Comparing transfer of IncHI1A- and IncP1- plasmids in the microbial community of residential sewage. PlasmidsWWTPsTransfer

Horizontal gene transfer (HGT) of plasmids is important for the dissemination of antibiotic resistance genes (ARGs) among medically relevant pathogens. Specifically, the transfer of IncHI1A (HI1A) plasmids is believed to be a contributor to the spread of resistances such as carbapenemases within the clinically important family Enterobacteriaceae. The microbial community of urban wastewater treatment plants (WWTPs) has been shown to be highly permissive towards conjugational transfer of broad host range IncP1 (P1) plasmids. We tracked the transfer of the HI1A plasmid R27 and the P1 plasmid pB10 in microbial communities from urban WWTP influent. We found that both plasmids readily conjugated in this microbial community. Furthermore, strains in the wastewater community (WWC) were able to disseminate both plasmids. We also reveal that R27 has a broad potential host range, but a low host divergence. Although the vast majority of R27 transfer events were distributed within members of the Enterobacteriaceae family, we found a subset of transfers to other families, even other phyla. We speculate these recipients do not stably maintain the plasmid, but may still act as intermediate hosts. Nevertheless, this does indicate that HI1A plasmids facilitate HGT both within Enterobacteriaceae, but also across families. A similar host range as for R27 was found for pB10. In contrast to R27, pB10 had a high host divergence. By cultivation we show that strains of Enterobacteriaceae or Aeromonadaceae of the WWC are stably maintaining R27 and pB10, respectively. Our results suggest that dissemination in the urban waste water system of HI1A plasmids may result in an accelerated acquisition of ARGs in critical pathogens.