● Metals are increasingly important risk factors for the evolution of antibiotic resistance in environments.

The rapid development of antibiotic resistance is occurring at a global scale. We therefore stride into the post-antibiotic era and have to battle antibiotic resistance in the Anthropocene. Metals are widely used and their pollution is widespread worldwide. More importantly, metal-induced co-selection greatly expands the environmental resistomes and increases the health risk of antibiotic resistance in environments. Here, we reviewed the metal-induced co-selection and their increasingly important roles in the development of antibiotic resistance. In particular, we highlight the metal-rich environments that maintain reservoirs for high-risk antibiotic resistance genes with horizontally transferable potentials. We also call for considerations and further investigations of other co-selective agents and the efficacy of metal-based interventions to better manage and combat the global antibiotic resistance crisis within the One Health framework.

● ARGs and ARB in typical environments which exposed to antibiotics are prevalent.

Antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) in the environment pose serious threats to environmental security and public health. There is an urgent need for methods to specifically and effectively control environmental pollution or pathogen infection associated with ARGs and ARB. This review aims to provide an overview of methods abating the prevalence and spread of ARGs and ARB from species to community level. At the species level, species-specific technologies, such as nanoparticle-, photosensitizer-, CRISPR-Cas-, and phage-related technology can be utilized to clear a particular class of ARGs or ARB, and in combination with low-dose antibiotics, a higher removal efficiency can be achieved. Moreover, the combination of antibiotics can be used to reverse microbial resistance and treat recurrent antibiotic resistant pathogen infections. At the community level, community-specific strategies, such as biochar, hyperthermophilic compost, and fecal microbiota transplantation can eradicate most types of ARGs or ARB in one shot, reducing the probability of resistance development. Though some progress has been made to eliminate ARGs and ARB in disease treatment or decontamination scenarios, further research is still needed to elucidate their mechanisms of action and scopes of application, and efforts should be made to explore novel strategies to counter the prevalence of antibiotic resistance.

● ARB was investigated in different soil types following manure application.

Swine manure, commonly applied as organic compost in agricultural fields, is an important reservoir of antibiotic-resistant bacteria (ARB). Previous work indicated that manure application led to more antibiotic resistance genes in red soil compared with black soil and fluvo-aquic soil. Accordingly, the influencing mechanisms of soil types on the distribution of ARB was worthy of further exploration by a soil column experiment. The results showed that a higher shift in the operational taxonomic units and the community composition of chlortetracycline (CTC)-resistant bacteria (CRB) were observed in fluvo-aquic soil than in black and red soils. CTC induced antibiotic resistance development in soil indigenous microorganisms (Streptomyces, Pseudomonas, Bacillus, Rhodococcus, and Paenibacillus), and the induction was most obvious in fluvo-aquic soil. Streptomyces was significantly positively correlated with pH and organic matter. Additionally, LEfSe analysis indicated that the key different genera were Microbacteriaceae (black soil), Lactobacillus, unclassified_c__Bacilli and Paenibacillus (fluvo-aquic soil), and Dyella, Ralstonia and Bacillus (red soil). It was concluded that manure application led to higher CRB risk in fluvo-aquic soil compared with black and red soils. Overall, appropriate methods according to soil types are important ways to reduce the risk of soil resistant bacteria during manure return.

● Gentamicin initially decreased microbial activity comparative to penicillin higher.

This study aimed to describe the static and cidal adverse effects of antibiotics on soil microbial activity resulting from manure application. So, in the present study, the treatments included: without antibiotics; application of gentamicin, oxytetracycline, and penicillin each in different concentrations (50, 100, and 200 mg kg⁻¹ dry soil). They were applied in soils treated with and without organic and mineral conditioners (cow manure, biochar, and nano-zeolite). Soil microbial respiration and metabolic quotient were studied at three time periods (1−7, 7−30, and 30−90 days) during a 90-day incubation of the treated soils. Antibiotics applied to the soil samples significantly decreased soil basal respiration (BR) values compared to those of the control, and the most significant decrease was observed for gentamicin. Gentamicin had a short intensive impact, alleviated by manure and biochar, on soil copiotrophs. After a significant initial reduction in substrate-induced respiration (SIR), gentamicin application then caused a substantial increase in SIR values. Unexpectedly metabolic quotient decreased in the antibiotic-treated soils. This study revealed that the static effects of the applied antibiotics in soil were greater than the cidal effects.