Characterization of Listeria monocytogenes isolated from wildlife in central New York

Abstract

Background Listeria monocytogenes (Lm) present in farming soil and food‐processing facilities threatens food safety, but little is known about the carriage of Lm by wildlife. Objectives We estimated the prevalence of faecal Lm shedding among wildlife admitted to a veterinary medical teaching hospital in central New York and characterized a subset of the Lm isolates. Methods Wildlife samples were collected between May 2018 and December 2019. We characterized the Lm isolates by assessing the growth at three temperatures approximating the body temperatures of reptiles (25°C), mammals (37°C), and birds (42°C) and identifying genotypic characteristics related to transmission and virulence. Results The apparent prevalence of faecal Lm shedding was 5.6% [18/324; 95% confidence interval (CI), 3.3%–8.6%]. Among 13 isolates that represented two lineages and 11 clonal complexes, three and five isolates were grouped into the same SNP clusters with human clinical isolates and environmental isolates, respectively. However, specific SNP difference data showed that Lm from wildlife was generally not closely related (>22 SNP differences) to Lm from human clinical sources and the food‐processing environment. While the stress response locus SSI‐2 was absent, SSI‐1 was found in four isolates. Virulence genes prfA, plcA, hly, mpl, actA, plcB, inlA, inlB, inlC, inlE, inlH, inlJ, and inlK were present, without any premature stop codons, in all isolates. Virulence loci Listeria pathogenicity island 3 (LIPI‐3) and LIPI‐4, which have been linked to hypervirulence, and inlG were found in four, three, and seven isolates, respectively. Conclusions Wildlife represents a potential reservoir for genetically diverse and putatively hypervirulent Lm strains. No statistically significant association between growth parameters and hosts was observed. However, compared to lineage I isolates, lineage II isolates showed significantly (p < 0.05) faster growth at 25°C and significantly slower growth at 42°C, suggesting that wildlife Lm isolates that belong to lineages I and II differ in their ability to grow at 25°C and 42°C.

Loggerhead Sea Turtle as Possible Source of Transmission for Zoonotic Listeriosis in the Marine Environment

“…The presence of an ST6 isolate carrying virulence genes involved in invasion and adherence mechanisms could be relevant in wildlife animals. In fact, they could play an active role as carriers of possibly pathogenetic and virulent strains, and contribute to the distribution of L. monocytogenes in the environment [ 38 , 39 ]. This is even more true when considering species such as Caretta caretta , which can migrate for hundreds or thousands of kilometers [ 6 , 40 ].…”

In Vitro and In Vivo Virulence Study of Listeria monocytogenes Isolated from the Andalusian Outbreak in 2019

“…To induce an infection, L. monocytogenes expresses virulence genes organized into groups such as the Internalin gene operon (encoded by inlA to inlK ), listerial pathogenicity islands (encoded by LIPI -1to LIPI-4 ) and stress survival islets (SSIs) [ 4 ]. Accordingly, two recent studies showed that strains belonging to CC388 harbor LIPI-4, but not inLF, inlG, SSI-1 and SSI-2 [ 25 , 26 ]. This pathogenic island is also present in isolates belonging to CC4 that cause cerebral and placental tissue tropism [ 17 , 20 ].…”

Pathogenic Bacteria in Free-Living Birds, and Its Public Health Significance

“…Additionally, L. monocytogenes needs the actA gene, which encodes a protein involved in actin polymerization and motility, to move intracellularly and spread from one cell to another [ 149 ]. In a study performed by Chen [ 150 ] in the USA, the common prevalence of inlA , inlB , and actA genes was noted among L. monocytogenes strains isolated from wild birds; moreover, these strains were identified as putatively hypervirulent L. monocytogenes strains.…”