Table of Contents Author Guidelines Submit a Manuscript
BioMed Research International
Volume 2015, Article ID 191409, 10 pages
http://dx.doi.org/10.1155/2015/191409
Research Article

Molecular Epidemiology of Invasive Listeriosis due to Listeria monocytogenes in a Spanish Hospital over a Nine-Year Study Period, 2006–2014

1Instituto Tecnológico Agrario de Castilla y León, Valladolid, Spain
2Department of Clinical Microbiology, Complejo Asistencial Universitario de León, León, Spain
3Institute of Biomedicine (IBIOMED), University of León, León, Spain
4Public Health, School of Physiotherapy ONCE, Madrid, Spain
5Institute of Milk Hygiene, Milk Technology and Food Science, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria
6Microbiology Section, Department of Biotechnology and Food Science, Faculty of Sciences, University of Burgos, Burgos, Spain

Received 18 April 2015; Revised 23 June 2015; Accepted 1 July 2015

Academic Editor: Milton O. Moraes

Copyright © 2015 Jaime Ariza-Miguel et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We investigated the pathogenicity, invasiveness, and genetic relatedness of 17 clinical Listeria monocytogenes stains isolated over a period of nine years (2006–2014). All isolates were phenotypically characterised and growth patterns were determined. The antimicrobial susceptibility of L. monocytogenes isolates was determined in E-tests. Invasion assays were performed with epithelial HeLa cells. Finally, L. monocytogenes isolates were subtyped by PFGE and MLST. All isolates had similar phenotypic characteristics (β-haemolysis and lecithinase activity), and three types of growth curve were observed. Bacterial recovery rates after invasion assays ranged from 0.09% to 7.26% (1.62 ± 0.46). MLST identified 11 sequence types (STs), and 14 PFGE profiles were obtained, indicating a high degree of genetic diversity. Genetic studies unequivocally revealed the occurrence of one outbreak of listeriosis in humans that had not previously been reported. This outbreak occurred in October 2009 and affected three patients from neighbouring towns. In conclusion, the molecular epidemiological analysis clearly revealed a cluster (three human cases, all ST1) of not previously reported listeriosis cases in northwestern Spain. Our findings indicate that molecular subtyping, in combination with epidemiological case analysis, is essential and should be implemented in routine diagnosis, to improve the tracing of the sources of outbreaks.