Multidrug-Resistant Bacteria in the Environment, Their Resistance and Transfer Mechanisms

Dear Colleagues,

Antibiotic-resistant bacteria (ARB) were found in the environment long before antibiotics were used by humans, e.g., antibiotics producers protecting themselves against their own antibiotics. Thus, one must clearly differentiate between this intrinsic environmental resistome and the acquired transferable resistome whose increasing abundance is a big concern as it can largely affect the health of humans and animals. Following the One Health approach, it is of primordial importance to monitor and control the release of selecting and co-selecting pollutants (antibiotics, heavy metals, and disinfectants), ARB, and their antibiotic resistance genes (ARGs) from hospitals, nursing homes, animal clinics, and industrial livestock farming into the environment via the release of wastewater (treated, partially treated, non-treated) into surface waters and soils.

In addition, organic wastewater solids (biosolids) are not only valuable organic fertilizers having numerous beneficial effects on soil characteristics—they are also recognized as one of the main anthropogenic sources of chemical pollutants, ARGs, and mobile genetic elements (MGEs) in agricultural soil. Thus, biosolids and partially treated irrigation water cannot only contribute to changes in the soil microbial community composition but also to increased ARG loads and, likely, to their persistence and dissemination via co-selection when applied to soils. Due to the presence of microbial communities, originating from different sources, together with selective compounds and a high nutrient availability, facilitating metabolic activities and high cell densities, wastewater treatment plants are regarded as hot spots of horizontal gene transfer (HGT), and therefore, biosolids are an important potential transfer gateway between clinical and environmental bacteria.

The concentration of ARB and ARGs released into the environment is not controlled in any case. When ARB, like multi-drug resistant (MDR) pathogens, arrive in the environment, they compete with the indigenous microbiome. Even if they are outcompeted by the autochthonous microbial communities and do not survive, however, they still spread their ARGs to environmental microbes, thereby generating MDR bacteria. These can contaminate crops and are eventually taken up by crops. Thus, there is an urgent need to monitor the release of ARGs on one hand and to assess their transferability in the environment on the other hand to enable appropriate countermeasures.

This Special Issue is open to any high-quality research dealing with:

-Following the path of ARGs and ARB from hospitals, nursing homes, intensive animal husbandry, and municipal wastewater treatment plants to the environment and/or the way back;

-The mechanisms of spread of ARGs and ARB in the environment (mainly focusing on soils and plants);

-The quantification of horizontal gene transfer (HGT) of ARGs in the environment, including the design and application of new methods for quantitative monitoring of ARG transfer on one hand and identification of hot spots of ARG transfer on the other hand.

Prof. Dr. Elisabeth Grohmann
Prof. Dr. Kornelia Smalla
Guest Editors

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