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PubMed2023

Capsular Polysaccharide Is Essential for the Virulence of the Antimicrobial-Resistant Pathogen Enterobacter hormaechei.

Nosocomial infections caused by multidrug-resistant (MDR) Enterobacter cloacae complex (ECC) pathogens are on the rise. However, the virulence strategies employed by these pathogens remain elusive. Here, we study the interaction of ECC clinical isolates with human serum to define how this pathogen evades the antimicrobial action of complement, one of the first lines of host-mediated immune defense. We identified a small number of serum-sensitive strains, including Enterobacter hormaechei strain NR3055, which we exploited for the in vitro selection of serum-resistant clones. Comparative genomics between the serum-sensitive NR3055 strain and the isolated serum-resistant clones revealed a premature stop codon in the wzy gene of the capsular polysaccharide biosynthesis locus of NR3055. The complementation of wzy conferred serum resistance to NR3055, prevented the deposition of complement proteins on the bacterial surface, inhibited phagocytosis by human neutrophils, and rendered the bacteria virulent in a mouse model of peritonitis. Mice exposed to a nonlethal dose of encapsulated NR3055 were protected from subsequent lethal infections by encapsulated NR3055, whereas mice that were previously exposed to unencapsulated NR3055 succumbed to infection. Thus, capsule is a key immune evasion determinant for E. hormaechei, and it is a potential target for prophylactics and therapeutics to combat these increasingly MDR human pathogens. IMPORTANCE Infections caused by antimicrobial resistant bacteria are of increasing concern, especially those due to carbapenem-resistant Enterobacteriaceae pathogens. Included in this group are species of the Enterobacter cloacae complex, regarding which there is a paucity of knowledge on the infection biology of the pathogens, despite their clinical relevance. In this study, we combine techniques in comparative genomics, bacterial genetics, and diverse models of infection to establish capsule as an important mechanism of Enterobacter pathogens to resist the antibacterial activity of serum, a first line of host defense against bacterial infections. We also show that immune memory targeting the Enterobacter capsule protects against lethal infection. The further characterization of Enterobacter infection biology and the immune response to infection are needed for the development of therapies and preventative interventions targeting these highly antibiotic resistant pathogens.

Humans↗
PubMed2026

Extensive hidden prophage diversity in Enterobacter species reveals host specificity and local distribution.

Bacteriophages are key drivers of bacterial evolution, particularly through their integration as prophages within host genomes. However, the diversity and host specificity of prophages in relevant pathogens such as Enterobacter species remain poorly characterized. In this study, we revealed the diversity of prophages, mapped their distribution and explored their relationships with their bacterial hosts. We analysed 3,661 prophage sequences identified from the genomes of 20 different Enterobacter species. This analysis uncovered an extensive hidden diversity, comprising 1,617 phage genera and 2,423 phage species - nearly 80% of which were singletons - highlighting an exceptionally rich prophage landscape. We found substantial variation in prophage species richness across host species and isolation sources, with Enterobacter kobei and environmental isolates exhibiting the highest richness. Prophage populations showed strong host specificity and limited cross-species transmission. Moreover, prophages exhibited geographic structuring and significant congruence between host and prophage phylogenies, as well as with the ecological lifestyles of their bacterial hosts. Although we found phages of the same species infecting different host species, these events were infrequent. Finally, bacterial genomes encoded diverse defence systems, mainly PDC-S07, RM type I-II and gabija, whereas only 8.9% of prophages encoded anti-defence systems, mostly anti-CBASS and anti-RM. Overall, this study provides new insights into the diversity of Enterobacter prophages and underscores their ecological and clinical relevance in shaping host adaptation and phage-host dynamics.

Prophages↗
PubMed2025

Isolation and characterization of strictly lytic bacteriophages against carbapenem-resistant Enterobacter cloacae complex.

UNLABELLED: The global surge of carbapenem-resistant Enterobacter cloacae complex (CR-ECC) poses a significant clinical challenge due to limited treatment options. This study aimed to isolate and characterize lytic bacteriophages (phages) targeting CR-ECC. CR-ECC CYEBC080 was used as the bacterial host for isolating lytic phages, and a comprehensive evaluation was conducted on isolated phages, including phage stability under various pH and temperature conditions, host range analysis, killing curves, and therapeutic efficacy in Galleria mellonella larvae and a murine bacteremia model. Twelve lytic phages with distinct random amplified polymorphic DNA patterns were isolated, and transmission electron microscopy confirmed their classification under the Straboviridae family within the Caudoviricetes class. All phages remained stable across pH 3-11 for up to 90 minutes, with an optimal temperature range of 25°C-37°C. Among them, CYPEBC012 exhibited the broadest host range, lysing 93.75% of 80 CR-ECC isolates, while CYPEBC006 displayed the narrowest, lysing only 65%. Whole-genome sequencing revealed 12 phages with linear double-stranded DNA genomes ranging from 177,624 to 180,648 bp. Phage treatment administered at a multiplicity of infection of 10, 1 hour post-infection, significantly improved larval survival at day 7, reaching ≥80% in most groups, except CYPEBC001 (50%) and CYPEBC004 (60%) treatment groups. In CYEBC080-infected mice, CYPEBC012 treatment resulted in 100% survival by day 3 and 80% survival through day 7. Additionally, phage-treated mice exhibited significantly reduced bacterial loads and high phage titers in blood and liver. This study demonstrates the therapeutic potential of CYPEBC012 as a promising strategy against CR-ECC infections, offering an alternative to conventional antimicrobial treatments. IMPORTANCE: This study identified and characterized lytic bacteriophages targeting carbapenem-resistant Enterobacter cloacae complex, with CYPEBC012 exhibiting the broadest host range and significantly improving survival in a murine bacteremia model. Its stability and efficacy highlight its potential for clinical application. Our findings demonstrate that phage therapy offers a promising alternative to conventional treatments to combat antibiotic-resistant infections.

Animals↗
PubMed2026

Genomic and Phenotypic Characterization of Two Novel Enterobacter Phages With EDTA-Enhanced Antibiofilm Activity.

Multidrug-resistant members of the Enterobacter cloacae complex (ECC) are increasingly linked to difficult-to-treat infections and biofilm-mediated antimicrobial tolerance. Here, two lytic phages, vB_EhoIP_HHH and vB_EluM_RZH, displaying podovirus-like and myovirus-like morphology, respectively, were isolated from the River Chelt. HHH has a 39,582 bp genome (51.2% GC, 63 ORFs), while RZH has a 174,197 bp genome (39.4% GC, 314 ORFs), with neither genome carrying antimicrobial resistance, virulence or lysogeny-associated genes. VIRIDIC and VICTOR analyses placed HHH within Kayfunavirus and RZH within Karamvirus, supporting their classification as distinct species. Both phages demonstrated rapid adsorption, short latent periods and stability across physiological pH and temperature ranges. A phage cocktail targeting MDR ECC strain was evaluated with EDTA against established biofilms. Crystal violet assays showed the greatest biomass reduction at MOI 10 with 0.5-0.75 mM EDTA. Bliss independence analysis revealed localized synergy within this window but significant overall antagonism at higher EDTA concentrations. CFU enumeration confirmed greater activity against 24 h than 48 h biofilms. The optimized combination also reduced recoverable bacteria in a fibroblast infection model while maintaining low LDH release. These findings identify two novel lytic Enterobacter phages and support a narrow EDTA concentration window for enhanced phage-mediated antibiofilm activity.

Biofilms↗
PubMed2026

Genomic and phenotypic characterization of mcr-9 carrying Enterobacter oligotrophicus recovered from bovine mastitis.

Bovine mastitis (BM) is a leading cause of economic loss in the dairy industry, driven by decreased milk yields, involuntary culling, and substantial veterinary costs. A single Gram-negative isolate recovered from BM was characterized in this study. For this, antimicrobial susceptibility testing (AST) was performed using the Neg-Urine-Combo 98 panel. Whole-genome sequencing (WGS) was employed to identify antimicrobial resistance genes (ARG), virulence factors (VF) genes, plasmid replicons and prophage sequences. Comparative genomic analysis was performed through phylogenetic analysis. The BM isolate was phenotypically identified as Citrobacter rodentium, however, WGS analysis reclassified the isolate as Enterobacter oligotrophicus. Phenotypic AST revealed a resistance profile of 12%, with the isolate exhibiting resistance to β-lactams antimicrobials, specifically amoxicillin-clavulanate, ampicillin and the cephalosporin-cefoxitin. Conversely, susceptibility was demonstrated for the remaining tested antimicrobials. Genomic profiling identified 31 ARG, 10 VF genes and 6 prophage sequences within the E. oligotrophicus genome. This study provides the first evidence of E. oligotrophicus as a causative agent of BM, expanding the known spectrum of pathogens affecting the dairy industry by delivering the second complete genome of E. oligotrophicus available globally. The identification of 31 ARG, 10 VF, and 6 prophage sequences underscore the potential pathogenic risk and environmental resilience of this isolate. These findings highlight the critical role of WGS-based surveillance in identifying non-conventional mastitis pathogens and underscore the need for targeted mitigation strategies in veterinary medicine.

Animals↗
PubMed2026

Diverse structures of mcr-10-bearing plasmids and high colistin resistance in Enterobacter cloacae complex clinical isolates from South Korea.

BACKGROUND: The emergence of mcr-mediated colistin resistance in Enterobacter cloacae complex (ECC) poses a significant threat to antimicrobial therapy. Among mcr variants, mcr-10 has been identified in various environments, but its genetic diversity, structural context, and functional role in colistin resistance remain unclear. METHODS: We investigated 183 ECC isolates and identified 60 colistin-resistant strains through minimum inhibitory concentration (MIC) testing. The presence of mcr-10 was screened using reference genomes from NCBI, and whole plasmid sequencing was conducted on mcr-10-positive isolates. The genetic environment of mcr-10 was analyzed via synteny and structural annotation. RESULTS: Whole-plasmid sequencing of eight mcr-10-positive ECC isolates identified three replicon types among the mcr-10-harboring plasmids: IncFIB (n=3), IncFII (n=3), and IncFII/IncFIB (n=2). Although all plasmids shared the xerC-mcr-10 cassette, they lacked a conserved backbone and showed diverse genetic contexts with variable insertion sequences near mcr-10, indicating marked structural heterogeneity. No additional antimicrobial resistance genes were detected on these plasmids. When introduced into E. coli DH5α, the plasmids increased colistin MICs only modestly, whereas representative plasmids transferred into colistin-susceptible E. roggenkampii and E. kobei conferred high-level resistance comparable to that of the parental mcr-10-positive isolates. Consistently, qRT-PCR showed higher mcr-10 expression in ECC transformants than in E. coli under colistin exposure, supporting a hostdependent effect on mcr-10-mediated colistin resistance. CONCLUSION: These findings highlight the diversity of mcr-10-carrying plasmids and suggest that mcr-10-mediated colistin resistance is shaped by the host genetic background. Further studies are needed to clarify the mechanisms underlying mcr-10 expression.

Colistin↗
PubMed2026

Mobilization of blaVIM genes via the Tn6292 transposon among carbapenem-resistant Enterobacter cloacae complex isolates from colonized patients in a Spanish hospital.

UNLABELLED: The aim of this study was to perform molecular characterization of the carbapenem-resistant Enterobacter cloacae complex (ECC) isolates from colonized patients in a hospital using whole-genome sequencing (WGS) technology. As part of routine surveillance for multidrug-resistant bacterial colonization, 21 ECC isolates were recovered from patients at San Carlos Hospital in Madrid (Spain) between December 2020 and November 2024. WGS was used to determine their genetic relatedness. Furthermore, species identification, sequence type (ST), resistome, plasmid content, and flanking mobile genetic elements (MGEs) of the carbapenemase genes were derived from the WGS data. The most prevalent carbapenemase gene identified was blaVIM-1 (n = 18, 85.7%), with other notable genes including blaKPC-2 (n = 1, 4.8%), blaKPC-3 (n = 1, 4.8%), and blaOXA-48 (n = 1, 4.8%). Several blaACT and blaESBL variants were also found among the carbapenem-resistant ECC isolates. All of them carried at least one blaACT gene, with blaACT-7 (11/21) and blaTEM-type (14/21) genes being the most common AmpC and ESBL-encoding genes, respectively. Additionally, two isolates exhibited the presence of the mcr-9 gene. Overall, E. hormaechei subsp. steigerwaltii (ST93), followed by E. hormaechei subsp. hoffmanii (ST78 and ST50), were the predominant species and STs circulating among the carbapenem-resistant ECC strains. The blaVIM-1 gene was part of class 1 integrons located within a Tn3-family transposon, Tn6292. blaKPC and blaOXA-48 were linked to Tn4401 and Tn1999 transposons, respectively. In conclusion, the presence of the blaVIM within a transposon Tn6292 enhances its mobility across bacterial genomes, underscoring the value of high-throughput sequencing in monitoring the spread of carbapenem-resistant ECC isolates. IMPORTANCE: This study highlights why monitoring the spread of antibiotic-resistant bacteria in hospitals is critical. By analyzing the complete DNA of carbapenem-resistant bacteria, antibiotics were considered a last line of treatment. We found that the resistance genes are not isolated. Instead, they are embedded within mobile elements called transposons. This means that they can "jump" between different bacteria, accelerating the spread of resistance. These findings emphasize the importance of high-resolution genomic technologies to track and control the spread of these dangerous bacteria in clinical settings, helping preserve the effectiveness of life-saving treatments.

Humans↗
PubMed2026

Genomic Characterisation of Carbapenem-Resistant Klebsiella pneumoniae and Enterobacter hormaechei Clinical Isolates from Nigeria: Evidence of Resistance, Virulence, and Putative Plasmid-Mediated Gene Sharing.

The global proliferation of carbapenem-resistant Enterobacterales (CRE) constitutes one of the most urgent public health threats, yet high-resolution genomic data from sub-Saharan Africa remain critically scarce. We applied whole-genome sequencing (WGS) and comparative phylogenomics to characterise antimicrobial resistance determinants, virulence genes, and mobile genetic elements (MGEs) in three carbapenem-resistant clinical isolates originating from three tertiary hospitals (selected from a broader surveillance collection spanning four facilities) in Osun State, southwestern Nigeria. We purposively selected three isolates, two Klebsiella pneumoniae subsp. pneumoniae (K22, ST411; K31, ST17) and one Enterobacter hormaechei subsp. steigerwaltii (K32, ST45) from a broader surveillance collection of 27 carbapenem-non-susceptible Enterobacterales, to represent phenotypically and genotypically divergent lineages. Resistome analysis revealed extensive plasmid-associated β-lactam and aminoglycoside resistance in K31 (including blaCTX-M-15, blaOXA-1, and blaTEM-1). K32 harboured an intrinsic chromosomal blaACT-17 AmpC gene, while IS26 and ISEcp1 insertion sequences, consistent with transposon-mediated mobilisation, flanked its acquired aminoglycoside and sulfonamide resistance cassettes. K22 lacked detected acquired carbapenemase, ESBL, or plasmid-mediated AmpC genes, indicating that its carbapenem-resistant phenotype may involve non-carbapenemase mechanisms such as porin alteration or efflux-mediated reduced susceptibility; however, this mechanism requires confirmation by direct ompK35/ompK36 sequence analysis and/or phenotypic outer membrane protein profiling. Virulome profiling identified a broader repertoire of siderophore, adhesion, and biofilm genes in both K. pneumoniae isolates than in E. hormaechei. Phylogenomic analysis demonstrated that K22 and K31 cluster within the broader K. pneumoniae population framework but represent distinct high-risk lineages (ST411 and ST17) rather than a single clonal outbreak. Analysis also identified a shared plasmid backbone between K31 and K32, supporting interspecies horizontal gene transfer. These descriptive genomic findings identify clinically relevant resistance and virulence determinants in three purposively selected carbapenem-resistant Enterobacterales from Nigerian tertiary-care hospitals. The detection of shared resistance elements between K. pneumoniae and E. hormaechei suggests possible plasmid-mediated gene sharing. Still, larger WGS studies with long-read sequencing and patient-level epidemiological data are required to define transmission and dissemination patterns.

Nigeria↗
PubMed2026

Functional identification of the key gene Eh-fadB in nicosulfuron degradation by Enterobacter hormaechei ES1 based on multi-omics and enzymatic characterization.

Nicosulfuron is a sulfonylurea herbicide with residues that pose ecological risks in agricultural soils. Here we elucidated the degradation mechanism of Enterobacter hormaechei ES1 through whole-genome sequencing, transcriptomics, metabolomics, gene knockout, heterologous expression, and soil bioremediation assays. Under nicosulfuron stress, ES1 upregulated antioxidant enzymes including SOD, POD, and CAT, along with glutathione synthesis, to scavenge excess reactive oxygen species. HPLC-TOF-MS identified degradation intermediates such as ADMP and ASDM, indicating initial cleavage of the sulfonylurea bridge. Integrated multi-omics prioritized Eh-fadB, encoding a fatty acid β-oxidation multifunctional enzyme, as a novel degradative gene. Targeted knockout of Eh-fadB reduced nicosulfuron degradation from 87.6% to 37.04%, while genetic complementation restored nearly full activity. Purified Eh-FadB directly converted nicosulfuron, with optimal performance at 30 °C and pH 5-6; its activity was enhanced by Na+ and Pb2+ but inhibited by Fe3+. Molecular docking and dynamics identified His-450 and Asn-427 as key residues for substrate binding. In contaminated soil, inoculation with ES1 reduced nicosulfuron content within 21 days and promoted recovery of dehydrogenase and urease activities. This study provides the first genetic and biochemical evidence that a FadB-type enzyme participates in nicosulfuron catabolism, supporting sulfonylurea bridge cleavage and its potential for soil bioremediation.

Eh-fadB↗
PubMed2026

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

BACKGROUND: In February, 2023, an outbreak of Enterobacter hormaechei ST79 carrying blaNDM-5 and blaOXA-48 was linked to contaminated dicloxacillin capsules administered to approximately 79 000 individuals in Denmark. Initial clonal outbreak investigations identified 11 patients with the E hormaechei ST79 outbreak strain, which carried blaNDM-5 on a distinct IncX3 plasmid, and in nine cases, blaOXA-48 was on a distinct IncL plasmid. Interspecies plasmid transfer was observed in one patient, suggesting a potential plasmid-mediated outbreak involving other Enterobacterales. However, no studies have characterised the progression of a clonal outbreak originating from a contaminated medicine into plasmid-mediated dissemination of carbapenemase genes. Hence, we aimed to characterise the clonal and plasmid-mediated spread of carbapenemase genes in this outbreak. METHODS: We conducted a retrospective genomic and epidemiological investigation using existing short-read whole-genome sequencing data from all carbapenemase-producing Enterobacterales (CPE) from the Danish national surveillance, collected between Jan 1, 2014, and Oct 1, 2023. All confirmed CPE isolates were eligible for inclusion. Using in-silico screening for unique fragments of the two outbreak plasmids, we selected 160 isolates for long-read sequencing to obtain complete plasmid sequences for outbreak investigation. Analyses were descriptive and included comparison of sequence identity and coverage to define outbreak-associated plasmids and summary statistics of patient characteristics. FINDINGS: Data from 1829 isolates were obtained. We detected 16 of 53 isolates involved in the outbreak using conventional outbreak detection methods. The remaining 37 isolates were detected using plasmid-specific screening and long-read sequencing. 15 patients carried the outbreak E hormaechei strain, including the 11 patients previously reported. Three of the 15 patients presented with at least one additional bacterial species carrying one or both outbreak plasmids (pDcap_OXA-48 and pDcap_NDM-5). A further 24 patients, sampled between July 1, 2020, and Oct 1, 2023, presented with other Enterobacterales carrying one or both outbreak-associated plasmids but not the original E hormaechei ST79 strain. In four cases, outbreak-associated plasmids differed structurally from the original outbreak plasmid. INTERPRETATION: This study describes how a clonal CPE outbreak caused by a contaminated medicine evolved into a complex plasmid-mediated outbreak involving multiple Enterobacterales species. Most patients related to the outbreak did not present with the original E hormaechei ST79 outbreak strain and were therefore not identified using standard outbreak detection methods. These findings highlight the importance of using plasmid-focused approaches in outbreak investigations. FUNDING: The Danish Ministry of Health, SSI-Seq (cofunded by EU4Health).

Humans↗
PubMed1979

Stereochemistry of the hydrolysis of the endo isomer of uridine 2',3'-cyclic phosphorothioate catalyzed by the nonspecific phosphohydrolase from Enterobacter aerogenes.

The nonspecific phosphohydrolase from Enterobacter aerogenes (ATCC 13048) requires divalent metal ions for activity, since zinc present in the isolated enzyme can be removed by extensive dialysis against 8-hydroxyquinoline-5-sulfonate at pH 7.5 to yield an inactive enzyme which can be reactivated by addition of Zn2+, Cd2+, Co2+, Mn2+, or Ni2+; six ions of either zinc or cadmium can be incorporated into the inactive enzyme, and this incorporation of metal ion can be correlated with the regaining of activity (J. A. Gerlt, R. Dhesi, and H. C. Hemmings, unpublished experiments). The cadmium-reactivated phosphohydrolase catalyzes the hydrolysis of the endo isomer of uridine 2',3'-cyclic phosphorothioate (U greater than pS) to yield uridine 3'-monophosphorothioate as the major product. After enzymatic hydrolysis of the cyclic phosphorothioate in 19.8% H218O and chemical recyclization of the 18O-labeled acyclic phosphorothioates to yield a mixture of the endo and exo isomers of U greater than pS, 18O is found primarily in the exo isomer, as judged by examination of the 145.7-MHz phosphorus-31 nuclear magnetic resonance spectrum of the mixture. This observation indicates that the cadmium phosphosphohydrolase catalyzes hydrolysis of endo-U greater than pS with inversion of configuration, implying that the hydrolysis reaction proceeds by an in-line attack of water on the phosphorus.

Enterobacter↗
PubMed1979

Competition of beta-lactam antibiotics for the penicillin-binding proteins of Pseudomonas aeruginosa, Enterobacter cloacae, Klebsiella aerogenes, Proteus rettgeri, and Escherichia coli: comparison with antibacterial activity and effects upon bacterial morphology.

The competition of a number of beta-lactam morphogenic probes for the penicillin-binding proteins (PBPs) of Pseudomonas aeruginosa, Enterobacter cloacae, Klebsiella aerogenes, Proteus rettgeri, and Escherichia coli has been studied. The results indicate that the various gram-negative bacteria have similar, but not identical, PBP patterns and that the individual proteins probably perform similar morphogenic functions as in E. coli K-12. Comparison of the 50% binding concentrations of the compounds for the various PBPs of the five strains with their antibacterial activity indicates that the different antibiotics are excluded to a greater or lesser degree by the outer membrane permeability barrier and that the exclusion is most pronounced in P. aeruginosa.

Anti-Bacterial Agents↗
PubMed1979

In vitro response of Enterobacter to ampicillin.

Three strains of Enterobacter were studied for their response to ampicillin. They exhibited a basic level of resistance that depended on the medium used and high-level mutational resistance at a frequency of 10(-5) to 10(-7). Two classes of mutants were selected, one of which showed markedly enhanced antibiotic inactivation as indicated by a biological assay and the other of which resembled the wild type in this regard. Both mutants showed cross-resistance to other beta-lactam antibiotics. The results explained discrepancies between traditional broth dilution minimum inhibitory concentration tests and early read automated procedures.

Ampicillin↗
PubMed1975

Physiological and biochemical role of the butanediol pathway in Aerobacter (Enterobacter) aerogenes.

Aerobacter (Enterobacter) aerogenes wild type and three mutants deficient in the formation of acetoin and 2,3-butanediol were grown in a glucose minimal medium. Culture densities, pH, and diacetyl, acetoin, and 2,3-butanediol levels were recorded. The pH in wild-type cultures dropped from 7.0 to 5.8, remained constant while acetoin and 2,3-butanediol were formed, and increased to pH 6.5 after exhaustion of the carbon source. More 2,3-butanediol than acetoin was formed initially, but after glucose exhaustion reoxidation to acetoin occurred. The three mutants differed from the wild type in yielding acid cultures (pH below 4.5). The wild type and one of the mutants were grown exponentially under aerobic and anaerobic conditions with the pH fixed at 7.0, 5.8, and 5.0, respectively. Growth rates decreased with decreasing pH values. Aerobically, this effect was weak, and the two strains were affected to the same degree. Under anaerobic conditions, the growth rates were markedly inhibited at a low pH, and the mutant was slightly more affected than the wild type. Levels of alcohol dehydrogenase were low under all conditions, indicating that the enzyme plays no role during exponential growth. The levels of diacetyl (acetoin) reductase, lactate dehydrogenase, and phosphotransacetylase were independent of the pH during aerobic growth of the two strains. Under anaerobic conditions, the formation of diacetyl (acetoin) reductase was pH dependent, with much higher levels of the enzyme at pH 5.0 than at pH 7.0. Lactate dehydrogenase and phosphotransacetylase revealed the same pattern of pH-dependent formation in the mutant, but not in the wild type.

Acetates↗
PubMed1979

Purification and characterization of cloacin DF13 receptor from Enterobacter cloacae and its interaction with cloacin DF13 in vitro.

Extraction of the crude cell envelope fraction of cloacin DF13-susceptible Enterobacter cloacae strain 02 with Triton X-100 and ethylenediaminetetraacetate solubilized an outer membrane fraction which neutralized the lethal activity of cloacin DF13. A similar fraction could not be isolated from strains known to be lacking functional cloacin DF13 receptors. On this basis the isolated outer membrane fraction was assumed to contain the specific cloacin DF13 receptor. The receptor was purified to homogeneity by acetone precipitation and affinity chromatography, using cloacin DF13 as a ligand. The purified receptor was identified as a protein which consisted of a single polypeptide chain with an apparent molecular weight of 90,000 and a preponderance of acidic amino acids (pI = 5.0). The interaction of equimolar amounts of purified receptor and cloacin DF13 in vitro resulted in a complete, irreversible neutralization of the lethal activity of the bacteriocin. This interaction showed a temperature optimum at 43 degrees C but was only slightly affected by variation of the pH between 5.0 and 8.5 or by increasing the ionic strength of the incubation buffer. The receptor had no neutralizing activity towards other bacteriocins, such as colicin E1 or colicin E3.

Bacterial Proteins↗
PubMed2026

Genome sequences of six Enterobacter phages of the genus Karamvirus.

Here, we describe the genomes of six Enterobacter bacteriophages (phages) of the genus Karamvirus. The range of genome length, GC content, and number of predicted protein-coding sequences were, respectively, 171,900-175,675 bp, 39.54-39.82%, and 298-316. Genomic analysis indicates that these phages have a lytic lifestyle and are suitable for therapeutic use.

Enterobacter cloacae↗
PubMed2025

Clinical carbapenem-resistant Enterobacterales in a University Hospital in Dakar, Senegal: genomic insights into Enterobacter hormaechei ST182 strains carrying blaNDM-5 and blaOXA-48 genes .

Senegal has witnessed the emergence and spread of carbapenem-resistant Enterobacterales (CRE), which often cause deadly infections. Accordingly, this study aimed to determine the antimicrobial susceptibility and prevalence of carbapenemases, as well as to perform a whole-genome sequence analysis of clinical CRE isolates from a university hospital in Dakar, Senegal. MALDI-TOF MS and VITEK2 systems were used for bacterial identification and antimicrobial susceptibility testing (AST). Carbapenemase- and cephalosporinase-encoding genes were screened using simplex end-point polymerase chain reaction. Whole-genome sequencing (WGS) was performed using the Illumina MiSeq platform. The CRE isolates were resistant to almost all the 34 antimicrobials tested. Nevertheless, colistin and amikacin remained active, with susceptibility rates of 96% and 71%, respectively. Only the carbapenemase genes blaOXA-48 (53.8%; 15/28) and blaNDM (35.7%; 10/28) and the cephalosporinase gene blaCMY-1 (25%; 7/28) were identified. In this context, two extensively drug-resistant Enterobacter hormaechei isolates were subjected to WGS analysis. These isolates were assigned as sequence type (ST) 182 and carried several genes related to antimicrobial resistance (AMR), metal tolerance, and virulence. An IncL/M plasmid with 61,054 bp in length was identified as carrying the blaOXA-48 gene, whereas an IncFIB(pECLA)/IncFII(pECLA)/IncX3 mutireplicon plasmid with 217,745 bp in length was detected as harboring the blaNDM-5 gene and other genes related to AMR and metal tolerance. Our study presents the first landscape of clinical CRE circulating in Senegal, along with additional genomic analysis of E. hormaechei ST182 strains, which could be useful for mitigating the burden associated with CRE in this country.IMPORTANCEThe investigation of global critical priority CRE isolates has become crucial to reduce morbidity and mortality associated with AMR. This study revealed that colistin and amikacin can be considered good alternatives for treating CRE-associated infections in Dakar. In addition, the genomic approach revealed that the CRE isolates carried both a wide resistome and virulome. Moreover, the abundance of horizontal gene transfer regions in the genomes suggests the great implications of mobile genetic elements in the spread of AMR in Dakar. Furthermore, this study reported the complete sequences of chromosomes and blaOXA-48 and blaNDM-5-carrying plasmids. Our findings are of great importance because complete genome sequences are still rarely characterized in the West African region. Finally, this study highlights the importance of strengthening genomic surveillance of CRE in sub-Saharan African countries to mitigate the burden associated with these pathogens.

Senegal↗