Colistin resistance in pigs – assessing the effectiveness of mitigation measures ; Résistance à la colistine chez le porc - des mesures de maîtrise efficaces

National audience ; The discovery of the plasmid gene for resistance to colistin mcr-1 in 2015 profoundly changed how this widely used molecule in veterinary medicine in France was considered. Subsequently, national management measures were set up to reduce its use in animals, in line with European Union recommendations aiming at preserving usefulness of colistin for human multiresistant infections treatment. To assess the effectiveness of these measures, French sales, usage and resistance surveillance data from the pig production sector were analysed. Based on national antibiotic sales data and INAPORC Panel results, the use of colistin in pig production in France strongly decreased from 2010 to 2019. Resistance to colistin was rare or absent in commensal bacteria isolated from slaughterhouse surveillance. In contrast, analysis of susceptibility tests collected by Resapath and carried out on clinical isolates in the context of digestive disorders in pigs showed an initial increase in resistance from 2006 to 2011 and a steady decrease thereafter. The correlation between sales and clinical isolate resistance over this period was strong and significant. Thus, applications measures to decrease colistin use were effective in France, leading to a strong decrease in consumption and a simultaneous decrease in colistin-resistance of clinical E. coli isolates.