Salmonella enterica outbreak in a banqueting hall in Jerusalem: the unseen hand of the epidemiological triangle?

BACKGROUND Foodborne Salmonella enterica outbreaks constitute both a threat to public health and an economic burden worldwide. OBJECTIVES To characterize the pathogen(s) involved and possible source of infection of an outbreak of acute gastroenteritis in a banqueting hall in Jerusalem. METHODS We conducted interviews of guests and employees of the banqueting hall, and analyzed food items, samples from work surfaces and stool cultures. RESULTS Of 770 persons participating in three events on 3 consecutive days at a single banqueting hall, 124 were interviewed and 75 reported symptoms. Salmonella enterica, serovar Enteritidis, phage type C-8, was isolated from 10 stool cultures (eight guests, one symptomatic employee and one asymptomatic employee) and a sample of a mayonnaise-based egg salad. Pulsed-field gel electrophoresis of the isolates revealed an identical pattern in the outbreak isolates, different from SE C-8 controls. A culture-positive asymptomatic employee was linked to all three events. After a closure order, allowing for cleaning of the banqueting hall, revision of food preparation procedures and staff instruction on hygiene, the banqueting hall was reopened with no subsequent outbreaks. CONCLUSIONS It is often difficult to pinpoint the source of infection in S. enterica outbreaks. Using molecular subtyping methods, a link was confirmed between patients, a food handler (presumably a carrier) and a food item--all showing an identical specific Salmonella enterica serovar Enteritidis. Testing asymptomatic as well as symptomatic food handlers in outbreak investigations is imperative. Pre- and post-hiring screening might be considered as preventive measures; hygiene and sanitation education are essential.