Klebsiella pneumoniae Liver Abscess

Development of a nomogram to assess thromboembolic risk in patients with liver abscesses

Thromboembolism, a serious complication in patients with liver abscesses, can lead to organ deterioration if left untreated. However, factors associated with thromboembolism in these patients remain poorly understood. We aimed to identify the factors associated with liver abscess complications, with a focus on thromboembolism and metastatic infection. Data from 325 patients diagnosed with liver abscesses between March 2019 and June 2023 were retrospectively collected. Baseline clinical and laboratory variables associated with thromboembolic events and metastatic infections were analyzed using logistic regression. A nomogram for predicting thromboembolism was constructed using significant predictors. Among the 325 patients, the median age was 68.0 years, and included 129 women. Fifty patients experienced thromboembolic events and 44 had metastatic infections. Significant predictors for thromboembolic events included white blood cell (WBC)  ≥ 20,000/µL (odds ratio [OR] 3.401, p = 0.002), platelet count < 100,000/µL (OR 3.291, p = 0.004), and abscess septation (OR 2.704, p = 0.007). Age ≥ 65 years (OR 0.457, p = 0.040), WBC  ≥ 20,000/µL (OR 3.340, p = 0.005), and abscess septation (OR 2.909, p = 0.008) were identified as factors associated with metastatic infections. A nomogram was constructed to predict thromboembolism using the following four variables: WBC  ≥ 20,000/µL platelet count < 100,000/µL, albumin < 2.8 g/dL, and abscess septation, and demonstrated an AUROC of 0.755. Our study is the first to develop a reliable nomogram for thromboembolism prediction, utilizing easily accessible clinical parameters. This innovative model enables clinicians to efficiently identify high-risk patients, facilitating the implementation of additional studies to mitigate the risk of overlooked thromboembolic events in these at-risk individuals.

Therapeutic Potential of Lactiplantibacillus plantarum FB091 in Alleviating Alcohol-Induced Liver Disease through Gut-Liver Axis

Alcoholic liver disease (ALD) poses a significant global health burden, often requiring liver transplantation and resulting in fatalities. Current treatments, like corticosteroids, effectively reduce inflammation but carry significant immunosuppressive risks. This study evaluates Lactiplantibacillus plantarum FB091, a newly isolated probiotic strain, as a safer alternative for ALD treatment. Using an in vivo mouse model, we assessed the effects of L. plantarum FB091 on alcohol-induced liver damage and gut microbiota composition. Alcohol and probiotics administration did not significantly impact water/feed intake or body weight. Histopathological analysis showed that L. plantarum FB091 reduced hepatocellular ballooning and inflammatory cell infiltration in liver tissues and mitigated structural damage in colon tissues, demonstrating protective effects against alcohol-induced damage. Biomarker analysis indicated that L. plantarum FB091 decreased aspartate aminotransferase levels, suggesting reduced liver damage, and increased alcohol dehydrogenase activity, indicating enhanced alcohol metabolism. Additionally, cytokine assays revealed a reduction in pro-inflammatory TNF-α and an increase in anti-inflammatory IL-10 levels in colon tissues of the L. plantarum FB091 group, suggesting an anti-inflammatory effect. Gut microbiota analysis showed changes in the L. plantarum FB091 group, including a reduction in Cyanobacteria and an increase in beneficial bacteria such as Akkermansia and Lactobacillus. These changes correlated with the recovery and protection of liver and colon health. Overall, L. plantarum FB091 shows potential as a therapeutic probiotic for managing ALD through its protective effects on liver and colon tissues, enhancement of alcohol metabolism, and beneficial modulation of gut microbiota. Further clinical studies are warranted to confirm these findings in humans.

Leukopenia-a rare complication secondary to invasive liver abscess syndrome in a patient with diabetes mellitus: A case report

BACKGROUND

Thrombocytopenia is a common complication of invasive liver abscess syndrome (ILAS) by Klebsiella pneumoniae (K. pneumoniae) infection, which indicates severe infection and a poor prognosis. However, the presence of leukopenia is rare. There are rare reports on leukopenia and its clinical significance for ILAS, and there is currently no recognized treatment plan. Early and broad-spectrum antimicrobial therapy may be an effective therapy for treating ILAS and improving its prognosis.

CASE SUMMARY

A 55-year-old male patient who developed fever, chills, and abdominal distension without an obvious cause presented to the hospital for treatment. Laboratory tests revealed thrombocytopenia, leukopenia, and multiple organ dysfunction. Imaging examinations revealed an abscess in the right lobe of the liver and thrombophlebitis, and K. pneumoniae was detected in the blood cultures. Since the patient was diabetic and had multi-system involvement, he was diagnosed with ILAS accompanied by leukopenia and thrombocytopenia. After antibiotic treatment and systemic supportive therapy, the symptoms disappeared, and the patient’s condition almost completely resolved.

CONCLUSION

Leukopenia is a rare complication of ILAS, which serves as an indicator of adverse prognostic outcomes and the severity of infection.

Bilateral Endogenous Endophthalmitis With Klebsiella pneumoniae Bacteremia Secondary to Hepatic Abscess

Klebsiella endophthalmitis is a rare cause of endogenous endophthalmitis, with very few cases documented in the US. We present a male patient in his 60s with a history of latent tuberculosis who presented to the hospital with complaints of acute bilateral vision loss that began three days prior to admission. The workup revealed Klebsiella pneumoniae bacteremia, a large hepatic abscess, severe orbital swelling, and acute angle-closure glaucoma. The patient received intravitreal antibiotics, intravenous antibiotics, a hepatic drain, intraocular pressure-lowering medications, and steroids. Bacteremia was cleared with antibiotics and source control; however, vision loss did not improve. This case emphasizes the acuity and severity of Klebsiella endogenous endophthalmitis and outlines the need for immediate intervention with the onset of symptoms to prevent irreversible vision loss.

COVID-19 and Prostatitis: A Review of Current Evidence

Coronavirus disease 2019 (COVID-19), a highly contagious viral disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), poses a global health threat. The virus enters host cells by binding with angiotensin-converting enzyme 2 (ACE2), which is then facilitated by the protease activity of transmembrane serine protease 2 (TMPRSS2). It triggers a cytokine storm that eventually leads to cell apoptosis, tissue damage, and organ failure. Therefore, any organs in the human body that have both receptors are highly susceptible to COVID-19 infection, potentially resulting in multiple-organ failure. The prostate has been reported to express high levels of ACE2 and TMPRSS2. While there are limited studies regarding the association between COVID-19 and prostatitis, the possibility that SARS-CoV-2 could cause prostatitis cannot be denied. Thus, through this review, a better insight into the associations of SAR-CoV-2 can be provided.

Macrophage-depleted young mice are beneficial in vivo models to assess the translocation of Klebsiella pneumonia from the gastrointestinal tract to the liver in the elderly

Pathobionts are commensal intestinal microbiota capable of causing systemic infections under specific conditions, such as environmental changes or aging. However, it is unclear how pathobionts are recognized by the intestinal mucosal immune system under physiological conditions. This study demonstrates that the gut pathobiont Klebsiella pneumoniae causes injury to the epithelium and translocates to the liver in specific pathogen-free mice treated with clodronate-liposomes that depleted macrophages. In the clodronate-liposome-treated mice, indigenous classical K. pneumoniae (cKp) with non-K1/K2 capsular serotypes were isolated from the liver, indicating that gut commensal cKp translocated from the gastrointestinal tract to the liver due to the depletion of intestinal macrophages. Oral inoculation of isolated cKp to clodronate-liposome-treated mice significantly reduced the survival rates compared to that of non-treated mice. Our findings demonstrate that intestinal mucosal macrophages play a pivotal role in sensing commensal cKp and suppressing their translocation to the liver. This study demonstrates that clodronate-liposome-treated mouse models are effective for screening and evaluating drugs that prevent the translocation of cKp to the liver, providing new insights into the development of preventive protocols against K. pneumoniae infection.

A unique case of hypervirulent Klebsiella pneumoniae acute cholecystitis complicated by portal vein thrombophlebitis: A case report and literature review

Hypervirulent Klebsiella pneumoniae remains a significant global public health concern, characterized by a unique syndrome involving monomicrobial primary pyogenic liver abscesses, often leading to metastatic complications such as endophthalmitis, meningitis, and other infections. These infections are frequently observed in immunocompetent hosts or diabetic patients, particularly those of Asian ethnicity. In this report, we present the case of a 66-year-old Burmese female, currently residing in the United States, who presented with severe swelling, pain, discharge, and vision loss in her left eye, along with abdominal pain. Subsequent investigation revealed monomicrobial Klebsiella pneumoniae acute cholecystitis with an adjacent liver abscess, complicated by bacteremia, endogenous endophthalmitis, and portal vein thrombosis. Treatment with ceftriaxone proved successful in addressing her intra-abdominal infections, while anticoagulation therapy was initiated following multidisciplinary discussions among all involved subspecialties. Early diagnosis and the timely administration of appropriate treatment are crucial in reducing mortality and preventing further complications.

Klebsiella pneumoniae K2 capsular polysaccharide degradation by a bacteriophage depolymerase does not require trimer formation

K2-capsular Klebsiella pneumoniae is a hypervirulent pathogen that causes fatal infections. Here, we describe a phage tailspike protein, named K2-2, that specifically depolymerizes the K2 capsular polysaccharide (CPS) of K. pneumoniae into tetrasaccharide repeating units. Nearly half of the products contained O-acetylation, which was thought crucial to the immunogenicity of CPS. The product-bound structures of this trimeric enzyme revealed intersubunit carbohydrate-binding grooves, each accommodating three tetrasaccharide units of K2 CPS. The catalytic residues and the key interactions responsible for K2 CPS recognition were identified and verified by site-directed mutagenesis. Further biophysical and functional characterization, along with the structure of a tetrameric form of K2-2, demonstrated that the formation of intersubunit catalytic center does not require trimerization, which could be nearly completely disrupted by a single-residue mutation in the C-terminal domain. Our findings regarding the assembly and catalysis of K2-2 provide cues for the development of glycoconjugate vaccines against K. pneumoniae infection.

IMPORTANCE

Generating fragments of capsular polysaccharides from pathogenic bacteria with crucial antigenic determinants for vaccine development continues to pose challenges. The significance of the C-terminal region of phage tailspike protein (TSP) in relation to its folding and trimer formation remains largely unexplored. The polysaccharide depolymerase described here demonstrates the ability to depolymerize the K2 CPS of K. pneumoniae into tetrasaccharide fragments while retaining the vital O-acetylation modification crucial for immunogenicity. By carefully characterizing the enzyme, elucidating its three-dimensional structures, conducting site-directed mutagenesis, and assessing the antimicrobial efficacy of the mutant enzymes against K2 K. pneumoniae, we offer valuable insights into the mechanism by which this enzyme recognizes and depolymerizes the K2 CPS. Our findings, particularly the discovery that trimer formation is not required for depolymerizing activity, challenge the current understanding of trimer-dependent TSP activity and highlight the catalytic mechanism of the TSP with an intersubunit catalytic center.

A retrospective study of endogenous endophthalmitis-related pyogenic liver abscess: An increasing complication in North Vietnam

Introduction

Endogenous endophthalmitis-related Klebsiella pyogenic liver abscess is a rare complication of metastatic infection. In most cases, visual acuity results are often impaired, even blind, and even with aggressive treatment with topical antibiotics, the final results are unsatisfactory. The objective of this study is to retrospectively based on medical records to describe clinical features, risk factors, and visual outcomes of patients with endogenous endophthalmitis-related pyogenic liver abscesses.

Methods

We reported a case series of 12 endogenous endophthalmitis-related pyogenic liver abscess patients from March 2021 to 2023. All cases of endogenous endophthalmitis were diagnosed at admission or during the hospital stay.

Results

From the medical records of 588 pyogenic liver abscess patients, we found 12 cases of endogenous endophthalmitis with 2.0%. The result showed a mean age of 61.5 ± 12.0 (41-78), diabetes mellitus (7 of 12), right lobe (7 of 12), single abscess (9 of 12), and the mean largest abscess diameter of 5.8 ± 1.7 cm (3.3-9). All patients had ocular symptoms such as eye pain (9 of 12), pus discharge (3 of 12), hypopyon (1 of 12), swollen eyelids (2 of 12), and corneal edema (2 of 12), pyogenic liver abscess before endogenous endophthalmitis (10 of 12), the median interval between endogenous endophthalmitis and pyogenic liver abscess 6.1 ± 1.9 days, ocular symptoms before diagnosis endogenous endophthalmitis 4.4 ± 2.3 days. All affected eyes were injected intravitreously with ceftazidime, amikacin, and vancomycin. Two patients underwent evisceration.

Conclusions

Endogenous endophthalmitis has permanent morbidity, reducing visual acuity, poor quality of life, and lacks the warning signs, so it is essential for early detection of symptoms and referral to ophthalmologists.

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.

Antimicrobial Resistance: Two-Component Regulatory Systems and Multidrug Efflux Pumps

The number of multidrug-resistant bacteria is rapidly spreading worldwide. Among the various mechanisms determining resistance to antimicrobial agents, multidrug efflux pumps play a noteworthy role because they export extraneous and noxious substrates from the inside to the outside environment of the bacterial cell contributing to multidrug resistance (MDR) and, consequently, to the failure of anti-infective therapies. The expression of multidrug efflux pumps can be under the control of transcriptional regulators and two-component systems (TCS). TCS are a major mechanism by which microorganisms sense and reply to external and/or intramembrane stimuli by coordinating the expression of genes involved not only in pathogenic pathways but also in antibiotic resistance. In this review, we describe the influence of TCS on multidrug efflux pump expression and activity in some Gram-negative and Gram-positive bacteria. Taking into account the strict correlation between TCS and multidrug efflux pumps, the development of drugs targeting TCS, alone or together with already discovered efflux pump inhibitors, may represent a beneficial strategy to contribute to the fight against growing antibiotic resistance.

Identification of three capsule depolymerases in a bacteriophage infecting Klebsiella pneumoniae capsular types K7, K20, and K27 and therapeutic application

BACKGROUND

Klebsiella pneumoniae capsular types K1, K2, K5, K20, K54, and K57 are prevalent hypervirulent types associated with community infections, and worrisomely, hypervirulent strains that acquired drug resistance have been found. In the search for alternative therapeutics, studies have been conducted on phages that infect K. pneumoniae K1, K2, K5, and K57-type strains and their phage-encoded depolymerases. However, phages targeting K. pneumoniae K20-type strains and capsule depolymerases capable of digesting K20-type capsules have rarely been reported. In this study, we characterized a phage that can infect K. pneumoniae K20-type strains, phage vB_KpnM-20.

METHODS

A phage was isolated from sewage water in Taipei, Taiwan, its genome was analyzed, and its predicted capsule depolymerases were expressed and purified. The host specificity and capsule-digesting activity of the capsule depolymerases were determined. The therapeutic effect of the depolymerase targeting K. pneumoniae K20-type strains was analyzed in a mouse infection model.

RESULTS

The isolated Klebsiella phage, vB_KpnM-20, infects K. pneumoniae K7, K20, and K27-type strains. Three capsule depolymerases, K7dep, K20dep, and K27dep, encoded by the phage were specific to K7, K20, and K27-type capsules, respectively. K20dep also recognized Escherichia coli K30-type capsule, which is highly similar to K. pneumoniae K20-type. The survival of K. pneumoniae K20-type-infected mice was increased following administration of K20dep.

CONCLUSIONS

The potential of capsule depolymerase K20dep for the treatment of K. pneumoniae infections was revealed using an in vivo infection model. In addition, K7dep, K20dep, and K27dep capsule depolymerases could be used for K. pneumoniae capsular typing.

Machine learning models for prediction of invasion Klebsiella pneumoniae liver abscess syndrome in diabetes mellitus: a singled centered retrospective study

OBJECTIVE

This study aimed to develop and validate a machine learning algorithm-based model for predicting invasive Klebsiella pneumoniae liver abscess syndrome(IKPLAS) in diabetes mellitus and compare the performance of different models.

METHODS

The clinical signs and data on the admission of 213 diabetic patients with Klebsiella pneumoniae liver abscesses were collected as variables. The optimal feature variables were screened out, and then Artificial Neural Network, Support Vector Machine, Logistic Regression, Random Forest, K-Nearest Neighbor, Decision Tree, and XGBoost models were established. Finally, the model's prediction performance was evaluated by the ROC curve, sensitivity (recall), specificity, accuracy, precision, F1-score, Average Precision, calibration curve, and DCA curve.

RESULTS

Four features of hemoglobin, platelet, D-dimer, and SOFA score were screened by the recursive elimination method, and seven prediction models were established based on these variables. The AUC (0.969), F1-Score(0.737), Sensitivity(0.875) and AP(0.890) of the SVM model were the highest among the seven models. The KNN model showed the highest specificity (1.000). Except that the XGB and DT models over-estimates the occurrence of IKPLAS risk, the other models' calibration curves are a good fit with the actual observed results. Decision Curve Analysis showed that when the risk threshold was between 0.4 and 0.8, the net rate of intervention of the SVM model was significantly higher than that of other models. In the feature importance ranking, the SOFA score impacted the model significantly.

CONCLUSION

An effective prediction model of invasion Klebsiella pneumoniae liver abscess syndrome in diabetes mellitus could be established by a machine learning algorithm, which had potential application value.

Klebsiella, a Clever Survivor Presenting As Pyogenic Liver Abscess Years After Travel

Klebsiella pneumoniae is a known cause of pyogenic liver abscess and has an increased prevalence in Southeast Asia. We present two cases of individuals with remote travel history to southeast Asia presenting with fevers, chills, and abdominal pain secondary to pyogenic liver abscess. Neither individual had a comorbid medical condition or history of prior hepato-biliary pathology that would predispose them to bacterial translocation and abscess formation. These patients were both successfully treated with percutaneous drainage and antibiotics. We present these cases to add to the growing body of literature surrounding hyper-mucoid strains of Klebsiella pneumonia causing a pyogenic liver abscess.

Clinical Spectrum and Outcomes of Cryptogenic Klebsiella pneumoniae Liver Abscess in the Americas: A Scoping Review

(1) Background: Cryptogenic Klebsiella pneumoniae liver abscesses are an invasive infection with or without extra hepatic involvement in the absence of hepatobiliary disease or abdominal malignancy. Most of the evidence has emanated from reports from Asia, and previous studies in the Americas have limited clinical characterization. (2) Methods: To understand this syndrome's characteristics on our continent, we conducted a scoping review to identify adult cases of idiopathic, community-acquired monomicrobial K. pneumoniae liver abscess in the Americas. (3) Results: We identified 144 cases spanning 1978-2022. Most cases were reported in males that had traveled or migrated from Southeast or East Asia with diabetes mellitus. Extrahepatic involvement and bacteremia were common, including seeding to the lungs, ocular structures, and central nervous system. Although limited by sample size, the most commonly reported genes were magA or rmpA. Concomitant percutaneous drainage and third generation cephalosporins (alone or in combination with other antibiotics) were frequently used, yet pooled fatality occurred in 9% of the reported cases. (4) Conclusions: The features of cryptogenic K. pneumoniae liver abscess in the Americas mirror those described in Asia, confirming its global dissemination. This condition is increasingly being reported in our continent and carries significant clinical impact due to its systemic invasiveness.

Phages for treatment of Klebsiella pneumoniae infections

Klebsiella pneumoniae is an opportunistic pathogen involved in both hospital- and community-acquired infections. K. pneumoniae is associated with various infections, including pneumonia, septicemia, meningitis, urinary tract infection, and surgical wound infection. K. pneumoniae possesses serious virulence, biofilm formation ability, and severe resistance to many antibiotics especially hospital-acquired strains, due to excessive use in healthcare systems. This limits the available effective antibiotics that can be used for patients suffering from K. pneumoniae infections; therefore, alternative treatments are urgently needed. Bacteriophages (for short, phages) are prokaryotic viruses capable of infecting, replicating, and then lysing (lytic phages) the bacterial host. Phage therapy exhibited great potential for treating multidrug-resistant bacterial infections comprising K. pneumoniae. Hence, this chapter emphasizes and summarizes the research articles in the PubMed database from 1948 until the 15th of December 2022, addressing phage therapy against K. pneumoniae. The chapter provides an overview of K. pneumoniae phages covering different aspects, including phage isolation, different morphotypes of isolated phages, in vitro characterization, anti-biofilm activity, various therapeutic forms, in vivo research and clinical studies.

Increasing incidence of pyogenic liver abscess in Southern Sweden: a population-based study from 2011 to 2020

BACKGROUND

Pyogenic liver abscess (PLA) is a rare but potentially life-threatening disease, and estimates suggest a gradual increase in the incidence during the last decades. The primary aim of this study was to report the incidence, trend and aetiology of PLA during a decade in Southern Sweden.

METHODS

This was a population-based observational cohort study between 2011 and 2020 in Skåne, Southern Sweden. Data were retrieved from the Swedish National Board of Health and Welfare for all individuals diagnosed with liver abscess (K750) according to ICD-10 (International Statistical Classification of Diseases, 10th revision).

RESULTS

A total of 456 episodes of PLA occurred in 364 patients during the study period. The median age of the first PLA episode was 71 years (range 3-97) and 57% (n = 206) were men. The mean incidence of all patients was 3.4/100,000 person-years (range 1.8-5.2). The incidence increased almost three times, from 1.8/100,000 person-years in 2011 to 5.2/100,000 person-years in 2020. Streptococcus species, Escherichia coli and Klebsiella species accounted for the vast majority of both mono- and polymicrobial findings in both blood and local abscess cultures. 16s rDNA added information about aetiology in 37% of episodes.

CONCLUSION

The incidence of PLA increased during the study period, and Streptococcus spp., Klebsiella spp. and E. coli dominated both blood and local cultures. Despite antimicrobial therapy, pathogens could be found in local abscess cultures several weeks into treatment. Increased use of 16s rDNA in the management of PLA could be beneficial.

Emergence of Carbapenemase-Producing Hypervirulent Klebsiella pneumoniae in Switzerland

Increasing occurrence of multidrug-resistant (MDR) and hypervirulent (hv) Klebsiella pneumoniae (MDR-hvKp) convergent clones is being observed. Those strains have the potential of causing difficult-to-treat infections in healthy adults with an increased capacity for mortality. It is therefore crucial to track their dissemination to prevent their further spread. The aim of our study was to investigate the occurrence of carbapenemase-producing hvKp isolates in Switzerland and to determine their genetic profile. A total of 279 MDR carbapenemase-producing K. pneumoniae from patients hospitalized all over Switzerland was investigated, and a rate of 9.0% K. pneumoniae presenting a virulence genotype was identified. Those isolates produced either KPC, NDM, or OXA-48 and had been either recovered from rectal swabs, urine, and blood. A series of previously reported K. pneumoniae clones such as ST23-K1, ST395-K2, and ST147-K20 or ST147-K64 were identified. All the isolates defined as MDR-hvKp (4.7%) possessed the aerobactin and the yersiniabactin clusters. The ST23-K1s were the only isolates presenting the colibactin cluster and achieved higher virulence scores. This study highlights the occurrence and circulation of worrisome MDR-hvKp and MDR nonhypervirulent K. pneumoniae (MDR-nhv-Kp) isolates in Switzerland. Our findings raise an alert regarding the need for active surveillance networks to track and monitor the spread of such successful hybrid clones representing a public health threat worldwide.

Genome sequence and genomic analysis of liver abscess caused by hypervirulent Klebsiella pneumoniae

Hypervirulent Klebsiella pneumoniae (hvKp) is an important pathotype with enhanced virulence features compared with classical K. pneumoniae (cKp). hvKp usually causes life-threatening infections in the community, often affecting young and healthy individuals. During the past few decades, hvKp-induced liver abscess has been increasingly reported in Asia and is emerging as a global disease. To better comprehend the molecular characteristics of hvKp-induced liver abscess and recognize the global dissemination of hypervirulent strains with resistance determinants, we sequenced the whole genome of 26 K. pneumoniae strains from patients with liver abscess (KLA) and investigated the clinical factors related to different phenotype groups. The epidemiology, virulence-related factors, and antimicrobial resistance determinants were also discussed. The age, gender, and whether being hospitalized showed no differences among the string-positive and -negative groups were also studied. The assembly and annotation suggested that most of the 26 new liver abscess-causing hvKp strains were ST23-K1 or ST86-K2, and only one of the strains exhibited multidrug resistance. Compared with the existing 36 global liver abscess genome sequences, higher sequence type and virulence gene diversity were found in the new genomes. The clinical characteristics and genomic data of the isolated strains will enrich our knowledge for comparative genomic studies, allowing the better understanding of hvKp characteristics and evolution.

Genetic and Phenotypic Characterization of Multidrug-Resistant Klebsiella pneumoniae from Liver Abscess

Cooccurrence of multidrug resistant (MDR) and hypervirulence phenotypes in liver abscess-causing Klebsiella pneumoniae (LAKp) would pose a major threat to public health. However, relatively little information is available on the genomic and phenotypic characteristics of this pathogen. This study aimed to investigate the virulence and resistance phenotype and genotype of MDR LAKp strains from 2016 to 2020. We collected 18 MDR LAKp strains from 395 liver abscess samples and characterized these strains using antimicrobial susceptibility test, string test, mucoviscosity assay, biofilm formation assay, Galleria mellonella killing assay, and whole-genome sequencing. Besides, phylogenetic and comparative genomic analyses were performed on these MDR LAKp, along with 94 LAKp genomes from global sources. Most of these MDR LAKp strains exhibited resistance to cephalosporins, quinolones, and chloramphenicol. Virulence assays revealed that only half of MDR LAKp strains exhibited higher virulence than classical MDR strain K. pneumoniae MGH78578. Importantly, we identified three ST11 KL64 hypervirulence carbapenem-resistant strains carrying blaKPC-2 and one colistin-resistant strain carrying mcr-1. Phylogenetic analysis revealed that 112 LAKp genomes were divided into two clades, and most of MDR LAKp strains in this study belonged to clade 1 (83.33%, 15/18). We also detected the loss of mucoviscosity mediated by mutations and ISKpn14 insertion in rmpA, and the latter representing a novel mechanism by which bacteria regulate RmpA system. This study provides novel insights into MDR LAKp and highlights the necessity for measures to prevent further spread of such organisms in hospital settings and the community. IMPORTANCE Pyogenic liver abscess is a potentially life-threatening suppurative infection of hepatic parenchyma. K. pneumoniae has emerged as a predominant pathogen of pyogenic liver abscess. Liver abscess-causing K. pneumoniae is generally considered hypervirulent K. pneumoniae and is susceptible to most antibiotics. Recently, convergence of multidrug resistant and hypervirulence phenotypes in liver abscess-causing K. pneumoniae was emerging and poses a major threat to public health. However, relatively little information is available on liver abscess-causing multidrug-resistant hypervirulent K. pneumoniae. In this study, we characterized phenotype and genotype of virulence and resistance of 18 multidrug-resistant hypervirulent liver abscess-causing K. pneumoniae strains collected from 395 pyogenic liver abscess cases in a tertiary teaching hospital over a 5-year period to enable in-depth understanding of this pathogen.

Predictive and prognostic factors associated with unliquefied pyogenic liver abscesses

INTRODUCTION

Poor liquefaction of pyogenic liver abscesses, which makes drainage impossible at the time of diagnosis, is not infrequent. The impact of poor liquefaction and subsequent drainage failure on clinical outcomes is unknown.

METHODS

We conducted a retrospective study with all patients diagnosed with liver abscesses from July 2017 through June 2020. Late drainage (LD) was defined as drainage performed ≥48 h after diagnosis due to poor liquefaction. Logistic regression was performed to identify the factors associated with late or non-drainage (LD/ND). The Cox proportional hazard model was used to identify the variables related to abscess recurrence by 90 days after diagnosis.

RESULTS

A total of 153 patients were included. Thirty (19.6%) patients underwent LD and 54 (35.3%) did not undergo drainage. Other than non-cystic appearance, LD/ND was associated with smaller size (adjusted odds ratio [aOR] 0.85, 95% confidence interval [CI] 0.73-0.98, p = 0.031) and culture-negativity (aOR 2.69, 95% CI 1.14-6.67, p = 0.027). Current hepatopancreaticobiliary malignancy was the only significant predictor of 90-day recurrence. Neither LD/ND (OR, 0.56; 95% CI, 0.13-2.41; p = 0.426) nor LD (OR, 1.26; 95% CI, 0.23-5.55; p = 0.719) was associated with recurrence by 90 days. The incidence of late complications was reduced by drainage, without a reduction in the duration of hospitalization.

CONCLUSION

Several clinical features were associated with undrainable liver abscesses. Neither LD/ND nor ND had an adverse impact on clinical outcomes.

Successful hepatic resection for invasive Klebsiella pneumoniae large multiloculated liver abscesses with percutaneous drainage failure: A case report

Background

Invasive Klebsiella-associated liver abscesses can progress rapidly and cause severe metastatic infections such as meningitis and hydrocephalus, which are associated with high morbidity and mortality. In patients with large multiloculated liver abscesses after failure of percutaneous drainage, rapid diagnosis of the abscess followed by hepatic resection is necessary for early recovery and to prevent severe secondary metastatic complications.

Case presentation

An 84-year-old woman with a large liver abscess and in septic shock was transferred to our hospital. Abdominal CT showed multiloculated liver abscesses 15 cm in diameter in the right lobe of the liver. We first performed percutaneous liver abscess drainage. The patient was managed in the intensive care unit, as well as treated with intravenous administration of meropenem followed by cefozopran according to the antibiogram. Klebsiella pneumoniae with invasive infection was confirmed by a string test in an isolated colony of K. pneumoniae; the K1 serotype with the rmpA and magA genes was determined by polymerase chain reaction and Sanger sequencing. Additional percutaneous liver abscess drainage was performed due to initial inadequate drainage. Although the abscess had shrunk to a diameter of 8 cm after drainage in 4 weeks, the patient recovered from sepsis, but still had low-grade fever (occasionally 38°C) and continued to have symptoms of chronic inflammation with persistent hyper mucus discharge from the liver abscess. Surgical resection was chosen to prevent prolonged hospitalization and ensure early recovery. A right posterior sectionectomy of the liver, including liver abscess, was performed. The post-operative course was uneventful, with no complications, and she was discharged after 18 days. There were no signs of abscess recurrence 1 year after surgery.

Conclusion

We present a case of successful hepatic resection after percutaneous drainage failure in a patient with invasive K. pneumoniae multiloculated liver abscess.

Elucidating the effect of iron acquisition systems in Klebsiella pneumoniae on susceptibility to the novel siderophore-cephalosporin cefiderocol

BACKGROUND

Cefiderocol (CFDC) is a novel siderophore-cephalosporin, effective against multidrug-resistant Gram-negative bacteria. As it has a siderophore side chain, it can utilize iron acquisition systems for penetration of the bacterial outer membrane. We aimed to elucidate the role of siderophores and iron uptake receptors in defining Klebsiella pneumoniae susceptibility to CFDC.

METHODS

Initially, 103 K. pneumoniae strains were characterized for susceptibility to different antibiotics including CFDC. CFDC minimum inhibitory concentrations (MIC) were determined in iron-depleted and iron-enriched conditions. Iron uptake genes including siderophores, their receptors, ferric citrate (fecA) and iron uptake (kfu) receptors were detected by PCR in all the strains. For 10 selected strains, gene expression was tested in iron-depleted media with or without CFDC treatment and compared to expression in iron-enriched conditions.

RESULTS

CFDC exhibited 96.1% susceptibility, being superior to all the other antibiotics (MIC50: 0.5 and MIC90: 4 μg/ml). Only three strains (2.9%) were intermediately susceptible and a pandrug resistant strain (0.97%) was resistant to CFDC (MIC: 8 and 256 μg/ml, respectively). The presence of kfu and fecA had a significant impact on CFDC MIC, especially when co-produced, and if coupled with yersiniabactin receptor (fyuA). CFDC MICs were negatively correlated with enterobactin receptor (fepA) expression and positively correlated with expression of kfu and fecA. Thus, fepA was associated with increased susceptibility to CFDC, while kfu and fecA were associated with reduced susceptibility to CFDC. CFDC MICs increased significantly in iron-enriched media, with reduced expression of siderophore receptors, hence, causing less drug uptake.

CONCLUSION

Iron acquisition systems have a significant impact on CFDC activity, and their altered expression is a factor leading to reduced susceptibility. Iron concentration is also a major player affecting CFDC susceptibility; therefore, it is essential to explore possible ways to improve the drug activity to facilitate its use to treat infections in iron-rich sites.

Klebsiella pneumoniae Infection as a Mimicker of Multiple Metastatic Lesions

We describe the case of a 42-year-old man with cirrhosis who presented with fever and imaging concerning for metastatic disease from suspected renal cell carcinoma. He had a right renal mass with multiple pulmonary masses and underwent a lung biopsy and oncology consultation. Blood cultures revealed Klebsiella pneumoniae, and all the lesions disappeared after intravenous (IV) antibiotics. Our case attempts to increase awareness of this unique presentation of invasive Klebsiella infections and discusses host factors that can predispose to this condition.

Liver Abscess Caused by Klebsiella Pneumoniae in the Absence of Hepatobiliary Disease

Klebsiella pneumoniae is notorious for causing abscesses in patients without any previous hepatobiliary disease and is a cause of liver abscesses. We report the case of a 70-year-old man with a past medical history of hypertension and benign prostatic hyperplasia who presented with a cough and fever lasting two weeks. The findings from his physical examination were unremarkable, but his laboratory investigations were significant for elevated inflammatory markers. A computed tomography scan of his abdomen revealed a complex septated cyst in the right lobe of his liver, and his blood culture was positive for K. pneumoniae. He responded well to drainage and intravenous and oral antibiotics. His abscess resolved fully. Cases of K. pneumoniae in the United States are rare, and studies are necessary to explore its epidemiology. Atypical symptoms make diagnosis a challenge, and physicians are urged to retain high levels of suspicion to diagnose and treat such cases early.

Epidemiological Features of Klebsiella pneumoniae Infection in the Hepatobiliary System of Patients in Yantai, China, Based on Clinical and Genetic Analyses

Purpose

To investigate the epidemiological features of Klebsiella pneumoniae infection of the hepatobiliary system of patients in Yantai, China.

Methods

This retrospective study was conducted from January to December 2019 in Yantai Yuhuangding Hospital. Patients for whom K. pneumoniae was isolated from the hepatobiliary system were considered for inclusion. The clinical features and genetic analyses were conducted to explore the epidemiological characteristics.

Results

A total of 88 cases were enrolled, including 69 cases of hypervirulent K. pneumoniae (hvKP) and 19 cases of classical K. pneumoniae (cKP). Community-acquired infections, fever, liver abscess, and C-reactive protein (CRP) and procalcitonin (PCT) levels were significantly higher, while biliary tract disease was lower in the hvKP group compared with the cKP group. Among the 69 hvKP infections, 61 developed a liver abscess. Community-acquired infections, fever, and CRP and PCT levels were higher, whereas biliary tract disease and malignancy were lower in the liver abscess group compared with the non-liver abscess group. All strains were susceptible to the majority of antibiotics tested. All hvKP strains possessed the bla_SHV, oqxA, oqxB and fosA resistance genes. K1 and K2 accounted for 78% of hvKP strains. K1 strains belonged to sequence types ST23 and ST700, whereas K2 strains belonged to ST65, ST86 and ST5212. K1 isolates possessed the most virulence determinants, followed by K2 and non-K1/K2 isolates. K2 isolates lacked the allS gene, which was rare in non K1/K2 isolates, but present in most K1 isolates. The mceG gene was only detected in K1 isolates. AllS and virulence determinants were significantly more prevalent in the liver abscess group than in the non-liver abscess group.

Conclusion

The prevalence of hvKP among K. pneumoniae infections of the hepatobiliary system is high in Yantai, China. Greater vigilance of hvKP infection is required in clinical and microbiological laboratories.

The Anti-Virulence Effect of Sub-Minimal Inhibitory Concentrations of Levofloxacin on Hypervirulent Klebsiella pneumoniae

Background

Hypervirulent Klebsiella pneumoniae (hvKp) is best described as a virulent pathogen and generally associated with the hypermucoviscosity phenotype. Increased capsule and aerobactin production are established important hvKp-specific virulence factors. Although hvKp strains have been relatively susceptible to antimicrobials, given the high morbidity and mortality, there is a critical need for alternative strategies for the treatment of hvKp infections. Thus, the anti-virulence therapy has been targeted for the hvKp development of therapeutics.

Materials and Methods

Four hvKp isolates with hypermucoviscous phenotype were used in our experiments. Mucoviscosity of the capsule can be assessed by low-speed centrifugation of cultures. CPS amount was determined by glucuronic acid content. The capsule thickness was measured under microscope after ink staining. The transcriptions of gene were measured by quantitative real-time PCR (qRT-PCR). The effect of levofloxacin on the resistance of K. pneumoniae to phagocytosis by macrophages and mouse lethality assay was observed.

Results

Our data revealed that sub-Minimal Inhibitory Concentrations (sub-MIC) of LVX reduce mucoviscosity and CPS production of hvKp. Microscopic observations demonstrated that the capsule of hvkp bacteria became thinned after treatment with LVX. qRT-PCR showed decreased transcript levels of rmpA, wzi, magA, iroN and icuA genes. Down-regulation of these virulence genes occurred leading to increased susceptibility to phagocytosis by macrophages. Mouse lethality assay revealed that the wild strain had the LD50 of 10³ CFU, while the sub-MIC LVX-treated bacteria had the LD50 of 10⁵ CFU.

Conclusion

Our data suggested that LVX may serve as a potential anti-virulence agent for refractory infection by hvKp.

Gastric heterotopia of colon found cancer workup in liver abscess: A case report

BACKGROUND

Recently reported cases of pyogenic liver abscess associated with colonic cancer in the absence of underlying disease, have included a small number of cases of gastric heterotopia (GHT). GHT is a congenital anomaly composed of ectopic gastric mucosa and can occur anywhere in the gastrointestinal tract but is more frequently encountered in the cervical esophagus. However, it is rarely observed in colon. Furthermore, most reported cases of GHT of the colon involved the rectum, and GHT involving the colon proximal to the rectum is rare.

CASE SUMMARY

An 83-year-old male patient presented with fever and a diagnosis of pyogenic liver abscess. Colonoscopy was performed for colon cancer workup and revealed a 1.0 cm sized polyp at the transverse colon. The polyp was removed by endoscopic mucosal resection by monopolar electrocauterization using a snare. Pathological examination revealed GHT. After administering intravenous antibiotics, the patient recovered well.

CONCLUSION

GHT in the colon could affect the development of pyogenic liver abscess by enabling hematogenous propagation of Klebsiella pneumoniae through mucosal damage. However, more study is needed due to the lack of cases.

Determination of extended-spectrum β-lactamase-producing Klebsiella pneumoniae isolated from horses with respiratory manifestation

Background and Aim:

The World Health Organization considers multidrug-resistant (MDR) Klebsiella pneumoniae a major global threat. Horses harbor commensal isolates of this bacterial species and potentially serve as reservoirs for human MDR bacteria. This study investigated antimicrobial resistance in horses caused by extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae.

Materials and Methods:

One hundred fifty-nine nasal swab samples were collected from horses with respiratory distress not treated with cefotaxime and erythromycin. Biochemical and serological identification was performed on all samples. Polymerase chain reaction (PCR) was used to detect 16S-23S ITS, mucoviscosity-associated gene (magA), uridine diphosphate galacturonate 4-epimerase gene (uge), and iron uptake system gene (kfu), bla_TEM, bla_SHV, and bla_CTX genes. Sequence analysis and phylogenetic relatedness of randomly selected K. pneumoniae isolates carrying the bla_TEM gene were performed.

Results:

Ten isolates of Klebsiella spp. were obtained from 159 samples, with an incidence of 6.28% (10 of 159). Based on biochemical and serological identification, K. pneumoniae was detected in 4.4% (7 of 159) of the samples. Using PCR, all tested K. pneumoniae isolates (n=7) carried the 16S-23S ITS gene. By contrast, no isolates carried magA, uge, and kfu genes. The bla_TEM gene was detected in all test isolates. Moreover, all isolates did not harbor the bla_SHV or bla_CTX gene. Sequence analysis and phylogenetic relatedness reported that the maximum likelihood unrooted tree generated indicated the clustering of the test isolate with the other Gram-negative isolate bla_TEM. Finally, the sequence distance of the bla_TEM gene of the test isolate (generated by Lasergene) showed an identity range of 98.4-100% with the bla_TEM gene of the different test isolates.

Conclusion:

The misuse of antimicrobials and insufficient veterinary services might help generate a population of ESBL-producing K. pneumoniae in equines and humans, representing a public health risk.

Emphysematous Liver Abscess and Disseminated Hypervirulent Klebsiella pneumoniae Infection in a Patient from Southern India

The pyogenic liver abscess is usually polymicrobial and is seen as a complication of biliary disease or peritonitis. Over the past three decades, monomicrobial liver abscess caused by Klebsiella pneumoniae is being increasingly reported from South East Asian countries like Taiwan and Korea. It is a community-acquired infection caused by a distinct strain, hypervirulent K. pneumoniae, different from classical strain related to the healthcare-associated Klebsiella infections. Diabetes mellitus is a significant risk factor. Reports of the disseminated infection due to hypervirulent Klebsiella are very few in Indian literature. We report the successful management of a diabetic patient with emphysematous liver abscess, brain abscess, and meningitis caused by hypervirulent K. pneumoniae infection.

Multi-system Klebsiella sepsis: A tale of destruction form lung to eye

Klebsiella pneumoniae, found in the gastrointestinal flora is a causative agent of hospital-acquired infections. Although isolated organ infections are common, reports of multi-system involvement are rare. We report on a susceptible patient presenting with disseminated Klebsiella infection with concurrent multi-organ disease involving the lung, liver, prostate and eye. He recovered after prolonged therapy but suffered from permanent sequalae. Early diagnosis and aggressive therapy is facilitated by awareness and a high degree of suspicion in at-risk patient groups.

A population-based study of pyogenic liver abscess in Korea: Incidence, mortality and temporal trends during 2007-2017

BACKGROUND/AIMS

Although the epidemiology of pyogenic liver abscess (PLA) continues to change, only a few population-based studies have been conducted in Korea. This study investigated the epidemiology and clinical outcomes of PLA patients during a period of 10 years.

METHODS

We analysed the Health Insurance Review and Assessment Service data between 2007 and 2017. The data included annual incidence rates, demographic data, underlying diseases, complications and mortality of PLA patients.

RESULTS

The annual incidence of PLA for all age groups was 10.9 per 100 000 population. The incidence was gradually increased from 5.7 per 100 000 in 2007 to 14.4 per 100 000 in 2017. In patients with liver abscess, the prevalence of diabetes and malignancy were 37.24% and 26.5% respectively. Metastatic infection was reported in 1.74% of the patients, and endophthalmitis was most common. The mean in-hospital mortality was 9.6%, and there was no significant difference in mortality by year during the observation period. Mortality increased with age and was greatly affected by the underlying diseases, especially cancer. Based on the multivariate analysis results, the mortality of PLA patients was associated with older age, female sex, diabetes, malignancy and chronic kidney disease.

CONCLUSION

The PLA incidence is rapidly increasing in Korea, especially in people with comorbidities. In addition, the causes and risk factors of PLA infections are changing and thus further research on epidemiology, different diagnosis and management approaches is required.

Gut Microbiota Contributes to Host Defense Against Klebsiella pneumoniae-Induced Liver Abscess

Purpose

Klebsiella pneumoniae-induced liver abscess (KLA) is a type of pyogenic liver abscess (PLA), which is a distinct invasive syndrome that has been increasingly reported worldwide over the past two decades. The intestinal microbiota is increasingly recognized as an important modulator that can promote and maintain host immune homeostasis. However, its precise role in liver abscess is unknown. We aimed to investigate the function of the gut microbiota in the host defense against K. pneumoniae infection.

Methods

We constructed C57BL/6J mice with KLA and analyzed the diversity and richness of the intestinal microflora by 16S rRNA sequencing. Next, to create a microbiota-depleted (MD) mouse model, we administered multiple broad-spectrum antibiotics and validated the model using 16S rRNA sequencing. At 48 h after K. pneumoniae infection, we assessed the general health condition, liver injury, bacterial loads, and inflammatory factor levels in MD+KLA mice. Additionally, fecal microbiota transplantation (FMT) was conducted in another group of MD+KLA mice prior to K. pneumoniae infection, and we assessed whether the transplantation changed the outcomes.

Results

The diversity of the intestinal flora was significantly changed in KLA mice compared to control mice, with a decrease in beneficial bacteria and an increase in harmful bacteria. The MD+KLA mice exhibited impaired antimicrobial capacity, reduced survival, increased inflammation and liver damage at 48 h after K. pneumoniae infection compared to the KLA mice. However, FMT normalized the inflammatory cytokine levels, reduced liver damage, and increased survival.

Conclusion

This study identified the gut microbiota as a protective factor against K. pneumoniae infection. The role of FMT in KLA should be investigated in future clinical studies.

Identification and Evaluation of Recombinant Outer Membrane Proteins as Vaccine Candidates Against Klebsiella pneumoniae

Klebsiella pneumoniae found in the normal flora of the human oral and intestinal tract mainly causes hospital-acquired infections but can also cause community-acquired infections. To date, most clinical trials of vaccines against K. pneumoniae have ended in failure. Furthermore, no single conserved protein has been identified as an antigen candidate to accelerate vaccine development. In this study, we identified five outer membrane proteins of K. pneumoniae, namely, Kpn_Omp001, Kpn_Omp002, Kpn_Omp003, Kpn_Omp004, and Kpn_Omp005, by using reliable second-generation proteomics and bioinformatics. Mice vaccinated with these five KOMPs elicited significantly higher antigen-specific IgG, IgG1, and IgG2a. However, only Kpn_Omp001, Kpn_Omp002, and Kpn_Omp005 were able to induce a protective immune response with two K. pneumoniae infection models. These protective effects were accompanied by the involvement of different immune responses induced by KOMPs, which included KOMPs-specific IFN-γ-, IL4-, and IL17A-mediated immune responses. These findings indicate that Kpn_Omp001, Kpn_Omp002, and Kpn_Omp005 are three potential Th1, Th2, and Th17 candidate antigens, which could be developed into multivalent and serotype-independent vaccines against K. pneumoniae infection.

Community-acquired Klebsiella spp Meningitis/Invasive Infection in Filipino-descent Patients Living in Greece: A Case Series

Klebsiella spp community-acquired meningitis caused by hypervirulent strains is well described as part of a distinct syndrome consisting of liver abscess and multiple septic metastatic lesions (Klebsiella pneumoniae invasive syndrome) occurring usually in diabetic, alcoholic, elderly or cancer patients, in Taiwan and other South-East Asian countries. In Western countries, these infections are very rare in natives and usually occur in patients of Asian origin. We report three cases of Filipino-origin patients, residents of Greece, with community-acquired invasive Klebsiella meningitis, who were treated in our ICU over a 10-year period.

Hypervirulent Klebsiella pneumoniae Endogenous Endophthalmitis-A Global Emerging Disease

The review aims to document the new emerging hypervirulent Klebsiella pneumoniae (Kp) endogenous endophthalmitis (EKE) in terms of incidence, microbiological characterization of the pathogenic agent, associated risk factors, management, and outcomes. Hypervirulent (hv) strains of KP (hvKp) induce invasive liver abscesses (LA) with specific clinical features. Up to 80–90% of cases have hepatic liver abscess as a primary focus of infection, followed by renal or lung hvKp infections. However, the incidence of EKE in patients with KPLA varied between 3.4% (19) and 12.6% (13), with a total of 95 cases of endophthalmitis in 1455 cases of KPLA (6.5%). Severe visual loss was encountered in 75% of cases, with 25% bilateral involvement. Intravitreal antibiotics are the mainstay therapeutic approach. Pars plana vitrectomy is a subject of controversy. HvKp strains present mostly natural “wild-type” antibiotic resistance profile suggestive for community-acquired infections, being highly susceptive to the third and fourth generation of cephalosporins and carbapenems. Antimicrobial resistance in hypervirulent strains was recently documented via plasmid transfer and may result in extremely difficult to treat cases. Global dissemination of these strains is a major epidemiologic shift that should be considered in the diagnostic and therapeutic management of patients with endogenous endophthalmitis. Ophthalmologic screening in patients with KPLA and other hvKp infections and a multidisciplinary therapeutic approach is extremely important for early diagnosis and preservation of the visual function.

Bacterial extracellular vesicles: Understanding biology promotes applications as nanopharmaceuticals

Extracellular vesicle (EV)-mediated communication between proximal and distant cells is a highly conserved characteristic in all of the life domains, including bacteria. These vesicles that contain a variety of biomolecules, such as proteins, lipids, nucleic acids, and small-molecule metabolites play a key role in the biology of bacteria. They are one of the key underlying mechanisms behind harmful or beneficial effects of many pathogenic, symbiont, and probiotic bacteria. These nanoscale EVs mediate extensive crosstalk with mammalian cells and deliver their cargos to the host. They are stable in physiological condition, can encapsulate diverse biomolecules and nanoparticles, and their surface could be engineered with available technologies. Based on favorable characteristics of bacterial vesicles, they can be harnessed for designing a diverse range of therapeutics and diagnostics for treatment of disorders including tumors and resistant infections. However, technical limitations for their production, purification, and characterization must be addressed in future studies.

Clinical evolution of ST11 carbapenem resistant and hypervirulent Klebsiella pneumoniae

Carbapenem-resistant and hypervirulent K. pneumoniae (CR-HvKP) strains that have emerged recently have caused infections of extremely high mortality in various countries. In this study, we discovered a conjugative plasmid that encodes carbapenem resistance and hypervirulence in a clinical ST86 K2 CR-HvKP, namely 17ZR-91. The conjugative plasmid (p17ZR-91-Vir-KPC) was formed by fusion of a non-conjugative pLVPK-like plasmid and a conjugative bla_KPC-2-bearing plasmid and is present dynamically with two other non-fusion plasmids. Conjugation of p17ZR-91-Vir-KPC to other K. pneumoniae enabled them to rapidly express the carbapenem resistance and hypervirulence phenotypes. More importantly, genome analysis provided direct evidence that p17ZR-91-Vir-KPC could be directly transmitted from K2 CR-HvKP strain, 17ZR-91, to ST11 clinical K. pneumoniae strains to convert them into ST11 CR-HvKP strains, which explains the evolutionary mechanisms of recently emerged ST11 CR-HvKP strains.

Carbapenem-resistant and hypervirulent Klebsiella pneumoniae strains are emerging. Here Xie et al. show that these phenotypes are carried on a plasmid formed from the fusion of a virulence plasmid with a conjugative plasmid.

Rare case of endogenous Klebsiella endophthalmitis associated with emphysematous prostatitis in a patient with diabetes, cirrhosis and COVID-19

A 35-year-old Hispanic man presented with fever, chills, dysuria, diarrhoea, scleral icterus, tachycardia and tachypnea. He was found to be COVID-19 positive, CT of the pelvis revealed prostatic abscess, and urine culture grew Klebsiella pneumoniae Additionally, he was found to have diabetes and cirrhosis. During treatment, the patient developed vision loss, and was diagnosed with endogenous Klebsiella endophthalmitis. The patient was treated with intravenous antibiotics, pars plana vitrectomy, intravitreal antibiotics and cystoscopy/suprapubic catheter placement. On follow-up, the patient has had the suprapubic catheter removed, and successfully passed a voiding trial, but suffers permanent vision loss in both eyes.

First evidence of Klebsiella pneumoniae infection in Aceh cattle: Pathomorphology and antigenic distribution in the lungs

BACKGROUND AND AIM

Klebsiella pneumoniae is an emerging zoonotic and foodborne pathogen worldwide. Hypervirulent K. pneumoniae (hvKp) was reported as the causative agent of bovine mastitis. This is the first study in Indonesia that has been conducted to determine the capsular serotype of K. pneumoniae, pulmonary gross pathology and histopathology, and distribution of hvKp in the lungs of Aceh cattle.

MATERIALS AND METHODS

The presence of K. pneumoniae in Aceh cattle was investigated in two slaughterhouses in Banda Aceh and Aceh Besar, Indonesia. Lung tissues with gross pathological lesions were collected from 15 cattle presenting with depression, dehydration, or cachexia. The confirmation and capsular serotyping of K. pneumoniae isolates were performed using polymerase chain reaction. The tissues were stained with hematoxylin-eosin and immunohistochemistry to observe the histopathological lesions and the distribution of the hvKp antigens.

RESULTS

The pneumonic lesions identified in the lungs of Aceh cattle included hyperemia, hemorrhage, consolidation, and atelectasis. K. pneumoniae was isolated in all 15 lung tissues with pathological pneumonic lesions. Two patterns of infection were observed histopathologically. Acute infection was characterized by hyperemia, inflammatory cell infiltration, hemorrhage, bronchiolar epithelium hyperplasia, bronchial and bronchiolar obstruction with purulent exudates, edema, and atelectasis. On the other hand, chronic infection was defined by macrophage infiltration, emphysema, bronchial dilatation, pleural fibrosis, and alveolar wall thickening by interstitial fibrosis. Immunohistochemical staining using monospecific antisera induced by the hvKp isolate confirmed the presence of K. pneumoniae-specific antigens in the acute infection, predominantly in the bronchiolar, vascular, and alveolar areas. In contrast, generally diffuse infiltrates were found in the pleura and interstitial alveolar areas in chronic infection.

CONCLUSION

hvKp can be detected in the lungs of Aceh cattle, representing acute and chronic infections. The distribution of Klebsiella antigens in the lung tissue was consistent with the histopathological findings.

Klebsiella pneumoniae liver abscess with endophthalmitis in a diabetic man with gallstones

Invasive liver abscess syndrome (ILAS) is caused by Klebsiella pneumoniae and is typically seen in people from East Asia, often with diabetes and gallstones. ILAS includes metastatic sequelae of the infection, commonly to the eyes. The case described below occurred in a London hospital. The patient's abscess was diagnosed on CT and MRI and he developed endophthalmitis secondary to metastatic spread of the infection. He was treated with intravenous and intravitreal antibiotics and discharged with a plan for vitrectomy and cholecystectomy as an outpatient. We discuss the epidemiology, risk factors, pathogenesis, prognosis and management of this rare condition. There have been a number of recent reports of cases of this nature outside of Asia and we believe greater awareness is required. A high index of suspicion should be held for the potential development of metastases in patients of this demographic presenting with abscesses of this nature.

The Changing Face of the Family Enterobacteriaceae (Order: "Enterobacterales"): New Members, Taxonomic Issues, Geographic Expansion, and New Diseases and Disease Syndromes

The family Enterobacteriaceae has undergone significant morphogenetic changes in its more than 85-year history, particularly during the past 2 decades (2000 to 2020). The development and introduction of new and novel molecular methods coupled with innovative laboratory techniques have led to many advances. We now know that the global range of enterobacteria is much more expansive than previously recognized, as they play important roles in the environment in vegetative processes and through widespread environmental distribution through insect vectors. In humans, many new species have been described, some associated with specific disease processes. Some established species are now observed in new infectious disease settings and syndromes. The results of molecular taxonomic and phylogenetics studies suggest that the current family Enterobacteriaceae should possibly be divided into seven or more separate families. The logarithmic explosion in the number of enterobacterial species described brings into question the relevancy, need, and mechanisms to potentially identify these taxa. This review covers the progression, transformation, and morphogenesis of the family from the seminal Centers for Disease Control and Prevention publication (J. J. Farmer III, B. R. Davis, F. W. Hickman-Brenner, A. McWhorter, et al., J Clin Microbiol 21:46-76, 1985, https://doi.org/10.1128/JCM.21.1.46-76.1985) to the present.

Maximal diameter of liver abscess independently predicts prolonged hospitalization and poor prognosis in patients with pyogenic liver abscess

Background/aims

This study aimed to investigate the factors associated with prolonged hospital stay and in-hospital mortality in patients with pyogenic liver abscess.

Methods

We retrospectively reviewed data from patients with pyogenic liver abscess who were admitted between 2005 and 2018 at three tertiary hospitals in Jeonbuk province, South Korea. Prolonged hospital stay was defined as a duration of hospital admission of more than 21 days.

Results

A total of 648 patients (406 men and 242 women) diagnosed with pyogenic liver abscess were enrolled in the study. The mean maximal diameter of the liver abscess was 5.4 ± 2.6 cm, and 74.9% of the lesions were single. The three groups were divided according to the maximal diameter of the abscess. Laboratory parameters indicated a more severe inflammatory state and higher incidence of complications and extrahepatic manifestations with increasing abscess size. Rates of percutaneous catheter drainage (PCD) insertion, multiple PCD drainage, and salvage procedures as well as duration of drainage were also higher in the large liver abscess group. Of note, the duration of hospitalization and in-hospital mortality were significantly higher in the large hepatic abscess group. A multivariate analysis revealed that underlying diabetes mellitus, hypoalbuminemia, high baseline high-sensitivity C-reactive protein (hs-CRP) and procalcitonin levels, and large maximal abscess diameter were independent factors associated with prolonged hospital stay. Regarding in-hospital mortality, acute kidney injury at admission and maximal diameter of the abscess were independent factors associated with in-hospital mortality.

Conclusions

A large maximal diameter of the liver abscess at admission indicated prolonged hospitalization and poor prognosis. More aggressive treatment strategies with careful monitoring are warranted in patients with large liver abscesses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-05873-7.