hvKP Isolates Research Articles

Incidence, Risk Factors and Clinical Outcomes of Patients with Hypermucoviscoid Klebsiella in a Tertiary Intensive Care Unit.

Background and Objectives:Hypermucoviscoid Klebsiella(hvKP), a dreaded variant of Klebsiella, so far, fewer cases were reported from the community. This study was designed to evaluate the incidence of hvKP isolates, risk factors for hvKP infections, antibiotic sensitivity pattern and clinical outcome including morbidity and mortality.Patients and Setting:Patients who have got admitted under medical intensive care unit (MICU) and had positive culture of Klebsiella infections.Materials and Methods:This study was conducted at department of MICU at a tertiary care hospital between January 2018 and December 2018. A standardized proforma was prepared and data was collected, which includes basic demographics of the patients, co-morbidities, clinical details and mortality. This study was approved by the Institutional Review Board and Ethics Committee.Results:A total of 165 patients (males, 123; 74.5%) had Klebsiella pneumoniae infection during the study period, out of whom 32 was hvKP (19.4%). The mean age was 53.1 ± 16.8 years. Among the 32 hvKP patients, 22 (68.8%) were hospital acquired infection (HAI) and 10 were (31.2%) community acquired infection. The overall mortality rate of hvKP infection was 56.2% (18/32). The incidence of mortality rate was similar in patients having pan-drug sensitive and in patients with extreme drug-resistance (61.9% vs. 66.7%; P = 0.831). HAI is significantly associated with multi drug resistance of hvKP (odds ratio [OR], 7.917; P < 0.05) and diabetes is associated with increased risk of hvKP related mortality (OR, 5.250; P = 0.054).Conclusions:Our study results showed, increased incidence of HAI with hvKP predominantly associated with pneumonia and increase in trend of drug resistance with two cases being pan resistant. More number of studies are required to evaluate the existing antibiotics strategy and steps to curb the spread of this dreaded infection.

Characteristics of Klebsiella pneumoniae Isolates from Stool Samples of Patients with Liver Abscess Caused by Hypervirulent K. pneumoniae.

BackgroundHypervirulent Klebsiella pneumoniae (hvKP) has been the most significant pathogen for liver abscesses in East Asia including the Republic of Korea (ROK). Although gastrointestinal colonization of K. pneumoniae may cross the intestinal barrier to invade the liver, characteristics of gastrointestinal carriage K. pneumoniae of hvKP liver abscess patients in the ROK are not well known.MethodsCharacteristics of K. pneumoniae isolated from stool samples and liver aspirate samples of patients with hvKP liver abscess at a tertiary care hospital in the ROK between 2017 and 2018 were evaluated.ResultsOut of 37 patients with hvKP liver abscess, 11 patients were noted to have K. pneumoniae isolated from stool samples and were enrolled for analysis. The median age was 71 years. For hvKP isolates from the liver aspirate samples, the most common serotype was K1 (72.7%) followed by K2 (27.3%). For K. pneumoniae isolates from the stool sample, the majority was non-K1/K2 serotype (72.7%). Among non-K1/K2 serotype isolates, high variability of sequence type (ST; ST15, ST307, ST37, ST273, ST2622, and ST42) with high rate of presence of extended-spectrum beta-lactamase (100.0%) was noted. The concordance rate of the K. pneumoniae isolates between the liver aspirate samples and the stool samples from the primary hvKP liver abscess was low (27.3%).ConclusionThis study suggests that significant heterogeneity of K. pneumoniae colonizing intestinal tract of the hvKP liver abscess patients. Further studies involving a larger number of hvKP liver abscess patients with continuing surveillance are needed to define the changing epidemiology and the role of gastrointestinal K. pneumoniae in the hvKP liver abscess patients in the ROK.

Protective Role of Kupffer Cells and Macrophages in Klebsiella pneumoniae-Induced Liver Abscess Disease.

Klebsiella pneumoniae-induced liver abscess (KLA) is emerging as a leading cause of pyogenic liver abscess worldwide. In recent years, the emergence of hypervirulent K. pneumoniae (hvKp) has been strongly associated with KLA. Unlike classical K. pneumoniae, which generally infects the immunocompromised population, hvKp can cause serious and invasive infections in young and healthy individuals. hvKp isolates are often associated with the K1/K2 capsular types and possess hypermucoviscous capsules. KLA is believed to be caused by K. pneumoniae colonizing the gastrointestinal tract of the host and translocating across the intestinal barrier via the hepatic portal vein into the liver to cause liver abscess. We optimized the isolation of the liver-resident macrophages called Kupffer cells in mice and examined their importance in controlling bacterial loads during hvKp infection in healthy mice. Our study reveals the high capability of Kupffer cells to kill hvKp in vitro despite the presence of the bacterial hypermucoviscous capsule, in contrast to other macrophages, which were unable to phagocytose the bacteria efficiently. Depletion of Kupffer cells and macrophages with liposome-encapsulated clodronate (liposomal clodronate) in both an intraperitoneal and an oral mouse infection model resulted in increased bacterial loads in the livers, spleens, and lungs and increased mortality of the infected mice. Thus, Kupffer cells and macrophages are critical for the control of hvKp infection.

Prevalence of Community-Acquired, Hypervirulent Klebsiella pneumoniae Isolates in Wenzhou, China.

Hypervirulent Klebsiella pneumoniae (hvKP) can cause severe invasive infections in healthy and immunocompromised individuals. It is an important clinical pathogen, with the recent identification of highly invasive community-acquired K. pneumoniae that produce purulent liver abscess. Herein, the frequency, clinical characteristics, and molecular epidemiology of K. pneumoniae isolates obtained from January to October 2016 in Wenzhou, China, were examined. In the present study, 33 isolates (68.8%, 33/48) had a positive string test and were identified as hvKP. Both age and sex were associated with a positive string test (p < 0.05). Univariate analysis revealed that liver abscess (odds ratio = 10.154) was a significant risk factor for hvKP. Among the hvKP isolates, K1 was the most common capsular serotype, followed by K2 (p < 0.05). The prevalence of K1 and K2 was significantly higher in hvKP than non-hvKP isolates. The rates of virulence-associated genes, rmpA, iroB, fib, and hib, were significantly higher for hvKP than for non-hvKP (p < 0.05). In this study, kfuB, ybtA, and wcaG were associated with K1 isolates. ST23 was the predominant hvKP type, which belonged to serotype K1. Pulsed-field gel electrophoresis showed that two clusters had >75% similarity and each accounted for >3 isolates. The homology of the 48 clinical isolates was diverse. In conclusion, hvKP isolates had a high frequency of virulence factors and a wide variety of homologs. These results suggest that, because of the toxicity associated with K. pneumoniae, increased clinical understanding of the disease is important to prevent larger, severe outbreaks.

MoS2-Modified Curcumin Nanostructures: The Novel Theranostic Hybrid Having Potent Antibacterial and Antibiofilm Activities against Multidrug-Resistant Hypervirulent Klebsiella pneumoniae.

The recent emergence of hypervirulent clinical variants of Klebsiella pneumoniae (hvKP) causing community-acquired, invasive, metastatic, life-threatening infections of lungs, pleura, prostate, bones, joints, kidneys, spleen, muscles, soft-tissues, skin, eyes, central nervous system (CNS) including extrahepatic abscesses, and primary bacteremia even in healthy individuals has posed stern challenges before the existing treatment modalities. There is therefore an urgent need to look for specific and effective therapeutic alternatives against the said bacterial infection or recurrence. A new type of MoS2-modified curcumin nanostructure has been developed and evaluated as a potential alternative for the treatment of multidrug-resistant isolates. The curcumin quantum particles have been fabricated with MoS2 via a seed-mediated hydrothermal method, and the resulting MoS2-modified curcumin nanostructures (MQCs) have been subsequently tested for their antibacterial and antibiofilm properties against hypervirulent multidrug-resistant Klebsiella pneumoniae isolates. In the present study, we found MQCs inhibiting the bacterial growth at a minimal concentration of 0.0156 μg/mL, while complete inhibition of bacterial growth was evinced at concentration 0.125 μg/mL. Besides, we also investigated their biocompatibility both in vitro and in vivo. MQCs were found to be nontoxic to the SiHa cells at a dose as high as 1024 μg/mL on the basis of the tested adhesion, spreading of the cells, and also on the various serological, biochemical, and histological investigations of the vital organs and blood of the Charles Foster Rat. These results suggest that MQCs have potent antimicrobial activities against hvKP and other drug resistant isolates and therefore may be used as broad spectrum antibacterial and antibiofilm agents.

Hypervirulent Klebsiella pneumoniae (hypermucoviscous and aerobactin positive) infection over 6\xa0years in the elderly in China: antimicrobial resistance patterns, molecular epidemiology and risk factor

BackgroundThe definition of hypervirulent Klebsiella pneumoniae (hvKp), traditionally regarded as hypermucoviscosity, is controversial. However, data based on both phenotype (hypermucoviscous) and genetic (aerobactin) criteria are limited.MethodsA retrospective study was conducted in 175 geriatric patients between January 2008 and January 2014. The clinical and molecular data, including antimicrobial susceptibility testing, extended-spectrum-β-lactamase (ESBL) production, virulence gene, and multilocus sequence typing of the hvKp-group (hypermucoviscosity and aerobactin positive) were compared with those of classic K. pneumoniae (cKp) isolates.ResultsOf 175 Kp isolates, 45.7% were hvKp. In pathogenicity, K1, K2, magA, rmpA, and rmpA2 genes were strongly associated with hvKp (P < 0.01). In the hvKp group, invasive infections (P < 0.000), liver abscess (P = 0.008), abdominal infection (P = 0.002) and septic shock (P = 0.035) are significantly higher than cKp group. Patients with better nutritional status were frequently infected with hvKp. However, host inflammatory reaction is most severe in hvKp group. Patients with diabetes (odds ratio [OR] = 2.548) and digestive diseases (OR = 2.196) are more likely to be infected with hvKp. Importantly, the detection of hvKp isolates increased from January 2008 to January 2010, January 2010 to January 2012, and January 2010 to January 2014 (12, 30, and 48 isolates, respectively). Overall, 16.3% of hvKp isolates produced ESBLs and 20.0% were MDR-hvKp. Multivariate analysis implied that infection occurred in the ICU (OR = 5.826) and patients with indwelling stomach tubes (OR = 6.461) are independent risk factors for ESBL-hvKp infection.ConclusionsHvKp, especially ESBL-hvKp and MDR-hvKp, is emerging in the elderly. It is essential to enhance clinical awareness and management of hvKp infections.

Virulence Factors, Capsular Serotypes and Antimicrobial Resistance of Hypervirulent Klebsiella pneumoniae and Classical Klebsiella pneumoniae in Southeast Iran.

The present study was conducted to investigate the distribution of virulence factors, capsular serotypes and antibiotic resistance properties of classical Klebsiella pneumoniae (cKP) and hypermucoviscous/hypervirulent Klebsiella pneumoniae (hvKP) isolated from different clinical specimens in Kerman, south-east of Iran. A total of 146 K. pneumoniae isolates were obtained from different clinical specimens. HvKP isolates were identified using the string test. Genes of capsular serotypes K1, K2, K5, K20, K54 and K57 and virulence-associated genes, rmpA, kfu, fimH, mrkD, allS, iutA, magA, entB and ybtS were evaluated by PCR. Antimicrobial susceptibility was also determined using the disc diffusion method. Out of 146 K. pneumoniae isolates, 22 (15.1 %) were hvKP. More than half of the hvKP isolates, 13 (59.1%), belonged to non-K1, K2, K5, K20, K54, K57 serotypes. Out of 22 hvKP isolates, 3 and 3 had K1 and K2 serotypes respectively. Among all isolates, entB 140 (95.9%) and mrkD 138 (94.5%) were the most common virulence genes. RmpA, iutA and kfu were associated with hvKP isolates (P-value <0.05). However, no significant difference was found in fimH, allS, mrkD, entB and ybtS genes between hvKP and cKP strains. HvKP exhibited significantly lower resistance rates to all antimicrobial agents than cKP, except to trimethoprim-sulphamethoxazole and ampicillin (P-value <0.05). The frequency of hvKP was low, but overall, the prevalence of virulence-related genes was higher in hvKP than cKP. HvKP was not related to specific serotypes. Furthermore, hvKP isolates were more susceptible to antimicrobial agents compared to cKP isolates.

Diversity of virulence level phenotype of hypervirulent Klebsiella pneumoniae from different sequence type lineage

BackgroundHypervirulent Klebsiella pneumoniae (hvKP) is emerging around the Asian-Pacific region and it is the major cause of the community-acquired pyogenic liver abscesses. Multidrug-resistant hypervirulent Klebsiella pneumoniae (MDR-hvKP) isolates were reported in France, China and Taiwan. However, the international-ally agreed definition for hvKP and the virulence level of hvKP are not clear.ResultsIn this study, 56 hvKP isolates were collected from March 2008 to June 2012 and investigated by string test, capsule serotyping, multilocus sequence typing (MLST), virulence gene detection and serum resistance assay. Among the 56 K. pneumoniae isolates, 64.3% had the hypermucoviscosity phenotype, meanwhile, 64.3% were the K1 serotype and 19.6% were the K2 serotype. Within the K1 serotype, 94.4% were ST23, and within the K2 serotype, ST65, ST86 and ST375 accounted for the same percentage 27.3%. The serum resistance showed statistically normal distribution. According to the 50% lethal dose of Galleria. mellonella infection model, hvKP isolates were divided into high virulence level group and moderate virulence level group. The ability of each method evaluating the virulence level of hvKP was assessed using the area under the receiver operating characteristic curve.ConclusionsK1 ST23 K. pneumoniae was the most prevalent clone of the hvKP. However, K1 ST23 K. pneumoniae was the dominant clone in the moderate virulence level group. MLST was a relatively reliable evaluation method to discriminate the virulence level of hvKP in our study.

Characteristics of ventilator-associated pneumonia due to hypervirulent Klebsiella pneumoniae genotype in genetic background for the elderly in two tertiary hospitals in China

BackgroundAerobactin is a critical factor for the hypervirulent Klebsiella pneumoniae (hvKp), but data for the aerobactin-positive genotype of hvKp in elderly persons with ventilator-associated pneumonia (VAP) is limited. The purpose of this study is to understand the risk factors and characteristics of the hvKp genotype for elderly patients with VAP.MethodsA retrospective study of 73 elderly patients with Kp was conducted from November 2008 to December 2017 in two tertiary hospitals. The clinical and microbiological data, including inflammatory reaction, nutritional status, antimicrobial susceptibility testing, string test, extended-spectrum-β-lactamase (ESBL) production, virulence-associated gene (capsular serotype-specific gene and rmpA/A2,magA,aerobaction) and multilocus sequence typing, of the hvKp group defined as aerobactin positive were compared with those of classic Kp strains.ResultsOf 73 Kp isolates, 46.6% were hvKp. ST23 is highly prevalent in two hospitals but is not highly associated with hvKp in different hospitals. Additionally, ST23, ST37 and ST2906 are more likely to induce lethal VAP. Most hvKp strains are sensitive to common antibiotics, but the number of multidrug-resistant (MDR) hvKp is increasing. Importantly, 38.2% of hvKp isolates produced ESBLs. Hypermucoviscosity and virulence-associated genes (K1,magA and rmpA/A2) were highly clustered in the hvKp group (P < 0.001). Cancer (P = 0.004), digestive disease (P = 0.038) and surgery (P = 0.023) within 1 month are strongly associated with the VAP-hvKp group. The incidence of septic shock (P = 0.016) and Sequential Organ Failure Assessment (SOFA) scores (P < 0.001) are significantly higher in the hvKp group. Multivariate analysis indicated that cancer (odds ratio [OR] = 5.365) is an independent risk factor for VAP-hvKp infection.ConclusionsThe morbidity for elderly patients with VAP due to hvKp is high. MDR-HvKp is emerging, which is a great challenge for clinical practice.

Outbreak of hypervirulent Klebsiella pneumoniae harbouring blaVIM-2 among mechanically-ventilated drug-poisoning patients with high mortality rate in Iran.

Carbapenem-resistant Klebsiella pneumoniae infections are associated with increased rates of treatment failure and death. Several studies have reported isolates with a combined hypervirulent and antimicrobial-resistant phenotype. In this study, the molecular characteristics of hypervirulent K. pneumoniae (hvKP) isolated from mechanically-ventilated patients admitted to a toxicological intensive care unit (ICU) in Tehran, Iran, were examined. String test, antimicrobial susceptibility testing, virulence factors analysis and plasmid replicon typing were performed. The clonal relatedness of the isolates was analysed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). hvKP accounted for 9.4% (5/53) of K. pneumoniae isolated from ventilator-associated pneumonia among patients admitted to the ICU with acute drug poisoning. The mortality rate was 7.5% (4/53) among K. pneumoniae-infected patients. All fatal K. pneumoniae were hvKP isolates, were resistant to imipenem and harboured an aacA7, blaVIM-2 and dhfrI cassette arrangement in a class 1 integron. The isolates were shown to be ST23 (Pasteur scheme) and exhibited similar PFGE patterns. Plasmid analysis revealed a class 1 integron harbouring blaVIM-2 located on an ca. 45-kb IncN plasmid. Here we describe the emergence of VIM-2-producing hvKP serotype K1/ST23 in an outbreak with high mortality in a hospital toxicological ICU. It appears that we must alert and prepare the hospital's surveillance system for the appearance, expansion and clinical importance of new K. pneumoniae clones associated with high antimicrobial resistance and robust virulence capabilities.

Occurrence and characterization of hyperviscous K1 and K2 serotype in Klebsiella pneumoniae.

BACKGROUND:Klebsiella pneumoniae causes both nosocomial and community-associated infections. Hypervirulent K. pneumoniae (hvKP), new variant of K. pneumoniae, can cause invasive infections in young healthy individuals as well as in the immunocompromised population. Hypervirulent strains frequently belong to capsular serotypes K1 or K2. Emergence of antimicrobial resistance in hvKP is a cause for concern.AIM AND OBJECTIVE:The present study was done to detect the K1 and K2 serotypes among clinical isolates of K. pneumoniae, spectrum of infections caused by them and presence of common beta-lactamases encoding genes in them.MATERIALS AND METHODS:A total of 370 isolates of K. pneumoniae, isolated from various clinical samples over a period of 1 year was included in this study. Antibiotic susceptibility testing to various classes of antimicrobials was done as per Clinical and Laboratory Standard Institute guidelines. The presence of K2A (specific to serotype K2), magA (specific to serotype K1), and rmpA genes was detected by multiplex polymerase chain reaction (PCR). Extended-spectrum beta-lactamases (TEM, SHV, and CTX-M), plasmid-mediated AmpCs (MOX, CIT, DHA, ACC, EBC, and FOX), and carbapenemase genes (IMP, VIM, NDM, KPC, and OXA-48) were also determined by PCR.RESULTS:Among the 370 isolates, 8 harbored K2A gene and one harbored magA. rmpA gene was detected in three isolates along with K1 or K2 serotypes. Seven K2A-positive isolates were resistant to one or more classes of antimicrobials. The studied ESBL genes were present in four isolates. Two isolates harbored carbapenemase genes (NDM-1, OXA-48) along with ESBLs.CONCLUSION:K2 serotype is more prevalent among hvKP isolates. They can harbor ESBLs and Carbapenemase genes. K1 serotype is rather uncommon in K. pneumoniae. Acquisition of multidrug-resistant genes by these strains adds to their virulence and limits the treatment options.

High prevalence of hypervirulent Klebsiella pneumoniae infection in the genetic background of elderly patients in two teaching hospitals in China.

PurposeAerobactin is a critical factor for hypervirulent Klebsiella pneumoniae (hvKp) in genetic backgrounds, but data based on the genotype for the elderly is limited.Materials and methodsA retrospective study was conducted on elderly patients from June 2008 to July 2017 in 2 teaching hospitals. The clinical and microbiological data, including antimicrobial susceptibility testing, string test, extended-spectrum β-lactamase (ESBL) production, virulence gene, and multilocus sequence typing, of the hvKp group defined as aerobactin positive were compared with those of classic K. pneumoniae isolates.ResultsA total of 45.7% of 202 K. pneumoniae isolates were hvKp.ST23, which were predominant in 2 hospitals, but they were not highly associated with hvKp in different hospitals. Hypermucoviscosity, K1, K2, magA, and rmpA/A2 genes were highly related to hvKp (P=0.000). With regard to the host, invasive infections (P=0.000), liver abscess (P=0.000), abdominal infection (P=0.000), pneumonia (P=0.037), and septic shock (P=0.045) were significantly higher in the elderly with hvKp. In the hvKp group, patients with better nutritional status were associated with a more severe sequential organ failure assessment score and a more serious inflammation reaction. Patients with diabetes (odds ratio [OR]=2.566) are more likely to be infected with hvKp. Previous hvKp is associated with hypermucoviscosity (OR=15.249) are often paralleled with hvKp. Importantly, 26% of hvKp isolates produced ESBLs, and most of them showed a carbapenems-resistant (CR) phenotype. Multivariate analysis implied that patients with a history of surgery within the last 1 month (OR=15.999) is an independent risk factor for CR-hvKp infection.ConclusionThe prevalence of hvKP is high in the elderly. ESBL-hvKp, especially CR-hvKp, is emerging, which is a sign that clinical awareness and infection monitoring needs to improve.

Microbiological characteristics of hypermucoviscous Klebsiella pneumoniae isolates from different body fluids.

Reports of hypermucoviscous Klebsiella pneumoniae (hvKP) isolated from fluids other than blood or abscess are rare. The aim of the study was to compare clinical and microbiological characteristics of hvKP found in blood or abscess fluid with those isolated from other loci. A total of 24 non-repetitive hvKP isolates were collected from January 2013 to June 2014 from patients with hvKP infections. There were 15 in Group 1 (fluid other than blood or abscess) and 9 in Group 2 (blood or abscess fluid). Medical records of all patients were reviewed. Capsular polysaccharide (CPS) typing, virulence factor determination, and multilocus sequence typing (MLST) of hvKP isolates were performed. Seventeen sequence types (STs) and 6 capsular serotypes were identified. Type K2CC65 was most commonly identified in Group 1 and type K2CC86 in Group 2. Deletion of pLVPK-derived loci were found in K2 and non-K1/K2 hvKP strains. Two virulent genes, fimH and ycfM, were identified more frequently in Group 2 than in Group 1. There was no difference in the frequency of other virulent genes or serotypes in the two groups. Two imipenem resistant hvKP isolates (cr-hvKP) were found in non-blood or abscess samples. hvKP isolated from different body fluids had similar clinical and microbiological characteristics. cr-hvKP identified in non-blood or abscess samples should raise our attention to the challenging situation and management of hvKP infection.

Comparison of Diabetic and Non-diabetic Human Leukocytic Responses to Different Capsule Types of Klebsiella pneumoniae Responsible for Causing Pyogenic Liver Abscess.

The major risk factor for Klebsiella liver abscess (KLA) is type 2 diabetes mellitus (DM), but the immunological mechanisms involved in the increased susceptibility are poorly defined. We investigated the responses of neutrophils and peripheral blood mononuclear cells (PBMCs) to hypervirulent Klebsiella pneumoniae (hvKP), the causative agent of KLA. DNA and myeloperoxidase levels were elevated in the plasma of KLA patients compared to uninfected individuals indicating neutrophil activation, but diabetic status had no effect on these neutrophil extracellular trap (NET) biomarkers in both subject groups. Clinical hvKP isolates universally stimulated KLA patient neutrophils to produce NETs ex vivo, regardless of host diabetic status. Ability of representative capsule types (K1, K2, and non-K1/K2 strains) to survive intra- and extra-cellular killing by type 2 DM and healthy neutrophils was subsequently examined. Key findings were: (1) type 2 DM and healthy neutrophils exhibited comparable total, phagocytic, and NETs killing against hvKP, (2) phagocytic and NETs killing were equally effective against hvKP, and (3) hypermucoviscous K1 and K2 strains were more resistant to total, phagocytic, and NETs killing compared to the non-mucoviscous, non-K1/K2 strain. The cytokine response and intracellular killing ability of type 2 DM as well as healthy PBMCs upon encounter with the different capsule types was also examined. Notably, the IL-12–IFNγ axis and its downstream chemokines MIG, IP-10, and RANTES were produced at slightly lower levels by type 2 DM PBMCs than healthy PBMCs in response to representative K1 and non-K1/K2 strains. Furthermore, type 2 DM PBMCs have a mild defect in its ability to control hvKP replication relative to healthy PBMCs. In summary, our work demonstrates that type 2 DM does not overtly impact neutrophil intra- and extra-cellular killing of hvKP, but may influence cytokine/chemokine production and intracellular killing by PBMCs.

High Prevalence of Hypervirulent Klebsiella pneumoniae Infection in China: Geographic Distribution, Clinical Characteristics, and Antimicrobial Resistance.

Hypervirulent Klebsiella pneumoniae (hvKP) is traditionally defined by hypermucoviscosity, but data based on genetic background are limited. Antimicrobial-resistant hvKP has been increasingly reported but has not yet been systematically studied. K. pneumoniae isolates from bloodstream infections, hospital-acquired pneumonia, and intra-abdominal infections were collected from 10 cities in China during February to July 2013. Clinical data were collected from medical records. All K. pneumoniae isolates were investigated by antimicrobial susceptibility testing, string test, extended-spectrum β-lactamase (ESBL) gene detection, capsular serotypes, virulence gene profiles, and multilocus sequence typing. hvKP was defined by aerobactin detection. Of 230 K. pneumoniae isolates, 37.8% were hvKP. The prevalence of hvKP varied among different cities, with the highest rate in Wuhan (73.9%) and the lowest in Zhejiang (8.3%). Hypermucoviscosity and the presence of K1, K2, K20, and rmpA genes were strongly associated with hvKP (P < 0.001). A significantly higher incidence of liver abscess (P = 0.026), sepsis (P = 0.038), and invasive infections (P = 0.043) was caused by hvKP. Cancer (odds ratio [OR], 2.285) and diabetes mellitus (OR, 2.256) appeared to be independent variables associated with hvKP infections by multivariate analysis. Importantly, 12.6% of hvKP isolates produced ESBLs, and most of them carried blaCTX-M genes. Patients with neutropenia (37.5% versus 5.6%; P = 0.020), history of systemic steroid therapy (37.5% versus 5.6%; P = 0.020), and combination therapy (62.5% versus 16.7%; P = 0.009) were more likely to be infected with ESBL-producing hvKP. The prevalence of hvKP is high in China and has a varied geographic distribution. ESBL-producing hvKP is emerging, suggesting an urgent need to enhance clinical awareness, especially for immunocompromised patients receiving combination therapy.

Clinical and molecular characteristics of bloodstream infection caused by K. pneumonia

Objective To investigate the clinical features and molecular characteristics of bacteremia caused by K. pneumoniae and study on the differences between classical and hypervirulent K. pneumonia(hvKP). Methods The clinical features of 70 cases of K. pneumoniae bacteremia collected from Beijing Chaoyang Hospital from 2008 to 2012 were retrospectively analyzed. The patients were identified according to the records from the Clinical Microbiology Department. Patients' data were obtained from medical records. The molecular characteristics of the K. pneumoniae strains were also studied using PCR, multilocus sequence typing and pulsed field gel electrophoresis(PFGE) methods. Data were analyzed using the statistical package SPSS for windows version 17.0. For categorical data, different groups were compared using the Chi-square test to analyze the quantitative variables. P≤0.05 was considered to be statistically significant. All susceptibility data were analyzed using Whonet, version 5.6. Results The hvKP was identified from 31.4% of the patients with K. pneumoniae bacteremia, which displayed 4 serotypes (K1, K2, K20, and K57). About 40.9% (9/22) hypervirulent strains were isolated from patients without underlying diseases, while 95.8% (46/48) of the classic K. pneumoniae infections were found in patients with the presence of one or more underlying diseases. More hvKP positive patients (95.5%, 21/22) had community-acquired infections compared with classical K. pneumonia (cKP) infected patients (35.4%, 17/48). There was a significant difference between these two groups (χ2=21.912, P<0.001). Two ESBLs-producing hvKP strains were found. The 22 hvKP isolates had 14 different PFGE patterns, among which 6 isolates (patients with primary liver abscess) shared similar PFGE patterns. Conclusions The emerging hvKP was prevalent in patients with severe community-acquired infections in healthy individuals. Two ESBLs-producing hvKP strains were identified. Drug resistance had a rising trend, which called for more attention in clinical settings. (Chin J Lab Med, 2015, 38: 627-631) Key words: Liver abscess; Community-acquired infections; Klebsiella pneumoniae; Virulence

Mapping the Evolution of Hypervirulent Klebsiella pneumoniae.

ABSTRACTHighly invasive, community-acquired Klebsiella pneumoniae infections have recently emerged, resulting in pyogenic liver abscesses. These infections are caused by hypervirulent K. pneumoniae (hvKP) isolates primarily of capsule serotype K1 or K2. Hypervirulent K1 isolates belong to clonal complex 23 (CC23), indicating that this clonal lineage has a specific genetic background conferring hypervirulence. Here, we apply whole-genome sequencing to a collection of K. pneumoniae isolates to characterize the phylogenetic background of hvKP isolates with an emphasis on CC23. Most of the hvKP isolates belonged to CC23 and grouped into a distinct monophyletic clade, revealing that CC23 is a unique clonal lineage, clearly distinct from nonhypervirulent strains. Separate phylogenetic analyses of the CC23 isolates indicated that the CC23 lineage evolved recently by clonal expansion from a single common ancestor. Limited grouping according to geographical origin was observed, suggesting that CC23 has spread globally through multiple international transmissions. Conversely, hypervirulent K2 strains clustered in genetically unrelated groups. Strikingly, homologues of a large virulence plasmid were detected in all hvKP clonal lineages, indicating a key role in K. pneumoniae hypervirulence. The plasmid encodes two siderophores, aerobactin and salmochelin, and RmpA (regulator of the mucoid phenotype); all these factors were found to be restricted to hvKP isolates. Genomic comparisons revealed additional factors specifically associated with CC23. These included a distinct variant of a genomic island encoding yersiniabactin, colibactin, and microcin E492. Furthermore, additional novel genomic regions unique to CC23 were revealed which may also be involved in the increased virulence of this important clonal lineage.

Molecular identification and antimicrobial resistance analysis of a new hypervirulent variant of Klebsiella pneumoniae

Objective To investigate the infection case and drug resistance patterns of new hypervirulent (hypermucoviscous) clinical variant of Klebsiella pneumoniae(hvKP)strains, and the virulence and resistance mechanisms. Methods Retrospective study.Two hundred and ten Klebsiella pneumoniae isolates were collected in the First Affiliated Hospital of Nanchang University from January 2011 to December 2013, and 12 hvKP were identified. Multilocus sequence typing (MLST) and enterobacterial repetitive intergenic consensus (ERIC)-PCR were used to type the hvKP isolates. The extended spectrum β-lactamase and carbapenemase producing Klebsiella pneumoniae were screened by the double disc synergy test and the modified Hodge test, respectively. PCR and DNA sequencing were carried out to detect their resistance related genes, serotype and virulence genes. Hypermucoviscosity phenotype (HM) of all strains was determined by string test. Results HvKP were resistant to 15 antibiotics and the extended-spectrum beta-lactamase producing rate was 8/12. In addition, one strain was detected positive by the modified Hodge test. Among the 12 hvKP strains, five ERIC-MLST molecular types were identified, of which A/ST23 and B/ST263 were the most predominant types, accounting for 5/12 and 4/12, respectively. The results of PCR and DNA secquencing showed that 2 were positive for blaKPC-2 (2/12), 9 positive for qnrA1 (9/12), 6 positive for qnrB4 (6/12), 8 positive for qnrS1 (8/12), 6 positive for blaCTX-M-3 (6/12), 7 positive for blaCTX-M-14 (7/12), 10 positive for blaTEM-1 (10/12), and 4 positive for blaSHV-12 (4/12). Eleven hvKP strains were serotype K1, while only one strain was serotype K2. Serotype K3, K5, K20, K54 and K57 were not detected. The positive rate of virulence genes magA, rmpA and aerobactin were 11/12, 9/12 and 9/12, respectively. In addition, the positive rate of kfu, mrkD, wabG and allS were 9/12, 10/12, 4/12 and 2/12, respectively. The positive rate of HM was 8/12. Conclusions The resistance mechanism of hvKP strains was complex and diverse, in which strong toxicity serotype and multiple virulence genes exist, which need attention from clinic. Effective infection control measure should be conducted in order to control the outbreak of resistant hvKP strains. (Chin J Lab Med, 2015, 38: 392-396) Key words: Klebsiella pneumoniae; Virulence; Drug resistance, bacterial; Serotyping

Clinical and molecular characteristics of emerging hypervirulent Klebsiella pneumoniae bloodstream infections in mainland China.

Recently, the newly emerged hypervirulent Klebsiella pneumoniae strain (hvKP) has caused great concern globally, but the clinical features and molecular characteristics of bacteremia caused by hvKP are rarely reported in mainland China. Seventy patients with K. pneumoniae bacteremia were investigated to study the clinical features of hvKP infection from 2008 till 2012 in Beijing Chao-Yang Hospital. The molecular characteristics of the hvKP strains were also studied using PCR, multilocus sequence typing, and pulsed-field gel electrophoresis (PFGE) methods. hvKP was identified in 31.4% of the patients with K. pneumoniae bacteremia, which displayed 4 serotypes (K1, K2, K20, and K57). Patients with hvKP infection tended to have no underlying diseases compared to those with classic K. pneumoniae (cKP). More hvKP-positive patients (95.5%) had community-acquired infection than did cKP-infected patients (35.4%) (P<0.001). The 30-day mortality rate was lower in hvKP-infected patients than in cKP-infected patients (4.5% compared to 16.7%). Resistance to tested antimicrobials was significantly greater in cKP- than in hvKP-infected patients. Two extended-spectrum-beta-lactamase (ESBL)-producing hvKP strains were found. Seven novel sequence types (STs) and 4 new alleles of K. pneumoniae were revealed. A strong correlation was found between two STs (ST23, ST1265) and the K1 serotype. The hvKP isolates (n=22) had 14 different PFGE patterns, and among them 10 K1 isolates shared similar PFGE patterns. The emerging hvKP strain was prevalent in patients with severe community-acquired infections in healthy individuals in China. Identification of ESBL-producing hvKP strains in hvKP-infected patients will facilitate clinical management of hvKP infection.

Increasing Occurrence of Antimicrobial-Resistant Hypervirulent (Hypermucoviscous) Klebsiella pneumoniae Isolates in China

New hypervirulent variants of Klebsiella pneumoniae (hvKP) are emerging globally, most of which exhibit antimicrobial susceptibility. A retrospective study was conducted in 88 patients with cultures positive for K. pneumoniae hospitalized in the Beijing You'an Hospital from April 2010 to June 2012. The clinical and molecular data of the hvKP isolates (defined as string test positive) were compared with those of the classic K. pneumoniae (cKP) isolates. Overall, 33.0% (29/88) of K. pneumoniae isolates were hvKP. Univariate analysis revealed the following risk factors for hvKP: virulence gene rmpA (odds ratio [OR], 16.92 [95% confidence interval {CI}, 4.842-59.145]), capsule antigens K1 (OR, 3.355 [95% CI, 1.153-9.768]) and K2 (OR, 9.280 [95% CI, 0.987-87.250]), alcoholic hepatitis (OR, 7.435 [95% CI, 1.397-39.572]), liver abscess (OR, 9.068 [95% CI, 1.747-47.061]), metastatic infection (OR, 2.752 [95% CI, 1.100-6.886]), community-acquired infection (OR, 10.432 [95% CI, 3.623-30.033]), sputum isolation (OR, 0.312 [95% CI, .095-1.021]), and HIV infection (<0.001 [not applicable]). Multivariate analysis implicated rmpA (OR, 17.398 [95% CI, 4.224-71.668]) and community-acquired infection (OR, 6.844 [95% CI, 1.905-24.585]) as independent risk factors. The proportion of hvKP isolates increased from April to December 2010, January to September 2011, and October 2011 to June 2012 (to 25.5%, 26.7%, and 54.5%, respectively). Resistance to 14 of 19 tested antimicrobials was found to be significantly greater in cKP compared to hvKP. Importantly, resistance to all the tested antimicrobials, except carbapenems and amikacin, was observed in a proportion of hvKP strains, 17% (5/29) of which expressed extended-spectrum β-lactamase. Furthermore, antimicrobial resistance in hvKP strains increased over time. HvKP strains are being isolated from patients in China with increasing frequency and constitute an increasing proportion of K. pneumoniae strains, indicating an increasing propensity for the acquisition of antimicrobial resistance.