Fluoroquinolone resistance in Salmonella typhi and S. paratyphi A in Bangalore, India.

Fluoroquinolone resistance in Salmonella typhi and S. paratyphi A is being increasingly reported. The minimum inhibitory concentrations (MICs) of ciprofloxacin, ofloxacin, levofloxacin and gatifloxacin against S. typhi and S. paratyphi A were compared. Fifty blood culture isolates, 25 S. typhi and 25 S. paratyphi A, were studied. The MICs were determined by the agar dilution method. Disc diffusion was done for the fluoroquinolones and other antibiotics. Nalidixic acid resistance was seen in 21/25 S. paratyphi A and 17/25 S. typhi isolates, and these had higher MICs to fluoroquinolones. Five S. typhi and six S. paratyphi A were fully resistant to ciprofloxacin (MIC >2 microg/l). No multidrug resistance was seen in S. typhi. The absence of multidrug resistance and presence of fluoroquinolone resistance warrants a review of therapy for enteric fever.