Antibiotic susceptibility pattern of Shigella isolates in a tertiary healthcare center

Background and objectives: Shigellosis is one of the most common causes of morbidity and mortality in children in developing countries. To the best of our knowledge, there is no published data in the study area on the antimicrobial susceptibility pattern and prevalence of Shigella species among diarrheagenic cases. Therefore, a retrospective analysis was done to find the Shigella serotypes, common age group affected, and antimicrobial resistance pattern of Shigella isolates in South Kerala.

Methods: Stool samples collected from cases of dysentery and diarrhea from January 2011 to December 2016 were processed. Standard bacteriological methods were used to isolate, identify, and determine the antimicrobial susceptibility pattern of Shigella isolates. The data were analyzed using SPSS version 16.

Results: Among 1585 stool samples, 48(3%) yielded Shigella. The most common serogroup isolated was Shigella sonnei (62.5%) followed by Shigella flexneri. Of 48 isolates, 44(91.6%) isolates were found to be multidrug resistant. Over the 5-year period, the isolates show 100% resistance to nalidixic acid, ciprofloxacin, and cotrimoxazole. Eight isolates were found to be resistant to ceftriaxone and cefotaxime. The presence of Extended spectrum betalactamase (ESBL) was phenotypically confirmed in five isolates.

Conclusion: Even though S. flexneri is the most common Shigella-causing diarrhea, S. sonnei was found to be the most important species responsible in our study. Multidrug resistance was common (91.6%) and the most common multidrug resistance profile was ampicillin-nalidixic acid-cotrimoxazole-ciprofloxacin. Regular monitoring of antibiotic susceptibility pattern including detection of beta lactamases should be done in all microbiology laboratories. Guidelines for therapy should be monitored and modified based on regional susceptibility reports.