Abstract
Listeria monocytogenes is a major human foodborne pathogen that is prevalent in the natural environment and has a high case fatality rate. Whole genome sequencing (WGS) analysis has emerged as a valuable methodology for the classification of L. monocytogenes isolates and the identification of virulence islands that may influence infectivity. In this study, WGS was used to provide an insight into 25 L. monocytogenes isolates from cases of clinical infection in Ireland between 2013 and 2015. Clinical strains were either lineage I (14 isolates) or lineage II (11 isolates), with 12 clonal complexes (CC) represented, of which CC1 (6) and CC101 (4) were the most common. Single nucleotide polymorphism (SNP) analysis demonstrated that clinical isolates from mother–infant pairs (one isolate from the mother and one from the infant) were highly related (3 SNP differences in each) and also identified close similarities between isolates from otherwise distinct cases (1 SNP difference). Clinical strains were positive for common virulence-associated loci and 13 isolates harbour the LIPI-3 locus. Pulsed-field gel electrophoresis (PFGE) was used to compare strains to a database of 1300 Irish food and food processing environment isolates and determined that 64% of clinical pulsotypes were previously encountered in the food or food processing environment. Five of the matching food and food processing environment isolates were sequenced and results demonstrated a correlation between pulsotype and genotype. Overall, the work provides insights into the nature of L. monocytogenes strains currently causing clinical disease in Ireland and indicates that similar isolates can be found in the food or food processing environment.
Highlights
Listeria monocytogenes is the causative agent of listeriosis, a serious infection that can manifest as meningitis and/or septicaemia in adults, infection of the fetus and miscarriage in pregnant women, or neonatal infection [1,2]
The objectives of this study were to use Whole genome sequencing (WGS) to characterise virulence determinants of Irish clinical L. monocytogenes isolates, in order to compare a variety of methods for determining relatedness of the isolates (PFGE, sequence type (ST), clonal complex (CC), core genome and Single nucleotide polymorphism (SNP) analysis) and to relate clinical isolates to a selection of food/food processing environment isolates from a three year longitudinal study [21]
Whole genome sequencing of L. monocytogenes isolates from cases of human listeriosis in Ireland between 2013 and 2015 has provided an overview of locally circulating clinical strains of the pathogen
Summary
Listeria monocytogenes is the causative agent of listeriosis, a serious infection that can manifest as meningitis and/or septicaemia in adults, infection of the fetus and miscarriage in pregnant women, or neonatal infection [1,2]. The disease is relatively rare, listeriosis is severe, with high hospitalisation and mortality rates [1,3]. In 2014, there were 2161 confirmed cases of human listeriosis in the European Union (EU) [4]. The fatality rate among 1524 confirmed cases with known outcome was 17.7% (270 cases), indicating the potential for this pathogen to pose a significant public health concern. In Ireland, listeriosis is a notifiable disease and the number of reported cases has been subject to an increase recently from eight cases in 2013, 15 cases in 2014 to 19 cases in 2015. A recent report suggests a trend towards an increased percentage of cases in adults (in particular adults over 65 years of age), which present as blood stream infection or meningitis [5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
