An in-depth investigation into a food poisoning outbreak.

Abstract

On and shortly after the 6th May 1990, 16 people were affected by food poisoning in an old peoples' residential home, of whom two died. The vehicle of infection was identified as a baked Alaska contaminated by Salmonella enteritidis phage type (PT) 8 and, at an early stage of the investigation, the source was attributed to a single infected egg. A separate investigation by the author, however, revealed that the baked Alaska meringue had been dispensed from an inadequately cleaned piping bag which had been recovered from the kitchen a month after the outbreak. A pure, profuse culture of S. enteritidis PT8 was isolated from it. At least one secondary case may have been attributable to food made with this bag. Ministry of Agriculture Investigations of the flocks suspected of producing the eggs used for the baked Alaska demonstrated an absence of S. enteritidis. On this basis, the author considered a more likely cause of the outbreak to be the piping bag, contaminated from source or sources unknown within the kitchen. Furthermore, the possibility of human carrier transmission cannot be wholly ruled out. The incident underlines the dangers of jumping to conclusions at the outset of food poisoning investigations and emphasises that hypotheses formulated on sources of contamination must be properly tested, the absence of which, in this instance, led the investigators to unwarranted conclusions as to the cause of the outbreak.