Genome-Based Characterization of Listeria monocytogenes, Costa Rica

Genomic data on the foodborne pathogen Listeria monocytogenes from Central America are scarce. We analyzed 92 isolates collected during 2009–2019 from different regions in Costa Rica, compared those to publicly available genomes, and identified unrecognized outbreaks. Our findings suggest mandatory reporting of listeriosis in Costa Rica would improve pathogen surveillance.

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Bacterial Isolation
The study included 92 L. monocytogenes isolates previously collected from different regions throughout Costa Rica (Figure in main manuscript; Appendix Table 1) and spanning Bacterial isolation was performed as described previously, following either the Bacteriological Analytical Manual method for Listeria isolation (1), for isolates obtained by the UCR, ITCR and SENASA, or the ISO 11290-1:2017 method (2), for isolates obtained by the
Minimum spanning trees were obtained from MLST and cgMLST profiles using BioNumerics v.
eleven years (2009-2019).Clinical isolates (n = 16) were obtained by the Institute for Research and Teaching in Nutrition and Health (INCIENSA) in the context of the activities of the Costa Rican National Clinical Laboratory Network, comprised by laboratories of major hospitals, clinical settings, and the University of Costa Rica (UCR).Even though L. monocytogenes is not a notifiable disease in the country, there is an established criterium where bacterial pathogens that cause meningitis are sent to INCIENSA for confirmation of identification as well as antibiotic susceptibility tests.Isolates from food and food-production environments (n = 76) were obtained by the National Laboratory of Veterinary Services (LANASEVE) of National Animal Health Service (SENASA), which performs microbiology analysis for the surveillance of food safety in products of animal origin for human consumption, by the INCIENSA that also monitors the microbiological quality of food for human consumption, and by the UCR and the Instituto Tecnológico de Costa Rica (ITCR) in the scope of research projects and/or routine analyses for customers, as well as in the framework of a specific study to investigate Listeria spp.strains previously isolated by private entities regulated and accredited by the international standard INTE/ISO/IEC 17025:2017 for microbiological analysis that guarantee the results of their sampling process.
35°C overnight before use.DNA extraction was performed with the DNeasy Blood & Tissue Kit (QIAGEN, København Ø, Denmark-confirm), according to the instructions provided by the manufacturer.Qubit fluorometer (Thermo FisherScientific, Waltham, MA, USA) was used to evaluate DNA quantity and purity.Library preparation was performed with the Nextera XT DNA Sample Kit (Illumina, San Diego, CA, USA), and DNA sequencing was carried out on a

Table 1 .
Isolate metadata and genome metrics of Listeria monocytogenes sequenced in this study (n = 92). Appendix