Risk analysis of the transmission of antimicrobial resistant Escherichia coli in pork food chain: a “farm-to-fork” perspective

Abstract

Antimicrobial resistance (AMR) is a public health risk that needs to be faced in a One Health perspective, including humans, animals, and environmental health. Food production chain has been identified as a possible route of transmission of AMR bacteria to humans. The most critical phenomenon is related to Critically Important Antimicrobial’s (CIA) resistance such as β-lactams antibiotics (cephalosporin of 3rd, 4th generation, carbapenem, monobactams and penicillins), quinolones, aminoglycosides, polymyxin and glycylcyclines. The same pigs were analysed along the entire food producing chain steps sampling pigs’ feces, then carcasses and finally pork food products (fresh meat, fermented and seasoned product). Escherichia coli (E. coli) were isolated from samples collected, and AMR and MDR profiles were evaluated: 1. The ability of E. coli to produce ESBL and AmpC β-lactamases was evaluated both phenotypically by disk diffusion method and genotypically by the research of the most common ESBL and AmpC plasmidic related genes; 2. MDR to 17 antimicrobial molecules were evaluated on the same isolates using Minimal Inhibitory Concentration; 3. All the strains that showed the same AMR in different stages of the food producton chain of the same pig or of pigs originating from the same farm were considered; 4. Phylogenetic analysis were performed through Enterobacterial Repetitive Intragenic Consensus (ERIC-PCR). Phylogenetic similarities between the strains identified were considered in order to evaluate the possible “farm-to-fork” transmission of AMR bacteria; 5. Average Nucleotide Identity (ANI) was used to genomically identify the strains considered and confirm the phylogenetically relation found by ERIC-PCR. Results showed that on 243 pork food chain fully or partially analysed the E. coli AMR profiles from feces, through carcasses, fresh meat to fermented and seasoned meat product, only in one case showed that resistant bacteria were phylogenetically similar from farm-to-fork (isolates in feces, carcasses and fresh meat have more than 95% of genomic similarities). Frequent similarities were shown in resistant E. coli isolates from carcasses and fresh meat or fermented product and in one case, bacteria isolated from fresh meat and fermented product were genomically similar. In conclusion, results showed that the transmission directly from farm-to-fork is possible but not frequent. However, the food producing environment and cross contamination can play an important role in the dissemination of AMR in fact antimicrobial resistant bacteria were easily found in the different stages of the food chain. New drugs are needed, and metal-based compounds represent a valid scaffold to explore new antibiotic classes. In this study we choose to investigate gallium(III) complexes for their potential antimicrobial activity against different strains of Klebsiella pneumoniae, E. coli and Pseudomonas aeruginosa which have developed different type of resistance mechanism including the production of β-lactamases (NDM-1, ESBL or AmpC). The compounds were active against resistant Gram-negative strain with minimal inhibitory concentration in the μM range, while no cytotoxicity was detected in eukaryotic cells. Further studies are needed to improve risk communication to consumers and access to clear and reliable information and health concerns on pork food labels.