Antibiotic resistance genes in phage particles isolated from human feces and induced from clinical bacterial isolates

Abstract

Phage particles have emerged as elements with the potential to mobilize antibiotic resistance genes (ARGs) in different environments, including the intestinal habitat. The aim of this study was to determine the occurrence of ARGs in phage particles present in fecal matter and induced from strains isolated from feces. Nine ARGs (blaTEM, blaCTX-M-1-group, blaCTX-M-9-group, blaOXA-48, qnrA, qnrS, mecA, sul1 and armA) were quantified by qPCR in the phage DNA fractions of 150 fecal samples obtained from healthy individuals. These subjects had not received antibiotic treatment or travelled abroad in the three months prior to the sample collection. On the suspicion that the detected particles originated from bacterial flora, 82 Escherichia coli and Klebsiella pneumoniae isolates possessing at least one identified ARG (blaTEM, blaCTX-M-1-group, blaCTX-M-9-group, armA, qnrA, qnrS, and sul1) were isolated and their capacity to produce phage particles carrying these ARGs after induction was evaluated. Seventy-two percent of samples were positive for at least one ARG, with blaTEM and blaCTX-M-9-group being the most prevalent and abundant. Fifty-one isolates (62%) showed an increase in the number of copies of the respective ARG in the phage fraction after induction, with blaTEM, blaCTX-M-1-group, blaCTX-M-9-group and sul1 being the most abundant. Phages induced from the isolates were further purified and visualized using microscopy and their DNA showed ARG levels of up to 10(10) gene copies/ml. This study highlights the abundance of phage particles harboring ARGs and indicates that bacterial strains in the intestinal habitat could be sources of these particles.