Bacteria can synthesize a broad spectrum of multifunctional polysaccharides including extracellular polysaccharides (EPS). Bacterial EPS can be utilized in the food, pharmaceutical, and biomedical areas owing to their physical and rheological properties in addition to generally presenting low toxicity. From an ecological viewpoint, EPS are biodegradable and environment compatible, offering several advantages over synthetic compounds. This study investigated the EPS produced by Klebsiella oxytoca (KO-EPS) by chemically characterizing and evaluating its properties. The monosaccharide components of the KO-EPS were determined by HPLC coupled with a refractive index detector and GC-MS. The KO-EPS was then analyzed by methylation analysis, FT-IR and NMR spectroscopy to give a potential primary structure. KO-EPS demonstrated the ability to stabilize hydrophilic emulsions with various hydrophobic compounds, including hydrocarbons and vegetable and mineral oils. In terms of iron chelation capacity, the KO-EPS could sequester 41.9 % and 34.1 % of the most common iron states, Fe2+ and Fe3+, respectively. Moreover, KO-EPS exhibited an improvement in the viscosity of aqueous dispersion, being proportional to the increase in its concentration and presenting a non-Newtonian pseudoplastic flow behavior. KO-EPS also did not present a cytotoxic effect indicating that the KO-EPS could have potential applications as a natural thickener, bioemulsifier, and bioremediation agent.

UNASSIGNED: Klebsiella oxytoca (K. oxytoca) is the second bacterial cause of nosocomial infections in the general population after K. pneumoniae. This study surveyed the frequency of cytotoxin-producing strains of K. oxytoca and their antibiotic susceptibility profile in a cohort of children admitted to a referral hospital with different malignancies.
UNASSIGNED: The Stool samples of children admitted to the Cancer Chemotherapy Unit of the Mofid Children\'s Hospital, Tehran, Iran were analyzed using conventional biochemical tests and polymerase chain reaction targeting the pehX gene to identify K. oxytoca. The antibiotic susceptibility profile of isolated K. oxytoca against commonly prescribed antibiotics used in treating infection at the facility was determined using the Kirby-Bauer disk diffusion technique. Also, the prevalence of genes encoding toxins among K. oxytoca was identified by PCR assay.
UNASSIGNED: The Stool samples of 280 participants were taken for the study of which 38 samples [(55.3% (21/38) 42 males and 44.7% (17/38) females)] tested positive for various Klebsiella spp. Out of this, K. oxytoca was identified in 2.5% (7/280) stools using cultures and conventional biochemical tests. Also, the stools of 2.9% (8/280) of the participants tested positive for K. oxytoca using PCR assay. Using PCR, (2/7) of the K. oxytoca isolates tested positive for the npsA and npsB genes and were identified as toxigenic K. oxytoca strains.
UNASSIGNED: The prevalence of toxin-producing K. oxytoca strains in stool samples of children diagnosed with cancer in Iran is relatively low. Most of the K. oxytoca isolates were susceptible to tested antibiotics. Globally, active surveillance of toxigenic K. oxytoca strains in patients with different malignancies or immunocompromised patients is recommended in healthcare settings.

BACKGROUND: We report the case of a 76-year-old male who was hospitalized with severe dehydration, pain in the hepatic region, and weakness in the limbs.
METHODS: A contrast-enhanced abdomen CT and a contrast-enhanced ultrasound identified a large liver abscess. The patient underwent percutaneous drainage of the abscess.
RESULTS: The culture examination, analyzed by multiplex polymerase chain reaction test, showed the presence of Klebsiella oxytoca. The laboratory report identified a resistance mechanism involving a plasmid-mediated SHV-1 extended-spectrum-beta-lactamase (ESBL).
CONCLUSIONS: K. oxytoca is a Gram-negative bacterium and is potentially associated with a large variety of infections. The association between the liver abscess by K. oxytoca and rhabdomyolysis had not yet been described in the literature.

Sugarcane bagasse (SCB) was utilized for efficiently producing optically pure D-(-)-lactate by Klebsiella oxytoca KIS004-91T strain. Cellulase (15 U/g NaOH-treated SCB) sufficiently liberated high sugars with saccharifications of 79.8 % cellulose and 52.5 % hemicellulose. For separated hydrolysis and fermentation, D-(-)-lactate was produced at 53.5 ± 2.1 g/L (0.98 ± 0.01 g/g sugar utilized or 0.71 ± 0.01 g/g total sugars) while D-(-)-lactate at 47.2 ± 1.8 g/L (0.78 ± 0.03 g/g sugar used or 0.69 ± 0.01 g/g total sugars) was obtained under simultaneous saccharification and fermentation (SSF). D-(-)-lactate at 99.9 ± 0.9 g/L (0.97 ± 0.01 g/g sugar utilized or 0.78 ± 0.01 g/g total sugars) was improved via fed-batch SSF. Based on mass balance, raw SCB of 7 kg is required to produce 1 kg D-(-)-lactate. Unlike others, D-(-)-lactate production was performed in low-cost salt medium without requirements of rich nutrients. Costs regarding medium, purification, and waste disposal may be reduced. This unlocks economic capability of SCB bioconversion or agricultural and agro-industrial wastes into high valuable D-(-)-lactate.

Klebsiella oxytoca KP001-TF60 (ΔadhEΔpta-ackAΔldhAΔbudABΔpflBΔtdcDΔpmd) was re-engineered to direct more carbon flux towards succinate production with less acetate. Glucose uptake, cell growth, and carbon distribution were restricted by alterations in relative expressions and nucleotide sequences of genes associated with PEP and pyruvate metabolisms. Transcripts of pck, ppc, and frd genes were up-regulated for enhancing NADH reoxidation during succinate production while increased pyk and tdcE transcripts were observed due to maintenance of acetyl-CoA through the oxidative branch of TCA cycle. Based on whole-genome sequencing, several genes in sugars-specific PTS (ptsG, bglF, chbR, fruA, mtlR, and treY), ABC transporters (alsK, and rbsK), Major Facilitator Superfamily (uhpB and setB), and catabolite repression (cyaA and csrB) were found to be mutated. The strain produced succinate yield up to 0.89 g/g (∼80 % theoretical maximum) with acetate < 1 g/L, and may be one of the succinate producers applied in an industrial-production scale with simplified purification processes.

The Klebsiella oxytoca complex comprises diverse opportunistic bacterial pathogens associated with hospital and community-acquired infections with growing alarming antimicrobial resistance. We aimed to uncover the genomic features underlying the virulence and antimicrobial resistance of isolates from Mulago National Hospital in Uganda. We coupled whole genome sequencing with Pathogenwatch multilocus sequence typing (MLST) and downstream bioinformatic analysis to delineate sequence types (STs) capsular polysaccharide K- and O-antigen loci, along with antimicrobial resistance (AMR) profiles of eight clinical isolates from the National Referral Hospital of Uganda. Our findings revealed that only two isolates (RSM6774 and RSM7756) possess a known capsular polysaccharide K-locus (KL74). The rest carry various unknown K-loci (KL115, KL128, KLI52, KL161 and KLI63). We also found that two isolates possess unknown loci for the lipopolysaccharide O-antigen (O1/O2v1 type OL104 and unknown O1). The rest possess known O1 and O3 serotypes. From MLST, we found four novel sequence types (STs), carrying novel alleles for the housekeeping genes glyceraldehyde-6-phosphate dehydrogenase A (gapA), glucose-6-phosphate isomerase (pgi), and RNA polymerase subunit beta (rpoB). Our AMR analysis revealed that all the isolates are resistant to ampicillin and ceftriaxone, with varied resistance to other antibiotics, but all carry genes for extended-spectrum beta-lactamases (ESBLs). Notably, one strain (RSM7756) possesses outstanding chromosomal and plasmid-encoded AMR to beta-lactams, cephalosporins, fluoroquinolones and methoprims. Conclusively, clinical samples from Mulago National Referral Hospital harbor novel STs and multidrug resistant K. oxytoca strains, with significant public health importance, which could have been underrated.

UNASSIGNED: Raoultella spp. is a genus of bacteria that is known to be closely related to Klebsiella. It has been debated whether Raoultella should be reclassified as a subgroup of Klebsiella. The aim of this study is to compare clinical aspects of Raoultella and Klebsiella oxytoca, a species of Klebsiella that is known to be bacteriologically similar to Raoultella spp.
UNASSIGNED: Using data collected at a tertiary care hospital in the United States, we identified 43 patients with Raoultella infection and 1173 patients with Klebsiella oxytoca infection. We compared patient demographics (age and sex), hospitalization status, isolation sites and antibiotic resistance profiles between the two species.
UNASSIGNED: There was no significant difference in patient demographics between the two bacteria species. The proportions of intensive care unit (ICU) admission were higher among patients with Raoultella infection (p=0.008). The most common site of isolation was urine for both species (39.5% of all patients with Raoultella spp. vs. 59.3% for K. oxytoca). The second most common site of isolation was blood stream for Raoultella spp. (23.3%) and respiratory tract for K. oxytoca (10.8%). Except for the high proportion of resistant isolates of Raoultella spp. for Trimethoprim/sulfamethoxazole, the antibiotic susceptibility profiles were similar between the two bacteria species. Both were susceptible to ciprofloxacin and meropenem.
UNASSIGNED: While there are no significant differences in the patient demographics and antibiotic susceptibility profiles between Raoultella spp. and K. oxytoca, Raoultella may cause more serious infection requiring ICU admissions. Also, Raoultella may cause blood stream infection more frequently than K. oxytoca.

The Klebsiella oxytoca species complex is part of the human microbiome, especially during infancy and childhood. K. oxytoca species complex strains can produce enterotoxins, namely, tilimycin and tilivalline, while also contributing to colonization resistance (CR). The relationship between these seemingly contradictory roles is not well understood. Here, by coupling ex vivo assays with CRISPR-mutagenesis and various mouse models, we show that K. oxytoca provides CR against Salmonella Typhimurium. In vitro, the antimicrobial activity against various Salmonella strains depended on tilimycin production and was induced by various simple carbohydrates. In vivo, CR against Salmonella depended on toxin production in germ-free mice, while it was largely toxin-independent in mice with residual microbiota. This was linked to the relative levels of toxin-inducing carbohydrates in vivo. Finally, dulcitol utilization was essential for toxin-independent CR in gnotobiotic mice. Together, this demonstrates that nutrient availability is key to both toxin-dependent and substrate-driven competition between K. oxytoca and Salmonella.

The environmental bacterium Klebsiella oxytoca displays an alarming increase of antibiotic-resistant strains that frequently cause outbreaks in intensive care units. Due to its prevalence in the environment and opportunistic presence in humans, molecular surveillance (including resistance marker screening) and high-resolution cluster analysis are of high relevance. Furthermore, K. oxytoca previously described in studies is rather a species complex (KoSC) than a single species comprising at least six closely related species that are not easily differentiated by standard typing methods. To reach a discriminatory power high enough to identify and resolve clusters within these species, whole genome sequencing is necessary. The resolution is achievable with core genome multilocus sequence typing (cgMLST) extending typing of a few housekeeping genes to thousands of core genome genes. CgMLST is highly standardized and provides a nomenclature enabling cross laboratory reproducibility and data exchange for routine diagnostics. Here, we established a cgMLST scheme not only capable of resolving the KoSC species but also producing reliable and consistent results for published outbreaks. Our cgMLST scheme consists of 2,536 core genome and 2,693 accessory genome targets, with a percentage of good cgMLST targets of 98.31% in 880 KoSC genomes downloaded from the National Center for Biotechnology Information (NCBI). We also validated resistance markers against known resistance gene patterns and successfully linked genetic results to phenotypically confirmed toxic strains carrying the til gene cluster. In conclusion, our novel cgMLST enables highly reproducible typing of four different clinically relevant species of the KoSC and thus facilitates molecular surveillance and cluster investigations.

Klebsiella spp. are causative agents of healthcare-associated infections in patients who are immunocompromised and use medical devices. The antibiotic resistance crisis has led to an increase in infections caused by these bacteria, which can develop into potentially life-threatening illnesses if not treated swiftly and effectively. Thus, new treatment options for Klebsiella are urgently required. Phage therapy can offer an alternative to ineffective antibiotic treatments for antibiotic-resistant bacteria infections. The aim of the present study was to produce a safe and effective phage cocktail treatment against Klebsiella pneumoniae and Klebsiella oxytoca, both in liquid in vitro culture and an in vivo Galleria mellonella infection model. The phage cocktail was significantly more effective at killing K. pneumoniae and K. oxytoca strains compared with monophage treatments. Preliminary phage cocktail safety was demonstrated through application in the in vivo G. mellonella model: where the phage cocktail induced no toxic side effects in G. mellonella. In addition, the phage cocktail significantly improved the survival of G. mellonella when administered as a prophylactic treatment, compared with controls. In conclusion, our phage cocktail was demonstrated to be safe and effective against Klebsiella spp. in the G. mellonella infection model. This provides a strong case for future treatment for Klebsiella infections, either as an alternative or adjunct to antibiotics.IMPORTANCEKlebsiella infections are a concern in individuals who are immunocompromised and are becoming increasingly difficult to treat with antibiotics due to their drug-resistant properties. Bacteriophage is one potential alternative therapy that could be used to tackle these infections. The present study describes the design of a non-toxic phage cocktail that improved the survival of Galleria mellonella infected with Klebsiella. This phage cocktail demonstrates potential for the safe and effective treatment of Klebsiella infections, as an adjunct or alternative to antibiotics.