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.Electronic supplementary materialThe online version of this article (10.1186/s12941-018-0302-9) contains supplementary material, which is available to authorized users.

Objectives Hypervirulent Klebsiella pneumoniae(hvKp) is an increasingly important pathogen. Tracking its epidemiology and evolving antimicrobial resistance will facilitate care. Methods A retrospective study was conducted in two hospitals. We collected the clinical data. Antimicrobial and virulence-associated phenotype and genotype, sequence type, and whole genome sequencing of selected strains were performed. HvKp was defined by the presence of some combination of p rmpA, p rmpA2, iucA, iroB, and peg-344, genes shown to accurately identify hvKp. Results Of 158 Kp clinical isolates, 79 (50%) were hvKp. Interestingly, 53/79 (67.1%) of hvKp strains were isolated from patients with nosocomial infection and 19/79 (24.1%) from patients with healthcare-associated infection, but only 7/79 (8.8%) from patients with community-acquired infections. Importantly, 27/53 (50.9%) and 4/19 (21.1%) of hvKp nosocomial and healthcare-associated isolates, respectively, were multi-drug-resistant (MDR); 25/53 (47.2%) and 5/19 (26.3%) expressed ESBLs and 14/53 (26.4%) and 2/19 (10.5%) were carbapenem-resistant. Of the hvKp isolates from community-acquired infection, 0/7 (0%) were MDR and 0/7 (0%) were carbapenem-resistant. Additionally, unique characteristics of nosocomial, healthcare-associated, and community-acquired hvKp infection were identified. In summary, 50% of K. pneumoniae infections were caused by hvKp. A concerning, novel finding from this report is a major shift in hvKp epidemiology. Ninety-one percent of hvKp infections were nosocomial or healthcare-associated, and 43.1% of these isolates were MDR. Conclusions These data suggest that hvKp may be replacing classical K. pneumoniae as the dominant nosocomial and healthcare-associated pathotype. Ongoing surveillance is needed to determine if this trend is occurring elsewhere.

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.

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.

Hypervirulent Klebsiella pneumoniae (hvKp) has become the dominant pathotype in hospitals recently. The sequence type (ST) 23 hvKp, which are more commonly associated with the community-acquired infections previously, may have the capacity to acquire multidrug-resistant (MDR) phenotypes creating a new “superbug” (MDR-hvKp) in hospital.

The H7N9 virus underwent dynamic evolution during infection within individual patients. Signature amino acids in PB2 and NA demonstrated high polymorphism, and signature sites related to antiviral resistance and mammalian adaption underwent dynamic variation during disease progression.

Purpose This study aimed to identify the clinical outcomes, microbiological features and risk factors for difficult-to-treat resistance (DTR) Klebsiella pneumoniae (Kp) infection. Materials and Methods A retrospective study was conducted at Peking University Third Hospital from January 2020 to March 2021. DTR was defined as resistance to ≥1 carbapenem, ≥1 extended-spectrum cephalosporin, and ≥1 fluoroquinolone. Hypervirulent Kp (HvKp) was defined as peg-344-, iroB-, iucA-, rmpA- , or rmpA2 -positive. Clinical data were collected. Antimicrobial susceptibility testing and string tests were performed to determine resistance and hypermucoviscosity phenotype. Whole genome sequencing was performed to analyze the sequence type (ST), capsular serotypes, resistance and virulence genes. Risk factors for 30-day mortality were analyzed. Results Fifty DTR-Kp (50.0%) strains were identified among 100 patients. Compared to non-DTR-Kp group, a significant number of patients with DTR-Kp infection experienced ICU admission (44.0% versus 10.0%, P<0.001) and mechanical ventilation after Kp detection (26.0% versus 10.0%, P=0.037). Notably, the percentage of hvKp among the DTR-Kp isolates increased consistently over the 15 months evaluated. Most DTR-Kp strains belonged to ST11 (82.0%), followed by ST15 (12.0%), ST86 (2.0%), ST996 (2.0%), and ST3157 (2.0%). DTR-Kp isolates possessed various resistance genes, such as bla KPC-2 , bla TEM-1D and fosA3 (90.0%, 80.0% and 72.0%, respectively). Importantly, the yersiniabactin genes were significantly clustered in DTR group (48/50, 96.0%). The 30-day mortality was significantly higher in patients with DTR-Kp infection than non-DTR-Kp group (38.0% versus 8.2%, P=0.001). DTR-Kp infection (odds ratio [OR] = 4.196) was an independent risk factor for the 30-day mortality of Kp-infected patients. Additionally, cerebrovascular disease (OR = 2.780) and Charlson comorbidity index (OR= 1.584) were independent risk factors for DTR-Kp infections. Conclusion DTR-hvKp is rapidly emerging. The DTR-Kp strains harbored various resistance genes and high rates of yersiniabactin siderophore genes. DTR-Kp infection was an independent risk factor for mortality, suggesting that enhanced awareness essential.

Pandrug-resistant (PDR) Klebsiella pneumoniae poses a great challenge to public health, and tigecycline is an essential choice for antimicrobial treatment. In this study, we reported the emergence of PDR K. pneumoniae coharboring tmexCD1-toprJ1 , bla NDM-1 , and bla KPC-2 , which belongs to ST22 and ST3691.