Hypervirulent Klebsiella Pneumoniae Research Articles

A Unique Case of Hypervirulent Klebsiella Pneumoniae Invasive Syndrome with Endogenous Endophthalmitis and Left Renal Vein Thrombosis without Liver Abscess.

This case report presents a rare instance of hypervirulent Klebsiella pneumoniae invasive syndrome (KPIS) without hepatic involvement. It highlights an atypical presentation as this syndrome is characterized by liver abscesses. A 54-year-old female of South Asian descent presented to the emergency department with abdominal pain, fever, chills, nausea, and vomiting. Lab investigations showed hyperglycaemia, leukocytosis, and elevated procalcitonin. Imaging revealed bilateral acute pyelonephritis with early abscess formation in the left kidney, bilateral pleural effusions, diffuse multi-lobar consolidations, minimal ascites, and left renal vein thrombosis. The patient was treated as a case of septic shock secondary to hypervirulent K. pneumoniae with complications evolving into acute pyelonephritis and endogenous endophthalmitis. K. pneumoniae, known for its polysaccharide capsule, can lead to severe complications in immunocompromised patients, such as endogenous endophthalmitis, liver abscess, and pyelonephritis. Endophthalmitis, a critical ocular emergency, can result in permanent vision loss. The patient's ocular outcomes remain uncertain due to a lack of follow-up, but prompt interdisciplinary intervention led to the resolution of other comorbidities. This case highlights the importance of considering hypervirulent K. pneumoniae as a cause of severe infection without liver abscess. It also underscores the importance of immediate multidisciplinary management to address the systemic complications associated with this infection and the importance of connecting different symptoms to one aetiology. Klebsiella pneumoniae invasive syndrome (KPIS) should be considered in patients with positive Klebsiella pneumoniae infection affecting more than one organ system.KPIS may present atypically, such as in the absence of liver abscesses and with the presence of thrombosis.Hypervirulent and hypermucoviscous strains of Klebsiella pneumoniae should be considered in cases of KPIS.

RNA interactome of hypervirulent Klebsiella pneumoniae reveals a small RNA inhibitor of capsular mucoviscosity and virulence

Hypervirulent Klebsiella pneumoniae (HvKP) is an emerging bacterial pathogen causing invasive infection in immune-competent humans. The hypervirulence is strongly linked to the overproduction of hypermucoviscous capsule, but the underlying regulatory mechanisms of hypermucoviscosity (HMV) have been elusive, especially at the post-transcriptional level mediated by small noncoding RNAs (sRNAs). Using a recently developed RNA interactome profiling approach iRIL-seq, we interrogate the Hfq-associated sRNA regulatory network and establish an intracellular RNA-RNA interactome in HvKP. Our data reveal numerous interactions between sRNAs and HMV-related mRNAs, and identify a plethora of sRNAs that repress or promote HMV. One of the strongest HMV repressors is ArcZ, which is activated by the catabolite regulator CRP and targets many HMV-related genes including mlaA and fbp. We discover that MlaA and its function in phospholipid transport is crucial for capsule retention and HMV, inactivation of which abolishes Klebsiella virulence in mice. ArcZ overexpression drastically reduces bacterial burden in mice and reduces HMV in multiple hypervirulent and carbapenem-resistant clinical isolates, indicating ArcZ is a potent RNA inhibitor of bacterial pneumonia with therapeutic potential. Our work unravels a novel CRP-ArcZ-MlaA regulatory circuit of HMV and provides mechanistic insights into the posttranscriptional virulence control in a superbug of global concern.

Characteristics of multidrug-resistant hypervirulent Klebsiella pneumoniae strains ST29 and K212 harbouring tmexC2-tmexD2-toprJ2

ObjectivesThis study aimed to characterize a tigecycline-resistant hypervirulent Klebsiella pneumoniae (HvKP) strain, identified as KLZT, which carries the tigecycline resistance gene cluster tmexC2-tmexD2-toprJ2 belonging to ST29 and serotype K212. MethodsAntimicrobial susceptibility and virulence phenotypes were assessed, followed by whole-genome sequencing (WGS) using PacBio II and MiSeq sequencers. Genome annotation was carried out using the RAST server and bioinformatics analysis revealed the genetic characteristics of this strain. ResultsAntimicrobial and virulence phenotype testing indicated that K. pneumoniae strain KLZT could be considered as a multidrug-resistant HvKP. WGS analysis showed that KLZT has a single 5,536,506-bp chromosome containing three plasmids 290,963 bp (pKLZT-1), 199,302 bp (pKLZT-2), and 4820 bp (pKLZT-3) in size, and also includes the ST29 and K212 serotypes. Four (blaSHV-187, oqxA, oqxB, and fosA6) and six resistance genes (tmexC2-tmxeD2-toprJ2, blaOXA-1, aac(6′)-Ib-cr, catB3, arr-3, and blaLEN27) were identified from chromosomal and plasmid pKLZT-1, respectively. Gene-based analysis of the resistance genes of plasmid pKLZT-1 showed that the tigecycline resistance gene cluster-carrying region was flanked by umuC and umuD (umuD-hps-IS5-tmexC2-tmexD2-toprJ2-umuC), as well as other resistance genes and virulence factors (ureB, ureC, and ureG), which were carried by IS5075-Tn3-intI1 -aac(6′)-Ib-cr-blaOXA-1-catB3-arr-3-blaLEN27-Tn3-ISkpn26-ureBCG-IS5075. ConclusionsWGS has revealed that a multidrug-resistant strain, HvKP KLZT, belonging to ST29 with capsular serotype K212, contains a multidrug-resistance plasmid.

Antibiotic resistance and epidemiological characteristics of polymyxin-resistant Klebsiella pneumoniae.

The emergence of polymyxin-resistant Klebsiella pneumoniae (KPN) in clinical settings necessitates an analysis of its antibiotic resistance characteristics, epidemiological features, and risk factors for its development. This study aims to provide insights for the prevention and control of polymyxin-resistant KPN infections. Thirty clinical isolates of polymyxin-resistant KPN were collected from the Third Xiangya Hospital of Central South University. Their antibiotic resistance profiles were analyzed. The presence of carbapenemase KPC, OXA-48, VIM, IMP, and NDM was detected using colloidal gold immunochromatography. Hypervirulent KPN was initially screened using the string test. Biofilm formation capacity was assessed using crystal violet staining. Combination drug susceptibility tests (polymyxin B with meropenem, tigecycline, cefoperazone/sulbactam) were conducted using the checkerboard method. Polymyxin-related resistance genes were detected by PCR. Multi-locus sequence typing (MLST) was performed for genotyping and phylogenetic tree construction. The study also involved collecting data from carbapenem-resistant (CR)-KPN polymyxin-resistant strains (23 strains, experimental group) and CR-KPN polymyxin-sensitive strains (57 strains, control group) to analyze potential risk factors for polymyxin-resistant KPN infection through univariate analysis and multivariate Logistic regression. The induction of resistance by continuous exposure to polymyxin B and colistin E was also tested. Among the 30 polymyxin-resistant KPN isolates, 28 were CR-KPN, all producing KPC enzyme. Four isolates were positive in the string test. Most isolates showed strong biofilm formation capabilities. Combination therapy showed additive or synergistic effects. All isolates carried the pmrA and phoP genes, while no mcr-1 or mcr-2 genes were detected. MLST results indicated that ST11 was the predominant type. The phylogenetic tree suggested that polymyxin-resistant KPN had not caused a hospital outbreak in the institution. The use of two or more different classes of antibiotics and the use of polymyxin were identified as independent risk factors for the development of polymyxin-resistant strains. Continuous use of polymyxin induced drug resistance. Polymyxin-resistant KPN is resistant to nearly all commonly used antibiotics, making polymyxin-based combination therapy a viable option. No plasmid-mediated polymyxin-resistant KPN has been isolated in the hospital. Polymyxin can induce resistance in KPN, highlighting the need for rational antibiotic use in clinical settings to delay the emergence of resistance.

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.

Distribution, characterization and antibiotic resistance of hypervirulent Klebsiella Pneumoniae (hvKp) strains versus classical strains(CKp) causing healthcare associated infections in Sohag University Hospitals

Distribution, characterization and antibiotic resistance of hypervirulent Klebsiella Pneumoniae (hvKp) strains versus classical strains(CKp) causing healthcare associated infections in Sohag University Hospitals

Comparison of clinical and microbiological characteristics of community-acquired hypervirulent Klebsiella pneumoniae liver abscess in diabetic and non-diabetic patients.

Invasive infection caused by hypervirulent Klebsiella pneumoniae (HvKP) has been reported worldwide. Most of the patients are community population, related to diabetes mellitus (DM), chronic liver disease and other basic diseases, which prone to systemic migratory infection. In this study, we collected 377 patients with community acquired Klebsiella pneumoniae liver abscess in our hospital from January 2013 to December 2018, 65.8% of whom were male, and 49.6% had DM. Patients with DM are prone to eye and central nervous system (CNS) infection, which need continuous local abscess drainage during treatment. Among them, patients with poor blood glucose control have a higher rate of blood stream infections (BSI). 219 strains of HvKP were obtained, with K1/K2 Serotype accounted for 81.7%. The incidence of BSI in K2 patients was higher than that in K1 patients. The PCR results indicate that the carrying rate of virulence genes (rmpA、areo、kfu、allS、iroN、magA、uge、wcaG) in K1/K2 type strains is significantly higher than that in non K1/K2 type strains. ST23 and ST65 are the most common multilocus sequence typing (MLST), which belong to K1 and K2 Serotype respectively. All of HvKP strains showed high sensitivity to commonly used clinical antibiotics other than ampicillin, with 54.3% of the strains exhibiting high viscosity characteristics. Meanwhile, 35 classic Klebsiella pneumoniae (cKP) strains were collected, and their serum typing is mainly non K1/K2. The carrying rate of virulence genes and viscosity degree in HvKP are significantly higher than those in cKP. Primary liver abscess caused by HvKP is prone to multiple tissue and organ infections, but it shows higher sensitivity to most commonly used antibiotics in clinical practice except for ampicillin. After effective treatment, the overall prognosis of patients is better. This study analyzes the pathogenic characteristics of HvKP and elaborates on the clinical characteristics of patients, which can provide reference for clinical and scientific research work.

Transcriptomic and phenotype analysis revealed the role of rpoS in stress resistance and virulence of a novel ST3355 ESBL-producing hypervirulent Klebsiella pneumoniae isolate.

An extended-spectrum beta-lactamase (ESBL)-hypervirulent Klebsiella pneumoniae (HvKP) strain HKE9 was isolated from the blood in an outpatient. The effect of the global regulatory factor RpoS on antimicrobial resistance, pathogenicity, and environmental adaptability was elucidated. HKE9 is a novel ST3355 (K20/O2a) hypervirulent strain with a positive string test and resistant to cephems except cefotetan. It has a genome size of 5.6M, including two plasmids. CTX-M-15 was found in plasmid 2, and only ompk37 was found in the chromosome. HKE9 could produce bacterial siderophores, and genes of enterobactin, yersiniabactin, aerobactin, and salmochelin have been retrieved in the genome. As a global regulatory factor, knockout of rpoS did not change antimicrobial resistance or hemolytic phenotype while increasing the virulence to Galleria mellonella larvae and showing higher viscosity. Moreover, rpoS knockout can increase bacterial competitiveness and cell adhesion ability. Interestingly, HKE9-M-rpoS decreased resistance to acidic pH, high osmotic pressure, heat shock, and ultraviolet and became sensitive to disinfectants (H2O2, alcohol, and sodium hypochlorite). Although there were 13 Type 6 secretion system (T6SS) core genes divided into two segments with tle1 between segments in the chromosome, transcriptomic analysis showed that rpoS negatively regulated T4SS located on plasmid 2, type 1, and type 3 fimbriae and positively regulate genes responsible for acidic response, hyperosmotic pressure, heat shock, oxidative stress, alcohol and hypochlorous acid metabolism, and quorum sensing. Here, this novel ST3355 ESBL-HvKP strain HKE9 may spread via various clonal types. The important regulation effect of rpoS is the enhanced tolerance and resistance to environmental stress and disinfectants, which may be at the cost of reducing virulence and regulated by T4SS.

Analysis of biofilm-forming ability and drug resistance for Hypervirulent Klebsiella pneumoniae

Investigate the biofilm-forming ability and drug resistance of Hypervirulent Klebsiella pneumoniae (HvKP) to provide scientific basis for the treatment of HvKP-infection. A total of 96 Klebsiella pneumoniae strains isolated from clinical infection specimens in Changsha Central Hospital from January to December in 2021 were retrospectively collected, and the clinical data of patients were collected. The string test preliminarily distinguished between HvKP and classic Klebsiella pneumoniae (CKP). The biofilm-forming ability of clinical strains of Klebsiella pneumoniae (KP) was determined by microplate method. The Vitek 2 Compact automatic microbial identification/drug sensitivity analysis system was used for bacterial identification and drug sensitivity test. The clinical data of patients, biofilm forming ability and drug resistance in the HvKP group and those in the CKP group were compared and analyzed. The results showed that a total of 20 strains of HvKP were isolated from 96 non-repetitive KP, and the detection rate was 20.8%. HvKP mainly come from respiratory specimens, up to 75.0%.The prevalence of hepatobiliary diseases and the infection rate of multiple sites in patients with HvKP infection were higher than those in patients with CKP infection, and the difference was statistically significant(χ2=5.184,7.488;P=0.023,0.006).There was no significant difference between the two groups in terms of gender, age, ICU admission, hypertension, diabetes, coronary heart disease, lung disease, urinary system disease, central nervous system disease and laboratory test indexes (all P>0.05).17 (85.0%) strains of HvKP can form biofilm, including 2 strains with weak biofilm-forming ability (10.0%), 10 strains with moderate biofilm-forming ability (50.0%) and 5 strains with strong biofilm-forming ability (25.0%). Among the 76 CKP, 71 (93.4%) could form biofilm, including 13 (17.1%) with weak biofilm-forming ability, 30(39.5%) with moderate biofilm-forming ability and 28 (36.8%) with strong biofilm-forming ability. There was no significant difference in biofilm-forming ability between HvKP and CKP (χ2=1.470,P=0.225).The overall resistance rate of HvKP was not high, but a multi-resistant HvKP resistant to carbapenems was found. The detection rate of multi-resistant HvKP (5.0%) was lower than that of multi-resistant CKP (28.9%), and the difference was statistically significant (χ2=4.984, P=0.026).The resistance rate of HvKP to piperacillin/tazobactam, aztreonam, ciprofloxacin, levofloxacin, ceftazidime, cefepime, tobramycin, minocycline, doxycycline, and compound sulfamethoxazole was lower than that of CKP, and the difference was statistically significant (all P<0.05). In conclusion, most of hypervirulent Klebsiella pneumoniae can form biofilm in this study, but the difference of biofilm-forming ability is not obvious compared with classic Klebsiella pneumoniae. HvKP maintains high sensitivity to commonly used antibacterial drugs, but the drug resistance monitoring of the bacteria cannot be ignored.

Violet phosphorene nanosheets coupled with CRISPR/Cas12a in a biosensor with a low background signal for onsite detection of tigecycline-resistant hypervirulent Klebsiella pneumoniae

CRISPR/Cas12a-based detection has been widely used for DNA targets, but always suffers from a relatively high background fluorescent signal, which potentially gives false positive results, and limits the accuracy and specificity of detection. To address this problem, violet phosphorene nanosheets (VPNSs) with excellent DNA adsorption and light absorption capacities were synthesized by liquid exfoliation from bulk violet phosphorus. The introduction of VPNSs into CRISPR/Cas12a-based detection decreased the relatively high background fluorescent signal by 32.7 %, and resulted in a background with the relative fluorescence unit of 2590.5 that was no longer visible via a visual readout, demonstrating that VPNSs are efficient fluorescence quenchers. By combining the detection with a smartphone-based fluorescence imaging system (FIS), a biosensor was developed for simultaneous detection of virulence genes iucA, iroB, peg-344, rmpA and rmpA2, and resistance gene tet(A) carried by tigecycline-resistant hypervirulent Klebsiella pneumoniae (HvKP). Upon optimization, the VPNSs-CRISPR/Cas12a-FIS biosensor detected 1 cfu of tigecycline-resistant HvKP in 60 min with a low background signal. The whole process was performed with portable devices including a block heater and an FIS, and the signal could be observed with either a smartphone or the naked eye. The biosensor provides new insights for exploration of low background, multiple target, and onsite analytical methods based on CRISPR/Cas12a.

Comparative Studies on Clinical Isolates of Hypervirulent and Classical Klebsiella pneumoniae

Hypervirulent Klebsiella pneumonia (hvKP), typically linked with the hypermucoviscous phenotype, has evolved as a clinically significant pathogen responsible for catastrophic disseminated infections including osteomyelitis, pyogenic liver abscesses (PLA), and endophthalmitis in an otherwise younger and healthier population. Methods: Mansoura University Hospitals, Egypt have utilised VITEK® 2 to identify clinical K. pneumoniae isolates. The Kirby Bauer's disc diffusion method was employed to asses sensitivity to antimicrobial. String test for detecting microvasculitis, Serotyping, and Bio-typing are among the phenotypic methods employed. Polymerase chain reaction (PCR) was performed to amplify capsular serotype-specific genes (K1 and K2) as well as virulence-associated genes (rmpA and magA). Results: Over two-years, 100 hypermucoviscous phenotype K. pneumoniae and 100 classical K. pneumoniae strains were isolated and screened by string test. Hypermucoviscosity Serotyping revealed that 76 isolates had K1-type capsules, 19 had K2-type capsules, and 5 were non-K1/K2 isolates. Among the positive hypermucoviscusisolates, the prevalence of rmpA gene was 79 %, and magA gene was 40 %. Although, the prevalence of these two genes in classical Klebsiella pneumoniae (cKP) isolates was very low 11% and 7%, respectively. Aside from that, the occurrence of K capsular genes in hvKP isolates were; K1 gene 66% and K2 gene 63%.However, the occurrence of these genes in cKP isolates were limited. Conclusion: In our geographical area, hypervirulent Klebsiella pneumoniae hvKP isolates were infrequent among K. pneumoniae isolates (El-Mansoura, Egypt). This study summarized and concentrated on the epidemiology, hypervirulence-associated variables, and antibiotic resistance mechanisms of hvKP strains. This was done to let the microbiologist or clinician know that the infecting strain could be hvKP, which is more dangerous than cKP. As a result, detecting these hypervirulent strains, which harbor resistance variants, should be a top goal priority.

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

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. 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. 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. 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.

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.

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

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. 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. 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. 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.

A Response to Article "Distribution of Mcr-1 Harboring Hypervirulent Klebsiella pneumoniae in Clinical Specimens and Lytic Activity of Bacteriophage KpnM Against Isolates" [Response to Letter

Response to Letter in regards to A Response to Article “Distribution of Mcr-1 Harboring Hypervirulent Klebsiella Pneumoniae in Clinical Specimens and Lytic Activity of Bacteriophage KpnM Against Isolates” [Letter]

A Response to Article "Distribution of Mcr-1 Harboring Hypervirulent Klebsiella Pneumoniae in Clinical Specimens and Lytic Activity of Bacteriophage KpnM Against Isolates" [Letter

A Response to Article "Distribution of Mcr-1 Harboring Hypervirulent Klebsiella Pneumoniae in Clinical Specimens and Lytic Activity of Bacteriophage KpnM Against Isolates" [Letter

Identification of hypervirulent Klebsiella pneumoniae carrying terW gene by MacConkey-potassium tellurite medium in the general population.

ObjectivesTo establish a MacConkey-potassium tellurium medium-based method for selectively culturing terW gene-positive Klebsiella pneumoniae (KP), to evaluate its performance and apply it to identifying particular clonal hypervirulent KP (hvKP) strains in epidemiological surveillance.MethodsThe virulence genes, rmpA, iutA, and terW, were detected by PCR. The minimum inhibitory concentration of potassium tellurite of hvKP (rmpA+/ iutA+) and classical KP (rmpA− and iutA−) was determined using the agar dilution method. The MacConkey medium containing 4 μg/ml potassium tellurite was prepared and the performance in detecting terW+ KP was evaluated, including an agreement with PCR and positive/negative predictive value. Fecal samples from healthy volunteers in Fujian were collected and cultured in the medium, then positive strains were identified using MALDI-TOF MS, antimicrobial susceptibility was tested by Kirby-Bauer assays, and virulence genes and capsular serotype genes were tested by PCR.ResultsIn KP isolated from clinical specimens (N = 198), the positive rate of terW was 37.9%, and the detection rate of terW in hvKP was significantly higher than that in classical KP (70.6% vs 13.3%). The potassium tellurite resistance levels of terW+ (N = 75) and terW− (N = 55) KP were 8–128 μg/ml and <1–8 μg/ml, respectively, with significant differences. KP was selectively cultured on a MacConkey medium with 4 μg/ml potassium tellurite, and its agreement with PCR was good (Kappa=0.936), and the positive and negative percent agreement and positive and negative predictive values were 100% (75/75), 92.7% (51/55), 94.9% (75/79), and 100% (51/51), respectively. The prevalence of tellurite-resistant KP was 16.7% (86/516) in fecal samples from healthy volunteers, among which the positive rate of terW was 100% (86/86). The antimicrobial resistance characteristics of terW+ KP showed no difference between healthy volunteers and inpatients. The most common capsular serotypes associated with high virulence were K1, K2, and K57.ConclusionsThe MacConkey medium containing 4 μg/ml potassium tellurite could easily select and culture terW+ KP in fecal samples with high sensitivity and specificity, which is a practical method for the epidemic surveillance of hvKP in the general population.

Molecular Epidemiology of Antimicrobial Resistance, Virulence and Capsular Serotypes of Carbapenemase-Carrying Klebsiella pneumoniae in China.

This study analyzed genomic data of 4643 strains of carbapenemase-carrying Klebsiella pneumoniae (KPN) in China by using the Kleborate software package. The data showed rich diversity in carbapenemase-carrying KPN genomes, which contain not only 152 sequence types but also 90 capsular serotypes. In 2013, the transfer of carbapenemase to hypervirulent Klebsiella pneumoniae (HvKP) of KL1 and KL2 occurred, and since 2014, the propagation of carbapenemase into mammals, poultry, and insects has been detected. The ST11 capsular serotype had a reversal of the prevalence of KL47 and KL64 in 2016, with KL64 replacing KL47 as the dominant serotype. Colibactin is a very suitable indicator to differentiate KL1-type HvKP and classic Klebsiella pneumoniae. The most prevalent yersiniabactin of KL1 is ybt1 ICEKp10, and that of ST11 carbapenem-resistant KPN(ST11-CRKP) is ybt9 ICEKp3. The virulence genes of KL1 carbapenem-resistant hypervirulent KPN (KL1-CRHvKP), as well as ST65- and ST86-type KL2-CRHvKP, were not lost after carbapenemase was obtained.

Occurrence of Hypervirulent Klebsiella pneumoniae in Clinical Settings and Lytic Potential of Bacteriophages Against the Isolates

Background: Antibiotic resistance is a major health hazard around the globe. Hypervirulent Klebsiella Pneumoniae (hvKp) is associated with hospital-acquired and community-acquired infections. Since there is a lack of new antibiotics against multidrug-resistant (MDR) pathogens, phage therapy might provide an alternative approach to confer antibiotic resistance. Objectives: This study aimed to estimate the occurrence of hvKp and characterize the bacteriophage against the hvKp prevalence in clinical settings, which might be used as an alternative to antibiotics. Methods: Different clinical samples (n = 50) were collected to isolate K. pneumoniae, and the assessment of multidrug resistance was carried out based on the Clinical and Laboratory Standards Institute guidelines (2020). The bacteriophage was isolated from hospital waste, and the double agar overlay method was used for phage purification and propagation. Spot test and one-step curve were performed to determine host-phage interactions. For the evaluation of phage stability in environmental conditions, the phage was incubated at various ranges of temperature, pH, and chloroform. Results: Out of the collected samples, 22 (44%) isolates were confirmed as K. pneumoniae. Among confirmed K. pneumoniae isolates, a total of 11 (50%) isolates were detected as hvKp. Moreover, 14 (64%) isolates were detected as MDR, out of which 5 (35%) isolates were among hvKp phenotypes. Maximum resistance was observed against ampicillin (86%) followed by ceftriaxone (81%) which was the highest among cephalosporins. The isolated bacteriophage showed a broad host range, short latent period, and stability. Overall, 16 isolates (85%) of K. pneumoniae were susceptible to phage infection, among which 12 isolates were MDR (75%); however, all 5 (100%) hvKp isolates were susceptible to phage infection. One-step growth analysis revealed a burst size of 190 phages/host bacterial cells with a short latent period of 24 minutes. Conclusions: Altogether, the significant prevalence of hvKp was estimated in clinical settings, and the isolated bacteriophage showed significant lytic activity as it killed all the hvKp strains. Phage therapy might be exploited and used as a potential alternative therapeutic approach against infections caused by this resistant pathogen.

Preliminary Investigation of Iron Acquisition in Hypervirulent Klebsiella pneumoniae Mediated by Outer Membrane Vesicles.

ObjectiveTo investigate the role of outer membrane vesicles (OMVs) and related proteins in iron acquisition of hypervirulent Klebsiella pneumoniae (HVKP) and classic Klebsiella pneumoniae (cKP).MethodsThe OMVs of HVKP and cKP under iron-deficient and iron-sufficient media were extracted and purified by ultracentrifugation. Transmission electron microscopy (TEM) was used to identify OMVs. The quantitative proteomics were performed based on mass spectrometry.ResultsFour OMVs samples secreted by HVKP and cKP under iron-deficient and iron-sufficient environment were isolated and collected (HVKP OMVs under iron-deficient environment (A1), HVKP OMVs under iron-sufficient environment (A2), cKP OMVs under iron-deficient environment (B1), cKP OMVs under iron-sufficient environment (B2)). The amount of OMVs released by HVKP in iron-deficient medium was significantly larger than that in iron-sufficient medium (P < 0.05). HVKP secreted more OMVs than cKP in iron-deficient medium (P < 0.05). A total of 1074 kinds of proteins were identified in four samples. A comparison between the iron-deficient vs iron-sufficient environment showed that 61 proteins in HVKP OMVs were identified with a significant change in abundance under iron-deficient environment. Among them, 17 proteins were related to iron acquisition and transportation systems. While in cKP OMVs, 62 proteins significantly changed under iron-deficient environment in which 5 proteins were related to iron acquisition and transportation systems. Upon comparison of the HVKP vs cKP OMVs under iron deficiency, 81 proteins were detected with a significant change in which 8 proteins were related to iron acquisition and transportation systems.ConclusionAbove all, the results of this study suggest a potential role for OMVs in iron acquisition of HVKP and provide evidence of potential connections between OMVs and strong iron-acquisition ability of HVKP during iron limitation.