title: The occurrence of antibiotic resistance genes in a Mediterranean river and their persistence in the riverbed sediment.
abstract: The spread of antibiotic resistance genes (ARGs) in the environment is a serious concern. Bacterial ARGs can spread via different mobile genetic elements as phage particles, which thereby emerge as novel vectors for environmental dissemination. To assess how climate events, such as heavy rains or water scarcity, could affect the spread of ARGs, it is necessary to know their prevalence and abundance in aquatic environments as well as the potential reservoirs from which they could become mobile. This study evaluates the occurrence of ARGs in the water and sediment of a Mediterranean river. Six clinically relevant ARGs (blaTEM, blaCTX-M, qnrA, qnrS, mecA and sul1) were quantified by qPCR in the bacterial and phage fractions of 69 water and 70 sediment samples from the River Llobregat (NE Spain), collected during both dry and rainy periods. blaTEMand sul1 were the most prevalent and abundant ARGs; the others were more variable. Significant seasonal differences in ARG prevalences and abundances were observed. Since ARGs were detected in the sediment, the persistence of the most abundant ARGs naturally occurring in that sediment (blaTEMand sul1) was evaluated under three conditions. No ARG inactivation occurred in fresh sediment over 14 days; while the ARGs declined by less than 2 log10units over 35 days in semi-dry and dry sediment. The occurrence of ARGs in water and sediment is influenced by seasonal conditions and they can be mobilized by bacteria and phage particles. In sediment, ARGs persist for long periods and hence sediment can be a natural reservoir of ARGs, from where they can spread and cause the emergence of new resistant strains.
authors.affiliation: Department of Genetics, Microbiology and Statistics, University of Barcelona, Diagonal 643, Annex, Floor 0, E-08028 Barcelona, Spain.
authors.forename: William
authors.initials: W
authors.lastname: Calero-Cáceres
authors.affiliation: Department of Genetics, Microbiology and Statistics, University of Barcelona, Diagonal 643, Annex, Floor 0, E-08028 Barcelona, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Méndez
authors.affiliation: Department of Genetics, Microbiology and Statistics, University of Barcelona, Diagonal 643, Annex, Floor 0, E-08028 Barcelona, Spain.
authors.forename: Julia
authors.initials: J
authors.lastname: Martín-Díaz
authors.affiliation: Department of Genetics, Microbiology and Statistics, University of Barcelona, Diagonal 643, Annex, Floor 0, E-08028 Barcelona, Spain. Electronic address: mmuniesa@ub.edu.
authors.forename: Maite
authors.initials: M
authors.lastname: Muniesa
mesh_terms: D001435:Bacteriophages / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics*; D005814:Genes, Viral / Q000235:genetics*; D005822:Genetic Vectors / Q000235:genetics; D019015:Geologic Sediments / Q000382:microbiology* / Q000821:virology*; D045483:Rivers / Q000382:microbiology* / Q000821:virology*; D012621:Seasons; D013030:Spain
keywords: Antibiotic resistance; Bacteriophages; Persistence; River; Sediment