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

In May 1996, the Georgia Division of Public Health was notified about a clu ster of persons with Salmonella Enteritidis (SE) infections in Waycross, Ge orgia. A matched pair case-control study to determine risk factors for illn ess found a statistically significant association of SE infection with a hi story of having eaten at Restaurant A during the 5 days before onset of ill ness (relative risk = 13 [95% confidence interval (CI) = 3-62, P < 0.01]). In a second case-control study, to determine specific food exposures, consu mption 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 investigati on found evidence of suboptimal food storage and cooking temperatures at Re staurant A; cross contamination of foods may have contributed to the low at tributable 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 pa tient isolates and one food isolate from Restaurant A) for which phage typi ng was conducted, all were phage type 34. A FDA traceback investigation thr ough 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 Carol ina to minimize SE contamination of eggs.