First report of two rapid-onset fatal infections caused by a newly emerging hypervirulent K. Pneumonia ST86 strain of serotype K2 in China

Identification of hypermucoviscous Klebsiella pneumoniae K1, K2, K54 and K57 capsular serotypes by Raman spectroscopy

Antimicrobial resistance poses a significant challenge in modern medicine, affecting public health. Klebsiella pneumoniae infections compound this issue due to their broad range of infections and the emergence of multiple antibiotic resistance mechanisms. Efficient detection of its capsular serotypes is crucial for immediate patient treatment, epidemiological tracking and outbreak containment. Current methods have limitations that can delay interventions and increase the risk of morbidity and mortality. Raman spectroscopy is a promising alternative to identify capsular serotypes in hypermucoviscous K. pneumoniae isolates. It provides rapid and in situ measurements with minimal sample preparation. Moreover, its combination with machine learning tools demonstrates high accuracy and reproducibility. This study analyzed the viability of combining Raman spectroscopy with one-dimensional convolutional neural networks (1-D CNN) to classify four capsular serotypes of hypermucoviscous K. pneumoniae: K1, K2, K54 and K57. Our approach involved identifying the most relevant Raman features for classification to prevent overfitting in the training models. Simplifying the dataset to essential information maintains accuracy and reduces computational costs and training time. Capsular serotypes were classified with 96 % accuracy using less than 30 Raman features out of 2400 contained in each spectrum. To validate our methodology, we expanded the dataset to include both hypermucoviscous and non-mucoid isolates and distinguished between them. This resulted in an accuracy rate of 94 %. The results obtained have significant potential for practical healthcare applications, especially for enabling the prompt prescription of the appropriate antibiotic treatment against infections.

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

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

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.

Phenotypic and genetic characterization of hypervirulent Klebsiella pneumoniae in patients with liver abscess and ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) and pyogenic liver abscess (PLA) due to Klebsiella pneumoniae infection can trigger life-threatening malignant consequences, however, there are few studies on the strain-associated clinical pathogenic mechanisms between VAP and PLA. A total of 266 patients consist of 129 VAP and 137 PLA were included for analysis in this study. We conducted a comprehensive survey for the two groups of K. pneumoniae isolates, including phenotypic experiments, clinical epidemiology, genomic analysis, and instrumental analysis, i.e., to obtain the genomic differential profile of K. pneumoniae strains responsible for two distinct infection outcomes. We found that PLA group had a propensity for specific underlying diseases, especially diabetes and cholelithiasis. The resistance level of VAP was significantly higher than that of PLA (78.57% vs. 36%, P < 0.001), while the virulence results were opposite. There were also some differences in key signaling pathways of biochemical processes between the two groups. The combination of iucA, rmpA, hypermucoviscous phenotype, and ST23 presented in K. pneumoniae infection is more important and highly prudent for timely treatment. The present study may contribute a benchmark for the K. pneumoniae clinical screening, epidemiological surveillance, and effective therapeutic strategies.

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

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

Characterization and Functional Studies of a Novel Depolymerase Against K19-Type Klebsiella pneumoniae

Carbapenem-resistant Klebsiella pneumoniae (CRKP), a pathogen that causes severe nosocomial infections and yields a high mortality rate, poses a serious threat to global public health due to its high antimicrobial resistance. Bacteriophages encode polysaccharide-degrading enzymes referred to as depolymerases that cleave the capsular polysaccharide (CPS), one of the main virulence factors of K. pneumoniae. In this study, we identified and characterized a new capsule depolymerase K19-Dpo41 from K. pneumoniae bacteriophage SH-KP156570. Our characterization of K19-Dpo41 demonstrated that this depolymerase showed specific activities against K19-type K. pneumoniae. K19-Dpo41-mediated treatments promoted the sensitivity of a multidrug-resistant K19-type K. pneumoniae strain to the bactericidal effect of human serum and significantly increased the survival rate of Galleria mellonella infected with K19-type K. pneumoniae. Our results provided strong primary evidence that K19-Dpo41 was not only effective in capsular typing of K19-type K. pneumoniae but promising in terms of developing new alternative therapeutic strategies against K19-type CRKP infections in the future.

Analysis of hypervirulent Klebsiella pneumoniae and classic Klebsiella pneumoniae infections in a Chinese hospital

Aims

To evaluate the clinical and genetic virulence characteristics of critically ill patients with hypervirulent Klebsiella pneumoniae (hvKP) and classic KP (cKP) infection.

Methods and Results

The patients included in this retrospective study (n = 225) were grouped according to their hvKP (n = 114) or cKP (n = 111) status, and their clinical characteristics were analysed and compared. Cox multivariate analysis was conducted to determine the risk factors for hvKP infection. Length of hospital stay, length of intensive care unit stay, duration of mechanical ventilation and 28‐day survival rate were similar between the groups. However, the incidence of septic shock was higher in the hvKP group (16.7%) than in the cKP group (8.1%).

Conclusions

There was a high rate of hvKP infection in this population. Compared to patients with cKP infection, those with hvKP infection showed a higher probability of having septic shock; nevertheless, survival and length of hospital stay were similar between the groups. Risk factors for hvKP infection included hospital‐acquired infection and renal insufficiency.

Significance and Impact of the Study

This study presents relevant information on the characteristics of hvKP infection in a Chinese population, and this promotes early diagnosis and supports the view that the prevalence of hvKP is high in China.

Genomic Features and Virulence Characteristics of a Community-Acquired Bloodstream Infection-Causing Hypervirulent Klebsiella pneumoniae ST86 Strain Harboring KPC-2-Encoding IncX6 Plasmid

The emergence and spread of carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) is causing worldwide concern. Sequence type (ST) 86 K. pneumoniae, a major hvKP clone, is rarely resistant to carbapenem. In this study, we report the genomic features and virulence characteristics of a community-acquired bloodstream infection (CA-BSI)-causing CR-hvKP ST86 strain (KPN55602). This strain is resistant to carbapenem but sensitive to amikacin, gentamicin, tigecycline, and colistin. According to in vitro and in vivo virulence assessments, it was classified as hypervirulent. Whole-genome sequencing revealed that KPN55602 has a single 5.13 Mb chromosome and two plasmids. The chromosome of KPN55602 is phylogenetically similar to those of other sequenced ST86 strains. The incompatibility (Inc) group HI1B plasmid pK55602_1, harboring a set of virulence genes, was classified as a virulence plasmid. The IncX6 plasmid pK55602_2, carrying bla_KPC-2, was transferable through conjugation and is highly homologous to all five sequenced bla_KPC-bearing IncX6 plasmids. In conclusion, to our knowledge, this is the first report of a CA-BSI-causing CR-hvKP ST86 strain harboring an exogenous bla_KPC-2-bearing IncX6 plasmid, supplementing existing knowledge on the CR-hvKP evolutionary scenario. The IncX6 plasmid may be an important vehicle for bla_KPC, and its horizontal transfer may have led to CR-hvKP evolution in the community setting.

The First Case of Community-Acquired Pneumonia Due to Capsular Genotype K2-ST86 Hypervirulent Klebsiella pneumoniae in Okinawa, Japan: A Case Report and Literature Review

Hypervirulent Klebsiella pneumoniae (HV-KP) typically causes pyogenic liver abscess and bacteremia with metastatic infections. Community-acquired pneumonia (CAP) due to HV-KP is uncommon and details of its clinical and microbiological features are limited. We report the first case of CAP due to capsular genotype K2-ST86 HV-KP in Okinawa, Japan and review infections caused by the K2-ST86 strain. A 79-year-old woman presenting with fever and productive cough persisting for the past three days was admitted to hospital. Her vital signs indicated septic shock. Lung examination by auscultation revealed holo-crackle and lobar pneumonia in chest radiography, and Streptococcus pneumoniae was suspected. However, sputum and blood cultures revealed Gram-negative coccus identified as K. pneumoniae. Genetic analysis identified the isolated strain as the K2 serotype harboring rmpA, iutA, entB, and mrkD. Therefore, we identified the isolated strain as hypervirulent. The isolate belonged to ST86 as determined by multilocus sequence typing. The case was not complicated by predisposing factors such as diabetes mellitus and malignancy related to HV-KP infection; thus, this CAP-causing HV-KP strain may differ from the typical HV-KP strain that induces liver abscess. A literature review identified only nine cases with CAP due to HV-KP. In all cases, the disease mainly occurred in older males with diabetes mellitus, which makes the present case unusual, and had high rates of septic shock and death. No case, including ours, was complicated by metastatic infection, suggesting that CAP due to HV-KP poses little distant metastasis risk, even in patients with bloodstream infection. In our review, consistent with our case, K2-ST86 was the most common strain of HV-KP in patients with CAP. Therefore, studies are needed to elucidate the clinical and microbiological features of HV-KP CAP, with a focus on the K2-ST86 strain. Physicians should always consider K. pneumoniae in cases of sepsis CAP with lobar pneumonia.

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.

An Outbreak of Carbapenem-Resistant and Hypervirulent Klebsiella pneumoniae in an Intensive Care Unit of a Major Teaching Hospital in Wenzhou, China

Carbapenem-resistant, hypervirulent Klebsiella pneumoniae (CR-hvKP) has recently emerged as a significant threat to public health. In this study, 29 K. pneumoniae isolates were isolated from eight patients admitted to the intensive care unit (ICU) of a comprehensive teaching hospital located in China from March 2017 to January 2018. Clinical information of patients was the basis for the further analyses of the isolates including antimicrobial susceptibility tests, identification of antibiotic resistance and virulence gene determinants, multilocus sequence typing (MLST), XbaI-macrorestriction by pulsed-field gel electrophoresis (PFGE). Selected isolates representing distinct resistance profiles and virulence phenotypes were screened for hypervirulence in a Galleria mellonella larvae infection model. In the course of the outbreak, the overall mortality rate of patients was 100% (n = 8) attributed to complications arising from CR-hvKP infections. All isolates except one (28/29, 96.6%) were resistant to multiple antimicrobial agents, and harbored diverse resistance determinants that included the globally prevalent carbapenemase bla_KPC−2. Most isolates had hypervirulent genotypes being positive for 19 virulence-associated genes, including iutA (25/29, 86.2%), rmpA (27/29, 93.1%), ybtA (27/29, 93.1%), entB (29/29, 100%), fimH (29/29, 100%), and mrkD (29/29, 100%). MLST revealed ST11 for the majority of isolates (26/29, 89,7%). Infection assays demonstrated high mortality in the Galleria mellonella model with the highest LD₅₀ values for three isolates (<10⁵ CFU/mL) demonstrating the degree of hypervirulence of these CR-hvKP isolates, and is discussed relative to previous outbreaks of CR-hvKP.

Two Hypervirulent Klebsiella pneumoniae Isolates Producing a bla KPC-2 Carbapenemase from a Canadian Patient

This report describes two hypervirulent Klebsiella pneumoniae isolates that produced K. pneumoniae carbapenemase (KPC), which were identified from a rectal swab and a urine culture upon hospital admission. The patient had recently traveled to Greece, where he was hospitalized. The isolates were sequence type 86 and contained an IncHI1B IncFIB_K hypervirulent plasmid and an IncFII_K plasmid harboring KPC.

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.

Molecular epidemiology of Klebsiella pneumoniae K1 and K2 isolates in Japan

Although severe infections caused by hypervirulent Klebsiella pneumoniae isolates, such as K1 isolates belonging to sequence type (ST) 23, have been a significant problem in Asian countries, epidemiology of these isolates in Japan remains unclear. We performed a nationwide molecular epidemiological study of K. pneumoniae K1 and K2 isolates in Japan. Of the 259K. pneumoniae isolates collected, 14 and 16 isolates were identified as capsular genotypes K1 and K2, respectively. All K1 isolates were ST23 or its closely related clones and showed high genetic similarity by pulsed-field gel electrophoresis (PFGE) and the DiversiLab system (DL). K2 isolates, belonging to ST14, ST25, ST65, ST86, and ST110, were more genetically diverse than K1 isolates. Isolates belonging to a specific ST showed identical virulence gene profiles with a few exceptions. PFGE and DL results using K1 and K2 isolates were generally in agreement.

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

Since the hypermucoviscous variants of Klebsiella pneumoniae were first reported, many cases of primary liver abscesses and other invasive infections caused by this pathogen have been described worldwide. Hypermucoviscosity is a phenotypic feature characterized by the formation of a viscous filament ≥5 mm when a bacterial colony is stretched by a bacteriological loop; this is the so-called positive string test. Hypermucoviscosity appears to be associated with this unusual and aggressive type of infection, and therefore, the causal strains are considered hypervirulent. Since these first reports, the terms hypermucoviscosity and hypervirulence have often been used synonymously. However, new evidence has suggested that hypermucoviscosity and hypervirulence are 2 different phenotypes that should not be used synonymously. Moreover, it is important to establish that a negative string test is insufficient in determining whether a strain is or is not hypervirulent. On the other hand, hypervirulence- and hypermucoviscosity-associated genes must be identified, considering that these phenotypes correspond to 2 different phenomena, regardless of whether they can act in synergy under certain circumstances. Therefore, it is essential to quickly identify the genetic determinants behind the hypervirulent phenotype to develop effective methodologies that can diagnose in a prompt and effective way these hypervirulent variants of K. pneumoniae.

First report of invasive liver abscess syndrome with endophthalmitis caused by a K2 serotype ST2398 hypervirulent Klebsiella pneumoniae in Germany, 2016

We report a case of severe infection with liver abscess and endophthalmitis caused by a hypervirulent Klebsiella pneumoniae strain in an immunocompetent German male patient without travel history to Asia. Phenotypic and molecular characterization showed high similarity to the reference genome NTUH-K2044 isolated in Asia. The isolate was assigned as ST2398 (clonal complex 66). The findings underline global spread of hypervirulent Klebsiella pneumoniae strains to Europe.

Peracute Bacterial Meningitis due to Infection with Klebsiella pneumoniae in Captive-bred Ruffed Lemurs (Varecia variegate)

We describe the development of neurological signs in four juvenile black-and-white ruffed lemurs (Varecia variegate), housed at a petting zoo in Japan. The clinical course was severe, with three lemurs dying within 1 day of the appearance of clinical signs. The other lemur was treated and survived. Pathological analyses demonstrated meningitis and the presence of gram-negative bacilli in the cerebrum, cerebellum, palatine tonsil and liver. Klebsiella pneumoniae was isolated from the brain of all of the dead lemurs. Multilocus sequence typing analysis showed that all the isolates were sequence type 86 (ST86). To our knowledge, this is the first determination of K. pneumoniae infection in ruffed lemurs of this genus. K. pneumoniae infection may represent a risk to lemurs and people who come into contact with infected animals.