Hypervirulence and hypermucoviscosity: Two different but complementary Klebsiella spp. phenotypes?

Hypervirulent Klebsiella pneumoniae in a South African tertiary hospital-Clinical profile, genetic determinants, and virulence in Caenorhabditis elegans

Introduction

A distinct strain of Klebsiella pneumoniae (K. pneumoniae) referred to as hypervirulent (hvKp) is associated with invasive infections such as pyogenic liver abscess in young and healthy individuals. In South Africa, limited information about the prevalence and virulence of this hvKp strain is available. The aim of this study was to determine the prevalence of hvKp and virulence-associated factors in K. pneumoniae isolates from one of the largest tertiary hospitals in a South African province.

Methods

A total of 74 K. pneumoniae isolates were received from Pelonomi Tertiary Hospital National Health Laboratory Service (NHLS), Bloemfontein. Virulence-associated genes (rmpA, capsule serotype K1/K2, iroB and irp2) were screened using Polymerase Chain Reaction (PCR). The iutA (aerobactin transporter) gene was used as a primary biomarker of hvKp. The extracted DNAs were sequenced using the next-generation sequencing pipeline and the curated sequences were used for phylogeny analyses using appropriate bioinformatic tools. The virulence of hvKp vs. classical Klebsiella pneumoniae (cKp) was investigated using the Caenorhabditis elegans nematode model.

Results

Nine (12.2%) isolates were identified as hvKp. Moreover, hvKp was significantly (p < 0.05) more virulent in vivo in Caenorhabditis elegans relative to cKp. The virulence-associated genes [rmpA, iroB, hypermucoviscous phenotype (hmv) phenotype and capsule K1/K2] were significantly (p < 0.05) associated with hvKp. A homology search of the curated sequences revealed a high percentage of identity between 99.8 and 100% with other homologous iutA gene sequences of other hvKp in the GenBank.

Conclusion

Findings from this study confirm the presence of hvKp in a large tertiary hospital in central South Africa. However, the low prevalence and mild to moderate clinical presentation of infected patients suggest a marginal threat to public health. Further studies in different settings are required to establish the true potential impact of hvKp in developing countries.

Pyogenic liver abscess caused by an atypical hypervirulent Klebsiella pneumoniae K1-ST23 in Mexico

Hypervirulent K. pneumoniae infection has been raising worldwide and is one of the major causes of community-acquired pyogenic liver abscess. We described a case report of pyogenic liver abscess caused by an atypical hypervirulent (non-hypermucoviscous) K. pneumoniae K1 ST23 in a diabetic Asian patient who resided in Mexico. The susceptibility to antimicrobials, pathogenicity, molecular and genomic analysis were determined. A man from Guangdong (China) with a recent diagnosis of diabetes mellitus was admitted to the hospital, and he denied traveling in the last 3 months. A computed tomography revealed a right lobe liver abscess. On the third day after admission a Klebsiella pneumoniae isolate (14652) was obtained. The isolate corresponded to a susceptible K. pneumoniae with capsular type K1 and ST23 (CG23) and exhibited a non-hypermucoviscous phenotype. The isolate 14652 was genetically related to the globally distributed lineage ST23-KL1. This study describes the first case in Mexico of K. pneumoniae capsular type K1 and ST23 with an atypical hypervirulent phenotype.

Molecular characterization of hypermucoviscous carbapenemase-encoding Klebsiella pneumoniae isolates from an Egyptian hospital

This study aimed to screen antibiotic resistance and virulence genes in carbapenem-resistant hypermucoviscous Klebsiella pneumoniae isolates from an Egyptian hospital. Among 38 previously confirmed carbapenem-nonsusceptible K. pneumoniae isolates, a string test identified three isolates as positive for hypermucoviscosity. Phenotypic characterization and molecular detection of carbapenemase- and virulence-encoding genes were performed. PCR-based multilocus sequence typing and phylogenetics were used to determine the clonality and global epidemiology of the strains. The coexistence of virulence and resistance genes in the isolates was analyzed statistically using a chi-square test. Three isolates showed the presence of carbapenemase-encoding genes (blaNDM, blaVIM, and blaIMP), adhesion genes (fim-H-1 and mrkD), and siderophore genes (entB); the isolates belonged to sequence types (STs) 101, 1310, and 1626. The relatedness between these sequence types and the sequence types of globally detected hypermucoviscous K. pneumoniae that also harbor carbapenemases was determined. Our analysis showed that the resistance and virulence profiles were not homogenous. Phylogenetically, different clones clustered together. There was no significant association between the presence of resistance and virulence genes in the isolates. There is a need for periodic surveillance of the healthcare settings in Egypt and globally to understand the true epidemiology of carbapenem-resistant, hypermucoviscous K. pneumoniae.

Community-Acquired Solitary Brain Abscesses Caused by Hypervirulent Klebsiella pneumoniae in a Healthy Adult

A 42-year-old man was admitted to the emergency room complaining of fever and headache. His cerebrospinal fluid showed a cloudy appearance, and his white blood cell count was elevated at 2460/mm3, with a predominance of neutrophils (81%), and abnormal protein and glucose levels (510.7 mg/dL and 5 mg/dL, respectively). A lobulated lesion with rim enhancement, suggestive of abscess, was detected through magnetic resonance imaging. Klebsiella pneumoniae was detected in nasopharyngeal swab and blood cultures. The capsular serotype of K. pneumoniae was K2 and the sequence type determined by multilocus sequence typing was 23. The hypervirulent phenotype was associated with multiple virulent genes, including rmpA, rmpA2, entB, ybtS, kfu, iucA, iutA, iroB mrkD, allS, peg-344, peg-589, and peg-1631. After six weeks of receiving appropriate antibiotics and exhibiting clinical resolution of the brain abscesses, the patient was discharged. We present the first reported case of a healthy community-dwelling adult with solitary brain abscesses, and no other invasive abscesses, related to hypervirulent K. pneumoniae.

Clinical and Microbiologic Analysis of Klebsiella pneumoniae Infection: Hypermucoviscosity, Virulence Factor, Genotype, and Antimicrobial Susceptibility

Hypervirulent Klebsiella pneumoniae (KP) is defined according to hypermucoviscosity or various virulence factors and is clinically associated with community-acquired liver abscess (CLA). In this study, we investigated the clinical and microbiological characteristics of KP and significant factors associated with hypervirulence. The clinical characteristics, antimicrobial susceptibility, hypermucoviscosity, serotypes, hypervirulence-related genes, and biofilm formation of 414 KP isolates collected from the Keimyung University Dongsan Hospital between December 2013 and November 2015 were analyzed according to CLA. Significant risk factors for hypervirulent KP (HvKP) associated with CLA were investigated using logistic regression analysis. Notably, 155 (37.4%) isolates were hypermucoviscous, and 170 (41.1%) harbored aerobactin. CLA was present in 34 cases (8.2%). Epidemiology and treatment outcomes did not differ significantly between the CLA and non-CLA groups. The CLA group had significantly higher antibiotic susceptibility, K1/K2, rmpA, magA, allS, kfu, iutA, string test-positive result, and biofilm mass. Multivariate logistic regression revealed rmpA (OR, 5.67; 95% CI, 2.09-15.33; p = 0.001), magA (OR, 2.34; 95% CI, 1.01-5.40; p = 0.047), and biofilm mass >0.80 (OR, 2.13; 95% CI, 1.00-4.56; p = 0.050) as significant risk factors for CLA. rmpA was identified as the most significant risk factor for CLA among KP strains, implying that it is an important factor associated with HvKP.

The Rapid Emergence of Hypervirulent Klebsiella Species and Burkholderia pseudomallei as Major Health Threats in Southeast Asia: The Urgent Need for Recognition as Neglected Tropical Diseases

The World Health Organization (WHO)'s list of neglected tropical diseases (NTDs) highlights conditions that are responsible for devastating health, social and economic consequences, and yet, they are overlooked and poorly resourced. The NTD list does not include conditions caused by Gram-negative bacilli (GNB). Infections due to GNB cause significant morbidity and mortality and are prevalent worldwide. Southeast Asia is a WHO region of low- and middle-income countries carrying the largest burden of NTDs. Two significant health threats in Southeast Asia are Burkholderia pseudomallei (causing melioidosis) and hypervirulent Klebsiella pneumoniae (HvKp). Both diseases have high mortality and increasing prevalence, yet both suffer from a lack of awareness, significant under-resourcing, incomplete epidemiological data, limited diagnostics, and a lack of evidence-based treatment. Emerging evidence shows that both melioidosis and HvKp are spreading globally, including in high-income countries, highlighting the potential future global threat they pose. In this article, we review both conditions, identifying current trends and challenges in Southeast Asia and areas for future research. We also argue that melioidosis and HvKp merit inclusion as NTDs, and that mandatory global surveillance and reporting systems should be established, and we make an urgent call for research to better understand, detect, and treat these neglected diseases.

A unique case of hypervirulent Klebsiella pneumoniae acute cholecystitis complicated by portal vein thrombophlebitis: A case report and literature review

Hypervirulent Klebsiella pneumoniae remains a significant global public health concern, characterized by a unique syndrome involving monomicrobial primary pyogenic liver abscesses, often leading to metastatic complications such as endophthalmitis, meningitis, and other infections. These infections are frequently observed in immunocompetent hosts or diabetic patients, particularly those of Asian ethnicity. In this report, we present the case of a 66-year-old Burmese female, currently residing in the United States, who presented with severe swelling, pain, discharge, and vision loss in her left eye, along with abdominal pain. Subsequent investigation revealed monomicrobial Klebsiella pneumoniae acute cholecystitis with an adjacent liver abscess, complicated by bacteremia, endogenous endophthalmitis, and portal vein thrombosis. Treatment with ceftriaxone proved successful in addressing her intra-abdominal infections, while anticoagulation therapy was initiated following multidisciplinary discussions among all involved subspecialties. Early diagnosis and the timely administration of appropriate treatment are crucial in reducing mortality and preventing further complications.

Analysis of virulence profiles in clinical isolates of Klebsiella pneumoniae from renal abscesses: clinical significance of hypervirulent isolates

Introduction

Klebsiella pneumoniae can cause a wide range of infections. Hypervirulent K. pneumoniae (hvKp), particularly associated with the K1 and K2 capsular types, is an increasingly significant microorganism with the potential to cause invasive infections, including renal abscesses. Despite the rising prevalence of hvKp infections, information on renal abscesses caused by K. pneumoniae is limited, and the clinical significance of hvKp associated with specific virulence genes remains elusive.

Methods

This study performed at a 1200-bed tertiary hospital sought to identify the clinical and microbiological characteristics of renal abscesses caused by K. pneumoniae, focusing on various virulence genes, including capsular serotypes and multilocus sequence typing (MLST).

Results

Over an 8-year period, 64 patients with suspected renal abscesses were reviewed. Ten patients diagnosed with K. pneumoniae-related renal abscesses were ultimately enrolled in the study. Among the isolates from the 10 patients, capsular serotype K2 was predominant (40.0%), followed by K1 (30.0%). The most common sequence type by MLST was 23 (40.0%). In particular, six patients (60.0%) harbored specific genes indicative of hvKp: iucA, peg-344, rmpA, and rmpA2.

Conclusions

Our findings highlight the importance of hvKp as a pathogen in renal abscesses. Although the nature of hvKp is relatively unknown, it is widely recognized as a highly virulent pathogen that can infect relatively healthy individuals of various ages and simultaneously cause infections at multiple anatomical sites. Therefore, when treating patients with K. pneumoniae-related renal abscesses, caution is necessary when considering the characteristics of hvKp, such as potential bacteremia, multi-organ abscess formation, and metastatic spread.

Klebsiella pneumoniae ST147 harboring blaNDM-1, multidrug resistance and hypervirulence plasmids

The spread of hypervirulent (hv) and carbapenem-/multidrug-resistant Klebsiella pneumoniae is an emerging problem in healthcare settings. The New Delhi metallo-β-lactamase-1 (blaNDM-1) is found in Enterobacteriaceae including K. pneumoniae. The blaNDM-1 is capable of hydrolyzing β-lactam antibiotics which are used for treatment of severe infections caused by multidrug-resistant Gram-negative bacteria. This is associated with the unacceptably high mortality rate in immunocompromised burn injury patients. This study reports on the characterization of blaNDM-1 gene and virulence factors in hv carbapenem-/multidrug-resistant K. pneumoniae ST147 in the burns unit of a tertiary teaching hospital during routine surveillance. Two K. pneumoniae strains were obtained from wounds of burn-infected patients from May 2020 to July 2021. The hypervirulence genes and genetic context of the blaNDM-1 gene and mobile genetic elements potentially involved in the transposition of the gene were analyzed. We identified a conserved genetic background and an IS26 and open reading frame flanking the blaNDM-1 gene that could suggest its involvement in the mobilization of the gene. The plasmid harbored additional antibiotic resistance predicted regions that were responsible for resistance to almost all the routinely used antibiotics. To ensure the identification of potential outbreak strains during routine surveillance, investigations on resistance genes and their environment in relation to evolution are necessary for molecular epidemiology.IMPORTANCEData obtained from this study will aid in the prompt identification of disease outbreaks including evolving resistance and virulence of the outbreak bacteria. This will help establish and implement antimicrobial stewardship programs and infection prevention protocols in fragile health systems in countries with limited resources. Integration of molecular surveillance and translation of whole-genome sequencing in routine diagnosis will provide valuable data for control of infection. This study reports for the first time a high-risk clone K. pneumoniae ST147 with hypervirulence and multidrug-resistance features in Ghana.

Comparative analysis of multidrug-resistant Klebsiella pneumoniae strains of food and human origin reveals overlapping populations

Given the increasing incidence of multidrug-resistant (MDR) Klebsiella pneumoniae infections, it is of great interest to investigate the risk of transmission associated with the prevalence of this pathogen. Some studies have described fresh raw poultry meat as a reservoir of MDR K. pneumoniae, including clinically relevant sequence types (ST) and extended-spectrum β-lactamase (ESBL) strains, indicating possible consumer exposure. This study compared 47 MDR strains of K. pneumoniae from poultry meat and human clinical isolates to assess similarities, including analysis of antimicrobial resistance profiles and virulence factors involved in infection. In addition, several biofilm culture methods were evaluated for reproducible assessment of biofilm formation in K. pneumoniae strains. Globally, no association between strain origin and STs, hypermucoviscosity, biofilm formation or serum resistance could be found between isolates of food and clinical origin, nor an associated AMR pattern, suggesting overlapping populations. We found that LB supplemented with glucose in microaerobiosis was the best discrimination condition for biofilm formation in the active attachment biofilm cultivation model. The biofilm formation capacity was strongly dependent on culture conditions, with a strain-specific response, but only a minor increase in biofilm levels was recorded in clinical K. pneumoniae populations. Our results suggest that a similar risk of zoonosis transmission from potentially virulent foodborne strains previously observed in E. coli is also present in this high-priority pathogen. This study further confirms that foodborne isolates of K. pneumoniae pose a risk to consumers and therefore this pathogen should be included in the surveillance of foodborne pathogens with high risk of MDR infections and therapeutic failure.

Multidrug-resistant clinical K. pneumoniae ST16, ST218, and ST283 and emergence of pandrug-resistant KPC-positive ST6434/K2 lineage in Iraq

BACKGROUND AND AIM

The increasing incidence of Klebsiella pneumoniae infections, both in the community and in hospitals, is a huge health problem. This is due to the increasing resistance of the bacteria to antibiotics and biofilm formation, as well as the presence of a capsule. This study focuses on two main objectives: to survey the most common capsular types in local isolates for the first time in Anbar, Iraq, on molecular level and to distinguish between infectious pathogen strains using multilocus sequence typing (MLST) for more efficient epidemiological and surveillance analysis, in order to determine the source of these strains (invasive or purebred).

METHODOLOGY

Multidrug-resistant (MDR) isolates adapted to genomic extraction and molecular screening of capsular type and MLST, and then to data processing by Pasteur Institut.

RESULTS

For the first time, one isolate was registered as a new strain in the world with ST 6434; the other strains demonstrated as preregistered with ST16, ST218, and ST283. 33% of MDR isolates belonged to the capsular K2 type.

CONCLUSION

The study's findings were not aligned with the global knowledge base about the distribution of capsular type in Asia. To prevent the spread of highly resistant strains, careful monitoring of virulence determinants is necessary in addition to the observation of antibiotic resistance.

Presence of hypervirulence-associated determinants in Klebsiella pneumoniae from hospitalised patients in Germany

BACKGROUND

Klebsiella (K.) pneumoniae is a ubiquitous Gram-negative bacterium and a common coloniser of animals and humans. Today, K. pneumoniae is one of the most persistent nosocomial pathogens worldwide and poses a severe threat/burden to public health by causing urinary tract infections, pneumonia and bloodstream infections. Infections mainly affect immunocompromised individuals and hospitalised patients. In recent years, a new type of K. pneumoniae has emerged associated with community-acquired infections such as pyogenic liver abscess in otherwise healthy individuals and is therefore termed hypervirulent K. pneumoniae (hvKp). The aim of this study was the characterisation of K. pneumoniae isolates with properties of hypervirulence from Germany.

METHODS

A set of 62 potentially hypervirulent K. pneumoniae isolates from human patients was compiled. Inclusion criteria were the presence of at least one determinant that has been previously associated with hypervirulence: (I) clinical manifestation, (II) a positive string test as a marker for hypermucoviscosity, and (III) presence of virulence associated genes rmpA and/or rmpA2 and/or magA. Phenotypic characterisation of the isolates included antimicrobial resistance testing by broth microdilution. Whole genome sequencing (WGS) was performed using Illumina® MiSeq/NextSeq to investigate the genetic repertoire such as multi-locus sequence types (ST), capsule types (K), further virulence associated genes and resistance genes of the collected isolates. For selected isolates long-read sequencing was applied and plasmid sequences with resistance and virulence determinants were compared.

RESULTS

WGS analyses confirmed presence of several signature genes for hvKp. Among them, the most prevalent were the siderophore loci iuc and ybt and the capsule regulator genes rmpA and rmpA2. The most dominant ST among the hvKp isolates were ST395 capsule type K2 and ST395 capsule type K5; both have been described previously and were confirmed by our data as multidrug-resistant (MDR) isolates. ST23 capsule type K1 was the second most abundant ST in this study; this ST has been described as commonly associated with hypervirulence. In general, resistance to beta-lactams caused by the production of extended-spectrum beta-lactamases (ESBL) and carbapenemases was observed frequently in our isolates, confirming the threatening rise of MDR-hvKp strains.

CONCLUSIONS

Our study results show that K. pneumoniae strains that carry several determinants of hypervirulence are present for many years in Germany. The detection of carbapenemase genes and hypervirulence associated genes on the same plasmid is highly problematic and requires intensified screening and molecular surveillance. However, the non-uniform definition of hvKp complicates their detection. Testing for hypermucoviscosity alone is not specific enough to identify hvKp. Thus, we suggest that the classification of hvKp should be applied to isolates that not only fulfil phenotypical criteria (severe clinical manifestations, hypermucoviscosity) but also (I) the presence of at least two virulence loci e.g. iuc and ybt, and (II) the presence of rmpA and/or rmpA2.

Differentiation of hypervirulent and classical Klebsiella pneumoniae with acquired drug resistance

Distinguishing hypervirulent (hvKp) from classical Klebsiella pneumoniae (cKp) strains is important for clinical care, surveillance, and research. Some combinations of iucA, iroB, peg-344, rmpA, and rmpA2 are most commonly used, but it is unclear what combination of genotypic or phenotypic markers (e.g., siderophore concentration, mucoviscosity) most accurately predicts the hypervirulent phenotype. Furthermore, acquisition of antimicrobial resistance may affect virulence and confound identification. Therefore, 49 K. pneumoniae strains that possessed some combinations of iucA, iroB, peg-344, rmpA, and rmpA2 and had acquired resistance were assembled and categorized as hypervirulent hvKp (hvKp) (N = 16) or cKp (N = 33) via a murine infection model. Biomarker number, siderophore production, mucoviscosity, virulence plasmid's Mash/Jaccard distances to the canonical pLVPK, and Kleborate virulence score were measured and evaluated to accurately differentiate these pathotypes. Both stepwise logistic regression and a CART model were used to determine which variable was most predictive of the strain cohorts. The biomarker count alone was the strongest predictor for both analyses. For logistic regression, the area under the curve for biomarker count was 0.962 (P = 0.004). The CART model generated the classification rule that a biomarker count = 5 would classify the strain as hvKP, resulting in a sensitivity for predicting hvKP of 94% (15/16), a specificity of 94% (31/33), and an overall accuracy of 94% (46/49). Although a count of ≥4 was 100% (16/16) sensitive for predicting hvKP, the specificity and accuracy decreased to 76% (25/33) and 84% (41/49), respectively. These findings can be used to inform the identification of hvKp.IMPORTANCEHypervirulent Klebsiella pneumoniae (hvKp) is a concerning pathogen that can cause life-threatening infections in otherwise healthy individuals. Importantly, although strains of hvKp have been acquiring antimicrobial resistance, the effect on virulence is unclear. Therefore, it is of critical importance to determine whether a given antimicrobial resistant K. pneumoniae isolate is hypervirulent. This report determined which combination of genotypic and phenotypic markers could most accurately identify hvKp strains with acquired resistance. Both logistic regression and a machine-learning prediction model demonstrated that biomarker count alone was the strongest predictor. The presence of all five of the biomarkers iucA, iroB, peg-344, rmpA, and rmpA2 was most accurate (94%); the presence of ≥4 of these biomarkers was most sensitive (100%). Accurately identifying hvKp is vital for surveillance and research, and the availability of biomarker data could alert the clinician that hvKp is a consideration, which, in turn, would assist in optimizing patient care.

ST218 Klebsiella pneumoniae became a high-risk clone for multidrug resistance and hypervirulence

BACKGROUND

The occurrence of multidrug-resistant and hypervirulent Klebsiella pneumoniae (MDR-hvKp) worldwide poses a great challenge for public health. Few studies have focused on ST218 MDR-hvKp.

METHODS

Retrospective genomic surveillance was conducted at the Peking University Third Hospital from 2017 and clinical information was obtained. To understand genomic and microbiological characteristics, antimicrobial susceptibility testing, plasmid conjugation and stability, biofilm formation, serum killing, growth curves and whole-genome sequencing were performed. We also assessed the clinical and microbiological characteristics of ST218 compared with ST23.

RESULTS

A total of eleven ST218 Kp isolates were included. The most common infection type was lower respiratory tract infection (72.7%, 8/11) in our hospital, whereas ST23 hvKp (72.7%, 8/11) was closely associated with bloodstream infection. Notably, nosocomial infections caused by ST218 (54.5%, 6/11) was slightly higher than ST23 (36.4%, 4/11). All of the ST218 and ST23 strains presented with the virulence genes combination of iucA + iroB + peg344 + rmpA + rmpA2. Interestingly, the virulence score of ST218 was lower than ST23, whereas one ST218 strain (pPEKP3107) exhibited resistance to carbapenems, cephalosporins, β-lactamase/inhibitors and quinolones and harbored an ~ 59-kb IncN type MDR plasmid carrying resistance genes including blaNDM-1, dfrA14 and qnrS1. Importantly, blaNDM-1 and qnrS1 were flanked with IS26 located within the plasmid that could successfully transfer into E. coli J53. Additionally, PEKP2044 harbored an ~ 41-kb resistance plasmid located within tetA indicating resistance to doxycycline.

CONCLUSION

The emergence of blaNDM-1 revealed that there is great potential for ST218 Kp to become a high-risk clone for MDR-hvKp, indicating the urgent need for enhanced genomic surveillance.

Plant-Origin Components: New Players to Combat Antibiotic Resistance in Klebsiella pneumoniae

Klebsiella pneumoniae (Kpn) is an opportunistic pathogen that causes intrahospital complications such as pneumonia, liver abscesses, soft tissue infections, urinary infections, bacteraemia, and, in some cases, death. Since this bacterium has a higher frequency than other Gram-negative pathogens, it has become an important pathogen to the health sector. The adaptative genome of Kpn likely facilitates increased survival of the pathogen in diverse situations. Therefore, several studies have been focused on developing new molecules, synergistic formulations, and biomaterials that make it possible to combat and control infections with and dispersion of this pathogen. Note that the uncontrolled antibiotic administration that occurred during the pandemic led to the emergence of new multidrug-resistant strains, and scientists were challenged to overcome them. This review aims to compile the latest information on Kpn that generates intrahospital infections, specifically their pathogenicity-associated factors. Furthermore, it explains the natural-product-based treatments (extracts and essential oils) developed for Kpn infection and dispersion control.

Differences in molecular characteristics and expression of virulence genes in carbapenem-resistant and sensitive Klebsiella pneumoniae isolates in Ningbo, China

Background

In recent years, Klebsiella pneumoniae has attracted attention because of its increasing drug resistance. At the same time, the migration and pathogenicity caused by its virulence genes also bring many difficulties to the diagnosis and treatment of clinical infections. However, it is currently unclear whether there are differences in virulence and pathogenicity with changes in drug resistance.

Objective

To understand the differences in molecular characteristics and expression of virulence genes in carbapenem-resistant Klebsiella pneumoniae (CRKP) and carbapenem-sensitive Klebsiella pneumoniae (CSKP).

Methods

Using polymerase chain reaction (PCR), we examined capsule polysaccharide-related genes and virulence genes in 150 clinical isolates of CRKP and 213 isolates of CSKP from the local area in Ningbo, China. Multilocus sequence typing (MLST) was used to analyze the phylogenetic relationships of clinical Klebsiella pneumoniae isolates. Furthermore, real-time quantitative PCR (RT-qPCR) was used to analyze the expression differences of common virulence genes in CSKP and CRKP, and the virulence was further verified by the larval model of Galleria mellonella.

Results

The study found that the detection rates of genes rmpA, iroB, peg-344, magA, aerobactin, alls, kfu, and entB were significantly higher in CSKP compared to CRKP. The capsule gene types K1 and K2 were more common in CSKP, while K5 was more common in CRKP. Hypervirulent Klebsiella pneumoniae (hvKP) was predominantly from CSKP. CRKP strains exhibited noticeable homogeneity, with ST11 being the predominant sequence type among the strains. CSKP strains showed greater diversity in ST types, but ST23 was still the predominant sequence type. Carbapenem-sensitive hypervirulent Klebsiella pneumoniae (CS-hvKP) had higher expression of rmpA and rmpA2 genes compared to carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP). In the wax moth virulence model, the survival rate of CS-hvKP was significantly lower than that of CR-hvKP.

Conclusion

There is a significant difference in the distribution of virulence genes between CSKP and CRKP, with CSKP carrying a significantly greater number of virulence genes. Furthermore, compared to CSKP, CRKP strains exhibit noticeable homogeneity, with ST11 being the predominant sequence type among the strains. Additionally, in terms of virulence gene expression efficiency and virulence, CSKP is significantly higher than CRKP.

Comparative genomic analysis of strong biofilm-forming Klebsiella pneumoniae isolates uncovers novel ISEcp1-mediated chromosomal integration of a full plasmid-like sequence

BACKGROUND

The goal of the current study was to elucidate the genomic background of biofilm formation in Klebsiella pneumoniae.

METHODS

Clinical isolates were screened for biofilm formation using the crystal violet assay. Antimicrobial resistance (AMR) profiles were assessed by disk diffusion and broth microdilution tests. Biofilm formation was correlated to virulence and resistance genes screened by PCR. Draft genomes of three isolates that form strong biofilm were generated by Illumina sequencing.

RESULTS

Only the siderophore-coding gene iutA was significantly associated with more pronounced biofilm formation. ST1399-KL43-O1/O2v1 and ST11-KL15-O4 were assigned to the multidrug-resistant strain K21 and the extensively drug-resistant strain K237, respectively. ST1999-KL38-O12 was assigned to K57. Correlated with CRISPR/Cas distribution, more plasmid replicons and prophage sequences were identified in K21 and K237 compared to K57. The acquired AMR genes (blaOXA-48, rmtF, aac(6')-Ib and qnrB) and (blaNDM-1, blaCTX-M, aph(3')-VI, qnrS, and aac(6')-Ib-cr) were found in K237 and K21, respectively. The latter showed a novel ISEcp1-mediated chromosomal integration of replicon type IncM1 plasmid-like structure harboring blaCTX-M-14 and aph(3')-VI that uniquely interrupted rcsC. The plasmid-mediated heavy metal resistance genes merACDEPRT and arsABCDR were spotted in K21, which also exclusively carried the acquired virulence genes mrkABCDF and the hypervirulence-associated genes iucABCD-iutA, and rmpA/A2. Pangenome analysis revealed NTUH-K2044 accessory genes most frequently shared with K21.

CONCLUSIONS

While less virulent to Galleria mellonella than ST1999 (K57), the strong biofilm former, multidrug-resistant, NDM-producer K. pneumoniae K21 (ST1399-KL43-O1/O2v1) carries a novel chromosomally integrated plasmid-like structure and hypervirulence-associated genes and represents a serious threat to countries in the area.

One-year surveillance for hypervirulent Klebsiella pneumoniae detected carbapenem-resistant superbugs

Hypervirulent Klebsiella pneumoniae (hvKp) can cause infections in clinically healthy people, such as young and immunocompetent patients. Genes involved in the capsule synthesis or those encoding the siderophores have been adopted as predictors of hvKp. Certain sequence types, such as ST23 and ST86, have been associated with hvKp strains, too. The aim of this study was to investigate the presence of hvKp among 354 K. pneumoniae strains isolated from clinical samples of patients admitted to an Italian 900-bed hospital between 21 May 2021 and April 2022. All the isolates were screened by PCR for the amplification of virulence loci. Whole genome sequencing was performed in strains tested positive for at least one target gene. Thirteen out of 354 (3.7%) were hvKp. Five were wild type and belonged to the hypervirulent clones ST23, ST86, ST5, and ST375 and to the new clone ST6310. Six strains carried the blaKPC gene: three belonged to ST101, two to ST512, and one to ST395. Two isolates were ST147 and carried the blaNDM gene. Although hvKp isolation is not frequent, their presence should be systematically investigated to avoid the spreading of both virulent strains and strains with combined increase in virulence and resistance to antibiotics. PCR-based protocols are essential for surveillance of these strains, which do not always show a recognizable phenotype. Moreover, hvKp strains were isolated also from patients without history of recent foreign travels, indicating an increased spreading of these strains as well as an underestimated of their circulation so far.IMPORTANCEKlebsiella pneumoniae is a healthcare-associated pathogen frequently resistant to antibiotics. Hypervirulent strains of pneumoniae (hvKp) can spread from the primary site of infection to multiple sites causing life-threatening infections also in young otherwise healthy individuals. This study described the isolation of 13 isolates of K. pneumoniae with increased virulence in a large tertiary hospital over a 1-year period. Among them, eight strains were multidrug resistant and hypervirulent. Although these hypervirulent strains are still rare in Italy, their presence is particularly concerning since they can cause difficult-to-treat life-threatening infections. Moreover, not all the hypervirulent isolates were positive by the string test, so hvKp isolates were not always phenotypically detectable. Molecular biology techniques such as PCR amplification and next generation sequencing are therefore necessary for the detection of hvKp isolates, and surveillance programs exploiting molecular techniques are highly desirable.

Chasing the landscape for intrahospital transmission and evolution of hypervirulent carbapenem-resistant Klebsiella pneumoniae

The spread of hypervirulent carbapenem-resistant Klebsiella pneumoniae (Hv-CRKP) is a global health concern. Here, we report the intrahospital colonization and spread of Hv-CRKP isolates in a tertiary hospital from 2017 to 2022. Analyses of 90 nonredundant CRKP isolates from 72 patients indicated that Hv-CRKP transferability relies on the dominant ST11-K64 clone. Whole-genome sequencing of 11 representative isolates gave 31 complete plasmid sequences, including 12 KPC-2 resistance carriers and 10 RmpA virulence vehicles. Apart from the binary vehicles, we detected two types of fusion plasmids, favoring the cotransfer of RmpA virulence and KPC-2 resistance. The detection of ancestry/relic plasmids enabled us to establish genetic mechanisms by which rare fusion plasmids form. Unexpectedly, we found a total of five rmpA promoter variants (P9T-P13T) exhibiting distinct activities and varying markedly in their geographic distributions. CRISPR/Cas9 manipulation confirmed that an active PT11-rmpA regulator is a biomarker for the "high-risk" ST11-K64/CRKP clone. These findings suggest clonal spread and clinical evolution of the prevalent ST11-K64/Hv-CRKP clones. Apart from improved public awareness of Hv-CRKP convergence, our findings might benefit the development of surveillance (and/or intervention) strategies for the dominant ST11-K64 lineage of the Hv-CRKP population in healthcare sectors.

Involvement of Tn3 transposon in formation and transmission of hypervirulent and carbapenem-resistant Klebsiella pneumoniae

IMPORTANCE

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is resistant to most common antibiotics, becoming the most important and prevalent nosocomial opportunity pathogen. Besides, K. pneumoniae can also cause severe community-acquired infections, such as primary liver abscess and endophthalmitis. These pathogens are commonly referred to as hvKp. CRKP and hvKp have evolved separately, each occupying its own clonal lineage and exhibiting a variety of properties. Our study provides important insights into the evolutionary events related to the arousal of virulence and drug resistance in K. pneumoniae through plasmid transmission, mediated by Tn3 transposon. Our study also provides evidence that multiple mechanisms contribute to the successful transfer of non-conjugative virulence plasmid, and the involvement of transposons enhances the efficiency. A good knowledge of its transmission mechanisms is fundamental to finding effective strategies to combat these threatening pathogens. Transposons are widely present in bacteria, spreading resistance and virulence genes between the environment and humans. Therefore, emerging transposon-mediated hypervirulent and carbapenem-resistant pathogens should be highly valued.

Identification of hypervirulent Klebsiella pneumoniae based on biomarkers and Galleria mellonella infection model

BACKGROUND

Currently, clinical laboratories lack an effective method to differentiate between classical Klebsiella pneumoniae (cKP) and hypervirulent Klebsiella pneumoniae (hvKP) strains, leading to delays in diagnosing and treating hvKP infections. Previous studies have identified peg-344, iroB, iucA, prmpA, prmpA2, and siderophores (SP) yields greater than 30 μg/ml as reliable markers for distinguishing hvKP from cKp strains. However, these diagnostic tests were conducted on a relatively small study population and lacked sufficient clinical data support. In this study, hvKP strains were identified by biomarker analysis and the Galleria mellonella model. Combined with in vitro and in vivo experiments, the reliability of clinical identification method of hvKP was verified, which provided an experimental basis for timely diagnosis of hvKP infection.

RESULTS

According to the clinical data, a total of 108 strains of hvKP were preliminary screened. Among them, 94 strains were further identified using PCR analysis of biomarkers and quantitative determination of SP. The high virulence of hvKP was subsequently confirmed through infection experiments on Galleria mellonella. Additionally, susceptibility testing revealed the identification of 58 carbapenem-resistant hvKP (CR-hvKP) strains and 36 carbapenem-sensitive hvKP (CS-hvKP) strains. By comparing molecular diagnostic indexes, molecular characteristics such as high SP production of CR-hvKP were found.

CONCLUSION

The combination of clinical data and molecular diagnostic index analysis effectively enables the identification of hvKP, particularly CR-hvKP. This study provides a scientific basis for accurate clinical identification and timely treatment of hvKP.

"Superbugs" with hypervirulence and carbapenem resistance in Klebsiella pneumoniae: the rise of such emerging nosocomial pathogens in China

Although hypervirulent Klebsiella pneumoniae (hvKP) can produce community-acquired infections that are fatal in young and adult hosts, such as pyogenic liver abscess, endophthalmitis, and meningitis, it has historically been susceptible to antibiotics. Carbapenem-resistant K. pneumoniae (CRKP) is usually associated with urinary tract infections acquired in hospitals, pneumonia, septicemias, and soft tissue infections. Outbreaks and quick spread of CRKP in hospitals have become a major challenge in public health due to the lack of effective antibacterial treatments. In the early stages of K. pneumoniae development, HvKP and CRKP first appear as distinct routes. However, the lines dividing the two pathotypes are vanishing currently, and the advent of carbapenem-resistant hypervirulent K. pneumoniae (CR-hvKP) is devastating as it is simultaneously multidrug-resistant, hypervirulent, and highly transmissible. Most CR-hvKP cases have been reported in Asian clinical settings, particularly in China. Typically, CR-hvKP develops when hvKP or CRKP acquires plasmids that carry either the carbapenem-resistance gene or the virulence gene. Alternatively, classic K. pneumoniae (cKP) may acquire a hybrid plasmid carrying both genes. In this review, we provide an overview of the key antimicrobial resistance mechanisms, virulence factors, clinical presentations, and outcomes associated with CR-hvKP infection. Additionally, we discuss the possible evolutionary processes and prevalence of CR-hvKP in China. Given the wide occurrence of CR-hvKP, continued surveillance and control measures of such organisms should be assigned a higher priority.

Rare Hypermucoviscous Klebsiella pneumoniae Liver Abscess in an Active Duty Male Requiring Partial Liver Resection for Definitive Treatment

Antibiotics and drainage have largely replaced hepatic resection for the treatment of liver abscesses in the modern era; however, in cases caused by a rare strain of Klebsiella pneumoniae with a hypermucoviscous phenotype, more aggressive hepatic resection may be required. The patient is a 34-year-old male who presented to Landstuhl Regional Medical Center with a week of epigastric pain. His workup revealed a 6 cm liver abscess with growth to 10 cm in 48 hours. He underwent multiple drainage procedures at Landstuhl and then was transferred to Walter Reed where further surgical drainage was performed. Initial cultures demonstrated K. pneumoniae. He clinically improved and was able to discharge after a 2 week hospitalization. His final remaining surgical drain was removed as an outpatient, but 48 hours after removal, he was admitted to the intensive care unit in septic shock. Imaging revealed a 12 cm liver abscess, and cultures verified hypermucoviscous Klebsiella. After multidisciplinary discussion and counseling, he underwent an open right partial hepatectomy. Postoperatively he gradually recovered from his sepsis and major operation and then returned to his home in Landstuhl. This is a case of a rare hypermucoviscous variant of K. pneumoniae causing a liver abscess resistant to multiple drainage procedures, ultimately requiring open hepatic surgical resection for source control. This remains a last-resort option in the treatment of liver abscesses and should be considered early when caused by this rare strain of Klebsiella.

Detection and characterization of putative hypervirulent Klebsiella pneumoniae isolates in microbiological diagnostics

Hypervirulent Klebsiella pneumoniae strains (hvKp) can cause invasive community-acquired infections in healthy patients of all ages. In this study, the prevalence of putative hvKp in a German tertiary center was investigated and hvKp were characterized by phenotypic and molecular assays. All K. pneumoniae isolates in routine microbiological diagnostics from a single center were screened by string-testing over a period of 6 months. String-test positive (≥ 0.5 mm) isolates were re-evaluated on different media and under various conditions (aerobe, anaerobe). For string-test positive isolates, genes (magA, iutA, rmpA and rmpA2) associated with hypermucoviscosity and hypervirulence were amplified by multiplex PCR. PCR-positive isolates were subjected to whole-genome sequencing and sedimentation and biofilm formation assays. From 1310 screened K. pneumoniae isolates in clinical routine 100 isolates (7.6%) were string test positive. From these, 9% (n = 9) were defined as putative hvKp (string-test+/PCR+). Highest rate of string-test-positive isolates was observed on MacConkey agar under aerobic conditions. Amongst these nine putative hvKp isolates, the international lineage ST23 carrying hvKp-plasmid pKpVP-1 was the most common, but also a rare ST86 with pKpVP-2 was identified. All nine isolates showed hypermucoviscosity and weak biofilm formation. In conclusion, 9% of string-positive, respectively 0.69% of all K. pneumoniae isolates from routine were defined as putative hypervirulent. MacConkey agar was the best medium for hvKp screening.

Severe disseminated infection by hypermucoviscous Klebsiella pneumoniae successfully treated by intensive therapy with continuous hemodiafiltration using AN69ST: A case report and review of the literature

Klebsiella pneumoniae (Kpn) is one of the most common gram-negative bacilli causing lung, urinary tract, and biliary tract infections. However, as a distinct entity from classic Kpn, hypervirulent Kpn causing liver abscess, endophthalmitis, and lung abscess with poor prognoses has been reported mainly in East and Southeast Asia since the mid-1980s. Although the definition of hypervirulent Kpn is unclear, the hypermucoviscosity of Kpn is considered an important feature of hypervirulence. We present a case of emphysematous pyelonephritis accompanied by septic shock and acute kidney injury caused by hypermucoviscous Kpn infection that was successfully treated by intensive treatment. A 70-year-old woman with type 2 diabetes mellitus was diagnosed with emphysematous pyelonephritis, and string test-positive Kpn was detected in blood and urine cultures and percutaneous catheter drainage fluid from the renal pelvis. The patient was treated with intensive therapies including antibiotics, ventilator management, and continuous hemodiafiltration (CHDF) using AN69ST, which can absorb cytokines. During the course of treatment, the infection was complicated by pyogenic spondylitis, which was cured by antimicrobial therapy, and the patient was transferred to another hospital for rehabilitation on day 119 after admission. Hypermucoviscous Kpn infection often has a severe course, and it is important to initiate multidisciplinary treatment at an early stage, including rifampicin, which is expected to inhibit the viscosity of hypermucoviscous Kpn. In the current case, immediate CHDF using AN69ST was also considered a life-saving treatment because it improved both volume overload and neutrophil-activated hypercytokinemia.

Evaluating the incidence of ampC-β-lactamase genes, biofilm formation, and antibiotic resistance among hypervirulent and classical Klebsiella pneumoniae strains

AIM

Both immunocompetent and healthy individuals can become life-threateningly ill when exposed to the hypervirulent (hvKp) strains of Klebsiella pneumoniae (Kp). The main objectives of this study were to evaluate the presence of ampC-lactamase genes, biofilm formation, and antibiotic resistance in clinical strains of hvKp and cKp (classical K. pneumoniae).

MATERIALS AND METHODS

Kp strains were collected from patients referred to Shahidzadeh Hospital in Behbahan City, Khuzestan Province, Iran. Several techniques were used to identify hvKp. The hypermucoviscosity phenotype was determined using the string test. Isolates that developed dark colonies on tellurite agar were assumed to be hvKp strains. If any of the iucA, iutA, or peg-344 genes were detected, the isolates were classified as hvKp. Phenotypic and genotypic detection of AmpC β-lactamases of hvKp strains was performed by the combined disk method and polymerase chain reaction, respectively. In addition, crystal violet staining was used to determine the biofilm formation of these isolates.

RESULTS

For this study, 76 non-duplicative isolates of Kp were collected. Overall, 22 (28.94%) strains had positive string test results, and 31 (40.78%) isolates were grown in tellurite-containing medium. The genes iucA and iutA or peg-344 were found in 23.68% of all Kp strains and in 50% of tellurite-resistant isolates, respectively. The most effective antibiotics against hvKp isolates were tetracycline (85.52%) and chloramphenicol (63.15%). Using the cefoxitin disc diffusion method, we observed that 56.57% (43/76) of the strains were AmpC producer. A total of 30.26% (n = 23/76) of the isolates tested positive for at least one ampC gene, including blaDHA (52.63%, n = 40), blaCIT (40.78%, n = 31), blaACC (19.76%, n = 15), blaMOX (25%, n = 19), and blaFOX (43.42%, n = 33). Biofilm formation analysis revealed that most hvKp isolates were weak (n = 6, 40%) and moderate (n = 5, 33.33%) biofilm producers.

CONCLUSION

Healthcare practitioners should consider the possibility of the existence and acquisition of hvKp everywhere. The exact mechanisms of bacterial acquisition are also unknown, and it is unclear whether the occurrence of infections is related to healthcare or not. Thus, there are still many questions about hvKp that need to be investigated.

Evaluating molecular epidemiology of carbapenem non-susceptible Klebsiella pneumoniae isolates with MLST, MALDI-TOF MS, PFGE

BACKGROUND

This study aimed to evaluate antibiotic resistance genes and virulence genes and the clonal relationship of the carbapenem-nonsusceptible Klebsiella pneumoniae strains by molecular methods which are isolated from various clinical specimens from patients treated in tertiary care hospital in Turkey.

METHODS

Identification of 32 carbapenem non-susceptible K. pneumoniae were determined by VITEK-2 (BioMérieux, France) automated system. Thirteen colistin-resistant strains were tested with the broth microdilution method. Various antibiotic resistance genes and virulence genes frequently seen in carbapenem-resistant strains were screened by PCR. Immunochromatographic tests used in the rapid diagnosis of carbapenemases were compared with PCR results. In addition, PFGE, MLST and MALDI-TOF MS methods were used to determine the clonal relationship among these strains.

RESULTS

PCR demonstrated that 31 of the strains carried at least one of the carbapenemase genes. In one strain, the coexistence of blaOXA-48+NDM was shown. The most common resistance genes were determined as blaSHV (84.3%), blaCTX-M-1 (46.8%), blaOXA-48 (40.6%), blaKPC (40.6%), blaTEM (31.2%), blaNDM (18.8%) respectively. Among the virulence genes; magA (68.7%) was the most common, followed by kpn (59.3%) and K2 (9.3%). Immunochromatographic tests were found to be 100% compatible with PCR results. All colistin-resistant isolates were also found to be resistant by colistin broth microdilution. In PFGE analysis, 25 different genotypes were determined and clustering isolates were collected in 5 different clusters and the clustering rate was 35.4%. In MLST analysis, ST101 type was determined as the most common ST type with a rate of 29%. ST101 is followed by ST16, ST307, ST14, ST147, ST309, ST377, ST395 and ST2096, respectively. The compatibility rate between MALDI-TOF MS and VITEK-2 was found 94.3%, in bacterial identification. In MALDI-TOF MS typing, the maximum similarity between the strains was less than 70% and clustering not shown.

CONCLUSION

In addition to OXA-48, which is endemic in our country, it has been determined that KPC, which is more common in the world, is becoming increasingly common in our region. ST101 type was determined as the most common type between the strains. To the best of our knowledge, this is the first study that compares these three methods in our country. There may be differences between bacterial identifications made with VITEK-2 and MALDI-TOF MS. In this study, it was observed that MALDI-TOF MS analyses were not compatible with the typing of strains according to PFGE and MLST analysis results.

Differentiation of hypervirulent and classical Klebsiella pneumoniae with acquired drug resistance

Distinguishing hypervirulent (hvKp) from classical Klebsiella pneumoniae (cKp) strains is important for clinical care, surveillance, and research. Some combination of iucA, iroB, peg-344, rmpA, and rmpA2 are most commonly used, but it is unclear what combination of genotypic or phenotypic markers (e.g. siderophore concentration, mucoviscosity) most accurately predicts the hypervirulent phenotype. Further, acquisition of antimicrobial resistance may affect virulence and confound identification. Therefore, 49 K. pneumoniae strains that possessed some combination of iucA, iroB, peg-344, rmpA, and rmpA2 and had acquired resistance were assembled and categorized as hypervirulent hvKp (hvKp) (N=16) or cKp (N=33) via a murine infection model. Biomarker number, siderophore production, mucoviscosity, virulence plasmid's Mash/Jaccard distances to the canonical pLVPK, and Kleborate virulence score were measured and evaluated to accurately differentiate these pathotypes. Both stepwise logistic regression and a CART model were used to determine which variable was most predictive of the strain cohorts. The biomarker count alone was the strongest predictor for both analyses. For logistic regression the area under the curve for biomarker count was 0.962 (P = 0.004). The CART model generated the classification rule that a biomarker count = 5 would classify the strain as hvKP, resulting in a sensitivity for predicting hvKP of 94% (15/16), a specificity of 94% (31/33), and an overall accuracy of 94% (46/49). Although a count of ≥ 4 was 100% (16/16) sensitive for predicting hvKP, the specificity and accuracy decreased to 76% (25/33) and 84% (41/49) respectively. These findings can be used to inform the identification of hvKp.

Importance

Hypervirulent Klebsiella pneumoniae (hvKp) is a concerning pathogen that can cause life-threatening infections in otherwise healthy individuals. Importantly, although strains of hvKp have been acquiring antimicrobial resistance, the effect on virulence is unclear. Therefore, it is of critical importance to determine whether a given antimicrobial resistant K. pneumoniae isolate is hypervirulent. This report determined which combination of genotypic and phenotypic markers could most accurately identify hvKp strains with acquired resistance. Both logistic regression and a machine-learning prediction model demonstrated that biomarker count alone was the strongest predictor. The presence of all 5 of the biomarkers iucA, iroB, peg-344, rmpA, and rmpA2 was most accurate (94%); the presence of ≥ 4 of these biomarkers was most sensitive (100%). Accurately identifying hvKp is vital for surveillance and research, and the availability of biomarker data could alert the clinician that hvKp is a consideration, which in turn would assist in optimizing patient care.

Genomic Analysis of Carbapenem-Resistant Hypervirulent Klebsiella pneumoniae in a Chinese Tertiary Hospital

Background

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) has become a clinical crisis and is associated with significant morbidity and mortality. The prevalence of CR-hvKP has trended upward since 2010. This study aims to describe the clinical and genomic characteristics of CR-hvKP collected from a tertiary hospital in eastern China, from August 2020 to October 2021.

Methods

We tested the susceptibility to common antibiotics in these isolates to feature the antibiotic-resistant phenotypes. We also applied whole-genome sequencing and core-genome phylogenetic to analysis the genetic features of these isolates. Plasmid replicons were identified by using the PlasmidFinder database, and core-genome phylogenetic analysis by Parsnp database.

Results

All these strains isolated from the patients with serious underlying diseases and poor prognosis. We found all CR-hvKp isolates exhibited a multidrug-resistant (MDR) phenotype. These results revealed that blaKPC-2 was the predominant carbapenemases gene (n = 53, 84.1%), and ST11-KL64 CR-hvKP strains dominated, forming a single cluster, and differed by an average of 26 core SNPs. We only found eight ST15 isolates containing KL24 and KL112 type capsules, with the main carbapenem resistance genes being blaOXA-232 and blaKPC-2. All ST11-KL64 strains had a series of resistance and virulence genes, along with IncHIB-FIB virulence plasmids and IncFII resistance plasmids, while the prevalence of resistance plasmids like the IncFII plasmid was absence in ST15 isolates.

Conclusion

This suggests that ST11-KL64 CR-hvKP has emerged as the most prevalent hypervirulence and carbapenem-resistant K. pneumoniae and may contribute to hospital outbreaks of infection, which required most clinical attention.

Characterization of ST11 and ST15 Carbapenem-Resistant Hypervirulent Klebsiella pneumoniae from Patients with Ventilator-Associated Pneumonia

Background

The prevalence of carbapenem-resistant hypervirulent Klebsiella pneumoniae (hv-CRKP) is a serious public threat globally. Here, we performed clinical, molecular, and phenotypic monitoring of hv-CRKP strains isolated from the intensive care unit (ICU) to offer evidence for prevention and control in hospitals.

Methods

Data analysis of ICU patients suffering from ventilator-associated pneumonia (VAP) because of hv-CRKP infection, admitted at the Chinese Teaching Hospital between March 2019 and September 2021 was performed. Patients' antibiotic-resistance genes, virulence-associated genes, and capsular serotypes of these isolates were detected. Homology analysis of the strains was performed by MLST and PFGE. Six different strains were tested for their virulence traits using the serum killing test and the Galleria mellonella infection assay. For whole genome sequencing, KP3 was selected as a representative strain.

Results

Clinical data of 19 hv-CRKP-VAP patients were collected and their hv-CRKP were isolated, including 10 of ST11-KL64, 4 of ST15-KL112, 2 of ST11-KL47, 1 of ST15-KL19, 1 of ST17-KL140, and 1 of ST48-KL62. Four ST15 and 8 ST11 isolates revealed high homology, respectively. Most strains carried the carbapenemase gene blaKPC-2 (14/19, 73.68%), followed by blaOXA-232 (4/19, 21.05%). All strains were resistant to almost all the antibiotics except polymyxin and tigacycline. Ten patients were treated with polymyxin or tigacycline based on their susceptibility results, and unfortunately 6 patients died. All strains exhibited a hyper-viscous phenotype, and the majority (17/19, 89.47%) of them contained rmpA and rmpA2. The serum killing test showed that KP9 was resistant to normal healthy serum, others were intermediately or highly sensitive. G. mellonella larvae infection assay suggested that the strains in this study were hypervirulent.

Conclusion

This study highlights the dominant strain and molecular epidemiology of hv-CRKP in a hospital in China. We should pay more attention to the effect of hv-CRKP on VAP, strengthen monitoring and control transmission.

Hypervirulent Klebsiella pneumoniae detection methods: a minireview

Hypervirulent Klebsiella pneumoniae (hvKp), characterized by high virulence and epidemic potential, has become a global public health challenge. Therefore, improving the identification of hvKp and enabling earlier and faster detection in the community to support subsequent effective treatment and prevention of hvKp are an urgent issue. To address these issues, a number of assays have emerged, such as String test, Galleria mellonella infection test, PCR, isothermal exponential amplification, and so on. In this paper, we have collected articles on the detection methods of hvKp and conducted a retrospective review based on two aspects: traditional detection technology and biomarker-based detection technology. We summarize the advantages and limitations of these detection methods and discuss the challenges as well as future directions, hoping to provide new insights and references for the rapid detection of hvKp in the future. The aim of this study is to focus on the research papers related to Hypervirulent Klebsiella pneumoniae involving the period from 2012 to 2022. We conducted searches using the keywords "Hypervirulent Klebsiella pneumoniae, biomarkers, detection techniques" on ScienceDirect and Google Scholar. Additionally, we also searched on PubMed, using MeSH terms associated with the keywords (such as Klebsiella pneumoniae, Klebsiella Infections, Virulence, Biomarkers, diagnosis, etc.).

Antibiotic-Resistant ESKAPE Pathogens and COVID-19: The Pandemic beyond the Pandemic

Antibacterial resistance is a renewed public health plague in modern times, and the COVID-19 pandemic has rekindled this problem. Changes in antibiotic prescribing behavior, misinformation, financial hardship, environmental impact, and governance gaps have generally enhanced the misuse and improper access to antibiotics during the COVID-19 pandemic. These determinants, intersected with antibacterial resistance in the current pandemic, may amplify the potential for a future antibacterial resistance pandemic. The occurrence of infections with multidrug-resistant (MDR), extensively drug-resistant (XDR), difficult-to-treat drug-resistant (DTR), carbapenem-resistant (CR), and pan-drug-resistant (PDR) bacteria is still increasing. The aim of this review is to highlight the state of the art of antibacterial resistance worldwide, focusing on the most important pathogens, namely Enterobacterales, Acinetobacter baumannii, and Klebsiella pneumoniae, and their resistance to the most common antibiotics.

Persistent transmission of carbapenem-resistant, hypervirulent Klebsiella pneumoniae between a hospital and urban aquatic environments

The increasing prevalence of infections caused by carbapenem-resistant hypervirulent Klebsiella pneumoniae strains (CR-hvKP) prompts the question of whether these strains also circulate outside of clinical settings. However, the environmental occurrence and dissemination of CR-hvKP are poorly studied. In the current study, we investigated the epidemiological characteristics, and dissemination dynamics of carbapenem-resistant K. pneumoniae (CRKP) isolated from a hospital, an urban wastewater treatment plant (WWTP), and adjacent rivers in Eastern China during one year of monitoring. A total of 101 CRKP were isolated, 54 were determined to be CR-hvKP harboring pLVPK-like virulence plasmids, which were isolated from the hospital (29 out of 51), WWTP (23 out of 46), and rivers (2 out of 4), respectively. The period with lowest detection rate of CR-hvKP in the WWTP, August, corresponded with the lowest detection rate at the hospital. Comparing the inlet and outlet of the WWTP, no significant reduction of the detection of CR-hvKP and relative abundance of carbapenem resistance genes was observed. The detection rate of CR-hvKP and the relative abundance of carbapenemase genes were significantly higher in the WWTP in colder months compared to warmer months. Clonal dissemination of CR-hvKP clones of ST11-KL64 between the hospital and the aquatic environment, as well as the horizontal spread of IncFII-IncR and IncC plasmids carrying carbapenemase genes, was observed. Furthermore, phylogenetic analysis showed that the ST11-KL64 CR-hvKP strain has spread nationally by interregional transmission. These results indicated transmission of CR-hvKP clones between hospital and urban aquatic environments, prompting the need for improved wastewater disinfection and epidemiological models to predict the public health hazard from prevalence data of CR-hvKP.

Comparative genomics and virulome analysis reveal unique features associated with clinical strains of Klebsiella pneumoniae and Klebsiella quasipneumoniae from Trinidad, West Indies

Klebsiella pneumoniae and Klebsiella quasipneumoniae are closely related human pathogens of global concern. The more recently described K. quasipneumoniae shares similar morphological characteristics with K. pneumoniae and is commonly misidentified as this species using traditional laboratory techniques. The vast mobilome in these pathogenic bacteria influences the dissemination of virulence factors in high-risk environments and it is, therefore, critical to monitor strains for developing effective clinical management strategies. Herein, this study utilized Illumina sequencing to characterize the whole genomes of nine clinical K. pneumoniae and one K. quasipneumoniae isolate obtained from patients of 3 major hospitals in Trinidad, West Indies. Reconstruction of the assembled genomes and implementation of several bioinformatic tools revealed unique features such as high pathogenicity islands associated with the isolates. The K. pneumoniae isolates were categorized as classical (n = 3), uropathogenic (n = 5), or hypervirulent (n = 1) strains. In silico multilocus sequence typing, and phylogenetic analysis showed that isolates were related to several international high-risk genotypes, including sequence types ST11, ST15, ST86, and ST307. Analysis of the virulome and mobilome of these pathogens showed unique and clinically important features including the presence of genes associated with Type 1 and Type 3 fimbriae, the aerobactin and yersiniabactin siderophore systems, the K2 and O1/2, and the O3 and O5 serotypes. These genes were either on or in close proximity to insertion sequence elements, phage sequences, and plasmids. Several secretion systems including the Type VI system and relevant effector proteins were prevalent in the local isolates. This is the first comprehensive study investigating the genomes of clinical K. pneumoniae and K. quasipneumoniae isolates from Trinidad, West Indies. The data presented illustrate the diversity of Trinidadian clinical K. pneumoniae isolates as well as significant virulence biomarkers and mobile elements associated with these isolates. Additionally, the genomes of the local isolates will add to global databases and thus can be used in future surveillance or genomic studies in this country and the wider Caribbean region.

Molecular Characterization of the Convergent Carbapenem-Resistant and Hypervirulent Klebsiella pneumoniae Strain K1-ST23, Collected in Chile during the COVID-19 Pandemic

The aim of this study was to investigate the genomic features of a carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) isolate (K-2157) collected in Chile. Antibiotic susceptibility was determined using the disk diffusion and broth microdilution methods. Whole-genome sequencing (WGS) and hybrid assembly were performed, using data generated on the Illumina and Nanopore platforms. The mucoid phenotype was analyzed using both the string test and sedimentation profile. The genomic features of K-2157 (e.g., sequence type, K locus, and mobile genetic elements) were retrieved using different bioinformatic tools. Strain K-2157 exhibited resistance to carbapenems and was identified as a high-risk virulent clone belonging to capsular serotype K1 and sequence type 23 (ST23). Strikingly, K-2157 displayed a resistome composed of β-lactam resistance genes (blaSHV-190, blaTEM-1, blaOXA-9, and blaKPC-2), the fosfomycin resistance gene fosA, and the fluoroquinolones resistance genes oqxA and oqxB. Moreover, several genes involved in siderophore biosynthesis (ybt, iro, and iuc), bacteriocins (clb), and capsule hyperproduction (plasmid-borne rmpA [prmpA] and prmpA2) were found, which is congruent with the positive string test displayed by K-2157. In addition, K-2157 harbored two plasmids: one of 113,644 bp (KPC+) and another of 230,602 bp, containing virulence genes, in addition to an integrative and conjugative element (ICE) embedded on its chromosome, revealing that the presence of these mobile genetic elements mediates the convergence between virulence and antibiotic resistance. Our report is the first genomic characterization of a hypervirulent and highly resistant K. pneumoniae isolate in Chile, which was collected during the coronavirus disease 2019 (COVID-19) pandemic. Due to their global dissemination and public health impact, genomic surveillance of the spread of convergent high-risk K1-ST23 K. pneumoniae clones should be highly prioritized. IMPORTANCE Klebsiella pneumoniae is a resistant pathogen involved primarily in hospital-acquired infections. This pathogen is characterized by its notorious resistance to last-line antibiotics, such as carbapenems. Moreover, hypervirulent K. pneumoniae (hvKp) isolates, first identified in Southeast Asia, have emerged globally and are able to cause infections in healthy people. Alarmingly, isolates displaying a convergence phenotype of carbapenem resistance and hypervirulence have been detected in several countries, representing a serious threat to public health. In this work, we analyzed the genomic characteristics of a carbapenem-resistant hvKp isolate recovered in 2022 from a patient with COVID-19 in Chile, representing the first analysis of this type in the country. Our results will provide a baseline for the study of these isolates in Chile, which will support the adoption of local measures aimed at controlling their dissemination.

Two-Component Response Regulator OmpR Regulates Mucoviscosity through Energy Metabolism in Klebsiella pneumoniae

Hypermucoviscosity is a hallmark of hypervirulent Klebsiella pneumoniae (hvKP). However, the molecular basis of its regulation is largely unknown. We hypothesize that hypermucoviscosity is modulated via two-component signal transduction systems (TCSs). In-frame deletion mutants of all 33 response regulators of hvKP ATCC43816 were generated using CRISPR/CAS and evaluated for their impacts on hypermucoviscosity. The response regulator OmpR is required for hypermucoviscosity in vitro and virulence in vivo in a mouse pneumonia model. The ΔompR mutant lost its mucoidy but retained its capsule level and comparable rmpADC expression, so transcriptomic analysis by RNA-Seq was performed to identify differentially expressed genes (DEGs) in ΔompR mutant. The top 20 Gene Ontology terms of 273 DEGs belong to purine ribonucleotide triphosphate biosynthetic and metabolic process, transmembrane transport, and amino acid metabolism. Among the overexpressed genes in the ΔompR mutant, the atp operon encoding F-type ATP synthase and the gcvTHP encoding glycine cleavage system were characterized further as overexpression of either operon reduced the mucoviscosity and increased the production of ATP. Furthermore, OmpR directly bound the promoter region of the atp operon, not the gcvTHP, suggesting that OmpR regulates the expression of the atp operon directly and gcvTHP indirectly. Hence, the loss of OmpR led to the overexpression of F-type ATP synthase and glycine cleavage system, which altered the energetic status of ΔompR cells and contributed to the subsequent reduction in the mucoviscosity. Our study has uncovered a previously unknown regulation of bacterial metabolism by OmpR and its influence on hypermucoviscosity. IMPORTANCE Hypermucoviscosity is a critical virulent factor for Klebsiella pneumoniae infections, and its regulation remains poorly understood at the molecular level. This study aims to address this knowledge gap by investigating the role of response regulators in mediating hypermucoviscosity in K. pneumoniae. We screened 33 response regulators and found that OmpR is essential for hypermucoviscosity and virulence of K. pneumoniae in a mouse pneumonia model. Transcriptomic analysis uncovered that genes involved in energy production and metabolism are highly upregulated in the ΔompR mutant, suggesting a potential link between bacterial energy status and hypermucoviscosity. Overexpression of those genes increased production of ATP and reduced mucoviscosity, recapitulating the ΔompR mutant phenotype. Our findings provide new insights into the regulation of K. pneumoniae hypermucoviscosity by a two-component signal transduction system, highlighting the previously unknown role of OmpR in regulating bacterial energy status and its influence on hypermucoviscosity.

Global spread and evolutionary convergence of multidrug-resistant and hypervirulent Klebsiella pneumoniae high-risk clones

For people living in developed countries life span is growing at a faster pace than ever. One of the main reasons for such success is attributable to the introduction and extensive use in the clinical practice of antibiotics over the course of the last seven decades. In hospital settings, Klebsiella pneumoniae represents a well-known and commonly described opportunistic pathogen, typically characterized by resistance to several antibiotic classes. On the other hand, the broad wedge of population living in Low and/or Middle Income Countries is increasing rapidly, allowing the spread of several commensal bacteria which are transmitted via human contact. Community transmission has been the original milieu of K. pneumoniae isolates characterized by an outstanding virulence (hypervirulent). These two characteristics, also defined as "pathotypes", originally emerged as different pathways in the evolutionary history of K. pneumoniae. For a long time, the Sequence Type (ST), which is defined by the combination of alleles of the 7 housekeeping genes of the Multi-Locus Sequence Typing, has been a reliable marker of the pathotype: multidrug-resistant clones (e.g. ST258, ST147, ST101) in the Western world and hypervirulent clones (e.g. ST23, ST65, ST86) in the Eastern. Currently, the boundaries separating the two pathotypes are fading away due to several factors, and we are witnessing a worrisome convergence in certain high-risk clones. Here we review the evidence available on confluence of multidrug-resistance and hypervirulence in specific K. pneumoniae clones.

Different regulatory mechanisms of the capsule in hypervirulent Klebsiella pneumonia: "direct" wcaJ variation vs. "indirect" rmpA regulation

Introduction

Hypervirulent Klebsiella pneumoniae produce an increased amount of capsular substance and are associated with a hypermucoviscous phenotype. Capsule production is regulated by capsular regulatory genes and capsular gene cluster variations. In the present study, we focus on the effect of rmpA and wcaJon capsule biosynthesis.

Methods

Phylogenetic trees were constructed to analyze wcaJ and rmpA sequence diversity in different serotypes hypervirulent strains. Then mutant strains (K2044ΔwcaJ, K2044K1wcaJ, K2044K2wcaJand K2044K64wcaJ) were used to verify the effects of wcaJ and its diversity on capsule synthesis and strain virulence. Furthmore, the role of rmpA in capsular synthesis and its mechanisms were detected in K2044ΔrmpA strain.

Results

RmpA sequences are conversed in different serotypes. And rmpA promoted the production of hypercapsules by simultaneously acting on three promoters in cps cluster. Whereas wcaJ, its sequences are different in different serotypes, and its loss result in the termination of capsular synthesis. Moreover, the results verified that K2 wcaJ could form hypercapsule in K2044 strains (K1 serotype), but K64 wcaJ could not.

Discussion

The interaction of multiple factors is involved in capsule synthesis, including wcaJ and rmpA. RmpA, an known conserved capsular regulator gene, acts on cps cluster promoters to promote the production of the hypercapsule. WcaJ as initiating enzyme of CPS biosynthesis, its presence determines the synthesis of capsule. Besides, different from rmpA, wcaJ sequence consistency is limited to the same serotype, which cause wcaJ functioning in different serotype strains with sequence recognition specificity.

Phagocytosis is a primary determinant of pulmonary clearance of clinical Klebsiella pneumoniae isolates

Introduction

Klebsiella pneumoniae (Kp) is a common cause of hospital-acquired pneumonia. Although previous studies have suggested that evasion of phagocytic uptake is a virulence determinant of Kp, few studies have examined phagocytosis sensitivity in clinical Kp isolates.

Methods

We screened 19 clinical respiratory Kp isolates that were previously assessed for mucoviscosity for their sensitivity to macrophage phagocytic uptake, and evaluated phagocytosis as a functional correlate of in vivo Kp pathogenicity.

Results

The respiratory Kp isolates displayed heterogeneity in the susceptibility to macrophage phagocytic uptake, with 14 out of 19 Kp isolates displaying relative phagocytosis-sensitivity compared to the reference Kp strain ATCC 43816, and 5 out of 19 Kp isolates displaying relative phagocytosis-resistance. Intratracheal infection with the non-mucoviscous phagocytosis-sensitive isolate S17 resulted in a significantly lower bacterial burden compared to infection with the mucoviscous phagocytosis-resistant isolate W42. In addition, infection with S17 was associated with a reduced inflammatory response, including reduced bronchoalveolar lavage fluid (BAL) polymorphonuclear (PMN) cell count, and reduced BAL TNF, IL-1β, and IL-12p40 levels. Importantly, host control of infection with the phagocytosis-sensitive S17 isolate was impaired in alveolar macrophage (AM)-depleted mice, whereas AM-depletion had no significant impact on host defense against infection with the phagocytosis-resistant W42 isolate.

Conclusion

Altogether, these findings show that phagocytosis is a primary determinant of pulmonary clearance of clinical Kp isolates.

Recombinase-Aided Amplification Assay for Rapid Detection of Hypervirulent Klebsiella pneumoniae (hvKp) and Characterization of the hvKp Pathotype

Hypervirulent Klebsiella pneumoniae (hvKp) is a major human pathogen associated with liver abscess, pneumonia, meningitis, and endophthalmitis. It is challenging to differentiate hvKp from classical Klebsiella pneumoniae (cKp) using conventional methods, necessitating the development of a rapid, sensitive, and convenient assay for hvKp detection. In this study, we constructed a recombinase-aided amplification (RAA) method targeting hvKp genes peg344 and rmpA, and also analyzed the pathogenic characteristics of hvKp. We optimized the reaction temperature and system, and evaluated its sensitivity, specificity, and clinical application. The primer and probe sets peg344-set1 and rmpA-set2 delivered significant fluorescent signals at 39°C with the shortest gene amplification times (sensitivity: 20 copies/reaction). This RAA assay showed no cross-reactivity with 15 other common pathogenic bacteria. Its applicability was confirmed by the evaluation of 208 clinical specimens, of which 45 were confirmed to be hvKp. The sensitivity and specificity of the RAA assay were both 100% compared with real-time PCR as the reference standard. To verify the assay, we also assessed the diversity of molecular characteristics among the hvKp isolates and identified serotype K1 and sequence type ST23 as the dominant clone. Virulence factors iroN and iutA were highly associated with virulence level. In conclusion, our novel RAA assay is a powerful tool for early diagnosis and epidemiological surveillance of hvKp. IMPORTANCEKlebsiella pneumoniae is the most common opportunistic bacterial species and a major threat to public health. Since the 1990s, hvKp has received increasing attention from public health officials and infectious disease specialists. Hypervirulent strains differ from classical strains in terms of phenotypic features and clinical outcomes. It is hard to identify hvKp from cKp using the conventional methods including colony morphology analysis, serum killing assays, mouse lethality assays, string tests, and real-time PCR. In this study, we established a rapid, sensitive and convenient recombinase-aided amplification assay for hvKp detection targeting virulence genes peg344 and rmpA. Our RAA assay provides an important tool for the rapid diagnosis of infectious diseases caused by hvKp, particularly in primary laboratories.

Occurrence and Molecular Study of Hypermucoviscous/Hypervirulence Trait in Gut Commensal K. pneumoniae from Healthy Subjects

Hypervirulent Klebsiella pneumoniae (hvKp) is emerging worldwide. Hypermucoviscousity is the characteristic trait that distinguishes it from classic K. pneumoniae (cKp), which enables Kp to cause severe invasive infections. This research aimed to investigate the hypermucoviscous Kp (hmvKp) phenotype among gut commensal Kp isolated from healthy individuals and attempted to characterize the genes encoding virulence factors that may regulate the hypermucoviscosity trait. Using the string test, 50 identified Kp isolates from healthy individuals’ stool samples were examined for hypermucoviscosity and investigated by transmission electron microscopy (TEM). Antimicrobial susceptibility profiles of Kp isolates were determined using the Kirby Bauer disc method. Kp isolates were tested for genes encoding different virulence factors by PCR. Biofilm formation was assayed by the microtiter plate method. All Kp isolates were multidrug-resistant (MDR). Phenotypically, 42% of isolates were hmvKp. PCR-based genotypic testing revealed the hmvKp isolates belonged to capsular serotype K2. All study Kp isolates harbored more than one virulence gene. The genes magA and rmpA were not detected, while the terW gene was present in all isolates. The siderophores encoding genes entB and irp2 were most prevalent in hmvKp isolates (90.5%) and non-hmvKp (96.6%), respectively. hmvKp isolates harbored the genes wabG and uge with rates of 90.5% and 85.7%, respectively. The outcomes of this research highlight the potential health risk of commensal Kp to cause severe invasive diseases, owing to being hmvKp and MDR, and harboring multiple virulence genes. The absence of essential genes related to hypermucoviscosity such as magA and rmpA in hmvKp phenotypes suggests the multifactorial complexity of the hypermucoviscosity or hypervirulence traits. Thus, further studies are warranted to verify the hypermucoviscosity-related virulence factors among pathogenic and commensal Kp in different colonization niches.

Synergistic Effects of Baicalin and Levofloxacin Against Hypervirulent Klebsiella pneumoniae Biofilm In Vitro

Hypervirulent Klebsiella pneumoniae (hvKp) strains that form biofilms have recently emerged worldwide; however, the mechanisms underlying biofilm formation and disruption remain elusive. In this study, we established a hvKp biofilm model, investigated its in vitro formation pattern, and determined the mechanism of biofilm destruction by baicalin (BA) and levofloxacin (LEV). Our results revealed that hvKp exhibited a strong biofilm-forming ability, forming early and mature biofilms after 3 and 5 d, respectively. Early biofilm and bacterial burden were significantly reduced by BA + LEV and EM + LEV treatments, which destroyed the 3D structure of early biofilms. Conversely, these treatments were less effective against mature biofilm. The expression of both AcrA and wbbM was significantly downregulated in the BA + LEV group. These findings indicated that BA + LEV might inhibit the formation of hvKp biofilm by altering the expression of genes regulating efflux pumps and lipopolysaccharide biosynthesis.

Antimicrobial Resistance Pattern, Pathogenicity and Molecular Properties of Hypervirulent Klebsiella pneumonia (hvKp) among Hospital-Acquired Infections in the Intensive Care Unit (ICU)

Hypervirulent Klebsiella pneumoniae (hvKp) is a new emerging variant of K. pneumoniae that is increasingly reported worldwide. The variant hvKp is known to cause severe invasive community-acquired infections such as metastatic meningitis, pyogenic liver abscesses (PLA) and endophthalmitis, but its role in hospital-acquired infections (HAIs) is little known. The aim of this study was to evaluate the prevalence of hvKp among hospital-acquired (HA) K. pneumoniae infections in the intensive care unit (ICU) and to compare between hvKp and classical K. pneumoniae (cKP) regarding antimicrobial resistance pattern, virulence and molecular characteristics. The study was cross-sectional and included 120 ICU patients suffering from HA K. pneumoniae infections between January and September 2022. K. pneumoniae isolates were subjected to antimicrobial susceptibility testing and detection of extended-spectrum-β-lactamase (ESBL) production by the Phoenix 100 automated microbiology system, string test, biofilm formation, serum resistance assay, and detection of virulence-associated genes (rmpA, rmpA2, magA, iucA) and capsular serotype-specific genes (K1, K2, K5, K20, K57) by polymerase chain reaction (PCR). Of 120 K. pneumoniae isolates, 19 (15.8%) were hvKp. The hypermucoviscous phenotype was more significantly detected in the hvKp group than in the cKP group (100% vs. 7.9%, p ≤ 0.001). The rate of resistance to different antimicrobial agents was significantly higher in the cKP group than that in the hvKp group. Fifty-three strains were identified as ESBL-producing strains, which was more frequent in the cKP group than in the hvKp group (48/101 [47.5%] vs. 5/19 [26.3%], respectively, p ≤ 0.001). The hvKP isolates were highly associated with moderate and strong biofilm formation than cKP isolates (p = 0.018 and p = 0.043 respectively). Moreover, the hvKP isolates were highly associated with intermediate sensitivity and re sistance to serum in the serum resistance assay (p = 0.043 and p = 0.016 respectively). K1, K2, rmpA, rmpA2, magA and iucA genes were significantly associated with hvKp (p ≤ 0.001, 0.004, <0.001, <0.001, 0.037 and <0.001, respectively). However, K5, K20 and K57 were not associated with hvKp. The hvKp strains have emerged as a new threat to ICU patients because of their ability to cause more severe and life-threatening infections than cKP. The string test alone as a laboratory test for screening of hvKp has become insufficient. Recently, hvKp was defined as hypermucoviscous- and aerobactin-positive. It is important to improve the awareness towards the diagnosis and management of hvKp infections.

Rifampicin exerts anti-mucoviscous activity against hypervirulent Klebsiella pneumoniae via binding to the RNA polymerase β subunit

OBJECTIVES

In hypervirulent Klebsiella pneumoniae (hvKP), the hypermucoviscous capsule is known to be a major virulence determinant. We previously discovered that rifampicin (RFP), a bactericidal drug that binds to and inhibits the β subunit of RNA polymerase (RpoB), elicits anti-mucoviscous activity against hvKP by suppressing rmpA, a regulator of capsule production. Here, we aimed to determine whether RFP exerts this effect at sub-growth-inhibitory concentrations via its binding to RpoB.

METHODS

Five spontaneous RFP-resistant mutants (R1-R5) were prepared from an hvKP clinical isolate and subjected to whole genome sequencing and mucoviscosity analyses. Subsequently, a two-step allelic exchange procedure was used to create a rpoB mutant R6 and revertants with wild-type rpoB from R1-R5 (named R1'-R5'). Transcription levels of rmpA and the capsular polysaccharide polymerase gene magA and capsule thickness of R1-R5 and R1'-R5' grown without or with RFP were evaluated by quantitative reverse transcription polymerase chain reaction and microscopic observation using India ink staining.

RESULTS

R1-R5 all had non-synonymous point mutations in rpoB and were highly resistant to the bactericidal effects and anti-mucoviscous activity of RFP. While the properties of R6 were similar to those of R1-R5, the responses of R1'-R5' to RFP were identical to those of the wild type. rmpA and magA transcription levels and capsule thickness correlated well with the mucoviscosity levels.

CONCLUSIONS

RFP exerts anti-mucoviscous activity by binding to RpoB. The mechanism of how this causes rmpA suppression remains to be explored.

Study on Virulence Genes, Drug Resistance and Molecular Epidemiology of Klebsiella pneumoniae with High Virulence in Inner Mongolia, China

Objective

The purpose of this study was to analyse the clinical, microbiological and molecular epidemiological characteristics of patients with pyogenic liver abscess (PLA) caused by Klebsiella pneumoniae (KPN) in Inner Mongolia, China.

Methods

The KPN isolates from 78 KPN-PLA cases admitted to a tertiary teaching hospital in Baotou, Inner Mongolia, from 2016 to 2019 were studied systematically and described comprehensively. The virulence factors, drug resistance and sequence types of KPN in different samples were identified by a wire-drawing test, polymerase chain reaction, a drug susceptibility test and multi-site sequence typing.

Results

There were more male than female KPN-PLA patients (P<0.05). The mortality rate was 2.5%, and KPN-PLA was significantly associated with diabetes mellitus (P<0.05). Most of the KPN isolates in the puncture fluid of patients with KPN-PLA were hypervirulent KPN (HvKP). The positive rate of the KPN-PLA specimens was higher than that of the blood and urine specimens. The KPN isolates of the urine specimens had higher drug resistance than the other two (P<0.05). The hypermucoviscous KPN, aerobic actin (aero) (+), K1 and K2 serotypes accounted for 80.8%, 89.7%, 56.4% and 26.9%, respectively. In addition to ironB (3.8%), the detection rates of virulence factors rmpA, irp2, entB, iucD, aero, wcaG, iutA, kfu, ybtA, iron, fimH and mrkD were higher (69.2%-100.0%). The positive rate of KPN isolates of the KPN-PLA puncture fluid was higher than that of the blood and urine samples (P<0.05). In addition, ST23 was found to be the dominant ST (32.1%) of KPN-PLA in the Baotou region.

Conclusion

In the KPN-PLA specimens, the KPN isolates were more virulent than those in the blood and urine specimens, and a carbapenem-resistant HvKP strain emerged. This research will help improve the understanding of HvKP and provide useful suggestions for KPN-PLA treatments.

Relationship Between Drug Resistance Characteristics and Biofilm Formation in Klebsiella Pneumoniae Strains

Objective

To conduct epidemiological analysis of Klebsiella pneumoniae (K. pneumoniae) with hypervirulence, and to investigate its drug resistance phenotype, Extended-spectrum β-lactamase (ESBLs) gene, virulence factor, capsular serotype and biofilm formation, so as to provide theoretical basis for further understanding of the drug resistance mechanism of K. pneumoniae with hypervirulence.

Methods

K. Pneumoniae were isolated from clinical samples collected from inpatients. All strains were identified by VITEK2 Compact using fully automatic microbial analyzer, the minimal inhibitory concentration (MIC) of antibiotics was determined by microbroth dilution test. The double disk diffusion method was used to detect the production of ESBLs, modified carbapenem inactivation method (mCIM) was used to detect the production of carbapenemase, and hypermucoviscosity phenotype was detected by wire drawing test. PCR was used to detect ESBLs gene, virulence factor and capsular serotype. Crystal violet staining was used to detect the ability of biofilm formation.

Results

The ESBLs genes detected in this study included strains blaTEM 35 (36.5%), blaSHV 51 (53.1%), and blaCTX-M 49 (51.0%). Most strains carried multiple ESBLs genes, but not all of them produce ESBLs. K1 and K2 accounted for 14.6% and 11.5% respectively. Most (91.7%) strains carried the fimH gene, and the other virulence genes were ybtS (53.1%), entB (46.9%), rmpA (41.7%), aerobactin (32.3%), allS (15.6%), kfu (15.6%). Of all the Klebsiella pneumoniae strains, 33 (34.4%) exhibited ESBLs phenotype, 16 (16.7%) were carbapenemase-producing, and 20 (20.8%) with ESBLs phenotype tested were resistant to all four drugs. The correlation between ESBLs-producing strains and biofilm formation was significantly increased compared to strains without ESBLs phenotype (P=0.035).

Conclusion

Compared to hypervirulent Klebsiella pneumoniae (hvKP), classical Klebsiella pneumoniae (cKP) has a tendency to acquire antibiotic resistance. Our study showed that genes encoding rmpA, K1 or K2, and kfu were highly associated with hvKP.

Keeping alert to the hypervirulent K1, K2, K3, K5, K54 and K57 strains of Klebsiella pneumoniae within dairy production process

Klebsiella pneumoniae (Kp) is now recognized as an urgent threat to public health since the emergence of multidrug-resistant and hypervirulent isolates. We identified a hypervirulent K2 isolate from the milk samples possibly associated with an infection incident in children, which raised the alarm to the zoonotic potential of bovine mastitis Kp as a foodborne pathogen. Subsequently, numerous K1, K2, K3, K5, K54 and K57 strains were identified from mastitis milk samples, and showed high pathogenicity in infected mouse. Further analysis based on complete genomes found that these isolates showed closely evolutionary relationships with the human hypervirulent strains in diverse phylogenetic lineages, suggesting their potential risk to public health.

Analysis of Whole-Genome Sequences of Pathogenic Gram-Positive and Gram-Negative Isolates from the Same Hospital Environment to Investigate Common Evolutionary Trends Associated with Horizontal Gene Exchange, Mutations and DNA Methylation Patterning

Hospital-acquired infections are a generally recognized problem for healthcare professionals. Clinical variants of Gram-negative and Gram-positive pathogens are characterized with enhanced antibiotic resistance and virulence due to mutations and the horizontal acquisition of respective genetic determinants. In this study, two Escherichia coli, two Klebsiella pneumoniae, three Pseudomonas aeruginosa, two Staphylococcus aureus, one Staphylococcus epidermidis and one Streptococcus pneumoniae showing broad spectra of antibiotic resistance were isolated from patients suffering from nosocomial infections in a local hospital in Almaty, Kazakhstan. The aim of the study was to compare general and species-specific pathways of the development of virulence and antibiotic resistance through opportunistic pathogens causing hospital-acquired infections. The whole-genome PacBio sequencing of the isolates allowed for the genotyping and identification of antibiotic resistance and virulence genetic determinants located in the chromosomes, plasmids and genomic islands. It was concluded that long-read sequencing is a useful tool for monitoring the epidemiological situation in hospitals. Marker antibiotic resistance mutations common for different microorganisms were identified, which were acquired due to antibiotic-selective pressure in the same clinical environment. The genotyping and identification of strain-specific DNA methylation motifs were found to be promising in estimating the risks associated with hospital infection outbreaks and monitoring the distribution and evolution of nosocomial pathogens.

Large-scale genomic analysis of global Klebsiella pneumoniae plasmids reveals multiple simultaneous clusters of carbapenem-resistant hypervirulent strains

BACKGROUND

Klebsiella pneumoniae (Kp) Gram-negative bacteria cause nosocomial infections and rapidly acquire antimicrobial resistance (AMR), which makes it a global threat to human health. It also has a comparatively rare hypervirulent phenotype that can lead to severe disease in otherwise healthy individuals. Unlike classic Kp, canonical hypervirulent strains usually have limited AMR. However, after initial case reports in 2015, carbapenem-resistant hypervirulent Kp has increased in prevalence, including in China, but there is limited understanding of its burden  in other geographical regions.

METHODS

Here, we examined the largest collection of publicly available sequenced Kp isolates (n=13,178), containing 1603 different sequence types (e.g. ST11 15.0%, ST258 9.5%), and 2174 (16.5%) hypervirulent strains. We analysed the plasmid replicons and carbapenemase and siderophore encoding genes to understand the movement of hypervirulence and AMR genes located on plasmids, and their convergence in carbapenem-resistant hypervirulent Kp.

RESULTS

We identified and analysed 3034 unique plasmid replicons to inform the epidemiology and transmission dynamics of carbapenem-resistant hypervirulent Kp (n=1028, 7.8%). We found several outbreaks globally, including one involving ST11 strains in China and another of ST231 in Asia centred on India, Thailand, and Pakistan. There was evidence of global flow of Kp, including across multiple continents. In most cases, clusters of Kp isolates are the result of hypervirulence genes entering classic strains, instead of carbapenem resistance genes entering canonical hypervirulent ones.

CONCLUSIONS

Our analysis demonstrates the importance of plasmid analysis in the monitoring of carbapenem-resistant and hypervirulent strains of Kp. With the growing adoption of omics-based technologies for clinical and surveillance applications, including in geographical regions with gaps in data and knowledge (e.g. sub-Saharan Africa), the identification of the spread of AMR will inform infection control globally.