Sun, R.-Y. | bioRxiv Science

bioRxiv2021

Source tracking and global distribution of the mobilized tigecycline resistant gene tet(X)

The emergence of tet(X) genes has compromised the clinical use of the last-line antibiotic tigecycline. We identified 322 (1.21%) tet(X) positive samples from 12,829 human microbiome samples distributed in four continents (Asia, Europe, North America and South America) using retrospective data from worldwide. These tet(X) genes were dominated by tet(X2)-like orthologs but we also identified 12 samples carrying novel tet(X) genes, designed tet(X15) and tet(X16), that were resistant to tigecycline. The metagenomic analysis revealed these tet(X) genes distributed in anaerobes dominated by Bacteroidaceae (78.89%) of human-gut origin. The transmission of these tet(X2)-like orthologs between Bacteroidaceae and Riemerella anatipestifer was primarily promoted by the mobile elements ISBf11 and IS4351. tet(X2)-like orthologs was also developed during transmission by mutation to high-level tigecycline resistant determinants tet(X15) and tet(X16). Further tracing these tet(X) in single bacterial isolate from public repository indicated that tet(X) genes were present as early as 1960s in R. anatipestifer that was the primary tet(X) carrier at early stage (before 2000). The tet(X2) and non-tet(X2) orthologs were primarily distributed in humans and food animals respectively, and non-tet(X2) were dominated by tet(X3) and tet(X4). Genomic comparison indicated these tet(X) genes were likely to be generated during tet(X) transmission between Flavobacteriaceae and E. coli/Acinetobacter spp.., and ISCR2 played a key role in the transmission. These results suggest R. anatipestifer was the potential ancestral source of tet(X) gene. Additionally, Bacteroidaceae of human-gut origin was an important hidden reservoir and mutational incubator for the mobile tet(X) genes that enabled spread to facultative anaerobes and aerobes.

bioinformatics↗

bioRxiv2019

Pluripotent Stem Cells Can Be Isolated from Human Peripheral Nerves after in vitro BMP-2 Stimulation

We have recently identified a population of cells within the peripheral nerves of adult mice that can respond to BMP-2 exposure or physical injury to rapidly proliferate. More importantly, these cells exhibited embryonic differentiation potentials that could be induced into osteoblastic and endothelial cells in vitro. The current study examined human nerve specimens to compare and characterize the cells after BMP-2 stimulation. Fresh pieces of human nerve tissue were minced and treated with either BMP-2 (750ng/ml) or vehicle for 12 hours at 37{degrees}C, before digested in 0.2% collagenase and 0.05% trypsin-EDTA. Isolated cells were cultured in restrictive stem cell medium. Significantly more cells were obtained from the nerve pieces with BMP-2 treatment in comparison with the non-treated controls. Cell colonies were starting to form at day 3. Expressions of the 4 transcription factors Klf4, c-Myc, Sox2 and Oct4 were confirmed at both transcriptional and translational levels. The cells can be maintained in the stem cell culture medium for at least 6 weeks without changing morphologies. When the cells were switched to fibroblast growth medium, dispersed spindle-shaped cells were noted and became fibroblast activated protein- (FAP) positive following immunocytochemistry staining. The data suggested that human peripheral nerve tissue also contain a population of cells that can respond to BMP-2 and express all four transcription factors KLF4, Sox2, cMyc, and Oct4. These cells are capable to differentiate into FAP-positive fibroblasts. It is proposed that these cells are possibly at the core of a previously unknown natural mechanism for healing injury.

cell biology↗