Epidemiological and clinical characteristics of shigellosis in rural Bangladesh

Abstract

Some epidemiological and clinical characteristics of 292 patients infected with Shigella spp in a sample of 2,635 diarrhoea patients are described. The sample consisted of every fifth of all patients who came for free treatment between May 1983 and April 1984 at the Matlab Field Hospital of the International Centre for Diarrhoeal Disease Research, Bangladesh. A little more than half of them belonged to the age groups of 1-4 years (31.3%) and 5-14 years (20.4%), and more than half (56.4%) were males. Of the 292 patients yielding Shigella spp in their stools, the predominating isolates were Shigella dysenteriae type 1 (181; 62%) and S. flexneri (79; 27.1%) respectively. Of the stool samples from 1,318 patients examined for Campylobacter, 148 (11.2%) were culture-positive for only Campylobacter jujuni. Shigella spp were isolated most frequently from patients aged 1 -2 years (154/1000), and in patients aged 60 years or more (147/1000), and least frequently in children under one year of age (58/1000). Compared with the genus as a whole, S. dysenteriae type 1 was isolated most frequently in patients aged 5-9 years (94/1000) and 10-14 years (116/1000) and more frequently from males (8.4%) trmn from females (4.9%; X2=13.0; p<.001). Two peaks of shigellosis were observed, one during June-September caused by S. dysenteriaelype 1, and the other in December caused by S. flexneri. Blood was visible to the naked eye in 68% of the faeces positive for Shigella spp (in 87% of faeces positive for S. dysenteriae type 1) on culture, but in only 18% of samples showing Entamoeba histolytica, in 18% of samples positive for C. jejunion culture and 12% of samples from the remaining patients. Stool samples positive for Shigella spp on culture were more often alkaline than those from patients yielding other pathogens (251/276 vs 1580/2052; X2=28.3; p<0.001). Patients infected with S. dysenteriae type 1 were more likely to have bloody stools than patients infected with other species of Shigella (150/181 vs 40/111; X2=77.8; p<0.0001). Patients with shigellosis less frequently presented with moderate-to-severe dehydration (53/292 vs 1182/2343; X2=108.9; p<0.0001), but required antibiotics more often (245/292 vs 1429/2343; X2=58.8; p<0.0001). Patients infected with S. dysenteriae type 1 required antibiotics more frequently than those infected with other species of Shigella (166/181 vs 79/111; X2=21.5; p<0.001). Salient findings, like the S. dysenteriae type 1 as the dominating isolate in place of S. flexneri observed earlier; two peaks of shigellosis, instead of one, known previously; similar value of the naked eye as well as the microscopic presence of blood in faeces as a diagnostic aid in shigellosis; antibiogram pattern of shigella isolates, etc., including their implications, are discussed.