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Epidemiology and Infection logoLink to Epidemiology and Infection
. 1999 Apr;122(2):209–215. doi: 10.1017/s0950268899002216

A Mexican restaurant-associated outbreak of Salmonella Enteritidis type 34 infections traced to a contaminated egg farm.

M M McNeil 1, L B Sweat 1, S L Carter Jr 1, C B Watson 1, J T Holloway 1, R Manning 1, S F Altekruse 1, P A Blake 1
PMCID: PMC2809608  PMID: 10355784

Abstract

In May 1996, the Georgia Division of Public Health was notified about a cluster of persons with Salmonella Enteritidis (SE) infections in Waycross, Georgia. A matched pair case-control study to determine risk factors for illness found a statistically significant association of SE infection with a history of having eaten at Restaurant A during the 5 days before onset of illness (relative risk = 13 [95% confidence interval (CI) = 3-62, P < 0.01]). In a second case-control study, to determine specific food exposures, consumption of a deep-fried Mexican dish (chile relleno) (4 of 21 cases vs. 0 of 26 controls, odds ratio undefined, 95% CI > 1.46, P = 0.034) was found to be significantly associated with SE infection. An environmental investigation found evidence of suboptimal food storage and cooking temperatures at Restaurant A; cross contamination of foods may have contributed to the low attributable risk identified for chile rellenos. Five of 37 Restaurant A food and environment specimens yielded SE strains. All five positive specimens were from chiles rellenos. Of the seven outbreak-associated strains (six patient isolates and one food isolate from Restaurant A) for which phage typing was conducted, all were phage type 34. A FDA traceback investigation through Restaurant A's single-egg supplier identified the potential source as three interrelated farms in South Carolina. Environmental culture from one of these farms yielded SE phage type 34. As a result of this outbreak, FDA helped institute a statewide egg quality-assurance programme in South Carolina to minimize SE contamination of eggs.

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