Monitoring of Antimicrobial Resistance of Serotypes Isolated from Humans in Northwest Italy, 2012-2021.

is among the most common causes of foodborne outbreaks in humans in Europe. The global emergence of resistance to antimicrobials calls for close monitoring of the spread and prevalence of resistant strains. In this study, we investigated the occurrence of antimicrobial resistance of serotypes isolated from humans between 2012 and 2021 in Piedmont, northwest Italy. A total of 4814 strains (168 serotypes) were tested against six classes of antimicrobials. Many strains (83.3%) showed resistance to at least one antibiotic: tetracycline (85.1%), ampicillin (79.2%), quinolones (47.4%), and gentamicin (28.4%). Between the first (2012-2016) and the second study period (2017-2021), a decrease in antimicrobial resistance was noted for tetracycline (from 92.4% to 75.3%), ampicillin (from 85.3% to 71.3%), quinolones (from 49.4% to 44.6%), and cefotaxime (from 34.8% to 4.0%). Many multidrug resistant strains (43.6%) belonged to ser. Typhimurium, ser. Infantis, and ser. Typhimurium 1,4,[5],12:i:-. Overall, multidrug resistance decreased from 60.7% to 26.4%, indicating a reduction in the antimicrobial resistance of strains in Piedmont and in Europe and demonstrating the effectiveness of the measures that were put in place to reduce antimicrobial resistance.