The emergence of carbapenem-resistant Enterobacteriaceae strains has posed a severe threat to public health in recent years. The mobile elements carrying the New Delhi metallo-β-lactqtamase (NDM) gene have been regarded as the major mechanism leading to the rapid increase of carbapenem-resistant Enterobacteriaceae strains isolated from clinics and animals. We describe an NDM-5-producing Escherichia coli strain, ECCRA-119 (sequence type 156 [ST156]), isolated from a poultry farm in Zhejiang, China. ECCRA-119 is a multidrug-resistant (MDR) isolate that exhibited resistance to 27 antimicrobial compounds, including imipenem and meropenem, as detected by antimicrobial susceptibility testing (AST). The complete genome sequence of the ECCRA-119 isolate was also obtained using the PacBio RS II platform. Eleven acquired resistance genes were identified in the chromosome; four were detected in plasmid pTB201, while six were detected in plasmid pTB202. Importantly, the carbapenem-resistant gene blaNDM-5 was detected in the IncX3 plasmid pTB203. In addition, seven virulence genes and one metal-resistance gene were also detected. The results of conjugation experiments and the transfer regions identification indicated that the blaNDM-5-harboring plasmid pTB203 could be transferred between E. coli strains. The results reflected the severe bacterial resistance in a poultry farm in Zhejiang province and increased our understanding of the presence and transmission of the blaNDM-5 gene.

Staphylococcus aureus biofilms are a serious problem in the food industry. Wall teichoic acid (WTA) is crucial in S. aureus biofilm formation. Overexpression of the WTA-hydrolyzing enzyme glycerophosphoryl diester phosphodiesterase (GlpQ), induced by lactobionic acid (LBA), may be related to biofilm formation. We investigated the relationship between the regulation on GlpQ degradation of WTA by LBA and S. aureus biofilm formation. LBA minimum inhibitory concentration for S. aureus was 12.5 mg/mL. Crystal violet staining revealed the LBA-mediated inhibition of S. aureus adhesion and biofilm formation. RT-qPCR revealed the repressed expression of adhesion-related genes by LBA. Scanning electron microscopy revealed the obvious disruption of S. aureus surface structure, confirming the repression of S. aureus adhesion and biofilm formation by LBA. Native-PAGE results suggested that the WTA content of S. aureus was reduced under the inhibition of LBA. Additionally, LBA induced the overexpression of glpQ. Combined with our previous work, these results suggest that glpQ is induced in S. aureus to function in WTA degradation with the addition of LBA, resulting in decreased WTA content and subsequent reduction of adhesion and biofilm formation. The findings provide new insight into the degradation mechanism of S. aureus WTA and indicate the potential of LBA as an anti-biofilm agent.

Colistin is used as one of the last-resort drugs against lethal infections caused by carbapenem-resistant Enterobacteriaceae family of pathogens. Enterobacteriaceae bacteria carrying the mcr-1 colistin resistance gene are emerging in livestock and poultry, posing a serious threat to human health. However, the prevalence and transmission of mcr-1 along the regional chicken supply chain remain rarely reported. In this study, the complete sequences of mcr-1 -positive Escherichia coli ST2705 and ST206 isolates obtained by screening 129 chilled chicken samples and 251 chicken fecal samples were investigated. Both of these isolates showed resistance to colistin, and importantly, the complete sequence of the mcr-1 -positive E. coli ST2705 in China was reported for the first time. The mcr-1 gene was located on the IncHI2 plasmids pTBMCR421 (254,365 bp) and pTBMCR401 (230,964 bp) in strains ECCNB20-2 and ECZP248, respectively. Comparative analysis of mcr-1 -bearing IncHI2 plasmids showed a marked similarity, indicating that these plasmids are very common and have the ability to be efficient vehicles for mcr-1 dissemination among humans, animals and food. Furthermore, an insertion (IS Kpn26 ) in Tn 6330 (IS Apl1 - mcr- 1- pap2 -IS Apl1 ) was identified in the plasmid pTBMCR401 and then compared; this insertion might affect the adaptability and stability of Tn 6330 . Taken together, these findings suggest that the IncHI2 plasmid might be a main factor affecting the transmission of mcr-1 in the chicken supply chain and that the genetic context of the mcr-1 -bearing IncHI2 plasmid is constantly evolving.

Adaptation to sublethal amounts of ethanol enables Salmonella Enteritidis to survive under normally lethal ethanol conditions, which is referred to as the ethanol tolerance response (ETR). To uncover mechanisms underlying this adaptative response, RNA-seq and RT-qPCR techniques were employed to reveal global gene expression patterns in S. Enteritidis after sublethal ethanol treatment. It was observed that 811 genes were significantly differentially expressed in ethanol-treated cells compared with control cells, among which 328 were up-regulated and 483 were down-regulated. Functional analysis revealed that these genes were enriched in different pathways, including signal transduction, membrane transport, metabolism, transcription, translation, and cell motility. Specifically, a couple of genes encoding histidine kinases and response regulators in two-component systems were up-regulated to activate sensing and signaling pathways. Membrane function was also influenced by ethanol treatment since ABC transporter genes for transport of glutamate, phosphate, 2-aminoethylphosphonate, and osmoprotectant were up-regulated, while those for transport of iron complex, manganese, and ribose were down-regulated. Accompanied with this, diverse gene expression alterations related to the metabolism of amino acids, carbohydrates, vitamins, and nucleotides were observed, which suggested nutritional requirements for S. Enteritidis to mount the ETR. Furthermore, genes associated with ribosomal units, bacterial chemotaxis, and flagellar assembly were generally repressed as a possible energy conservation strategy. Taken together, this transcriptomic study indicates that S. Enteritidis employs multiple genes and adaptation pathways to develop the ETR.

Background: Staphylococcus aureus, particularly MRSA strains, poses a critical global health threat due to its multidrug resistance and virulence. Objectives: This study elucidates the role of the acnA gene, encoding aconitase in the tricarboxylic acid (TCA) cycle, in governing virulence and antimicrobial resistance in MRSA. Methods: The identification of the acnA mutant was performed by a transposon mutant library. The function of the acnA gene on virulence was evaluated through deletion and complementation analyses. Other phenotypes of ΔacnA were also determined, including growth curve, cell wall structure observations using scanning and transmission electron microscopy (SEM/TEM), cell wall thickness, autolysis and the determination of energy metabolism-associated phenotypes. MICs for BAA1717 and ΔacnA were determined by antimicrobial susceptibility testing. Finally, virulence- and resistance-related gene expression levels were determined by RT–qPCR. Results: Deletion of acnA in MRSA strain BAA1717 abolished staphyloxanthin biosynthesis and haemolytic activity, disrupted cell wall integrity and reduced resistance to β-lactams, aminoglycosides, macrolides and vancomycin, with MICs decreasing by 2- to 128-fold. Structural defects in the cell wall, visualized via SEM and TEM, correlated with heightened autolysis rates. Metabolic dysfunction in the acnA mutant was evident through diminished ATP production, NADPH synthesis and membrane potential. Transcriptional profiling revealed significant downregulation of virulence-related genes (crtO, crtP, hla, hlgA and hlyIII) and resistance determinants (sepA, norA, ftsW, pbps, murC and lytR). Conclusions: These findings establish acnA as a metabolic nexus coordinating virulence and antimicrobial resistance in MRSA, highlighting its potential as a therapeutic target to disarm persistent infections through metabolic interference.