Stool shedding of Salmonella Typhi in children with blood culture-confirmed typhoid fever

Abstract

Background: Shedding of Salmonella Typhi in stool following symptomatic or asymptomatic infections may play a substantial role in the transmission of typhoid fever. This study estimated the proportion of children shedding S. Typhi in stool during and after an episode of typhoid fever, as well as shedding among members of their household. Methods and materials: The study was nested within a paediatric cohort of the Surveillance for Enteric Fever in India (SEFI) study, Vellore, where 6000 children are under active surveillance for fever. As per the study protocol, children with fever for ≥3 days receive a blood culture and receive azithromycin therapy, if the culture grew S. Typhi. Children positive for S.Typhi were requested to provide stool samples (3 samples/week) over the next three weeks. Concurrently, three stool samples were also collected from each of the household contacts of these children, for screening S. Typhi. The STY0201 gene was detected using Real-time Polymerase Chain Reaction (RT-PCR). Clinical characteristics of children with blood culture-confirmed typhoid fever who shed S. Typhi and did not were compared. Results: Of 65 children with blood culture-confirmed typhoid fever between November 2018 to July 2019, 58(89.2%) children from 53 households consented to provide stool samples. Of these 58 children, 15(25.9%) shed S. Typhi, with a median time (IQR) of shedding at 17(11-24) days from the onset of fever and three of these 15, shed S. Typhi again at a median interval of 30 days from the onset of fever. History of hospitalization during the typhoid fever episode was associated with shedding S. Typhi [OR: 6.6(95% CI:1.5-29)]. Eight(15.1%) of the 53 households with a case of typhoid fever had at least one family member shedding S. Typhi, of whom five were asymptomatic and remaining three had a recent history of fever. Conclusion: One in four children shed S.Typhi during and after the typhoid fever and severity of illness was associated with shedding. About 15% of the households with a child with typhoid fever had a family member shedding S. Typhi concurrently. Thus, it is recommended to consider these parameters while studying disease transmission in endemic settings.