Antibiotic resistance of bacteria isolated from Pagellus erythrinus microplastics and public health

Microplastics (MPs) are widespread in the aquatic environmental due to anthropogenic pollution and are ingested indifferently by fishes that confuse them with food. In aquatic environment, mechanical stress, UV radiations, chemical and biological actions cause a constant degradation and breakdown of plastic objects into smaller fragments. Mediterranean Sea is characterized by the highest densities of plastics in the world being a closed basin with a complex hydrodynamics. The aim of this work is to evidence the occurrence of microbial adhesions on MPs found in edible Pagellus erythrinus (Linnaeus, 1758) bought in local Sicilian supermarkets and therefore highlight the potential role of microplastics in conveying antibiotic resistance by ingestion of food by humans. The composition and structural-morphological properties of MPs found in the excised gastrointestinal tract (GIT) and gills are identified using different techniques. In particular, microparticles of different nature (plastics, organic components, cellulose-based materials) have been determined following specific Raman signals on a large spectral range (300-3500 cm-1). The Pagellus was dissected, open longitudinally, within a sterile glass Petri dish. The components deemed exogenous to the normal structure of the gills and GIT were collected. Optical microscopy images showed that both the GIT and the gill of Pagellus erythrinus contain MPs of different colors (black, dark blu) and mainly with a fibrous shape. At the moment, microbial assays show the adhesion of Citrobacter and E. coli in some fibers extracted by gills while Vibrio spp was mainly detected in the fibers present in GIT. Bacterial isolates were screened for susceptibility to antibiotics using the Kirby-Bauer test, choosing the molecules most used in human therapy. The results obtained suggest that plastics may contribute to the spread of multiple antibiotic resistance in marine environments underline the relevance of future studies on this topic. Key messages Plastics can serve as vectors for the spread of multiple resistances to antibiotics across marine environments. Further studies on possible vehicles of multidrug-resistant germs carried by food of various kinds are desirable.