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The pet industry is expanding worldwide, particularly raw meat-based diets (RMBDs). There are concerns regarding the safety of RMBDs, especially their potential to spread clinically relevant antibiotic-resistant bacteria or zoonotic pathogens.


We aimed to investigate whether dog food, including RMBD, commercially available in Portugal can be a source of and/or other strains resistant to last-line antibiotics such as colistin.


Fifty-five samples from 25 brands (21 international ones) of various dog food types from 12 suppliers were screened by standard cultural methods between September 2019 and January 2020. Isolates were characterised by phenotypic and genotypic methods, including whole genome sequencing and comparative genomics.


Only RMBD batches were contaminated, with 10 of 14 containing polyclonal multidrug-resistant (MDR) and one MDR . One turkey-based sample contained MDR serotype 1,4,[5],12:i:- ST34/cgST142761 with similarity to human clinical isolates occurring worldwide. This exhibited typical antibiotic resistance ( +  +  + ) and metal tolerance profiles ( +  + ) associated with the European epidemic clone. Two samples (turkey/veal) carried globally dispersed MDR (ST3997-complexST10/cgST95899 and ST297/cgST138377) with colistin resistance (minimum inhibitory concentration: 4 mg/L) and gene on IncX4 plasmids, which were identical to other IncX4 circulating worldwide.


Some RMBDs from European brands available in Portugal can be a vehicle for clinically relevant MDR and pathogenic clones carrying genes encoding resistance to the last-line antibiotic colistin. Proactive actions within the One Health context, spanning regulatory, pet-food industry and consumer levels, are needed to mitigate these public health risks.


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