Listeria monocytogenes, a silent foodborne pathogen in Ecuador.

Listeria monocytogenes is a foodborne pathogen that can produce serious, even fatal, infections. Among other foods, it can be found in unpasteurized dairy and ready-to-eat products. Surveillance of L. monocytogenes is of great interest since sources of infection are difficult to determine due to the long incubation period, and because the symptoms of listeriosis are similar to other diseases. We have performed a genomic study of L. monocytogenes isolated from fresh cheeses and clinical samples. Sixty-five isolates were evaluated and sequenced, 14 isolates from cheese samples and 20 from clinical listeriosis cases from the National Institute of Public Health, and 31 isolates from artisanal cheese samples from 8 provinces.All isolates were sensitive to penicillin, ampicillin, erythromycin, trimethoprim/sulfamethoxazole, and meropenem. They exhibited heterogeneous patterns of presence of pathogenicity islands. All isolates exhibit at least 4 genes from LIPI-1, but all references (26 L. monocytogenes closed genomes available in NCBI database) showed the complete island, which encompasses 5 genes, and present in only two Ecuadorian isolates. Most isolates lack gene actA. Genes from LIPI-2 were absent in all isolates. LIPI-3 and LIPI-4 were only present in a few references and isolates. With respect to the stress survival islets, our samples either presented SSI-1 or SSI-F2365, except for one isolate that presented SSI-F2365 but also one gene from SSI-1. None of the samples presented SSI-2.The predominant ST was ST2 (84.62% 55/65), and the only ST found in food (93.33% 42/45) and clinical samples (65% 13/20). Isolates did not group according to their sampling origin, date or place in a phylogenetic tree obtained form the core alignment. The presence of ST2 in food and clinical samples, with high genomic similarity, suggests a foodborne infection risk linked to the consumption of fresh cheeses in Ecuador.