The transferable resistance genes optrA and poxtA mediate cross-resistance to florfenicol and linezolid, posing serious challenges to both veterinary and h

Klebsiella pneumoniae as a conditional pathogen has become a worldwide public health issue. It can colonize animals and is capable of transmitting to humans through the food chain, raising serious concerns about antimicrobial resistance (AMR). In this study, the prevalence, phenotypes, genomic characteristics of K. pneumoniae in layer chicken feces were investigated across five regions of Xinjiang, China. From 1115 samples collected, 408 (36.6%) K. pneumoniae were isolated. Antimicrobial susceptibility testing revealed the highest resistance rates to colistin (55.0%) and florfenicol (50.0%). PCR results revealed high detection rate of plasmid-mediated quinolone resistance (PMQR) genes, with oqxA (97.8%) and oqxB (90.4%) being the most prevalent. Among β-lactam-resistance genes, bla_SHV was predominant (97.8%), while bla_CTX-M (10.3%) and bla_TEM (10.5%) showed lower prevalence. The overall detection rate of mcr genes (mcr-1 to mcr-9) was low (0.5%). ESBL-producing isolates were identified in 9.8% (n = 40) of the total strains, indicating the presence of extended-spectrum β-lactamase-mediated resistance mechanisms. Importantly, two mcr-8.2 positive isolates were detected, one of which belonged to the ST147 clone. The backbone structure of the mcr-8.2 positive IncFII plasmid (pCD19-mcr8) identified in this study shared high structural similarity with known mcr-8.2-positive plasmids from chicken, human, and environmental sources. The mcr-8.2 core genetic environment (IS903B-dgkA-baeS-copR-ISEcl1-mcr-8.2-ISKpn26) also found in these plasmids. In addition, transfer of the IncFII plasmid pCD19-mcr8 into E. coli did not result in a significant fitness cost. To our knowledge, this is the first report of mcr-8.2-positive K. pneumoniae in layer chickens in Xinjiang, China. These findings highlight the contribution by mobile genetic elements (MGEs) to cross-species dissemination of colistin resistance and emphasize the necessity of a One Health strategy for monitoring and controlling such pathogens and AMR.

Introduction: African lions (Panthera leo) face severe population declines, making captive breeding programs essential for conservation. However, genetic data scarcity in such programs elevates inbreeding risks and threatens genetic diversity.Methods: Using next-generation sequencing (NGS), we analyzed genome-wide genetic markers from 10 captive African lions at Xinjiang Tianshan Wildlife Park. We identified high-confidence SNPs, evaluated population structure, and calculated kinship/inbreeding coefficients alongside identity by descent (IBD) and identity by state (IBS) analyses.Results: We identified 5,051,795 high-confidence SNPs. The population contained distinct genetic subgroups. Six lion pairs exhibited elevated kinship coefficients, with one individual showing inbreeding signs. We developed a science-driven breeding program based on population genetic structure, identity by descent (IBD) analysis, and Identity by State (IBS) analysis. This program prioritizes pairings with low kinship while maintaining a balanced ancestral lineage.Discussion: This study underscores the importance of genomic tools in managing captive populations, offering actionable insights to mitigate inbreeding risks and improve long-term viability. This approach offers a model for optimizing breeding strategies in other endangered species conservation efforts.

Background/Objectives: The global dissemination of tet(X) variants critically threatens tigecycline efficacy as a last-resort antibiotic. The aim of this study was to characterize a tet(X6)-carrying integrative and conjugative element (ICE) in a multidrug-resistant Chryseobacterium lecithinasegens strain, SHZ29, isolated from Shanghai, China. Methods: Minimum inhibitory concentrations (MICs) were determined by broth microdilution for SHZ29. Whole genomic sequencing and bioinformatic analysis were performed to depict the structure of the novel tet(X6)-carrying ICE. Inverse PCR and conjugation experiments were conducted to investigate the transfer ability of the ICE. Results: We depicted a novel tet(X6)-carrying ICE, named ICECleSHZ29, which is 74,906 bp in size and inserted into the 3′ end of tRNA-Met-CAT gene of the C. lecithinasegens strain SHZ29, with 17 bp direct repeats (5′-tcccgtcttcgctacaa-3′). This ICE possesses a 38 kb conserved backbone and four variable regions (VR1-4), with VR3 aggregating multiple resistance genes, including tet(X6), tet(X2), erm(F), ere(D), floR, catB, sul2, ant(6)-I and bla_OXA-1327. NCBI database searching identified 13 additional ICEs sharing a similar backbone to ICECleSHZ29. These ICECleSHZ29-like ICEs could be classified into two types based on their distinct insertion sites: Type I, inserted at the tRNA-Met-CAT gene; and Type II, inserted at the tRNA-Glu-TTC gene. Phylogenetic analysis indicated that differences in integrases may result in differences in the insertion site among these ICEs. A circular intermediate form of ICECleSHZ29 was detected by inverse PCR. However, the conjugation experiments using Escherichia coli EC600 as recipients failed. Conclusions: To our knowledge, this study provides the first report of tet(X6) in C. lecithinasegens and characterizes its carrier, a novel ICE: ICECleSHZ29.

The dissemination of New Delhi metallo-β-lactamase (NDM)-producing Escherichia coli poses a serious threat to public health. Although increasing attention has been paid to the relationship between temperature and antimicrobial resistance (AMR) transmission, research in China’s Xinjiang region remains scarce. In this study, we conducted a cross-sectional survey of 1914 samples from intensive livestock farms across Xinjiang to characterize the detection rate and antimicrobial resistance profiles of bla_NDM-positive E. coli. Using selective culture, PCR, and 16S rRNA sequencing, we identified 140 bla_NDM-positive E. coli (7.3%), predominantly in northern Xinjiang. The highest detection rate of bla_NDM-positive E. coli was found in Tacheng Prefecture (24.0%), followed by Changji Hui Autonomous Prefecture (4.3%) and Bortala Mongol Autonomous Prefecture (0.6%). No bla_NDM-positive E. coli isolates were detected in Bayingolin Mongol Autonomous Prefecture, Kashgar Prefecture, or from pigeon samples. Binomial logistic regression analysis revealed a significant positive association between regional temperature and the detection rate of bla_NDM-positive E. coli. Genotypic analysis identified 35 distinct resistance gene profiles, with predominant resistance genes including bla_TEM (87.9%), ant(3″)-Ia (97.1%), qnrS (92.9%), tet(A) (95.0%), sul1 (70.0%), sul3 (85.0%), and floR (97.1%); mcr-1 and mcr-8 were not detected. Antibiotic susceptibility tests showed that all isolates were resistant to imipenem and exhibited universal resistance to ampicillin, ceftiofur, tetracycline, florfenicol, and enrofloxacin, whereas the majority remained susceptible to amikacin (99.3%), tigecycline (94.3%), and polymyxin (77.1%). These findings indicate that livestock farms, particularly laying-hen systems in northern Xinjiang, may serve as reservoirs of multidrug-resistant bla_NDM-positive E. coli, and that elevated regional temperature is an environmental factor associated with higher detection rates, underscoring a potential climate-associated risk for the spread of AMR.