Bacteriophages as a reservoir of extended-spectrum β-lactamase and fluoroquinolone resistance genes in the environment

Six antibiotic resistance genes (bla(CTX-M), bla(SHV), bla(TEM), qnrA, qnrB and qnrS) were quantified by qPCR in both phage and bacterial DNA fractions of environmental water samples in order to determine the contribution of phages to the dissemination of antibiotic resistance genes (ARGs) in the environment. Although the highest copy numbers (p < 0.05) of ARGs were detected in the bacterial DNA fraction, qnrS and bla(SHV) genes were found in the phage DNA from all samples analysed, reaching up to 4 log10 copy numbers/mL in hospital samples. These results indicate that bacteriophages are a potential reservoir of resistance genes and may act as efficient vehicles for horizontal gene transfer.