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Open Access Highly Accessed Research article

Development of stable reporter system cloning luxCDABE genes into chromosome of Salmonella enterica serotypes using Tn7 transposon

Kevin Howe1, Attila Karsi23, Pierre Germon4, Robert W Wills1, Mark L Lawrence23* and Richard H Bailey1*

Author Affiliations

1 Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA

2 Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA

3 Institute for Digital Biology, Mississippi State University, Mississippi State, MS 39762, USA

4 INRA, UR 1282 Infectiologie Animale et Santé Publique, Laboratoire de Pathogénie Bactérienne, Nouzilly, France

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BMC Microbiology 2010, 10:197  doi:10.1186/1471-2180-10-197

Published: 23 July 2010

Abstract

Background

Salmonellosis may be a food safety problem when raw food products are mishandled and not fully cooked. In previous work, we developed bioluminescent Salmonella enterica serotypes using a plasmid-based reporting system that can be used for real-time monitoring of the pathogen's growth on food products in short term studies. In this study, we report the use of a Tn7-based transposon system for subcloning of luxCDABE genes into the chromosome of eleven Salmonella enterica serotypes isolated from the broiler production continuum.

Results

We found that the lux operon is constitutively expressed from the chromosome post-transposition and the lux cassette is stable without external pressure, i.e. antibiotic selection, for all Salmonella enterica serotypes used. Bioluminescence expression is based on an active electron transport chain and is directly related with metabolic activity. This relationship was quantified by measuring bioluminescence against a temperature gradient in aqueous solution using a luminometer. In addition, bioluminescent monitoring of two serotypes confirmed that our chicken skin model has the potential to be used to evaluate pathogen mitigation strategies.

Conclusions

This study demonstrated that our new stable reporting system eliminates bioluminescence variation due to plasmid instability and provides a reliable real-time experimental system to study application of preventive measures for Salmonella on food products in real-time for both short and long term studies.