Emergence of K1 ST23 and K2 ST65 hypervirulent klebsiella pneumoniae as true pathogens with specific virulence genes in cryptogenic pyogenic liver abscesses Shiraz Iran

Antibiotic resistance rates in hypervirulent Klebsiella pneumoniae strains: a systematic review and meta-analysis

OBJECTIVES

In response to the growing global concerns regarding antibiotic resistance, we conducted a meta-analysis to assess the prevalence of antibiotic resistance in hypervirulent Klebsiella pneumoniae (hvKp) strains.

METHODS

We conducted a meta-analysis of antibiotic resistance in the hvKp strains. Eligible studies published in English until April 10, 2023, were identified through a systematic search of various databases. After removing duplicates, two authors independently assessed and analyzed the relevant publications, and a third author resolved any discrepancies. Data extraction included publication details and key information on antibiotic resistance. Data synthesis employed a random-effects model to account for heterogeneity, and various statistical analyses were conducted using R and the metafor package.

RESULTS

This meta-analysis of 77 studies from 17 countries revealed the prevalence of antibiotic resistance in hvKp strains. A high resistance rates have been observed against various classes of antibiotics. Ampicillin-sulbactam faced 45.3% resistance, respectively, rendering them largely ineffective. The first-generation cephalosporin cefazolin exhibited a resistance rate of 38.1%, whereas second-generation cefuroxime displayed 26.7% resistance. Third-generation cephalosporins, cefotaxime (65.8%) and ceftazidime (57.1%), and fourth-generation cephalosporins, cefepime (51.3%), showed substantial resistance. The last-resort carbapenems, imipenem (45.7%), meropenem (51.0%), and ertapenem (40.6%), were not spared. Conclusion CONCLUSION: This study emphasizes the growing issue of antibiotic resistance in hvKp strains, with notable resistance to both older and newer antibiotics, increasing resistance over time, regional disparities, and methodological variations. Effective responses should involve international cooperation, standardized testing, and tailored regional interventions.

A challenging case of carbapenem resistant Klebsiella pneumoniae-related pyogenic liver abscess with capsular polysaccharide hyperproduction: a case report

BACKGROUND

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections are a major public health problem, necessitating the administration of polymyxin E (colistin) as a last-line antibiotic. Meanwhile, the mortality rate associated with colistin-resistant K. pneumoniae infections is seriously increasing. On the other hand, importance of administration of carbapenems in promoting colistin resistance in K. pneumoniae is unknown.

CASE PRESENTATION

We report a case of K. pneumoniae-related pyogenic liver abscess in which susceptible K. pneumoniae transformed into carbapenem- and colistin-resistant K. pneumoniae during treatment with imipenem. The case of pyogenic liver abscess was a 50-year-old man with diabetes and liver transplant who was admitted to Abu Ali Sina Hospital in Shiraz. The K. pneumoniae isolate responsible for community-acquired pyogenic liver abscess was isolated and identified. The K. pneumoniae isolate was sensitive to all tested antibiotics except ampicillin in the antimicrobial susceptibility test and was identified as a non-K1/K2 classical K. pneumoniae (cKp) strain. Multilocus sequence typing (MLST) identified the isolate as sequence type 54 (ST54). Based on the patient's request, he was discharged to continue treatment at another center. After two months, he was readmitted due to fever and progressive constitutional symptoms. During treatment with imipenem, the strain acquired blaOXA-48 and showed resistance to carbapenems and was identified as a multidrug resistant (MDR) strain. The minimum inhibitory concentration (MIC) test for colistin was performed by broth microdilution method and the strain was sensitive to colistin (MIC < 2 µg/mL). Meanwhile, on blood agar, the colonies had a sticky consistency and adhered to the culture medium (sticky mucoviscous colonies). Quantitative real-time PCR and biofilm formation assay revealed that the CRKP strain increased capsule wzi gene expression and produced slime in response to imipenem. Finally, K. pneumoniae-related pyogenic liver abscess with resistance to a wide range of antibiotics, including the last-line antibiotics colistin and tigecycline, led to sepsis and death.

CONCLUSIONS

Based on this information, can we have a theoretical hypothesis that imipenem is a promoter of resistance to carbapenems and colistin in K. pneumoniae? This needs more attention.

Infection with Carbapenem-resistant Hypervirulent Klebsiella Pneumoniae: clinical, virulence and molecular epidemiological characteristics

BACKGROUND

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) is gradually becoming the dominant nosocomial pathogens in the healthcare setting.

METHODS

A retrospective study was conducted on patients with CR-KP from July 2021 to May 2022 in a teaching hospital. We identified bacterial isolates, collected the clinical data, and performed antimicrobial susceptibility testing, hypermucoviscosity string test, antimicrobial and virulence-associated genotype, as well as multi-locus sequence typing. CR-hvKP was defined as the presence of some combination of rmpA and/or rmpA2 with iucA, iroB, or peg-344. SPSS was used for data analysis. Univariate logistic regression analyses were used for risk factor and all statistically significant variables were included in the multivariate model. Statistical significance was taken to be P < 0.05.

RESULTS

A total of 69 non-duplicated CR-KP isolates were collected, 27 of which were CR-hvKP. Out of the 69 CR-KP strains under investigation, they were distributed across 14 distinct sequence types (STs), wherein ST11 exhibited the highest prevalence, constituting 65.2% (45/69) of the overall isolates. The principal carbapenemase genes identified encompassed blakpc-2, blaNDM-1, and blaOXA-48, with blakpc-2 prevailing as the predominant type, accounting for 73.9% (51/69). A total of 69 CR-KP strains showed high resistance to common clinical antibiotics, with the exception of ceftazidime/avibactam. The ST11 (P = 0.040), ST65 (P = 0.030) and blakpc-2 ST11 clones (P = 0.010) were found to be highly related to hvKp. Regarding the host, tracheal intubation (P = 0.008), intracranial infection (P = 0.020) and neutrophil count (P = 0.049) were significantly higher in the patients with CR-hvKP. Multivariate analysis showed tracheal intubation to be an independent risk factor for CR-hvKP infection (P = 0.030, OR = 4.131). According to the clinical data we collected, tracheal intubation was performed mainly in the elderly with severe underlying diseases, which implied that CR-hvKP has become prevalent among elderly patients with comorbidities.

CONCLUSIONS

The prevalence of CR-hvKP may be higher than expected in the healthcare setting. CR-hvKP is gradually becoming the dominant nosocomial pathogen, and its prevalence and treatment will be a major challenge. It is essential to enhance clinical awareness and management of CR-hvKP 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.

Molecular epidemiology and clinical characteristics of the type VI secretion system in Klebsiella pneumoniae causing abscesses

Purpose

The type VI system (T6SS) has the potential to be a new virulence factor for hypervirulent Klebsiella pneumoniae (hvKp) strains. This study aimed to characterize the molecular and clinical features of T6SS-positive and T6SS-negative K. pneumoniae isolates that cause abscesses.

Patients and methods

A total of 169 non-duplicate K. pneumoniae strains were isolated from patients with abscesses in a tertiary hospital in China from January 2018 to June 2022, and clinical data were collected. For all isolates, capsular serotypes, T6SS genes, virulence, and drug resistance genes, antimicrobial susceptibility testing, and biofilm formation assays were assessed. Multilocus sequence typing was used to analyze the genotypes of hvKp. T6SS-positive hvKp, T6SS-negative hvKp, T6SS-positive cKP, and T6SS-negative cKP (n = 4 strains for each group) were chosen for the in vivo Galleria mellonella infection model and in vitro competition experiments to further explore the microbiological characteristics of T6SS-positive K. pneumoniae isolates.

Results

The positive detection rate for T6SS was 36.1%. The rates of hvKp, seven virulence genes, K1 capsular serotype, and ST23 in T6SS-positive strains were all higher than those in T6SS-negative strains (p < 0.05). Multivariate logistic regression analysis indicated that the carriage of aerobactin (OR 0.01) and wcaG (OR 33.53) were independent risk factors for T6SS-positive strains (p < 0.05). The T6SS-positive strains had a stronger biofilm-forming ability than T6SS-negative strains (p < 0.05). The T6SS-positive and T6SS-negative strains showed no significant differences in competitive ability (p = 0.06). In the in vivo G. mellonella infection model, the T6SS(+)/hvKP group had the worst prognosis. Except for cefazolin and tegacyclin, T6SS-positive isolates displayed a lower rate of antimicrobial resistance to other drugs (p < 0.05). The T6SS-positive isolates were more likely to be acquired from community infections (p < 0.05).

Conclusion

Klebsiella pneumoniae isolates causing abscesses have a high prevalence of T6SS genes. T6SS-positive K. pneumoniae isolates are associated with virulence, and the T6SS genes may be involved in the hvKp virulence mechanism.

Risk factors and molecular epidemiology of bloodstream infections due to carbapenem-resistant Klebsiella pneumoniae

PURPOSE

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is emerging as a worldwide public health concern; however, molecular epidemiological surveillance of clinical CRKP bloodstream infection (BSI) in China is limited. We conducted a retrospective observational study to assess risk factors and the molecular epidemiology of CRKP BSI.

METHODS

We reviewed the medical records of enrolled patients to assess risk factors of CRKP BSI. Characteristics of CRKP isolates were analyzed by whole genome sequencing and Kleborate. Evolutionary diversification in CRKP isolates was described through Single Nucleotide Polymorphisms analysis and phylogenetic tree construction.

RESULTS

We found that prior ICU hospitalization and use of carbapenems were independent risk factors for CRKP BSI. The main CRKP sequence type (ST) and capsular serotype were ST11 and KL64, and KPC-2 was the most prevalent enzyme type of carbapenemase-carrying Klebsiella pneumoniae. The most prevalent aerobactin and yersiniabactin of ST11-CRKP were iuc-1 and ybt9 ICEKp3, as for KL64-CRKP. Phylogenomic analysis showed that the antibacterial resistance genes on plasmids were highly consistent, but the genetic background of the chromosomes was still different.

CONCLUSIONS

Our findings are important for hospitals, allowing them to limit dissemination of CRKP and optimize antibiotic administration.

Microevolution of CG23-I Hypervirulent Klebsiella pneumoniae during Recurrent Infections in a Single Patient

CG23-I lineage constitutes the majority of hypervirulent Klebsiella pneumoniae. A diabetic patient suffered six episodes of infections caused by CG23-I K. pneumoniae. A total of nine isolates were collected in 2020. We performed whole-genome sequencing to elucidate the within-patient evolution of CG23-I K. pneumoniae. The maximum pairwise difference among the nine longitudinally collected isolates was five single nucleotide polymorphisms. One of the mutations was at the Asp87 position of GyrA. Four indels were identified, including an initiator tRNAfMet duplication, a tRNAArg deletion, a 7-bp insertion, and a 22-bp deletion. All 9 isolates had the genomic features of CG23-I K. pneumoniae, a chromosome-borne ICEKp10, and a large virulence plasmid. The carriage of a complete set of genes for the biosynthesis of colibactin by ICEKp10 gave the nine isolates an ability to cause DNA damage to RAW264.7 cells. Compared with the initial isolate, the last isolate with an additional copy of initiator tRNAfMet grew faster in a nutrient-limiting condition and exhibited enhanced virulence in BALB/c mice. Collectively, we characterized the within-patient microevolution of CG23-I K. pneumoniae through an in-depth comparison of genome sequences. Using the in vitro experiments and mouse models, we also demonstrated that these genomic alterations endowed the isolates with advantages to pass through in vivo selection. IMPORTANCE CG23-I is a significant lineage of hypervirulent Klebsiella pneumoniae. This study characterizes the within-patient microevolution of CG23-I K. pneumoniae. Selective pressures from continuous use of antibiotics favored point mutations contributing to bacterial resistance to antibiotics. The duplication of an initiator tRNAfMet gene helped CG23-I K. pneumoniae proliferate to reach a maximal population size during infections. For longer persistence inside a human host, the large virulence plasmid evolved with more flexible control of replication through duplication of the iteron-1 region. With the genomic alterations, the last isolate had a growth advantage over the initial isolate and exhibited enhanced virulence in BALB/c mice. This study gives us a deeper understanding of the genome evolution during the within-patient pathoadaptation of CG23-I K. pneumoniae.