Molecular Approaches for Isolation of Shigella Species from Culture Negative Diarrheal Samples: A Hospital Based Study in Bangladesh

Diarrhoeal infection is defined as a significant reason of morbidity as well as mortality all over the world. Isolation of Shigella, the most significant etiological agents of diarrhea in developing countries, was missing occasionally when patients feces are cultured by conventional procedures. The collected 200 samples from hospitalized diarrhoeal patients in Tangail district, Bangladesh during 2010-2011, Shigella were isolated from 24 (12%) samples utilizing conventional culture methods. Among176 culture negative stool samples,ipa H gene, specific marker to identify Shigella species was detected from 14 (8%) by PCR. Furthermore, these samples which possess the ipa H gene were cultured and identified as Shigella-like organism (s) by utilizing various phenotypic as well as molecular tools. Of 24 Shigella spp. which was identified using conventional culture methods, S. flexneri were dominant 41.7%, followed by S. boydii 29.2%, S. sonnei 25%, and S. dysenteriae 4.2%. Among 14 of 176 culture negative ipaH positive samples, 7 were identified as Shigella sspp., of which, 3 were S. flexneri, 1 was S. boydii, 2 were S. sonnei and 1 identified as a novel group of S. dysenteriae designated as KIVI 156. Additionally, all Shigella strains were resistant to ampicillin, sulfamethaxol-trimethoprime and were susceptible to ciprofloxacin and mecillinam. This study demonstrated that the conventional culture method cannot be referred as an adequate method to focus the actual disease burden caused by Shigella.