Listeria monocytogenesfaecal carriage is common and driven by microbiota

Abstract

Listeria genus comprises two opportunistic pathogenic species, L. monocytogenes (Lm) and L. ivanovii, and several non-pathogenic species. All can thrive as saprophytes, whereas only pathogenic species cause systemic infections in human and cattle. Identifying Listeria species’ respective biotopes is critical to understand the ecological contribution of Listeria pathogenic potential. Here, we aimed at detecting Listeria in samples of diverse origins, to highlight ecological differences between pathogenic and non-pathogenic species. We retrieved 16S rDNA datasets from the metagenomics MG-RAST database and determined the prevalence and abundance of Listeria species in various sources. Overall, Listeria was detected in 14% of datasets. Lm was the most prevalent species, most abundant both in soil and host-associated environments, including in 5% of human stools. Lm was also detected in 10% of human stool samples from an independent cohort of 900 healthy asymptomatic donors. A specific microbiota signature was associated with Lm faecal carriage in human, as well as in experimentally inoculated mice, in which it preceded Lm long-term gut colonization, indicating that gut microbiota composition influences Lm faecal carriage. These results suggest that asymptomatic faecal carriage, rather than disease, exerts purifying selection on Lm “virulence genes”.

Ruminant-associated Listeria monocytogenes isolates belong preferentially to dairy-related hypervirulent clones: a longitudinal study in 19 farms

“…monocytogenes was detected more frequently in cattle farms than in smallruminant farms, which is coherent with previous studies regarding the epidemiology of listeriosis among cattle and small ruminants (8,11,34,40). Interestingly, the pathogenic species L. ivanovii, reported in small ruminants in previous studies (40)(41)(42) was not detected in any of our farms, which could be due to its relative low prevalence (42,43) or to possible biases of isolation protocols that have typically been optimized for recovery of L. monocytogenes (42). Our results are in line with reports showing that the incidence of L. innocua in ruminants feces is higher (9.7-22.7%) than that of L. monocytogenes (1.8-9.3%) (17,44).…”

“…The majority of isolates retrieved here belonged to lineage I (particularly to SL1/CC1, SL219/CC4 and SL87/CC87) which is significantly associated with a clinical origin both in humans and animals (29,49,50). CC1 has been shown to be highly associated with dairy products (30, 51) and cause human listeriosis outbreaks (52,53).…”

Listeria monocytogenes gene essentiality under laboratory conditions and during macrophage infection

“…Due to the ubiquitous presence of L. monocytogenes in the environment, food contaminations and thus periods of asymptomatic carriage in the gut are quite common. Approximately 5-10% of the population are considered to carry L. monocytogenes in the gastrointestinal tract and it is estimated that healthy adults experience two periods of asymptomatic L. monocytogenes carriage per year (2,3). L. monocytogenes that crosses the epithelial barrier is rapidly cleared from the blood stream by macrophages and non-professional phagocytes in the liver and the spleen, which represent an important line of defence against the infection (4)(5)(6).…”