Dose–response effects in an outbreak of Salmonella enteritidis

Abstract

SummaryThe effects of ingested Salmonella enteritidis (SE) dose on incubation period and on the severity and duration of illness were estimated in a cohort of 169 persons who developed gastroenteritis after eating hollandaise sauce made from grade–A shell eggs. The cohort was divided into three groups based on self–reported dose of sauce ingested. As dose increased, median incubation period decreased (37 h in the low exposure group 21 h in the medium exposure group v. 17·5 h. in the high exposure group, P = 0.006) and greater proportions reported body aches (71 v. 85 v. 94%, P = 0.0009) and vomiting (21 v. 56 v. 57%, P = 0.002). Among 118 case-persons who completed a follow–up questionnaire, increased dose was associated with increases in median weight loss in kilograms (3.2 v. 4.5 v. 5.0, P = 0.0001), maximum daily number of stools (12.5 v. 15.0 v. 20.0, P = 0.02), subjective rating of illness severity (P = 0.0007), and the number of days of confinement to bed (3.0 v. 6.5, P = 0.04). In this outbreak, ingested dose was an important determinant of the incubation period, symptoms and severity of acute salmonellosis.