True Prevalence of Shigellosis in Indian Children with Acute Gastroenteritis: Have We Been Missing the Diagnosis?

Background: Shigella is responsible for high morbidity and mortality among children, yet its true prevalence remains inconclusive. The aim of this study was to determine the actual prevalence of Shigella infection in childhood diarrhea and dysentery cases and assess the applicability of ipaH gene PCR in Indian settings. Methods: This study was conducted at Maulana Azad Medical College and associated Lok Nayak Hospital, New Delhi, India during 2011-12. A total of 385 children (207 with diarrhea, 118 with dysentery, and 60 matched controls) were enrolled. Stool samples were cultured, and the suspected colonies were analyzed using biochemical reactions and serotyping. Antimicrobial susceptibility testing was done using disc diffusion method. ipaH-gene PCR was performed directly on stool samples collected from 180 randomly selected patients (60 from each group). Results: Shigella was isolated using conventional culture methods in 8.2% (95% CI: 5.1%, 12.8%), 33.1% (95% CI: 25.2%, 42.0%), and 0% in the diarrhea, dysentery and control cases, respectively. High resistance was seen towards co-trimoxazole, nalidixic acid, fluoroquinolones, doxycycline and several beta-lactams drugs. Actual prevalence of shigellosis was determined using ipaH gene PCR to be 18.3% (95% CI: 10.4% – 30.1%) diarrhea cases and 56.7% (95% CI: 44.1, 68.4%) dysentery cases. One (1.7%, 95% CI: 0.01%, 9.7%) control specimen also yielded positive result in PCR. Conclusions: Correct diagnosis of shigellosis is essential to start antimicrobial therapy in selected cases. The prevalence of Shigella / EIEC infection in children is much higher than previously estimated. Despite its high costs and other limitations, we recommend the use of ipaH-gene PCR as a routine tool in the management of childhood acute gastroenteritis cases.