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Brown rats () are an important wildlife species in cities, where they live in close proximity to humans. However, few studies have investigated their role as reservoir of antimicrobial-resistant bacteria.


We intended to determine whether urban rats at two highly frequented sites in Vienna, Austria, carry extended-spectrum β-lactamase-producing Enterobacteriaceae fluoroquinolone-resistant Enterobacteriaceae and meticillin-resistant (MR) spp. (MRS).


We surveyed the presence of antimicrobial resistance in 62 urban brown rats captured in 2016 and 2017 in Vienna, Austria. Intestinal and nasopharyngeal samples were cultured on selective media. We characterised the isolates and their antimicrobial properties using microbiological and genetic methods including disk diffusion, microarray analysis, sequencing, and detection and characterisation of plasmids.


Eight multidrug-resistant and two extensively drug-resistant New Delhi metallo-β-lactamases-1 (NDM-1)-producing ST114 ( complex) were isolated from nine of 62 rats. Nine Enterobacteriaceae isolates harboured the gene and one carried a plasmid-encoded gene (). Forty-four MRS were isolated from 37 rats; they belonged to seven different staphylococcal species: , , , , , (all -positive) and -positive .


Our findings suggest that brown rats in cities are a potential source of multidrug-resistant bacteria, including carbapenem-resistant . ST114. Considering the increasing worldwide urbanisation, rodent control remains an important priority for health in modern cities.


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