Antibiotic resistance levels in soils from urban and rural land-uses in Great Britain

Although the soil is one of the largest microbial diversity reservoirs, the processes that define its microbial community dynamics are not fully understood. Improving our understanding of the levels of antibiotic resistance in soils with different land-uses in Great Britain is not only important for the protection of animal health (including humans) but also for gaining an insight into gene transfer levels in microbial communities. This study looked at the levels of antibiotic resistant bacteria (ARB) able to survive inhibitory concentrations of chloramphenicol, erythromycin and vancomycin, as well as subinhibitory (10 μg/ml) erythromycin concentrations. Soils from nine different sites across Great Britain belonging to three distinct land-uses (agricultural, urban and semi-natural) were sampled and the percentage of ARB was calculated for each site. Statistical analyses confirmed a significant difference in the level of ARB found in agricultural land compared to urban or semi-natural sites. The results also showed that resistance levels to vancomycin and chloramphenicol in the agricultural and urban sites sampled were significantly higher than those for erythromycin, whilst in semi-natural sites all three antibiotics show similar resistance levels. Finally, although the levels of resistance to a subinhibitory (10 μg/ml) erythromycin concentration, were significantly higher across land-use types when compared to the levels of resistance to an inhibitory (20 μg/ml) concentration, these were much less marked in agricultural land respect to urban or semi-natural land-uses.