Plant growth-promoting bacteria improve the Cd phytoremediation efficiency of soils contaminated with PE-Cd complex pollution by influencing the rhizosphere microbiome of sorghum

Composite pollution by microplastics and heavy metals poses a potential threat to the soilplant system and has received increasing attention. Plant growth-promoting bacteria (PGPB) have good application potential for the remediation of combined microplastic and heavy metal pollution, but few related studies exist. The present study employed a pot experiment to investigate the effects of inoculation with the PGPB Bacillus sp. SL-413 and Enterobacter sp. VY-1 on sorghum growth and Cd accumulation under conditions of combined cadmium (Cd) and polyethylene (PE) pollution. Cd+PE composite contamination led to a significant reduction in sorghum length and biomass due to increased toxicity. Inoculation with Bacillus sp. SL-413 and Enterobacter sp. VY-1 alleviated the stress caused by Cd+PE complex pollution, and the dry weight of sorghum increased by 25.7% to 46.1% aboveground and by 12.3% to 45.3% belowground. Bacillus sp. SL-413 and Enterobacter sp. VY-1 inoculation increased the Cd content and accumulation in sorghum and improved the phytoremediation efficiency of Cd. The inoculation treatment effectively alleviated the nutrient stress caused by the reduction in soil mineral nutrients due to Cd+PE composite pollution. The composition of the soil bacterial communities was also affected by the Cd, Cd+PE and bacterial inoculation treatments, which affected the diversity of the soil bacterial communities. Network analyses indicated that bacterial inoculation regulated the interaction of rhizospheric microorganisms and increased the stability of soil bacterial communities. The Mantel test showed that the changes in the soil bacterial community and function due to inoculation with Bacillus sp. SL-413 and Enterobacter sp. VY-1 were important factors influencing sorghum growth and Cd remediation efficiency. The results of this study will provide new evidence for the research on joint plantmicrobe remediation of heavy metal and microplastic composite pollution.

Statistical modelling, optimization, and mechanistic exploration of novel ureolytic Enterobacter hormaechei IITISM-SA3 in cadmium immobilization under microbial inclusive and cell-free conditions through microbially induced calcite precipitation

The study aimed to evaluate the potential of a novel isolated ureolytic Enterobacter hormaechei IITISM-SA3 in cadmium bioremoval through MICP. The optimization and modelling of the biotic and abiotic factors affecting the process of mineralization were also performed. In addition, the underlying mechanism of MICP-driven Cd mineralization under microbial-inclusive and cell-free conditions was revealed and supported through the characterization of the bio-precipitates obtained using various characterization techniques. The results indicated that the isolate could remove 97.18% Cd2+ of 11.4 ppm under optimized conditions of 36.86 h, pH 7.63, and biomass dose of 1.75 ml. Besides, the presence and absence of bacterial cells were found to influence both the morphologies and crystalline structures of precipitates. The precipitates obtained under microbial-inclusive conditions showed typical rhombohedral crystalline structures of the composition comprising CaCO3, CdCO3, and 0.67Ca0.33CdCO3. However, the crystalline nature of the precipitate reduced to a nano-sized granular structure in cell-free media. Unlike the cadmium mineralization process under microbial-inclusive media, where bacterial cells serve as nucleation sites for crystallization, the carbonate precipitation effectively captures Cd2+ through co-precipitation, chemisorption, or alternative mechanisms involving interactions between metal ions and CaCO3 under cell-free conditions. The findings presented suggest that using cell-free culture supernatant enriched with carbonate ions provides an avenue that could be harnessed for sustainable metal remediation.

A Multidrug-Resistant Extended-Spectrum Beta-Lactamase (ESBL)-Producing Enterobacter hormaechei Strain from Mixed Sprouts

Fresh vegetables can harbor antibiotic-resistant bacteria, including extended-spectrum β-lactamase (ESBL)-producing Enterobacterales. Enterobacter hormaechei is a bacterium belonging to the Enterobacterales order and the most commonly identified nosocomial pathogen of Enterobacter cloacae complex. The purpose of this study was to characterize a multi-drug resistant ESBL-producing E. hormaechei strain isolated from a sample of mixed sprouts. Vegetable samples were pre-enriched in buffered peptone water, followed by enrichment in Enterobacteria Enrichment Broth, and isolation on Chromagar™ ESBL plates. One isolate from a sprout sample was confirmed to produce both ESBL and AmpC β-lactamases through the combination disk diffusion assay using antibiotic disks containing cefotaxime and ceftazidime with or without clavulanate, and with or without cloxacillin, respectively. The isolate was also resistant to multiple antibiotics, including cefotaxime, ceftazidime, chloramphenicol, trimethoprim-sulfamethoxazole, tetracycline, gentamicin, ampicillin, and amoxicillin-clavulanate, as determined by antimicrobial susceptibility testing. Through whole genome sequencing, the isolate was identified as E. hormaechei 057-E1, which carried multiple antibiotic resistance (AR) genes and a sul2-aph(3″)-Ib-aph(6)-Id-blaTEM-1-ISEcp1 -blaCTX-M-15 gene cluster. Our results further demonstrate the important role of fresh vegetables in AR and highlight the need to develop strategies for AR mitigation in fresh vegetables.

xiangfangensis

Blood-borne infections caused by the carbapenem-resistant Enterobacter cloacae complex (CR-ECC) are major public threats with respect to the challenges encountered during treatment. This study describes the whole genome sequencing-based molecular characteristics of blood isolates (n = 70) of CR-ECC from patients admitted to the intensive care unit of tertiary care hospitals in Kolkata, India, during 2017-2022 with respect to species identification, antimicrobial resistance (AMR) profiling, mechanism of drug resistance, and molecular subtypes. Vitek2 MALDI and species-specific PCR identified Enterobacter hormaechei subsp. xiangfangensis (47.14%) as the emerging CR-ECC subspecies in Kolkata. The predominating carbapenemase and extended-spectrum β-lactamase genes found were blaNDM-1 (51.42%) and blaCTX-M-15 (27%), respectively. Besides, blaNDM-4, blaNDM-5, blaNDM-7, blaCMH-3, blaSFO-1, blaOXA-181, blaOXA-232, blaKPC-3, and blaDHA-7 genes were also detected, which were not previously reported from India. A multitude of Class 1 integrons (including In180, In4874, In4887, and In4888, which were novel) and plasmid replicon types (IncFIB, IncFII, IncX3, IncHI1-HI2, IncC, and IncR) involved in AMR dissemination were identified. Reverse transcription-PCR and western blot revealed that carbapenem resistance in non-carbapenemase-producing CR-ECC isolates was contributed by elevated levels of ampC, overexpression of acrAB, and loss of ompF. A total of 30 distinct sequence types (STs) were ascertained by multi-locus sequence typing; of which, ST2011, ST2018, ST2055, ST2721, and ST2722 were novel STs. Pulsed-field gel electrophoresis analysis showed heterogeneity (69 pulsotypes with a similarity coefficient of 48.40%) among the circulating isolates, suggesting multiple reservoirs of infections in humans. Phylogenetically and genetically diverse CR-ECC with multiple AMR mechanisms mandates close monitoring of nosocomial infections caused by these isolates to forestall the transmission and dissemination of AMR.IMPORTANCEThe emergence and extensive dissemination of the carbapenem-resistant Enterobacter cloacae complex (CR-ECC) have positioned it as a critical nosocomial global pathogen. The dearth of a comprehensive molecular study pertaining to CR-ECC necessitated this study, which is the first of its kind from India. Characterization of blood isolates of CR-ECC over the last 6 years revealed Enterobacter hormaechei subsp. xiangfangensis as the most prevalent subsp., exhibiting resistance to almost all antibiotics currently in use and harboring diverse transmissible carbapenemase genes. Besides the predominating blaNDM-1 and blaCTX-M-15, we document diverse carbapenemase and AmpC genes, such as blaNDM-4, blaNDM-7, blaOXA-181, blaOXA-232, blaKPC-3, blaCMH-3, blaSFO-1, and blaDHA-7, in CR-ECC, which were not previously reported from India. Furthermore, novel integrons and sequence types were identified. Our findings emphasize the need for strengthened vigilance for molecular epidemiological surveillance of CR-ECC due to the presence of epidemic clones with a phylogenetically diverse and wide array of antimicrobial resistance genes in vulnerable populations.

Antipathogenic Efficacy of Biogenic Silver Nanoparticles and Antibiofilm Activities Against Multi-drug-Resistant ESKAPE Pathogens

The silver nanoparticles (AgNPs) were produced by employing a biogenic loom and tested for antipathogenic assets against multi-drug-resistant (MDR) ESKAPE bacteria. Biogenically synthesized AgNPs were characterized adopting various high-throughput techniques such as UHRTEM, SEM with EDX, DLS, TGA-DTA, and XRD and spectroscopic analysis showed polydispersion of nanoparticles. In this context, AgNPs with the attribute of spherical-shaped nanoparticles with an average size of 26 nm were successfully synthesized utilizing bacterial supernatant. The antipathogenic activities of AgNPs were assessed against 11 strains of MDR ESKAPE bacteria including Enterococcus faecium; methicillin-resistant Staphylococcus aureus; Klebsiella pneumonia; Acinetobacter baumannii; Pseudomonas aeruginosa; Enterobacter aerogenes; and Enterobacter species. The exposure of biogenic AgNPs in a well diffusion assay showed all the growth inhibitions of ESKAPE bacteria at 200 μg/ml after 18 h of incubation. Growth kinetics demonstrated maximum killing at 60 μg/ml after 4 h of completion. The highest biofilm depletions were found at 100 μg/ml in adhesion assay. Live/dead assays showed effective killing of the ESKAPE bacteria at 10 μg/ml in pre-existing biofilms. The effective inhibitory concentrations of AgNPs were investigated ranging from 10 to 200 μg/ml. The selected pathogens found sensitive to AgNPs are statistically significant (P < 0.05) than that of cefotaxime/AgNO3. Consequently, a broad spectrum of antimicrobial potentials of AgNPs can be alternative to conventional antimicrobial agents for future medicine.

Genomic, functional, and metabolic enhancements in multidrug-resistant Enterobacter bugandensis facilitating its persistence and succession in the International Space Station

BACKGROUND

The International Space Station (ISS) stands as a testament to human achievement in space exploration. Despite its highly controlled environment, characterised by microgravity, increased CO2 levels, and elevated solar radiation, microorganisms occupy a unique niche. These microbial inhabitants play a significant role in influencing the health and well-being of astronauts on board. One microorganism of particular interest in our study is Enterobacter bugandensis, primarily found in clinical specimens including the human gastrointestinal tract, and also reported to possess pathogenic traits, leading to a plethora of infections.

RESULTS

Distinct from their Earth counterparts, ISS E. bugandensis strains have exhibited resistance mechanisms that categorise them within the ESKAPE pathogen group, a collection of pathogens recognised for their formidable resistance to antimicrobial treatments. During the 2-year Microbial Tracking 1 mission, 13 strains of multidrug-resistant E. bugandensis were isolated from various locations within the ISS. We have carried out a comprehensive study to understand the genomic intricacies of ISS-derived E. bugandensis in comparison to terrestrial strains, with a keen focus on those associated with clinical infections. We unravel the evolutionary trajectories of pivotal genes, especially those contributing to functional adaptations and potential antimicrobial resistance. A hypothesis central to our study was that the singular nature of the stresses of the space environment, distinct from any on Earth, could be driving these genomic adaptations. Extending our investigation, we meticulously mapped the prevalence and distribution of E. bugandensis across the ISS over time. This temporal analysis provided insights into the persistence, succession, and potential patterns of colonisation of E. bugandensis in space. Furthermore, by leveraging advanced analytical techniques, including metabolic modelling, we delved into the coexisting microbial communities alongside E. bugandensis in the ISS across multiple missions and spatial locations. This exploration revealed intricate microbial interactions, offering a window into the microbial ecosystem dynamics within the ISS.

CONCLUSIONS

Our comprehensive analysis illuminated not only the ways these interactions sculpt microbial diversity but also the factors that might contribute to the potential dominance and succession of E. bugandensis within the ISS environment. The implications of these findings are twofold. Firstly, they shed light on microbial behaviour, adaptation, and evolution in extreme, isolated environments. Secondly, they underscore the need for robust preventive measures, ensuring the health and safety of astronauts by mitigating risks associated with potential pathogenic threats. Video Abstract.

Enterobacter asburiae ST229: an emerging carbapenemases producer

Enterobacter asburiae, member of the Enterobacter cloacae complex (ECC) group, shows an increasing clinical relevance being responsible for infections like pneumonia, urinary tract infections and septicemia. The aim of the present study was the investigation of the genomic features of two XDR E. asburiae ST229 clinical strains co-carrying blaNDM-1 and blaVIM-1 determinants, collected in October 2021 and in June 2022, respectively. Two E. asburiae strains were collected from rectal swabs of as many patients admitted to the cardiopulmonary intensive care unit of Fondazione I.R.C.C.S. "Policlinico San Matteo" in Pavia, Italy. Based on the antibiotic susceptibility profile results, both isolates showed an XDR phenotype, retaining susceptibility only to fluoroquinolones. Both isolates shared identical resistome, virulome, plasmid content, and belonged to ST229, a rarely reported sequence type. They co-harbored blaNDM-1 and blaVIM-1 genes, that resulted located on transferable plasmids by conjugation and transformation. Moreover, both strains differed in 24 SNPs and showed genetic relatedness with E. asburiae ST709 and ST27. We described the first case of ST229 E. asburiae co-harboring blaNDM-1 and blaVIM-1 in Italy. This study points out the emergence of carbapenemases in low-risk pathogens, representing a novel challenge for public health, that should include such types of strains in dedicated surveillance programs. Antimicrobial susceptibility testing was carried out using Thermo Scientific™ Sensititre™ Gram Negative MIC Plates DKMGN. Both strains underwent whole-genome sequencing (WGS) using Illumina Miseq platform. Resistome, plasmidome, virulome, MLST, plasmid MLST and a SNPs-based phylogenetic tree were in silico determined.

Analysis of distinct blaKPC-encoding plasmids in an Enterobacter kobei strain recovered from recreational coastal water

In this study we present an in-depth characterization of two blaKPC-2 encoding plasmids found in the Enterobacter kobei FL23 strain recovered from recreational coastal water. The plasmids belong to distinct incompatibility groups and carry a diverse collection of resistance genes. Furthermore, the genetic context of the blaKPC-2 gene was different in each of them. While pEkFL23-IncX3 presents a new Tn4401k, a new isoform, similar to Tn4401b but with a truncated tnpA and a deleted tnpR; pEkFL23-IncU/P6 carries a new isoform of a non-Tn4401 element (NTEKPC), named NTEKPC-IIh. Its difference from NTEKPC-IId is the truncated Tn3 resolvase upstream blaKPC-2. Capacity of conjugation, maintenance rates and fitness cost of both replicons were also assessed. Both were transferred after mating assays, whereas only pEkFL23-IncX3 was transferred under the adverse conditions of Marine broth at 25 °C as a mating platform. A remarkable stability of both plasmids was observed in the parental and transconjugant strains. Finally, both replicons did not impose a significant fitness cost to their transformant hosts, with pEkFL23-IncU/P6 conferring a statistically significant (p < 0.05) advantage in head-to-head competitions. Our findings show that E. kobei FL23 is a disquieting case of a carbapenem-resistant bacteria identified in a community setting, being a possible silent disseminator of two seemingly stable and metabolic weightless multidrug resistance plasmids.

First report of blaOXA-181-carrying IncX3 plasmids in multidrug-resistant Enterobacter hormaechei and Serratia nevei recovered from canine and feline opportunistic infections

Whole-genome sequence analysis of six Enterobacter hormaechei and two Serratia nevei strains, using a hybrid assembly of Illumina and Oxford Nanopore Technologies sequencing, revealed the presence of the epidemic blaOXA-181-carrying IncX3 plasmids co-harboring qnrS1 and ∆ere(A) genes, as well as multiple multidrug resistance (MDR) plasmids disseminating in all strains, originated from dogs and cats in Thailand. The subspecies and sequence types (ST) of the E. hormaechei strains recovered from canine and feline opportunistic infections included E. hormaechei subsp. xiangfangensis ST171 (n = 3), ST121 (n = 1), and ST182 (n = 1), as well as E. hormaechei subsp. steigerwaltii ST65 (n = 1). Five of the six E. hormaechei strains harbored an identical 51,479-bp blaOXA-181-carrying IncX3 plasmid. However, the blaOXA-181 plasmid (pCUVET22-969.1) of the E. hormaechei strain CUVET22-969 presented a variation due to the insertion of ISKpn74 and ISSbo1 into the virB region. Additionally, the blaOXA-181 plasmids of S. nevei strains were nearly identical to the others at the nucleotide level, with ISEcl1 inserted upstream of the qnrS1 gene. The E. hormaechei and S. nevei lineages from canine and feline origins might acquire the epidemic blaOXA-181-carrying IncX3 and MDR plasmids, which are shared among Enterobacterales, contributing to the development of resistance. These findings suggest the spillover of significant OXA-181-encoding plasmids to these bacteria, causing severe opportunistic infections in dogs and cats in Thailand. Surveillance and effective hygienic practice, especially in hospitalized animals and veterinary hospitals, should be urgently implemented to prevent the spread of these plasmids in healthcare settings and communities.

IMPORTANCE

blaOXA-181 is a significant carbapenemase-encoding gene, usually associated with an epidemic IncX3 plasmid found in Enterobacterales worldwide. In this article, we revealed six carbapenemase-producing (CP) Enterobacter hormaechei and two CP Serratia nevei strains harboring blaOXA-181-carrying IncX3 and multidrug resistance plasmids recovered from dogs and cats in Thailand. The carriage of these plasmids can promote extensively drug-resistant properties, limiting antimicrobial treatment options in veterinary medicine. Since E. hormaechei and S. nevei harboring blaOXA-181-carrying IncX3 plasmids have not been previously reported in dogs and cats, our findings provide the first evidence of dissemination of the epidemic plasmids in these bacterial species isolated from animal origins. Pets in communities can serve as reservoirs of significant antimicrobial resistance determinants. This situation places a burden on antimicrobial treatment in small animal practice and poses a public health threat.

JIV1 assisted with putrescine

The detrimental impact of soil salinization on crop productivity and agricultural economy has garnered significant attention. A rhizosphere bacterium with favorable salt tolerance and plant growth-promoting (PGP) functions was isolated in this work. The bacterium was identified as Enterobacter through 16 S rDNA sequencing analysis and designated as Enterobacter sp. JIV1. Interestingly, the presence of putrescine (Put), which had been shown to contribute in reducing abiotic stress damage to plants, significantly promoted strain JIV1 to generate 1-aminocyclopropane-1-carboxylic (ACC) deaminase, dissolve phosphorus and secrete indole-3-acetic acid (IAA). However, the synergy of plant growth promoting rhizobacteria (PGPR) and Put in improving plant salt resistance has not been extensively studied. In this study, strain JIV1 and exogenous Put effectively mitigated the inhibitory impact of salt stress simulated by 200 mM NaCl on rice (Oryza sativa L.) growth. The chlorophyll accumulation, photosynthetic efficiency and antioxidant capacity of rice were also significantly strengthened. Notably, the combined application of strain JIV1 and Put outperformed individual treatments. Moreover, the co-addition of strain JIV1 and Put increased soil protease and urease activities by 451.97% and 51.70% compared to that of salt treatment group. In general, Put-assisted PGPR JIV1 provides a new perspective on alleviating the salt-induced negative impacts on plants.

Extensively drug-resistant Enterobacter ludwigii co-harbouring MCR-9 and a multicopy of blaIMP-1 in South Korea

In this study, we describe an Enterobacter ludwigii clinical isolate that is resistant to both carbapenems and colistin in South Korea. Antimicrobial susceptibility testing revealed that E. ludwigii CRE2104-31 was non-susceptible to all tested antibiotics except fosfomycin. Whole genome sequencing identified a 323-kbp IncHI2 plasmid, pCRE2104-31a, that was co-harbouring mobile colistin resistance (mcr)-9.1 and blaIMP-1. In comparison with other full plasmids, pCRE2104-31a exhibited the closest similarity to a plasmid from the Klebsiella pneumoniae strain CNR48 from France, with 19.9% query coverage and 99% identity. Notably, we observed five tandem repeats of blaIMP-1 and aac(6')-Il genes, accompanied by multiple attCs within a class I integron on the Tn402-like transposon. The unit of blaIMP-1-attC-aac(6')-Il-attC might have accumulated due to multiple convergent events. In addition to mcr-9.1 and blaIMP-1, various other antibiotic resistance-associated genes were identified in the plasmid, as follows: blaTEM-1B, aph(3')-I, aph(3')-Ia, aac(6')-Il, aac(6')-IIc, aac(6')-IIa, aph(6)-Id, aph(3'')-Ib, aadA2b, aac(6')-Ib3, sul, dfrA19, qnrB2, aac(6')-Ib-cr, ere(A), and qacE. A conjugation assay showed that the mcr-9.1/blaIMP-1-co-bearing plasmid was self-transmissible to E. coli J53. However, colistin and carbapenem resistance could not be transferred to E. coli due to high incompatibility. The convergence of mcr and carbapenemase genes is thought to be host-dependent among Enterobacteriaceae. The emergence of extensively drug-resistant E. ludwigii co-harbouring MCR-9.1 and a multicopy of blaIMP-1 would pose a significant threat within the compatible Enterobacteriaceae.

Phenotypic and genomic insights into the pathogenicity and antimicrobial resistance of an Enterobacter roggenkampii strain isolated from diseased silver arowana (Osteoglossum bicirrhosum)

Enterobacter roggenkampii is an opportunistic pathogen that causes infections in a wide range of hosts. A bacterial strain named EOBSR_19 was isolated from diseased silver arowana, Osteoglossum bicirrhosum. This bacterium was identified as E. roggenkampii based on the phenotypic characteristics and sequence analysis of the16S rDNA and gyrB genes. Average nucleotide identity and phylogenetic analysis based on the whole genome sequence further confirmed the bacterial taxonomy of EOBSR_19. Artificial experimental infection indicated that EOBSR_19 was pathogenic to fish. Antimicrobial susceptibility test showed it was multi-drug resistant. The EOBSR_19 was found to be resistant to 18 antibiotics belonging to quinolones, macrolides, sulfonamides, aminoglycosides, and β-lactams classes. The whole genome sequencing analysis showed that EOBSR_19 carried 730 virulence genes that were annotated for different functional modules, such as adhesion and invasion, secretion system, siderophore transport system and bacterial toxin. Among them, the virulence genes related to adhesion and invasion were the most abundant. In addition, drug resistance genes involved in multiple mechanisms of antimicrobial resistance were identified in its genomics, including multidrug resistance efflux pumps, antibiotic inactivating enzymes, and antibiotic binding site mutations. Its genomic analysis via whole-genome sequencing provided insights into the pathogenicity and antimicrobial resistance.

Biocontrol of Escherichia coli O157:H7 by Enterobacter asburiae AEB30 on intact cantaloupe melons

Escherichia coli O157:H7 causes >73,000 foodborne illnesses in the United States annually, many of which have been associated with fresh ready-to-eat produce including cantaloupe melons. In this study, we created a produce-associated bacterial (PAB) library containing >7500 isolates and screened them for the ability to inhibit the growth of E. coli O157:H7 using an in vitro fluorescence-based growth assay. One isolate, identified by 16S and whole-genome sequence analysis as Enterobacter asburiae, was able to inhibit the growth of E. coli by ~30-fold in vitro and produced zones of inhibition between 13 and 21 mm against 12 E. coli outbreak strains in an agar spot assay. We demonstrated that E. asburiae AEB30 was able to grow, persist and inhibit the growth of E. coli on cantaloupe melons under simulated pre- and post-harvest conditions. Analysis of the E. asburiae AEB30 genome revealed an operon encoding a contact-dependent growth inhibition (CDI) system that when mutated resulted in the loss of E. coli growth inhibition. These data suggest that E. asburiae AEB30 is a potential biocontrol agent to prevent E. coli contamination of cantaloupe melons in both pre- and post-harvest environments and that its mode of action is via a CDI system.

Antagonistic effect of the beneficial bacterium Enterobacter hormaechei against the heavy metal Cu2+ in housefly larvae

Vermicomposting via housefly larvae can be used to efficiently treat manure and regenerate biofertilizer; however, the uptake of heavy metals could negatively influence the growth and development of larvae. Intestinal bacteria play an important role in the development of houseflies, but their effects on resistance to heavy metal damage in houseflies are still poorly understood. In this study, the life history traits and gut microbiota of housefly larvae were evaluated after exposure to an environment with Cu2+ -Enterobacter hormaechei. The data showed that exposure to 300 μg/mL Cu2+ significantly inhibited larval development and locomotor activity and reduced immune capacity. However, dietary supplementation with a Cu2+ -Enterobacter hormaechei mixture resulted in increased body weight and length, and the immune capacity of the larvae returned to normal levels. The abundances of Providencia and Klebsiella increased when larvae were fed Cu2+ -contaminated diets, while the abundances of Enterobacter and Bacillus increased when larvae were exposed to a Cu2+ -Enterobacter hormaechei mixture-contaminated environment. In vitro scanning electron microscopy analysis revealed that Enterobacter hormaechei exhibited obvious adsorption of Cu2+ when cultured in the presence of Cu2+, which reduced the damage caused by Cu2+ to other bacteria in the intestine and protected the larvae from Cu2+ injury. Overall, our results showed that Enterobacter hormaechei can absorb Cu2+ and increase the abundance of beneficial bacteria, thus protecting housefly larvae from damage caused by Cu2+. These results may fill the gaps in our understanding of the interactions between heavy metals and beneficial intestinal bacteria, offering valuable insights into the interplay between housefly larvae and metal contaminants in the environment. This approach could enhance the efficiency of converting manure contaminated with heavy metals to resources using houseflies.

Exploitation of Enterobacter hormaechei for biodegradation of multiple plastics

The escalating problem of environmental ecological pollution caused by plastics presents a significant challenge, which makes the management of plastic waste urgent nowadays. In this study, a bacterium named WX-2 was isolated and screened for its potential in polymer degradation. Through standard microbiological techniques and 16SrDNA gene sequencing, it was identified as Enterobacter hormaechei. To assess its biodegradability potential, various plastics including High density polyethylene, Polypropylene, Linear low density polyethylene, Poly (butyleneadipate-co-terephthalate) and Polyvinyl chloride were subjected to the study. The biodegradability of the plastics was evaluated using multiphase approaches involving techniques such as Scanning electron microscopy, Fourier transform infrared spectroscopy, Mass loss, X-ray diffraction, X-ray photoelectron spectroscopy, Water contact angle, and Gas chromatography-mass spectrometry. Results indicated that WX-2 possesses the capability to utilize diverse plastic polymers as sole carbon sources, displaying distinct biodegradation capacities. Notably, PBAT exhibited heightened susceptibility to degradation by the screened bacterial population.

Disease suppression, growth promotion and colonization attributes of resident endophytic bacteria against white root rot (Dematophora necatrix Hartig) of apple

The inherent potential of apple plants was investigated to explore bacterial endophytes and their role in suppressing Dematophora necatrix, the causative pathogen of white root rot disease. Resultantly 34 endophytic bacteria isolated from healthy apple plants, and subsequently 6 most efficient isolates viz., Bacillus megaterium strain EA3, Enterobacter sp. strain EA7, Bacillus megaterium strain EK2, Stenotrophomonas maltophilia strain EK6, Acinetobacter nosocomialis strain ES2 and Pseudomonas aeruginosa strain ES8 depicting anti-pathogen interactions through preliminary screening were assessed further under in vitro, glasshouse and field conditions against white root rot pathogen/disease. Maximum mycelial growth inhibition (80.37%) was obtained with S. maltophilia strain EK6 encouraging for its seed treatment and soil application thereby providing significant effective control (87.91%) of white root rot under glasshouse conditions to other five bacterial endophytes evaluated simultaneously, followed by field efficacy of 83.70%. In addition, it has significantly enhanced the growth parameters of apple trees under both glasshouse and field conditions. The inoculated healthy plants were assessed for endophytic colonization which revealed maximum endosphere colonialism by S. maltophilia strain EK6. Additionally, confocal microscopic images of transverse sections of root cells colonized by bacterial endophytes as compared to untreated control implied their persistence and establishment in endosphere of apple seedlings. The study provides the first report on interaction between apple associated bacterial root endophytes and D. necatrix. The obtained endophytic strains could be employed as alternative for mitigating white root rot disease in future.

Analysis of gut microbiota of ladybug beetle (Harmonia axyridis) after feeding on different artificial diets

BACKGROUND

Harmonia axyridis is an effective natural enemy insect to a variety of phloem-sucking pests and Lepidopteran larvae, such as aphids, scabies, and phylloxera, while its industrial production is limited due to unmature artificial diet. Insect intestinal microbiota affect host development and reproduction. The aim of this study is to understand intestinal microbiota composition of H. axyridis and screen effective probiotics on artificial diet. Considering the role of the components and composition of the diet on the structure and composition of the intestinal microbiome, four kinds of diets were set up: (1) aphid; (2) basic diet; (3) basic diet + glucose; (4) basic diet + trehalose. The gut microbiota of H. axyridis was detected after feeding on different diets.

RESULTS

Results showed that the gut microbiota between artificial diet group and aphid groups were far apart, while the basic and glucose groups were clearly clustered. Besides, the glucose group and trehalose group had one unique phylum, Cryptophyta and Candidatus Saccharibacteria, respectively. The highest abundance of Proteobacteria was found in the aphid diet. The highest abundance of Firmicutes was found in the basic diet. However, the addition of glucose or trehalose alleviated the change. In addition, the relative abundance of Enterobacter, Klebsiella, Enterobacteriaceae_unclassified, Enterobacteriales_unclassified and Serratia in the aphid group was higher than other groups. Moreover, the function of gut genes in each group also showed clear differences.

CONCLUSION

These results have offered a strong link between artificial diets and gut microbes, and also have provided a theoretical basis for the screening of synergistic probiotics in artificial diet.

Epidemiology of Enterococcus , Staphylococcus aureus , Klebsiella , Acinetobacter , Pseudomonas , and Enterobacter Species Transmission in the Pediatric Anesthesia Work Area Environment With and Without Practitioner Use of a Personalized Body-Worn Alcohol Dispenser

BACKGROUND

Personalized body-worn alcohol dispensers may serve as an important tool for perioperative infection control, but the impact of these devices on the epidemiology of transmission of high-risk Enterococcus , Staphylococcus aureus , Klebsiella, Acinetobacter , Pseudomonas , and Enterobacter (ESKAPE) pathogens is unknown. We aimed to characterize the epidemiology of ESKAPE transmission in the pediatric anesthesia work area environment with and without a personalized body-worn alcohol dispenser.

METHODS

This controlled before and after study included 40 pediatric patients enrolled over a 1-year study period. Two groups of operating room cases were compared: (1) operating room cases caring for patients with usual care (December 17, 2019, to August 25, 2020), and (2) operating room cases caring for patients with usual care plus the addition of a personalized, body-worn alcohol hand rub dispenser (September 30, 2020, to December 16, 2020). Operating rooms were randomly selected for observation of ESKAPE transmission in both groups. Device use was tracked via wireless technology and recorded in hourly hand decontamination events.

RESULTS

Anesthesia providers used the alcohol dispenser 3.3 ± 2.1 times per hour. A total of 57 ESKAPE transmission events (29 treatment and 28 control) were identified. The personalized body-worn alcohol dispenser impacted ESKAPE transmission by increasing the contribution of provider hand contamination at case start (21/29 device versus 10/28 usual care; relative risk, [RR] 2.03; 99.17% confidence interval [CI], 1.025-5.27; P = .0066) and decreasing the contribution of environmental contamination at case end (3/29 device versus 12/28 usual care; RR, 0.24; 99.17% CI, 0.022-0.947; P = .0059). ESKAPE pathogen contamination involved 20% (8/40) of patient intravascular devices. There were 85% (34/40) of preoperative patient skin surfaces contaminated with ≥1 (1.78 ± 0.19 [standard deviation {SD}]) ESKAPE pathogens.

CONCLUSIONS

A personalized body-worn alcohol dispenser can impact the epidemiology of ESKAPE transmission in the pediatric anesthesia work area environment. Improved preoperative patient decolonization and vascular care are indicated to address ESKAPE pathogens among pediatric anesthesia work area reservoirs.

N1-10 and remediation of uranium-contaminated soil

Uranium (U) pollution in soils is prevalent worldwide and poses a significant health risk that will require remediation approaches. However, traditional U bioreduction by sulfate reducing bacteria (SRB) are sensitive to oxygen and are not suitable for treating aerobic topsoil. Bioprecipitation of U into uranyl phosphate (UP) mediated by phosphate-solubilizing microorganism (PSM) is not affected by oxygen. In this study, PSM strains were isolated and used for U-contaminated soil remediation. Microbial metabolites and the mechanism of PSM bioprecipitation were revealed. The results showed that strain Enterobacter sp. N1-10 had the highest phosphate-solubilizing capacity (dissolved P was 409.51 ± 8.48 mg/L). Uranium bioprecipitation was investigated by culturing the bacterium in the presence of 50 mg/L U and in the cell-free culture supernatant. The results showed that strain N1-10 had a high U removal rate (99.45 ± 0.43 %) after adding 50 mg/L U to the culture medium. A yellow precipitate was immediately formed when uranyl nitrate solution was added to the cell-free culture supernatant. The analysis indicated that bacterium produced lactic acid (37.58 mg/L), citric acid (4.76 mg/L), succinic acid (2.03 mg/L), and D-glucuronic acid (1.94 mg/L); the four organic acids solubilized Ca3(PO4)2 to form stable uranyl phosphate precipitate. The application of strain N1-10 and Ca3(PO4)2 significantly decreased the bioavailability of soil U (43.54 ± 0.52 %). In addition, pot experiments showed that PSM N1-10 and Ca3(PO4)2 promoted plant growth and markedly reduced U accumulation by pakchoi. These results demonstrate that PSM N1-10 and Ca3(PO4)2 exhibit a great potential for U bioremediation.

Rocket-miR, a translational launchpad for miRNA-based antimicrobial drug development

IMPORTANCE

Antimicrobial-resistant infections contribute to millions of deaths worldwide every year. In particular, the group of bacteria collectively known as ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter sp.) pathogens are of considerable medical concern due to their virulence and exceptional ability to develop antibiotic resistance. New kinds of antimicrobial therapies are urgently needed to treat patients for whom existing antibiotics are ineffective. The Rocket-miR application predicts targets of human miRNAs in bacterial and fungal pathogens, rapidly identifying candidate miRNA-based antimicrobials. The application's target audience are microbiologists that have the laboratory resources to test the application's predictions. The Rocket-miR application currently supports 24 recognized human pathogens that are relevant to numerous diseases including cystic fibrosis, chronic obstructive pulmonary disease (COPD), urinary tract infections, and pneumonia. Furthermore, the application code was designed to be easily extendible to other human pathogens that commonly cause hospital-acquired infections.

Maternal transmission of bacterial microbiota during embryonic development in a viviparous lizard

IMPORTANCE

We investigated the presence and diversity of bacteria in the embryos of the viviparous lizard Sceloporus grammicus and their amniotic environment. We compared this diversity to that found in the maternal intestine, mouth, and cloaca. We detected bacterial DNA in the embryos, albeit with a lower bacterial species diversity than found in maternal tissues. Most of the bacterial species detected in the embryos were also found in the mother, although not all of them. Interestingly, we detected a high similarity in the composition of bacterial species among embryos from different mothers. These findings suggest that there may be a mechanism controlling the transmission of bacteria from the mother to the embryo. Our results highlight the possibility that the interaction between maternal bacteria and the embryo may affect the development of the lizards.

[Effect of Combined Application of an Enterobacter and Sulfur Fertilizer on Cadmium and Arsenic Accumulation in Rice]

The aim of this study was to explore the effects of different sulfur fertilizers combined with sulfate-reducing bacteria on the accumulation of cadmium and arsenic in rice and the formation of iron plaque under long-term flooding conditions and to provide a reference for the safe production of rice fields polluted by moderate and mild cadmium and arsenic. We adopted a pot experiment, selecting two sulfur fertilizers, sulfur and calcium sulfate, and Enterobacter M5 with sulfate-reducing ability, and designed six treatments of single application and combined application of different sulfur fertilizers and M5. The results showed that the combined application of calcium sulfate and M5(CM5) had the best effect on reducing available cadmium and arsenic in rice rhizosphere soil. The combined application of sulfur fertilizer or M5 could reduce the content of cadmium and inorganic arsenic in early season rice grains by 8%-51% and 42%-61%, respectively, under flooding conditions. The content of cadmium and inorganic arsenic in late rice grains decreased by 81%-92% and 41%-62%, respectively. The treatment of the combined application of sulfur and M5(SM5) and CM5 had the best effect on reducing cadmium and arsenic content in both early and late season rice grains. SM5 and CM5 could promote the adsorption of cadmium and arsenic by iron plaque, and the extracted cadmium and arsenic content of ACA in both treatments was significantly higher than that of CK. The extracted iron content of ACA in the CM5 treatment was also significantly higher than that of CK, which indicates that the combined application of calcium sulfate and M5 would promote the formation of iron plaque. The results showed that the combined application of sulfur fertilizer and M5 was better than single application in reducing the content of cadmium and arsenic in grains, whereas the combined application of calcium sulfate and M5 was the best and most stable method.

Bioremediation of industrial wastewater heavy metals using solo and consortium Enterobacter spp

Heavy metals are considered the most common pollutants in industrial wastewater areas. Out of thirty bacterial isolates, only 3 isolates sighted the highest metal resistance activity for Zn+2, Fe+2, Pb+2, Co+2, Mn+2, Ni+2, and Cd+2. The biochemical and DNA homology identification with similarities 99.58%, 99.79%, and 99.86% of those isolates was identified and deposited in WDCM, respectively, as Enterobacter kobei OM144907 SCUF0000311, Enterobacter cloacae OM180597 SCUF0000312, and Enterobacter hormaechei OM181067 SCUF0000313. The minimum tolerance activity (MIC) of heavy metal concentrations against E. kobei and E. cloacae was 25, 15, and 15 mmol/l for Ni+2, Fe+2, and Mn+2, respectively, and 10 mmol/l for Zn+2, Pb+2, Co+2, and Cd+2, while against E. hormaechei, it is 15 mmol/l for Ni+2, Fe+2, and Mn+2 and 10 mmol/l for Zn+2, Pb+2, Co+2, and Cd+2. The consortium and solitary application of bacterial isolates towards heavy metal removal at 100%, 200%, and 300% industrial wastewater concentrations were conducted and showed that more than 90% removal of Zn+2, Fe+2, Pb+2, Mn+2, Ni+2, and Cd+2 from a non-concentrated polluted sample (100%) was reported by the three strains. With doubling the polluted sample concentration (200%), the highest removal efficiency for Zn+2, Pb+2, Mn+2, Ni+2, and Cd+2 was reported by E. cloacae as 70. 75, 66, 65, and 57%, respectively. Removal efficiency after increasing the polluted sample concentration to 300% showed that E. cloacae removed above 45% of all tested heavy metals except Pb+2. Ultimately, E. cloacae exposed the highest efficiency with recommendations for heavy metals removal under higher concentrations.

isolated from the rhizosphere of Vachellia gummifera in Morocco

The Moroccan endemic Vachellia gummifera grows wild under extreme desert conditions. This plant could be used as an alternative fodder for goats, and camels, in order to protect the Argan forests against overgrazing in Central and Southwestern Moroccan semiarid areas. With the aim to improve the V. gummifera population's density in semiarid areas, we proposed its inoculation with performing plant growth-promoting bacteria. Hence, 500 bacteria were isolated from the plant rhizosphere. From these, 291 isolates were retained for plant growth-promoting (PGP) activities assessment. A total of 44 isolates showed the best phosphates solubilization potential, as well as siderophore and auxin production. The combination of REP-PCR (repetitive extragenic palindromic-polymerase chain reaction) fingerprinting, PGP activities, and phenotypic properties, allowed the selection of three strains for the inoculation experiments. The three selected strains' 16S rRNA sequencing showed that they are members of the Enterobacter and Pseudomonas genera. The inoculation with three strains had diverse effects on V. gummifera growth parameters. All single and combined inoculations improved the plant shoot weight by more than 200%, and the root length by up to 139%, while some combinations further improved protein and chlorophyll content, thereby improving the plant's forage value. The three selected strains constitute an effective inoculum for use in the arid and semiarid zones of southern Morocco.

Polystyrene microplastics biodegradation by gut bacterial Enterobacter hormaechei from mealworms under anaerobic conditions: Anaerobic oxidation and depolymerization

Synthetic plastic is used throughout daily life and industry, threatening organisms with microplastic pollution. Polystyrene is a major plastic polymer and also widely found sources of plastic wastes and microplastics. Here, we report that Enterobacter hormaechei LG3 (CP118279.1), a facultative anaerobic bacterial strain isolated from the gut of Tenebrio molitor larvae (mealworms) can oxidize and depolymerize polystyrene under anaerobic conditions. LG3 performed biodegradation while forming a biofilm on the plastic surface. PS biodegradation was characterized by analyses of surface oxidation, change in morphology and molecular weights, and production of biodegraded derivative. The biodegradation performance by LG3 was compared with PS biodegradation by Bacillus amyloliquefaciens SCGB1 under both anaerobic and aerobic conditions. In addition, through nanopore sequencing technology, we identified degradative enzymes, including thiol peroxidase (tpx), alkyl hydroperoxide reductase C (ahpC) and bacterioferritin comigratory protein (bcp). Along with the upregulation of degradative enzymes for biodegradation, changes in lipid A and biofilm-associated proteins were also observed after the cells were incubated with polystyrene microplastics. Our results provide evidence for anaerobic biodegradation by polystyrene-degrading bacteria and show alterations in gene expression patterns after polystyrene microplastics treatment in the opportunistic pathogen Enterobacter hormaechei.

TY-1

Although studies on immobilized microorganisms have been conducted, their performance remains unclear for enhancing plants to remediate cadmium (Cd)-contaminated soil. In this study, a Cd-resistant strain TY-1 with good plant growth promotion traits was immobilized by biochar (BC) or oyster shell (OS) power to strengthen ryegrass to remediate Cd-contaminated soil. SEM-EDS combined with FTIR showed that TY-1 could tolerate Cd toxicity by surface precipitation, and functional groups such as hydroxyl and carbonyl groups might be involved. In the biocomposite treatments, soil pH increased, and the activity of fertility-related enzymes such as dehydrogenase increased by 109.01%-128.01%. The relative abundance of genus Saccharimonadales decreased from 7.97% to 3.35% in BS-TY and 2.61% in OS-TY, respectively. Thus, a suitable environment for ryegrass growth was created. The fresh weight, dry weight, plant height and Cd accumulation of ryegrass in TY treatment increased by 122.92%, 114.81%, 42.08% and 8.05%, respectively, compared to the control. Cd concentration in ryegrass was further increased in BC-TY and OS-TY by 24.14% and 40.23%, respectively. The improvement in soil microcosm and plant biomass forms an ongoing virtuous cycle, demonstrating that using carrier materials to improve the efficiency of microbial-assisted phytoremediation is realistic and feasible.

Characterizing the type 6 secretion system (T6SS) of E. cloacae SBP-8 and its role in pathogenesis and bacterial competition

Despite the relevance of E. cloacae as an opportunistic pathogen, very little is known about its pathogenicity mechanism and the factors influencing its virulence. The mechanism of E. cloacae pathogenicity appears to be complex and multifactorial, with the presence of different putative virulence factors whose role is still not clear in the development of the disease. In this study, we systematically investigated the role of T6SS (type six secretion system) of E. cloacae SBP-8, an environmental isolate, in eukaryotic and bacterial cell interaction. Analysis of the genome sequence of E. cloacae SBP-8 revealed the presence of sets of genes coding for the expression of one complete T6SS cluster, which is similar to T6SS-1 cluster of E. cloacae ATCC 13047 (clinical isolates). In addition, an Hcp effector protein was detected in the secretome, and this secretion depended on ClpV, an Atpase of T6SS, confirming that strain SBP-8 produces functional T6SS. Deletion of T6SS-associated gene clpV did not induce any significant change in the life span and rate of colonization in C. elegans. No major significant change was observed in the expression profiling of antimicrobial genes (clec-60, clec-85, clec-87 and lys-1) and toll-like receptor (toll-1) gene, involved in stimulating an immune response against the pathogen. No difference in the ability to invade and proliferate in intestinal cells and phagocytosis by macrophages was observed. In addition, we demonstrated that the ability of E. cloacae SBP-8 to out-compete Escherichia coli was reliant upon its T6SS in contact-dependent manner. Our results show that T6SS of the environmental isolates is required for interbacterial competition but not for invasion and proliferation inside host cells.

Antibiofilm potential of gallic acid against Klebsiella pneumoniae and Enterobacter hormaechei: in-vitro and in-silico analysis

Biofilm refers to a community of microorganisms that adhere to a substrate and play a crucial role in microbial pathogenesis and developing infections associated with medical devices. Enterobacter hormaechei and Klebsiella pneumoniae are classified as significant nosocomial pathogens within the ESKAPE category and cause diverse infections. In addition to their reputation as prolific biofilm formers, these pathogens are increasingly becoming drug-resistant and pose a substantial threat to the healthcare setting. Due to the inherent resistance of biofilms to conventional therapies, novel strategies are imperative for effectively controlling E. hormaechei and K. pneumoniae biofilms. This study aimed to assess the anti-biofilm activity of gallic acid (GA) against E. hormaechei and K. pneumoniae. The results of biofilm quantification assays demonstrated that GA exhibited significant antibiofilm activity against E. hormaechei and K. pneumoniae at concentrations of 4 mg mL-1, 2 mg mL-1, 1 mg mL-1, and 0.5 mg mL-1. Similarly, GA exhibited a dose-dependent reduction in violacein production, a QS-regulated purple pigment, indicating its ability to suppress violacein production and disrupt QS mechanisms in Chromobacterium violaceum. Additionally, computational tools were utilized to identify the potential target involved in the biofilm formation pathway. The computational analysis further indicated the strong binding affinity of GA to essential biofilm regulators, MrkH and LuxS, suggesting its potential in targeting the c-di-GMP and quorum sensing (QS) pathways to hinder biofilm formation in K. pneumoniae. These compelling findings strongly advocate GA as a promising drug candidate against biofilm-associated infections caused by E. hormaechei and K. pneumoniae.

Inoculating moldavian balm (Dracocephalum moldavica L.) with mycorrhizal fungi and bacteria may mitigate the adverse effects of water stress

Plant growth-promoting bacteria (PGPBs) play a crucial role in mitigating the oxidative damage caused by water stress in different plant species. The aim of this study was to determine the effects of PGPBs and mycorrhiza-like fungi (Piriformospora indica) on improving drought tolerance in moldavian balm (Dracocephalum moldavica L.), a medicinal and aromatic plant. For this purpose, a greenhouse study was conducted in a factorial experiment based on a randomized complete design with three replications. Results indicate that water stress reduces the membrane stability index (MSI), total chlorophyll content (Chlt), carotenoids, and maximum photochemical efficiency of photosystem II (Fv'/Fm') in moldavian balm plants, while increasing superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and hydrogen peroxide (H2O2) content compared to the control (no water stress). Inoculation with PGPBs and Piriformospora indica helped alleviate the negative effects of water stress. The highest MSI (48%) and Fv'/Fm' value (0.82) were observed when inoculated with Enterobacter and Piriformospora, respectively, under non-water-stressed conditions. Inoculation with Agrobacterium, Piriformospora, and Enterobacter improved the Chlt and leaf proline contents, as well as the SOD activity under high water stress, compared to the non-inoculated control values. Furthermore, inoculation with Pseudomonas under high water deficit stress levels increased the MDA content (0.51 mmol g-1 FW) and H2O2 levels (0.40 mmol g-1 FW). The highest yield of flowering branches (2.414 g pot-1) in moldavian balm was obtained with Enterobacter. Based on the enhanced physiological and biochemical responses, as well as increased antioxidant enzyme activity that improve water tolerance in this plant, it is recommended to use PGPBs and Piriformospora indica fertilization.

Biochemical and metabolic signatures are fundamental to drought adaptation in PGPR Enterobacter bugandensis WRS7

Drought alone causes more annual loss in crop yield than the sum of all other environmental stresses. There is growing interest in harnessing the potential of stress-resilient PGPR in conferring plant resistance and enhancing crop productivity in drought-affected agroecosystems. A detailed understanding of the complex physiological and biochemical responses will open up the avenues to stress adaptation mechanisms of PGPR communities under drought. It will pave the way for rhizosphere engineering through metabolically engineered PGPR. Therefore, to reveal the physiological and metabolic networks in response to drought-mediated osmotic stress, we performed biochemical analyses and applied untargeted metabolomics to investigate the stress adaptation mechanisms of a PGPR Enterobacter bugendensis WRS7 (Eb WRS7). Drought caused oxidative stress and resulted in slower growth rates in Eb WRS7. However, Eb WRS7 could tolerate drought stress and did not show changes in cell morphology under stress conditions. Overproduction of ROS caused lipid peroxidation (increment in MDA) and eventually activated antioxidant systems and cell signalling cascades, which led to the accumulation of ions (Na+, K+, and Ca2+), osmolytes (proline, exopolysaccharides, betaine, and trehalose), and modulated lipid dynamics of the plasma membranes for osmosensing and osmoregulation, suggesting an osmotic stress adaption mechanism in PGPR Eb WRS7. Finally, GC-MS-based metabolite profiling and deregulated metabolic responses highlighted the role of osmolytes, ions, and intracellular metabolites in regulating Eb WRS7 metabolism. Our results suggest that understanding the role of metabolites and metabolic pathways can be exploited for future metabolic engineering of PGPR and developing bio inoculants for plant growth promotion under drought-affected agroecosystems.

Going Beyond Host Defence Peptides: Horizons of Chemically Engineered Peptides for Multidrug-Resistant Bacteria

Multidrug-resistant (MDR) bacteria are considered a health threat worldwide, and this problem is set to increase over the decades. The ESKAPE, a group of six pathogens including Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp. is the major source of concern due to their high death incidence and nosocomial acquired infection. Host defence peptides (HDPs) are a class of ribosomally synthesised peptides that have shown promising results in combating MDR, including the ESKAPE group, in- and outside bacterial biofilms. However, their poor pharmacokinetics in physiological mediums may impede HDPs from becoming viable clinical candidates. To circumvent this problem, chemical engineering of HDPs has been seen as an emergent approach to not only improve their pharmacokinetics but also their efficacy against pathogens. In this review, we explore several chemical modifications of HDPs that have shown promising results, especially against ESKAPE pathogens, and provide an overview of the current findings with respect to each modification.

Treatment of antibiotic-resistant bacteria colonizing diabetic foot ulcers by OLED induced antimicrobial photodynamic therapy

We evaluate the efficacy of antimicrobial Photodynamic Therapy (APDT) for inactivating a variety of antibiotic-resistant clinical strains from diabetic foot ulcers. Here we are focused on APDT based on organic light-emitting diodes (OLED). The wound swabs from ten patients diagnosed with diabetic foot ulcers were collected and 32 clinical strains comprising 22 bacterial species were obtained. The isolated strains were identified with the use of mass spectrometry coupled with a protein profile database and tested for antibiotic susceptibility. 74% of isolated bacterial strains exhibited adaptive antibiotic resistance to at least one antibiotic. All strains were subjected to the APDT procedure using an OLED as a light source and 16 µM methylene blue as a photosensitizer. APDT using the OLED led to a large reduction in all cases. For pathogenic bacteria, the reduction ranged from 1.1-log to > 8 log (Klebsiella aerogenes, Enterobacter cloaca, Staphylococcus hominis) even for high antibiotic resistance (MRSA 5-log reduction). Opportunistic bacteria showed a range from 0.4-log reduction for Citrobacter koseri to > 8 log reduction for Kocuria rhizophila. These results show that OLED-driven APDT is effective against pathogens and opportunistic bacteria regardless of drug resistance.

E1 increased arsenic uptake in Pteris vittata by promoting plant growth and dissolving Fe-bound arsenic

Microbes affect arsenic accumulation in the arsenic-hyperaccumulator Pteris vittata, but the associated molecular mechanism remains uncertain. Here, we investigated the effect of Enterobacter sp. E1 on arsenic accumulation by P. vittata. Strain E1 presented capacities of arsenate [As(V)] and Fe(III) reduction during cultivation. In the pot experiment with P. vittata, the biomass, arsenic content, and chlorophyll content of P. vittata significantly increased by 30.03%, 74.9%, and 112.1%, respectively. Strikingly, the water-soluble plus exchangeable arsenic (WE-As) significantly increased by 52.05%, while Fe-bound arsenic (Fe-As) decreased by 29.64% in the potted soil treated with strain E1. The possible role of activation of arsenic by strain E1 was subsequently investigated by exposing As(V)-absorbed ferrihydrite to the bacterial culture. Speciation analyses of As showed that strain E1 significantly increased soluble levels of As and Fe and that more As(V) was reduced to arsenite. Additionally, increased microbial diversity and soil enzymatic activities in soils indicated that strain E1 posed few ecological risks. These results indicate that strain E1 effectively increased As accumulation in P. vittata mainly by promoting plant growth and dissolving soil arsenic. Our findings suggest that As(V) and Fe(III)-reducer E1 could be used to enhance the phytoremediation of P. vittata in arsenic-contaminated soils.

In Vitro Persistence Level Reflects In Vivo Antibiotic Survival of Natural Pseudomonas aeruginosa Isolates in a Murine Lung Infection Model

Clinicians are increasingly confronted with the limitations of antibiotics to clear bacterial infections in patients. It has long been assumed that only antibiotic resistance plays a pivotal role in this phenomenon. Indeed, the worldwide emergence of antibiotic resistance is considered one of the major health threats of the 21st century. However, the presence of persister cells also has a significant influence on treatment outcomes. These antibiotic-tolerant cells are present in every bacterial population and are the result of the phenotypic switching of normal, antibiotic-sensitive cells. Persister cells complicate current antibiotic therapies and contribute to the development of resistance. In the past, extensive research has been performed to investigate persistence in laboratory settings; however, antibiotic tolerance under conditions that mimic the clinical setting remain poorly understood. In this study, we optimized a mouse model for lung infections with the opportunistic pathogen Pseudomonas aeruginosa. In this model, mice are intratracheally infected with P. aeruginosa embedded in seaweed alginate beads and subsequently treated with tobramycin via nasal droplets. A diverse panel of 18 P. aeruginosa strains originating from environmental, human, and animal clinical sources was selected to assess survival in the animal model. Survival levels were positively correlated with the survival levels determined via time-kill assays, a common method to study persistence in the laboratory. We showed that survival levels are comparable and thus that the classical persister assays are indicative of antibiotic tolerance in a clinical setting. The optimized animal model also enables us to test potential antipersister therapies and study persistence in relevant settings. IMPORTANCE The importance of targeting persister cells in antibiotic therapies is becoming more evident, as these antibiotic-tolerant cells underlie relapsing infections and resistance development. Here, we studied persistence in a clinically relevant pathogen, Pseudomonas aeruginosa. It is one of the six ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, P. aeruginosa, and Enterobacter spp.), which are considered major health threats. P. aeruginosa is mostly known to cause chronic lung infections in cystic fibrosis patients. We mimicked these lung infections in a mouse model to study persistence under more clinical conditions. It was shown that the survival levels of natural P. aeruginosa isolates in this model are positively correlated with the survival levels measured in classical persistence assays in vitro. These results not only validate the use of our current techniques to study persistence but also open opportunities to study new persistence mechanisms or evaluate new antipersister strategies in vivo.

Source-tracking ESBL-producing bacteria at the maternity ward of Mulago hospital, Uganda

INTRODUCTION

Escherichia coli, Klebsiella pneumoniae and Enterobacter (EKE) are the leading cause of mortality and morbidity in neonates in Africa. The management of EKE infections remains challenging given the global emergence of carbapenem resistance in Gram-negative bacteria. This study aimed to investigate the source of EKE organisms for neonates in the maternity environment of a national referral hospital in Uganda, by examining the phenotypic and molecular characteristics of isolates from mothers, neonates, and maternity ward.

METHODS

From August 2015 to August 2016, we conducted a cross-sectional study of pregnant women admitted for elective surgical delivery at Mulago hospital in Kampala, Uganda; we sampled (nose, armpit, groin) 137 pregnant women and their newborns (n = 137), as well as health workers (n = 67) and inanimate objects (n = 70 -beds, ventilator tubes, sinks, toilets, door-handles) in the maternity ward. Samples (swabs) were cultured for growth of EKE bacteria and isolates phenotypically/molecularly investigated for antibiotic sensitivity, as well as β-lactamase and carbapenemase activity. To infer relationships among the EKE isolates, spatial cluster analysis of phenotypic and genotypic susceptibility characteristics was done using the Ridom server.

RESULTS

Gram-negative bacteria were isolated from 21 mothers (15%), 15 neonates (11%), 2 health workers (3%), and 13 inanimate objects (19%); a total of 131 Gram-negative isolates were identified of which 104 were EKE bacteria i.e., 23 (22%) E. coli, 50 (48%) K. pneumoniae, and 31 (30%) Enterobacter. Carbapenems were the most effective antibiotics as 89% (93/104) of the isolates were susceptible to meropenem; however, multidrug resistance was prevalent i.e., 61% (63/104). Furthermore, carbapenemase production and carbapenemase gene prevalence were low; 10% (10/104) and 6% (6/104), respectively. Extended spectrum β-lactamase (ESBL) production occurred in 37 (36%) isolates though 61 (59%) carried ESBL-encoding genes, mainly blaCTX-M (93%, 57/61) implying that blaCTX-M is the ideal gene for tracking ESBL-mediated resistance at Mulago. Additionally, spatial cluster analysis revealed isolates from mothers, new-borns, health workers, and environment with similar phenotypic/genotypic characteristics, suggesting transmission of multidrug-resistant EKE to new-borns.

CONCLUSION

Our study shows evidence of transmission of drug resistant EKE bacteria in the maternity ward of Mulago hospital, and the dynamics in the ward are more likely to be responsible for transmission but not individual mother characteristics. The high prevalence of drug resistance genes highlights the need for more effective infection prevention/control measures and antimicrobial stewardship programs to reduce spread of drug-resistant bacteria in the hospital, and improve patient outcomes.

Predominance of multi-drug resistant extended spectrum β lactamase producing bacteria from marine fishes

The present study aimed to determine the extended spectrum beta lactamase (ESBL) genes in the bacteria from fresh exportable fish samples collected along South east coast of India, Chennai. ESBL genes are the base for the antibiotic resistance in pathogens and it transmitted from one to other species. Totally 2670 isolates were isolated from 293 fish samples which belong to 31 species dominated by Aeromonas, Klebsiella, Serratia, Leclerica, Proteus, Enterobacter, Acinetobacter, Haemophilus, Escherichia, Shigella sp. Out of 2670 isolates, 1958 isolates have multi drug resistant capacity with ESBL genes of bla_CTX, bla_SHV, bla_TEM and bla_AmpC and 712 isolates are not detected ESBL genes. The present study revealed that, the contamination of fresh fish sample with pathogenic bacteria resistant to multiple antibiotics can incriminate seafood as a potential carrier and accentuate an immediate need to prevent environmental infectivity and distribution. Further, hygienic facilitated markets should be developed with ensured quality of seafood.

Gram-negative ESKAPE bacteria bloodstream infections in patients during the COVID-19 pandemic

Bloodstream infections due to bacteria are a highly consequential nosocomial occurrences and the organisms responsible for them are usually multidrug-resistant. The aims of this study were to describe the incidence of bacteremia caused by Gram-negative ESKAPE bacilli during the COVID-19 pandemic and characterize the clinical and microbiological findings including antimicrobial resistance. A total of 115 Gram-negative ESKAPE isolates were collected from patients with nosocomial bacteremia (18% of the total bacteremias) in a tertiary care center in Mexico City from February 2020 to January 2021. These isolates were more frequently derived from the Respiratory Diseases Ward (27), followed by the Neurosurgery (12), Intensive Care Unit (11), Internal Medicine (11), and Infectious Diseases Unit (7). The most frequently isolated bacteria were Acinetobacter baumannii (34%), followed by Klebsiella pneumoniae (28%), Pseudomonas aeruginosa (23%) and Enterobacter spp (16%). A. baumannii showed the highest levels of multidrug-resistance (100%), followed by K. pneumoniae (87%), Enterobacter spp (34%) and P. aeruginosa (20%). The blaCTX-M-15 and blaTEM-1 genes were identified in all beta-lactam-resistant K. pneumoniae (27), while blaTEM-1 was found in 84.6% (33/39) of A. baumannii isolates. The carbapenemase gene blaOXA-398 was predominant among carbapenem-resistant A. baumannii (74%, 29/39) and blaOXA-24was detected in four isolates. One P. aeruginosa isolate was blaVIM-2 gene carrier, while two K. pneumoniae and one Enterobacter spp were blaNDM gene carriers. Among colistin-resistant isolates mcr-1 gene was not detected. Clonal diversity was observed in K. pneumoniae, P. aeruginosa and Enterobacter spp. Two outbreaks caused by A. baumannii ST208 and ST369 were detected, both belonging to the clonal complex CC92 and IC2. A. baumannii was associated with a death rate of 72% (28/32), most of them (86%, 24/28) extensively drug-resistant or pandrug-resistant isolates, mainly in patients with COVID-19 (86%, 24/28) in the Respiratory Diseases Ward. A. baumannii isolates had a higher mortality rate (72%), which was higher in patients with COVID-19. There was no statistically significant association between the multidrug-resistant profile in Gram-negative ESKAPE bacilli and COVID-19 disease. The results point to the important role of multidrug-resistant Gram-negative ESKAPE bacteria causing bacteremia in nosocomial settings before and during the COVID-19 epidemic. Additionally, we were unable to identify a local impact of the COVID-19 pandemic on antimicrobial resistance rates, at least in the short term.

P1

Atrazine toxicity is one of the limiting factors inhibiting sensitive plant growth. Previous studies showed that atrazine-degrading bacteria could alleviate atrazine toxicity. However, there is limited information on how atrazine-degrading bacteria and plant growth-promote bacteria alleviate atrazine toxicity in soybeans. Therefore, the current study aimed to explore the atrazine removal, phosphorus utilization, and the oxidative stress alleviation of atrazine-degrading bacterium Arthrobacter sp. DNS10 and/or inorganic phosphorus-solubilizing bacterium Enterobacter sp. P1 in the reduction of atrazine toxicity in soybean. The results showed that atrazine exposure to soybean seedlings led to significant inhibition in growth, atrazine removal, and phosphorus utilization. However, the co-inoculatied strains significantly increased seedlings biomass, chlorophyll a/b contents, and total phosphorus in leaves accompanied by great reduction of the atrazine-induced antioxidant enzymes activities and malonaldehyde (MDA) contents, as well as atrazine contents in soil and soybeans under atrazine stress. Furthermore, transcriptome analysis highlighted that co-inoculated strains increased the expression levels of genes related to photosynthetic-antenna proteins, carbohydrate metabolism, and fatty acid degradation in leaves. All the results suggest that the co-inoculation mitigates atrazine-induced oxidative stress on soybean by accelerating atrazine removal from soil and phosphorus accumulation in leaves, enhancing the chlorophyll contents, and regulating plant transcriptome. It may be suggested that co-inoculation of atrazine-degrading bacteria and inorganic phosphorus-solubilizing bacteria can be used as a potential method to alleviate atrazine toxicity to the sensitive crops.

A hybrid technique for sulfamethoxazole (SFM) removal using Enterobacter hormaechei HaG-7: Bio-electrokinetic degradation, pathway and toxicity

Prolonged exposure to antibiotics would likely favor the development of antibiotic resistance and their gene transfer among bacterial communities that are responsible for enriched antibiotic resistant microbes. Sulfamethoxazole (SFM) is a commonly used antibiotic that is released into the environment through human and animal wastes. Improper degradation of SFM poses severe threats to mankind and all life forms. The present study aims in analyzing the process and the probability of utilizing bio-electrokinetic degradation for elimination of SFM from artificially contaminated soil employing Enterobacter hormaechei HaG-7. The desired optimal conditions for SFM degradation (∼98%) were observed at SFM initial concentration (100 mg/L) with an inoculum dose (1% v/v) and applied potential voltage (1.5 V) at pH (7). The results indicated efficient and complete degradation of SFM when compared with the conventional biodegradation.

KDML105)

Climate change is predicted to increase the length, severity, and frequency of drought, which limits plant development by changing various physiological and biochemical processes. Therefore, the present study investigated the effects of drought stress on indole-3-acetic and exopolysaccharide production by Enterobacter sp. NRRU-N13, developed bioformulations of plant growth-promoting Enterobacter sp. NRRU-N13, and evaluated the synergistic effects of these bioformulations in combination with different chitosans on the physiological responses of rice under drought stress. Drought stress inhibited the biosynthesis of indole-3-acetic and exopolysaccharides by Enterobacter sp. NRRU-N13. The viability and stability of Enterobacter sp. NRRU-N13 in bioformulations ranged between 4.70 and 5.70 log CFU g-1 after 80 days at an ambient temperature. Oligochitosan and chitosan at 40‍ ‍mg L-1 were appropriate concentrations for improving rice seedling growth, namely, plant height, root length, shoot and root fresh weights, biomass, and the vigor index (P<0.05). The abilities of these bioformulations, in combination with oligochitosan and chitosan, to alleviate drought stress in rice were examined. The results obtained revealed that the combined application of oligochitosan (40‍ ‍mg L-1) and the FON13 bioformulation (filter cake+40‍ ‍mg kg-1 oligochitosan+10% Enterobacter sp. NRRU-N13) exerted the strongest synergistic effects to alleviate drought stress in rice plants by increasing ascorbate peroxidase and catalase activities, chlo-rophyll concentrations, and relative water content and suppressing proline accumulation and electrolyte leakage from rice plants under drought stress. The present results indicate that the application of oligochitosan combined with these bioformulations effectively improved plant physiology and development. Therefore, the combined application of oligochitosan and a bioformulation of Enterobacter sp. NRRU-N13 is recommended to alleviate drought stress in rice plants.

Emerging resistance to ceftriaxone treatment owing to different ampD mutations in Enterobacter roggenkampii

OBJECTIVES

The Enterobacter cloacae complex is responsible for a variety of infections in hospitalized patients and is resistant to β-lactam antibiotics owing to the expression of AmpC β-lactamase. We report emerging resistance in Enterobacter roggenkampii exposed to ceftriaxone and explore the mechanism underlying mutations responsible for this resistance.

METHODS

Three strains were derived from different samples from one patient (blood and liver abscess fluid). Antimicrobial susceptibility was evaluated by standard broth microdilution, while ampC expression was determined via RT-PCR. Genetic relatedness was evaluated via pulsed-field gel electrophoresis (PFGE). Species identification and comparative genome analysis were performed via genome sequencing. Mutation rate testing and selection of AmpC-derepressed mutants were conducted to explore the mutation mechanism.

RESULTS

E. roggenkampii F1247 was susceptible to third-generation cephalosporins (3GCs); F95 and F1057, found in blood sample on day 11 and liver abscess drainage fluid on day 25, were resistant. ampC expression was 341- and 642-fold higher in F95 and F1057, respectively, than in F1247. Three isolates were the same PFGE and sequence types (ST1778) and were highly homologous (2 and 4 core genome single nucleotide polymorphism differences). Compared to F1247, F95 possessed a 575 bp deletion, including 537 bp of ampD, whereas F1057 harbored only one amino acid mutation (Leu140Pro in ampD). The mutation rates from F1247 exposure to cefotaxime, ceftazidime, ceftriaxone, piperacillin-tazobactam, and cefepime were (1.90 ± 0.21) × 10^-8, (3.18 ± 0.43) × 10^-8, (2.00 ± 0.20) × 10^-8, (2.92 ± 0.29) × 10^-9, and zero, respectively. In vitro-selected mutations responsible for resistance were identified in ampD, ampR, and dacB.

CONCLUSIONS

E. roggenkampii may develop resistance in vivo and in vitro upon exposure to 3GCs and to a lesser extent to piperacillin-tazobactam. 3GCs should not be used as a monotherapy for E. roggenkampii infections. Therapy using cefepime or carbapenems may be preferred to piperacillin-tazobactam in the treatment of E. roggenkampii, especially if source control is difficult.

Halotolerant native bacteria Enterobacter 64S1 and Pseudomonas 42P4 alleviate saline stress in tomato plants

Salinity is one of the principal abiotic stresses that limit the growth and productivity of crops. The use of halotolerant plant growth-promoting rhizobacteria (PGPR) that increase the growth of salt-stressed crops is an environmentally friendly alternative to promote plant yield under salinity. The aim of this study was to test native PGPR, isolated according to their tolerance to NaCl, and to evaluate their influence on morphological, physiological, and biochemical traits promoted by salt stress in tomato plants. Enterobacter 64S1 and Pseudomonas 42P4 were selected as the most efficient strains in terms of salt tolerance. Both strains were classified as moderately resistant to salinity (NaCl) and maintained their plant growth-promoting activities, such as nitrogen fixation and phosphate solubilization, even in the presence of high levels of salt. The results of a greenhouse experiment demonstrated that PGPR inoculation increased root and shoot dry weight, stem diameter, plant height, and leaf area compared to control noninoculated plants under nonsaline stress conditions, reversing the effects of salinity. Inoculated plants showed increased tolerance to salt conditions by reducing electrolyte leakage (improved membrane stability) and lipid peroxidation and increasing chlorophyll quantum efficiency (Fv/Fm) and the performance index. Also, inoculation increased the accumulation of proline and antioxidant nonenzymatic compounds, such as carotenes and total phenolic compounds. The catalase and peroxidase activities increased with salinity, but the effect was reversed by Enterobacter 64S1. In conclusion, Enterobacter 64S1 and Pseudomonas 42P4 isolated from salt-affected regions have the potential to alleviate the deleterious effects of salt stress in tomato crops.

Phenotypic and Genotypic Characterization of Multidrug-Resistant Enterobacter hormaechei Carrying qnrS Gene Isolated from Chicken Feed in China

Multidrug resistance (MDR) in Enterobacteriaceae including resistance to quinolones is rising worldwide. The plasmid-mediated quinolone resistance (PMQR) gene qnrS is prevalent in Enterobacteriaceae. However, the qnrS gene is rarely found in Enterobacter hormaechei (E. hormaechei). Here, we reported one multidrug resistant E. hormaechei strain M1 carrying the qnrS1 and blaTEM-1 genes. This study was to analyze the characteristics of MDR E. hormaechei strain M1. The E. hormaechei strain M1 was identified as Enterobacter cloacae complex by biochemical assay and 16S rRNA sequencing. The whole genome was sequenced by the Oxford Nanopore method. Taxonomy of the E. hormaechei was based on multilocus sequence typing (MLST). The qnrS with the other antibiotic resistance genes were coexisted on IncF plasmid (pM1). Besides, the virulence factors associated with pathogenicity were also located on pM1. The qnrS1 gene was located between insertion element IS2A (upstream) and transposition element ISKra4 (downstream). The comparison result of IncF plasmids revealed that they had a common plasmid backbone. Susceptibility experiment revealed that the E. hormaechei M1 showed extensive resistance to the clinical antimicrobials. The conjugation transfer was performed by filter membrane incubation method. The competition and plasmid stability assays suggested the host bacteria carrying qnrS had an energy burden. As far as we know, this is the first report that E. hormaechei carrying qnrS was isolated from chicken feed. The chicken feed and poultry products could serve as a vehicle for these MDR bacteria, which could transfer between animals and humans through the food chain. We need to pay close attention to the epidemiology of E. hormaechei and prevent their further dissemination. IMPORTANCE Enterobacter hormaechei is an opportunistic pathogen. It can cause infections in humans and animals. Plasmid-mediated quinolone resistance (PMQR) gene qnrS can be transferred intergenus, which is leading to increase the quinolone resistance levels in Enterobacteriaceae. Chicken feed could serve as a vehicle for the MDR E. hormaechei. Therefore, antibiotic-resistance genes (ARGs) might be transferred to the intestinal flora after entering the gastrointestinal tract with the feed. Furthermore, antibiotic-resistant bacteria (ARB) were also excreted into environment with feces, posing a huge threat to public health. This requires us to monitor the ARB and antibiotic-resistant plasmids in the feed. Here, we demonstrated the characteristics of one MDR E. hormaechei isolate from chicken feed. The plasmid carrying the qnrS gene is a conjugative plasmid with transferability. The presence of plasmid carrying antibiotic-resistance genes requires the maintenance of antibiotic pressure. In addition, the E. hormaechei M1 belonged to new sequence type (ST). These data show the MDR E. hormaechei M1 is a novel strain that requires our further research.

Studies on the Transmission of a Tigecycline Resistance-Mediating tet(A) Gene Variant from Enterobacter hormaechei via a Two-Step Recombination Process

To investigate the contribution of a tet(A) variant to tigecycline resistance in Enterobacter hormaechei and the recombination events that occurred during transmission of this variant. MICs were determined by broth microdilution. E. hormaechei G17 was characterized by PCR, transfer assay, S1-PFGE, Southern blot hybridization, and WGS analysis. A tet(A) variant conferring resistance to tigecycline was present in E. hormaechei G17. This strain harbored two resistance plasmids (pG17-1, 264,084 bp and pG17-2, 68,610 bp) and its E. coli transformant Tm-G17TGC one resistance plasmid (pTm-G17, 93,013 bp). The comparative analysis of pG17-1, pG17-2, and pTm-G17 showed that a tet(A) variant-carrying multiresistance gene cluster (~23 kb) originating from pG17-1 had integrated into pG17-2, forming the novel plasmid pTm-G17. In a first step, this multiresistance gene cluster was excised from pG17-1 by recombination of homologous sequences, including △TnAs1 at both termini, thereby generating an unconventional circularizable structure (UCS). In a second step, this UCS integrated into pG17-2 via recombination between homologous sequences, including IS26 present on both, the UCS and pG17-2, thereby giving rise to the new plasmid pTm-G17. In summary, a tet(A) variant conferring resistance to tigecycline was reported in E. hormaechei. Transfer of a tet(A) variant-carrying multiresistance gene cluster between plasmids occurred in a two-step recombination process, in which homologous sequences, including either △TnAs1 or IS26, were involved. IMPORTANCE Tigecycline is an important last-resort broad spectrum antimicrobial agent. This study describes the two-step recombination processes resulting in the transfer of the tet(A) variant gene between different plasmids in E. hormaechei, which depicts the role of recombination processes in the generation of UCSs and new plasmids, both carrying a tet(A) variant conferring resistance to tigecycline. Such processes enhance the dissemination of resistance genes, which is of particular relevance for resistance genes, such as the tet(A) variant. The presence and transmission of a tet(A) variant in E. hormaechei will compromise the efficacy of tigecycline treatment for E. hormaechei associated infection.

Computer-Aided Multi-Epitope Vaccine Design against Enterobacter xiangfangensis

Antibiotic resistance is a global public health threat and is associated with high mortality due to antibiotics’ inability to treat bacterial infections. Enterobacter xiangfangensis is an emerging antibiotic-resistant bacterial pathogen from the Enterobacter genus and has the ability to acquire resistance to multiple antibiotic classes. Currently, there is no effective vaccine against Enterobacter species. In this study, a chimeric vaccine is designed comprising different epitopes screened from E. xiangfangensis proteomes using immunoinformatic and bioinformatic approaches. In the first phase, six fully sequenced proteomes were investigated by bacterial pan-genome analysis, which revealed that the pathogen consists of 21,996 core proteins, 3785 non-redundant proteins and 18,211 redundant proteins. The non-redundant proteins were considered for the vaccine target prioritization phase where different vaccine filters were applied. By doing so, two proteins; ferrichrome porin (FhuA) and peptidoglycan-associated lipoprotein (Pal) were shortlisted for epitope prediction. Based on properties of antigenicity, allergenicity, water solubility and DRB*0101 binding ability, three epitopes (GPAPTIAAKR, ATKTDTPIEK and RNNGTTAEI) were used in multi-epitope vaccine designing. The designed vaccine construct was analyzed in a docking study with immune cell receptors, which predicted the vaccine’s proper binding with said receptors. Molecular dynamics analysis revealed that the vaccine demonstrated stable binding dynamics, and binding free energy calculations further validated the docking results. In conclusion, these in silico results may help experimentalists in developing a vaccine against E. xiangfangensis in specific and Enterobacter in general.

Identifying Algicides of Enterobacter hormaechei F2 for Control of the Harmful Alga Microcystis aeruginosa

Eutrophication has become an increasingly serious environmental issue and has contributed towards an explosion in harmful algal blooms (HABs) affecting local development. HABs can cause serious threats to ecosystems and human health. A newly isolated algicidal strain, Enterobacter hormaechei F2, showed high algicidal activity against the typical HAB species Microcystis aeruginosa. Potential algicides were detected through liquid chromatograph–mass spectrometer analysis, revealing that prodigiosin is an algicide and PQS is a quorum sensing molecule. RNA-seq was used to understand the algicidal mechanisms and the related pathways. We concluded that the metabolism of prodigiosin and PQS are active at the transcriptional level. The findings indicate that E. hormaechei F2 can be used as a potential biological agent to control harmful algal blooms to prevent the deterioration of the ecological and economic value of water bodies.

Emergence of Neonatal Sepsis Caused by MCR-9- and NDM-1-Co-Producing Enterobacter hormaechei in China

Mobile colistin resistance (mcr) genes represent an emerging threat to public health. Reports on the prevalence, antimicrobial profiles, and clonality of MCR-9-producing Enterobacter cloacae complex (ECC) isolates on a national scale in China are limited. We screened 3,373 samples from humans, animals, and the environment and identified eleven MCR-9-positive ECC isolates. We further investigated their susceptibility, epidemiology, plasmid profiles, genetic features, and virulence potential. Ten strains were isolated from severe bloodstream infection cases, especially three of them were recovered from neonatal sepsis. Enterobacter hormaechei was the most predominant species among the MCR-9-producing ECC population. Moreover, the co-existence of MCR-9, CTX-M, and SHV-12 encoding genes in MCR-9-positive isolates was globally observed. Notably, mcr-9 was mainly carried by IncHI2 plasmids, and we found a novel ~187 kb IncFII plasmid harboring mcr-9, with low similarity with known plasmids. In summary, our study presented genomic insights into genetic characteristics of MCR-9-producing ECC isolates retrieved from human, animal, and environment samples with one health perspective. This study is the first to reveal NDM-1- and MCR-9-co-producing ECC from neonatal sepsis in China. Our data highlights the risk for the hidden spread of the mcr-9 colistin resistance gene.

and its ability to promote cadmium/lead accumulation in Centella asiatica L

In the present study, we characterized the plant growth-promoting traits of Enterobacter sp. FM-1 (FM-1) and investigated its ability to promote growth and increase IAA, P, and Fe concentrations as well as Cd and Pb accumulation in Centella asiatica L. (C. asiatica L.) in upstream area (UA) soil and downstream area (DA) soil that we collected from Siding mine. The results demonstrated that FM-1 secreted IAA, produced siderophores, and had P-solubilization ability even under Cd exposure. IAA secretion reached a maximum of 108.3 ± 1.3 mg L^-1 under Cd exposure at 25 mg L^-1. Siderophore production reached a maximum of 0.94 ± 0.01 under Cd exposure at 50 mg L^-1. Pot experiments indicated that FM-1 successfully colonized the roots of C. asiatica L. In both soils, inoculation with FM-1 decreased the pH in rhizosphere soil and increased the bioavailability of both Cd and Pb. In addition, inoculation with FM-1 increased the IAA, P, and Fe concentrations and simultaneously promoted both Cd and Pb accumulation in C. asiatica L. The Cd and Pb concentrations in leaves increased 1.73- and 1.07-fold in the UA soil and 1.25- and 1.11-fold in the DA soil, respectively. Thus, the Cd-resistant strain FM-1 presented excellent PGP traits and could facilitate Cd and Pb phytoremediation by C. asiatica L.

Isolation, characterization and biocontrol efficacy of a T4-like phage virulent to multidrug-resistant Enterobacter hormaechei

Enterobacter hormaechei is an important emerging pathogen, often exhibiting resistance to multiple clinically important antibiotics. In this study, E. hormaechei was found, for the first time, to be lethal to fish. Bacteriophages are considered potential treatments for bacterial infections. The lytic phage vB_EhoM-IME523 (abbreviated 'IME523') infecting multidrug-resistant E. hormaechei was isolated from hospital sewage. IME523 exhibits T4-like morphology, including a prolate icosahedral head 110 ± 1.89 nm (mean ± SD) long and 82 ± 0.75 nm wide, and a contractile tail of ca. 110 ± 0.91 nm in length. The complete genome length of phage IME523 is 172763 bp, with a G + C content of 39.97%. The whole genome sequence of IME523 has a 93.10% average nucleotide identity (ANI) and a 53.3% in silico DNA-DNA hybridization (isDDH) value with the closest-related Enterobacter phage vB_EclM_CIP9 ('CIP9'). ANI and isDDH values between IME523 and other phages were lower than 78 and 22%, respectively. IME523 and CIP9 formed a monophyletic branch in a phylogenetic tree based on the terminase large subunit, DNA polymerase protein and whole genome phylogenetic analysis. Results suggest that IME523 is a novel species in the subfamily Tevenvirinae and forms a novel genus together with CIP9. No IME523 open reading frame was found to be associated with virulence factors or antibiotic resistance genes. IME523 showed promising protection to zebrafish and brocade carp against E. hormaechei challenge.