Abstract
Freshwater mussels are among the most endangered groups of fauna anywhere in world. The indiscriminate use of antibiotics has led to the emergence of resistant strains. These antibiotic-resistant bacteria play a key role in increasing the risk allied with the use of surface water and in spread of resistance genes. Two endangered freshwater mussel species, Margaritifera margaritifera and Potomida littoralis, were sampled at 4 sampling sites along a 50km stretch of River Tua. Water samples were taken at same sites. Of the total of 135 isolates, 64.44% (39.26% from water and 25.19% from mussels) were coliform bacteria. Site T1, with the lowest concentration of coliform bacteria, and site T2 were the only ones where M. margaritifera was found. No E. coli isolates were found in this species and the pattern between water and mussels was similar. P. littoralis, which was present at T3/T4 sites, is the one that faces the highest concentration of bacterial toxins, which are found in treated wastewater effluents and around population centers. Sites T3/T4 have the isolates (water and mussels) with the highest resistance pattern, mainly to β-lactams. Water and P. littoralis isolates (T3/T4) showed resistance to penicillins and their combination with clavulanic acid, and to cephalosporins, precisely to a fourth generation of cephalosporin antibiotics. We discuss the conservation status and risk to water systems and the need for research into possible management measures. It is suggested that future studies on the health status of freshwater bivalves should incorporate measures to indicate bacteriological water quality.
Highlights
Freshwater bivalves (FB) are ubiquitous organisms in freshwater ecosystems
We explore whether site and mussel species are factors influencing the incidence of multidrug resistant (MDR) bacteria, and what potential risk they represent to freshwater ecosystems
The sample included a total of 5 M. margaritifera. 2 specimens were from site T1 and 3 from T2
Summary
Freshwater bivalves (FB) are ubiquitous organisms in freshwater ecosystems. They are affected by various threats across the world, such as pollution (Goodchild et al, 2015), overexploitation of natural re sources (Nobles and Zhang, 2011), competition by invasive alien species (Bodis et al, 2014; Pilotto et al, 2016; Sousa et al, 2019), loss of host fishes (Benaissa et al, 2019), habitat modifications and fragmentation (Sousa et al, 2020), and more recently by climate change (Atkinson and Vaughn, 2014; Santos et al, 2015; Strayer and Dudgeon, 2010). Fresh water mussels have a complex life cycle and are highly sensitive to anthropogenic pressures They have been suffering global extinction and loss of biodiversity for decades and are among the most threatened animal groups on the planet (Downing et al, 2010). They are long-lived (some species can live for up to 100 years) and are responsible for important functions and vital ecosystem services (Vaughn and Haken kamp, 2001). They are sensitive to environmental changes, making them excellent bioindicators (Grabarkiewicz and Davis, 2008). As benthic filter-feeders, freshwater mussels (the Unionida order) are constantly exposed to pollution and accumulated pollutants, seques tering heavy metals associated with suspended particles and deposited in bottom sediments (Naimo, 1995; Parra et al, 2021; Ribeiro Guevara et al, 2004) and even taking up pharmaceuticals, contaminants of emerging concern, and bacteria such as Escherichia coli
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