Gene transfer from NDM-5-producing and OXA-48-producing Enterobacter hormaechei ST79 on contaminated dicloxacillin capsules to other Enterobacterales in Europe, 2020-23: a retrospective, observational, molecular epidemiological study.

This study reports the draft genome sequence of Enterobacter hormaechei ML02, isolated from mangrove-associated rhizosphere soil in Bangladesh. The assembled genome is 4,874,798 base pairs in length, distributed across 80 contigs, with a GC content of 55.5%, and encodes 4,565 predicted protein-coding genes.

Antimicrobial resistance and virulence in polymicrobial chronic wound infections: A metagenomic perspective.

Outbreak investigations of two carbapenemase-producing bacteria (CPB)-clusters identified a link to utility room wastewater drains (URWD), prompting an investigation into CPB-colonization of the hospital's URWD and into utility room management to identify possible breaches in infection prevention and control (IPC) measures. At the University Hospital Basel, Switzerland, a cluster of four patients with VIM-1-producing Enterobacter hormaechei and two patients with KPC-3-producing Citrobacter freundii, occurred between 07/2022 - 07/2024. A multidisciplinary team (IPC specialists, nurses, cleaning experts) evaluated utility room management. Wastewater drains in affected patient rooms and 25 utility rooms of the hospital building (including two wards in which the two transmission-cluster occurred) affected by the clusters were screened for CPB-colonization and whole genome sequencing was performed on clinical and environmental CPB isolates. The blaVIM-1 and the blaKPC-3 gene corresponding to both clusters were identified in sequences of Citrobacter freundii and Klebsiella pneumoniae isolates colonizing the ward's URWD. Colonized drains were in proximity to affected patient's rooms, while none of the wastewater drains in the respective patient rooms was colonized with CPB. Overall, CPB were identified in 52% of all URWD. Several breaches in utility room management and design facilitating colonization with CPB and potentially leading to contamination of shared medical equipment by dispersal were observed, including lacking separation between clean and contaminated zones in utility rooms (34%), and improper use of contaminated zones for storage of clean shared medical equipment (88.7%). URWD serve as reservoirs for CPB. Breaches in utility room management and design, potentially leading to contamination of shared medical equipment by dispersal from contaminated wastewater drains, represent an intervention target for prevention of CPB-transmission.

Silent carriage of mcr-9 on IncHI2 plasmid in an Enterobacter hormaechei strain causing a urinary tract infection in a dog from Portugal.

Emergence and diversity of IncHI2 plasmids co-carrying carbapenemase genes and mcr-9.1/9.2 in Enterobacter hormaechei from a Chinese children's hospital.

Community-acquired multidrug-resistant (MDR) Enterobacterales bacteria are an increasing public health concern, yet whether households play a role in community spread remains unclear. We investigated 150 households with children in St. Louis, Missouri, USA, for MDR Enterobacterales. We cultured swab specimens from household members and environmental surfaces for identification and antimicrobial susceptibility testing. We also performed whole-genome sequencing in the 53 (35%) households where >1 MDR Enterobacterales species were recovered. Enterobacter hormaechei predominated, followed by Klebsiella pneumoniae and Pantoea species. Whole-genome sequencing revealed closely related strains shared between persons and environmental surfaces, suggesting potential intra-household transmission. We identified >1 horizontal gene transfer event between Enterobacterales genera within a household. On multivariable analysis, households that had children attending daycare, a member with an ADHD diagnosis, and dog ownership were associated with increased odds of household MDR Enterobacterales colonization. Households likely serve as major contributors in acquisition and community spread of MDR Enterobacterales.

Distillery industry generates large amounts of spent wash, containing melanoidin. Its resistance to biodegradation, high oxygen demand and toxicity is of critical concern due to its ecological impact on aquatic ecosystems, soil fertility, and crop viability. While conventional treatment methods are inefficient, microbial degradation offers a green, cost-effective alternative. This study aimed to isolate and screen melanoidin-decolorizing bacteria from distillery wastewater. Decolorization studies were carried out using synthetic melanoidin in four different media. Role of laccase and manganese peroxidase enzyme activities of the were evaluated. 16S rRNA sequencing revealed the isolates as Bacillus subtilis, Enterobacter hormaechei and Priestia aryabhattai. P. aryabhattai showed the highest melanoidin decolourization efficiency of 87.89% in minimal salt media, followed by E. hormaechei with 85.39% in nutrient broth, and Bacillus subtilis with 79.82% in minimal salt medium at 96 hours of incubation. All three strains demonstrated effective decolourization under optimal conditions of 37°C and pH 7. Tests on the germination of Vigna radiata seeds and on the growth of Rhizobium leguminosarum suggested the degraded products are non toxic. The findings demonstrate that the isolated strains have strong potential for effective and eco-friendly remediation of melanoidin in distillery wastewater, offering a valuable biotechnological tool for wastewater treatment.

Urinary tract infections (UTIs) are among the most prevalent bacterial infections worldwide, posing a significant health burden, particularly in the context of rising antimicrobial resistance. The increasing ineffectiveness of conventional antibiotics has necessitated the exploration of alternative therapeutic approaches, especially those derived from natural plant-based sources. This study aimed to evaluate the antimicrobial efficacy of Cymbopogon citratus (lemongrass) leaf extracts against multidrug-resistant uropathogens. Extracts were prepared using three solvents: methanol, ethanol, and n-hexane, and tested against three clinically relevant bacterial strains: Escherichia coli, Bacillus subtilis, and Enterobacter hormaechei subsp. xiangfangensis. Phytochemical screening revealed that extracts contained a wide variety of bioactive compounds, including alkaloids, flavonoids, saponins, tannins, terpenoids, phenols, coumarins, and volatile oils. Further analysis using Fourier-transform infrared spectroscopy identified characteristic functional groups, including O-H, C-H, C = O, C = C, and N-H, indicating the presence of alcohols, aldehydes, ketones, alkenes, and amines, which are often associated with antimicrobial activity. Antibacterial assays showed that the methanolic extract exhibited the strongest inhibitory activity. In disc diffusion tests, it produced the largest zones of inhibition: 14mm against Escherichia coli, 14mm against Bacillus subtilis, and 13mm against Enterobacter hormaechei subsp. xiangfangensis. Minimum inhibitory concentration values further confirmed its superior potency, with results of 3.12mg/mL for Escherichia coli, 6.25mg/mL for Bacillus subtilis, and 12.5mg/mL for Enterobacter hormaechei subsp. xiangfangensis. The extract also showed bactericidal activity, with minimum bactericidal concentrations of 12.5mg/mL for Escherichia coli and 25mg/mL for the other two strains. In summary, this study provides strong evidence that Cymbopogon citratus, particularly when extracted with methanol, possesses significant antibacterial and antioxidant properties against multidrug-resistant uropathogens. These findings support its potential use as a complementary or alternative therapeutic agent in managing resistant urinary tract infections, offering a promising natural strategy to address the growing challenge of antimicrobial resistance. IMPACT STATEMENT. Methanolic extracts of Cymbopogon citratus demonstrated strong antibacterial and bactericidal activity against multidrug-resistant uropathogens, including Escherichia coli and Enterobacter hormaechei subsp. xiangfangensis. Phytochemical and FTIR analyses confirmed the presence of bioactive functional groups associated with antimicrobial effects. These findings highlight lemongrass as a promising plant-based candidate for developing complementary therapies to address antimicrobial resistance in urinary tract infections and support further pharmacological standardization and clinical investigation.

Carbapenemase-producing Enterobacterales (CPE) are a major public health concern. Within the Enterobacter cloacae complex (ECC), the blaVIM-1 carbapenemase gene is frequently plasmid-borne, enabling inter-clonal and inter-species spread that complicates the detection and control of carbapenemase dissemination. We investigated an increase in VIM-1-producing Enterobacter spp. reported to the Swiss National Reference Center for Emerging Antibiotic Resistance (NARA) between 2022 and 2024 using high-resolution genomic methods. Between January 2022 and October 2024, blaVIM-1-positive Enterobacter spp. isolates from 39 patients, plus additional contemporary blaVIM-1-positive Enterobacterales, were analyzed. Whole-genome sequencing (Illumina) was performed for all isolates, with long-read sequencing (Oxford Nanopore Technologies) for 12 selected isolates. Species identification, genomic relatedness by MLST and cgMLST, and fine-scale plasmid characterization and comparison were performed. Most isolates were Enterobacter hormaechei (n = 37), alongside Enterobacter kobei (n = 1) and Enterobacter ludwigii (n = 1), distributed across 13 sequence types, excluding purely clonal dissemination. Hybrid assemblies showed blaVIM-1 located on several plasmid types. IncHI2 plasmids of 249-343 kb carrying additional antimicrobial resistance promoting genes including mcr-9 predominated, spanning multiple ECC lineages and also present in two other species. Conjugation of these was confirmed experimentally, and within-host plasmid variation was observed. No further cases occurred after October 2024. We describe a multiclonal spread of blaVIM-1 Enterobacterales in Switzerland, mediated by IncHI2 plasmids. These findings highlight the need for plasmid-focused genomic surveillance to complement clonal typing in CPE outbreak investigations.

To investigate the emergence of resistance to cefiderocol (FDC) in clinical Enterobacter hormaechei isolates and to elucidate the underlying genetic mechanisms, with particular focus on mutations in a putative TonB-dependent receptor (TBDR). Five non-duplicate clinical FDC-susceptible E. hormaechei isolates were exposed to stepwise increasing concentrations of FDC using disk diffusion and broth microdilution to select for spontaneous FDC-resistant mutants. WGS was performed to identify resistance-associated mutations. Site-directed mutagenesis via CRISPR-Cas9 was employed to confirm causality. Bacterial fitness was evaluated by growth curve experiments under both standard and iron-depleted conditions. Six spontaneous mutants exhibited increased FDC MICs ranging from 2 to 16 mg/L. All mutants carried distinct mutations in the TBDR gene, including frameshift mutations and premature stop codons. CRISPR-engineered strains harbouring identical mutations displayed the same resistance phenotype, confirming that disruption of TBDR is sufficient to confer increased FDC resistance. Susceptibility to other β-lactams remained unaffected. Growth analyses did not reveal an obvious growth defect in TBDR mutants compared to the parental strain under the tested in vitro conditions, including iron-depleted media. This study identifies mutations in a putative TBDR as a key mechanism mediating FDC resistance in E. hormaechei. The absence of an obvious growth defect under the tested in vitro conditions suggests that loss of this receptor does not impose a major growth disadvantage. These findings underscore the role of TBDRs in FDC uptake and highlight the potential for resistance development under antibiotic selection pressure through disruption of siderophore-mediated uptake pathways.

Mosquitoes are vectors of deadly, life-threatening diseases worldwide. There is limited information on the interactions between microbes and local mosquito fauna in the Nigerian ecotype and Osun State. This study employed molecular techniques to characterize microorganisms isolated from the internal tissues of adult mosquitoes reared from larvae and pupae collected from various breeding sites in the Osogbo metropolis, Nigeria. Bacteria and yeasts were isolated from immobilized, surface-sterilized, and homogenized mosquitoes. Molecular identification of microbes was based on the Polymerase Chain Reaction (PCR) technique and sequencing of the 16S rDNA gene and internal transcribed spacer (ITS) region for bacteria and yeasts, respectively. The genus Wolbachia was screened with PCR using Wolbachia-specific primers. The adult mosquitoes harboured bacteria, namely Enterobacter bugandensis, Staphylococcus haemolyticus, Staphylococcus capitis, Enterobacter hormaechei, Pantoea dispersa, Sphingobium yanoikuyae, and Aerococcus urinaeequi. Yeasts identified were Meyerozyma caribbica, Rhodotorula mucilaginosa, and Candida orthopsilosis. The genus Wolbachia was not detected in the mosquitoes. The bacteria and yeast isolates from this study can play important roles in the biology of mosquitoes. Notably, S. yanoikuyae possesses bio-degradative potential, as reported in previous studies. Hence, this underscores the need for further investigation of the role of Sphingobium species in mosquito resistance to insecticides.

Therapeutic potential of three virulent bacteriophages targeting clinical Enterobacter hormaechei strains: comprehensive biological properties and genomic functional analysis.

Mitigation of lead-induced soil toxicity and plant growth promotion by phosphate-solubilizing bacterium Enterobacter hormaechei KR2215 isolated from mangrove rhizosphere.

Essential role of the leucine-293 for the AmpC β-lactamase in the resistance to cefepime, cefiderocol, and new β-lactams/β-lactamase inhibitor combinations in Enterobacter hormaechei.

The increasing detection of pharmaceutical micropollutants in aquatic environments raises concerns due to their persistence and incomplete removal in conventional wastewater treatment plants (WWTPs). Among the various biological approaches, bacterial consortia are an effective strategy for enhancing biodegradation efficiency. This study investigated the biodegradation of N-acetyl-para-aminophenol, also known as acetaminophen (APAP or paracetamol), using a local bacterial consortium composed of Enterobacter hormaechei subsp. xiangfangensis A10, Bacillus cereus A16, and Enterobacter hormaechei subsp. xiangfangensis A17. These strains were isolated from a WWTP and household compost. An antagonism assay confirmed the compatibility of the three strains in co-culture. Batch experiments were conducted in a minimal medium containing APAP (100mgL-1) under metabolic conditions and with the addition of glucose (50mgL-1) under co-metabolic conditions. The experiments were performed at 37°C and 150rpm for up to 72h. The APAP degradation kinetics was evaluated and successfully described using appropriate kinetic models, which provided quantitative insight into the performance of the consortium. HPLC and LC-MS analyses revealed that 80.33 ± 1.21% of APAP were removed under metabolic conditions, whereas the removal efficiency decreased to 50.40 ± 1.32% in the presence of glucose. Several transformation products were identified, including 4-aminophenol, hydroquinone, and muconic acid. The consortium exhibited resistance to several co-pollutants, including heavy metals and antibiotics, with the exception of nickel. Overall, these findings demonstrate the potential of the selected bacterial consortium for APAP bioremediation while highlighting the need for further studies that integrate process optimization and mechanistic investigations to achieve complete degradation.

The global rise of carbapenem-resistant Pseudomonas aeruginosa (CRPA) poses a significant threat to public health. Through active surveillance conducted between 2021 and 2022, we collected 92 distinct CRPA isolates and identified a clonal shift toward high-risk lineages ST235* and ST292. Whole-genome sequencing and phylogenomic analysis revealed that ST235*, a single-locus variant of epidemic ST235, exhibited broader antimicrobial resistance (AMR) and carried a nalD loss-of-function mutation, resulting in MexAB-OprM overexpression. Two ST235* isolates contained a hybrid resistance cassette with bla KPC-2 and bla TEM-1, likely acquired through IS26-mediated transfer from Enterobacter hormaechei. Most ST292 isolates demonstrated an extensively drug-resistant phenotype with a bla CARB-2-containing cassette and a chromosomally integrated tMexC3D-OprJ efflux system. Additionally, ST244 isolates possessed a bla VIM-2 cassette embedded within a Tn402 transposition module (tniABQR-intI1). Multiple copies of tniABQR-intI1 carrying AMR genes were exclusively found in the genomes of ST244, representing a novel mechanism. The genomic plasticity of high-risk CRPA lineages emphasizes their capacity to acquire, amplify and disseminate AMR determinants. To combat the spread of CRPA, genomic surveillance and targeted infection control strategies are urgently required.

Honey bees rely on a specialized gut microbiota for nutrition, detoxification, and immune function, yet the effects of emerging insecticides on this symbiotic system remain poorly understood. We compared the acute toxicity and short-term gut microbiota responses of Apis mellifera ligustica workers exposed to two insecticides with contrasting toxicity classes: the highly toxic emamectin benzoate-lufenuron (EB-LFR) and the low-toxicity ecdysone agonist RH-5849. EB-LFR was associated with observed reductions in core gut symbionts (Gilliamella, Snodgrassella, Lactobacillus), a transient increase in Bifidobacterium, and the detection of opportunistic taxa such as Serratia marcescens and Enterobacter hormaechei. In contrast, RH-5849 was associated with broad reductions in beneficial bacteria without detectable pathogen emergence, suggesting a more moderate alteration of microbiota composition. Because microbiota analyses were based on single pooled samples per treatment, these results represent exploratory, qualitative insights into early microbial responses. Together with acute toxicity data, the findings suggest that insecticides with contrasting toxicity classes may differentially affect gut microbiota composition in honey bees and highlight the value of incorporating gut microbiota endpoints into pesticide risk-assessment frameworks to better anticipate sublethal effects on pollinator health.

BackgroundEnterobacter hormaechei (E. hormaechei) is an opportunistic pathogen in poultry, increasingly associated with multidrug resistance due to the extensive use of antibiotics in animal production. The emergence of resistant E. hormaechei strains poses a significant threat to poultry health and food safety, highlighting the urgent need for alternative antimicrobial strategies. This study aimed to isolate and characterize a novel lytic bacteriophage targeting E. hormaechei and to evaluate its biological properties and therapeutic potential in a gastrointestinal infection mice model.ResultsA lytic phage, designated S18-3, was isolated from environmental water using E. hormaechei strain HZW1 isolated from diseased broiler liver. Phage S18-3 forms clear plaques (~ 0.6 cm) and exhibits an icosahedral head with a long tail. Optimal infectivity occurs at an MOI of 0.1. S18-3 remains stable from 30 to 50 °C and tolerates a broad pH range (pH 4–11). Whole-genome sequencing revealed no known virulence factors or antimicrobial resistance genes, indicating favorable genetic safety. In a murine intestinal infection model established by antibiotic pretreatment and oral challenge, E. hormaechei caused significant weight loss and mortality. Oral administration of S18-3 markedly improved survival and mitigated weight loss compared with infected controls. Phage S18-3 titers were detectable in feces in infection group, with only transient, low-level presence in blood. Histopathology showed no evident liver injury or inflammatory changes, suggesting no hepatotoxicity associated with phage treatment.ConclusionsPhage S18-3 is a stable, genetically safe lytic phage that effectively alleviates intestinal E. hormaechei infection in a murine model without observable adverse effects. These data support the potential of S18-3 as an antibiotic alternative for controlling E. hormaechei infections in poultry. Further validation in broiler models and farm-level settings is warranted to assess translational applicability in sustainable poultry production.

Carbapenem-resistant Enterobacter hormaechei (CR-Eh) represents a critical global health threat, especially when carrying mobile antimicrobial resistance genes (ARGs) like blaNDM and mcr. This study characterized three clinical CR-Eh isolates in the context of global genomic datasets, identifying distinct patterns of resistance gene carriage. Notably, blaNDM-1 was found duplicated on the chromosome of strain BC18 but resided on plasmids in other isolates. In contrast, mcr-9 was detected in a conserved genetic context on an IncHI2 plasmid. Analysis of publicly available genomes from 47 countries demonstrated that blaNDM variants (primarily blaNDM-1 and blaNDM-5) and mcr-9 are widely distributed globally. Within the available dataset, the isolates exhibited high genetic diversity, with numerous sequence types (including high-risk clones ST171 and ST190) and plasmids (IncX3/IncHI2) implicated in their spread. The strains carried an average of 14 ARGseach, and phylogenetic analysis suggested potential for cross-border and cross-habitat transmission. Collectively, our findings underscore that E. hormaechei is not merely a pathogen but a highly adaptable genetic reservoir for ARG accumulation and dissemination, highlighting the urgent need for systematic One Health genomic surveillance.