Diverse and Flexible Transmission of fosA3 Associated with Heterogeneous Multidrug Resistance Regions in Salmonella enterica Serovar Typhimurium and Indiana Isolates

We identified fosA3 at a rate of 2.6% in 310 Salmonella isolates from food animals in Guangdong province, China. The fosA3 gene was genetically linked to diverse antibiotic resistance genes (ARGs), including mcr-1 , bla _{CTX-M-14/55}, oqxAB , and rmtB These gene combinations were embedded in heterogeneous fosA3 -containing multidrug resistance regions on the transferable ST3-IncHI2 and F33:A-:B- plasmids and the chromosome. This indicated a great flexibility of fosA3 cotransmission with multiple important ARGs among Salmonella species.