and use of ammunitions in war regions might be correlated with its increased levels of antimicrobial resistance (AMR). Therefore, herein we aim to investigate the effects of heavy metals on AMR of A. baumannii clinical isolates particularly those originating from war patients and determine the mechanisms implicated at the molecular level. Methods: A total of 11 clinical isolates of A .baumannii, 7 obtained from non-war wounded patients living in conflict areas and 4 recovered from war injuries specifically from Iraqi patients, were screened for their susceptibility against a panel of 8 heavy metals (Zn2+, Cu2+, Cr6+, Pb2+, Ba2+, Cd2+, Hg2+, and As5+) commonly used in weapons, 5 antimicrobial agents (Meropenem, Colistin, Gentamicin, Ciprofloxacin, and Cefepime), and 40 different combinations of antimicrobial agents and heavy metals using the Broth Micro-Dilution (BMD) assay. Induction of resistance in vitro in the fully susceptible reference strain A. baumannii DSM 30008 to selected heavy metals (Copper, Lead, Cadmium, and Arsenate) and-or antimicrobial agents (Gentamicin, Cefepime, and Meropenem) followed by phenotypic resistance testing and Whole Genome Sequencing (WGS) of raised resistant mutants were performed to investigate the molecular