The emergence and increased prevalence of antibiotic resistance genes (ARGs) in the environment may pose a serious global health concern. This study evaluates the abundance of several ARGs in bacterial and bacteriophage DNA via real-time qPCR in samples from five different sampling points in Tunisia; three wastewater treatment plants (WWTP 1, 2 and 3) and wastewater from two abattoirs slaughtering different animals. Results are compared with those obtained in the Barcelona area, in northeast Spain. Eight ARGs were quantified by qPCR from total and phage DNA fraction from the samples. Three β-lactamases (bla(TEM), bla(CTX-M) cluster 1 and bla(CTX-M) cluster 9), two quinolone resistance genes (qnrA and qnrS), the mecA gene that confers resistance to methicillin in Staphylococcus aureus, the emerging armA gene, conferring resistance to aminoglycosides and sul1, the most extended gene conferring resistance to sulfonamides, were evaluated. Sul1 and bla(TEM) were the most prevalent ARGs detected at all five Tunisian sampling points, similarly with the observations in Barcelona. bla(CTX-M-9) was more prevalent than bla(CTX-M-1) both in bacterial and DNA within phage particles in all samples analysed. mecA and armA were almost absent in Tunisian waters from human or animal origin in contrast with Barcelona that showed a medium prevalence. qnrA was more prevalent than qnrS in bacterial and phage DNA from all sampling points. In conclusion, our study shows that ARGs are found in the bacterial and is reflected in the phage DNA fraction of human and animal wastewaters. The densities of each ARGs vary depending on the ARGs shed by each population and is determined by the characteristics of each area. Thus, the evaluation of ARGs in wastewaters seems to be suitable as marker reflecting the antibiotic resistance patterns of a population.

The reuse of treated wastewaters can be a solution to meet the needs of water in the geographical area of study. Bacteriophages seem to predict differently the presence of faecal contamination in water than bacterial indicators. Consequently, they can be a valuable additional tool to improve water resources management for minimizing health risks.

No clear correlation between studied enteric viruses and coliphages concentration was proved. Coliphages abundance in collected samples should raise concerns about human enteric viruses transmission as these residues are reused in agricultural fields.

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