Carbapenem- and colistin-resistant Enterobacter has been a clinical and therapy problem in recent years. Here, we report the carbapenem- and colistin-resistant Enterobacter harboring blaIMI isolated from intestinal samples and the environment of a duck farm in China. Four blaIMI-positive Enterobacter isolates were resistant to carbapenem and colistin. Three blaIMI subtypes were detected in different molecular categories of Enterobacter. The detection of the various IMI producers highlights the diversity of carbapenemases in a duck farm. Whole-genome sequencing demonstrated the blaIMI genes were present in chromosomes or plasmids in these strains. The conjugation experiment demonstrated the ability of blaIMI-carrying plasmid to transmit horizontally. The molecular evolution characteristics were examined through comparative genetic analysis. The study demonstrated the presence of chromosomal and plasmid blaIMI and the blaIMI-carrying plasmid exhibits a horizontal transmission between Enterobacter and Escherichia coli C600. The similar genetic content was discovered between two blaIMI-16-positive Enterobacter asburiae. In addition, a blaIMI-16-carrying plasmid is an IncFII(Yp) plasmid, and a substantial amount of mobile genetic elements were identified around blaIMI-16. The IS-like elements and IncFII(Yp) plasmid are significant in the propagation of blaIMI. Our study provides evidence for the transmission of diverse blaIMI genes in China and supplies additional reference data for blaIMI-positive antimicrobial-resistant Enterobacter. Routine surveys of blaIMI-positive Enterobacter from animal-raising environments must be given more focus

Streptococcus equi subsp. zooepidemicus (SEZ) is an important zoonotic agent.  Here, a virulence-attenuated strain M35246 derived from natural variation of wild-type SEZ ATCC35246 was found.  M35246 showed a deletion of 25 contiguous genes as well as a loss-of-function mutation in covS.  Subsequently, a 25-gene-deleted strain (ΔPI), a covS-mutant strain (McovS), and relevant complementary strains were constructed and investigated.  M35246 and McovS were significantly less encapsulated and exhibited poorer anti-phagocytic capacity compared to wild-type SEZ.  McovS was significantly more sensitive to β-lactams, aminoglycosides, macrolides, and lincosamides than wild-type SEZ.  M35246, McovS, and ΔPI exhibited an increase in median lethal dose (LD₅₀) in mice by 10⁵, 10⁵, and 5 times when compared to wild-type SEZ, respectively.  Neither M35246 nor McovS were isolated from mice 48 h after being challenged with approximately 2 000 times the LD₅₀ of wild-type SEZ.  Transcriptome analysis showed that 668 significantly differentially expressed genes existed between McovS and wild-type SEZ.  Numerous virulence factor-encoding genes and anabolic-related genes in McovS that were involved in anti-phagocytosis, capsule formation, pathogenicity, and antibiotic resistance were downregulated significantly relative to the wild-type strain.  This study revealed that the CovS plays a vital role in the establishment of SEZ virulence

Linoleic acid is an essential polyunsaturated fatty acid that cannot be synthesized by humans or animals themselves and can only be obtained externally.  The amount of linoleic acid present has an impact on the quality and flavour of meat and indirectly affects consumer preference.  However, the molecular mechanisms influencing the deposition of linoleic acid in organisms are not clear.  As the molecular mechanisms of linoleic acid deposition are not well understood, to investigate the main effector genes affecting the linoleic acid content, this study aimed to screen for hub genes in slow-type yellow-feathered chickens by transcriptome sequencing (RNA-Seq) and weighted gene coexpression network analysis (WGCNA).  We screened for candidate genes associated with the linoleic acid content in slow-type yellow-feathered broilers.  A total of 399 Tiannong partridge chickens were slaughtered at 126 days of age, fatty acid levels were measured in pectoral muscle, and pectoral muscle tissue was collected for transcriptome sequencing.  Transcriptome sequencing results were combined with phenotypes for WGCNA to screen for candidate genes.  KEGG enrichment analysis was also performed on the genes that were significantly enriched in the modules with the highest correlation.  A total of 13 310 genes were identified after quality control of transcriptomic data from 399 pectoral muscle tissues.  WGCNA was performed, and a total of 26 modules were obtained, eight of which were highly correlated with the linoleic acid content.  Four key genes, namely, MDH2, ATP5B, RPL7A and PDGFRA, were screened according to the criteria |GS|>0.2 and |MM|>0.8.  The functional enrichment results showed that the genes within the target modules were mainly enriched in metabolic pathways.  In this study, a large-sample-size transcriptome analysis revealed that metabolic pathways play an important role in the regulation of the linoleic acid content in Tiannong partridge chickens, and MDH2, ATP5B, RPL7A and PDGFRA were screened as important candidate genes affecting the linoleic acid content.  The results of this study provide a theoretical basis for selecting molecular markers and comprehensively understanding the molecular mechanism affecting the linoleic acid content in muscle, providing an important reference for the breeding of slow-type yellow-feathered broiler chickens.

Indigenous chicken products are increasingly favored by consumers due to their unique meat and egg quality.  However, the relatively poor egg-laying performance largely impacts the economic benefits and hinders sustainable development of the local chicken industry.  Thus, excavating key genes and effective molecular markers associated with egg-laying performance is necessary to improve egg production via genetic selection in indigenous breeds.  In the present study, comparative hypothalamic transcriptome between pre-laying (15 weeks old) and peak-laying (30 weeks old) Lushi blue-shelled-egg (LBS) chicken was performed.  A total of 518 differentially expressed genes (DEGs) were identified.  Among the DEGs, 64 genes were enriched in 10 Gene Ontology (GO) terms associated with reproductive regulation via GO analysis and considered as potential candidate genes regulating egg-laying performance.  Of the 64 genes, 16 showed high connectivity (degree≥12) by protein–protein interaction (PPI) network analysis and were considered as potential core candidate genes (PCCGs).  To further look for key candidate genes from the PCCGs, firstly, the expression patterns of the 16 genes were examined in the hypothalamus of two indigenous breeds (LBS and Gushi (GS) chickens) between the pre-laying and peak-laying stages using quantitative real-time PCR (qRT-PCR).  Eleven out of the 16 genes showed significantly differential expression (P<0.05) with the same changing trends in the two breeds.  Then, correlations between the expression levels of the above 11 genes and egg numbers and reproductive hormone concentrations in serum were investigated in high-yielding and low-yielding GS chickens.  Of the 11 genes, eight showed significant correlations (P<0.05) between their expression levels and egg numbers, and between expression levels and reproductive hormone concentration in serum.  Furthermore, an association study on single nucleotide polymorphisms (SNPs) identified in these eight genes and egg production traits was carried out in 640 GS hens, and a significant association (P<0.05) between the SNPs and egg numbers was confirmed.  In conclusion, the eight genes, including CNR1, AP2M1, NRXN1, ANXA5, PENK, SLC1A2, SNAP25 and TRH, were demonstrated as key genes regulating egg production in indigenous chickens, and the SNPs sites within the genes might be served as markers to provide a guide for indigenous chicken breeding.  These findings provide a novel insight for further understanding the regulatory mechanisms of egg-laying performance and developing molecular markers to improve egg production of indigenous breeds.

Suppression subtractive hybridization (SSH) was performed with virulent strain ATCC35246 and avirulent strain ST171 to identify novel genes associated with virulence in Streptococcus equi ssp. zooepidemicus (SEZ). There were fourteen genomic regions that only presented in virulent strain ATCC35246. These regions encoded 14 proteins, some of them were homologous to proteins associated with cellular surface structure, molecular synthesis, energy metabolism, regulation, transport systems, and other unknown functions. Primers for 6 particular regions were designed from the already published SEZ sequence. Then, we used PCR to evaluate the distribution and conservation of these 6 DNA fragments in various SEZ strains collected from different sources, regions, groups, and times. The results showed that these 6 DNA fragments were widely distributed in SEZ strains, yet they were not existence in the avirulent strain ST171. Moreover, these fragments could not be detected in other Streptococcus groups.