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Application of molecular methods to a nosocomial outbreak of Salmonella enteritidis phage type 4
1PHLS Communicable Disease Surveillance Centre, London, UK.
Abstract:
A nosocomial outbreak of Salmonella enteritidis phage type 4 occurred in July 1995. Seven definite cases were identified over 13 days affecting four wards in a London hospital. The outbreak strain was characterized by plasmid profile typing and pulsed-field gel electrophoresis (PFGE), and was unusual in that it did not possess a 38 MDa plasmid common to most isolates of S. enteritidis PT 4 made from humans and food animals in England and Wales. Seven asymptomatic excreters were identified on screening. No additional cases occurred on wards after standard isolation procedures were implemented. No common or continuing food or dietary source was identified. Results of epidemiological, microbiological and environmental investigations suggested 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. The study highlights the importance of close collaboration between hospital staff, epidemiologists and microbiologists, and demonstrates the value of molecular techniques for strain subdivision in outbreak investigations.
Insights
A hospital outbreak of Salmonella enteritidis phage type 4 was investigated. Person-to-person transmission was identified as the likely cause, highlighting the need for rapid response and molecular typing in healthcare settings.
Area of Science:
- Infectious Diseases
- Epidemiology
- Microbiology
Background:
- Nosocomial outbreaks pose significant challenges in healthcare settings.
- Salmonella enteritidis phage type 4 (PT 4) is a recognized pathogen.
- Effective outbreak investigation requires multidisciplinary collaboration.
Purpose of the Study:
- To investigate a nosocomial outbreak of Salmonella enteritidis PT 4.
- To identify the transmission route and contributing factors.
- To evaluate the utility of molecular typing in outbreak management.
Main Methods:
- Epidemiological investigation including case finding and contact screening.
- Microbiological analysis including plasmid profiling and pulsed-field gel electrophoresis (PFGE).
- Environmental and dietary source assessment.
Main Results:
- Seven cases of Salmonella enteritidis PT 4 infection were identified across four hospital wards.
- The outbreak strain lacked a 38 MDa plasmid, distinguishing it from common strains.
- Seven asymptomatic carriers were detected; person-to-person transmission was the probable route.
- Standard isolation procedures halted further cases.
Conclusions:
- Person-to-person transmission was the likely cause of the hospital outbreak.
- Molecular techniques like PFGE are valuable for differentiating strains during outbreaks.
- Prompt implementation of infection control measures is crucial for containing nosocomial spread.
- Collaboration between clinical staff, epidemiologists, and microbiologists is essential for effective outbreak response.