Surveillance of changing antimicrobial resistance pattern in Shigella in North India

Diarrhea and dysentery are responsible for immense morbidity and mortality in developing countries, with Shigella spp. being one of the common bacterial causes. Rising trends in antimicrobial resistance rates pose a significant problem in treatment. Therefore, this study was undertaken to analyze the current situation in vitro drug resistance of Shigella spp. Stool samples were received from 7377 patients of all age groups presenting with signs and symptoms of diarrhea or dysentery from 1st January 2009 to 31st December 2012. Causative organisms were identified by routine microscopic examination, culture techniques and serotyping, followed by susceptibility testing according to CLSI guidelines. Shigella spp. were isolated in 143/7377 (1.94%) cases with following distribution: S. flexneri (89/143, 62.2%), S. boydii (36/143, 25.2%), S. sonnei (22/143, 15.4%) and S. dysenteriae (2/143, 1.4%). 119 (83.2%) strains were multidrug resistant to three or more agents. High resistance rates were seen for cotrimoxazole (90.9%), nalidixic acid (90.9%) doxycycline (88.8%), ofloxacin (56.6%) and ciprofloxacin (53.8%). Resistance to third generation cephalosporins was 18.9-20.3%. All strains were susceptible to piperacillin-tazobactam combination and carbapemens. Antimicrobial agents like sulphonamides, tetracyclines, amplicillin, cotrimoxazole and nalidixic acid have been popular choices in past. Current drug of choice is ciprofloxacin, however more than half of the strains showed resistance. The third generation cephalosporins are being used with increasing frequency in such cases resulting in emergence of significant resistance to this class as well. Current scenario suggests change in the drug of choice from ciprofloxacin to oral third generation cephalosporin for severe cases.