Between June and September 2023, a total of 80 meat samples from pork and chicken meat were collected from 16 retail markets in La Plata, Argentina. Eighty-four highest priority critically important antimicrobial-resistant Escherichia coli and two Salmonella spp. were isolated. Resistance to ciprofloxacin and cefotaxime was observed in 65 and 49 E. coli isolates, respectively. Seventy-five E. coli isolates were multidrug resistant. Fourteen E. coli isolates from chicken meat showed resistance to three of the HPCIA. Resistance to third-generation cephalosporin was associated with bla_CTX-M. It is 15 times more likely to find HPCIA-resistant E. coli in chicken meat than in pork.

The occurrence of Escherichia coli resistant to high-priority critically important antimicrobials (HPCIA) in the food chain is a growing concern for food safety and public health. This study aimed to evaluate whether HPCIA-resistant E. coli isolated from pork and chicken meat at retail markets in La Plata, Buenos Aires, Argentina, exhibit source-associated genomic differentiation through whole-genome sequencing. The isolates displayed a polyclonal population structure, encompassing multiple phylogenetic groups and sequence types. Virulence gene profiles were highly diverse, with chicken-derived isolates harbouring a substantially higher number of virulence genes than pork isolates. Notably, one pork isolate carried a complete set of virulence genes characteristic of diarrheagenic E. coli. Single Nucleotide Polymorphism-based phylogenetic analysis revealed several closely related subclusters, including strains recovered from both pork and chicken meat from the same retail markets, suggesting recent clonal sharing or cross-contamination at the point of sale. These findings highlight the circulation of genetically diverse HPCIA-resistant E. coli in retail meat, underscoring the potential public health risk and the importance of monitoring resistance and virulence determinants throughout the food production chain.

The occurrence of Escherichia coli resistant to high-priority critically important antimicrobials (HPCIA) in the food chain is a growing concern for food safety and public health. This study aimed to evaluate whether HPCIA-resistant E. coli isolated from pork and chicken meat at retail markets in La Plata, Buenos Aires, Argentina, exhibit source-associated genomic differentiation through whole-genome sequencing. The isolates displayed a polyclonal population structure, encompassing multiple phylogenetic groups and sequence types. Virulence gene profiles were highly diverse, with chicken-derived isolates harbouring a substantially higher number of virulence genes than pork isolates. Notably, one pork isolate carried a complete set of virulence genes characteristic of diarrheagenic E. coli. single Nucleotide Polymorphism-based phylogenetic analysis revealed several closely related subclusters, including strains recovered from both pork and chicken meat from the same retail markets, suggesting recent clonal sharing or cross-contamination at the point of sale. These findings highlight the circulation of genetically diverse HPCIA-resistant E. coli in retail meat, underscoring the potential public health risk and the importance of monitoring resistance and virulence determinants throughout the food production chain.

Listeria monocytogenes is one of the most significant foodborne pathogens capable of causing bacteremia. In the present study, a total of 138 pork meat samples were collected from 46 randomly selected butcher shops selling raw and ready-to-eat products in La Plata, Buenos Aires, Argentina. Samples were processed according to internationally recognised standards, resulting in a positivity rate of 32.6%. This constitutes the first report of L. monocytogenes in fresh pork meat in the region and provides a strong foundation for control strategies of this microorganism in fresh pork meat retailers in Argentina.

High-risk clones represent a major concern, as they are very efficient vehicles for mobile genetic elements carrying antimicrobial resistance genes and therefore promote their spread, especially if they confer resistance to cefotaxime, ciprofloxacin, and fosfomycin, included within the highest-priority, critically important antimicrobial agents (HPCIA). Between February 2022 and April 2024, 138 pork samples were obtained from 46 butcher shops in La Plata, Buenos Aires, Argentina. A total of 102 HPCIA-resistant E. coli were isolated. Eighty-five HPCIA-resistant E. coli were selected for whole-genome sequencing. Of these, 27 belonged to 9 clones described as high risk: ST101 (n = 5), ST10 (n = 4), ST48 (n = 4), ST744 (n = 4), ST23 (n = 3), ST58 (n = 2), ST88 (n = 2), ST117 (n = 2), and ST410 (n = 1). Twelve of them were third-generation cephalosporin-resistant. Resistance was mediated by bla_CTX-M-55 (n = 7), bla_CTX-M-14 (n = 4), bla_CTX-M-8 (n = 1), and bla_CMY-2 (n = 1). This study highlights the importance of food products and the food production chain as reservoirs of high-risk clones and resistance genes of epidemiological relevance to public health.