Supplementary data – Antimicrobial resistance of Escherichia coli in Hungarian wild rats – Szmolka, 2026

This study presents a comprehensive analysis of antimicrobial resistance in E. coli from brown rats (Rattus norvegicus), focusing on the occurrence and genetic basis of resistance and characterizing an ESBL-producing E. coli strain with a fully resolved CTX-M-1 plasmid. 25.6% of 90 brown rats carried AMR E. coli strains, with 8.9% displaying multidrug resistance. The predominant resistance pattern was combined resistance to ampicillin (17.8%) and tetracycline (12%), with plasmid-associated resistance genes blaTEM−1 and tet(A)/tet(B).

The study identified the first ESBL-producing E. coli strain (88/Ec2) in an urban rat in Hungary, harboring the gene blaCTX−M−1 on an approximately 92 kb IncI1 plasmid pCTX-M-1_88/Ec2. Comparative plasmid analysis showed 98% structural similarity to CTX-M-1 plasmids from human-derived pathogens. Strain 88/Ec2 was serotyped as O168:H38 and assigned to a novel sequence type, ST17982.