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

Abstract

Listeria monocytogenes is an ubiquitous pathogen isolated from different host species including fish, crustaceans, and molluscs, but it is rarely a pathogenic microorganism to marine reptiles. In particular, only two cases of fatal disseminated listeriosis have been described in the loggerhead sea turtle (Caretta caretta). In this study, we describe a lethal case of L. monocytogenes infection in a loggerhead sea turtle. The turtle was found alive, stranded on a beach in North-eastern Italy, but perished soon after being rescued. The autoptic examination revealed that heart, lung, liver, spleen, and urinary bladder were disseminated with multiple, firm, 0.1–0.5 mm sized, nodular, white-green lesions. Microscopically, these lesions corresponded with heterophilic granulomas with Gram+ bacteria within the necrotic center. Furthermore, the Ziehl–Neelsen stain was negative for acid-fast organisms. Colonies isolated from heart and liver were tested through MALDI-TOF for species identification, revealing the presence of L. monocytogenes. Whole Genome Sequencing on L. monocytogenes isolates was performed and the subsequent in silico genotyping revealed the belonging to Sequence Type 6 (ST 6); the virulence profile was evaluated, showing the presence of pathogenicity islands commonly observed in ST 6. Our results further confirm that L. monocytogenes should be posed in differential diagnosis in case of nodular lesions of loggerhead sea turtles; thus, given the zoonotic potential of the microorganism, animals should be treated with particular caution. In addition, wildlife animals can play an active role as carriers of possibly pathogenetic and virulent strains and contribute to the distribution of L. monocytogenes in the environment.

The Isolation, Genetic Analysis and Biofilm Characteristics of Listeria spp. from the Marine Environment in China

“…Recreational water activities in coastal areas contaminated with fecal matter have been associated with gastrointestinal disease (>120 million cases) and respiratory disease (>50 million cases) worldwide each year [ 35 , 36 ]. A loggerhead sea turtle stranded on a beach on northern Italy’s coastline was infected with ST6 L. monocytogenes , leading to multiple internal lesions and a fatal infection [ 37 ]. Exposure to beach sand and recreational seawater contaminated with L. monocytogenes poses a potential threat to human and animal health.…”

Genomic Characterization of Listeria monocytogenes and Other Listeria Species Isolated from Sea Turtles

“…More attention has been paid to marine ecosystems as the detection of strains of Lm has been reported in marine animals [20][21][22][23], which highlighted the importance of further studies of these microorganisms in relation to the environment. From a One Health perspective, it is important to consider the role of wild animals and the environment as reservoirs of bacteria and sources of infection, as the environment, animals, and humans are closely linked and interconnected [24].…”