Discriminatory Usefulness of Pulsed-Field Gel Electrophoresis and Sequence-Based Typing in Legionella Outbreaks

Abstract

Aim: To compare the discriminatory power of pulsed-field gel electrophoresis (PFGE) and sequence-based typing (SBT) in Legionella outbreaks for determining the infection source. Materials & methods: Twenty-five investigations of Legionnaires’ disease were analyzed by PFGE, SBT and Dresden monoclonal antibody. Results: The results suggested that monoclonal antibody could reduce the number of Legionella isolates to be characterized by molecular methods. The epidemiological concordance PFGE–SBT was 100%, while the molecular concordance was 64%. Adjusted Wallace index (AW) showed that PFGE has better discriminatory power than SBT (AW_SBT→PFGE = 0.767; AW_PFGE→SBT = 1). The discrepancies appeared mostly in sequence type (ST) 1, a worldwide distributed ST for which PFGE discriminated different profiles. Conclusion: SBT discriminatory power was not sufficient verifying the infection source, especially in worldwide distributed STs, which were classified into different PFGE patterns.

KEYWORDS:

• congruence
• discriminatory power
• Legionella
• molecular-epidemiology outbreaks
• PFGE
• SBT
• typing

Supplementary Data

Acknowledgements

The authors would like to thank the Subdireccció general de Vigilància i Resposta a Emergències de Salut Pública and the technicians from the Equip Territorial de Salut Pública del Departament de Salut de la Generalitat de Catalunya for the support received and for providing the samples. They also thank N Fry and T Harrison for helpful advice about sequence-based typing and assigning the alleles newly identified by the authors.

Disclosure

Part of this work was presented at the First European Study Group for Legionella Infections (ESGLI) Meeting held in Dresden, Germany on 5–7 September 2012.

Financial & competing interests disclosure

The present study was funded by the project PI10/0191, integrated in the National R + D + I and funded by the ISCIII-General Evaluation Branch and the European Regional Development Fund (ERDF) by CIBER de Enfermedades Respiratorias (CIBERES). CIBERES is an initiative of Instituto de Salud Carlos III. S Quero was funded by CIBERes and FI-AGAUR (FI-AGAUR 2012). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Additional information

Funding

The present study was funded by the project PI10/0191, integrated in the National R + D + I and funded by the ISCIII-General Evaluation Branch and the European Regional Development Fund (ERDF) by CIBER de Enfermedades Respiratorias (CIBERES). CIBERES is an initiative of Instituto de Salud Carlos III. S Quero was funded by CIBERes and FI-AGAUR (FI-AGAUR 2012). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.