An insight into the characterization of multidrug resistant Salmonella Minnesota isolated from poultry in Brazil.

Salmonella enterica subspecies enterica serovar Minnesota (S. Minnesota) is an emerging serovar in Brazilian poultry production. This study aimed to characterize the antimicrobial resistance profile of 20 S. Minnesota strains isolated from broiler chicken litter in Paraná, southern Brazil, between 2021 and 2023, and to confirm these findings with whole-genome sequencing. Antimicrobial susceptibility testing showed all isolates were multidrug resistant. High resistance rates were observed against ciprofloxacin (100%), ceftazidime (95%), and gentamicin (70%). Genomic analysis confirmed the resistance profiles, revealing key resistance determinants: the beta-lactamase gene blaCMY-2 was present in all isolates; parC p.T57S mutation was present in all isolates, along with plasmid-borne qnrB genes in some, correlating with ciprofloxacin resistance; and aminoglycoside resistance genes such as aac(6')-Iy, aph(3)-Ia, and aadA1 were detected. Additionally, all isolates belonged to sequence type ST548 and carried tet(A), sul2, and acrB resistance genes. A major finding was a discrepancy in in-silico serotyping. While SISTR identified all strains as S. Minnesota, SeqSero2 identified one as S. Minnesota and 19 as inconclusive, a difference that highlights the limitations of serological and in silico methods. These results emphasize the spread of MDR S. Minnesota in poultry and the necessity of genomic surveillance for accurate resistance monitoring and public health protection.