Salmonella spp. are important foodborne pathogens, and multidrug-resistant (MDR) Salmonella strains have become a serious threat to clinical therapy. MDR S .

Colistin is a last-resort antibiotic for severe infections caused by multidrug-resistant (MDR) Gram-negative pathogens. Colistin resistance genes mcr , particularly mcr-1 , have been found in Enterobacteriaceae around the world, mainly in Escherichia coli and Salmonella . Salmonella enterica is a major foodborne pathogen, with MDR Salmonella being considered a “Serious Threat Level pathogen” by the Centers for Disease Control and Prevention.

Tigecycline has been regarded as one of the last-resort antibiotics available for the treatment of infections caused by carbapenem-resistant Enterobacterales . The plasmid-mediated resistance-nodulation-division–type efflux pump gene cluster tmexCD - toprJ is a newly identified tigecycline resistance determinant.

Oxazolidinone are effective antimicrobial agents for the treatment of infections caused by multidrug-resistant Gram-positive bacteria, including vancomycin-resistant enterococci. The emergence and global spread of transferable oxazolidinone resistance genes such as optrA is worrisome. Enterococcus spp. can become causes of hospital-associated infections and are also widely distributed in the gastrointestinal tracts of animals and the natural environment.