Listeriosis: genotyping as a key for identification a possible source of infection

Objective.

To perform a comparative analysis of clinical and food isolates of Listeria monocytogenes collected in the European part of Russia in 2018–2019.

Materials and Methods.

We used multilocus sequencing (MLST), supplemented by virulence loci, including fragments of internalin genes (MvLST, Multi-virulent-locus sequence typing), followed by phylogenetic analysis.

Results.

The main diagnoses for clinical isolates were prenatal and neonatal listeriosis and meningitis. Clinical isolates predominantly belonged to phylogenetic line II with the predominance of ST7, which was also the most abundant in food isolates. The second most common occurrence in food isolates was ST121, widely distributed in Europe. Isolates of phylogenetic line I in the group of clinical cultures in three cases were represented by ST6, detected during outbreaks of listeriosis in Europe 2015–2018 and South Africa in 2017–2018. Only in one isolate from food belonged to the phylogenetic lineage I. In general, the diversity of food isolate genotypes was significantly higher than clinical isolates. The analysis of virulence loci revealed a new internalin A allele and a new internalin genes profile (IP) in isolate ST7 from food.

Conclusions.

L. monocytogenes of the most common ST7 is autochthonous in Russia; cases of listeriosis caused by the ST6 bacterium are most likely imported. Based on the analysis of the diversity of ST and IP of L. monocytogenes identified in Russia, a rapid diagnosis scheme for epidemiological investigation is proposed.