Molecular epidemiology of Klebsiella pneumoniae K1 and K2 isolates in Japan

Molecular Characteristics of Virulence Genes in Carbapenem-Resistant and Carbapenem-Sensitive Klebsiella Pneumoniae in Relation to Different Capsule Serotypes in Ningbo, China

Background

Klebsiella pneumoniae (KP) is a common nosocomial pathogen. Capsules are an important component of KP's virulence, among which the K1, K2, K5, K20, K54, and K57 serotypes are predominant and exhibit varying degrees of virulence.

Methods

The capsule and virulence genes of 150 carbapenem-resistant Klebsiella pneumoniae (CRKP) and 213 carbapenem-sensitive Klebsiella pneumoniae (CSKP) isolates were examined by polymerase chain reaction (PCR). The isolates were tested for hypermucoviscosity by string tests. Phylogenetic relationships between KP isolates were analyzed using multilocus sequence typing (MLST) and a Galleria mellonella infection model confirmed the differences in virulence.

Results

A total of 111 of 363 isolates of KP were detected, the highest detected serotypes were K1, K5, and K2, and CSKP was detected more frequently than CRKP. There was a greater prevalence of K1 and K2 serotypes in CSKP, while in CRKP, K5 serotypes were more prevalent. K1 isolates had the highest detection rates for hypermucoviscosity Klebsiella pneumoniae (hmKP) and hypervirulent Klebsiella pneumoniae (hvKP), and carried the most virulence genes. K54 isolates had the lowest detection rate of hmKP while K5 isolates had the lowest detection rate of hvKP and carried the fewest virulence genes. MLST results for serotypes K1, K20, and K57 showed significant homogeneity, while those for serotypes K2, K5, and K54 showed diversity. The Galleria mellonella infection model showed that the K1 serotype was the most virulent and the K54 serotype was the weakest.

Conclusion

CSKP isolates were detected more frequently than CRKP isolates for capsular serotype detection. K1 isolates had the most virulence gene and strongest virulence, K5 isolates carried the fewest virulence genes, and K54 isolates had the weakest virulence. Furthermore, significant homogeneity was observed among K1, K20, and K57 isolates.

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.

Prevalence, clonal diversity, and antimicrobial resistance of hypervirulent Klebsiella pneumoniae and Klebsiella variicola clinical isolates in northern Japan

OBJECTIVES

Hypervirulent Klebsiella pneumoniae (hvKp) and Klebsiella variicola (hvKv) cause hospital/community-acquired infections, often associated with antimicrobial resistance (AMR). This study aimed to investigate the molecular epidemiology of hvKp and hvKv in northern Japan.

METHODS

A total of 500 K. pneumoniae and 421 K. variicola clinical isolates collected from August to December 2021 were studied. Prevalence of virulence factor-encoding genes, wzi sequence and associated K/KL type, sequence type (ST), and beta-lactamases and their types were characterized.

RESULTS

Any virulence gene (rmpA, rmpA2, peg-344, iucA, iutA, and iroB) and/or magA was detected in 25% (n = 125) of K. pneumoniae and 1% (n = 5) of K. variicola. Among these hvKp/hvKv, 22 wzi types (18 and 4 types, respectively) and 24 STs (20 and 4 STs, respectively) were identified. Sequence types of hvKp were classified into some clonal groups (CGs), among which CG35, including six STs, was the most common (n = 59; 47%), followed by CG23, and CG65. ST268 (CG35) associated with wzi95-K20 or wzi720 was the dominant lineage (n = 43, 34%), while K1:ST23/ST249 and K2:ST65/ST86 accounted for 26% and 13% of hvKp, respectively. Extended-spectrum beta-lactamase (ESBL) genes (blaCTX-M-2, blaCTX-M-3, blaCTX-M-15, and blaCTX-M-27) were detected in only ST23 and CG35 (ST268 and ST412) hvKp. No isolate was resistant to carbapenems, without detection of the ESBL gene in K. variicola. Phylogenetically, wzi was differentiated into two main clusters of K. pneumoniae and K. variicola. A major clonal group CG347 was identified in K. variicola.

CONCLUSION

Clonal structures were revealed for hvKp and hvKv clinical isolates with their AMR status in northern Japan.

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.

Characterization of bacteriophage BUCT631 lytic for K1 Klebsiella pneumoniae and its therapeutic efficacy in Galleria mellonella larvae

Severe infections caused by multidrug-resistant Klebsiella pneumoniae (K. pneumoniae) highlight the need for new therapeutics with activity against this pathogen. Phage therapy is an alternative treatment approach for multidrug-resistant K. pneumoniae infections. Here, we report a novel bacteriophage (phage) BUCT631 that can specifically lyse capsule-type K1 K. pneumoniae. Physiological characterization revealed that phage BUCT631 could rapidly adsorb to the surface of K. pneumoniae and form an obvious halo ring, and it had relatively favorable thermal stability (4-50 ​°C) and pH tolerance (pH ​= ​4-12). In addition, the optimal multiplicity of infection (MOI) of phage BUCT631 was 0.01, and the burst size was approximately 303 ​PFU/cell. Genomic analysis showed that phage BUCT631 has double-stranded DNA (total length of 44,812 bp) with a G ​+ ​C content of 54.1%, and the genome contains 57 open reading frames (ORFs) and no virulence or antibiotic resistance related genes. Based on phylogenetic analysis, phage BUCT631 could be assigned to a new species in the genus Drulisvirus of the subfamily Slopekvirinae. In addition, phage BUCT631 could quickly inhibit the growth of K. pneumoniae within 2 ​h in vitro and significantly elevated the survival rate of K. pneumoniae infected Galleria mellonella larvae from 10% to 90% in vivo. These studies suggest that phage BUCT631 has promising potential for development as a safe alternative for control and treatment of multidrug-resistant K. pneumoniae infection.

Clinical and Molecular Characteristics and Antibacterial Strategies of Klebsiella pneumoniae in Pyogenic Infection

Treatment of Klebsiella pneumoniae causing pyogenic infections is challenging. The clinical and molecular characteristics of Klebsiella pneumoniae causing pyogenic infections are poorly understood, and antibacterial treatment strategies are limited. We analyzed the clinical and molecular characteristics of K. pneumoniae from patients with pyogenic infections and used time-kill assays to reveal the bactericidal kinetics of antimicrobial agents against hypervirulent K. pneumoniae (hvKp). A total of 54 K. pneumoniae isolates were included, comprising 33 hvKp and 21 classic K. pneumoniae (cKp) isolates, and the hvKp and cKp isolates were identified using five genes (iroB, iucA, rmpA, rmpA2, and peg-344) that have been applied as hvKp strain markers. The median age of all cases was 54 years (25th and 75th percentiles, 50.5 to 70), 62.96% of individuals had diabetes, and 22.22% of isolates were sourced from individuals without underlying disease. The ratios of white blood cells/procalcitonin and C-reactive protein/procalcitonin were potential clinical markers for the identification of suppurative infection caused by hvKp and cKp. The 54 K. pneumoniae isolates were classified into 8 sequence type 11 (ST11) and 46 non-ST11 strains. ST11 strains carrying multiple drug resistance genes have a multidrug resistance phenotype, while non-ST11 strains carrying only intrinsic resistance genes are generally susceptible to antibiotics. Bactericidal kinetics revealed that hvKp isolates were not easily killed by antimicrobials at susceptible breakpoint concentrations compared with cKp. Given the varied clinical and molecular features and the catastrophic pathogenicity of K. pneumoniae, it is critical to determine the characteristics of such isolates for optimal management and effective treatment of K. pneumoniae causing pyogenic infections. IMPORTANCE Klebsiella pneumoniae may cause pyogenic infections, which are potentially life-threatening and bring great challenges for clinical management. However, the clinical and molecular characteristics of K. pneumoniae are poorly understood, and effective antibacterial treatment strategies are limited. We analyzed the clinical and molecular features of 54 isolates from patients with various pyogenic infections. We found that most patients with pyogenic infections had underlying diseases, such as diabetes. The ratio of white blood cells to procalcitonin and the ratio of C-reactive protein to procalcitonin were potential clinical markers for differentiating hypervirulent K. pneumoniae strains from classical K. pneumoniae strains that cause pyogenic infections. K. pneumoniae isolates of ST11 were generally more resistant to antibiotics than non-ST11 isolates. Most importantly, hypervirulent K. pneumoniae strains were more tolerant to antibiotics than classic K. pneumoniae isolates.

Emergence of Carbapenemase-Producing Hypervirulent Klebsiella pneumoniae in Switzerland

Increasing occurrence of multidrug-resistant (MDR) and hypervirulent (hv) Klebsiella pneumoniae (MDR-hvKp) convergent clones is being observed. Those strains have the potential of causing difficult-to-treat infections in healthy adults with an increased capacity for mortality. It is therefore crucial to track their dissemination to prevent their further spread. The aim of our study was to investigate the occurrence of carbapenemase-producing hvKp isolates in Switzerland and to determine their genetic profile. A total of 279 MDR carbapenemase-producing K. pneumoniae from patients hospitalized all over Switzerland was investigated, and a rate of 9.0% K. pneumoniae presenting a virulence genotype was identified. Those isolates produced either KPC, NDM, or OXA-48 and had been either recovered from rectal swabs, urine, and blood. A series of previously reported K. pneumoniae clones such as ST23-K1, ST395-K2, and ST147-K20 or ST147-K64 were identified. All the isolates defined as MDR-hvKp (4.7%) possessed the aerobactin and the yersiniabactin clusters. The ST23-K1s were the only isolates presenting the colibactin cluster and achieved higher virulence scores. This study highlights the occurrence and circulation of worrisome MDR-hvKp and MDR nonhypervirulent K. pneumoniae (MDR-nhv-Kp) isolates in Switzerland. Our findings raise an alert regarding the need for active surveillance networks to track and monitor the spread of such successful hybrid clones representing a public health threat worldwide.

Comparative genetic analysis of the antimicrobial susceptibilities and virulence of hypermucoviscous and non-hypermucoviscous ESBL-producing Klebsiella pneumoniae in Japan

BACKGROUND

Hypermucoviscous (HMV) Klebsiella pneumoniae produces large amounts of capsular polysaccharides, leading to high mortality. Since extended spectrum beta-lactamase (ESBL)-producing HMV K. pneumoniae strains have increased in Japan, we investigated and compared the antimicrobial susceptibilities and genetic characteristics of HMV and non-HMV ESBL-producing K. pneumoniae.

METHODS

We investigated 291 ESBL-producing K. pneumoniae collected between 2012 and 2018, and in them 54 HMV strains were identified and comparable 53 non-HMV strains were selected. Then, ESBL gene detection, plasmid replicon typing, and virulence gene detection were done by PCR amplification.

RESULTS

Almost all of the HMV K. pneumoniae strains possessed uge (98.1%), wabG (96.3%), rmpA (94.4%), iucA (79.6%), fimH (70.4%), iroB (70.4%), and peg-344 (70.4%). These genes were found less frequently in non-HMV strains (uge 20.8%, wabG 83.0%, rmpA 7.5%, iucA 3.8%, fimH 9.4%, iroB 5.7%, and peg-344 1.9%). K2 capsule type (40.7%) was most common in HMV strains. HMV strains showed higher resistance to cefepime (p = 0.001) and piperacillin/tazobactam (p = 0.005) than non-HMV strains. CTX-M-15 (75.9%, 60.4%) was the dominant ESBL type in both HMV and non-HMV strains, and the most common plasmid replicon type was IncFII (52.1%) in CTX-M-15-producing strains.

CONCLUSIONS

We found that HMV strains had more virulence genes and showed higher resistance to antibiotics than non-HMV strains. The most common capsule type was K2. CTX-M-15 was the most common type of ESBL gene in both HMV and non-HMV strains in Japan. The FII plasmid might be related to the spread of CTX-M-15 among K. pneumoniae strains.

Coexistence of Multidrug Resistance and Virulence in a Single Conjugative Plasmid from a Hypervirulent Klebsiella pneumoniae Isolate of Sequence Type 25

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) has received considerable attention. Typically, the genetic elements that confer virulence are harbored by nonconjugative plasmids. In this study, we report a CR-hvKP strain, CY814036, of high-risk sequence type 25 (ST25) and the K2 serotype, which is uncommon among K. pneumoniae isolates but caused serious lung infection in a tertiary teaching hospital in China. Whole-genome sequencing (WGS) revealed a rare conjugative plasmid, pCY814036-iucA, carrying a virulence-associated iuc operon (iucABCD-iutA) coding for aerobactin and determinants of multidrug resistance (MDR), coexisting with a conjugative bla_KPC-2-bearing plasmid, pCY814036-KPC2, in the same strain. A conjugation assay showed that pCY814036-iucA and pCY814036-KPC2 could be efficiently cotransmitted from CY814036 to Escherichia coli EC600. Further phenotypic investigation, including antimicrobial susceptibility tests, serum resistance assays, and mouse infection models, confirmed that pCY814036-iucA was capable of cotransferring multidrug resistance and hypervirulence features to the recipient. pCY814036-KPC2 also conferred resistance to antibiotics, including β-lactams and aminoglycosides. Overall, the rare coexistence of a conjugative MDR-virulence plasmid and a bla_KPC-2-bearing plasmid in a K. pneumoniae isolate offers a possible mechanism for the formation of CR-hvKP strains and the potential to significantly accelerate the propagation of high-risk phenotypes. IMPORTANCE The increased reporting of carbapenem-resistant hypervirulent K. pneumoniae is considered a worrisome concern to human health care and has restricted the choice of effective antibiotics for clinical treatment. Moreover, virulence plasmids with complete conjugation modules have been identified, which evolved via homologous recombination. Here, we characterize an ST25 CR-hvKP strain, CY814036, harboring both a conjugative MDR-virulence plasmid and a bla_KPC-2-bearing plasmid in China. This study highlights that the cotransmission of drug resistance and virulence plasmids increases therapeutic difficulties and worsens clinical prognoses. Also, active surveillance of the conjugative MDR-virulence plasmid is necessary.

Biotyping, Virulotyping and Biofilm Formation Ability of ESBL-Klebsiella pneumoniae Isolates from Nosocomial Infections

The aim of this study was to investigate the frequency, molecular characterization, virulence genes, resistance genes and antimicrobial profile of nosocomial extended spectrum beta lactamase producing Klebsiella species. A total of 22 (12.2%) K. pneumoniae strains were isolated from 180 clinical samples collected from hospitalized patients in Egypt. K. pneumoniae biotypes were B1 (72.8%), B3 (13.6%) and B4 (13.6%). The isolates were classified for the capsular serotypes, 86.4% (20/22) were of K1 serotype, while only two isolates (13.64%) were of K2 serotype. Hypermucoviscous K. pneumoniae isolates accounted for 68.2%. Biofilm formation ability of K. pneumoniae was determined by microtitre plate method. The majority of the isolates (40.9%) were moderate biofilm producers, while 27.3% were strong biofilm producers. All K. pneumoniae strains were positive for fimH and traT genes, while magA was identified in only 63.6% of the isolates. The antibiotic susceptibility profile of the isolates (n=22) was determined by the disc diffusion technique using 23 different antibiotics. Streptomycin and imipenem are the most effective antibiotics against 22 tested K. pneumoniae isolates with sensitivity rates of 63.64% and 54.54%, respectively. All tested K. pneumoniae isolates showed high resistance to amoxicillin∕clavulanate (100%), cefuroxime (100%) and ceftazidime (95.45%). Extended spectrum beta lactamases (ESBL) production and the presence of ESBL related genes were tested in the isolates. All the isolates tested positive for blaVIM, NDM1, and blaTEM, while only 81.8 percent tested positive for the blaSHV gene. Increasing antimicrobial resistance in K. pneumoniae causing nosocomial infections limits the use of antimicrobial agents for treatment. Furthermore, the spread of biofilm, multiple drug resistant and ESBL-producing K. pneumoniae isolates is a public threat for hospitalized patients.

Ruptured Emphysematous Prostatic Abscess Caused by K1-ST23 Hypervirulent Klebsiella pneumoniae Presenting as Brain Abscesses: A Case Report and Literature Review

Emphysematous prostatic abscess (EPA) is an extremely rare but potentially fatal urinary tract infection (UTI). Here, we describe a case (a 69-year-old male with prediabetes) of ruptured EPA caused by a hypervirulent Klebsiella pneumoniae (hvKp) K1-ST23 strain, presenting as motor aphasia. Our patient presented with ruptured EPA concurrent with various severe systemic pyogenic complications (e.g., urethro-prostatic fistula, ascending UTIs, epididymal and scrotal abscesses, and liver, lung, and brain abscesses). Whole-body computed tomography (CT) and next-generation sequencing (NGS) were useful for the detection of ruptured EPA and its systemic complications, and for identification of K1-ST23 hvKp strains, respectively. Subsequently, the infections were successfully treated with aggressive antimicrobial therapy and multiple surgical procedures. This case highlights the significance of awareness of this rare entity, the clinical importance of CT for the early diagnosis of EPA and the detection of its systemic complications in view of hvKp being an important causative organism of severe community-acquired UTI, and the usefulness of NGS to identify hvKp strains.

The first case of abdominal mycotic aneurysm caused by K1 hypervirulent Klebsiella pneumoniae in a healthy adult

Incidence of hypervirulent Klebsiella pneumoniae (hvKp) infection has been steadily increasing in the Asia-Pacific rim. The characteristic of hvKp infection is its ability to cause multiple site infections and unpredictable metastatic spread in the community. We describe the first case of mycotic aneurysm caused by hvKp serotype K1 in a previously healthy man and review the literature. Of a total of 13 cases, including our case, three cases were related to hvKp. Among patients with hvKp, the level of mycotic aneurysm in most patients was the infrarenal aorta, and they underwent an aortic graft or coil embolization. All strains were susceptible to most antimicrobial agents, except ampicillin. Early detection of hvKp can help to prevent the metastatic spread of pathogens and be useful for optimal patient care and epidemiologic research.

Characterization of multidrug-resistant and virulent Klebsiella pneumoniae strains belonging to the high-risk clonal group 258 (CG258) isolated from inpatients in northeastern Brazil

Multidrug-resistant (MDR) and hypervirulent Klebsiella pneumoniae (hvKp) clones have become a major threat to global public health. The clonal group 258 (CG258) is considered a high-risk CG and the K. pneumoniae strains belonging to it are often multi-resistant and to spread mainly in the hospital environment. This study aimed to characterize the antimicrobial resistance profile, virulence factors, and the clonal relationships among 13 K. pneumoniae strains belonging to CG258 from patients admitted to a tertiary hospital in Teresina, in the state of Piauí, northeastern Brazil. Ten strains were classified as MDR and three as extensively drug-resistant (XDR). Three different β-lactamase-encoding genes (bla_KPC, bla_OXA-1-like, and bla_CTX-M-Gp1) and six virulence genes (fimH, ycfM, mrkD, entB, ybtS, and kfu) were detected. Moreover, two hypermucoviscous K. pneumoniae strains and one capsular K-type 2 were found. Multilocus sequence typing analysis revealed ten different sequence types (STs) (ST14, ST17, ST20, ST29, ST45, ST101, ST268, ST1800, ST3995, and ST3996) belonging to CG258, being two (ST3995 and ST3996) described for the first time in this study.

Infection with capsular genotype K1-ST23 hypervirulent Klebsiella pneumoniae isolates in Japan after a stay in East Asia: Two cases and a literature review

Disseminated community-acquired infections caused by the hypervirulent Klebsiella pneumoniae (hvKp) among relatively healthy individuals in East Asia have been reported in recent years. Isolate of the capsular genotype K1, belonging to sequence type (ST) 23, is the most common causative agent of this disease. We experienced two cases of K1-ST23 infection with a travel history in East Asia, and hvKp infection was diagnosed after entering or returning to Japan. Case 1 was a 45-year-old Myanmar seaman with a history of ischemic heart disease who developed a fever on board and was transported to Japan via Shanghai and Taiwan. He had multiple disseminated lesions due to K. pneumoniae; other symptoms included liver abscess, intraocular inflammation, intraventricular thrombosis, brain abscess, and bloodstream infection. Along with antimicrobial treatment, drainage of liver abscesses and surgery for intraocular inflammation and intraventricular thrombosis were required. The patient was discharged 93 days after admission, with little improvement in the visual acuity. Case 2: A 29-year-old Japanese man with no underlying disease developed a prostate abscess and bloodstream infection caused by K. pneumoniae after a trip to Korea. However, he improved only with antimicrobial treatment. K. pneumoniae in both cases were identified to have the rmpA gene, with capsular genotypes K1 and ST23. Further, both cases were considered to have been infected with hvKp during their stay in East Asia. In conclusion, it is important to suspect disseminated disease and perform a systemic search, taking into account that hvKp may be present in cases of Klebsiella infection acquired from East Asia.

Characterization of blaKPC-2-Harboring Klebsiella pneumoniae Isolates and Mobile Genetic Elements from Outbreaks in a Hospital in Ecuador

Aim: To investigate the mobile genetic elements harboring bla_KPC gene in carbapenem-resistant Klebsiella pneumoniae recovered during a 6-month outbreak in a high-complexity hospital from Ecuador. Results: A total of 62 isolates belonging to ST258 pilv-I-positive (n = 45), ST25 serotype K2 (n = 8), ST348 (n = 6), ST42 (n = 1), ST196 (n = 1), and ST1758 (n = 1) were collected from intensive care unit (ICU), neurosurgery, burn unit, internal medicine, pneumology, and neurology. Pulsed-field gel electrophoresis analysis showed two major clusters of ST258 and ST25 related to bloodstream infections and pneumonia circulating in ICU. The PCR assay showed that in non-ST258 isolates, the bla_KPC-2 gene were located on the Tn4401a transposon inserted in the transferable pKpQIL-like IncFII_K2 plasmid; the whole-genome sequencing of ST258 clone showed two plasmids, the bla_KPC-2 gene was located on nonconjugative IncR plasmid, whereas the IncFIB/IncFII plasmid lacked ß-lactamase genes. We found an IncM plasmid in bla_KPC-2-harboring Klebsiella pneumoniae ST1758 clone. Conclusions: These findings highlight the presence of pKpQIL-like plasmids in non-ST258 and nonconjugative plasmids in ST258 isolates causing hospital outbreaks.

Molecular and Epidemiological Characteristics of Carbapenemase-Producing Klebsiella pneumoniae Clinical Isolates in Japan

Carbapenems serve as a last resort for the clinical treatment of multidrug-resistant infections. Therefore, the rapid spread of carbapenemase-producing strains represents a serious public health threat, further limiting antibiotic choices. The current findings of hypervirulent carbapenemase-producing Klebsiella pneumoniae clinical isolates in Japan demonstrate the potential broad spread and transfer of these genes, necessitating close surveillance.

Carbapenemase-producing Enterobacteriaceae represent a serious public health threat worldwide. Carbapenemase genes, harbored on a transferable plasmid, have been isolated globally with distinct geographical features. Klebsiella pneumoniae, included in Enterobacteriaceae, also produces carbapenemase and often shows hypervirulence. Overlapping carbapenem resistance and hypervirulence in K. pneumoniae have been reported, but such strains have not yet been found in Japan. Here, we screened 104 carbapenemase-producing K. pneumoniae isolates collected from 37 hospitals and outpatient clinics in Japan between September 2014 and July 2015. PCR and DNA sequencing demonstrated IMP-1 in 21 isolates and IMP-6 in 83 isolates, 77 of which coharbored CTX-M-2. Most of the isolates showed low MICs toward imipenem and meropenem but high MICs toward penicillin and cephalosporins. Conjugation experiments with an Escherichia coli J53 recipient showed that most of the plasmids in IMP-6 producers were transferable, whereas only one-half of the plasmids in IMP-1 producers were transferable. PCR-based replicon typing and multiplex PCR identified five isolates belonging to the CG258 non-tonB79 cluster and no isolate belonging to the CG258-tonB79 cluster or sequence type 307 (ST307). Four K1-ST23 isolates, 10 K2-ST65 isolates, and 7 K2-ST86 isolates were detected that harbored virulence genes. The resistance genes in 85 isolates were transferable, but the virulence genes were not transferred. These results demonstrate the acquisition of IMP-type carbapenemase genes and CTX-M-type genes among hypervirulence isolates in Japan, warranting further attention and countermeasures. In this study, we have determined the molecular characteristics and epidemiology of IMP-6 producers that coharbored various CTX-M genes in Japan.

IMPORTANCE Carbapenems serve as a last resort for the clinical treatment of multidrug-resistant infections. Therefore, the rapid spread of carbapenemase-producing strains represents a serious public health threat, further limiting antibiotic choices. The current findings of hypervirulent carbapenemase-producing Klebsiella pneumoniae clinical isolates in Japan demonstrate the potential broad spread and transfer of these genes, necessitating close surveillance.

Case Report of Primary Lung Abscesses Due to Hypervirulent Klebsiella pneumoniae (Serotype K2, Sequence Type 375): an Emerging Isolate in Okinawa, Japan

Hypervirulent Klebsiella pneumoniae (HV-KP) is typically associated with community-acquired liver abscess and bacteremia with metastatic infection; however, primary lung abscess (PLA) caused by HV-KP is rare, with only one such case report to date. A 69-year-old man with a history of diabetes mellitus (DM) was admitted to hospital complaining of slight bloody sputum. Chest imaging showed multiple consolidations with cavities in both lung fields. A culture of bronchoalveolar lavage fluid confirmed the presence of K. pneumoniae. Genetic analyses identified the isolate as serotype K2 and sequence type 375 (K2-ST375), and that it harbored the rmpA gene. The patient was an Asian middle-aged male with DM, all of which are risk factors for HV-KP infection. Although complicating DM and the presence of the rmpA gene are more likely to induce disseminated infection, metastatic infections were not found in this patient. The clinical and microbiological characteristics of our patient were different from those of a previous reported case, although in both cases the patient was from Asia and had DM. Therefore, DM appears to be one of the predisposing factors for HV-KP lung abscesses and physicians should pay attention to emerging HV-KP lung abscess infection, particularly in Asian countries. Previous studies have also revealed that K2-ST375 is one of the major clones causing HV-KP infection, and that it is mainly isolated from patients with liver abscess. Interestingly, including the present case, most of the infectious cases caused by K2-ST375 have been reported from Okinawa Prefecture in Japan. Therefore, the trend of the K2-ST375 strain should be carefully monitored, particularly in Okinawa, Japan. The serotype of HV-KP that causes PLA is still unknown and further study is needed to elucidate the etiology of PLA due to HV-KP and the relationship between the strain K2-ST375 and PLA.

Fatal fulminant community-acquired pneumonia caused by hypervirulent Klebsiella pneumoniae K2-ST86: Case report

RATIONALE

Invasive community-acquired infections, including pyogenic liver abscesses, caused by hypervirulent Klebsiella pneumoniae (hvKp) strains have been well recognized worldwide. Among these, sporadic hvKp-related community-acquired pneumonia (CAP) is an acute-onset, rapidly progressing disease that can likely turn fatal, if left untreated. However, the clinical diagnosis of hvKp infection remains challenging due to its non-specific symptoms, lack of awareness regarding this disease, and no consensus definition of hvKp.

PATIENT CONCERNS

A 39-year-old man presented with high-grade fever and sudden-onset chest pain. Laboratory testing revealed an elevated white blood cell count of 11,600 cells/μl and C-reactive protein level (>32 mg/dl). A chest X-ray and computed tomography revealed a focal consolidation in the left lower lung field.

DIAGNOSIS

Diagnosis of fulminant CAP caused by a hvKp K2-ST86 strain was made based upon multilocus sequencing typing (MLST).

INTERVENTIONS

The patient was treated with ampicillin/sulbactam.

OUTCOMES

The pneumonia became fulminant. Despite intensive care and treatment, he eventually died 15.5 hours after admission.

LESSONS

This is the first case of fatal fulminant CAP caused by a hvKp K2-ST86 strain reported in Japan. MLST was extremely useful for providing a definitive diagnosis for this infection. Thus, we propose that a biomarker-based approach should be considered even for an exploratory diagnosis of CAP related to hvKp infection.

Hypervirulent Klebsiella pneumoniae - clinical and molecular perspectives

Hypervirulent Klebsiella pneumoniae (hvKp) has emerged as a concerning global pathogen. hvKp is more virulent than classical K. pneumoniae (cKp) and capable of causing community-acquired infections, often in healthy individuals. hvKp is carried in the gastrointestinal tract, which contributes to its spread in the community and healthcare settings. First recognized in Asia, hvKp arose as a leading cause of pyogenic liver abscesses. In the decades since, hvKp has spread globally and causes a variety of infections. In addition to liver abscesses, hvKp is distinct from cKp in its ability to metastasize to distant sites, including most commonly the eye, lung and central nervous system (CNS). hvKp has also been implicated in primary extrahepatic infections including bacteremia, pneumonia and soft tissue infections. The genetic determinants of hypervirulence are often found on large virulence plasmids as well as chromosomal mobile genetic elements which can be used as biomarkers to distinguish hvKp from cKp clinical isolates. These distinct virulence determinants of hvKp include up to four siderophore systems for iron acquisition, increased capsule production, K1 and K2 capsule types, and the colibactin toxin. Additionally, hvKp strains demonstrate hypermucoviscosity, a phenotypic description of hvKp in laboratory conditions that has become a distinguishing feature of many hypervirulent isolates. Alarmingly, multidrug-resistant hypervirulent strains have emerged, creating a new challenge in combating this already dangerous pathogen.

Comparison between Patients with Chest Infection due to Klebsiella spp. and Streptococcus pneumoniae

Objective In Japan, the aging demographic structure is becoming pronounced, and the full-blown graying of society appears not far off, which indicates an increasing population that will require healthcare contact. Klebsiella spp. are major pathogens in healthcare-associated infections, and their importance is increasing. The aim of this study was to clarify the characteristics of Klebsiella spp. chest infections by evaluating the differences in the characteristics of chest infections caused by Klebsiella spp. and pneumoniae. Methods We conducted a retrospective study of consecutive patients hospitalized with pneumonia, lung abscess/necrotizing pneumonia, and empyema due to Klebsiella spp. and S. pneumoniae for 15 years at our institution in Saitama, Japan. Patients Patients with chest infections due to Klebsiella spp. (K group, n=76) and S. pneumoniae (S group, n=446) were included. Results The K group more frequently was male, older, coinfected by Pseudomonas aeruginosa, and had diabetes mellitus, a history of upper digestive system surgery, alcohol drinking habit, a smoking habit, and an impaired premorbid performance status than the S group. The percentages of lung abscesses or necrotizing pneumonia (31.6% vs. 0.9%) and empyema without pulmonary parenchymal shadow (3.9% vs. 0.7%) were higher in the K group than those in the S group. Severity on admission and mortality did not differ between the groups; however, patients in the K group required a longer duration of antibiotics administration and hospital stay than those in the S group. Conclusion Klebsiella spp. chest infections have some marked characteristics when compared with pneumococcal infections, and our results serve to differentiate Klebsiella spp. infection from pneumococcal infection.

Clinical and Molecular Characteristics of Klebsiella pneumoniae Isolates Causing Bloodstream Infections in Japan: Occurrence of Hypervirulent Infections in Health Care

Although hypervirulent Klebsiella pneumoniae (hvKp) has been associated with severe community-acquired infections that occur among relatively healthy individuals, information about hvKp infections in health care settings remains limited. Here, we systematically analyzed the clinical and molecular characteristics of K. pneumoniae isolates causing bloodstream infections in a cross-sectional study. Clinical characteristics of K. pneumoniae bloodstream infections from hospitals across Japan were analyzed by a review of the medical records. Whole-genome sequencing of the causative isolates was performed. Bacterial species were confirmed and hvKp were identified using whole-genome sequencing data. Clinical characteristics of hvKp infections were compared with those of non-hvKp infections by bivariate analyses. Of 140 cases of K. pneumoniae bloodstream infections, 26 cases (18.6%) were caused by various clones of hvKp defined by the carriage of cardinal virulence genes. Molecular identification revealed that 24 (17.1%) and 14 (10%) cases were caused by Klebsiella variicola and Klebsiella quasipneumoniae, respectively. Patients with hvKp infections had higher proportions of diabetes mellitus (risk ratio [RR], 1.75; 95% confidence interval [CI], 1.05 to 2.94), and their infections had significantly higher propensity to involve pneumonia (RR, 5.85; 95% CI, 1.39 to 24.6), liver abscess (RR, 5.85; 95% CI, 1.39 to 24.6), and disseminated infections (RR, 6.58; 95% CI, 1.16 to 37.4) than infections by other isolates. More than one-half of hvKp infections were health care associated or hospital acquired, and a probable event of health care-associated transmission of hvKp was documented. hvKp isolates, which are significantly associated with severe and disseminated infections, are frequently involved in health care-associated and hospital-acquired infections in Japan.

Community-acquired liver abscess caused by capsular genotype K2-ST375 hypervirulent Klebsiella pneumoniae isolates

Hypervirulent Klebsiella pneumoniae has been associated with community-acquired liver abscesses in relatively healthy subjects since the 1990s, occasionally accompanied by disseminated disease. While isolates of capsular genotype K1 belonging to sequence type (ST) 23 have been the most prominent causative pathogen of this syndrome, other virulent clones have been implicated sporadically in recent years.

A 68-year-old woman with diabetes in Okinawa, Japan suffered from a K. pneumoniae liver abscess, which recurred after a prolonged antibacterial treatment. The clinical course was further complicated with multiple sites of dissemination. Another 45-year-old woman living in Okinawa without underlying conditions was also diagnosed with a community-acquired K. pneumoniae liver abscess, which was cured with antibacterial treatment alone. Both of the causative isolates carried rmpA and aerobactin genes, and were confirmed as capsular genotype K2 and ST375.

K. pneumoniae K2-ST375 is a hypervirulent clone of epidemiological significance causing severe community-acquired infections in relatively healthy subjects. More information about clinical characteristics and molecular epidemiology of hypervirulent K. pneumoniae clones other than K1-ST23 should be accumulated.

Hypervirulent Klebsiella pneumoniae: a Call for Consensus Definition and International Collaboration

Hypervirulent Klebsiella pneumoniae strains have higher potential to cause more severe and disseminated infections than classic K. pneumoniae strains. While initially reported from East Asian countries, cases have now been identified worldwide, sometimes in conjunction with extensive drug resistance. In this issue of the Journal of Clinical Microbiology, T. A. Russo et al. (J Clin Microbiol 56:e00776-18, 2018, https://doi.org/10.1128/JCM.00776-18) validated the diagnostic accuracy of biomarkers that differentiate hypervirulent K. pneumoniae strains from classic strains. This represents a major step forward in building a consensus definition and designing international studies aimed at elucidating the global epidemiology, clinical features, and outcome of this important pathogen.

KPC-producing Klebsiella pneumoniae bloodstream isolates from Brazilian hospitals: What (still) remains active?

OBJECTIVES

This study assessed susceptibility to polymyxin B (PMB) and alternative antimicrobials, with focus on aminoglycosides and tigecycline, according to different breakpoints in KPC-producing Klebsiella pneumoniae (KPC-Kp) bloodstream isolates from Brazilian hospitals.

METHODS

Bloodstream K. pneumoniae isolates non-susceptible to any of the three carbapenems (meropenem, imipenem or ertapenem) from four Brazilian tertiary-care hospitals were selected. Antimicrobial susceptibility was determined and interpreted according to distinct breakpoints. Twenty-nine PMB-resistant KPC-Kp isolates were selected for molecular typing.

RESULTS

A total of 158 KPC-Kp were analysed. MIC_50/90 values for PMB were 0.25/16mg/L; 40 isolates (25.3%) were resistant to PMB. MIC_50/90 values for meropenem were 32/≥256mg/L; no isolates were susceptible to meropenem according to CLSI, but 10 isolates were intermediate using EUCAST breakpoints (1, MIC=4mg/L; 9, MIC=8mg/L). MIC_50/90 values for tigecycline were 2/8mg/L; 53 (33.5%) and 94 (59.5%) isolates were susceptible according to EUCAST and FDA breakpoints, respectively. MIC_50/90 values were 32/≥64mg/L for amikacin and ≥16/≥16mg/L for gentamicin; 48 (30.4%), 28 (17.7%) and 16 (10.1%) were susceptible to amikacin according to CLSI, EUCAST and USCAST, respectively, but susceptibility rates to gentamicin were <7.0%. Eighteen distinct clonal profiles were identified among 29 PMB-resistant isolates by DNA macrorestriction. Most clones belonged to CC11.

CONCLUSION

Elevated rates of PMB-resistant KPC-Kp bloodstream infections were found in four Brazilian hospitals, mostly of polyclonal origin. Alternative antimicrobials with the highest in vitro activity were tigecycline and amikacin, although susceptibility rates significantly decreased using criteria with stricter breakpoints (e.g. EUCAST, USCAST).