Genetic Characteristics of Japanese Clinical Listeria monocytogenes Isolates

Abstract

Listeria monocytogenes causes foodborne illnesses through consumption of ready-to-eat foods. Although 135-201annual listeriosis cases have been estimated in Japan, the details regarding the clinical isolates such as infection source, virulence level, and other genetic characteristics, are not known. In order to uncover the trends of listeriosis in Japan and use the knowledge for prevention measures to be taken, the genetic characteristics of the past human clinical isolates needs to be elucidated. For this purpose, multilocus tandem-repeat sequence analysis (MLTSA) and multi-virulence-locus sequence typing (MVLST) were used in this study. The clinical isolates showed a variety of genetically distant genotypes, indicating they were from sporadic cases. However, the MVLST profiles of 7 clinical isolates were identical to those of epidemic clone (EC) I isolates, which have caused several serious outbreaks in other countries, suggesting the possibility that they have strong virulence potential and originated from a single outbreak. Moreover, 6 Japanese food isolates shared their genotypes with ECI isolates, indicating that there may be risks for listeriosis outbreak in Japan. This is the first investigational study on genetic characteristics of Japanese listeriosis isolates. The listeriosis cases happened in the past are presumably sporadic, but it is still possible that some isolates with strong virulence potential have caused listeriosis outbreaks, and future listeriosis risks also exist.

Increasing Incidence of Listeriosis and Infection-associated Clinical Outcomes

“…In addition, several important medical record details, such as infection source of listeriosis, were not available for most patients. However, although human listeriosis is a food-borne disease, it is difficult to determine the food source of infection because of the long incubation time of L. monocytogenes [ 7 ].…”

“…Listeriosis caused by Listeria monocytogenes is a bacterial infection with a high case-fatality rate (CFR) of approximately 20% to 30%; listeriosis occurs mainly in the elderly, neonates, immunocompromised patients, and pregnant women via central nervous system (CNS) infection and bloodstream infection (BSI) [ 1 2 3 4 ]. This gram-positive intracellular bacterium is widespread in the natural environment [ 5 ], and infections mostly arise following the consumption of contaminated food, such as unheated ready-to-eat meals and dairy products [ 6 7 8 ], because of the ability of L. monocytogenes to survive under salty or acidic conditions and grow at refrigeration temperatures [ 9 ].…”

“…An increase in the annual incidence of listeriosis has been reported in many countries recently [ 1 7 10 11 12 ]. Although a number of listeriosis outbreaks have been reported [ 13 ], most cases are sporadic.…”

Characterization of Listeria monocytogenes isolated from human Listeriosis cases in China

“…By serotype, 1/2a and 4b were prevalent in some European countries, representing 46.3% and 42.6% of human isolates from sporadic cases in Italy, 10 23.5% and 52.8% of listeriosis cases in Hungary respectively. 11 Recently, Satoko et al 12 described genetic characteristics of 21 Japanese clinical L. monocytogenes isolates, 13 of which belonged to 4b. The distribution of serotypes was different in this study.…”

Matrix-assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) Can Precisely Discriminate the Lineages of Listeria monocytogenes and Species of Listeria

“…They were screened from river water in Japan and identified by the conventional method using ALOA media (bioMérieux, Lyon, France) and antisera serotyping kit. Species of Listeria were determined by a physiological biochemical test using the Listeria identification system Api (bioMérieux), and 16S rRNA sequencing [ 27 ]. Pathogenicity of L .…”