APPLICATION OF MOLECULAR METHODS TO A NOSOCOMIAL OUTBREAK OF SALMONELLA-ENTERITIDIS PHAGE TYPE-4

A nosocomial outbreak of Salmonella enteritidis phage type 4 occurred in July 1995. Seven definite cases were identified over 13 days affect ing four wards in a London hospital. The outbreak strain was character ized by plasmid profile typing and pulsed-field gel electrophoresis (P FGE), and was unusual in that it did not possess a 38 MDa plasmid comm on to most isolates of S. enteritidis PT 4 made from humans and food a nimals in England and Wales. Seven asymptomatic excreters were identif ied on screening. No additional cases occurred on wards after standard isolation procedures were implemented. No common or continuing food o r dietary source was identified. Results of epidemiological, microbiol ogical and environmental investigations sugested that the outbreak was due to person-to-person transmission within the hospital. The source of the outbreak was not established but was probably due to admission of a patient with an unrecognized infection of S. enteritidis PT 4. Th e study highlights the importance of close collaboration between hospi tal staff, epidemiologists and microbiologists, and demonstrates the v alue of molecular techniques for strain subdivision in outbreak invest igations.