Genetic diversity of Listeria monocytogenes strains in ruminant abortion and rhombencephalitis cases in comparison with the natural environment

Abstract

BackgroundListeria monocytogenes is the causative agent of listeriosis, a serious disease affecting both animals and humans. Here, multilocus sequence typing (MLST) was used to characterize the genetic diversity of Listeria monocytogenes strains isolated from the natural environment and animal clinical cases in Europe. The prevalence of clonal complexes (CCs) obtained was compared according to (i) the origin of isolation – clinical cases vs. natural environment – and (ii) the clinical form of animal listeriosis – rhombencephalitis vs. abortion. To this aim, two datasets were constructed. The clinical dataset consisted of 350 animal clinical isolates originating from France and Slovenia and supplemented with isolates from Switzerland and Great Britain. The natural environment dataset consisted of 253 isolates from the natural environment originating from Slovenia and supplemented with isolates from nine other European countries.ResultsFor the clinical cases, CC1, CC4-CC217 and CC412 were the most prevalent in rhombencephalitis and CC1, CC37 and CC4-CC217 in abortion. The hypervirulent CC1 and CC4-CC217 prevailed in both datasets. These results indicated that livestock is constantly exposed to hypervirulent CCs. CC1 was significantly associated with a clinical origin, whereas CC9, CC29 and CC14 were associated with the natural environment. CC1 was predominant among rhombencephalitis cases both in cattle and small ruminants, and its prevalence did not differ significantly between these two groups. A novel association of CC37 and CC6 with abortion cases was revealed.ConclusionsHere, we show that CC1 and CC4-CC217 are prevalent in isolates of environmental and animal clinical origin, suggesting that ruminants are frequently exposed to hypervirulent CCs. The presence of CC4 in two mastitis cases calls for further attention due to direct threat to the consumer. We showed several associations between CCs and the origin of isolation or clinical form of listeriosis, e.g. CC37 and CC6 with abortion. This study improves our understanding of the population structure of L. monocytogenes isolates from the natural environment and animal clinical cases. Moreover, it provides a basis for future studies aiming to determine the underlying mechanisms of phenotypic traits of interest.

Environmental dissemination of pathogenic Listeria monocytogenes in flowing surface waters in Switzerland

“…Two further strains (8%) were assigned to CC6, which is an emerging epidemic L. monocytogenes serotype 4b clone causing major outbreaks and severe forms of human listerial meningitis worldwide 6 , 24 . Other CCs identified among the strains in this study included L. monocytogenes serotype 1/2a CC7, CC11 and CC29, all of which have been associated with outbreaks occurring in the US between 1987 and 2011, and further found to represent environmental strains that persist within food production and livestock environments globally 23 , 25 – 27 . On the other hand, L. monocytogenes serotype 1/2a CC37 found in two samples in this study, is associated with abortion in small ruminants and cattle and found frequently in wildlife and ruminant environments 13 , 25 , 28 .…”

“…Other CCs identified among the strains in this study included L. monocytogenes serotype 1/2a CC7, CC11 and CC29, all of which have been associated with outbreaks occurring in the US between 1987 and 2011, and further found to represent environmental strains that persist within food production and livestock environments globally 23 , 25 – 27 . On the other hand, L. monocytogenes serotype 1/2a CC37 found in two samples in this study, is associated with abortion in small ruminants and cattle and found frequently in wildlife and ruminant environments 13 , 25 , 28 . Further, L. monocytogenes CC37 is prominent in milk samples from US dairy farms 29 .…”

In-Depth Longitudinal Study of Listeria monocytogenes ST9 Isolates from the Meat Processing Industry: Resolving Diversity and Transmission Patterns Using Whole-Genome Sequencing

“…While L. monocytogenes is frequently found in animals, on farms, and in the natural environment, the frequency of the different genetic groups of L. monocytogenes appears to differ significantly in these environments compared to that observed in meat products and the meat processing industry. L. monocytogenes ST9 is rarely found in pig or ruminant farming environments, animals, or wild natural surroundings ( 22 , 58 – 60 ). This sequence type has, however, frequently been found to dominate in raw pork meat ( 21 , 52 , 61 ) and is also commonly found to persist in slaughterhouses ( 14 , 15 , 24 , 62 ) as well as in downstream compartments in the meat processing chain ( 10 , 22 , 26 ).…”

First Report on the Finding of Listeria mnocytogenes ST121 Strain in a Dolphin Brain

“…Although increasing reports are available on the prevalence of Lm in diverse wild species [ 9 , 16 , 29 , 35 , 36 ], it is rare to isolate Lm strains from a dolphin. In England, systematic surveillance programs were conducted on 728 cetaceans of 16 different species tested for 12 consecutive years and no Lm strain was ever detected [ 37 ].…”

“…CC121 strains pose a serious challenge to the food industry, as they are overrepresented in all food sectors [ 18 , 19 ], and can persist in different food processing plants for years [ 20 , 21 , 22 , 23 , 24 , 25 ]. Remarkably, in farming animals, CC121 strains are either never observed [ 26 , 27 , 28 , 29 ] or observed with a low prevalence [ 16 , 30 ]. Regarding wild mammals, only one study has reported the occurrence of CC121 strains among hedgehogs, in the UK [ 4 ].…”