Detection of a nosocomial outbreak of salmonellosis may be delayed by application of a protocol for rejection of stool cultures

In October 2001 an outbreak of Salmonella enterica serovar enteritidis phage-type 6 occurred in a hospital and a nursing home, both served by the same hospital kitchen. Five nursing home residents died during the outbreak. S. enteritidis was isolated from three of them. Of 231 stool samples from nursing home residents, hospital patients and employees, 82 were culture-positive. All symptomatic patients were treated with oral ciprofloxacin. Inspection of the kitchen showed that during preparation of the desserts implicated in causing the outbreak, temperatures were not measured and storage temperatures were too high. No left-over food samples were available for analysis. According to the ‘four-day rule’ in use in this hospital, the stool samples related to the first outbreak were not cultured for Salmonella spp., whereas culturing afterwards from both stored specimens and repeats, showed that some of these samples would have been positive for S. enteritidis. Thus without the application of stool culture rejection criteria the outbreak would have been detected one day earlier. With the four-day rule in effect, the outbreak might have been detected much later, if an unusually high number of nursing home residents with gastroenteritis had not been noticed by nursing home physicians. The rule was revised to prevent a possible delay in the future. As a result of this outbreak, the government has announced legislation forbidding the sale of Salmonella-contaminated eggs. An official ban on the use of raw eggs will be included in several hygiene codes.