IncHI1A plasmids potentially facilitate a horizontal flow of antibiotic resistance genes to pathogens in microbial communities of urban residential sewage

Abstract

Horizontal gene transfer via plasmids is important for the dissemination of antibiotic resistance genes among medically relevant pathogens. Specifically, the transfer of IncHI1A plasmids is believed to facilitate the spread of antibiotic resistance genes, such as carbapenemases, within the clinically important family Enterobacteriaceae. The microbial community of urban wastewater treatment plants has been shown to be highly permissive towards conjugal transfer of IncP1 plasmids. Here, we tracked the transfer of the P1 plasmid pB10 and the clinically relevant HI1A plasmid R27 in the microbial communities present in urban residential sewage entering full-scale wastewater treatment plants. We found that both plasmids readily transferred to these communities and that strains in the sewage were able to further disseminate them. Furthermore, that R27 has a broad potential host range, but a low host divergence. Interestingly, although the majority of R27 transfer events were to members of Enterobacteriaceae, we found a subset of transfer to other families, even other phyla. Indicating, that HI1A plasmids facilitate horizontal gene transfer both within Enterobacteriaceae, but also across families of especially Gammaproteobacteria, such as Moraxellaceae, Pseudomonadaceae and Shewanellaceae. pB10 displayed a similar potential host range as R27. In contrast to R27, pB10 had a high host divergence. By cultivative enrichment of the transconjugant communities, we show that sewage strains of Enterobacteriaceae and Aeromonadaceae can stably maintain R27 and pB10, respectively. Our results suggest that dissemination in the urban residual water system of HI1A plasmids may result in an accelerated acquisition of antibiotic resistance genes among pathogens.

Estimating the rate of plasmid transfer with an adapted Luria–Delbrück fluctuation analysis

“…In fact, conjugation can occur across vast phylogenetic distances, such that the expansive gene repertoire in the “accessory” genome encoded on conjugative plasmids is shared among many microbial species (5). This ubiquitous genetic exchange reinforces the central role of conjugation in shaping the ecology and evolution of microbial communities (1, 3, 6). Notably, conjugation is a common mechanism facilitating the spread of antimicrobial resistance genes among bacteria and the emergence of multi-drug resistance in clinical pathogens (7–9).…”

An easily modifiable conjugative plasmid for studying horizontal gene transfer

“…For sample treatment, dilute 5μl of the overnight cultured bacterial solution with 1ml of PBS. The threshold for forward scatter (FSC) was 1200, for side scatter (SSC) was 200, and the gating strategy was consistent with our previous study (Olesen et al, 2022). Data was acquired and analyzed using the BD FACSDiva software v.6.1.3.…”