Fluoroquinolone Resistance in Salmonella: Mechanisms, Fitness, and Virulence

Fluoroquinolones are highly effective broad-spectrum antibiotics usually used for the treatment of human and animal infections, including salmonellosis. Fluoroquinolones act against Salmonella by inhibiting their DNA replication. However, several zoonotic serotypes of Salmonella have developed resistance or are less susceptible to fluoroquinolones. Salmonella presents its resistance by substituting amino acids within the topoisomerase subunits, overexpression of multidrug efflux pumps, or decreasing the expression of outer membrane porins. The resistance level is further increased with the plasmid-mediated quinolone resistance genes which could horizontally transfer the resistance from strain to strain. The development of resistance in Salmonella shows that it is a multifactorial process and the acquisition of fluoroquinolone resistance might have significant influences on the bacterial fitness and virulence. Due to the high level resistance against fluoroquinolones that has been observed in Salmonella, care needs to be taken to avoid misuse and overuse of this important class of antibiotics to minimize the occurrence and dissemination of resistance.