Molecular Epidemiology of Klebsiella pneumoniae Strains Causing Bloodstream Infections in Adults

The Molecular Genetics and Genomics of Plant-Pathogen Interactions

Plants have evolved an intricate immune system to protect themselves from potential pathogens [...].

Cannabinoid CB2 receptor agonist reduces local and systemic inflammation associated with pneumonia-induced sepsis in mice

Sepsis is a severe condition secondary to dysregulated host response to infection leading to tissue damage and organ dysfunction. Cannabinoid CB2 receptor has modulatory effects on the immune response. Therefore, this study investigated the effects of a cannabinoid CB2 receptor agonist on the local and systemic inflammatory process associated with pneumonia-induced sepsis. Pneumonia-induced sepsis was induced in mice by intratracheal inoculation of Klebsiella pneumoniae. Tissue and bronchoalveolar lavage (BAL) were collected 6, 24, or 48 h after surgery. Mice were treated with CB2 agonist (AM1241, 0.3 and 3 mg/kg, i.p.) and several parameters of inflammation were evaluated 24 h after sepsis induction. Polymorphonuclear cell migration to the infectious focus peaked 24 h after pneumonia-induced sepsis induction in male and female animals. Septic male mice presented a significant reduction of cannabinoid CB2 receptor density in the lung tissue after 24 h, which was not observed in females. CB2 expression in BAL macrophages was also reduced in septic animals. Treatment of septic mice with AM1241 reduced cell migration, local infection, myeloperoxidase activity, protein extravasation, and NOS-2 expression in the lungs. In addition, the treatment reduced plasma IL-1β, increased IL-10 and reduced the severity and mortality of septic animals. These results suggest that AM1241 promotes an interesting balance in the inflammatory response, maintaining lung function and preventing organ injury. Therefore, cannabinoid CB2 receptors are potential targets to control the excessive inflammatory process that occurs in severe conditions, and agonists of these receptors can be considered promising adjuvants in pneumonia-induced sepsis treatment.

Klebsiella pneumoniae bacteremia mortality: a systematic review and meta-analysis

Objective

To analyze the mortality rate of patients with Klebsiella pneumoniae bacteremia (KPB) and the impact of extended spectrum beta-lactamase (ESBL) producing or carbapenem-resistance (CR) KP on the mortality rate among patients with bacteremia.

Methods

EMbase, Web of Science, PubMed, and The Cochrane Library were searched up to September 18^th, 2022. Two reviewers independently extracted data and evaluated risk of bias of included studies by ROBINS-I tool. A meta-regression analysis was conducted using a mixed-effects model to explore possible sources of heterogeneity. A random-effects model was used for pooled analysis in case of significant heterogeneity (I²>50%). Otherwise, the fixed-effects model was performed.

Results

A total of 157 studies (37,915 enrolled patients) were included in the meta-analysis. The pooled death proportions of KPB were 17% (95% CI=0.14-0.20) at 7-day, 24% (95% CI=0.21-0.28) at 14-day, 29% (95% CI=0.26-0.31) at 30-day, 34% (95% CI=0.26-0.42) at 90-day, and 29% (95% CI=0.26-0.33) in hospital, respectively. Heterogeneity was found from the intensive care unit (ICU), hospital-acquired (HA), CRKP, and ESBL-KP in the meta-regression analysis. More than 50% of ICU, HA, CRKP, and ESBL-KP were associated with a significant higher 30-day mortality rates. The pooled mortality odds ratios (ORs) of CRKP vs. non-CRKP were 3.22 (95% CI 1.18-8.76) at 7-day, 5.66 (95% CI 4.31-7.42) at 14-day, 3.87 (95% CI 3.01-3.49) at 28- or 30-day, and 4.05 (95% CI 3.38-4.85) in hospital, respectively.

Conclusions

This meta-analysis indicated that patients with KPB in ICU, HA-KPB, CRKP, and ESBL-KP bacteremia were associated with a higher mortality rate. The high mortality rate caused by CRKP bacteremia has increased over time, challenging the public health.

Novel Virulence Factors Deciphering Klebsiella pneumoniae KpC4 Infect Maize as a Crossing-Kingdom Pathogen: An Emerging Environmental Threat

Klebsiella pneumoniae is not only a human and animal opportunistic pathogen, but a food-borne pathogen. Cross-kingdom infection has been focused on since K. pneumoniae was identified as the pathogen of maize, banana, and pomegranate. Although the pathogenicity of K. pneumoniae strains (from ditch water, maize, and human) on plant and mice has been confirmed, there are no reports to explain the molecular mechanisms of the pathogen. This study uncovered the K. pneumoniae KpC4 isolated from maize top rot for the determination of various virulence genes and resistance genes. At least thirteen plant disease-causing genes are found to be involved in the disruption of plant defense. Among them, rcsB is responsible for causing disease in both plants and animals. The novel sequence types provide solid evidence that the pathogen invades plant and has robust ecological adaptability. It is imperative to perform further studies on the verification of these KpC4 genes’ functions to understand the molecular mechanisms involved in plant−pathogen interactions.

Identification of extended-spectrum beta-lactamase (CTX-M)-producing Klebsiella pneumoniae belonging to ST37, ST290, and ST2640 in captive giant pandas

Background

Extended-spectrum β-lactamases (ESBL)-producing strains of Klebsiella pneumoniae remain a worldwide, critical clinical concern. However, limited information was available concerning ESBL-producing Klebsiella pneumoniae in giant pandas. The objective of this study was to characterize ESBL-producing Klebsiella pneumoniae isolates from captive giant pandas. A total of 211 Klebsiella pneumoniae isolates were collected from 108 giant pandas housed at the Chengdu Research Base of Giant Panda Breeding (CRBGP), China. Samples were screened for the ESBL-producing phenotype via the double-disk synergy test.

Result

A total of three (1.42%, n = 3/211) ESBL-producing Klebsiella pneumoniae strains were identified, and characterization of ESBL-producing Klebsiella pneumoniae isolates were studied by the detection of ESBL genes and mobile genetic elements (MGEs), evaluation of antimicrobial susceptibility and detection of associated resistance genes. Clonal analysis was performed by multi-locus sequencing type (MLST). Among the three ESBL-producing isolates, different ESBL-encoding genes, including bla_CTX-M, and bla_TEM, were detected. These three isolates were found to carry MGEs genes (i.e., IS903 and tnpU) and antimicrobial resistance genes (i.e., aac(6')-Ib, aac(6')-I, qnrA, and qnrB). Furthermore, it was found that the three isolates were not hypermucoviscosity, resistant to at least 13 antibiotics and belonged to different ST types (ST37, ST290, and ST2640).

Conclusion

Effective surveillance and strict infection control strategies should be implemented to prevent outbreaks of ESBL-producing Klebsiella pneumoniae in giant pandas.

Coexistence of aminoglycoside resistance genes in CTX-M-producing isolates of Klebsiella pneumoniae in Bushehr province, Iran

Background and Objectives:

Increasing the rate of extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae has given rise to a major healthcare issue in clinical settings over the past few years. Treatment of these strains is hardly effective since the plasmid encoding ESBL may also carry other resistance genes including aminoglycosides. The current study aimed to evaluate the prevalence of ESBL-producing K. pneumoniae and investigate the coexistence of Cefoxitamase-Munich (bla_CTX-M) with aminoglycoside-modifying enzyme (AME) genes, aac(3)IIa as well as aac(6′)Ib, in CTX-M-producing K. pneumoniae isolated from patients in Bushehr province, Iran.

Materials and Methods:

A total of 212 K. pneumoniae isolates were collected and confirmed using polymerase chain reaction (PCR) of the malate dehydrogenase gene. Isolates were screened for production of ESBL. Phenotypic confirmatory test was performed using combined disk test. The genes encoding CTX-M groups and AME genes, aac(3)IIa and aac(6′)Ib, were investigated by PCR.

Results:

The ESBL phenotype was detected in 56 (26.4%) K. pneumoniae isolates. Moreover, 83.9% of ESBL-producing isolates carried the genes for CTX-M type β-lactamases, which were distributed into the two genetic groups of CTX-M-1 (97.8%)- and CTX-M-2 (2.1%)-related enzymes. Notably, among K. pneumoniae isolates containing the bla_CTX-M gene, 68.08% of isolates harbored AME genes. In addition, the coexistence of bla_CTX-M with aac(3)-IIa and aac(6′)-Ib was observed in 46.8% of CTX-M-producing K. pneumoniae isolates.

Conclusion:

This study provides evidence of a high prevalence of AME genes in CTX-M-producing K. pneumoniae isolates; therefore, in the initial empirical treatment of infections caused by ESBL-KP in regions with such antibiotic resistance patterns, aminoglycoside combination therapy should be undertaken carefully.

Molecular epidemiology of antimicrobial resistant microorganisms in the 21th century: a review of the literature

Healthcare-associated infections (HAIs) are the most frequent and severe complication acquired in healthcare settings with high impact in terms of morbidity, mortality and costs. Many bacteria could be implicated in these infections, but, expecially multidrug resistance bacteria could play an important role. Many microbial typing technologies have been developed until to the the bacterial whole-genome sequencing and the choice of a molecular typing method therefore will depend on the skill level and resources of the laboratory and the aim and scale of the investigation. In several studies the molecular investigation of pathogens involved in HAIs was performed with many microorganisms identified as causative agents such as Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Clostridium difficile, Acinetobacter spp., Enterobacter spp., Enterococcus spp., Staphylococcus aureus and several more minor species. Here, we will describe the most and least frequently reported clonal complex, sequence types and ribotypes with their worldwide geographic distribution for the most important species involved in HAIs.

Prevalence of extended-spectrum β-lactamase-producing Klebsiella pneumoniae: First systematic review and meta-analysis from Iran

OBJECTIVES

Extended-spectrum β-lactamase-producing Klebsiella pneumoniae (ESBL-KP) have emerged as an important pathogen causing severe infections worldwide. Infections due to ESBL-KP are associated with high morbidity and mortality, especially in developing countries such as Iran. The aim of this study was to assess the pooled prevalence of ESBL-KP with different gene variants in Iran.

METHODS

A literature search of Medline (via PubMed), Embase, Web of Science and Iranian Database was performed. A meta-analysis was conducted using Comprehensive Meta-Analysis Software (version 2.2, Biostat). A fixed- or random-effects model was used based on the heterogeneity test. Publication bias was determined using Begg's rank correlation and Egger's weighted regression methods.

RESULTS

Among 783 articles identified, 43 studies met the eligibility criteria. The pooled prevalence of ESBL-KP was 43.5% (95% CI 39.3-47.9%) among clinical K. pneumoniae isolates. Among genes encoding ESBLs during 2000-2009, SHV, CTX-M and TEM were found with prevalences of 23.3%, 15.2% and 12.3%, respectively, whilst the prevalences of SHV, CTX-M, TEM and VEB were 24%, 28.1%, 25.2% and 8.3%, respectively, during the period 2010-2018.

CONCLUSION

The prevalence of ESBL-KP has increased steadily in recent years among clinical K. pneumoniae isolates in Iran. Thus, initial identification of ESBL-KP according to Clinical and Laboratory Standards Institute (CLSI) guidelines, proper molecular approaches, and implementation of antimicrobial stewardship programmes in Iranian hospitals together with comprehensive infection control measures are urgently needed to control the dissemination of these strains.

Clinical characteristics, antimicrobial resistance and capsular types of community-acquired, healthcare-associated, and nosocomial Klebsiella pneumoniae bacteremia

Background

Klebsiella pneumoniae bacteremia is a major cause of morbidity and mortality worldwide. We aimed to compare the clinical characteristics, distribution of capsular types, and antimicrobial resistance of K. pneumoniae bacteremia among community-acquired (CA), healthcare-associated (HCA), and nosocomial infections.

Methods

This retrospective study of patients with K. pneumoniae bacteremia was conducted at Taipei Veterans General Hospital from January to December 2015. Clinical characteristics of K. pneumoniae bacteremia were collected. The K. pneumoniae isolates were subjected to antimicrobial susceptibility testing and capsular genotyping.

Results

In total, 337 patients with K. pneumoniae bacteremia were identified: 70 (20.8%), 102 (30.3%), and 165 (48.9%) presented with CA, HCA, and nosocomial infection, respectively. The 28-day mortality of HCA bacteremia was lower than that of nosocomial bacteremia (17.6% versus 30.9%, p = 0.016); however, that of the HCA and CA bacteremia was similar (17.6% versus 14.3%, p = 0.557). CA isolates had the highest prevalence of virulent capsular types (51.4%), followed by HCA (36.3%) and nosocomial isolates (19.4%). The proportion of multidrug-resistant (MDR) isolates was highest in nosocomial infections (41.8%), followed by HCA (23.5%) and CA infections (5.7%).

Conclusion

CA, HCA and nosocomial K. pneumoniae are distinct entities, as evidenced by the differences in clinical characteristics, antimicrobial resistance, and capsular types found in this study.