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A new research study developed by researchers from the BacT_Drugs Lab at UCIBIO - FFUP - University of Porto, brings good news for poultry production and food safety related to bacterial resistance to colistin, a last-resort antibiotic reserved to severe/hard-to-treat human infections. Three to eight months after adoption of colistin ban on Portuguese farms, the authors screened marketed chicken meat for colistin resistant bacteria. The study was published as a Special Issue Article in the Journal of Environmental Microbiology (doi:10.1111/1462-2920.15689).


"Colistin has been commonly used in food-animal production and is recognized as a contributor for the spread of colistin resistance and colistin resistance gene “mcr” across food chain with impact on human health. EU actions involve colistin restrictions in food-animal production chain, but the impact of these measures on poultry-derived products was underestimated, justifying farm-to-fork studies", explains Patrícia Antunes, researcher at the BacT_Drugs Lab and Professor of Food Microbiology at Porto University-FCNAUP. Patrícia Antunes is the leader of the research work under IJUP-Empresas Project.


The authors detected a reduction in colistin-resistant bacteria with “mcr” genes in poultry meat samples, from 80-100% to 12% after 8 months of colistin ban on poultry farms. To find out if the bacteria detected, Escherichia coli and Klebsiella pneumoniae (both with potential to cause infections), persisted over time, the authors used a rapid methodology (Fourier transform infrared “FTIR” spectroscopy) developed by the group (doi:10.1128/mSystems.00386-19) that proved to be useful for discriminating bacteria in the food/animal context. Using this method, the authors identified, with high precision and at low cost, K. pneumoniae and E. coli strains persisting through the food chain during months.


Whole genome sequencing revealed that most of the bacteria studied carried genes encoding resistance to other antibiotics and metals, also widely used in food-producing animals to control diseases or as growth-promoters, possibly compromising the success of colistin restriction measures at long-term which needs close monitoring.

The researchers conclude that colistin ban at farm level resulted in a positive outcome for reducing colistin-resistance towards healthier and sustainable food systems in EU, but authorities must be alert to other factors to guide concerted, effective and durable actions under a “One Health” perspective.


Original article:

From farm to fork: Colistin voluntary withdrawal in Portuguese farms reflected in decreasing occurrence of mcr-1-carrying Enterobacteriaceae from chicken meat. Sofia Ribeiro, Joana Mourão, Ângela Novais, Joana Campos, Luísa Peixe and Patrícia Antunes. Environmental Microbiology (2021). doi:10.1111/1462-2920.15689