Enterobacter Aerogenes Research Articles

Assessing the quality of drinking water from selected water sources in Mbarara city, South-western Uganda.

This study assessed the physical, chemical, and microbiological quality with emphasis on risk score, source apportionment, geochemistry, feacal coliforms and water quality index of drinking water from selected water sources. A cross-sectional study was conducted in six villages in Mbarara city, south-western Uganda. Each selected source was inspected using a WHO-adopted sanitary inspection questionnaire. Each source's risk score was calculated. Thirty-seven samples were taken from one borehole, nine open dug wells, four rain harvest tanks, and twenty-three taps. The values for apparent color and phosphate were higher than the permissible level as set by the World Health Organization and Ugandan standards (US EAS 12). The isolated organisms were Klebsiella spp. (8.11%), Citrobacter divergens (62.16%), Citrobacter fluendii (2.7%), E. coli (35.14%), Enterobacter aerogenes (8.11%), Enterobacter agglomerus (5.4%), Proteus spp. (2.7%), Enterobacter cloacae (13.5%), and Proteus mirabilis (2.7%). Twelve water sources (32.4%) had water that was unfit for human consumption that was unfit for human consumption (Grade E), Five sources (13.5%) had water that had a very poor index (Grade D), nine (24.3%) had water of poor index (Grade C), eight (21.6%) had water of good water index (Grade B), and only three (8.1%) had water of excellent water quality index (Grade A). The piper trilinear revealed that the dominant water type of the area were Mgso4 and Caso4 type. Gibbs plot represents precipitation dominance. PCA for source apportionment showed that well, tap and borehole water account for the highest variations in the quality of drinking water. These results suggest that drinking water from sources in Mbarara city is not suitable for direct human consumption without treatment. We recommend necessary improvements in water treatment, distribution, and maintenance of all the available water sources in Mbarara City, South Western Uganda.

Phylogenetic Analysis of Bacterial Isolates Recovered from Salt-affected Soils of Haryana & Punjab, India

Excessive saline/alkaline conditions present a significant challenge to the environment and ecology, impacting yield, plant growth, and soil health. This study focuses on isolating and characterizing halophilic bacteria from salt-affected areas in Haryana and Punjab, India. Morphological, biochemical, and molecular analyses were conducted to assess their potential as plant growth-promoting rhizobacteria (PGPR) for mitigating salt stress in salt-affected soils. Four bacterial strains, identified as HR3-PM, PB01-KB, PB-424, and PB-466, were isolated and characterized. Morphological and biochemical assays revealed diverse traits among the isolates, including phosphate solubilization, indole-3-acetic acid (IAA) production, and ammonia excretion. Molecular identification via 16S rRNA sequencing confirmed their taxonomic classification and revealed close homology to known bacterial species such as Klebsiella aerogenes, Pseudomonas mosselii, Lysinibacillus acetophenoni, and Pseudomonas stutzeri. Phylogenetic analysis provided insights into their evolutionary relationships. These salt-tolerant bacteria exhibit promising PGPR activities, suggesting their potential for sustainable agriculture and soil remediation practices in salt-affected soils. Harnessing their abilities could offer cost-effective and environmentally friendly solutions to mitigate soil salinity, enhance plant productivity, and contribute to global environmental stresses. Further research is warranted to fully understand and harness the biotechnological potential of these halophilic bacteria in salt-affected ecosystems, paving the way for a more sustainable environmental future.

ANTIMICROBIAL POTENCY AND PHYTOCHEMICAL CONTENTS OF THREE COMMON NIGERIA MEDICINAL PLANTS’ LEAF EXTRACTS

Morinda lucida, Tithonia diversifolia and Carica papaya are three medicinal plants commonly used for curing several diseases in traditional medicine. However, comparative scientific information as regards their antibacterial, antifungal, and phytochemical properties remains limited. Fresh leaves of Morinda lucida, Tithonia diversifolia, and Carica papaya were harvested and extracted by soaking pulverized samples of the plants in 250 mL of water and ethanol. The phytochemical constituents were determined by subjecting the decoction to qualitative and quantitative tests using standard methods. The antimicrobial and antifungal activities were determined by solidified Mueller-Hinton agar plate and solidified Potato Dextrose agar plate respectively. Alkaloids, flavonoids, saponins, tannins, and terpenoids were shown to be the primary metabolites in the ethanolic extract of the three plant species. Cardiac glycosides are only present in T. diversifolia. Aqueous and ethanolic leaf extracts of the three species had significant, but varying antibacterial activity and no antifungal properties. Ethanolic extracts of Morinda lucida were the most active against Escherichia coli with a 30 mm zone of inhibition and very active against Klebsiella pneumonia and Enterobacter aerogenes with 28 mm and 24 mm zone of inhibition, respectively. The aqueous extracts of T. diversifolia were more active against Staphylococcus aureus, Serratia marscences, and Enterobacter aerogenes than ethanolic extract. The ethanolic decoction of C. papaya was active against Enterococci. This study showed that depending on the decoction solvent and the microbes under investigation, the leaf extracts of the three plant species have a tolerable but variable level of activity.

PRELIMINARY EVALUATION OF ANTIBIOTIC SUSCEPTIBILITY PATTERNS OF PATHOGENS ISOLATED FROM PRIVATE LABORATORY SPECIMENS IN UKRAINE

Objective. This study aims at conducting an analysis of data on antibiotic resistance to antimicrobials that were obtained for the period from April 28, 2018, to December 31, 2019, in a private laboratory in the city of Kharkiv. Materials and methods. We conducted an investigation into the identification and analysis of antimicrobial sensitivity for isolates obtained from patients at a private clinic in the city of Kharkiv from 2018 to 2019. Results. The analysis revealed that patients most frequently sought bacteriological examination for materials from the throat (34.5%) and nose (29.9%), while the least common requests were for examination of the mucous membrane of the oral cavity (2.3%) and skin (3.4%). The positive results accounted for 94.3% of the cases. The isolated strains included Staphylococcus aureus (29.4%), Neisseria spp. (16.5%), Staphylococcus epidermidis (14.1%), Streptococcus spp. of the Viridans group (12.9%), Candida albicans (5.9%), Moraxella spp. (1.2%), Streptococcus anhaemolyticus, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa (each constituting 3.5%), molds (2.4%), and Streptococcus haemolyticus, Enterobacter aerogenes, and Enterococcus faecalis (each accounting for 1.2%). The isolated strains obtained from patients of the private laboratory had a pronounced antibiotic resistance to antimicrobial drugs of the following groups: beta-lactams, tetracycline, aminoglycosides, and sulfonamides. This should be taken into account by doctors when prescribing antibacterial therapy. Conclusions. The data indicate disturbingly high levels of antimicrobial resistance in isolates collected from patients at a private clinic in the city of Kharkiv.

Gut permeability among Astronauts during Space missions

The space environment poses substantial challenges to human physiology, including potential disruptions in gastrointestinal health. Gut permeability has only recently become widely acknowledged for its potential to cause adverse effects on a systemic level, rendering it a critical factor to investigate in the context of spaceflight. Here, we propose that astronauts experience the onset of leaky gut during space missions supported by transcriptomic and metagenomic analysis of human and murine samples. A genetic map contributing to intestinal permeability was constructed from a systematic review of current literature. This was referenced against our re-analysis of three independent transcriptomic datasets which revealed significant changes in gene expression patterns associated with the gut barrier. Specifically, in astronauts during flight, we observed a substantial reduction in the expression genes that are crucial for intestinal barrier function, goblet cell development, gut microbiota modulation, and immune responses. Among rodent spaceflight studies, differential expression of cytokines, chemokines, and genes which regulate mucin production and post-translational modifications suggest a similar dysfunction of intestinal permeability. Metagenomic analysis of feces from two murine studies revealed a notable reduction probiotic, short chain fatty acid-producing bacteria and an increase in the Gram-negative pathogens, including Citrobacter rodentium, Enterobacter cloacea, Klebsiella aerogenes, and Proteus hauseri which promote LPS circulation, a recipe for barrier disruption and systemic inflammatory activation. These findings emphasize the critical need to understand the underlying mechanisms and develop interventions to maintain gastrointestinal health in space.

Study of disinfectant activity against bee pathogenic enterobacteria in vitro

Dysbiosis is a pathological condition caused by violating the normal coexistence of bacterial organisms in one or more body systems. This disease arises due to the action of many ethological factors, the mechanisms of which arise from each other. Klebsiellosis of bee colonies is a relatively new disease of Apis mellifera, caused by pathogenic enterobacteria, which leads to the mass death of bees with signs of acute dyspepsia, particularly in the spring and autumn periods. To prevent klebsiellosis in bees, it is necessary to carry out veterinary and sanitary measures in apiaries every year, including disinfection. Modern beekeeping encourages the search for new antibacterial drugs to ensure the production technology of safe and high-quality beekeeping products suitable for sale. Preliminary laboratory assessment (in vitro) of the effectiveness of disinfectants against specific pathogens of specific diseases of bees will ensure an increase in the effectiveness of such agents in apiaries, which is economically effective for practical beekeeping. The purpose of the research was to determine the activity of different concentrations of the disinfectant (0.25 %, 0.5 %, 1.25 %, 2.5 %) with an active substance of an organic nature with covalent weakly polar bonds against pure cultures of pathogenic enterobacteria of bees of the species Klebsiella pneumoniae and Klebsiella (Enterobacter) aerogenes in vitro. The modified Kirby-Baur method on Mueller-Hinton agar was used for research. A bactericidal effect against a pure culture of Klebsiella pneumoniae species was registered after 24 hours with lysis zone diameters at 8.6 ± 0.27 mm (0.25 % concentration) – 15.0 ± 0.35 mm (2.5 % concentration). On the 3rd day of research, a bacteriostatic effect was registered with the largest diameter of the zone of growth retardation (24.4 ± 0.27 mm) at 2.5 % disinfectant concentration. Bactericidal and bacteriostatic effects were recorded on the culture of enterobacteria of bees of the species Klebsiella (Enterobacter) aerogenes for 24 hours of cultivation with zones of lysis – 6.8 ± 0.42 mm (0.25 %) – 11.8 ± 0.22 mm (2.5 %) and inhibition of bacterial growth at the level of – 21.8 ± 0.42 mm (0.25 %) – 25.8 ± 0.42 mm (2.5 %). At the same time, there was no significant difference between the zones of Klebsiella (Enterobacter) aerogenes growth retardation in concentrations of 0.5 % – 2.5 % on the 3rd day of research. The studied disinfectant has bactericidal and bacteriostatic effects on pure cultures of bee enterobacteria of the species Klebsiella pneumoniae and Klebsiella (Enterobacter) aerogenes in laboratory conditions, which is promising for further study of the drug.

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 β-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.

Impact of water quality on reprocessing equipment: Assessment of neurosurgical instruments cleaning and biofilm formation in hospital pipes.

The presence of contamination and microorganisms at any stage of processing renders a method unsafe, leading to a high risk of cross-transmission and cross-infection. The objective of this study was to assess the cleaning quality of aspirator instruments used in neurosurgical procedures. The experimental study was conducted at the materials and sterilization center, as well as the microbiology laboratory, of a philanthropic hospital in Brazil. A study protocol was implemented, which involved the analysis of 10 samples of Yasargil aspirators with varying dimensions. The samples were subjected to protein tests to detect the presence of organic matter and microbiological analysis. Descriptive statistics were used to analyze the data. The results indicated that 40% of the instruments tested positive for protein after manual cleaning. Furthermore, after automated cleaning, samples showed an increased microbiological load, with Escherichia coli accounting for 20% and Klebsiella aerogenes for 10% of the identified microorganisms. This study provides evidence of failures in the cleaning process of healthcare products and highlights the presence of biofilm in the pipes, thereby compromising the drinking water quality standard.

Inhibition of Aflatoxin Production in Aspergillus flavus by a Klebsiella sp. and Its Metabolite Cyclo(l-Ala-Gly).

During an experiment where we were cultivating aflatoxigenic Aspergillus flavus on peanuts, we accidentally discovered that a bacterium adhering to the peanut strongly inhibited aflatoxin (AF) production by A. flavus. The bacterium, isolated and identified as Klebsiella aerogenes, was found to produce an AF production inhibitor. Cyclo(l-Ala-Gly), isolated from the bacterial culture supernatant, was the main active component. The aflatoxin production-inhibitory activity of cyclo(l-Ala-Gly) has not been reported. Cyclo(l-Ala-Gly) inhibited AF production in A. flavus without affecting its fungal growth in a liquid medium with stronger potency than cyclo(l-Ala-l-Pro). Cyclo(l-Ala-Gly) has the strongest AF production-inhibitory activity among known AF production-inhibitory diketopiperazines. Related compounds in which the methyl moiety in cyclo(l-Ala-Gly) is replaced by ethyl, propyl, or isopropyl have shown much stronger activity than cyclo(l-Ala-Gly). Cyclo(l-Ala-Gly) did not inhibit recombinant glutathione-S-transferase (GST) in A. flavus, unlike (l-Ala-l-Pro), which showed that the inhibition of GST was not responsible for the AF production-inhibition of cyclo(l-Ala-Gly). When A. flavus was cultured on peanuts dipped for a short period of time in a dilution series bacterial culture broth, AF production in the peanuts was strongly inhibited, even at a 1 × 104-fold dilution. This strong inhibitory activity suggests that the bacterium is a candidate for an effective biocontrol agent for AF control.

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

The dissemination of New Delhi metallo-β-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. 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. The KA3 strain belongs to ST4 and shows high resistance to β-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). Continued monitoring for the dissemination of blaNDM-5 among uncommon Enterobacterales species should be further reinforced.

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.

Antibacterial Agent of Echinochloa esculenta-Mediated ZnO Nanoparticles on Urinary Infection-Causing Bacteria

Background: Echinochloa esculenta is the Indian Barnyard millet which is a grass type of species. This study focused on the evaluation of the antibacterial activity of Echinochloa esculenta-mediated zinc oxide nanoparticles (ZnONPs) against urinary tract infection (UTI) microbes, such as Escherichia coli (E. coli), Enterobacter aerogenes, Pseudomonas aeruginosa, Staphylococcus aureus, and Proteus vulgaris. Methods: The millet Echinochloa esculenta-mediated ZnONPs are synthesized using a green method. Synthesized ZnONPs are characterized by ultraviolet (UV), Fourier transform-infrared resonance spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX) to determine the functional groups, crystalline size, shape, and elemental composition of the synthesized NPs. Results: The UV and FTIR results of Echinochloa esculenta-mediated ZnONPs preliminarily confirmed the formation of ZnONPs. The XRD and SEM results also confirmed that the synthesized ZnONPs are well-crystalline in nature, and the average size was observed to be 23.38 nm with a spherical shape. Echinochloa esculenta-mediated ZnONPs contained 73.33% of zinc and 26.77% of oxygen, which was examined by EDX. Synthesized ZnONPs were tested against the five UTI pathogens, and they exhibited a greater zone of inhibitions than zinc acetate and plant extract. Especially against S. aureus, Echinochloa esculenta-mediated ZnONPs performed well with an inhibitory effect. Conclusions: Therefore, this study had the potential value of developing new eco-friendly, low-cost, and less toxic nanomaterials that can be used as a bio-control for diseases.

Differences in microorganisms causing infection after cranial and spinal surgeries.

The primary aim of this retrospective study was to assess differences in the pathogens causing surgical site infections (SSIs) following craniectomies/craniotomies and open spinal surgery. The secondary aim was to assess differences in rates of SSI among these operative procedures. ANOVA tests with Bonferroni correction and incidence risk ratios (RRs) were used to identify differences in pathogens by surgical site and procedure using retrospective, de-identified records of 19,993 postneurosurgical patients treated between 2007 and 2020. The overall infection rates for craniotomy/craniectomy, laminectomy, and fusion were 2.1%, 1.1%, and 1.5%, respectively, and overall infection rates for cervical, thoracic, and lumbar spine surgery were 0.3%, 1.6%, and 1.9%, respectively. Craniotomy/craniectomy was more likely to result in an SSI than spine surgery (RR 1.8, 95% CI 1.4-2.2, p < 0.0001). Cutibacterium acnes (RR 24.2, 95% CI 7.3-80.0, p < 0.0001); coagulase-negative staphylococci (CoNS) (methicillin-susceptible CoNS: RR 2.9, 95% CI 1.6-5.4, p = 0.0006; methicillin-resistant CoNS: RR 5.6, 95% CI 1.4-22.3, p = 0.02); Klebsiella aerogenes (RR 6.5, 95% CI 1.7-25.1, p = 0.0003); Serratia marcescens (RR 2.4, 95% CI 1.1-7.1, p = 0.01); Enterobacter cloacae (RR 3.1, 95% CI 1.2-8.1, p = 0.02); and Candida albicans (RR 3.9, 95% CI 1.2-12.3, p = 0.02) were more commonly associated with craniotomy/craniectomy cases than fusion or laminectomy SSIs. Pseudomonas aeruginosa was more commonly associated with fusion SSIs than craniotomy SSIs (RR 4.4, 95% CI 1.3-14.8, p = 0.02), whereas Escherichia coli was nonsignificantly associated with fusion SSIs compared to craniotomy SSIs (RR 4.1, 95% CI 0.9-18.1, p = 0.06). Infections with E. coli and P. aeruginosa occurred primarily in the lumbar spine (p = 0.0003 and p = 0.0001, respectively). SSIs due to typical gastrointestinal or genitourinary gram-negative bacteria occur most commonly following lumbar surgery, particularly fusion, and are likely to be due to contamination of the surgical bed with microbial flora in the perianal area and genitourinary tract. Cutibacterium acnes in the skin flora of the head and neck increases risk of infection due to this microbe following surgical interventions in these body sites. The types of gram-negative bacteria associated with craniotomy/craniectomy SSIs suggest potential environmental sources of these pathogens. Based on the authors' findings, neurosurgeons should consider using a two-step skin preparation with benzoyl peroxide, in addition to a standard antiseptic such as alcoholic chlorhexidine for cranial, cervical, and upper thoracic surgeries. Additionally, broader gram-negative bacterial coverage, such as use of a third-generation cephalosporin, should be considered for lumbar/lumbosacral fusion surgical antibiotic prophylaxis.

Biological Degradation of Natural Rubber Glove by Gram-negative Bacteria Klebsiella aerogenes

Biological Degradation of Natural Rubber Glove by Gram-negative Bacteria Klebsiella aerogenes

Microbiocidal Studies of Some Azo Dyes

Microbiocidal potential of some azo dyes has been studied. Polydentate azo dyes viz. 1-(2’-carbo xyphenylazo)-2-naphthol, 5-(2’-carboxyphenylazo)-8-hydroxyquinoline, 5-(2’-carboxyphenylazo)salicylic acid and 4-(2’-carboxyphenylazo)resorcinol were synthesized and characterized by elemental analysis, infrared (FTIR) and 1H NMR spectral studies. The dyes were screened for antibacterial sensitivities against the Gram positive bacteria Staphylococcus aureus and Gram negative bacteria Enterobacter aerogenes and Escherichia coli at four concentrations of the dyes viz. 0.5, 1.0, 1.5 and 2.0 mg/ml, in acetone. Results revealed a high to low potency of the dyes as antibacterials. 5-(2’-carboxyphenylazo)salicylic acid and 4-(2’-carboxyphenylazo) resorcinol in the concentration range of 1 to 2mg/ml, were found to be more potent in inhibiting the bacterial growth uniformly towards all the three bacteria. A possible role of salicylate or resorcinol moieties, in addition to azo group of these dyes in their higher microbiocidal activities may be envisaged. These azo dyes may, thus, be of medicinal value.

Transcriptomic analysis of nitrogen metabolism pathways in Klebsiella aerogenes under nitrogen-rich conditions.

The acceleration of the nitrogen cycle and the nitrogen excess observed in some coastal waters has increased interest into understanding the biochemical and molecular basis of nitrogen metabolism in various microorganisms. To investigate nitrogen metabolism of a novel heterotrophic nitrification and aerobic denitrification bacterium Klebsiella aerogenes strain (B23) under nitrogen-rich conditions, we conducted physiological and transcriptomic high-throughput sequencing analyses on strain B23 cultured on potassium nitrate-free or potassium nitrate-rich media. Overall, K. aerogenes B23 assimilated 82.47% of the nitrate present into cellular nitrogen. Further, 1,195 differentially expressed genes were observed between K. aerogenes B23 cultured on potassium nitrate-free media and those cultured on potassium nitrate-rich media. Gene annotation and metabolic pathway analysis of the transcriptome were performed using a series of bioinformatics tools, including Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and Non-Redundant Protein Database annotation. Accordingly, the nitrogen metabolism pathway of K. aerogenes B23 was analyzed; overall, 39 genes were determined to be involved in this pathway. Differential expression analysis of the genes involved in the nitrogen metabolism pathway demonstrated that, compared to the control, FNR, NarK/14945, fdx, gshA, proB, proA, gapA, argH, artQ, artJ, artM, ArgR, GAT1, prmB, pyrG, glnS, and Ca1 were significantly upregulated in the nitrogen-treated K. aerogenes B23; these genes have been established to be involved in the regulation of nitrate, arginine, glutamate, and ammonia assimilation. Further, norV, norR, and narI were also upregulated in nitrogen-treated K. aerogenes B23; these genes are involved in the regulation of NO metabolism. These differential expression results are important for understanding the regulation process of key nitrogen metabolism enzyme genes in K. aerogenes B23. Therefore, this study establishes a solid foundation for further research into the expression regulation patterns of nitrogen metabolism-associated genes in K. aerogenes B23 under nitrogen-rich conditions; moreover, this research provides essential insight into how K. aerogenes B23 utilizes nutritional elements.

Evaluation of predictors of third-generation cephalosporin non-susceptibility and factors affecting recurrence or death in bacteremia caused by Citrobacter freundii complex, Enterobacter cloacae complex, and Klebsiella aerogenes

Factors involved in the susceptibility of third-generation cephalosporins (3GCs) to bacteremia caused by Citrobacter freundii complex, Enterobacter cloacae complex, and Klebsiella aerogenes were investigated based on a case-case-control design. Antimicrobial therapy administered 30 days prior to bacteremia and hospitalization within 90 days were common risk factors for the 3GC susceptible and 3GC non-susceptible groups, while hospitalization from an institution or another hospital was a specific risk factor for the 3GC non-susceptible group. We also attempted to examine the factors affecting the clinical outcome of bacteremia. Hospitalization more than 14 days before the onset of bacteremia was an independent factor indicating poor clinical outcome. In contrast, the implementation of source control was an independent predictor of successful treatment. Although a longer hospital stay before the onset of bacteremia was associated with worse clinical outcomes, implementation of source control may have contributed to improved treatment outcomes for bacteremia.

Enterobacterales carrying chromosomal AmpC β-lactamases in Europe (EuESCPM): Epidemiology and antimicrobial resistance burden from a cohort of 27 hospitals, 2020–2022

IntroductionThe ESCPM group (Enterobacter species including Klebsiella aerogenes - formerly Enterobacter aerogenes, Serratia species, Citrobacter freundii complex, Providencia species and Morganella morganii) has not yet been incorporated into systematic surveillance programs. MethodsWe conducted a multicentre retrospective observational study analysing all ESCPM strains isolated from blood cultures in 27 European hospitals over a 3-year period (2020–2022). Diagnostic approach, epidemiology, and antimicrobial susceptibility were investigated. ResultsOur study comprised 6,774 ESCPM isolates. MALDI-TOF coupled to mass spectrometry was the predominant technique for bacterial identification. Susceptibility to new β-lactam/β-lactamase inhibitor combinations and confirmation of AmpC overproduction were routinely tested in 33.3% and 29.6% of the centres, respectively. The most prevalent species were E. cloacae complex (44.8%) and S. marcescens (22.7%). Overall, third-generation cephalosporins (3GC), combined third- and fourth-generation cephalosporins (3GC + 4GC) and carbapenems resistance phenotypes were observed in 15.7%, 4.6%, and 9.5% of the isolates, respectively. AmpC overproduction was the most prevalent resistance mechanism detected (15.8%). Among carbapenemase-producers, carbapenemase type was provided in 44.4% of the isolates, VIM- (22.9%) and OXA-48-enzyme (16%) being the most frequently detected. E. cloacae complex, K. aerogenes and Providencia species exhibited the most notable cumulative antimicrobial resistance profiles, with the former displaying 3GC, combined 3GC + 4GC and carbapenems resistance phenotypes in 15.2%, 7.4%, and 12.8% of the isolates, respectively. K. aerogenes showed the highest rate of both 3GC resistant phenotype (29.8%) and AmpC overproduction (32.1%), while Providencia species those of both carbapenems resistance phenotype (42.7%) and carbapenemase production (29.4%). ESCPM isolates exhibiting both 3GC and combined 3GC + 4GC resistance phenotypes displayed high susceptibility to ceftazidime/avibactam (98.2% and 95.7%, respectively) and colistin (90.3% and 90.7%, respectively). Colistin emerged as the most active drug against ESCPM species (except those intrinsically resistant) displaying both carbapenems resistance phenotype (85.8%) and carbapenemase production (97.8%). ConclusionsThis study presented a current analysis of ESCPM species epidemiology in Europe, providing insights to inform current antibiotic treatments and guide strategies for antimicrobial stewardship and diagnostics.

The importance of meropenem resistance, rather than imipenem resistance, in defining carbapenem-resistant Enterobacterales for public health surveillance: an analysis of national population-based surveillance

BackgroundIn Japan, carbapenem-resistant Enterobacterales (CRE) infections were incorporated into the National Epidemiological Surveillance of Infectious Diseases (NESID) in 2014, necessitating mandatory reporting of all CRE infections cases. Subsequently, pathogen surveillance was initiated in 2017, which involved the collection and analysis of CRE isolates from reported cases to assess carbapenemase gene possession. In this surveillance, CRE is defined as (i) minimum inhibitory concentration (MIC) of meropenem ≥2 mg/L (MEPM criteria) or (ii) MIC of imipenem ≥2 mg/L and MIC of cefmetazole ≥64 mg/L (IPM criteria). This study examined whether the current definition of CRE surveillance captures cases with a clinical and public health burden.MethodsCRE isolates from reported cases were collected from the public health laboratories of local governments, which are responsible for pathogen surveillance. Antimicrobial susceptibility tests were conducted on these isolates to assess compliance with the NESID CRE definition. The NESID data between April 2017 and March 2018 were obtained and analyzed using antimicrobial susceptibility test results.ResultsIn total, 1681 CRE cases were identified during the study period, and pathogen surveillance data were available for 740 (44.0%) cases. Klebsiella aerogenes and Enterobacter cloacae complex were the dominant species, followed by Klebsiella pneumoniae and Escherichia coli. The rate of carbapenemase gene positivity was 26.5% (196/740), and 93.4% (183/196) of these isolates were of the IMP type. Meanwhile, 315 isolates were subjected to antimicrobial susceptibility testing. Among them, 169 (53.7%) fulfilled only the IPM criteria (IPM criteria-only group) which were susceptible to meropenem, while 146 (46.3%) fulfilled the MEPM criteria (MEPM criteria group). The IPM criteria-only group and MEPM criteria group significantly differed in terms of carbapenemase gene positivity (0% vs. 67.8%), multidrug resistance rates (1.2% vs. 65.8%), and mortality rates (1.8% vs 6.9%).ConclusionThe identification of CRE cases based solely on imipenem resistance has had a limited impact on clinical management. Emphasizing resistance to meropenem is crucial in defining CRE, which pose both clinical and public health burden. This emphasis will enable the efficient allocation of limited health and public health resources and preservation of newly developed antimicrobials.

First report of coexistence of blaKPC-2 and blaNDM-1 in carbapenem-resistant clinical isolates of Klebsiella aerogenes in Brazil.

Klebsiella aerogenes is an important opportunistic pathogen with the potential to develop resistance against last-line antibiotics, such as carbapenems, limiting the treatment options. Here, we investigated the antibiotic resistance profiles of 10 K. aerogenes strains isolated from patient samples in the intensive-care unit of a Brazilian tertiary hospital using conventional PCR and a comprehensive genomic characterization of a specific K. aerogenes strain (CRK317) carrying both the blaKPC-2 and blaNDM-1 genes simultaneously. All isolates were completely resistant to β-lactam antibiotics, including ertapenem, imipenem, and meropenem with differencing levels of resistance to aminoglycosides, quinolones, and tigecycline also observed. Half of the strains studied were classified as multidrug-resistant. The carbapenemase-producing isolates carried many genes of interest including: β-lactams (blaNDM-1, blaKPC-2, blaTEM-1, blaCTX-M-1 group, blaOXA-1 group and blaSHVvariants in 20-80% of the strains), aminoglycoside resistance genes [aac(6')-Ib and aph(3')-VI, 70 and 80%], a fluoroquinolone resistance gene (qnrS, 80%), a sulfonamide resistance gene (sul-2, 80%) and a multidrug efflux system transporter (mdtK, 70%) while all strains carried the efflux pumps Acr (subunit A) and tolC. Moreover, we performed a comprehensive genomic characterization of a specific K. aerogenes strain (CRK317) carrying both the blaKPC-2 and blaNDM-1 genes simultaneously. The draft genome assembly of the CRK317 had a total length of 5,462,831 bp and a GC content of 54.8%. The chromosome was found to contain many essential genes. In silico analysis identified many genes associated with resistance phenotypes, including β-lactamases (blaOXA-9, blaTEM-1, blaNDM-1, blaCTX-M-15, blaAmpC-1, blaAmpC-2), the bleomycin resistance gene (bleMBL), an erythromycin resistance methylase (ermC), aminoglycoside-modifying enzymes [aac(6')-Ib, aadA/ant(3")-Ia, aph(3')-VI], a sulfonamide resistance enzyme (sul-2), a chloramphenicol acetyltransferase (catA-like), a plasmid-mediated quinolone resistance protein (qnrS1), a glutathione transferase (fosA), PEtN transferases (eptA, eptB) and a glycosyltransferase (arnT). We also detected 22 genomic islands, eight families of insertion sequences, two putative integrative and conjugative elements with a type IV secretion system, and eight prophage regions. This suggests the significant involvement of these genetic structures in the dissemination of antibiotic resistance. The results of our study show that the emergence of carbapenemase-producing K. aerogenes, co-harboring blaKPC-2 and blaNDM-1, is a worrying phenomenon which highlights the importance of developing strategies to detect, prevent, and control the spread of these microorganisms.