Molluscs-A ticking microbial bomb

Abstract

Bivalve shellfish consumption (ark shells, clams, cockles, and oysters) has increased over the last decades. Following this trend, infectious disease outbreaks associated with their consumption have been reported more frequently. Molluscs are a diverse group of organisms found wild and farmed. They are common on our tables, but unfortunately, despite their great taste, they can also pose a threat as a potential vector for numerous species of pathogenic microorganisms. Clams, in particular, might be filled with pathogens because of their filter-feeding diet. This specific way of feeding favors the accumulation of excessive amounts of pathogenic microorganisms like Vibrio spp., including Vibrio cholerae and V. parahaemolyticus, Pseudomonas aeruginosa, Escherichia coli, Arcobacter spp., and fecal coliforms, and intestinal enterococci. The problems of pathogen dissemination and disease outbreaks caused by exogenous bacteria in many geographical regions quickly became an unwanted effect of globalized food supply chains, global climate change, and natural pathogen transmission dynamics. Moreover, some pathogens like Shewanella spp., with high zoonotic potential, are spreading worldwide along with food transport. These bacteria, contained in food, are also responsible for the potential transmission of antibiotic-resistance genes to species belonging to the human microbiota. Finally, they end up in wastewater, thus colonizing new areas, which enables them to introduce new antibiotic-resistance genes (ARG) into the environment and extend the existing spectrum of ARGs already present in local biomes. Foodborne pathogens require modern methods of detection. Similarly, detecting ARGs is necessary to prevent resistance dissemination in new environments, thus preventing future outbreaks, which could threaten associated consumers and workers in the food processing industry.

Keywords: antibiotic-resistance; aquaculture; bacteria; bivalves; foodborne diseases; genes; molluscs; zoonoses.

FIGURE 1

Circulating Mobile Genetic Elements (MGE) may increase Antibiotic Resistant (AR) marine bacterial species in the marine environment. Bacteria in the marine environment may spread resistance genes to other species, especially when antibiotics appear (like in fish aquacultures and bivalves’ larval hatcheries). The spread of MGE generates new strains of bacteria capable of successfully breaking out and becoming resistant to popular antibiotics. Antibiotics are delivered to water also with feces from coastlines, which are usually densely populated. The figure is prepared based on literature (Krieger et al., 1981; Kueh and Chan, 1985; Moy and Walday, 1996; Islam and Tanaka, 2004; Li et al., 2012; Weis, 2014; Hsu and Lee, 2015; Beaudry et al., 2016; Zannella et al., 2017; Chiesa et al., 2018; Kolm et al., 2018; Lopez-Joven et al., 2018; MacFadden et al., 2018; Bondarczuk and Piotrowska-Seget, 2019; Fresia et al., 2019; Hoegh-Guldberg et al., 2019; Pinsky et al., 2019; Chen et al., 2020; Grabowska et al., 2020; Martinez-Albores et al., 2020; Musella et al., 2020; Preena et al., 2020; Verga et al., 2020; Albano et al., 2021; Mudadu et al., 2021; Pepi and Focardi, 2021; Bagi and Skogerbø, 2022; Baker et al., 2022; Kamermans et al., 2022).