Revised Ciprofloxacin Breakpoints
for Salmonella: Is it Time to Write
an Obituary?
2467-2469
Correspondence
Dr. V. Anil Kumar,
Amrita Institute of Medical Sciences, Ponekkara, Kochi, Kerala-682041, India.
Office:+91484 2801234 (Extn: 8015), Fax: +91484 2802020,
Mobile: +919037401413
E-mail: vanilkumar@aims.amrita.edu
Objectives: To determine the minimum inhibitory concentration of ciprofloxacin among 50 blood stream isolates of Salmonella enterica.
Material and Methods: A total of 50 consecutive isolates of Salmonella enterica were tested for susceptibility to antimicrobials using the Kirby Bauer disk diffusion method. Minimum inhibitory concentrations were determined using Hi-Comb strips. All results were interpreted according to the CLSI guidelines.
Results: Of the 50 isolates 70%were Salmonella Typhi, 4% Salmonella paratyphi A, 2% Salmonella paratyphi B and the remaining 10% were identified only as Salmonella species. Using the CLSI 2011 breakpoints for disc diffusion, 86% (43/50) were resistant to nalidixic acid(NA), 22% (11/50) to ciprofloxacin, 12% to azithromycin, 6% to cotrimoxazole, 4% to ampicillin and 1% to chloramphenicol. The MIC50 and MIC90 of ciprofloxacin for S.Typhi were 0.181 µg/mL and 5.06 µg/mL respectively. While the same for S. paratyphi A was 0.212µg/mL and 0.228µg/mL respectively. None of the isolates were multi drug resistant and all were susceptible to ceftriaxone. Using the CLSI 2012 revised ciprofloxacin breakpoints for disc diffusion (>31mm) & MIC (<0.06 µg/mL), 90% (45/50) of these isolates were found to be resistant.
Conclusion: MIC’s of ciprofloxacin should be reported for all salmonella isolates and should be used to guide treatment. Blindly following western guidelines for a disease which is highly endemic in the subcontinent will spell the death knell of a cheap and effective drug in our armamentarium. Therefore it will be too premature to declare that “the concept of using ciprofloxacin in typhoid fever is dead!”