Pitfalls of interpreting ciprofloxacin minimum inhibitory concentrations in Salmonella enterica serovar Typhi

摘要

We read with interest the article on emergence of fluoroqumolone resistance in Salmonella enterica serovar Typhi in Andaman and Nicobar Islands. As fluoroquinolones are widely used in the empirical therapy of enteric fever, it is important to determine the minimum inhibitory concentrations (MIC) of this group of antimicrobials in an endemic area. However, there were certain points in the article that needed clarification, which we would like to highlight: (i) CLSI 2007 guidelines have been used though the study was conducted in 2009-2010. (ii) The Table showed that five out of six isolates had an MIC of 0.25 mug/ml. Based on CLSI guidelines till 2011, MICs of <1 mug/ml have indicated that the organism is susceptible to ciprofloxacin. The 2012 CLSI guidelines have reduced the MIC indicating ciprofloxacin susceptibility to <0.06 ng/ml, probably making most of our strains resistant to ciprofloxacin.