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Open Access Highly Accessed Methodology article

Fluorescence amplified fragment length polymorphism compared to pulsed field gel electrophoresis for Listeria monocytogenes subtyping

Sophie Roussel1*, Benjamin Félix1, Kathie Grant2, Trinh Tam Dao1, Anne Brisabois1 and Corinne Amar2

Author Affiliations

1 ANSES, Maisons-Alfort Laboratory for Food Safety, Bacterial Characterization and Epidemiology Unit, 23, avenue du Général de Gaulle, MAISONS-ALFORT cedex, 94706, France

2 Health Protection Agency, Gastrointestinal Bacteria Reference Unit, 61 Colindale Avenue, London, NW9 5EQ, UK

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BMC Microbiology 2013, 13:14  doi:10.1186/1471-2180-13-14

Published: 24 January 2013

Abstract

Background

Listeriosis is a severe infection which mainly affects pregnant women, neonates and immuno-compromised adults. ANSES’s Laboratory for Food safety has been the European Union Reference Laboratory (EURL) for L. monocytogenes in the food chain since 2006. Pulsed Field Gel Electrophoresis (PFGE) is routinely used in the EURL for the surveillance of L. monocytogenes isolated from foods, animals and the environment. One of the main EURL activities is to evaluate alternative molecular subtyping methods to PFGE, and integrate their use within the National Reference Laboratories (NRL) network. Since 2008, the United Kingdom (UK)-NRL for L. monocytogenes at the Health Protection Agency (HPA), London, has used fluorescent Amplified Fragment Length Polymorphism (fAFLP) for the routine surveillance of L. monocytogenes isolated from human clinical cases, food and food processing environments in the UK. This study compares fAFLP with PFGE for subtyping L. monocytogenes.

Results

A panel of 109 L. monocytogenes isolates from either human cases of listeriosis, foods, food processing environments and animals were used for the comparative evaluation. Among these, 2 strains were tested from duplicate culture by both methods. The panel also included field isolates, isolates associated with outbreaks or sporadic cases and reference strains. The two strains tested in duplicate displayed the same fAFLP and PFGE types. Strains known to be epidemiologically associated with one another were found to have unique PFGE and fAFLP types. FAFLP and PFGE divided the strains into 76 and 82 distinct profiles, or types, respectively. The discriminatory index calculated was 0.993 and 0.996 for fAFLP and PFGE, respectively.

Conclusions

The discriminatory ability of fAFLP was similar to that of PFGE for the subtyping of L. monocytogenes isolates. As a less labour intensive technique fAFLP may be a better method to use than PFGE in investigating outbreaks of human listeriosis and tracking the source of contamination in food processing facilities in real time.

Keywords:
fAFLP; PFGE; Molecular subtyping; Listeria monocytogenes; Discriminatory power