fENko-Kae01 is a flagellum-specific jumbo phage infecting Klebsiella aerogenes.

BACKGROUND: Klebsiella aerogenes is an opportunistic pathogen that causes a wide variety of infections. Due to the rising problem of antibiotic resistance, novel antibiotics and strategies to combat bacterial infections are needed. Host-specific bacteriophages are natural enemies of bacteria and can be used in phage therapy as an alternative form of treatment against bacterial infections. Jumbo phages are defined as phages with genomes larger than 200 kb. Relatively few studies have been done on jumbo phages compared to smaller phages. RESULTS: A novel phage, fENko-Kae01, was isolated from a commercial phage cocktail. Genomic analysis revealed that fENko-Kae01 is a lytic jumbo phage with a 360 kb genome encoding 578 predicted genes. No highly similar phage genomes were identified and fENko-Kae01 may be a completely new genus representative. No known genes associated with lysogenic life cycle, bacterial virulence, or antibiotic resistance were identified. The phage had myovirus morphology and a narrow host range. Phage resistant bacterial mutants emerged under phage selection. Whole genome sequencing revealed that the biogenesis of the flagellum was affected in four mutants and the lack of functional flagellum was confirmed in motility assays. Furthermore, phage fENKo-Kae01 failed to adsorb on the non-motile mutants indicating that the bacterial flagellum is the phage-binding receptor. CONCLUSIONS: fENko-Kae01 is a novel jumbo bacteriophage that is considered safe for phage therapy. fENko-Kae01 uses the flagellum as the phage-binding receptor and may represent a completely novel genus.

Differences in clinical outcomes of bloodstream infections caused by Klebsiella aerogenes, Klebsiella pneumoniae and Enterobacter cloacae: a multicentre cohort study.

BACKGROUND: Klebsiella aerogenes has been reclassified from Enterobacter to Klebsiella genus due to its phenotypic and genotypic similarities with Klebsiella pneumoniae. It is unclear if clinical outcomes are also more similar. This study aims to assess clinical outcomes of bloodstreams infections (BSI) caused by K. aerogenes, K. pneumoniae and Enterobacter cloacae, through secondary data analysis, nested in PRO-BAC cohort study. METHODS: Hospitalized patients between October 2016 and March 2017 with monomicrobial BSI due to K. aerogenes, K. pneumoniae or E. cloacae were included. Primary outcome was a composite clinical outcome including all-cause mortality or recurrence until 30 days follow-up. Secondary outcomes were fever ≥ 72 h, persistent bacteraemia, and secondary device infection. Multilevel mixed-effect Poisson regression was used to estimate the association between microorganisms and outcome. RESULTS: Overall, 29 K. aerogenes, 77 E. cloacae and 337 K. pneumoniae BSI episodes were included. Mortality or recurrence was less frequent in K. aerogenes (6.9%) than in E. cloacae (20.8%) or K. pneumoniae (19.0%), but statistical difference was not observed (rate ratio (RR) 0.35, 95% CI 0.08 to 1.55; RR 0.42, 95% CI 0.10 to 1.71, respectively). Fever ≥ 72 h and device infection were more common in K. aerogenes group. In the multivariate analysis, adjusted for confounders (age, sex, BSI source, hospital ward, Charlson score and active antibiotic therapy), the estimates and direction of effect were similar to crude results. CONCLUSIONS: Results suggest that BSI caused by K. aerogenes may have a better prognosis than E. cloacae or K. pneumoniae BSI.

Bacteriogenic synthesis of morphologically diverse silver nanoparticles and their assessment for methyl orange dye removal and antimicrobial activity.

Nanotechnology and nanoparticles have gained massive attention in the scientific community in recent years due to their valuable properties. Among various AgNPs synthesis methods, microbial approaches offer distinct advantages in terms of cost-effectiveness, biocompatibility, and eco-friendliness. In the present research work, investigators have synthesized three different types of silver nanoparticles (AgNPs), namely AgNPs-K, AgNPs-M, and AgNPs-E, by using Klebsiella pneumoniae (MBC34), Micrococcus luteus (MBC23), and Enterobacter aerogenes (MBX6), respectively. The morphological, chemical, and elemental features of the synthesized AgNPs were analyzed by using UV-Vis spectroscopy (UV-Vis), Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and energy-dispersive spectroscopy (EDX). UV-Vis absorbance peaks were obtained at 475, 428, and 503 nm for AgNPs-K, AgNPs-M, and AgNPs-E, respectively. The XRD analysis confirmed the crystalline nature of the synthesized AgNPs, having peaks at 26.2°, 32.1°, and 47.2°. At the same time, the FTIR showed bands at 599, 963, 1,693, 2,299, 2,891, and 3,780 cm-1 for all the types of AgNPs indicating the presence of bacterial biomolecules with the developed AgNPs. The size and morphology of the AgNPs varied from 10 nm to several microns and exhibited spherical to porous sheets-like structures. The percentage of Ag varied from 37.8% (wt.%) to 61.6%, i.e., highest in AgNPs-K and lowest in AgNPs-M. Furthermore, the synthesized AgNPs exhibited potential for environmental remediation, with AgNPs-M exhibiting the highest removal efficiency (19.24% at 120 min) for methyl orange dye in simulated wastewater. Further, all three types of AgNPs were evaluated for the removal of methyl orange dye from the simulated wastewater, where the highest dye removal percentage was 19.24% at 120 min by AgNPs-M. Antibacterial potential of the synthesized AgNPs assessment against both Gram-positive (GPB) Bacillus subtilis (MBC23), B. cereus (MBC24), and Gram-negative bacteria Enterococcus faecalis (MBP13) revealed promising results, with AgNPs-M, exhibiting the largest zone of inhibition (12 mm) against GPB B. megaterium. Such investigation exhibits the potential of the bacteria for the synthesis of AgNPs with diverse morphology and potential applications in environmental remediation and antibacterial therapy-based synthesis of AgNPs.

Molecular Epidemiology of Carbapenem-Resistant Klebsiella aerogenes in Japan.

Information regarding Klebsiella aerogenes haboring carbapenemase in Japan is limited. A comprehensive nationwide survey was conducted from September 2014 to December 2022, and 67 non-duplicate strains of carbapenem-resistant K. aerogenes were isolated from 57 healthcare facilities in Japan. Through genetic testing and whole-genome sequencing, six strains were found to possess carbapenemases, including imipenemase (IMP)-1, IMP-6, New Delhi metallo-ß-lactamase (NDM)-1, and NDM-5. The strain harboring blaNDM-5 was the novel strain ST709, which belongs to the clonal complex of the predominant ST4 in China. The novel integron containing blaIMP-1 featured the oxacillinase-101 gene, which is a previously unreported structure, with an IncN4 plasmid type. However, integrons found in the strains possessing blaIMP-6, which were the most commonly identified, matched those reported domestically in Klebsiella pneumoniae, suggesting the prevalence of identical integrons. Transposons containing blaNDM are similar or identical to the transposon structure of K. aerogenes harboring blaNDM-5 previously reported in Japan, suggesting that the same type of transposon could have been transmitted to K. aerogenes in Japan. This investigation analyzed mobile genetic elements, such as integrons and transposons, to understand the spread of carbapenemases, highlighting the growing challenge of carbapenem-resistant Enterobacterales in Japan and underscoring the critical need for ongoing surveillance to control these pathogens.

Global phylogeography and genomic characterization of blaKPC and blaNDM-positive clinical Klebsiella aerogenes isolates from China, 2016-2022.

Carbapenem-resistant Klebsiella aerogenes (CRKA), being one of the members of carbapenem-resistant Enterobacteriaceae (CRE), has caused great public health concern, but with fewer studies compared to other CRE members. Furthermore, studies on phylogenetic analysis based on whole genome Single-Nucleotide Polymorphism (SNP) of CRKA were limited. Here, 20 CRKA isolates (11 blaKPC-2-bearing and 9 blaNDM-1/5-harboring) were characterized by antimicrobial susceptibility testing, conjugation assay, whole genome sequencing (WGS) and bioinformatics analysis. Additionally, the phylogeographic relationships of K. aerogenes were further investigated from public databases. All isolates were multidrug-resistant (MDR) bacteria, and they demonstrated susceptibility to colistin. Most blaKPC-2 or blaNDM-1/5-carrying plasmids were found to be conjugative. Phylogenetic analysis revealed the clonal dissemination of K. aerogenes primarily occurred within clinical settings. Notably, some strains in this study showed the potential for clonal transmission, sharing few SNPs between K. aerogenes and KPC- and/or NDM-positive K. aerogenes isolated from various countries. The STs of K. aerogenes strains had significant diversity. WGS analysis showed that the IncFIIK plasmid was the most prevalent carrier of blaKPC-2, and, blaNDM-1/5 were detected on the IncX3 plasmids. The Tn6296 and Tn3000 transposons were most common vehicles for facilitating the transmission of blaKPC-2 and blaNDM-1/5, respectively. This study highlights the importance of continuous screening and surveillance by WGS for analysis of drug-resistant strains in hospital settings, and provide clinical information that supports epidemiological and public health research on human pathogens.

In-depth analysis of Klebsiella aerogenes resistome, virulome and plasmidome worldwide.

Klebsiella aerogenes is an emergent pathogen associated with outbreaks of carbapenem-resistant strains. To date, studies focusing on K. aerogenes have been small-scale and/or geographically restricted. Here, we analyzed the epidemiology, resistome, virulome, and plasmidome of this species based on 561 genomes, spanning all continents. Furthermore, we sequenced four new strains from Brazil (mostly from the Amazon region). Dozens of STs occur worldwide, but the pandemic clones ST93 and ST4 have prevailed in several countries. Almost all genomes were clinical, however, most of them did not carry ESBL or carbapenemases, instead, they carried chromosomal alterations (omp36, ampD, ampG, ampR) associated with resistance to ß-lactams. Integrons were also identified, presenting gene cassettes not yet reported in this species (blaIMP, blaVIM, blaGES). Considering the virulence loci, the yersiniabactin and colibactin operons were found in the ICEKp10 element, which is disseminated in genomes of several STs, as well as an incomplete salmochelin cluster. In contrast, the aerobactin hypervirulence trait was observed only in one ST432 genome. Plasmids were common, mainly from the ColRNAI replicon, with some carrying resistance genes (mcr, blaTEM, blaNDM, blaIMP, blaKPC, blaVIM) and virulence genes (EAST1, senB). Interestingly, 172 genomes of different STs presented putative plasmids containing the colicin gene.

Genomic characterisation of blaNDM-5-IncX3 plasmid in an ST4 Klebsiella aerogenes clinical isolate.

OBJECTIVES: The dissemination of New Delhi metallo-ß-lactamase-5 (NDM-5) among various species of Enterobacterales has attracted serious global attention. Here, we characterise the genomic characterisation of blaNDM-5-IncX3 plasmid (pNDM-KA3) in an ST4 Klebsiella aerogenes (KA3) strain isolated from a neonate with pneumonia. METHODS: Antimicrobial susceptibility and multilocus sequence typing was performed for the KA3. The plasmid conjugation assay and plasmid stability of the KA3 (pNDM-KA3) were also analysed. The pNDM-KA3 plasmid was further analysed by whole-genome sequencing and comparative analysis to determine the genetic environment of blaNDM-5. RESULTS: The KA3 strain belongs to ST4 and shows high resistance to ß-lactam antibiotics, including carbapenems, but is susceptible to ciprofloxacin, amikacin, tigecycline, and colistin. The pNDM-KA3 was successfully transferred to the recipient E. coli J53 and showed strong stability in K. aerogenes. Genomic sequencing revealed that the pNDM-KA3 plasmid was assigned to plasmid incompatibility group X3 with 43367 bp, and a conserved structure sequence of △IS3000-△ISAba125-IS5-blaNDM-5-bleMBL- trpF-dsbC-IS26 was detected upstream and downstream of the blaNDM-5 gene. Further analysis revealed that insertion sequences mediated the dissemination of blaNDM-5 from other species of Enterobacterales. The pNDM-KA3 showed high similarity to blaNDM-5-harbouring plasmids in other species of Enterobacterales, with these plasmids carrying genes for replication (repB), partitioning (parA and parB), stability (hns), and conjugative transfer (virB and virD). CONCLUSIONS: Continued monitoring for the dissemination of blaNDM-5 among uncommon Enterobacterales species should be further reinforced.

Klebsiella aerogenes ingestion elicits behavioral changes and innate immunity in the host, Caenorhabditis elegans.

Klebsiella aerogenes (previously known as Enterobacter aerogenes) is a common opportunistic pathogen that infect the respiratory tract and central nervous system. However, how it interferes the host regulatory mechanism has not been previously described. When C. elegans were exposed to K. aerogenes, they exhibited a shorter lifespan compared to those fed with E. coli OP50. The time required for 50 % of L4 hermaphrodite nematodes to die when exposed to K. aerogenes was approximately 9 days, whereas it was about 18 days when fed with E. coli OP50. The interaction with K. aerogenes also affected the physical activity of C. elegans. Parameters like pharyngeal pumping, head thrashing, body bending, and swimming showed a gradual decline during infection. The expression of serotonin-mediated axon regeneration K. aerogenes infection led to increased levels of reactive oxygen species (ROS) in C. elegans compared to E. coli OP50-fed worms. The nematodes activated antioxidant mechanisms, including the expression of SODs, to counteract elevated ROS levels. The interaction with K. aerogenes activated immune regulatory pathways in C. elegans, including the mTOR signaling pathway downstream player SGK-1. Lifespan regulatory pathways, such as pha-4 and pmk-1, were also affected, likely contributing to the nematode ability to survive in a pathogenic environment. K. aerogenes infection has a detrimental impact on the healthspan and lifespan of C. elegans, affecting physical activity, intestinal health, serotonin regulation, ROS levels, and immune responses. These findings provide insights into the complex interactions between K. aerogenes and host organisms.

Systemic metabolic engineering of Enterobacter aerogenes for efficient 2,3-butanediol production.

2,3-Butanediol (2,3-BDO) is an important gateway molecule for many chemical derivatives. Currently, microbial production is gradually being recognized as a green and sustainable alternative to petrochemical synthesis, but the titer, yield, and productivity of microbial 2,3-BDO remain suboptimal. Here, we used systemic metabolic engineering strategies to debottleneck the 2,3-BDO production in Enterobacter aerogenes. Firstly, the pyruvate metabolic network was reconstructed by deleting genes for by-product synthesis to improve the flux toward 2,3-BDO synthesis, which resulted in a 90% increase of the product titer. Secondly, the 2,3-BDO productivity of the IAM1183-LPCT/D was increased by 55% due to the heterologous expression of DR1558 which boosted cell resistance to abiotic stress. Thirdly, carbon sources were optimized to further improve the yield of target products. The IAM1183-LPCT/D showed the highest titer of 2,3-BDO from sucrose, 20% higher than that from glucose, and the yield of 2,3-BDO reached 0.49 g/g. Finally, the titer of 2,3-BDO of IAM1183-LPCT/D in a 5-L fermenter reached 22.93 g/L, 85% higher than the wild-type strain, and the titer of by-products except ethanol was very low. KEY POINTS: Deletion of five key genes in E. aerogenes improved 2,3-BDO production The titer of 2,3-BDO was increased by 90% by regulating metabolic flux Response regulator DR1558 was expressed to increase 2,3-BDO productivity.

Klebsiella aerogenes exacerbates colon tumorigenesis in the AOM/DSS-induced C57BL/6J mouse.

Klebsiella aerogenes (K. aerogenes, KA) is a gram-negative opportunistic pathogen from the Klebsiella species and the Enterobacteriaceae family. However, the impact of K. aerogenes on colorectal cancer (CRC) remains uncertain. A colitis-associated tumorigenesis animal model was established by administering azoxymethane (AOM) and dextran sulfate sodium (DSS) to C57BL/6J mice. The concentration of K. aerogenes gavage in mice was 109 cfu. The study measured the following parameters: tumor formation (number and size), intestinal permeability (MUC2, ZO-1, and Occludin), colonic inflammation (TNF-α, IL-1ß, IL-6, and IL-10), proliferation and the fluctuation of the intestinal flora. Under the AOM/DSS-treated setting, K. aerogenes colonization worsened colitis by exacerbating intestinal inflammatory reaction and destroying the mucosal barrier. The intervention markedly augmented the quantity and dimensions of neoplasm in the AOM/DSS mice, stimulated cellular growth, and impeded cellular programmed cell death. In addition, K. aerogenes exacerbated the imbalance of the intestinal microbiota by elevating the abundance of Pseudomonas, Erysipelatoclostridium, Turicibacter, Rikenella, and Muribaculum and leading to a reduction in the abundance of Odoribacter, Alloprevotella, Roseburia, and Lachnospiraceae_NK4A136_group. The presence of K. aerogenes in AOM/DSS-treated mice promoted tumorigenesis, worsened intestinal inflammation, disrupted the intestinal barrier, and caused disturbance to the gut microbiota.

Regulation of miR-61 and col-19 via TGF-ß and Notch signalling in Caenorhabditis elegans against Klebsiella aerogenes infection.

Klebsiella aerogenes, previously known as Enterobacter aerogenes, is a gram-negative bacterium typically present in the gastrointestinal tract. While numerous studies reported the pathogenicity and drug resistance of this bacterium there remains a lack of comprehensive research on K. aerogenes induced alterations in the host cellular mechanisms. In this study, we identify a previously uncharacterized C. elegans miR-61 that defines an evolutionarily conserved miRNA important for development and innate immunity regulation through Notch and TGF-ß signaling pathway. We employed C. elegans wild-type (N2) as well as mutant strains, such as TGF-ß (sma-6) and notch-signaling pathway mutants (adm-4 and mir-61). Our results have demonstrated that the K. aerogenes infected mutants exhibited significantly reduced survival rate, reduced pharyngeal pumping, altered swimming and chemotactic behavior. Moreover, K. aerogenes affects the healthspan by increasing ROS level in the mutants. The gene expression analysis revealed that K. aerogenes upregulated egl-30, tph-1 and sod-1 in adm-4, mir-61 mutants not in sma-6. The in-silico analysis indicated an interaction between mir-61 and col-19, which was confirmed by the upregulation of miR-61 expression and the downregulation of col-19 in sma-6, adm-4, and wild-type strains. These findings suggest that C. elegans activates mir-61 and col-19 regulation through the Notch and TGF-ß signaling pathway against K. aerogenes infection.

Development and evaluation of a colorimetric LAMP-based biosensor for rapid detection of a nosocomial infection agent, Citrobacter freundii.

Simple and fast diagnosis of Citrobacter freundii which is an important cause of nosocomial infection in human is crucial to achieve early treatment. We have developed and evaluated an optical LAMP-based biosensor for the visual detection of C. freundii for the first time. The efficiency of the assay was investigated and compared to PCR method. The selectivity and specificity of the biosensor were analyzed using Morganella morganii, Enterobacter aerogenes, Pseudomonas aeruginosa, Yersinia enterocolitica, Shigella sonnei, Serratia marcescens, Burkholderia cepacia and Klebsiella pneumoniae and a mixed-culture medium. Endpoint analysis using hydroxy naphthol blue was applied, and the color change to sky blue and no color change from violet indicated positive and negative results, respectively. The absorption at 650 nm was measured 0.39 for the positive sample, while the mean absorption of the test samples, including water, was 0.23. The specificity of the method was equal to that of PCR. However, the sensitivity was determined as 12.24 fg/µL of the genomic content of C. freundii, higher than PCR assay. The developed LAMP-based method provided a rapid and accurate technique for molecular diagnostics of C. freundii, making it a suitable technique for point-of-care diagnostics in cases of urgent situations.

Gas Chromatography-Mass Spectrometry Profiling of Volatile Metabolites Produced by Some Bacillus spp. and Evaluation of Their Antibacterial and Antibiotic Activities.

Bacillus species produce different classes of antimicrobial and antioxidant substances: peptides or proteins with different structural compositions and molecular masses and a broad range of volatile organic compounds (VOCs), some of which may serve as biomarkers for microorganism identification. The aim of this study is the identification of biologically active compounds synthesized by five Bacillus species using gas chromatography coupled to mass spectrometry (GC-MS). The current study profoundly enhances the knowledge of antibacterial and antioxidant metabolites ensuring the unambiguous identification of VOCs produced by some Bacillus species, which were isolated from vegetable samples of potato, carrot, and tomato. Phylogenetic and biochemical studies were used to identify the bacterial isolates after culturing. Phylogenetic analysis proved that five bacterial isolates BSS12, BSS13, BSS16, BSS21, and BSS25 showed 99% nucleotide sequence similarities with Bacillus safensis AS-08, Bacillus cereus WAB2133, Bacillus acidiproducens NiuFun, Bacillus toyonesis FORT 102, and Bacillus thuringiensis F3, respectively. The crude extract was prepared from bacterial isolates to assess the antibiotic resistance potency and the antimicrobial potential against various targeted multidrug-resistant strains, including yeast strains such as Candida albicans, Candida krusei, and bacterial strains of Enterococcus hirae, Escherichia coli, Klebsiella aerogenes, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus group B, Streptococcus mutans, Shigella sonnei, Salmonella enteritidis, Serratia marcescens, Pseudomonas aeruginosa, and Proteus vulgaris. GC-MS analysis of bacterial strains found that VOCs from Bacillus species come in a variety of chemical forms, such as ketones, alcohols, terpenoids, alkenes, etc. Overall, 69 volatile organic compounds were identified from five Bacillus species, and all five were found to share different chemical classes of volatile organic components, which have a variety of pharmacological applications. However, eight antibacterial compounds with different concentrations were commonly found in all five species: acetoin, acetic acid, butanoic acid, 2-methyl-, oxime-, methoxy-phenyl, phenol, 1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester, nonanoic acid, and hexadecanoic acid, methyl. The present study has demonstrated that bacterial isolates BSS25, BSS21, and BSS16 display potent inhibitory effects against Candida albicans, while BSS25, BSS21, and BSS13 exhibit the ability to restrain the growth and activity of Candida krusei. Notably, BSS25 and BSS21 are the only isolates that demonstrate substantial inhibitory activity against Klebsiella aerogenes. This disparity in inhibitory effects could be attributed to the higher concentrations of acetoin in BSS25 and BSS21, whereas BSS16 and BSS13 have relatively elevated levels of butanoic acid, 2-methyl-. Certainly, the presence of acetoin and butanoic acid, 2-methyl-, contributes to the enhanced antibacterial potential of these bacterial strains, in conjunction with other organic volatile compounds and peptides, among other factors. The biology and physiology of Bacillus can be better understood using these results, which can also be used to create novel biotechnological procedures and applications. Moreover, because of its exceptional ability to synthesize and produce a variety of different antibacterial compounds, Bacillus species can serve as natural and universal carriers for antibiotic compounds in the form of probiotic cultures and strains to fight different pathogens, including mycobacteria.

A novel phage carrying capsule depolymerase effectively relieves pneumonia caused by multidrug-resistant Klebsiella aerogenes.

BACKGROUND: Klebsiella aerogenes can cause ventilator-associated pneumonia by forming biofilms, and it is frequently associated with multidrug resistance. Phages are good antibiotic alternatives with unique advantages. There has been a lack of phage therapeutic explorations, kinetic studies, and interaction mechanism research targeting K. aerogenes. METHODS: Plaque assay, transmission electron microscopy and whole-genome sequencing were used to determine the biology, morphology, and genomic characteristics of the phage. A mouse pneumonia model was constructed by intratracheal/endobronchial delivery of K. aerogenes to assess the therapeutic effect of phage in vivo. Bioinformatics analysis and a prokaryotic protein expression system were used to predict and identify a novel capsule depolymerase. Confocal laser scanning microscopy, Galleria mellonella larvae infection models and other experiments were performed to clarify the function of the capsule depolymerase. RESULTS: A novel lytic phage (pK4-26) was isolated from hospital sewage. It was typical of the Podoviridae family and exhibited serotype specificity, high lytic activity, and high environmental adaptability. The whole genome is 40,234 bp in length and contains 49 coding domain sequences. Genomic data show that the phage does not carry antibiotic resistance, virulence, or lysogenic genes. The phage effectively lysed K. aerogenes in vivo, reducing mortality and alleviating pneumonia without promoting obvious side effects. A novel phage-derived depolymerase was predicted and proven to be able to digest the capsule, remove biofilms, reduce bacterial virulence, and sensitize the bacteria to serum killing. CONCLUSIONS: The phage pK4-26 is a good antibiotic alternative and can effectively relieve pneumonia caused by multidrug-resistant K. aerogenes. It carries a depolymerase that removes biofilms, reduces virulence, and improves intrinsic immune sensitivity.

Optimization of hydrogen production in Enterobacter aerogenes by Complex I peripheral fragments destruction and maeA overexpression.

As a concentrated energy source with high added value, hydrogen has great development prospects, with special emphasis on sustainable microbial production as a replacement for traditional fossil fuels. In this study, λ-Red recombination was used to alter the activity of Complex I by single and combined knockout of nuoE, nuoF and nuoG. In addition, the conversion of malic to pyruvic acid was promoted by overexpressing the maeA gene, which could increase the content of NADH and formic acid in the bacterial cells. Compared to the original strain, hydrogen production was 65% higher in the optimized strain IAM1183-EFG/M, in which the flux of the formic acid pathway was increased by 257%, the flux of the NADH pathway was increased by 13%, and the content of metabolites also changed significantly. In further bioreactor, the total hydrogen production of the scale-up IAM1183-EFG/M after 44 h of fermentation was 4.76 L, which increased by 18% compared with the starting strain. This study provides a new direction for future exploration of microbial hydrogen production by combinatorial modification of multiple genes.

Assessing the protection mechanisms on Enterobacter aerogenes ATCC 13048 by potentially probiotic strain Lacticaseibacillus casei XN18: An experimental and modeling study.

In this study, Lacticaseibacillus casei XN18 had a remarkable resistant to simulated gastrointestinal conditions, hydrophobicity (38.60%), auto-aggregation (29.80%), co-aggregation (21.10%), adhesion (9.50%), anti-adhesion (24.40-36.90%), antioxidant activity (46.47%), cholesterol assimilation (41.10%), and antimicrobial effect on some pathogenic microorganisms. The modified double layer method, and Enterobacter aerogenes (inhibition zone (IZ) = 9.10 mm) and Listeria monocytogenes (IZ = 14.60 mm) were the most sensitive and resistant pathogens to the probiotic strain. The Lb. casei was sensitive to ciprofloxacin (IZ = 23 mm) and nitrofurantoin (IZ = 25.10 mm), semi-sensitive to imipenem (IZ = 18.80 mm), erythromycin (IZ = 16.90 mm), and chloramphenicol (IZ = 17.90 mm), and resistant to ampicillin (IZ = 9.60 mm) and nalidixic acid (IZ = 9.90 mm). The Lb. casei showed no haemolytic and DNase properties, and it could therefore be used for health-promoting purposes. In the next section, multilayer perceptron (MLP) neural network (NN) and gaussian process regression (GPR) models with k-fold cross validation method were used for predicting the rate of probiotic viability based on three levels of pH and time. The results showed that GPR has the lowest error. The mean absolute percentage error (MAPE), root mean absolute error (RMSE) and coefficient of determination (R2) for GPR and MLP models were 1.49 ± 0.40, 0.21 ± 0.03, 0.98 ± 0.05 and 6.66 ± 0.98, 0.83 ± 0.23 0.82 ± 0.09, respectively. So, the GPR model can be reliably used as a useful method to predict the probiotic viability in similar cases.

Assessing the protection mechanisms against Enterobacter aerogenes by analyzing aggregation, adherence, antagonistic activity, and safety properties of potentially probiotic strain Lactobacillus brevis G145.

The aim of this study was to evaluate the probiotic potential of Lactobacillus brevis G145 isolated from traditional Khiki cheese, analyzing pH and bile resistance, physicochemical properties of the strain (hydrophobicity, auto- and co-aggregation), cholesterol removal, hydroxyl radical scavenging activity, adhesion ability to Caco-2 cells monolayer, and adhesion competition on Enterobacter aerogenes (competition, inhibition and replacement assays). Also, DNase, haemolytic activity, biogenic amine production and antibiotic susceptibility was investigated. L. brevis G145 was resistant to acidic pHs, bile salts, and simulated gastrointestinal conditions, and showed remarkable cell surface hydrophobicity (49.56%), co-aggregation (28.90%), auto-aggregation (34.10%), adhesion (9.40%), cholesterol removal (45.50%), and antioxidant (52.19%) properties. According to the results of well diffusion agar and disc diffusion agar tests, the highest and lowest inhibition zones were accounted for Staphylococcus aureus and Enterobacter aerogenes, respectively. The isolate did not show haemolytic, DNAse, and biogenic amine production properties. It was sensitive to antibiotics erythromycin, ciprofloxacin, and chloramphenicol, and semi-sensitive to imipenem, ampicillin, nalidixic acid, and nitrofurantoin. According to the findings of probiotic tests L. brevis G145 can be used as a in the food industry.

Piperacillin/tazobactam versus cefepime or carbapenems for cefoxitin-non-susceptible Enterobacter cloacae, Klebsiella aerogenes, Citrobacter freundii, Serratia marcescens and Morganella morganii bacteraemia in immunocompromised patients.

BACKGROUND: The role of piperacillin/tazobactam for treatment of serious infections due to AmpC-producing organisms remains debatable, particularly in immunocompromised patients. METHODS: This was a retrospective cohort study in immunocompromised patients that investigated the effect of definitive treatment with either piperacillin/tazobactam versus cefepime or carbapenems for bacteraemia caused by cefoxitin-non-susceptible Enterobacterales. The primary endpoint was a composite of clinical and microbiological failure. A logistic regression model was constructed to assess the impact of definitive treatment choice on the primary endpoint. RESULTS: A total of 81 immunocompromised patients with blood cultures positive for cefoxitin-non-susceptible Enterobacterales were included for analysis. There was more microbiological failure in the piperacillin/tazobactam arm compared with the cefepime/carbapenem arm (11.4% versus 0.0%, P = 0.019). Definitive treatment with cefepime or a carbapenem was associated with a decreased odds of clinical or microbiological failure (OR 0.303, 95% CI 0.093-0.991, P = 0.048) when controlling for baseline characteristics. CONCLUSIONS: In immunocompromised patients with bacteraemia due to cefoxitin-non-susceptible Enterobacterales, definitive treatment with piperacillin/tazobactam was associated with an increased risk of microbiological failure and higher odds of clinical or microbiological failure compared with cefepime or carbapenems.