Phenotypic and molecular characterization of multidrug-resistant Escherichia coli strains carrying resistance genes isolated from various clinical cases in Iraq

Document Type : Research Paper

Authors

1 Department of Medical Biotechnology, College of Biotechnology, Al-Qasim Green University, Babylon 51013, Iraq.

2 Department of Medical Laboratory Techniques, Institute of Medical Technology- Al Mansour, Middle Technical University (MTU), Baghdad, Iraq.

3 Department of Medical Biotechnology, College of Biotechnology, Al-Qasim Green University, Babylon 51013, Iraq

Abstract

Objective
Multidrug-Resistant (MDR) E. coli are among the most important causes of urosepsis. and they also pose a significant economic burden on hospitals worldwide. To further exacerbate the issue, MDR has spread rapidly through E. coli populations, making infections more troublesome and costlier to treat, requiring a new therapeutic approach. This investigation aimed to detect the phenotypic and molecular characteristics of MDR in E. coli strains recovered from Iraqi patients with urinary tract infections (UTIs) and wounds.
Materials and methods
Thirty clinical samples were collected from midstream urine (MSU) and wound discharge. The clinical E. coli was identified phenotypically based on shape, size, texture, and color of bacteria on medium and confirmed using the VITEC 2 compact system, with 10 confirmed as MDR strains showing 100% resistance to CIP and CAZ. The minimum inhibitory concentration (MIC) testing was done using the checkerboard microdilution method. Fractional Inhibitory Concentration (FIC) indices were investigated. Gene expression study was preformed via RT-qPCR for emrD and marA genes. Statistical analysis was achieved using SPSS 27 and GraphPad Prism 10.
Results
The CIP-CAZ combination decreases the MIC level from 200 µg/mL and 260 µg/mL (separately) to 50 µg/mL (combined), with a ΣFIC index of 0.4495, representing highly synergism. Combinations (CIP, CAZ) with bacteriocins and leucine promote greater antibacterial activity, mainly at 50-60 µg/mL, with significant reductions in growth rate (P < 0.01). Gene expression revealed noticeable downregulation of emrD and marA in all combination therapies. For emrD gene, the expression decreased from 1.06±0.36 (control) to 0.05±0.05 (CIP/leucine), while for marA gene reduced from 1.17±0.47 to 0.03±0.02 (CAZ/bacteriocin), with all comparisons showing P-values < 0.01.
Conclusions
The outcomes support the use of antibiotic-adjuvant combinations as a promising strategy to prevent MDR E. coli infections. The result aligns with global studies on antimicrobial synergy and announces novel gene targets for resistance variation.

Keywords

Agricultural Biotechnology Journal
Volume 18, Issue 2
February 2026
Pages 415-434

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