Abstract
The vast majority of antibiotic resistant genes (ARG) acquired by human pathogens have originated from the natural environment. Therefore, understanding factors that influence intrinsic levels of ARG in the environment could be epidemiologically significant. The selection for metal resistance often promotes AR in exposed organisms; however, the relationship between metal levels in nature and the intrinsic presence of ARG has not been fully assessed. Here, we quantified, using qPCR, the abundance of eleven ARG and compared their levels with geochemical conditions in randomly selected soils from a Scottish archive. Many ARG positively correlated with soil copper levels, with approximately half being highly significant (p<0.05); whereas chromium, nickel, lead, and iron also significantly correlated with specific ARG. Results show that geochemical metal conditions innately influence the potential for AR in soil. We suggest soil geochemical data might be used to estimate baseline gene presence on local, regional and global scales within epidemiological risk studies related to AR transmission from the environment.
Highlights
There is a growing concern about antibiotic resistance in natural and clinical settings
Relationships between geochemical conditions, microorganisms and human health have been long documented in terms of altered mobility and toxicity of metals [7], but the influence of background geochemical conditions on intrinsic antibiotic resistant genes (ARG) abundance has not been considered relative to AR proliferation
A bivariate correlation analysis (Table 2; other correlations can be found in Supplemental Table S4) showed that eight of the eleven quantified ARG positively correlated with soil copper levels; five ARG being highly significant (p,0.05), including tet(M), tet(W), blaOXA, erm(B) and erm(F)
Summary
There is a growing concern about antibiotic resistance in natural and clinical settings. The practical question is whether elevated metal levels in soils increase the prevalence of antibiotic genes in the environment.
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