Byline: Pavithra. Jain, R. Kulkarni, S. Dutta, Ajanta. Ganavali, Anuradha. Kalabhavi, Praveen. Shetty, C. Shubhada, Manjunath. Hosamani, Suma. Appannanavar, Deepa. Hanamaraddi
Context: Shigella is a common cause of bacillary dysentery. Although it is reported worldwide, the majority of the infections are seen in developing countries with Shigella flexneri being the most common isolate. Prevalence of Shigella species and their antibiotic susceptibility profiles vary according to geographic area and season. Aims: In the present study, the epidemiology and antimicrobial profile of Shigella from stool samples received at our hospital for a period of 12 years (January 2006 to December 2017) was evaluated. Subjects and Methods: A total of 4578 stool samples were collected from the cases of acute gastroenteritis and diarrhoea. Samples were processed for culture and sensitivity according to standard microbiological techniques. The presumptive identification of Shigella species was done using standard conventional biochemical tests and confirmed using antisera. Results: A total of 189 (4.2%) samples yielded Shigella spp. Isolation of Shigella spp. were more frequent from males (58.2%). S. flexneri was the commonest species isolated (47.6%) followed by Shigella sonnei(11.6%), Shigella dysenteriae (4.2%) and Shigella boydii (2.1%). Non-typeable Shigella was commonly recovered. The isolates showed high resistance to ampicillin (76.7%) and co-trimoxazole (75%) while highest susceptibility was observed to ceftriaxone (79.2%). Conclusions: S. flexneri was the most prevalent species isolated at this centre. Shigella isolates from the study showed alarming resistance to recommended antibiotics. Non-typeable Shigella accounted for 34.4% isolates. Molecular discrimination between Shigella and Escherichia coli is essential.
The genus Shigella is a group of Gram-negative non-spore-forming bacilli belonging to the family Enterobacteriaceae and is further divided into four species, namely, Shigella dysenteriae, Shigella flexneri , Shigella boydii and Shigella sonnei . Shigella spp. cause mild diarrhoea to fulminant dysentery. Shigellosis commonly causes high morbidity and mortality in children <5 years of age in developing countries. Shigellosis is seen in both endemic and epidemic forms worldwide. The lack of safe water, poor hygiene, close personal contact and malnutrition play an important role in the transmission of Shigella . Rainfall and temperature also contribute to the endemicity of shigellosis.
The primary mode of transmission of this highly infectious pathogen is faeco-oral and as low as 10-100 bacilli may initiate a clinical infection. Shigella colonises and invades the intestinal epithelium leading to disruption of colonic mucosa. Loose motions, abdominal cramps, fever, tenesmus are the cardinal features of shigellosis.
True prevalence of Shigella cannot be estimated reliably as most infections are mild and self-limiting, not needing medical attention or laboratory evaluation. In addition, the sensitivity of culture is low because of low bacterial load or prior antibiotic therapy as well as poor transportation of samples. As per reports, estimated annual mortality of 35,000-40,000 is noted globally in both under five and older than 5 years age groups., The number of Shigella -related deaths in Asia has substantially decreased due to current non-specific interventions, including measles vaccination, Vitamin A supplementation and improved nutrition.
S. flexneri is prevalent in developing countries from...