Virulence Factors in Hypervirulent Klebsiella pneumoniae

Characterization and genomic insights into bacteriophages Kpph1 and Kpph9 against hypervirulent carbapenem-resistant Klebsiella pneumoniae

The increasing incidence of infections attributed to hypervirulent carbapenem-resistant Klebsiella pneumoniae (Hv-CRKp) is of considerable concern. Bacteriophages, also known as phages, are viruses that specifically infect bacteria; thus, phage-based therapies offer promising alternatives to antibiotic treatments targeting Hv-CRKp infections. In this study, two isolated bacteriophages, Kpph1 and Kpph9, were characterized for their specificity against the Hv-CRKp K. pneumoniae NUHL30457 strain that possesses a K2 capsule serotype. Both phages exhibit remarkable environmental tolerance, displaying stability over a range of pH values (4-11) and temperatures (up to 50°C). The phages demonstrate potent antibacterial and antibiofilm efficacy, as indicated by their capacity to inhibit biofilm formation and to disrupt established biofilms of Hv-CRKp. Through phylogenetic analysis, it has been revealed that Kpph1 belongs to the new species of Webervirus genus, and Kpph9 to the Drulisvirus genus. Comparative genomic analysis suggests that the tail fiber protein region exhibits the greatest diversity in the genomes of phages within the same genus, which implies distinct co-evolution histories between phages and their corresponding hosts. Interestingly, both phages have been found to contain two tail fiber proteins that may exhibit potential depolymerase activities. However, the exact role of depolymerase in the interaction between phages and their hosts warrants further investigation. In summary, our findings emphasize the therapeutic promise of phages Kpph1 and Kpph9, as well as their encoded proteins, in the context of research on phage therapy targeting hypervirulent carbapenem-resistant Klebsiella pneumoniae.

Identification of a novel phage depolymerase against ST11 K64 carbapenem-resistant Klebsiella pneumoniae and its therapeutic potential

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a clinical pathogen with a high mortality rate, and its clinical management and infection control have become a serious challenge. Phage-encoded depolymerase cleaves the capsular polysaccharide, a major virulence factor of K. pneumoniae. This study aimed to identify a phage depolymerase targeting ST11 K64 CRKP, evaluate its antimicrobial activity and therapeutic efficacy, and provide new alternative therapeutic strategies for K64 CRKP. Phages were screened from untreated hospital sewage using clinically isolated CRKP as the host bacterium. The host range, efficiency of plaque formation, optimal multiplicity of infection, adsorption efficiency, and one-step growth curve of phage vB_KpnP_IME1309 were determined by the double-layer agar plate culture method. The morphology of the phage was observed by transmission electron microscopy. Phage nucleic acids were extracted for whole-genome sequencing, and the phage-encoded depolymerase gene ORF37 was amplified by polymerase chain reaction. Next, a recombinant plasmid was constructed to induce depolymerase expression, which was verified using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In vitro bactericidal activity was determined using a combined serum assay, and the anti-K. pneumoniae biofilm effect of depolymerase was determined by crystal violet staining. Finally, a Galleria mellonella larvae infection model was established to investigate the therapeutic effect of depolymerase on larvae in vivo. Here, we isolated and characterized a phage vB_KpnP_IME1309 targeting ST11 K64 CRKP, which featured a latent period of 20 min and a burst size of approximately 290 plaque-forming units/cell. It contained 41 predicted open reading frames, of which ORF37 encoded depolymerase. The expressed and purified depolymerase Dep37 cleaved only ST11 K64 CRKP and formed a translucent halo on the agar plate. Dep37 increased the susceptibility of K. pneumoniae B1 to serum killing, inhibited CRKP biofilm formation, and degraded mature biofilms. The combination of Dep37 and kanamycin was significantly more effective in treating CRKP biofilms compared to either Dep37 or kanamycin alone. An injection of Dep37 at 5 min and 2 h after the CRKP infection of Galleria mellonella larvae increased their survival rates by up to 73% and 53%, respectively. Depolymerase Dep37 may be used as a potential method for capsule typing of K. pneumoniae, showing great promise for the development of novel alternative therapeutic strategies against ST11 K64 CRKP.

IMPORTANCE

A novel phage vB_KpnP_IME1309 targeting ST11 K64 carbapenem-resistant Klebsiella pneumoniae (CRKP) was isolated and characterized. The ORF37 encoding depolymerase gene of phage vB_KpnP_IME1309 was successfully expressed and purified. Depolymerase increases the susceptibility of CRKP to serum killing, inhibits CRKP biofilm formation, and degrades mature biofilms. The combination of depolymerase and kanamycin is significantly more effective than either depolymerase or kanamycin alone in the treatment of CRKP biofilm. Depolymerase injection at 5 min and 2 h after CRKP infection of Galleria mellonella larvae increased the survival rate of larvae by up to 73% and 53%, respectively. Depolymerase Dep37 may be used as a method for the development of novel alternative therapeutic strategies against ST11 K64 CRKP.

New insights and perspectives on the virulence of hypervirulent Klebsiella pneumoniae

Klebsiella pneumoniae, a Gram-negative bacterium, comprises strains with diverse virulence potentials, ranging from classical to hypervirulent variants. Understanding the genetic basis underlying the virulence disparities between hypervirulent (hvKp) and classical K. pneumoniae (cKp) strains is crucial. hvKp strains are characterized by hypermucoviscosity, attributed to the presence of specific virulence genes and the production of molecules that aid in their ability to survive, evade host immune defenses, and cause infection. In contrast, classical strains exhibit a broader array of antimicrobial resistance determinants, conferring resistance to multiple antibiotics. Although current definitions of hvKp incorporate clinical features, phenotypes, and genotypes, identifying hvKp strains in clinical settings remains challenging. Genomic studies have been pivotal and have helped to identify distinct genetic profiles in hvKp strains, including unique virulence plasmids and chromosomal variations, underscoring the genetic diversity within K. pneumoniae populations. This review examines the virulence and genetic determinants associated with hvKp. The presence of genes defining hypervirulence, alongside considerations of their utility as biomarkers and targets for therapeutic strategies, is discussed, while also providing insight into biofilm formation by hvKp and key questions that need urgent responses in understanding hvKp.

Molecular epidemiology and emergence of sequence type 25 hypervirulent Klebsiella pneumoniae in pigs in the Netherlands (2013-2020): a global comparative analysis with human and pig isolates

Klebsiella pneumoniae (Kp), a ubiquitous pathogen found in diverse ecological niches, poses a threat to human and animal health. Hypervirulent Kp (hvKp) is concerning for its acquisition of virulence and antimicrobial resistance genes through plasmids. This study investigates hvKp as a cause of septicaemia in piglets in the Netherlands and examines the role of plasmids in virulence and host association. We collected 41 Kp isolates cultured from necropsies submitted from 15 different farms (2013-2020) and sequenced them using long-read sequencing. We identified sequence type (ST) 25 as the dominant Kp (67%, 10/15 farms) associated with septicaemia in pigs in the Netherlands. ST25 isolates displayed a hypervirulent profile, including the K2 hyper-capsule type and carried an iuc3 virulence plasmid. Further analysis revealed two ST25 clonal groups: CG25 and CG3804, a novel porcine clone. Multidrug resistance was identified in CG25 isolates from five pig farms. There was one colistin-resistant isolate carrying mcr-1 on a plasmid. Comparative genomic analysis was performed by including a large dataset of related publicly available Kp genomes from ST25 humans (n=230) and pigs (n=12) of all STs for phylogenetic and plasmid analysis. Pangenomic analysis revealed significantly higher iuc3 prevalence in global CG25 pig isolates (98%, 40/41) compared to humans (10%, 24/234) correlating with their enhanced virulence (scores 3-4 vs 0-1). The study highlights ST25 hvKp causing septicaemia in piglets in the Netherlands for the first time. Aerobactin lineage iuc3 on a plasmid is associated with infections in pigs and is responsible for an increased virulence score.

Multidrug-resistant hypervirulent Klebsiella pneumoniae: an evolving superbug

Multidrug-resistant hypervirulent Klebsiella pneumoniae (MDR-hvKP) combines high pathogenicity with multidrug resistance to become a new superbug. MDR-hvKP reports continue to emerge, shattering the perception that hypervirulent K. pneumoniae (hvKP) strains are antibiotic sensitive. Patients infected with MDR-hvKP strains have been reported in Asia, particularly China. Although hvKP can acquire drug resistance genes, MDR-hvKP seems to be more easily transformed from classical K. pneumoniae (cKP), which has a strong gene uptake ability. To better understand the biology of MDR-hvKP, this review discusses the virulence factors, resistance mechanisms, formation pathways, and identification of MDR-hvKP. Given their destructive and transmissible potential, continued surveillance of these organisms and enhanced control measures should be prioritized.

The First Report on the Structure of Polysaccharide Surface Antigens of the Clinical Klebsiella oxytoca 0.062 Strain and the Contribution in the Serological Cross-Reactions

Klebsiella oxytoca bacilli co-form the human intestinal microbiota, but in favorable conditions, they may also affect immunocompromised individuals, causing urinary tract infections, bacteremia, or antibiotic-associated hemorrhagic colitis. The growing numbers of clinical outbreaks of K. oxytoca infections make these bacteria an emerging pathogen, which is still masked by the predominant K. pneumoniae isolates. Thus, it is very important to advance knowledge on K. oxytoca pathogenicity. This work aims to characterize a urine isolate, K. oxytoca 0.062, from central Poland, which appears to present a multidrug-resistant and extended-spectrum β-lactamases-positive phenotype. The structural experiments include sugar and methylation analyses, mass spectrometry, and 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy. Additionally, 1H,1H ROESY, and 1H,13C HMBC experiments were carried out on the high-molecular-weight O polysaccharide fraction of K. oxytoca lipopolysaccharides (LPSs). These analyses led to the detection of two polysaccharide antigens: one neutral, containing a linear trisaccharide unit called mannan, and one acidic, which is built up of a branched tetrasaccharide unit containing two mannopyranose (α-Manp) residues, one galactopyranose (β-Galp) residue, and one galacturonic acid (α-GalpA) residue. The GalpA residue seems to be a potential minor epitope, recognized by the selected Proteus antisera in the serological studies.

Antibacterial Activity of Ocimum tenuiflorum against Drug Resistant Bacteria Isolated from Raw Beef

Recent empirical evidence has acknowledged raw meat, particularly beef, as a significant reservoir for diverse foodborne pathogens and drug-resistant strains, posing severe threat to consumer health. This study aimed to isolate and identify drug-resistant bacteria from raw beef samples, obtained from different butcher shops in Khulna city, Bangladesh, as well as, to determine their susceptibility pattern against Ocimum tenuiflorum extracts. Raw beef samples were randomly collected from various butcher shops, followed by the initial isolation of thirty pure bacterial isolates. Later, 16S rRNA gene amplification and analysis identified twelve distinct bacterial species from those isolates. The antimicrobial susceptibility test results revealed ten of the isolates, including Klebsiella pneumoniae, Aeromonas veronii and Enterobacter hormaechei, to exhibit multidrug resistance pattern. Amoxicillin, nitrofurantoin, and flucloxacillin were found to be ineffective against most isolates. However, the ethanolic extracts of O. tenuiflorum were found effective in inhibiting the growth of eight species at three different concentrations. Subsequent HPLC analysis of O. tenuiflorum reported the presence of five secondary metabolites epicatechin, syringic acid, rutin hydrate, p-coumaric acid, and myricetin as potent contributors to the observed antimicrobial activity. Lastly, in silico binding interaction simulations of the secondary metabolites against five relevant targets predict syringic acid and myricetin to have effective antibacterial properties, primarily mediated by better binding affinity and molecular interactions. Thus, this study identified diverse drug-resistant bacteria in raw beef and provided novel insights into the antibacterial properties of O. tenuiflorum extracts.

Computational design of a fimbriae-derived multi-epitope vaccine candidate against Klebsiella pneumoniae

Klebsiella pneumoniae is a pathogen that causes infections in various parts of the body, with high mortality rates reported in antibiotic-resistant cases. Treating at-risk individuals requires crucial vaccination efforts due to the challenges that exist. This research involved designing a multi-epitope vaccine from K. pneumoniae's fimbriae antigens. Optimal T-cell and B-cell epitopes were chosen through in silico studies including epitope-HLAs molecular docking. The multi-epitope was created, featuring antigenic T- and B-cell epitopes, β-defensin as an adjuvant, the PADRE sequence to boost immunogenicity and well-suited linkers. The tertiary structure of the multi-epitope was achieved through modeling and molecular dynamics-based refinements. The construct underwent scrutiny for structural traits, physicochemical properties, conformational B epitope prediction, immune responses simulation, in silico cloning, molecular docking for assay binding to toll-like receptors (TLRs), and deformability studies. The outcomes indicated the vaccine candidate's positive attributes, encompassing immunogenicity, structure, physicochemical properties, solubility, TLR binding, toxicity, stability, allergenicity, and cross-reactivity. The multi-epitope vaccine candidate exhibits the potential for provoking diverse immune responses against K. pneumoniae. Nevertheless, additional in vitro and in vivo experimental tests are necessary to substantiate its efficacy.

Bacteriophage-derived depolymerase: a review on prospective antibacterial agents to combat Klebsiella pneumoniae

Klebsiella pneumoniae is a Gram-negative bacterium that colonizes mucosal surfaces and is a common cause of nosocomial infections. The emergence of antimicrobial resistance in K. pneumoniae, particularly carbapenem-resistant strains, poses a significant threat to human health, with high mortality rates and healthcare costs. Another major problem is that hypervirulent K. pneumoniae tends to form biofilms. Bacteriophage-derived depolymerases, a class of enzymes that degrade diverse bacterial surface carbohydrates, have been exploited as antibiofilm and antimicrobial adjuvants because of their high stability, specificity, strong antimicrobial activity, and low incidence of bacterial resistance. This review presents a summary of the structure and properties of depolymerase, as well as an overview of both in vitro and in vivo studies of depolymerase therapy for multidrug-resistant or biofilm-forming K. pneumoniae infections. These studies employed a range of approaches, including utilizing a single depolymerase or combinations of depolymerase and phages or antibiotics. Furthermore, this review outlines the current challenges facing depolymerase therapy and potential future approaches for treating K. pneumoniae infections.

Prevalence and Virulence Profiles of Klebsiella pneumoniae Isolated From Different Animals

BACKGROUND

Klebsiella pneumoniae liver abscess (KLA) is an invasive disease, and the occurrence of infection is related to its virulence factors and colonization of the host's gastrointestinal (GI) tract. Some animal-sourced isolates share virulence factors with human pathogens. However, the potential of K. pneumoniae as a zoonotic agent has not been confirmed in murine infection model.

OBJECTIVES

To identify the prevalence and virulence profiles of K. pneumoniae colonization in companion and wild animals and subsequently determine the pathogenicity of selected strains.

METHODS

Forty-five K. pneumoniae isolates (45/302) were obtained from faeces of companion or wild animals. Virulence factors, gyrA polymerase chain reaction with the restriction fragment length polymorphism (PCR-RFLP) and pulsed field gel electrophoresis (PFGE) were detected and compared with our previous collection of 60 human pathogens. For KLA model and cytotoxicity test, three animal-sourced isolates, CHKP0009 (snake, K1, KpII), CHKP0021 (turtle, K2, pLVPK, KpI, cluster I) and CHKP1027 (dog, non-K1/K2, HV, KpI, cluster III), with similar genotype and/or phenotype to human pathogens were selected and evaluated for their virulence with human hypervirulent K. pneumoniae (hvKp) CG43S.

RESULTS

The prevalence of K. pneumoniae was higher in companion than wild animals. K. pneumoniae was primarily isolated from dogs, turtles and snakes. Some animal-sourced isolates carried virulence factors and revealed phylogenetic relatedness with human pathogens. In KLA model, BALB/c mice infected with snake isolate CHKP0009 and dog isolate CHKP1027 survived for 14 days but showed significant bacterial loads in the liver and spleen. Notably, the pet turtle isolate CHKP0021 presented comparable virulence with human hvKp CG43S and induced liver abscess formation. All three selected animal-sourced isolates could colonize in the GI tract and possess cytotoxic ability. These findings demonstrated pathogenicity of the animal K. pneumoniae isolates. In addition, the high prevalence of K. pneumoniae in companion animals and some isolates with virulence profiles suggested animal-sourced K. pneumoniae has the zoonotic potential to cause human disease.

CONCLUSION

Animals are the natural hosts of zoonotic pathogens. Some animal-sourced K. pneumoniae isolates are not only pathogenic in vivo but also exhibit phylogenetic relatedness to human pathogens, suggesting the existence of a zoonotic risk for K. pneumoniae between these two populations.

Bioinformatics analysis of the in silico engineered protein vaccine with and without Escherichia coli heat labile enterotoxin adjuvant on the model of Klebsiella pneumoniae

Klebsiella pneumoniae (K. pneumoniae) has been identified as a major cause of nosocomial infections with multidrug-resistant phenotypes. Vaccination is one of the most effective methods to prevent infectious diseases. We aim to design a vaccine candidate based on the epitope-rich domains of the OmpA, OMPK17, and fimb proteins of K. pneumoniae that could protect against this infection. A vaccine structure was constructed by selecting five epitope-rich domains from three proteins. We decided to add the heat-labile toxin (LT) of Escherichia coli as an adjuvant to the designed protein structure. The evaluation of the vaccine candidates' interaction with the immune system's receptors showed an appropriate interaction of the specially adjuvated protein with TLR2 and TLR4. The stability of the interactions was also studied by molecular dynamics (MD) for to 100 ns. All parameters showed that the structure of the candidate proteins alone and in complex with TLR2 and TLR4 are stable, especially the adjuvanted protein. Immune response simulations showed that both candidates induce acceptable protective immune responses. Overall, the LT-adjuvanted design protein may have the potential to induce more favorable protective immune responses. However, further in vitro and in vivo studies are required to obtain more definitive results.

Capsule mutations serve as a key strategy of phage resistance evolution of K54 hypervirulent Klebsiella pneumoniae

Phage therapy is a promising antibacterial strategy against the antibiotic resistance crisis. The evolved phage resistance could pose a big challenge to clinical phage therapy. Therefore, it is necessary to conduct a comprehensive analysis of phage resistance mechanisms during treatment. Here, we characterize 37 phage-resistant mutants of hypervirulent K. pneumoniae strain SCNJ1 under phage-imposed selection in both in vitro and in vivo experiments. We show that 97.3% (36/37) of phage-resistant clones possessed at least one mutation in genes related to the CPS biosynthesis. Notably, the wcaJ gene emerges as a mutation hotspot, as mutations in this gene are detected at a high frequency under both conditions. In contrast, mutations in wzc exhibit more association with in vivo samples. These CPS-related mutants all exhibit compromised bacterial fitness and attenuated virulence in mice. Strain CM8 is the only non-CPS-related mutant, which has a bglA mutation that confers phage resistance and retains full fitness and virulence. This study highlights that laboratory characterization of phage resistance evolution can give useful insights for clinical phage therapy.

Phage vB_Kpn_HF0522: Isolation, Characterization, and Therapeutic Potential in Combatting K1 Klebsiella pneumoniae Infections

Purpose

Klebsiella pneumoniae is a globally prevalent pathogen responsible for severe hospital- and community-acquired infections, and presents significant challenges for clinical management. Current therapeutic strategies are no longer able to meet the clinical needs; therefore, there is an urgent need to develop novel therapeutic strategies. This study aimed to evaluate the efficacy of phage therapy in treating bacterial infections.

Methods

Isolated phage vB_Kpn_HF0522 and phage morphology were observed using transmission electron microscopy. Analysis of vB_Kpn_HF0522 characteristics, including optimal multiplicity of infection (MOI), one-step growth curve, host range, stability in different environments, and adsorption capacity. The phage genomic sequence was analyzed to explore evolutionary relationships. The effect of phage vB_Kpn_HF0522 on biofilms was assessed using crystal violet staining assay. The Galleria mellonella (G. mellonella) infection model and mouse infection models were established to evaluate the practical application potential of the phage and the fitness cost of phage-resistant bacteria.

Results

Phage was isolated from hospital sewage for experimental studies. Genome analysis revealed that vB_Kpn_HF0522 is a double-stranded linear DNA virus. Biological characterization demonstrated that this phage specifically targets serotype K1 K. pneumoniae with an optimal multiplicity of infection (MOI) of 0.01, effectively disrupting biofilms and inhibiting bacterial growth. The bacterial growth rate remained largely unchanged after the phage resistance mutation, but mice infected with the mutant strain showed significantly higher survival rates than those infected with the wild-type strain. vB_Kpn_HF0522 increased the survival rate of infected G. mellonella from 12.5% to 75%, inhibited incisional surgical site infections and alleviated inflammatory response in mice.

Conclusion

These findings indicate that vB_Kpn_HF0522 has significant potential for treating specific bacterial infections, and may serve as an antimicrobial agent for research and clinical anti-infective therapy.

The rapid detection of a neonatal unit outbreak of a wild-type Klebsiella variicola using decentralized Oxford Nanopore sequencing

BACKGROUND

Klebsiella variicola has been implicated in neonatal intensive care unit (NICU) outbreaks previously and can be misidentified as Klebsiella pneumoniae. An increased incidence of K. pneumoniae bacteremia on the NICU of our institution was notified to the infection prevention and control (IPC) team in May 2024. The four isolates involved displayed wild-type susceptibility, so had not been detected via multidrug-resistant organism surveillance. This triggered investigation with a nanopore-based decentralized whole-genome sequencing (dWGS) system in operation at our laboratory.

METHODS

Since early 2022, the hospital laboratory at Wellington Regional Hospital has been performing dWGS using the Oxford Nanopore MinION device. This allows for prospective genomic surveillance of certain hospital-associated organisms, but also rapid reactive investigation of possible outbreaks. Isolates are sequenced in the hospital laboratory and undergo multilocus sequence typing (MLST). If transmission events are suspected, sequence data are transferred to the reference laboratory, the Institute for Environmental Science and Research (ESR) for high-resolution bioinformatic analysis.

RESULTS

Within 48 h of notification isolates had been subcultured and sequenced. This showed that three of four isolates were in fact K. variicola, and two of these were sequence type (ST)6385. This sequence type had not been seen previously at our institution, so transmission was suspected. Environmental sampling revealed K. variicola ST6385 in two sink traps on the unit, and prospective sequencing of all K. pneumoniae isolates from NICU samples revealed two further infants with K. variicola ST6385. Subsequent phylogenetic analysis at ESR using original sequence data showed tight clustering of these isolates, confirming an outbreak. Sink traps were disinfected, environmental cleaning procedures were updated, and a strict focus on hand hygiene was reinforced on the ward. No further isolates were detected, and the outbreak was closed after two months.

CONCLUSIONS

Access to dWGS at the level of the local hospital laboratory permitted rapid identification of an outbreak of an organism displaying no unusual antimicrobial resistance features at a point where there were only two known cases. This in turn facilitated a rapid IPC response.

Hypervirulent Klebsiella pneumoniae have better clinical outcomes than classical Klebsiella pneumoniae for lower respiratory tract infection patients

BACKGROUND

The clinical outcomes and microbiological features of lower respiratory tract infections (LRTIs) caused by hypervirulent Klebsiella pneumoniae (hvKp) and classical Klebsiella pneumoniae (cKp) have not been well understood.

METHODS

This study collected 287 non-repetitive Klebsiella pneumoniae isolates from 287 LRTI patients. All these strains underwent annotation for resistance and virulence factors, with 141 strains undergoing mouse infection experiments to assess their virulence. The primary clinical outcomes of these patients were evaluated, including intensive care unit (ICU) admission and in-hospital mortality rates.

RESULTS

A total of 46 capsule serotypes were identified. Among these isolates subjected to mouse infection experiments, the proportions of strains exhibiting hypervirulent phenotypes were 92.6% (25/27), 92.1% (35/38), 80% (4/5), 25% (1/4), 10.5% (2/19), and 7.1% (1/14) for K2, K1, K20, K54, K47, and K25, respectively. Therefore, K1, K2, and K20 K. pneumoniae were defined as hvKp. In addition, the rates of ICU admission and in-hospital mortality for hvKp-infected patients were significantly lower than those of cKp-infected patients (51.4% vs. 65.9%, χ2 = 4.722, p = 0.03 and 8.6% vs. 29%, χ2 = 12.133, p < 0.001). Notably, among the cKp group, the cKp-ST11 subgroup had higher rates of ICU admission (77% vs. 58.5%, χ2 = 7.981, p = 0.005) and in-hospital mortality (44.8% vs. 18.5%, χ2 = 17.585, p < 0.001) than cKp-nonST11 subgroup.

CONCLUSIONS

These findings suggest that capsule serotype is a more accurate factor for the prediction of the virulence phenotype, while hvKp have better clinical outcomes than cKp for LRTI patients. Furthermore, the cKp-ST11 subgroup has the worst prognosis than cKp-nonST11 subgroup.

Molecular Characterization and Risk Factors of Carbapenem-Resistant Hypervirulent Klebsiella pneumoniae Isolated from Chinese Tertiary Hospital

Background

Therefore, the objectives of this study were to investigate the prevalence of carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) in Fujian Medical University Union Hospital, identify their genetic characters, characterize their resistance profiles, and identify risk factors for their infection to improve prevention and treatment strategies for CR-hvKp in the area.

Methods

Between January 2021 and January 2022, clinically identified carbapenem-resistant Klebsiella pneumoniae (CRKp) isolates were collected. A PCR assay was used to detect the K capsule type, virulence genes, carbapenemase genes, and membrane pore protein. ERIC-PCR was carried out for homology analysis. Antimicrobial susceptibility test was used to determine drug resistance. Logistic multivariate regression analysis was conducted to confirm the risk factors for CR-hvKp infection.

Results

In total, 239 CRKp isolates were obtained. The virulence genes with the highest detection rates were mrkD, iucA, and rmpA2. Of these isolates, 54 (22.59%) carried both iucA and rmpA2, thus classifying them as CR-hvKp. All CR-hvKp isolates carried bla KPC. Furthermore, capsular serotypes K64 (94.44%) and K47 (3.70%) were detected. Resistance was observed against most common antibiotics, with the exception of complete sensitivity to ceftazidime-avibactam. ERIC-PCR indicated a potential clonal spread among CR-hvKp. Multivariate analysis found that changing beds was a risk factor for CR-hvKp infection.

Conclusion

Currently, the hospital predominantly carries K64 CR-hvKp that harbors the bla KPC. Our study found that changing patient beds was an independent risk factor for CR-hvKp infection.

Breaking the resistance: integrative approaches with novel therapeutics against Klebsiella pneumoniae

Klebsiella pneumoniae is a leading cause of anti-microbial resistance in healthcare-associated infections that have posed a severe threat to neonatal and wider community. The escalating crises of antibiotic resistance have compelled researchers to explore an innovative arsenal beginning from natural resources to chemical modifications in order to overcome the ever-increasing resistance issues. The present review highlights the drug discovery efforts with a special focus on cutting-edge strategies in the hunt for potential drug candidates against MDR/XDR Klebsiella pneumoniae. Nature's bounty constituting plant extracts, essential oils, fungal extracts, etc. holds promising anti-bacterial potential especially when combined with existing antibiotics. Further, enhancing these natural products with synthetic moieties has improved their effectiveness, creating a bridge between the natural and synthetic world. Conversely, the synthetically modified novel scaffolds have been also designed to meticulously target specific sites. Furthermore, we have also elaborated various emerging strategies for broad-spectrum infections caused by K. pneumoniae, which include anti-microbial peptides, nanotechnology, drug repurposing, bacteriophage, photodynamic, and multidrug therapies. This review further addresses the challenges confronted by the research community and the future way forward in the field of drug discovery against multi-resistant bacterial infections.

A Decade-Long Review of the Virulence, Resistance, and Epidemiological Risks of Klebsiella pneumoniae in ICUs

Klebsiella pneumoniae, a major opportunistic pathogen, causes severe infections in both community and healthcare settings, especially in intensive care units (ICUs), where multidrug-resistant (MDR) strains, such as carbapenem-resistant K. pneumoniae (CRKP), pose significant treatment challenges. The rise in hypervirulent K. pneumoniae (hvKP) with enhanced virulence factors complicates management further. The ST11 clone, prevalent in China, exhibits both resistance and virulence traits, contributing to hospital outbreaks. ICU patients, particularly those with comorbidities or prior antibiotic exposure, are at higher risk. Treatment is complicated by limited antibiotic options and the increasing prevalence of polymicrobial infections, which involve resistant pathogens like Pseudomonas aeruginosa and Acinetobacter baumannii. Combination therapies offer some promise, but mortality rates remain high, and resistance to last-resort antibiotics is growing. Infection control measures and personalized treatment plans are critical, alongside the urgent need for vaccine development to combat the rising threat of K. pneumoniae, particularly in vulnerable populations. Effective management requires improved diagnostic tools, antimicrobial stewardship, and innovative treatment strategies to reduce the burden of this pathogen, especially in resource-limited settings. This review aims to provide a comprehensive analysis of the virulence, resistance, and epidemiological risks of K. pneumoniae in ICUs over the past decade, highlighting the ongoing challenges and the need for continued efforts to combat this growing threat.

Distribution of Virulence-Associated and Aminoglycoside Resistance Genes Among Clinical Isolates of Klebsiella pneumoniae in the Southeast of Iran, During 2019-2023: A Cross-Sectional Study

Background and Aims

Klebsiella pneumoniae (K. pneumoniae), included in the World Health Organization's list of critical priority pathogens, is considered a serious threat to public health. The present study aims to investigate the prevalence of virulence-associated and aminoglycoside resistance genes in clinical isolates of K. pneumoniae.

Methods

This cross-sectional study was carried out on 88 clinical isolates of K. pneumoniae collected from patients at Zabol hospital, Iran. Isolates were identified using conventional microbiology tests and polymerase chain reaction (PCR). Antibiotic susceptibility patterns were ascertained by the disc diffusion method. The prevalence of virulence-associated genes (K1, K2, K5, iucA, and peg-344) and aminoglycoside resistance (AME) genes (aac (2')-Ia, aac (3)-IIa, aac (3)-Ib, aac (6')-1b, ant (2″)-Ia, and aph (3″)-Ib) was investigated by PCR.

Results

The isolates were mostly resistant to kanamycin (73.8%) and streptomycin (69.3%). The most predominant virulence gene was iucA, observed in 89.8% of isolates, followed by peg-344 55.7% and K5 14.8%. The most prevalent resistance gene was aph (3″)-Ib, which was detected in 35.2% of isolates, followed by ant (2″)-Ia 22.7% and aac (3)-Ib 17%. In addition, sixteen different patterns of AME genes were observed.

Conclusion

Most investigated isolates of K. pneumoniae were positive for different virulence-associated and AME genes and therefore can play a significant role in life-threatening infections. Meanwhile, resistance rates to aminoglycoside antibiotics were high and it was primarily due to the presence of AME genes such as aph (3″)-Ib, ant (2″)-Ia, and aac (3)-Ib.

Antibiotic resistance and its correlation with biofilm formation and virulence genes in Klebsiella pneumoniae isolated from wounds

Klebsiella pneumoniae is the most important species of the Klebsiella genus and often causes hospital infections. These bacteria have a high resistance to most of the available drugs, which has caused concern all over the world. In this study, we investigated the antibiotic resistance profile and the ability to produce extended-spectrum beta-lactamase (ESBL) among K. pneumoniae isolates, and then we investigated the relationship between these two factors with biofilm formation and the prevalence of different virulence genes. In this study, 130 isolates of K. pneumoniae isolated from wounds were investigated. The antibiotic resistance of the isolates was evaluated by the disk diffusion method. The microtiter plate method was used to measure biofilm formation. The prevalence of virulence genes was detected by multiplex PCR. Among the examined isolates, 85.3% showed multidrug resistance. 87.6% of the isolates were ESBL-positive. Imipenem, meropenem, and fosfomycin were the most effective drugs. The ability of the isolates to produce biofilm was strong (80%), moderate (12.3%), and weak (7.6%), respectively. fimH, mrKD, entB, and tolC virulence genes were observed in all isolates. High prevalence of antibiotic resistance (especially multidrug resistance), high prevalence of ESBL-producing isolates, the ability of all isolates to biofilm formation, and the presence of fimH, mrKD, entB, and tolC virulence genes in all isolates show the importance of these factors in the pathogenesis of K. pneumoniae isolates in Iraq.

Anti-quorum sensing activity of essential oils against multidrug-resistant Klebsiella pneumoniae: a novel approach to control bacterial virulence

The increasing resistance of microbes to conventional drugs is a serious problem worldwide that has increased the need for alternative antimicrobial compounds. Naturally occurring essential oils (EOs) are considered an important component of traditional pharmacopeia because of their antimicrobial and antioxidant properties. This has attracted researchers to identify novel therapeutic anti-pathogenic agents that could act as non-toxic quorum sensing inhibitors, thus controlling infections without encouraging the development of bacterial resistance. This prompted to undertake the current investigation to unravel the efficacy of EOs as QS modulators in reducing the virulence of multidrug resistant (MDR) strains of Klebsiella pneumoniae. The study highlighted the anti-QS activity of fifteen EOs in modulating the QS-related traits by a reduction in capsular polysaccharide, exopolysaccharide and siderophore production in addition to inhibition of biofilm formation. The overall results suggest using EOs to develop alternate intervention strategies to mitigate infections caused by MDR strains of K. pneumoniae.

Molecular mechanisms responsible KPC-135-mediated resistance to ceftazidime-avibactam in ST11-K47 hypervirulent Klebsiella pneumoniae

Ceftazidime-avibactam resistance attributable to the blaKPC-2 gene mutation is increasingly documented in clinical settings. In this study, we characterized the mechanisms leading to the development of ceftazidime-avibactam resistance in ST11-K47 hypervirulent Klebsiella pneumoniae that harboured the blaKPC-135 gene. This strain possessed fimbriae and biofilm, demonstrating pathogenicity. Compared with the wild-type KPC-2 carbapenemase, the novel KPC-135 enzyme exhibited a deletion of Glu168 and Leu169 and a 15-amino acid tandem repeat between Val262 and Ala276. The blaKPC-135 gene was located within the Tn6296 transposon truncated by IS26 and carried on an IncFII/IncR-type plasmid. Compared to the blaKPC-2-positive cloned strain, only the MIC of ceftazidime increased against blaKPC-135-positive K. pneumoniae and wasn't inhibited by avibactam (MIC 32 μg/mL), while clavulanic acid and vaborbactam demonstrated some inhibition. Kinetic parameters revealed that KPC-135 exhibited a lower Km and kcat/Km with ceftazidime and carbapenems, and a higher (∼26-fold) 50% inhibitory concentration with avibactam compared to KPC-2. The KPC-135 enzyme exerted a detrimental effect on fitness relative to the wild-type strain. Furthermore, this strain possessed hypervirulent determinants, which included the IncHI1B/FIB plasmid with rmpA2 and expression of type 1 and 3 fimbriae. In conclusion, we reported a novel KPC variant, KPC-135, in a clinical ST11-K47 hypervirulent K. pneumoniae strain, which conferred ceftazidime-avibactam resistance, possibly through increased ceftazidime affinity and decreased avibactam susceptibility. This strain simultaneously harboured resistance and virulence genes, posing an elevated challenge in clinical treatment.

Klebsiella pneumoniae capsular polysaccharide: Mechanism in regulation of synthesis, virulence, and pathogenicity

Hypervirulent Klebsiella pneumoniae exhibits strong pathogenicity and can cause severe invasive infections but is historically recognized as antibiotic-susceptible. In recent years, the escalating global prevalence of antibiotic-resistant hypervirulent K. pneumoniae has raised substantial concerns and created an urgent demand for effective treatment options. Capsular polysaccharide (CPS) is one of the main virulence determinants contributing to the hypervirulent phenotype. The structure of CPS varies widely among strains, and both the structure and composition of CPS can influence the virulence of K. pneumoniae. CPS possesses various immune evasion mechanisms that promote the survival of K. pneumoniae, as well as its colonization and dissemination. Given the proven viability of therapies that target the capsule, improving our understanding of the CPS structure is critical to effectively directing treatment strategies. In this review, the structure and typing of CPS are addressed as well as genes related to synthesis and regulation, relationships with virulence, and pathogenic mechanisms. We aim to provide a reference for research on the pathogenesis of K. pneumoniae.

Genomic characterisation of an extended-spectrum β-Lactamase-producing Klebsiella pneumoniae isolate assigned to a novel sequence type (6914)

BACKGROUND

Cow milk, which is sometimes consumed raw, hosts a plethora of microorganisms, some of which are beneficial, while others raise food safety concerns. In this study, the draft genome of an extended-spectrum β-lactamase-producing Klebsiella pneumoniae subsp. pneumoniae strain Cow102, isolated from raw cow milk used to produce traditional foods in Nigeria, is reported.

RESULT

The genome has a total length of 5,359,907 bp, with 70 contigs and a GC content of 57.35%. A total of 5,244 protein coding sequences were detected with 31% mapped to a subsystem, and genes coding for amino acids and derivatives being the most prevalent. Multilocus sequence typing revealed that the strain had new allelic profile assigned to the novel 6914 sequence type possessing capsular and lipopolysaccharide antigen K locus 122 with an unknown K type (KL122) and O locus O1/O2v2 with type O2afg, respectively. A total of 28 resistance-related genes, 98 virulence-related genes, two plasmids and five phages were identified in the genome. The resistance genes oqxA, oqxB and an IS3 belonging to cluster 204 were traced to bacteriophage Escher 500,465. Comparative analysis predicted one strain specific orthologous group comprising three genes.

CONCLUSION

This report of a novel sequence type (ST6914) in K. pneumoniae presents a new allelic profile, indicating ongoing evolution and diversification within the species. Its uniqueness suggests it may represent a locally evolved lineage, although further sampling would be necessary to confirm this hypothesis. The strain's multidrug resistance, virulence gene repertoire, and isolation from animal milk render it a potentially significant public health concern, underscoring the importance of genomic surveillance in non-clinical settings to detect emerging strains. Further research is required to fully characterise the capsular K type of ST6914.

Metabolic Reprogramming of Klebsiella pneumoniae Exposed to Serum and Its Potential Implications in Host Immune System Evasion and Resistance

The aim of this study was to identify, using proteomics, the molecular alterations caused by human serum exposure to Klebsiella pneumoniae ACH2. The analysis was performed under two different conditions, native serum from healthy donors and heat-inactivated serum (to inactivate the complement system), and at two different times, after 1 and 4 h of serum exposure. More than 1,000 bacterial proteins were identified at each time point. Enterobactin, a siderophore involved in iron uptake, and proteins involved in translation were upregulated at 1 h, while the chaperone ProQ and the glyoxylate cycle were identified after 4 h. Enzymes involved in the stress response were downregulated, and the SOD activity was validated using an enzymatic assay. In addition, an intricate metabolic adaptation was observed, with pyruvate and thiamine possibly involved in survival and virulence in the first hour of serum exposure. The addition of exogenous thiamine contributes to bacterial growth in human serum, corroborating this result. During 4 h of serum exposure, the glyoxylate cycle (GC) probably plays a central role, and the addition of exogenous succinate suppresses the GC, inducing a decrease in serum resistance. Therefore, serum exposure causes important changes in iron acquisition, the expression of virulence factors, and metabolic reprogramming, which could contribute to bacterial serum resistance.

Ceftazidime-avibactam resistance in KPC-producing Klebsiella pneumoniae accompanied hypermucoviscosity acquisition

BACKGROUND

Antimicrobial resistance and bacterial hypermucoviscosity, associated with escalating production of capsules, constitute major challenges for the clinical management of Klebsiella pneumoniae (K. pneumoniae) infections. This study investigates the association and underlying mechanism between ceftazidime-avibactam (CAZ-AVI) resistance and bacterial hypermucoviscosity in Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-Kp).

RESULTS

The proportion of CAZ-AVI-sensitive clinical isolates exhibiting the hypermucoviscous phenotype was significantly lower than that of the resistant strains (5.6% vs. 46.7%, P < 0.001). To further verify the correlation and molecular mechanism between CAZ-AVI resistance and hypermucoviscosity, 10 CAZ-AVI-resistant isolates were generated through in vitro resistance selection from CAZ-AVI-sensitive KPC-Kp. The results showed the same association as it showed in the clinical isolates, with four out of ten induced CAZ-AVI-resistant isolates transitioning from negative to positive in the string tests. Comparative genomic analysis identified diverse mutations in the wzc gene, crucial for capsule polysaccharide (CPS) synthesis, in all four CAZ-AVI-resistant hypermucoviscous KPC-Kp strains compared to the parent strains. However, these mutations were absent in the other six KPC-Kp strains that did not exhibit induced hypermucoviscosity. Cloning of the wzc gene variants and their expression in wild-type strains confirmed that mutations in the wzc gene can induce bacterial hypermucoviscosity and heightened virulence, however, they do not confer resistance to CAZ-AVI.

CONCLUSIONS

These results indicated that resistance to CAZ-AVI in KPC-Kp isolates may be accompanied by the acquisition of hypermucoviscosity, with mutations in the wzc gene often involving in this process.

Far-UVC light (222 nm) efficiently inactivates clinically significant antibiotic-resistant bacteria on diverse material surfaces

In recent years, there has been a gradual increase in the prevalence of drug-resistant bacteria, primarily attributed to the widespread use of antibiotics. This has resulted in heightened mortality rates, morbidity, and exorbitant healthcare costs associated with antibiotic-resistant bacterial infections. In order to mitigate the spread of antibiotic-resistant bacteria, environmental disinfection plays a crucial role. Ultraviolet radiation C (UVC) light disinfection has emerged as a potent technique to limit the transmission of nosocomial pathogens and prevent healthcare-associated infections. Different types of high-touch surfaces were used. A serial disinfected experiment with different 222 nm UVC dosages was conducted on clinically isolated antibiotic-resistant bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus species (VRE), carbapenem-resistant Escherichia coli (CREC), carbapenem-resistant Klebsiella pneumonia (CRKP), carbapenem-resistant Acinetobacter baumannii (CRAB), and carbapenem-resistant Pseudomonas aeruginosa (CRPA) on different material surfaces. The bactericidal efficacy was evaluated by The Clinical & Laboratory Standards Institute (CLSI) guidelines. 222 nm UVC irradiation had a potent bactericidal efficacy on clinical antibiotic-resistant bacteria on different high-touch surfaces that are commonly found in the environment and healthcare facilities. 222 nm UVC irradiation time was tested from 10 s to 1 h. Different surfaces affect the efficiency of 222 nm UVC. The more adsorptive a material is, the higher the dosage of 222 nm UVC irradiation energy is required for effective disinfection. The use of 222 nm UVC lamps for disinfection on different materials has been shown to be a useful method. However, it is crucial to pay attention to the energy required for effective sterilization.

IMPORTANCE

This study is crucial, providing compelling evidence on Far-ultraviolet radiation C (Far-UVC) light's efficacy against clinically significant antibiotic-resistant bacteria-a pressing issue in microbiology and infection control. Our research employs antibiotic-resistant strains from clinically isolated bacteria, emphasizing real-world relevance. Simultaneously, we assess Far-UVC light (222 nm) across diverse material surfaces commonly found in clinical settings. This dual approach ensures practical applicability and broad relevance. Our comprehensive setup and rigorous methodologies unequivocally demonstrate Far-UVC light's potency in combating antibiotic-resistant bacteria. Since 222 nm far-UVC has a disinfection capability and is harmless to mammalian cells, this dual effectiveness positions Far-UVC as a secure tool for infection control, with potential applications in healthcare settings, mitigating antibiotic-resistant bacteria spread, and reducing healthcare-associated infections.

Genetic characteristics of clinical carbapenem-resistant Klebsiella pneumoniae: epidemic ST11 KPC-2-producing strains and non-negligible NDM-5-producing strains with diverse STs

Klebsiella pneumoniae is among the most important Gram-negative pathogens that can cause serious nosocomial infections. The emergence and prevalence of hypervirulent carbapenem-resistant K. pneumoniae (Hv-CRKP) pose a significant challenge to public health. In this study, we characterized thirty carbapenem-resistant K. pneumoniae (CRKP) strains from a tertiary care hospital in Sichuan province, China, by whole-genome sequencing and genome analysis. These strains were all highly resistant to carbapenem but remained susceptible to tigecycline. Of the 30 tested CRKP strains, 23 were positive for blaKPC-2 and seven for blaNDM-5. These blaKPC-2-positive strains all belonged to ST11, while blaNDM-5-positive strains belonged to five distinct STs. Phylogenetic analysis revealed a predominant intra-hospital transmission of ST11-KL64 in KPC-2-producing CRKP, and that both clonal and horizontal transmission of blaNDM-5 have occurred among NDM-5-producing CRKP strains in this hospital. Hypervirulence genes were commonly detected in the CRKP. The prevalent pLVKP-like plasmid and ICEKp seem to have contributed largely to the transmission of virulence genes in them. blaNDM-5 was located on highly similar IncX3 plasmids in the collected strains, and its truncated vision was highlighted. blaKPC-2 was primarily carried by IncFII/IncR plasmids in our collection. At least two IncFII/IncR plasmid subtypes were identified, exhibiting high similarity to many previously reported blaKPC-2-bearing plasmids from different parts of China. The findings provide an expanded knowledge of the genetic characteristics of CRKP, the transmission pattern of carbapenem-resistance genes, and also the convergence of Hv-CRKP.

The Association between Resistance and Virulence of Klebsiella pneumoniae in High-Risk Clonal Lineages ST86 and ST101

Klebsiella pneumoniae is an opportunistic pathogen known for two main pathotypes: classical K. pneumoniae (cKp), often multidrug-resistant and common in hospitals, and hypervirulent K. pneumoniae (hvKp), associated with severe community-acquired infections. The recent emergence of strains combining hypervirulence and resistance is alarming. This study investigates the distribution of sequence types (STs), resistance, and virulence factors in K. pneumoniae strains causing bloodstream and urinary tract infections in Croatia. In 2022, 200 consecutive K. pneumoniae isolates were collected from blood and urine samples across several Croatian hospitals. Whole genome sequencing was performed on 194 isolates. Within the analyzed K. pneumoniae population, the distribution of sequence types was determined with multi-locus sequence typing (MLST) and capsule loci, resistance, and virulence determinants were assessed with the bioinformatics tool Kleborate. The analysis identified 77 different STs, with ST101 (24.6%) being the most prevalent, predominantly linked to the K17 capsular type (CT), invasive device usage, high antimicrobial resistance, and low virulence scores. The highest virulence scores were recorded in ST86 isolates, which were predominantly linked to the K2 CT and included some strains with medium resistance scores. String tests were positive in 19 strains, but only four of those harbored hypermucoviscous genetic determinants. The most prevalent ST101 clone in Croatia demonstrated a diverging association between resistance and virulence. An alarming co-existence of resistance and virulence was recorded in the ST86 strains.

RfaH contributes to maximal colonization and full virulence of hypervirulent Klebsiella pneumoniae

Hypervirulent K. pneumoniae (hvKp) have emerged as clinically important pathogens, posing a serious threat to human health. RfaH, a transcriptional elongation factor, has been regarded as implicated in facilitating the transcription of long virulence operons in certain bacterial species. In K. pneumoniae, RfaH plays a vital role in promoting CPS synthesis and hypermucoviscosity, as well as mediating bacterial fitness during lung infection. In this study, we aim to conduct a systematic investigation of the roles of rfaH in the survival, dissemination, and colonization of hvKp through in vitro and in vivo assays. We found that bacterial cells and colonies displayed capsule -deficient phenotypes subsequent to the deletion of rfaH in K. pneumoniae NTUH-K2044. We confirmed that rfaH is required for the synthesis of capsule and lipopolysaccharide (LPS) by positively regulating the expression of CPS and LPS gene clusters. We found that the ΔrfaH mutant led to a significantly decreased mortality of K. pneumoniae in a mouse intraperitoneal infection model. We further demonstrated that the absence of rfaH was associated with slower bacterial growth under conditions of low nutrition or iron limitation. ΔrfaH displayed reduced survival rates in the presence of human serum. Besides, the engulfment of the ΔrfaH mutant was significantly higher than that of NTUH-K2044 by macrophages in vivo, indicating an indispensable role of RfaH in the phagocytosis resistance of hvKp in mice. Both mouse intranasal and intraperitoneal infection models revealed a higher bacterial clearance rate of ΔrfaH in lungs, livers, and spleens of mice compared to its wild type, suggesting an important role of RfaH in the bacterial survival, dissemination, and colonization of hvKp in vivo. Histopathological results supported that RfaH contributes to the pathogenicity of hvKp in mice. In conclusion, our study demonstrates crucial roles of RfaH in the survival, colonization and full virulence of hvKp, which provides several implications for the development of RfaH as an antibacterial target.

Evaluation of Klebsiella pneumoniae pathogenicity through holistic gene content analysis

Klebsiella pneumoniae is a Gram-negative bacterium that causes both community- and healthcare-associated infections. Although various virulence factors and highly pathogenic phenotypes have been reported, the pathogenicity of K. pneumoniae is still not fully understood. In this study, we utilized whole-genome sequencing data of 168 clinical K. pneumoniae strains to assess pathogenicity. This work was based on the concept that the genetic composition of individual genomes (referred to as holistic gene content) of the strains may contribute to their pathogenicity. Holistic gene content analysis revealed two distinct groups of K. pneumoniae strains ('major group' and 'minor group'). The minor group included strains with known highly pathogenic clones (ST23, ST375, ST65 and ST86). The minor group had higher rates of capsular genotype K1 and presence of nine specific virulence genes (rmpA, iucA, iutA, irp2, fyuA, ybtS, iroN, allS and clbA) compared to the major group. Pathogenicity was assessed using Galleria mellonella larvae. Infection experiments revealed lower survival rates of larvae infected with strains from the minor group, indicating higher virulence. In addition, the minor group had a higher string test positivity rate than the major group. Holistic gene content analysis predicted possession of virulence genes, string test positivity and pathogenicity as observed in the G. mellonella infection model. Moreover, the findings suggested the presence of as yet unrecognized genomic elements that are either involved in the acquisition of virulence genes or associated with pathogenicity.

Essential oils as capsule disruptors: enhancing antibiotic efficacy against multidrug-resistant Klebsiella pneumoniae

Background

Multidrug-resistant Klebsiella pneumoniae (MDR-KP) poses a significant global health threat due to its involvement in severe infections and high mortality rates. The emergence of MDR strains necessitates the exploration of alternative therapeutic strategies.

Methods

K. pneumoniae isolates were obtained from human and animal sources. Antibacterial susceptibility testing was performed, followed by the evaluation of essential oil activity through inhibition zone, MIC, and MBC determinations. Checkerboard assays were conducted to assess synergistic effects with amikacin. Gene expression analysis and transmission electron microscopy were employed to elucidate the mechanisms of action. Molecular docking studies were performed to identify potential binding targets of bioactive compounds.

Results

Klebsiella pneumoniae was isolated from 25 of the100 samples examined, representing a prevalence rate of 25%. All isolates were found to be multidrug-resistant. Tea tree and thyme essential oils exhibited potent antibacterial activity and synergistic effects with amikacin. Notably, these combinations significantly downregulated the expression of key capsule virulence genes (wcaG, rmpA, magA, uge, and wabG), suggesting a novel mechanism for enhancing amikacin efficacy. Transmission electron microscopy revealed disrupted cell integrity in MDR-KP cells treated with the combinations. Molecular docking analysis identified Terpinen-4-ol, Farnesol, 1,4-Dihydroxy-p-menth-2-ene, and 7-Oxabicyclo [4.1.0] heptane as potential bioactive compounds responsible for the observed effects.

Conclusion

By effectively combating MDR-KP, this research holds promise for reducing antibiotic resistance, improving treatment outcomes, and ultimately enhancing potential care.

RIL-seq reveals extensive involvement of small RNAs in virulence and capsule regulation in hypervirulent Klebsiella pneumoniae

Hypervirulent Klebsiella pneumoniae (hvKp) can infect healthy individuals, in contrast to classical strains that commonly cause nosocomial infections. The recent convergence of hypervirulence with carbapenem-resistance in K. pneumoniae can potentially create 'superbugs' that are challenging to treat. Understanding virulence regulation of hvKp is thus critical. Accumulating evidence suggest that posttranscriptional regulation by small RNAs (sRNAs) plays a role in bacterial virulence, but it has hardly been studied in K. pneumoniae. We applied RIL-seq to a prototypical clinical isolate of hvKp to unravel the Hfq-dependent RNA-RNA interaction (RRI) network. The RRI network is dominated by sRNAs, including predicted novel sRNAs, three of which we validated experimentally. We constructed a stringent subnetwork composed of RRIs that involve at least one hvKp virulence-associated gene and identified the capsule gene loci as a hub target where multiple sRNAs interact. We found that the sRNA OmrB suppressed both capsule production and hypermucoviscosity when overexpressed. Furthermore, OmrB base-pairs within kvrA coding region and partially suppresses translation of the capsule regulator KvrA. This agrees with current understanding of capsule as a major virulence and fitness factor. It emphasizes the intricate regulatory control of bacterial phenotypes by sRNAs, particularly of genes critical to bacterial physiology and virulence.

Relationship between virulence and carbapenem resistance phenotype of Klebsiella pneumoniae from blood infection: identification of a carbapenem-resistant and hypervirulent strain

OBJECTIVES

To investigate the relationship between the virulence and the carbapenem resistance phenotype of Klebsiella pneumoniae from blood infection, and to identify carbapenem-resistant and hypervirulent Klebsiella pneumoniae (CR-HVKP)strains.

METHODS

A total of 192 Klebsiella pneumoniae strains were isolated from blood culture of patients with bloodstream infections from 2016 to 2019, of which 96 isolates were carbapenem-resistant Klebsiella pneumoniae (CRKP) and 96 were carbapenem-sensitive Klebsiella pneumoniae (CSKP). The drug susceptibility was detected by VITEK-2 automatic microbial analyzer; carbapenemase genes, virulence genes and capsule typing were detected by polymerase chain reaction; the high viscosity phenotype of strains was detected by string test, and the genome characteristics of CR-HVKP were detected by whole genome sequencing. Serum killing and biofilm formation test were used to further verify the virulence of CR-HVKP.

RESULTS

There were significant differences in drug resistance to common antibiotics, except for minocycline between CSKP and CRKP isolates (all P<0.05). 92 out of 96 CRKP isolates carried carbapenemase genes, mainly blaKPC-2. The string tests were positive in 4 isolates of CRKP and 36 isolates of CSKP (P<0.05). The detection rates of virulence genes Kfu, aerobictin, iutA, ybtS, rmpA, magA, allS, and capsule antigen K1 and K2 in CSKP group were significantly higher than those in CRKP group (all P<0.05). One HVKP strain was detected in the CRKP group (CR-HVKP) and 36 HVKP was detected in the CSKP group (P<0.05). The CR-HVKP strain belonged to the MLST412, serotype K57, expressed iutA, entB, mrkD, fimH, and rmpA virulence genes, and showed strong biofilm formation and significantly increased serum resistance. Whole genome sequencing results showed that this CR-HVKP isolate carried blaSHV-145, blaTEM-1, blaCTX-M-3, fosA6, oqxA5, oqxB26, and aac(3)-IId resistance genes, accompanied by abnormalities in outer membrane protein K (OmpK) 35 and OmpK36.

CONCLUSIONS

The drug resistance of CRKP is significantly higher than that of CSKP, while CRKP carrying fewer virulence genes in both number and types compared to CSKP. A new MLST type of carbapenem-resistant and hypervirulent Klebsiella pneumoniae strain has been detected, which requires clinical awareness and epidemiological monitoring.

Microaerobic-mediated suppression of Klebsiella pneumoniae mucoviscosity is restored by rmpD overexpression

AIMS

Hypervirulent Klebsiella pneumoniae (hvKp) causes invasive community-acquired infections in healthy individuals, and hypermucoviscosity (HMV) is the main phenotype associated with hvKp. This study investigates the impact of microaerobic environment availability on the mucoviscosity of K. pneumoniae.

METHODS AND RESULTS

By culturing 25 clinical strains under microaerobic and aerobic environments, we observed a notable reduction in mucoviscosity in microaerobic environments. RNA sequencing and qRT-PCR revealed downregulated expressions of capsule synthesis genes (galf, orf2, wzi, wza, wzb, wzc, wcaj, manC, manB, and ugd) and regulatory genes (rmpA, rmpD, and rmpC) under microaerobic conditions. Transmission electron microscopy and Indian ink staining analysis were performed, revealing that the capsular thickness of K. pneumoniae decreased by half in microaerobic conditions compared to aerobic conditions. Deletion of rmpD and rmpC caused the loss of the HMV phenotype in both aerobic and microaerobic conditions. However, compared to wild-type strain in microaerobic condition, only rmpD overexpression strain, and not rmpC overexpression strain, displayed a significant increase in capsule thickness in microaerobic conditions.

CONCLUSIONS

Microaerobic conditions can suppress the mucoviscosity of K. pneumoniae, but this suppression can be overcome by altering the expression of rmpD, indicating a specific function for rmpD in the oxygen environmental adaptation of K. pneumoniae.

Insights into the recognition of hypermucoviscous Klebsiella pneumoniae clinical isolates by innate immune lectins of the Siglec and galectin families

Klebsiella pneumoniae is an opportunistic bacterium that frequently colonizes the nasopharynx and gastrointestinal tract and can also cause severe infections when invading other tissues, particularly in immunocompromised individuals. Moreover, K. pneumoniae variants exhibiting a hypermucoviscous (HMV) phenotype are usually associated with hypervirulent strains that can produce invasive infections even in immunocompetent individuals. Major carbohydrate structures displayed on the K. pneumoniae surface are the polysaccharide capsule and the lipopolysaccharide, which presents an O-polysaccharide chain in its outermost part. Various capsular and O-chain structures have been described. Of note, production of a thick capsule is frequently observed in HMV variants. Here we examined the surface sugar epitopes of a collection of HMV and non-HMV K. pneumoniae clinical isolates and their recognition by several Siglecs and galectins, two lectin families of the innate immune system, using bacteria microarrays as main tool. No significant differences among isolates in sialic acid content or recognition by Siglecs were observed. In contrast, analysis of the binding of model lectins with diverse carbohydrate-binding specificities revealed striking differences in the recognition by galactose- and mannose-specific lectins, which correlated with the binding or lack of binding of galectins and pointed to the O-chain as the plausible ligand. Fluorescence microscopy and microarray analyses of galectin-9 binding to entire cells and outer membranes of two representative HMV isolates supported the bacteria microarray results. In addition, Western blot analysis of the binding of galectin-9 to outer membranes unveiled protein bands recognized by this galectin, and fingerprint analysis of these bands identified several proteins containing potential O-glycosylation sites, thus broadening the spectrum of possible galectin ligands on the K. pneumoniae surface. Moreover, Siglecs and galectins apparently target different structures on K. pneumoniae surfaces, thereby behaving as non-redundant complementary tools of the innate immune system.

Bacteraemia associated with multiple septic localizations caused by Klebsiella pneumoniae sequence type ST660

We report a case of Klebsiella pneumoniae bacteraemia in an 80-year-old man in France with no history of travel to Asia, complicated by endogenous endophthalmitis, multiple cerebral microbleeds and hepatic microabscesses, associated with a Bentall endocarditis. Hypervirulence pathotype was suggested based on clinical picture, bacterial isolate genomic sequence and hypermucoidy. Interestingly, the isolate had the non-K1/K2-capsular serotype locus KL113-like, carried a KpVP-1-like virulence plasmid, and belonged to the emerging sublineage SL660 (comprising the sequence type ST660).

A new model of endotracheal tube biofilm identifies combinations of matrix-degrading enzymes and antimicrobials able to eradicate biofilms of pathogens that cause ventilator-associated pneumonia

Ventilator-associated pneumonia is defined as pneumonia that develops in a patient who has been on mechanical ventilation for more than 48 hours through an endotracheal tube. It is caused by biofilm formation on the indwelling tube, which introduces pathogenic microbes such as Pseudomonas aeruginosa, Klebsiella pneumoniae and Candida albicans into the patient's lower airways. Currently, there is a lack of accurate in vitro models of ventilator-associated pneumonia development. This greatly limits our understanding of how the in-host environment alters pathogen physiology and the efficacy of ventilator-associated pneumonia prevention or treatment strategies. Here, we showcase a reproducible model that simulates the biofilm formation of these pathogens in a host-mimicking environment and demonstrate that the biofilm matrix produced differs from that observed in standard laboratory growth medium. In our model, pathogens are grown on endotracheal tube segments in the presence of a novel synthetic ventilated airway mucus medium that simulates the in-host environment. Matrix-degrading enzymes and cryo-scanning electron microscopy were employed to characterize the system in terms of biofilm matrix composition and structure, as compared to standard laboratory growth medium. As seen in patients, the biofilms of ventilator-associated pneumonia pathogens in our model either required very high concentrations of antimicrobials for eradication or could not be eradicated. However, combining matrix-degrading enzymes with antimicrobials greatly improved the biofilm eradication of all pathogens. Our in vitro endotracheal tube model informs on fundamental microbiology in the ventilator-associated pneumonia context and has broad applicability as a screening platform for antibiofilm measures including the use of matrix-degrading enzymes as antimicrobial adjuvants.

Biological characteristics of manganese transporter MntP in Klebsiella pneumoniae

Klebsiella pneumoniae is an important opportunistic pathogen that causes a variety of infections. It is critical for bacteria to maintain metal homeostasis during infection. By using an isogenic mntP deletion mutant of K. pneumoniae strain NTUH-K2044, we found that MntP was a manganese efflux pump. Manganese increased the tolerance to oxidative stress, and oxidative stress could increase the intracellular manganese concentration. In oxidative stress, the mntP deletion mutant exhibited significantly higher sensitivity to manganese. Furthermore, iron could increase the tolerance of the mntP deletion mutant to manganese. Inductively coupled plasma mass spectrometry analysis revealed that the mntP deletion mutant had higher intracellular manganese and iron concentrations than wild-type and complementary strains. These findings suggested that iron could increase manganese tolerance in K. pneumoniae. This work elucidated the role of MntP in manganese detoxification and Mn/Fe homeostasis in K. pneumoniae.IMPORTANCEMetal homeostasis plays an important role during the process of bacterial infection. Herein, we revealed that MntP was involved in intracellular manganese homeostasis. Manganese promoted resistance to oxidative stress in Klebsiella pneumoniae. Furthermore, we demonstrated that the mntP deletion mutant exhibited significantly lower survival under manganese and H2O2 conditions. Oxidative stress increased the intracellular manganese content of the mntP deletion mutant. MntP played a critical role in maintaining intracellular manganese and iron concentrations. MntP contributed to manganese detoxification and Mn/Fe homeostasis in K. pneumoniae.

A New Casjensviridae Bacteriophage Isolated from Hospital Sewage for Inactivation of Biofilms of Carbapenem Resistant Klebsiella pneumoniae Clinical Isolates

Klebsiella pneumoniae, a member of the ESKAPE pathogen group, is a prominent cause of hospital-acquired infections. The WHO has recognized carbapenem-resistant K. pneumoniae as a critical-one priority pathogen. These resilient superbugs have the ability to form biofilms and present a significant global threat. In the present study, we isolated and characterized a bacteriophage SAKp02, from hospital sewage, infectious to carbapenem-resistant K. pneumoniae patient isolates. SAKp02 could infect 43 of 72 clinical isolates, indicating a broad host spectrum. Whole genome analysis classified SAKp02 within the family Casjensviridae, with a 59,343 bp genome encoding 82 ORFs. Comparative genomic analysis revealed significant differences between SAKp02 and its closest viruses, indicating a distinct genetic makeup positioning it as a novel phage strain within the lineage. The SAKp02 genome comprises bacteriolytic enzymes, including holin, endolysin, and phage depolymerase, crucial for bacterial lysis and biofilm disruption. It reduced biofilm biomass by over threefold compared to the control and eradicated 99% of viable cells within a 4 h treatment period. Scanning electron microscopy corroborated the ability of the phage to dismantle biofilm matrices and lyse bacterial cells. Safe and effective treatments are warranted, and hence, the fully characterized lytic phages with therapeutic potential against drug-resistant clinical isolates of bacteria are needed. Our study is the first to report the antibacterial and antibiofilm activity of Casjensviridae phages, and our discovery of a novel K. pneumoniae phage broadens the arsenal against the bacteria.

Complete genome sequence, phenotypic correlation and pangenome analysis of uropathogenic Klebsiella spp

Urinary tract infections (UTI) by antibiotic resistant and virulent K. pneumoniae are a growing concern. Understanding the genome and validating the genomic profile along with pangenome analysis will facilitate surveillance of high-risk clones of K. pneumoniae to underpin management strategies toward early detection. The present study aims to correlate resistome with phenotypic antimicrobial resistance and virulome with pathogenicity in Klebsiella spp. The present study aimed to perform complete genome sequences of Klebsiella spp. and to analyse the correlation of resistome with phenotypic antimicrobial resistance and virulome with pathogenicity. To understand the resistome, pangenome and virulome in the Klebsiella spp, the ResFinder, CARD, IS Finder, PlasmidFinder, PHASTER, Roary, VFDB were used. The phenotypic susceptibility profiling identified the uropathogenic kp3 to exhibit multi drug resistance. The resistome and in vitro antimicrobial profiling showed concordance with all the tested antibiotics against the study strains. Hypermucoviscosity was not observed for any of the test isolates; this phenotypic character matches perfectly with the absence of rmpA and magA genes. To the best of our knowledge, this is the first report on the presence of ste, stf, stc and sti major fimbrial operons of Salmonella enterica serotype Typhimurium in K. pneumoniae genome. The study identifies the discordance of virulome and virulence in Klebsiella spp. The complete genome analysis and phenotypic correlation identify uropathogenic K. pneumoniae kp3 as a carbapenem-resistant and virulent pathogen. The Pangenome of K. pneumoniae was open suggesting high genetic diversity. Diverse K serotypes were observed. Sequence typing reveals the prevalence of K. pneumoniae high-risk clones in UTI catheterised patients. The study also highlights the concordance of resistome and in vitro susceptibility tests. Importantly, the study identifies the necessity of virulome and phenotypic virulence markers for timely diagnosis and immediate treatment for the management of high-risk K. pneumoniae clones.

Occurrence of carbapenem-resistant hypervirulent Klebsiella pneumoniae in oysters in Egypt: a significant public health issue

BACKGROUND

The global dissemination of critical-priority carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) via food sources represents a significant public health concern. Epidemiological data on CR-hvKp in oysters in Egypt is limited. This study aimed to investigate the potential role of oysters sold in Egypt as a source for carbapenem-resistant K. pneumoniae (CRKP), hypervirulent K. pneumoniae (hvKp), and CR-hvKp and assess associated zoonotic risks.

METHODS

A sample of 330 fresh oysters was randomly purchased from various retail fish markets in Egypt and divided into 33 pools. Bacteriological examination and the identification of Klebsiella pneumoniae were performed. Carbapenem resistance in K. pneumoniae isolates was determined by phenotypic and molecular methods. Additionally, the presence of hypervirulent K. pneumoniae was identified based on virulence gene markers (peg-344, rmpA, rmpA2, iucA, and iroB), followed by a string test. The clustering of CR-hvKp strains was carried out using R with the pheatmap package.

RESULTS

The overall prevalence of K. pneumoniae was 48.5% (16 out of 33), with 13 isolates displaying carbapenem resistance, one intermediate resistance, and two sensitive. Both carbapenem-resistant K. pneumoniae and carbapenem-intermediate-resistant K. pneumoniae strains exhibited carbapenemase production, predominantly linked to the blaVIM gene (68.8%). HvKp strains were identified at a rate of 62.5% (10/16); notably, peg-344 was the most prevalent gene. Significantly, 10 of the 13 CRKP isolates possessed hypervirulence genes, contributing to the emergence of CR-hvKp. Moreover, cluster analysis revealed the clustering of two CR-hvKp isolates from the same retail fish market.

CONCLUSION

This study provides the first insight into the emergence of CR-hvKp among oysters in Egypt. It underscores the potential role of oysters as a source for disseminating CR-hvKp within aquatic ecosystems, presenting a possible threat to public health.

Screening of Klebsiella pneumoniae subsp. pneumoniae Strains with Multi-Drug Resistance and Virulence Profiles Isolated from an Italian Hospital between 2020 and 2023

Klebsiella pneumoniae strains that are resistant to multiple drugs (KPMDRs), which are often acquired in hospital settings and lead to healthcare-associated infections, pose a serious public health threat, as does hypervirulent K. pneumoniae (hvKp), which can also cause serious infections in otherwise healthy individuals. The widespread and often unnecessary use of antibiotics seen during the recent COVID-19 pandemic has exacerbated the challenges posed by antibiotic resistance in clinical settings. There is growing concern that hypervirulent (hvKp) strains may acquire genes that confer antimicrobial resistance, thus combining an MDR profile with their increased ability to spread to multiple body sites, causing difficult-to-treat infections. This study aimed to compare resistance and virulence profiles in KPC-3-producing K. pneumoniae isolates collected over four years (2020-2023). A genome-based surveillance of all MDR CRE-K. pneumoniae was used to identify genetic differences and to characterize the virulence and resistance profiles. Our results provide a picture of the evolution of resistance and virulence genes and contribute to avoiding the possible spread of isolates with characteristics of multi-drug resistance and increased virulence, which are thought to be one of the main global challenges to public health, within our hospital.

Complete genome sequence of carbapenem-resistant pathogenic Klebsiella aerogenes strain CH7 isolated from vermicompost

We announce the complete genome of Klebsiella aerogenes strain CH7, isolated from a vermicompost sample. A total of 9.14131 million high-quality reads comprised 96 contigs with 5,273 genes and 5,038 protein-coding genes.

Identification of Lytic Phages Against Multidrug-Resistant Klebsiella pneumoniae: Illuminating Hope on Antimicrobial-Resistance

Background

Lytic phages have been considered as a solution to mitigate the emergence of multidrug-resistant bacteria. Nevertheless, finding phages capable of targeting a broad host-range remains a significant challenge.

Materials and Methods

Our study introduces two lytic phages isolated from hospital effluent, which are active against extended-spectrum cephalosporin-resistant Klebsiella pneumoniae.

Results

Overnight coculture with host, two purified phage lysates yielded around 3.0 × 107 PFU/mL with an average 0.8 ± 0.2 mm diameter of clear, round, and non-halo plaques in both instances. The genomes of iPHaGe-KPN-11i (177,603 bp, 273 coding sequences [CDS]) and iPHaGe-KPN-12i (178,179 bp, 275 CDS) belong to the Pseudotevenvirus genus. Both phages have at least 120 genes with known functions, including 1 endolysin and 2 tRNAs, and are capable of lysing at least 12 distinct bacterial species in vitro.

Conclusions

Most phages are host-specific, whereas our phages can kill multiple bacterial species, enabling their potential use for a broad range of hosts.

Exploring the resistome, virulome, and mobilome of multidrug-resistant Klebsiella pneumoniae isolates: deciphering the molecular basis of carbapenem resistance

BACKGROUND

Klebsiella pneumoniae, a notorious pathogen for causing nosocomial infections has become a major cause of neonatal septicemia, leading to high morbidity and mortality worldwide. This opportunistic bacterium has become highly resistant to antibiotics due to the widespread acquisition of genes encoding a variety of enzymes such as extended-spectrum beta-lactamases (ESBLs) and carbapenemases. We collected Klebsiella pneumoniae isolates from a local tertiary care hospital from February 2019-February 2021. To gain molecular insight into the resistome, virulome, and genetic environment of significant genes of multidrug-resistant K. pneumoniae isolates, we performed the short-read whole-genome sequencing of 10 K. pneumoniae isolates recovered from adult patients, neonates, and hospital tap water samples.

RESULTS

The draft genomes of the isolates varied in size, ranging from 5.48 to 5.96 Mbp suggesting the genome plasticity of this pathogen. Various genes conferring resistance to different classes of antibiotics e.g., aminoglycosides, quinolones, sulfonamides, tetracycline, and trimethoprim were identified in all sequenced isolates. The highest resistance was observed towards carbapenems, which has been putatively linked to the presence of both class B and class D carbapenemases, blaNDM, and blaOXA, respectively. Moreover, the biocide resistance gene qacEdelta1 was found in 6/10 of the sequenced strains. The sequenced isolates exhibited a broad range of sequence types and capsular types. The significant antibiotic resistance genes (ARGs) were bracketed by a variety of mobile genetic elements (MGEs). Various spontaneous mutations in genes other than the acquired antibiotic-resistance genes were observed, which play an indirect role in making these bugs resistant to antibiotics. Loss or deficiency of outer membrane porins, combined with ESBL production, played a significant role in carbapenem resistance in our sequenced isolates. Phylogenetic analysis revealed that the study isolates exhibited evolutionary relationships with strains from China, India, and the USA suggesting a shared evolutionary history and potential dissemination of similar genes amongst the isolates of different origins.

CONCLUSIONS

This study provides valuable insight into the presence of multiple mechanisms of carbapenem resistance in K. pneumoniae strains including the acquisition of multiple antibiotic-resistance genes through mobile genetic elements. Identification of rich mobilome yielded insightful information regarding the crucial role of insertion sequences, transposons, and integrons in shaping the genome of bacteria for the transmission of various resistance-associated genes. Multi-drug resistant isolates that had the fewest resistance genes exhibited a significant number of mutations. K. pneumoniae isolate from water source displayed comparable antibiotic resistance determinants to clinical isolates and the highest number of virulence-associated genes suggesting the possible interplay of ARGs amongst bacteria from different sources.

Occurrence, antibiotic resistance profiles and associated risk factors of Klebsiella pneumoniae in poultry farms in selected districts of Somalia Reginal State, Ethiopia

BACKGROUND

Klebsiella pneumoniae is an opportunistic infection that causes production losses and death in the chicken industry. A cross-sectional study was conducted on exotic chicken breeds reared at the Jigjiga poultry farm from November 2022 to May 2023 to estimate the occurrence, associated risk factors, and antimicrobial susceptibility profiles of Klebsiella pneumoniae. The chickens were selected using systematic random sampling techniques. A total of 384 cloacal swabs were collected aseptically and transported to the laboratory for analysis. For statistical analysis, STATA® version 14.0 statistical software was used.

RESULTS

From 384 examined faecal samples, 258 (67.2%) prevalences of Klebsiella pneumoniae were found. Furthermore, the association of the study's risk factors with the prevalence of Klebsiella pneumoniae was explored, and no statistically significant association was identified between sex and age. Nonetheless, relative prevalence at the age level was higher in chickens aged 12 months (67.6%) and Sasso breeds (90.0%). Similarly, male chickens and those raised for meat and egg production had a high prevalence rate of 72.5 and 75.8%, respectively. A total of 30 isolated Klebsiella pneumoniae colonies were tested in vitro for antibiotic sensitivity for six drugs, and it was shown that Klebsiella pneumoniae is moderately sensitive to Penicillin G (43.3%) while having higher resistance to Oxytetracycline (80.0%).

CONCLUSIONS

The current findings revealed that the research area had the highest prevalence of Klebsiella pneumoniae, and the isolates were resistant to commonly used drugs in the study area. Thus, a long-term intervention plan, thorough research to determine a nationwide status, as well as further multi-drug resistance patterns and molecular characterization, were urged.

A challenging case of carbapenem resistant Klebsiella pneumoniae-related pyogenic liver abscess with capsular polysaccharide hyperproduction: a case report

BACKGROUND

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections are a major public health problem, necessitating the administration of polymyxin E (colistin) as a last-line antibiotic. Meanwhile, the mortality rate associated with colistin-resistant K. pneumoniae infections is seriously increasing. On the other hand, importance of administration of carbapenems in promoting colistin resistance in K. pneumoniae is unknown.

CASE PRESENTATION

We report a case of K. pneumoniae-related pyogenic liver abscess in which susceptible K. pneumoniae transformed into carbapenem- and colistin-resistant K. pneumoniae during treatment with imipenem. The case of pyogenic liver abscess was a 50-year-old man with diabetes and liver transplant who was admitted to Abu Ali Sina Hospital in Shiraz. The K. pneumoniae isolate responsible for community-acquired pyogenic liver abscess was isolated and identified. The K. pneumoniae isolate was sensitive to all tested antibiotics except ampicillin in the antimicrobial susceptibility test and was identified as a non-K1/K2 classical K. pneumoniae (cKp) strain. Multilocus sequence typing (MLST) identified the isolate as sequence type 54 (ST54). Based on the patient's request, he was discharged to continue treatment at another center. After two months, he was readmitted due to fever and progressive constitutional symptoms. During treatment with imipenem, the strain acquired blaOXA-48 and showed resistance to carbapenems and was identified as a multidrug resistant (MDR) strain. The minimum inhibitory concentration (MIC) test for colistin was performed by broth microdilution method and the strain was sensitive to colistin (MIC < 2 µg/mL). Meanwhile, on blood agar, the colonies had a sticky consistency and adhered to the culture medium (sticky mucoviscous colonies). Quantitative real-time PCR and biofilm formation assay revealed that the CRKP strain increased capsule wzi gene expression and produced slime in response to imipenem. Finally, K. pneumoniae-related pyogenic liver abscess with resistance to a wide range of antibiotics, including the last-line antibiotics colistin and tigecycline, led to sepsis and death.

CONCLUSIONS

Based on this information, can we have a theoretical hypothesis that imipenem is a promoter of resistance to carbapenems and colistin in K. pneumoniae? This needs more attention.

Draft genome sequence of Klebsiella pneumoniae KLEB-33: a convergent biofilm hyperforming multiresistant strain belonging to the emerging ST16 lineage harboring multiple hypervirulence genes

The emergence of convergent Klebsiella pneumoniae strains showing multiresistance, characteristic of nosocomial pathotypes and hypervirulent traits typical of community-acquired isolates, makes them important models for studying K. pneumoniae pathogenesis. Here, we describe the convergent, multidrug-resistant KLEB-33 strain harboring several hypervirulence genes and make its genome available to the scientific community.

Virulent Klebsiella pneumoniae ST11 clone carrying blaKPC and blaNDM from patients with and without COVID-19 in Brazil

AIMS

Investigated and compared the occurrence of virulence genes fimH, mrkD, irp2, entB, cps, rmpA, and wabG, resistance genes blaKPC and blaNDM, and the genetic variability and clonal relationship of 29 Klebsiella pneumoniae clinical isolates of patients with and without COVID-19, from a hospital in Brazil.

METHODS AND RESULTS

All isolates were resistant to beta-lactams. The genes were investigated by PCR, and for molecular typing, enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) and MLST were used. The detection of blaNDM was greater (n = 23) when compared to that of blaKPC (n = 14). The virulence genes that most occurred were fimH, entB, cps, and wabG, which are responsible for adhesins, siderophore enterobactin, capsule, and lipopolysaccharides, respectively. Among the isolates, 21 distinct genetic profiles were found by ERIC-PCR, with multiclonal dissemination. Four isolates belonged to the ST11 clone.

CONCLUSIONS

The occurrence of the ST11 is worrying as it is a high-risk clone involved in the dissemination of virulent strains throughout the world.