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Bacteriophages are ubiquitously distributed prokaryotic viruses that are more abundant than bacteria. As a consequence of their life cycle, phages can kidnap part of their host's genetic material, including antibiotic resistance genes (ARGs), which released phage particles transfer in a process called transduction. The spread of ARGs among pathogenic bacteria currently constitutes a serious global health problem. In this study, fresh vegetables (lettuce, spinach and cucumber), and cropland soil were screened by qPCR for ten ARGs (blaTEM, blaCTX-M-1 group, blaCTX-M-9 group, blaOXA-48, blaVIM, mecA, sul1, qnrA, qnrS and armA) in their viral DNA fraction. The presence of ARGs in the phage DNA was analyzed before and after propagation experiments in an Escherichia coli host strain to evaluate the ability of the phage particles to infect a host. ARGs were found in the phage DNA fraction of all matrices, although with heterogeneous values. ARG prevalence was significantly higher in lettuce and soil, and the most common overall were β-lactamases. After propagation experiments, an increase in ARG densities in phage particles was observed in samples of all four matrices, confirming that part of the isolated phage particles were infectious. This study reveals the abundance of free, replicative ARG-containing phage particles in vegetable matrices and cropland soil. The particles are proposed as vehicles for resistance transfer in these environments, where they can persist for a long time, with the possibility of generating new resistant bacterial strains. Ingestion of these mobile genetic elements may also favor the emergence of new resistances, a risk not previously considered. Keywords: Bacteriophages, Antibiotic resistance genes, Cropland, Lettuce, Cucumber, Spinach

Phage particles have emerged as elements with the potential to mobilise antibiotic resistance genes (ARGs) in different environments, including the intestinal habitat. This study aimed to determine the occurrence of ARGs in phage particles present in faecal matter and induced from strains isolated from faeces. Nine ARGs (bla(TEM), bla(CTX-M-1 group), bla(CTX-M-9 group), bla(OXA-48), qnrA, qnrS, mecA, sul1 and armA) were quantified by qPCR in the phage DNA fractions of 150 faecal samples obtained from healthy individuals who had not received antibiotic treatment or travelled abroad in the 3 months prior to 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 (bla(TEM), bla(CTX-M-1 group), bla(CTX-M-9 group), armA, qnrA, qnrS and sul1) were isolated and their capacity to produce phage particles carrying these ARGs following induction was evaluated. Of 150 samples, 72.7% were positive for at least one ARG, with bla(TEM) and bla(CTX-M-9 group) being the most prevalent and abundant. Of the 82 isolates, 51 (62%) showed an increase in the number of copies of the respective ARG in the phage fraction following induction, with bla(TEM), bla(CTX-M-1 group), bla(CTX-M-9 group) and sul1 being the most abundant. Phages induced from the isolates were further purified and visualised using microscopy and their DNA showed ARG levels of up to 1010 gene copies/mL. This study highlights the abundance of phage particles harbouring ARGs and indicates that bacterial strains in the intestinal habitat could be source of these particles. (C) 2017 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.

Antibiotic resistance in bacteria is increasing continually, and it severely undermines the ability to control infectious diseases. This fact and new requirements for food quality and safety, especially fresh products, have enhanced the search of novel methods. As alternatives, phages have been proposed to control bacteria, either pathogens in clinical settings and food or spoilage bacteria in food processes. The advantage of their use is that phages target specific bacterial strains. In the last stages of the phage infectious cycle, phages express cell wall–hydrolyzing enzymes that cause lysis and death of the bacteria. These enzymes, called lysins, also are included as alternative antimicrobial molecules. Application of phages to control the bacterial growth shows promising results. Limitations, opportunities, and progresses in the use of phages and phage proteins as antimicrobials are discussed in this chapter.