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Characterization of a collection of Enterobacter sakazakii isolates from environmental and food sources
Denise Drudy1, Michele O'Rourke, Mary Murphy
1Centre for Food Safety, School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
Abstract:
Enterobacter sakazakii has emerged as a rare cause of neonatal meningitis, septicemia and enterocolitis. Contaminated infant milk formula (IMF) has been identified as one infection route. A small number of clinical outbreaks have been epidemiologically linked to IMF contaminated post-pasteurization during manufacture and/or mishandled when reconstituted. Currently no agreed standardized typing protocol has been developed to trace E. sakazakii. The objectives of this study were to apply biochemical and genetic methods to characterize 51 environmental and food E. sakazakii isolates and 6 E. sakazakii type strains. Isolates were presumptively identified using biochemical profiles based on API 20E and ID32E methods and by culture on differential selective Druggan Forsythe Iversen (DFI) agar. Identification was subsequently confirmed by real time polymerase chain reaction (PCR). All but one of the isolates was identified as E. sakazakii by biochemical profiling. One isolate was identified as Escherichia vulneris by ID 32E and as Pantoea agglomerans by API 20E. All isolates produced green/blue colonies on DFI medium characteristic of this organism. Real time PCR could differentiate between E. sakazakii, Enterobacter spp. and other Enterobacteriacae. Analysis of RAPD banding patterns revealed 3 major clusters of E. sakazakii. There was a large degree of diversity noted amongst the remaining isolates. Our findings indicate that RAPD may be applied as a useful and reliable tool for direct comparison of E. sakazakii isolates providing traceability through the infant formula food chain.
Insights
A study on Enterobacter sakazakii found that Random Amplified Polymorphic DNA (RAPD) analysis can reliably trace this pathogen. This method helps track contamination in infant milk formula (IMF) to prevent outbreaks.
Area of Science:
- Microbiology
- Food Safety
- Molecular Biology
Background:
- Enterobacter sakazakii is a rare but serious cause of neonatal infections, including meningitis and septicemia.
- Contaminated infant milk formula (IMF) is a known transmission route, often linked to post-pasteurization contamination.
- A standardized method for tracing E. sakazakii strains is currently lacking.
Purpose of the Study:
- To characterize environmental and food isolates of E. sakazakii using biochemical and genetic techniques.
- To evaluate the utility of Random Amplified Polymorphic DNA (RAPD) analysis for E. sakazakii strain typing.
- To establish a reliable method for tracing E. sakazakii within the infant formula supply chain.
Main Methods:
- Biochemical profiling using API 20E and ID32E methods.
- Culture on differential selective Druggan Forsythe Iversen (DFI) agar.
- Identification confirmation via real-time polymerase chain reaction (PCR).
- Genetic characterization using Random Amplified Polymorphic DNA (RAPD) analysis.
Main Results:
- Biochemical methods and DFI agar successfully identified most E. sakazakii isolates, with PCR confirming identification.
- Real-time PCR effectively differentiated E. sakazakii from other Enterobacteriaceae.
- RAPD analysis revealed three major clusters of E. sakazakii, indicating genetic diversity and potential for strain differentiation.
Conclusions:
- RAPD analysis is a valuable and reliable tool for the direct comparison and tracing of E. sakazakii isolates.
- This method can enhance traceability throughout the infant formula food chain, aiding in outbreak investigation and prevention.
- Standardized molecular typing protocols are crucial for controlling E. sakazakii contamination in food products.
