Characterization of Escherichia coli isolates associated with bovine mastitis in Austria

Despite advances in dairy husbandry, mastitis-associated Escherichia (E.) coli (MAEC) remains a primary causative agent of bovine mastitis, contributing significantly to economic losses in the cattle industry. This study characterized 50 E. coli isolates from severe, moderate, mild, and subclinical mastitis by antimicrobial susceptibility testing and genotypic analysis, including PCR, DNA microarray, E. coli phylotyping and whole-genome sequencing of selected strains. Antimicrobial resistance rates were highest for ampicillin (30%), tetracycline (20%), amoxicillin-clavulanate (20%), and trimethoprim-sulfamethoxazole (14%); The majority of isolates (66%) was susceptible to antibiotics. One isolate displayed an ESBL phenotype, carrying blaCTX-M-3 and blaTEM-1 genes. Phylogenetic analysis indicated that members of phylogroups B1 (50%) and A (16%) are predominant among the isolates, followed by group C (12%), with the remaining isolates belonging to groups D, E, and F, and two unassigned. The most prevalent virulence-associated genes detected were fimH (100%), and genes of the ferric dicitrate uptake locus (fecIRABCDE). Overall, MAEC isolates exhibited diverse and heterogeneous genetic profiles. The proliferation of ESBL-producing E. coli poses a threat within a One Health framework, given the risk of multidrug-resistant strains at the human-animal-environment interface, compromising critical antimicrobials in both veterinary and human medicine.

University of Donja Gorica
Leibniz-Institut für Photonische Technologien
InfectoGnostics Research Campus Jena
Medizinische Universität Innsbruck
Justus-Liebig-Universität Giessen
Österreichische Agentur für Gesundheit und Ernährungssicherheit GmbH
Friedrich-Schiller-Universität Jena