Molecular and Phenotypic Characterization of a Multidrug-Resistant Escherichia coli Coproducing OXA-232 and MCR-1.1...

Area of Science:

• Microbiology
• Molecular Biology
• Clinical Infectious Diseases

Background:

• Carbapenem-resistant Enterobacterales (CRE) pose a global health threat due to limited treatment options.
• OXA-48-like carbapenemase-producing Enterobacterales are emerging in South America.
• Multidrug-resistant (MDR) bacterial infections require continuous surveillance and characterization.

Purpose of the Study:

• To characterize a multidrug-resistant Escherichia coli isolate from a hospitalized patient in Buenos Aires.
• To identify the antimicrobial resistance genes and their genetic context within the isolate.
• To report the first co-occurrence of OXA-232 and mcr-1.1 in South American E. coli.

Main Methods:

• Phenotypic characterization: antimicrobial susceptibility testing, synergistic and colorimetric assays.
• Molecular characterization: Polymerase Chain Reaction (PCR), whole genome sequencing (WGS), and plasmid analysis.
• Isolate identification: Sequence Type (ST744), phylogroup (A), and serotype (O162/O89:H9).

Main Results:

• The E. coli isolate remained susceptible to several key antibiotics including meropenem and tigecycline.
• Identified resistance genes: blaOXA-232 (on a non-conjugative ColKp3 plasmid), blaCTX-M-14, mcr-1.1, and fosL1 (on two conjugative plasmids).
• This represents the first report of OXA-232 and mcr-1.1 co-production in a South American E. coli clinical isolate, particularly in a patient without prior colistin treatment.

Conclusions:

• The characterized E. coli isolate demonstrates a complex MDR profile with significant public health implications.
• The presence of mobile colistin resistance (mcr-1.1) and carbapenemase (OXA-232) genes highlights the need for enhanced surveillance in South America.
• Understanding the genetic mechanisms of resistance is crucial for developing effective treatment and control strategies against CRE.