Some virulence genes are associated with antibiotic susceptibility in Enterobacter cloacae complex.

BACKGROUND: Enterobacter cloacae complex (ECC) including different species are isolated from different human clinical samples. ECC is armed by many different virulence genes (VGs) and they were also classified among ESKAPE group by WHO recently. The present study was designed to find probable association between VGs and antibiotic susceptibility in different ECC species. METHODS: Forty-five Enterobacter isolates that were harvested from different clinical samples were classified in four different species. Seven VGs were screened by PCR technique and antibiotic susceptibility assessment was performed by disk-diffusion assay. RESULT: Four Enterobacter species; Enterobacter cloacae (33.3%), Enterobacter hormaechei (55.6%), Enterobacter kobei (6.7%) and Enterobacter roggenkampii (4.4%) were detected. Minimum antibiotic resistance was against carbapenem agents and amikacin even in MDR isolates. 33.3% and 13.3% of isolates were MDR and XDR respectively. The rpoS (97.8%) and csgD (11.1%) showed maximum and minimum frequency respectively. Blood sample isolated were highly virulent but less resistant in comparison to the other sample isolates. The csgA, csgD and iutA genes were associated with cefepime sensitivity. CONCLUSION: The fepA showed a predictory role for differentiating of E. hormaechei from other species. More evolved iron acquisition system in E. hormaechei was hypothesized. The fepA gene introduced as a suitable target for designing novel anti-virulence/antibiotic agents against E. hormaechei. Complementary studies on other VGs and ARGs and with bigger study population is recommended.

Effects of Enterobacter cloacae insecticidal protein on the Duox-ROS system and midgut bacterial community and function of Galleria mellonella larvae.

BACKGROUND: Enterobacter cloacae insecticidal proteins have been reported to kill Galleria mellonella larvae through affecting their midgut microbiome. However, the mechanisms involved remain unclear. Here we aim to investigate how the insecticidal proteins act on the midgut Duox-ROS system and microbial community of G. mellonella larvae. METHODS: Reverse transcription qPCR and fluorescence probes were utilized to assess the Duox expression levels and to evaluate quantitative changes of the ROS levels. Sequencing of the 16S rRNA gene sequences of the midgut bacteria of G. mellonella larvae was conducted for further analyses of bacterial diversity, composition, and abundance. RESULTS: After the injection of the insecticidal proteins, the Duox expression levels first increased within 28 h, then dramatically peaked at 36 h, and slowly decreased thereafter. Simultaneously, the ROS levels increased significantly at 36 h, peaked at 48 h, and rapidly declined to the normal level at 60 h. Responsive to the change of the ROS levels, the structure of the midgut microbial community was altered substantially, compared to that of the untreated larvae. The relative abundance of Enterobacteriaceae and other specific pathogenic bacteria increased significantly, whereas that of Lactobacillus decreased sharply. Importantly, notable shifts were observed in the crucial midgut predicted metabolic functions, including membrane transportation, carbohydrate metabolism, and amino acid metabolism. CONCLUSION: Insecticidal proteins of E. cloacae kill G. mellonella larvae mainly through generation of high oxidative stress, alterations of the midgut microbial community and function, and damage to the physiological functions. These findings provide insights into the inhibition mechanism of E. cloacae insecticidal proteins to G. mellonella larvae.

Screening the Rumen of Balochi Camel (Camelus dromedarius) and Cashmere Goat (Capra hircus) to Isolate Enzyme-Producing Bacteria as Potential Additives for Animal Feed.

Rumen microbiology has made a significant contribution to the discovery of biodegradation processes, which convert nutrients into energy for ruminants. Therefore, understanding the enzymatic potential in the rumen of different animal species is essential for developing efficient microbial feed additives. The aim of this study was to isolate enzyme-producing bacteria (EPBs) from the rumen of the Balochi camel (Camelus dromedarius) and Cashmere goat (Capra hircus) as potential additives for animal feed. The EPBs were screened based on the hydrolysis of carboxyl methyl cellulose, tannin, starch, and bovine serum albumin. The isolates were then subjected to enzyme activity assays and molecular characterization. Additionally, they were evaluated for their antagonistic effects, antibiotic susceptibility, and growth in acidic, bile, and saline media. Thirteen enzyme-producing strains were identified in the rumen of the camels and goats, belonging to the genera Klebsiella, Escherichia, Raoultella, Enterobacter and Pectobacterium. The highest and lowest tannase activities were recorded for Escherichia coli GHMGHE41 (10.46 Um/l-1) and Raoultella planticola GHMGHE15 (1.83 Um/l-1), respectively. Enterobacter cloacae GHMGHE18 (2.03 U/ml) was the most effective cellulolytic isolate, compared to Klebsiella strains (1.05 Um/l-1). The highest protease producer was Klebsiella pneumoniae GHMGHE13 (3.00 U/ml-1), while Escherichia coli GHMGHE17 (1.13 U/ml-1) had the lowest activity. Klebsiella pneumoniae GHMGHE13 (1.55 U/ml-1) and Enterobacter cloacae GHMGHE19 (1.26 U/ml-1) were the highest and lowest producers of amylase, respectively. The strains exhibited mixed responses to antibiotics and remained stable under stressful conditions. These findings indicate that ruminal EPBs have the potential to be used in animal feed, pending further in vivo studies.

Enterobacter cloacae-mediated polymer biodegradation: in-silico analysis predicts broad spectrum degradation potential by Alkane monooxygenase.

Plastic pollution poses a significant environmental challenge. In this study, the strain Enterobacter cloacae O5-E, a bacterium displaying polyethylene-degrading capabilities was isolated. Over a span of 30 days, analytical techniques including x-ray diffractometry, scanning electron microscopy, optical profilometry, hardness testing and mass spectrometric analysis were employed to examine alterations in the polymer. Results revealed an 11.48% reduction in crystallinity, a 50% decrease in hardness, and a substantial 25-fold increase in surface roughness resulting from the pits and cracks introduced in the polymer by the isolate. Additionally, the presence of degradational by-products revealed via gas chromatography ascertains the steady progression of degradation. Further, recognizing the pivotal role of alkane monooxygenase in plastic degradation, the study expanded to detect this enzyme in the isolate molecularly. Molecular docking studies were conducted to assess the enzyme's affinity with various polymers, demonstrating notable binding capability with most polymers, especially with polyurethane (- 5.47 kcal/mol). These findings highlight the biodegradation potential of Enterobacter cloacae O5-E and the crucial involvement of alkane monooxygenase in the initial steps of the degradation process, offering a promising avenue to address the global plastic pollution crisis.

Community-acquired multidrug-resistant Enterobacter cloacae sepsis in a 25-month-old child in rural Gambia: A case report.

Enterobacter cloacae is the leading cause of morbidity and mortality in the genus Enterobacter. It mostly causes nosocomial infections, especially in children, the elderly and those with underlying diseases. However, cases of community-acquired bacteraemia caused by E. cloacae have been reported. The increasing inclination of E. cloacae to cause multidrug-resistant infections has made it particularly challenging to treat. A 25-month-old male child presented to a rural hospital in The Gambia with a one-week history of persistent high-grade fever, dyspnoea, and anorexia. Two days before presentation, he began to have generalized tonic-clonic seizures. On examination, he was found to be febrile, dyspnoeic, pale, and tachycardic. He had a modified Glasgow Coma Scale score of 9/15. Investigations revealed an elevated C-reactive protein, low haemoglobin, and elevated white blood cell count. Cerebrospinal fluid culture did not yield any growth. E. cloacae was isolated from a blood culture taken on the day of admission. The pathogen was resistant to all available antibiotics. He was transfused with whole blood and initially treated empirically with amoxicillin-clavulanic acid and gentamicin. The former was changed to cefuroxime because the child had not improved. The child died nine days after admission. Although E. cloacae is primarily known for causing nosocomial infections, fatal community-acquired infections also occur. This case report demonstrates the difficulty in treating multidrug-resistant E. cloacae in a low-resource setting and its propensity to cause fatal infections.

Presence of intracellular bacterial communities in uroepithelial cells, a potential reservoir in symptomatic and non-symptomatic people.

BACKGROUND: Urinary tract infection is one of the most common infections in humans, affecting women in more proportion. The bladder was considered sterile, but it has a urinary microbiome. Moreover, intracellular bacteria (IB) were observed in uroepithelial cells from children and women with urinary tract infections (UTIs). Here, we evaluated the presence of IB in urine from healthy people and patients with UTI symptoms. METHODS: Midstream urine was self-collected from 141 donors, 77 females and 64 males; 72 belonged to the asymptomatic group and 69 were symptomatic. IB was characterized by a culture-dependent technique and visualized by confocal microscopy. Urine was also subjected to the classical uroculture and isolated bacteria were identified by MALDI-TOF. RESULTS: One-hundred and fifteen uroculture were positive. A significant association was observed between the presence of symptoms and IB (P = 0.007). Moreover, a significant association between the presence of IB, symptoms and being female was observed (P = 0.03). From the cases with IB, Escherichia coli was the most frequent microorganism identified (34.7%), followed by Stenotrophomonas maltophilia (14.2%), Staphylococcus spp (14.2%), and Enterococcus faecalis (10.7%). Intracellular E. coli was associated with the symptomatic group (P = 0.02). Most of the intracellular Staphylococcus spp. were recovered from the asymptomatic group (P = 0.006). CONCLUSIONS: Intracellular bacteria are present in patients with UTI but also in asymptomatic people. Here, we report for the first time, the presence of S. maltophilia, Staphylococcus spp., and Enterobacter cloacae as intracellular bacteria in uroepithelial cells. These findings open new insights into the comprehension of urinary tract infections, urinary microbiome and future therapies. Uroculture as the gold standard could not be enough for an accurate diagnosis in recurrent or complicated cases.

A Case of New Delhi Metallo-ß-Lactamase-Producing Enterobacter and a Review of Cases in the United States From January 2009 to September 2022.

Antimicrobial resistance is a growing problem. Novel resistance mechanisms continue to emerge, and the pipeline of antimicrobial development struggles to keep up. Antimicrobial stewardship and proper infection control are key in preventing the spread of these infections. A case of a carbapenem-resistant Enterobacter cloacae complex urinary isolate was identified in an 81-year-old male patient at the San Antonio Veterans Affairs hospital, Texas, USA. The patient was placed on isolation, and further testing of the isolate to other antibiotics requested. The purpose of this study is to analyze the details of reports of such cases and to review at-risk populations and appropriate treatment for resistant organisms.

Exceptional association of two species of bacteria causing acute appendicitis: Haemophilus influenzae and Enterobacter cloacae.

Appendicitis, typically caused by appendiceal lumen obstruction, is a prevalent abdominal surgical emergency worldwide. While most cases involve Enterobacterales, Haemophilus influenzae, primarily known for upper respiratory infections, is infrequently associated with gastrointestinal infections. This article presents an exceptional case of acute appendicitis caused by both Haemophilus influenza and Enterobacter cloacae in a 15-year-old child, highlighting the significance of recognizing uncommon pathogens in appendicitis and emphasizing the necessity for thorough microbiological investigations to refine diagnostic approaches.

Comparative Genomics of an Emerging Multidrug-Resistant blaNDM-Carrying ST182 Lineage in Enterobacter cloacae Complex.

BACKGROUND: Enterobacter cloacae, E. hormaechei and related subspecies remain the most clinically relevant among the Enterobacter cloacae complex (ECC). Carbapenemase-producing ECC strains are increasingly identified in hospital-acquired infections and usually belong to four main multilocus sequence types (MLST STs) named ST114, ST93, ST90 and ST78. Instead, ST182 has been sporadically reported among E. hormaechei strains, and recently, outbreaks of blaNDM-producing ST182 clonal strains have emerged. Herein, we aimed to investigate the presence of ST182 and explore its evolution and modes of blaNDM acquisition. METHODS: A phylogenetic analysis of 646 MLST STs identified among 4685 E. hormaechei whole-genome sequencing (WGS) assemblies deposited in public repositories was performed, as well as an in silico comparative and phylogenomic analyses for 55 WGS assemblies of ST182. blaNDM-harboring contigs were also compared to published plasmid sequences. RESULTS: ST182 E. hormaechei strains were recovered from patients on five continents during 2011-2021. They were divided into three major genomic clusters, comprising a separate clonal complex with six other STs. In 30 out of 55 ST182 WGS assemblies, blaNDM-harboring structures were identified that were similar to the plasmids predominant in Gram-negative bacteria, harboring resistance genes to multiple antibiotic classes and virulence genes. No associations between the genomic clusters and the country/continent of isolation or the presence and the plasmid types of the blaNDM-harboring contigs were observed. CONCLUSIONS: Our findings show that ST182 E. hormaechei strains have been identified in the past decade worldwide; 54.5% of them carried diverse blaNDM genetic structures, suggesting recent acquisition of the blaNDM alleles. Thus, blaNDM-harboring ST182 is an emerging multidrug-resistant and virulent lineage in ECC strains that requires close monitoring.

Dynamic evolution of ceftazidime-avibactam resistance from a single patient through the IncX3_NDM-5 plasmid transfer and blaKPC mutation.

The rapid dissemination of carbapenem-resistant Enterobacterales (CRE) especially carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a great threat to global public health. Ceftazidime-avibactam, a novel ß-lactam/ß-lactamase inhibitor combination, has been widely used due to its excellent antibacterial activity against KPC-producing K. pneumoniae. However, several resistance mechanisms have been reported since its use. Here, we conducted a series of in vitro experiments to reveal and demonstrate the dynamic evolution of ceftazidime-avibactam resistance including interspecies IncX3_NDM-5 plasmid transfer between Enterobacter cloacae and K. pneumoniae and blaKPC mutation from blaKPC-2 to blaKPC-33. Through the analysis of conjugation frequency and fitness cost, the IncX3_NDM-5 plasmid in this study showed strong transmissibility and stability in E. coli EC600 and clinical strain K. pneumoniae 5298 as recipient strain. With increasing ceftazidime-avibactam concentration, the conjugation frequency remained at 10-3-10-5, while the mutation frequency of K. pneumoniae 5298 was 10-6-10-8 at the same concentration. Further plasmid analysis (the IncX3_NDM plasmid from this study and other 658 plasmids from the NCBI database) revealed the diverse origin and genetic structure of blaNDM-5 carrying plasmids. E. coli (42.9%), China (43.9%), IncX3 (66.6%) are the most common strains, regions, and Inc types respectively. By analysing of genetic environment detected in IncX3 plasmids, the dominant structures (168/258, 65.1%) were identified: ISKox3-IS26-blaNDM-5-IS5-ISAba125-Tn3000-Tn3. In additon, several structural variations were found in the core gene structure. In conclusion, the high fitness and transmissibility of the IncX3_NDM-5 plasmids were noteworthy. More importantly, the diverse ceftazidime-avibactam resistance mechanisms including blaNDM-5 tranfer and blaKPC-2 mutation highlighted the importance of the continuous monitoring of antimicrobial susceptibility and carbapenemases subtype during ceftazidime-avibactam treatment.

NagZ modulates the virulence of E. cloacae by acting through the gene of unknown function, ECL_03795.

ß-N-acetylglucosaminidase (NagZ), a cytosolic glucosaminidase, plays a pivotal role in peptidoglycan recycling. Previous research demonstrated that NagZ knockout significantly eradicated AmpC-dependent ß-lactam resistance in Enterobacter cloacae. However, NagZ's role in the virulence of E. cloacae remains unclear. Our study, incorporating data on mouse and Galleria mellonella larval mortality rates, inflammation markers, and histopathological examinations, revealed a substantial reduction in the virulence of E. cloacae following NagZ knockout. Transcriptome sequencing uncovered differential gene expression between NagZ knockout and wild-type strains, particularly in nucleotide metabolism pathways. Further investigation demonstrated that NagZ deletion led to a significant increase in cyclic diguanosine monophosphate (c-di-GMP) levels. Additionally, transcriptome sequencing and RT-qPCR confirmed significant differences in the expression of ECL_03795, a gene with an unknown function but speculated to be involved in c-di-GMP metabolism due to its EAL domain known for phosphodiesterase activity. Interestingly, in ECL_03795 knockout strains, a notable reduction in the virulence was observed, and virulence was rescued upon complementation with ECL_03795. Consequently, our study suggests that NagZ's function on virulence is partially mediated through the ECL_03795→c-di-GMP pathway, providing insight into the development of novel therapies and strongly supporting the interest in creating highly efficient NagZ inhibitors.

A Rare Case of Gas Forming Enterobacter cloacae Leading to Bleeding Mycotic Pseudoaneurysm of Transplant Renal Artery Culminating in Graft Nephrectomy.

Enterobacter cloacae belongs to Enterobacter genus. It is a common gram-negative, facultative anaerobic, rod-shaped organism. It causes a variety of nosocomial infections including urinary tract infection, pneumonia, wound infection, osteomyelitis and endocarditis. Over time Enterobacter cloacae complex (ECC) has developed to be resistant to antibiotics including carbapenem. It has been rarely reported to cause gas gangrene and never been reported to cause pseudoaneurysm (PA) of transplant renal artery. We report and share our experience with this rare case of gas forming and muti-drug resistant ECC which led to mycotic PA of transplant renal artery, complicated by bleeding and infected hematoma and which resulted in graft nephrectomy.

IMI-Type Carbapenemase-Producing Enterobacter cloacae Complex, France and Overseas Regions, 2012-2022.

We characterized a collection of IMI-like-producing Enterobacter spp. isolates (n = 112) in France. The main clone corresponded to IMI-1-producing sequence type 820 E. cloacae subspecies cloacae that was involved in an outbreak. Clinicians should be aware of potential antimicrobial resistance among these bacteria.

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.

Transcriptomic analysis of induced resistance to polymyxin in carbapenem-resistant Enterobacter cloacae complex isolate carrying mcr-9.

OBJECTIVES: Polymyxins are currently the last-resort treatment against multi-drug resistant Gram-negative bacterial infections, but plasmid-mediated mobile polymyxin resistance genes (mcr) threaten its efficacy, especially in carbapenem-resistant Enterobacter cloacae complex (CRECC). The objective of this study was to provide insights into the mechanism of polymyxin-induced bacterial resistance and the effect of overexpression of mcr-9. METHODS: The clinical strain CRECC414 carrying the mcr-9 gene was treated with a gradient concentration of polymyxin. Subsequently, the broth microdilution was used to determine the minimum inhibitory concentration (MIC) and RT-qPCR was utilized to assess mcr-9 expression. Transcriptome sequencing and whole genome sequencing (WGS) was utilized to identify alterations in strains resulting from increased polymyxin resistance, and significant transcriptomic differences were analysed alongside a comprehensive examination of metabolic networks at the genomic level. RESULTS: Polymyxin treatment induced the upregulation of mcr-9 expression and significantly elevated the MIC of the strain. Furthermore, the WGS and transcriptomic results revealed a remarkable up-regulation of arnBCADTEF gene cassette, indicating that the Arn/PhoPQ system-mediated L-Ara4N modification is the preferred mechanism for achieving high levels of resistance. Additionally, significant alterations in bacterial gene expression were observed with regards to multidrug efflux pumps, oxidative stress and repair mechanisms, cell membrane biosynthesis, as well as carbohydrate metabolic pathways. CONCLUSION: Polymyxin greatly disrupts the transcription of vital cellular pathways. A complete PhoPQ two-component system is a prerequisite for polymyxin resistance of Enterobacter cloacae, even though mcr-9 is highly expressed. These findings provide novel and important information for further investigation of polymyxin resistance of CRECC.

In vitro and in vivo activity of ceftazidime/avibactam and aztreonam alone or in combination against mcr-9, serine- and metallo-ß-lactamases-co-producing carbapenem-resistant Enterobacter cloacae complex.

PURPOSE: Enterobacteriaceae carrying mcr-9, in particularly those also co-containing metallo-ß-lactamase (MBL) and TEM type ß-lactamase, present potential transmission risks and lack adequate clinical response methods, thereby posing a major threat to global public health. The aim of this study was to assess the antimicrobial efficacy of a combined ceftazidime/avibactam (CZA) and aztreonam (ATM) regimen against carbapenem-resistant Enterobacter cloacae complex (CRECC) co-producing mcr-9, MBL and TEM. METHODS: The in vitro antibacterial activity of CZA plus ATM was evaluated using a time-kill curve assay. Furthermore, the in vivo interaction between CZA plus ATM was confirmed using a Galleria mellonella (G. mellonella) infection model. RESULTS: All eight clinical strains of CRECC, co-carrying mcr-9, MBL and TEM, exhibited high resistance to CZA and ATM. In vitro time-kill curve analysis demonstrated that the combination therapy of CZA + ATM exerted significant bactericidal activity against mcr-9, MBL and TEM-co-producing Enterobacter cloacae complex (ECC) isolates with a 100% synergy rate observed in our study. Furthermore, in vivo survival assay using Galleria mellonella larvae infected with CRECC strains co-harboring mcr-9, MBL and TEM revealed that the CZA + ATM combination significantly improved the survival rate compared to the drug-treatment alone and untreated control groups. CONCLUSION: To our knowledge, this study represents the first report on the in vitro and in vivo antibacterial activity of CZA plus ATM against CRECC isolates co-harboring mcr-9, MBL and TEM. Our findings suggest that the combination regimen of CZA + ATM provides a valuable reference for clinicians to address the increasingly complex antibiotic resistance situation observed in clinical microorganisms.

Carbapenem-Resistant Enterobacter cloacae Complex in Southwest China: Molecular Characteristics and Risk Factors Caused by NDM Producers.

Purpose: The isolation rate of carbapenem-resistant Enterobacter cloacae complex (CREC) is continuously increasing. The aims of this study were to investigate the molecular characteristics and risk factors associated with CREC infections. Methods: Bacterial species were identified using the matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) (Bruker Daltonik GmbH, Bremen, Germany), and the hsp60 gene was utilized for further typing. Antimicrobial susceptibilities were assessed through the MicroScan WalkAway 96 Plus system (Siemens, Germany) and the microbroth dilution method. Antimicrobial resistance genes were screened through polymerase chain reaction (PCR), while the homologous relationship was assessed using multilocus sequence typing (MLST). Conjugation experiments were performed to verify whether the plasmid could be transferred. Additionally, logistic regression model was employed to analyze risk factors for CREC infections. Results: 32 strains of CREC bacteria were isolated during the study, yet only 20 were retained for preservation. While the isolates demonstrated resistance to the majority of antibiotics, they exhibited high sensitivity to polymyxin B and tigecycline. All isolates carried the blaNDM resistance gene, including 13 blaNDM-1 isolates and 7 blaNDM-5 isolates. MLST homology analysis revealed the presence of seven known ST types and one new ST type. Conjugation experiments confirmed that 13 isolates were capable of transferring the blaNDM resistance gene to Escherichia coli strain EC600. Single-factor analysis identified multiple primary risk factors for CREC infection, but multivariate analysis did not reveal independent risk factors. Conclusion: This study investigates the molecular characteristics and risk factors associated with CREC infections. The detection rate of CREC strains in our hospital is continuously rising and homology analysis suggested that strains might spread in our hospital, emphasizing the importance of implementing effective preventive measures to control the horizontal transmission of plasmid-mediated antimicrobial resistance genes.

Clinical Characteristics, Prognosis and Treatment of Bloodstream Infections with Enterobacter Cloacae Complex in a Chinese Tertiary Hospital: A Retrospective Study.

Objective: This research aimed to analyze the clinical characteristics, prognosis, and antimicrobial treatment of bloodstream infections (BSI) caused by Enterobacter cloacae complex (ECC). Methods: The clinical data of patients with bloodstream infections caused by Enterobacter cloacae complex from April 2017 to June 2023 were collected retrospectively. These data were then analyzed in subgroups based on the detection results of extended-spectrum ß-lactamase (ESBL), 30-day mortality, and the type of antimicrobial agent used (ß-lactam/ß-lactamase inhibitor combinations (BLICs) or carbapenems). Results: The proportion of ESBL-producing Enterobacter cloacae complex was 32.5% (37/114). Meanwhile, ICU admission, receiving surgical treatment within 3 months, and biliary tract infection were identified as risk factors for ESBL-producing ECC-BSI. Additionally, immunocompromised status and Sequential Organ Failure Assessment (SOFA) score ≥ 6.0 were identified as independent risk factors of 30-day mortality in patients with ECC-BSI (n = 108). Further analysis in BSI patients caused by non-ESBL-producing ECC revealed that patients treated with BLICs (n = 45) had lower SOFA scores and lower incidence of hypoproteinemia and sepsis compared with patients treated with carbapenems (n = 20). Moreover, in non-ESBL-producing ECC-BSI patients, the univariate Cox regression analysis indicated a significantly lower 30-day mortality rate in patients treated with BLICs compared to those treated with carbapenems (hazard ratios (HR) [95% CI] 0.190 [0.055-0.662], P = 0.009; adjusted HR [95% CI] 0.106 [0.013-0.863], P = 0.036). Conclusion: This study investigated the factors influencing the susceptibility to infection by ESBL-producing strains and risk factors for 30-day mortality in ECC-BSI patients. The results revealed that ESBL-negative ECC-BSI patients treated with BLICs exhibited significantly lower 30-day mortality compared to those treated with carbapenems. BLICs were found to be more effective in ECC-BSI patients with milder disease (ESBL-negative and SOFA ≤6.0).

Genomic and biological characterization of bacteriophages against Enterobacter cloacae, a high-priority pathogen.

Enterobacter cloacae is a clinically significant pathogen due to its multi-resistance to antibiotics, presenting a challenge in the treatment of infections. As concerns over antibiotic resistance escalate, novel therapeutic approaches have been explored. Bacteriophages, characterized by their remarkable specificity and ability to self-replicate within target bacteria, are emerging as a promising alternative therapy. In this study, we isolated and partially characterized nine lytic bacteriophages targeting E. cloacae, with two selected for comprehensive genomic analysis based on their host range and bacteriolytic activity. All identified phages exhibited a narrow host range, demonstrated stability within a temperature range of 30-60 °C, displayed pH tolerance from 3 to 10, and showed an excellent bacteriolytic capacity for up to 18 h. Notably, the fully characterized phage genomes revealed an absence of lysogenic, virulence, or antibiotic-resistance genes, positioning them as promising candidates for therapeutic intervention against E. cloacae-related diseases. Nonetheless, translating this knowledge into practical therapeutic applications mandates a deeper understanding of bacteriophage interactions within complex biological environments.

The nucleoid protein HU positively regulates the expression of type VI secretion systems in Enterobacter cloacae.

Enterobacter cloacae is an emerging pathogen isolated in healthcare-associated infections. A major virulence factor of this bacterium is the type VI secretion system (T6SS). The genome of E. cloacae harbors two T6SS gene clusters (T6SS-1 and T6SS-2), and the functional characterization of both systems showed that these two T6SSs are not expressed under the same conditions. Here, we report that the major histone-like protein HU positively regulates the expression of both T6SSs and, therefore, the function that each T6SS exerts in E. cloacae. Single deletions of the genes encoding the HU subunits (hupA and hupB) decreased mRNA levels of both T6SS. In contrast, the hupA hupB double mutant dramatically affected the T6SS expression, diminishing its transcription. The direct binding of HU to the promoter regions of T6SS-1 and T6SS-2 was confirmed by electrophoretic mobility shift assay. In addition, single and double mutations in the hup genes affected the ability of inter-bacterial killing, biofilm formation, adherence to epithelial cells, and intestinal colonization, but these phenotypes were restored when such mutants were trans-complemented. Our data broaden our understanding of the regulation of HU-mediated T6SS in these pathogenic bacteria. IMPORTANCE: T6SS is a nanomachine that functions as a weapon of bacterial destruction crucial for successful colonization in a specific niche. Enterobacter cloacae expresses two T6SSs required for bacterial competition, adherence, biofilm formation, and intestinal colonization. Expression of T6SS genes in pathogenic bacteria is controlled by multiple regulatory systems, including two-component systems, global regulators, and nucleoid proteins. Here, we reported that the HU nucleoid protein directly activates both T6SSs in E. cloacae, affecting the T6SS-related phenotypes. Our data describe HU as a new regulator involved in the transcriptional regulation of T6SS and its impact on E. cloacae pathogenesis.