The molecular characteristics, clinical manifestations, 44 and risk factors of hypervirulent Klebsiella pneumoniae infections in a large teaching hospital in southwest China

Prevalence, Risk Factors, and Clinical Outcomes of Hypervirulent Klebsiella pneumoniae Strains among Klebsiella pneumoniae Infections: A Systematic Review and Meta-analysis

Aim and background

Hypervirulent Klebsiella pneumoniae (HvKp) is a virulent strain associated with invasive infections. While initially community-acquired, hospital-acquired HvKp (HA-HvKp) and carbapenem-resistant HvKp (CR-HvKp) are increasingly reported. This meta-analysis evaluates the prevalence, risk factors, and clinical outcomes associated with HvKp, including CR-HvKp and HA-HvKp, among Kp infections.

Methodology

A systematic search of PubMed, Scopus, Embase, and Cochrane Library was conducted until December 2024. Observational studies comparing HvKp vs classical Kp (cKp), CR-HvKp vs carbapenem-sensitive HvKp (CS-HvKp), and HA-HvKp vs community-acquired HvKp (CA-HvKp) were included. Quality was assessed using the Joanna Briggs Critical Appraisal Tool, and pooled prevalence and odds ratios (ORs) with 95% confidence intervals (CIs) were calculated.

Results

Fifty studies with 6,663 participants were included. The HvKp prevalence was 33.0%, with most studies from Asia, predominantly China. Temporal analysis revealed an increase in HvKp prevalence (27.7% in 2006-2018 to 38.5% in 2019-2024). The CR-HvKp prevalence rose from 9.5% to 16.5% (2016-2024). The HA-HvKp prevalence increased from 25.9 to 47.1%. Key risk factors included diabetes mellitus (OR = 1.56), CA-Kp (OR = 2.59), and hypermucoviscous (HM)-phenotype (OR = 29.79). Complications included liver abscess (OR = 6.35), metastatic spread (OR = 4.74), meningitis (OR = 11.14), and septic shock (OR = 1.30). Mortality was higher in HvKp infections but not statistically significant (p = 0.219). HA-HvKp and immunosuppression were significant CR-HvKp risk factors, with CR-HvKp showing higher mortality.

Conclusions

Diabetes mellitus, CA-Kp infections, and HM-phenotype are significant risk factors for HvKp. The rising prevalence of CR-HvKp and HA-HvKp highlights the need for early detection, infection control, and targeted treatment strategies.

How to cite this article

Nagendra D, Chaudhuri S, Gupta N, Shanbhag V, Eshwara VK, Rao S, et al. Prevalence, Risk Factors, and Clinical Outcomes of Hypervirulent Klebsiella pneumoniae Strains among Klebsiella pneumoniae Infections: A Systematic Review and Meta-analysis. Indian J Crit Care Med 2025;29(4):370-393.

Phenotypic and Genotypic Detection of Hypervirulent Klebsiella pneumoniae Isolated from Hospital-Acquired Infections

Hypervirulent Klebsiella pneumoniae is a highly pathogenic variant of Klebsiella pneumonae, which represents a global public health issue because it is very virulent and spreads easily. The objectives of this study were to assess the predominance of hvKp among health care-associated infections in intensive care units of Tanta University Hospital and to compare hvKp with classical K. pneumoniae (cKp) in terms of antibiotic resistance, virulence, and molecular features. The study included 300 patients suffering from HAIs from different ICUs of Tanta University Hospitals. K. pneumoniae isolates were identified and subjected to string testing and antibiotic susceptibility testing, and the tissue culture assay for biofilm formation and polymerase chain reaction (PCR) tests were performed for the identification of capsular genes (K1, K2, K57) and virulence genes (rmpA, rmpA2, iuc A). Fifty-seven K. pneumonaie isolates were isolated. A total of 21 (36.8%) of them were hvKp and 36 (63.15%) were cKp. Significantly higher antibiotic resistance was detected in the cKp group. There was a significant difference between biofilm formation between cKp and hvKp isolates (p < 0.004*). iucA, rmpA2, and K1 genes were significantly associated with hvKp. The string test shows 100% sensitivity and negative predictive value for the detection of hvKp. Consequently, using the string test alone for the screening of hvKp is required. However, combining aerobactin-positive with hypermucoviscous isolates while screening for hvKp is crucial.

Bio inspired microfluidic-based analysis of Klebsiella pneumoniae virulence factors and antimicrobial resistance

The objective of this research was to examine the antibiotic resistance and microbiological traits of Klebsiella pneumoniae isolates that were responsible for liver abscesses in Qingdao, China. Between April and September 2022, isolates were taken from 120 patients at three tertiary hospitals. Rapid detection of capsule serotypes (K1, K2) and virulence genes (rmpA, aerobactin) was achieved by using microfluidic-based techniques. Testing for antimicrobial susceptibility was done with the VITEK 2 Compact system. The findings showed that there was a high frequency of extremely virulent K. pneumoniae strains, which are often linked to bacteremia and higher death rates. These strains belonged to the K1 and K2 serotypes and were primarily carrying the aerobactin and rmpA genes. The majority of isolates were antibiotic-sensitive, but the emergence of resistant strains emphasizes the necessity of continuing surveillance. The efficiency of microfluidic platforms for the quick and precise characterization of K. pneumoniae is demonstrated in this work, enabling prompt clinical interventions.

Genotypic characterization of hypervirulent Klebsiella pneumoniae (hvKp) in a tertiary care Indian hospital

Hypervirulent Klebsiella pneumoniae (hvKp) is an emerging pathogen and causes endophthalmitis, liver abscess, osteomyelitis, meningitis, and necrotizing soft tissue infections in both immunodeficient and healthy people. The acquisition of the antibiotic resistance genes of hvKp has become an emerging concern throughout the globe. In this study, a total of 74 K. pneumoniae isolates were collected and identified by VITEK2 and blaSHV gene amplification. Out of these, 18.91% (14/74) isolates were identified as hvKp by both phenotypic string test and genotypic iucA PCR amplification. The antibiotic susceptibility revealed that 57.14% (8/14) isolates were multidrug-resistant (MDR) and 35.71% (5/14) isolates were extremely drug-resistant (XDR). All the isolates were resistant to β-lactam, β-lactamase + inhibitor groups of antibiotics, and the least resistance to colistin. Of 14 hvKp isolates, all isolates are positive for iroB (100%), followed by iutA (92.85%), peg344 (85.71%), rmpA (57.14%), and magA (21.42%) genes. Among serotypes, K1 was the most prevalent serotype 21.4% (3/14), followed by K5 14.3% (2/14). The most common carbapenemase gene was blaOXA-48 (78.57%) followed by blaNDM (14.28%) and blaKPC (14.28%) which co-carried multiple resistance genes such as blaSHV (100%), blaCTX-M (92.85%), and blaTEM (78.57%). About 92.85% (13/14) of hvKp isolates were strong biofilm producers, while one isolate (hvKp 10) was the only moderate biofilm producer. The (GTG)5-PCR molecular typing method revealed high diversity among the hvKp isolates in the tertiary care hospital. Our findings suggest that MDR-hvKp is an emerging pathogen and a challenge for clinical practice. In order to avoid hvKp strain outbreaks in hospital settings, robust infection control and effective surveillance should be implemented.

Risk Factors, Outcomes, and Predictions of Extensively Drug-Resistant Acinetobacter baumannii Nosocomial Infections in Patients with Nervous System Diseases

Purpose

Acinetobacter baumannii has evolved to become a major pathogen of nosocomial infections, resulting in increased morbidity and mortality. This study aimed to investigate the risk factors, outcomes, and predictions of extensively drug-resistant (XDR)-A. baumannii nosocomial infections in patients with nervous system diseases (NSDs).

Methods

A retrospective study of patients infected with XDR-A. baumannii admitted to the Affiliated Hospital of Southwest Medical University (Luzhou, China) from January 2021 to December 2022 was conducted. Three multivariate regression models were used to assess the risk factors and predictive value for specific diagnostic and prognostic subgroups.

Results

A total of 190 patients were included, of which 84 were diagnosed with NSDs and 80% of those were due to stroke. The overall rates of all-cause mortality for XDR-A. baumannii nosocomial infections and those in NSDs were 38.9% and 40.5%, respectively. Firstly, hypertension, indwelling gastric tube, tracheotomy, deep puncture, bladder irrigation, and pulmonary infections were independent risk factors for XDR-A. baumannii nosocomial infections in patients with NSDs. Moreover, pulmonary infections, the aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio, and the neutrophil-to-lymphocyte ratio (NLR) were significantly associated with increased mortality rates in patients with nosocomial infections caused by XDR-A. baumannii. Thirdly, NLR and cardiovascular diseases accounted for a high risk of mortality for XDR-A. baumannii nosocomial infections in patients with NSDs. The area under the curves of results from each multivariate regression model were 0.827, 0.811, and 0.853, respectively.

Conclusion

This study reveals the risk factors of XDR-A. baumannii nosocomial infections in patients with NSDs, and proves their reliable predictive value. Early recognition of patients at high risk, sterilizing medical tools, and regular blood monitoring are all critical aspects for minimizing the nosocomial spread and mortality of A. baumannii infections.

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.

Predictors of hypervirulent Klebsiella pneumoniae infections: a systematic review and meta-analysis

BACKGROUND

Hypervirulent Klebsiella pneumoniae (hvKp) infections confer notable morbidity and mortality. Differential diagnosis to determine whether the infections are caused by either the hvKp or classical K. pneumoniae (cKp) strain is particularly important for undertaking optimal clinical care and infection control efforts.

AIM

To identify and assess the potential predictors of hvKp infections.

METHODS

PubMed, Web of Science, and Cochrane Library databases were searched for all relevant publications from January 2000 to March 2022. The search terms included a combination of the following terms: (i) Klebsiella pneumoniae or K. pneumoniae and (ii) hypervirulent or hypervirulence. A meta-analysis of factors for which risk ratio was reported in three or more studies was conducted, and at least one statistically significant association was identified.

FINDINGS

In this systematic review of 11 observational studies, a total of 1392 patients with K. pneumoniae infection and 596 (42.8%) with hvKp strains were evaluated. In the meta-analysis, diabetes mellitus and liver abscess (pooled risk ratio: 2.61 (95% confidence interval: 1.79-3.80) and 9.04 (2.58-31.72), respectively; all P < 0.001) were predictors of hvKp infections.

CONCLUSION

For patients with a history of the abovementioned predictors, prudent management, including the search for multiple sites of infection and/or metastatic spread and the enforcement of an early and appropriate source control procedure, should be initiated in consideration of the potential presence of hvKp. We believe that this research highlights the urgent need for increasing clinical awareness of the management of hvKp infections.

MDR carbapenemase-producing Klebsiella pneumoniae of the hypervirulence-associated ST23 clone in Poland, 2009-19

OBJECTIVES

To characterize carbapenemase-producing isolates of the Klebsiella pneumoniae hypervirulent (hvKp) clone ST23 in Poland.

METHODS

Fifteen K. pneumoniae ST23 isolates were identified by the Polish surveillance of carbapenemase-producing Enterobacterales. These comprised a cluster with KPC-2 + NDM-1 (n = 7), KPC-2 (n = 1) or NDM-1 (n = 1) enzymes from one hospital from 2018, and sporadic isolates with KPC-2 (n = 1), NDM-1 (n = 1), VIM-1 (n = 1) or OXA-48 (n = 3), recovered from 2009 to 2019 in different towns. The isolates were sequenced by Illumina MiSeq, followed by MinION for six representatives. Clonality, phylogeny, serotypes, virulomes, resistomes and plasmids of the isolates were analysed and compared with international ST23 strains, using various bioinformatic tools.

RESULTS

Only two diverse isolates with KPC-2 or VIM-1 were of typical hvKp ST23 serotypes K1 and O1v.2, and its predominant phylogenetic clade. These contained multiple chromosomal (ybt, clb) and pK2044/KpVP-1 plasmid (iuc, iro, rmpADC, rmpA2) virulence loci, whereas carbapenemase and other antimicrobial resistance (AMR) genes were on single additional plasmids. All remaining isolates were of K57 and O2v.2 serotypes, and a minor, distant clade of unclear phylogeny, including also ∼10 isolates from other European countries. These had fewer virulence loci (ybt, iuc, rmpADC, rmpA2) but abounded in plasmids, which with several chromosomal AMR mutations conferred more extensive MDR phenotypes than in K1 O1v.2. Lower clonal diversity than in K1, and numerous common characteristics of the isolates supported the hypothesis of the emerging character of the ST23 K57 clade.

CONCLUSIONS

A new MDR ST23 lineage has emerged in Europe, causing a potential threat to public health.

Successful treatment of acute respiratory distress syndrome caused by hypervirulent Klebsiella pneumoniae with extracorporeal membrane oxygenation and continuous renal replacement therapy: A case report and literature review

Hypervirulent Klebsiella pneumoniae (hvKP) causes invasive infections and leads to high morbidity and mortality rates. Here, we report the case of a Chinese man with diabetes mellitus who developed acute respiratory distress syndrome and septic shock due to hvKP belonging to the K1 strain. The patient was treated with venovenous extracorporeal membrane oxygenation and continuous renal replacement therapy, in combination with antibiotics and recovered well. Clinicians should be aware of fatal infections caused by hvKP and investigate the best treatment options for patients at various stages of infection.

Phenotypic and Genotypic Characteristics of a Tigecycline-Resistant Acinetobacter pittii Isolate Carrying bla NDM-1 and the Novel bla OXA Allelic Variant bla OXA-1045

A tigecycline-resistant Acinetobacter pittii clinical strain from pleural fluid carrying a bla_NDM–1 gene and a novel bla_OXA gene, bla_OXA–1045, was isolated and characterized. The AP2044 strain acquired two copies of the bla_NDM–1 gene and six antibiotic resistance genes (ARGs) from other pathogens. According to the whole-genome investigation, the GC ratios of ARGs (50–60%) were greater than those of the chromosomal backbone (39.46%), indicating that ARGs were horizontally transferred. OXA-1045 belonged to the OXA-213 subfamily and the amino acid sequence of OXA-1045 showed 89% similarity to the amino acid sequences of OXA-213. Then, bla_OXA–1045 and bla_OXA–213 were cloned and the minimum inhibitory concentrations (MICs) of β-lactams in the transformants were determined using the broth microdilution method. OXA-1045 was able to confer a reduced susceptibility to piperacillin and piperacillin-tazobactam compared to OXA-213. AP2044 strain exhibited low pathogenicity in Galleria mellonella infection models. The observation of condensed biofilm using the crystal violet staining method and scanning electron microscopy (SEM) suggested that the AP2044 strain was a weak biofilm producer. Quantitative reverse transcription-PCR (qRT-PCR) was used to detect the expression of resistance-nodulation-cell division (RND) efflux pump-related genes. The transcription level of adeB and adeJ genes increased significantly and was correlated with tigecycline resistance. Therefore, our genomic and phenotypic investigations revealed that the AP2044 strain had significant genome plasticity and natural transformation potential, and the emergence of antibiotic resistance in these unusual bacteria should be a concern for future investigations.