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Antimicrobial resistance (AMR) is a major threat to global public health, and antibiotic resistance genes (ARGs) are widely distributed across humans, animals, and environment. Farming environments are emerging as a key research area for ARGs and antibiotic resistant bacteria (ARB). While the skin is an important reservoir of ARGs and ARB, transmission mechanisms between farming environments and human skin remain unclear. Previous studies confirmed that swine farm environmental exposures alter skin microbiome, but the timeline of these changes is ill defined. To improve understanding of these changes and to determine the specific time, we designed a cohort study of swine farm workers and students through collected skin and environmental samples to explore the impact of daily occupational exposure in swine farm on human skin microbiome. Results indicated that exposure to livestock‐associated environments where microorganisms are richer than school environment can reshape the human skin microbiome and antibiotic resistome. Exposure of 5 h was sufficient to modify the microbiome and ARG structure in workers' skin by enriching microorganisms and ARGs. These changes were preserved once formed. Further analysis indicated that ARGs carried by host microorganisms may transfer between the environment with workers' skin and have the potential to expand to the general population using farm workers as an ARG vector. These results raised concerns about potential transmission of ARGs to the broader community. Therefore, it is necessary to take corresponding intervention measures in the production process to reduce the possibility of ARGs and ARB transmission. Highlights: Exposure to livestock‐associated environment, more microbially enriched than school environment, can remodel the human skin microbiome and antibiotic resistome.The 5 h of exposure is sufficient to alter the microbiota and antibiotic resistance genes (ARGs) structure of skin and these changes were retained once formed.ARGs carried by host microbes were transferred between the environment and workers' skin. [ABSTRACT FROM AUTHOR]

Objectives: Carbapenems, colistin, and tigecycline are critically important antibiotics in clinics. After the global appearance of bla NDM and mcr mediating the resistance to carbapenems and colistin, respectively, tigecycline becomes the last-resort drug against severe human infections caused by multidrug-resistant bacteria. Recently, a mobile tigecycline resistance gene tet (X4) has been identified in Escherichia coli , Klebsiella pneumoniae , and Acinetobacter baumannii that causes high resistance to tigecycline and other tetracyclines. In this study, the prevalence of tet (X4) in E. coli isolates from duck and goose farms in Southeast China was identified and characterized. Methods: Feces, soil, sewage, and dust samples were collected from duck and goose farms along with the southeast coast provinces of China. Antimicrobial susceptibility testing and polymerase chain reaction screening were performed to investigate the phenotype and genotype of tigecycline resistance. Conjugation, S1 pulsed-field gel electrophoresis (PFGE), and whole-genome sequencing were used to determine the transferability, genetic location, and the genomic characteristics of tet (X4). Results: In total, 1,716 samples were collected, and 16 isolates (0.9%) recovered from Guangdong, Shandong, and Jiangsu were positive for tet (X4) gene with tigecycline minimum inhibitory concentrations ≥16 mg/L. Notably, among these tet (X4)-positive E. coil isolates, seven of them were from the environment samples (soil and sewage). PFGE and multilocus sequence typing demonstrated that ST3997 was the most prevalent sequence type (eight isolates, 50%) in Jiangsu province. By conjugation assays, 11 isolates were able to transfer tet (X4) plasmid to E. coli C600 recipient, and these plasmids belonged to IncHI1 and IncX1 detected by sequence analysis. tet (X4) was found adjacent to an insertion sequence IS CR2 downstream and a cat D gene upstream for all isolates. In addition, multiple-drug resistance to tigecycline, chlortetracycline, ampicillin, florfenicol, ciprofloxacin, gentamicin, trimethoprim/sulfamethoxazole, and fosfomycin was profiled in most of the tet (X4)-positive isolates. Conclusion: The identification of tet (X4) harboring E. coli strains in duck farms and their surrounding environment enlarges our knowledge of the variety and prevalence of tigecycline resistance. The prevalence of tet (X4) raises concern for the use of tetracyclines in animal farming, and the tet (X4) gene should be listed as primary gene for resistance surveillance. [ABSTRACT FROM AUTHOR]

The rapid dissemination of plasmid-mediated tet (X) genes in Acinetobacter species has compromised the clinical effectiveness of tigecycline, one of the last-resort antibiotics. However, the classification strategy and homology group of tet (X)-positive Acinetobacter spp. plasmids remain largely unknown. In this study, we classified them by genome-based replicon typing, followed by analyses of structural characteristics, transferability and in vivo effect. A total of 34 plasmids distributed in at least nine Acinetobacter species were collected, including three tet (X3)-positive plasmids and one tet (X6)-positive plasmid from our genome sequencing results. Among them, there were 28 plasmids carrying Rep&#95;3 superfamily replicase genes and classified into six homology groups, consisting of GR31 (82.1%), GR26 (3.6%), GR41 (3.6%), GR59 (3.6%), and novel groups GR60 (3.6%) and GR61 (3.6%). Our tet (X3)-positive plasmids pYH16040-1, pYH16056-1, and pYH12068-1 belonged to the dominant GR31 group, whereas the tet (X6)-positive plasmid pYH12068-2 was unclassified. Structurally, all tet (X)-positive GR31 plasmids shared similar plasmid replication ( repB ), stability ( parA and parB ) and accessory modules [ tet (X) and sul2 ], and 97.6% of plasmid-mediated tet (X) genes in Acinetobacter species were adjacent to IS CR2 . Conjugation and susceptibility testing revealed pYH16040-1, pYH16056-1, and pYH12068-2, carrying plasmid transfer modules, were able to mediate the mobilization of multiple antibiotic resistance. Under the treatment of tigecycline, the mortality rate of Galleria mellonella infected by pYH16040-1-mediated tet (X3)-positive Acinetobacter spp. isolate significantly increased when compared with its plasmid-cured strain ( p < 0.0001). The spread of such plasmids is of great clinical concern, more effects are needed and will facilitate the future analysis of tet (X)-positive Acinetobacter spp. plasmids., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Chen, Huang, Cui, He, Sun, Liu and Huang.)

Tetracycline and its derivative tigecycline are clinical options against Gram-negative bacterial infections. The emergence of mobile Tet(X) enzymes that destruct tetracycline-type antibiotics is posing a big challenge to antibacterial therapy and food/environmental securities. Here, we present an update on a growing number of Tet(X) variants. We describe structure and action of Tet(X) enzyme, and discuss the evolutional origin. In addition, potential Tet(X) inhibitors are given. This mini-review might benefit better understanding of Tet(X)-mediated tigecycline resistance. This article is categorized under: Infectious Diseases > Genetics/Genomics/Epigenetics Infectious Diseases > Environmental Factors Infectious Diseases > Molecular and Cellular Physiology., (© 2021 Wiley Periodicals LLC.)