Characterization of enterotoxigenic Escherichia colistrains isolated from Nicaraguan children in hospital primarycare and community settings

摘要

Enterotoxigenic Escherichia coli (ETEC) is one of the most common causes of diarrhoea among young children in developing countries. ETEC vaccines offer promise in reducing the burden of ETEC disease, but the development of these vaccines relies on the characterization of ETEC isolates from a variety of settings. To best reflect the full spectrum of ETEC disease in León, Nicaragua, the aim of this study was to characterize ETEC strains isolated from children with diarrhoea attending different settings (hospital, primary care clinics and in the community) and children from different age groups. We characterized ETEC isolates in terms of their colonization factors (CFs) and enterotoxins, and determined whether these factors varied with setting and age group. Diarrhoeal stool samples were obtained from children under the age of 60 months from: (1) the regional public hospital, (2) four public primary care clinics, and (3) a population-based cohort. In total, 58 ETEC-positive isolates were analysed by multiplex-PCR assays for the identification of CFs (CS1, CS2, CS3, CS4, CS5, CS6, CS7, CS8, CS12, CS13, CS14, CS15, CS17, CS18, CS19, CS20, CS21, CS22 and CFA/I), and enterotoxins [heat-labile toxin (LT) and heat-stable variants STh and STp]. The frequency of CFs and enterotoxins wascompared among the three settings and for different age groups, usingFisher’s exact test or a χ² test. At least one CF wasdetected among one-half of samples; CS19 was detected among all strains in whicha CF was identified, either alone or in combination with another CF. Among allCFs detected, 91.7 % were identified as members of the class 5 fimbrialfamily. CFs were detected more commonly among samples from infants captured inthe health facility setting compared with the community setting. Overall, LT wasdetected among 67.2 % of samples, STh was detected among 20.7 %and both enterotoxins were detected among 12.1 %. The enterotoxin SThwas detected more commonly among cases in the community, whilst a combination ofSTh and LT was detected more commonly among cases treated in health facilities.Our results suggest that, to protect against diarrhoeal cases associated withthis E. coli pathotype in León, Nicaragua, an ETECvaccine that effectively targets the archeotype CFA/I of the class 5 fimbrialfamily would be the most effective in this setting.