The influence of reduced susceptibility to fluoroquinolones in salmonella enterica serovar typhi on the clinical response to of loxacin therapy

Background: Infection with Salmonella enterica serovar Typhi (S. Typhi) with reduced susceptibility to fluoroquinolones has been associated with fluoroquinolone treatment failure. We studied the relationship between ofloxacin treatment response and the ofloxacin minimum inhibitory concentration (MIC) of the infecting isolate. Individual patient data from seven randomised controlled trials of antimicrobial treatment in enteric fever conducted in Vietnam in which ofloxacin was used in at least one of the treatment arms was studied. Data from 540 patients randomised to ofloxacin treatment was analysed to identify an MIC of the infecting organism associated with treatment failure. Principal Findings: The proportion of patients failing ofloxacin treatment was significantly higher in patients infected with S. Typhi isolates with an MIC ≥ 0.25 µg/mL compared with those infections with an MIC of ≤ 0.125 µg/mL (p