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 v. 21 h in the medium exposure group v. 17T5 h in the high exposure group, P = 0 006) and greater proportions reported body aches (71 v. 85 v. 94 %, P = 00009) and vomiting (21 v. 56 v. 57%, P = 0002). Among 118 casepersons 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 (30 v. 6-5 v. 65, P = 004). In this outbreak, ingested dose was an important determinant of the incubation period, symptoms and severity of acute salmonellosis.

Growth potential of Salmonella spp. and Listeria monocytogenes in nine types of ready-to-eat vegetables stored at variable temperature conditions during shelf-life

“…Although the infectivity of Salmonella is highly variable (Mintz et al, 1994;Musher and Musher, 2004), the infection by L. monocytogenes seems to be mostly associated with ingestion of high doses of this pathogen in healthy individuals (>8 log CFU) or with low doses in susceptible individuals (2-3 log CFU) (Takeuchi et al, 2006;Williams et al, 2007;Warriner and Namvar, 2009). Given this, the knowledge of growth potential (δ) in RTE vegetables can be very useful to identify critical storage conditions to be respected to prevent the growth of pathogens in these products to unacceptable levels.…”

An Outbreak ofSalmonellaSerotype Typhimurium Infections with an Unusually Long Incubation Period

“…Although this is the longest incubation period reported to the CDC for a Typhimurium-related foodborne outbreak, outbreaks of illnesses with unusually long incubation periods have been previously described for this (Seals et al, 1983) and other non-typhoidal Salmonella serotypes (Ethelberg et al, 2004;Matsui et al, 2004;Nagai et al, 1999;O'Mahony et al, 1990). In some other studies, incubation periods for enteric infections with non-typhoidal Salmonella have been correlated with the dose of bacteria consumed (Abe et al, 2004;Blaser and Newman, 1982;Glynn and Palmer, 1992;Mintz et al, 1994).…”

Current trends in typhoid fever

“…The infectious dose has been estimated as 10 5 to 10 9 organisms. With a higher inoculum, the clinical symptoms are unchanged, but the likelihood of clinical illness is greater, and the incubation period is shortened [36,37]. Histologically, aggregates of infected macrophages, called typhoid nodules, occur in the intestine, liver, spleen, and many other organs.…”