Finding Mobile Genetic Components in Salmonella, and Salmonella Typhimurium Serovars that Give Resistance to Heavy Metals and Linking them to Antibiotic Resistance

Abstract

S. 4,[5],12:i:-, also known as Salmonella enterica subsp. enterica serovar Typhimurium variation
4,[5],12:i:-, has quickly become the most common Salmonella serovar in pigs and is frequently linked to
the development of heavy metal resistance (HMR) and antibiotic resistance (ABR) genes. Our work
examined the evolution of mobile genetic elements (MGEs) comprising HMR and ABR genes in 78
strains of S. 4,[5],12:i:- (n = 57), and S. Typhimurium (n = 21), which were gathered between 1999 and
2021. The following five MGEs were found to harbor HMR genes: pUO-STVR2, pSTM45, pUO-STmRV1,
SGI-4, and MREL. 91.23 percent (52/57) of the strains of S. 4,[5],12:i:- carried at least one of these
components, while only 14.29 percent (3/21) of the strains of S. Typhimurium did the same. Due to the
European Union's ban on the use of antibiotics as feed additives, S. 4,[5],12: i:- have changed from
mostly carrying pUO-STmRV1 to the emergence of SGI-4 and MREL, lowering ABR genes. SGI-4 and
MREL imparted increased resistance to copper and silver in S. 4,[5],12:i:-, indicating that their
acquisition was associated with the continued use of heavy metals in food-animal production. The
necessity for focused interventions to reduce the spread of multidrug-resistant Salmonella in veterinary
and public health settings is highlighted by the fact that strains bearing SGI-4 and MREL still show
multidrug resistance.