Salmonella enterica Serotype Typhi with Nonclassical Quinolone Resistance Phenotype

Abstract

We report Salmonella enterica serotype Typhi strains with a nonclassical quinolone resistance phenotype (i.e., decreased susceptibility to ciprofloxacin but with susceptibility to nalidixic acid) associated with a nonsynonymous mutation at codon 464 of the gyrB gene. These strains, not detected by the nalidixic acid disk screening test, can result in fluoroquinolone treatment failure.

Keywords

• Salmonella
• typhoid fever
• ciprofloxacin
• treatment failure
• gyrB
• bacteria