Cryptogenic invasive Klebsiella pneumoniae liver abscess syndrome

A Nomogram Based on a Non-Invasive Method to Distinguish Between Gram-Positive and Gram-Negative Bacterial Infections of Liver Abscess

Purpose

The diagnosis of liver abscess (LA) caused by Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB) depends on ultrasonography, but it is difficult to distinguish the overlapping features. Valuable ultrasonic (US) features were extracted to distinguish GPB-LA and GNB-LA and establish the relevant prediction model.

Materials and Methods

We retrospectively analyzed seven clinical features, three laboratory indicators and 11 US features of consecutive patients with LA from April 2013 to December 2023. Patients with LA were randomly divided into training group (n=262) and validation group (n=174) according to a ratio of 6:4. Univariate logistic regression and LASSO regression were used to establish prediction models. The performance of the model was evaluated using area under the curve(AUC), calibration curves, and decision curve analysis (DCA), and subsequently validated in the validation group.

Results

A total of 436 participants (median age: 55 years; range: 42-68 years; 144 women) were evaluated, including 369 participants with GNB-LA and 67 with GPB-LA, respectively. A total of 11 predictors by LASSO regression analysis, which included gender, age, the liver background, internal gas bubble, echogenic debris, wall thickening, whether the inner wall is worm-eaten, temperature, diabetes mellitus, hepatobiliary surgery and neutrophil(NEUT). The performance of the Nomogram prediction model distinguished between GNB-LA and GPB-LA was 0.80, 95% confidence interval [CI] (0.73-0.87). In the validation group, the AUC of GNB was 0.79, 95% CI (0.69-0.89).

Conclusion

A model for predicting the risk of GPB-LA was established to help diagnose pathogenic organism of LA earlier, which could help select sensitive antibiotics before the results of drug-sensitive culture available, thereby shorten the treatment time of patients.

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.

Klebsiella Endogenous Endophthalmitis During the COVID-19 Pandemic

Purpose: To describe the characteristics of Klebsiella pneumoniae endogenous endophthalmitis (KEE) encountered during the COVID-19 pandemic. Methods: This retrospective consecutive case series evaluated eyes that presented with KEE between March 2020 and July 2022. Results: Seven eyes of 5 patients developed KEE. Between January 2020 and July 2022, KEE was observed in 42% of consecutive EE cases compared with 7.8% during the preceding 13 years. COVID-19 was positive in 4 of 5 patients before they developed KEE. Only 1 patient presented with a VA better than hand motions (20/400). All eyes were treated with urgent vitrectomy and intravitreal and systemic antibiotics. No improvement in vision occurred in any patient; VA remained light perception to no light perception in 60% of eyes. Conclusions: The visual prognosis in KEE is extremely poor. The presence of a preceding COVID-19 infection in 80% of patients may signal a new risk factor for KEE. Patients with a hypervirulent Klebsiella syndrome should be routinely screened for EE.

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.

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.

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.

A Rare Case of Ascariasis-Induced Cholangitis Complicated With Klebsiella pneumoniae Bacteremia and Liver Microabscesses

Ascariasis, which is caused by Ascaris lumbricoides, is the most common gastrointestinal parasitic infection worldwide, with occasional invasion of the biliary tract leading to a variety of complications. In rare cases, pathogens carried on the surface of A. lumbricoides can complicate the course of the disease and lead to superimposed bacterial infections. In this article, we present a case of ascariasis-induced cholangitis complicated with Klebsiella pneumoniae bacteremia and multiple hepatic microabscesses. This article, which shows an association that was not reported in the literature before, aims to increase the awareness of clinicians for the possibility of the association between ascariasis and superimposed bacterial infection, specifically with K. pneumoniae.

A retrospective study of pyogenic liver abscess caused primarily by Klebsiella pneumoniae vs. non-Klebsiella pneumoniae: CT and clinical differentiation

PURPOSE

The incidence of Klebsiella pneumoniae pyogenic liver abscesses (KP-PLA) is increasing. However, its diagnosis and treatment are often delayed, leading to complications. In this study, we aimed to retrospectively compare computed tomographic (CT) features of KP-PLAs with those of abscesses caused by other bacterial pathogens (non-KP-PLAS) and to further identify prognostic factors for PLA.

METHODS

Data of 219 study patients including clinical presentation, comorbid conditions, metastatic infection, treatment duration, and mortality were retrospectively collated. CT characteristics of abscesses were recorded. Etiology was established by pus and/or blood culture. The differentiating CT features and clinical findings were compared between the monomicrobial KP-PLA and non-KP-PLA groups. Furthermore, factors related to in-hospital case fatality were analyzed.

RESULTS

Multivariate analysis identified thin-walled abscesses, absent rim enhancement, metastatic infection, and absence of underlying biliary tract disease as significant predictors of KP-PLA. With 3/4 criteria applied in combination, a specificity of 96.5% was achieved for KP-PLA diagnosis. The in-hospital mortality rate was 3.7%. Multivariate analysis revealed that diabetes mellitus (P = 0.031), multiple abscesses (P = 0.026), internal gas bubble (P = 0.041), metastatic infection (P = 0.004), and septic shock (P = 0.002) were significantly associated with mortality.

CONCLUSION

Thin-walled abscess, metastatic infection, absence of rim enhancement, and absence of underlying biliary tract disease are potentially useful CT findings for early KP-PLA diagnosis.

Klebsiella pneumoniae Multiple Liver Abscesses and Bacteremia in a Transfusion-dependent β Thalassemia Major Patient

β thalassemia major is a common hemoglobinopathy in Sri Lanka. Klebsiella pneumoniae (KP) is a Gram-negative capsulated organism responsible for various nosocomial and community-acquired infections. Transfusion-dependent splenectomized thalassemia patients are at risk of infections. Liver abscess is an infection to suspect in such patients, and, among the organisms, KP is an organism to watch out for. Furthermore, KP could cause multiple liver abscesses, which makes it difficult to treat, as it cannot be drained. We report a 16-year-old splenectomized transfusion-dependent thalassemia major patient who presented with multiple liver abscesses with KP bacteremia.

Contrast-Enhanced Ultrasound Appearance of Hypervirulent Klebsiella pneumoniae Liver Abscesses

There has been a paradigm shift with Klebsiella pneumoniae (KP) emerging as the most frequently isolated bacterium in pyogenic liver abscesses in immunocompetent patients. Colonization of this hypervirulent KP strain has led to community-acquired liver abscesses. Septic seeding to distant sites of the body has been recognized and is strongly associated with diabetes. Contrast-enhanced computed tomographic features have been described. Grayscale ultrasound (US) features remain inconclusive, with variable US appearances. Here we describe the contrast-enhanced US features of KP liver abscesses, which correlated with previously described computed tomographic findings. The use of contrast-enhanced US eliminates the need for radiation exposure.

Perinatal Pyogenic Liver Abscess: A Rare Entity and First Reported Case of Klebsiella pneumoniae

Introduction  Pyogenic liver abscess (PLA) is a rare clinical entity, occurring in ∼2.3 per 100,000 patients. Perinatal PLA syndromes are exceedingly rare with just seven previously described cases in the literature and no prior Klebsiella-associated reports. Case  A 29-year-old gravida 2 para 1 woman at 11 weeks gestation reporting fever, body aches, and headache. Search for an infectious source identified a 4-cm liver abscess. Percutaneous drainage confirmed Klebsiella pneumoniae infection. The patient was treated with antibiotics until imaging verified complete resolution of the abscess. Conclusion  PLA is an uncommon etiology of sepsis in pregnancy. A thorough workup until a source was identified resulted in accurate diagnosis. This allowed for directed therapy and prompt recovery, undoubtedly contributing to favorable pregnancy outcomes in this first report of Klebsiella-associated perinatal PLA.

Hypervirulent Klebsiella pneumoniae in Cryptogenic Liver Abscesses, Paris, France

Liver abscesses containing hypervirulent Klebsiella pneumoniae have emerged during the past 2 decades, originally in Southeast Asia and then worldwide. We hypothesized that hypervirulent K. pneumoniae might also be emerging in France. In a retrospective, monocentric, cohort study, we analyzed characteristics and outcomes for 199 consecutive patients in Paris, France, with liver abscesses during 2010-2015. We focused on 31 patients with abscesses containing K. pneumoniae. This bacterium was present in most (14/27, 52%) cryptogenic liver abscesses. Cryptogenic K. pneumoniae abscesses were more frequently community-acquired (p<0.00001) and monomicrobial (p = 0.008), less likely to involve cancer patients (p<0.01), and relapsed less often (p<0.01) than did noncryptogenic K. pneumoniae liver abscesses. K. pneumoniae isolates from cryptogenic abscesses belonged to either the K1 or K2 serotypes and had more virulence factors than noncryptogenic K. pneumoniae isolates. Hypervirulent K. pneumoniae are emerging as the main pathogen isolated from cryptogenic liver abscesses in the study area.

Identification and Management of the Hypervirulent Invasive Klebsiella pneumoniae Syndrome: A Unique and Distinct Clinical Entity

In this article, we describe the case of a 61-year-old woman who presented with altered mental status and was found to have Klebsiella pneumoniae meningitis, bacteremia, and hepatic abscess. Despite intravenous antibiotic therapy and percutaneous drainage of the hepatic abscess, the patient developed worsening meningitis with ventriculitis, which led to her death. This invasive Klebsiella syndrome is characterized by metastatic infections with a hypervirulent strain and a poor clinical prognosis. Important elements of this patient’s case—including the widespread and highly aggressive course—and of those reported in the literature are reviewed. Although the invasive Klebsiella syndrome is an increasingly recognized clinical entity, most often in the Eastern hemisphere, it remains rare in the United States with approximately 20 cases reported in the literature, and given its high morbidity, it is vitally important for clinicians to recognize.

Cryptogenic and non-cryptogenic liver abscess: A retrospective analysis of 178 cases revealed distinct characteristics

Objective

To enhance theoretical support of pyogenic liver abscess (PLA) treatment by comparing characteristics of patients with either PLA with an identified infectious origin (non-cryptogenic) or PLA with no obvious underlying cause (cryptogenic).

Methods

This retrospective study included all first episodes of PLA in adults admitted to a tertiary hospital between 2009 and 2016. Relevant clinical data were collected for patients with cryptogenic or non-cryptogenic PLA and compared across a number of characteristics.

Results

In all, 178 patients were included: 111 cases (62.4%) of cryptogenic PLA, and 67 cases (37.6%) of non-cryptogenic PLA. Diabetes mellitus was significantly more prevalent in patients with cryptogenic PLA than those with non-cryptogenic PLA. The proportion of multidrug resistance/poly-microbial infection was significantly lower and Klebsiella pneumoniae infection was significantly higher in the cryptogenic versus non-cryptogenic PLA group. Metastatic infection occurred in four patients with cryptogenic PLA only, and all had diabetes and K. pneumoniae infection. Multivariate logistic regression analysis revealed that male sex, diabetes and K. pneumoniae were independent predictors for cryptogenic PLA.

Conclusions

Cryptogenic and non-cryptogenic PLA have distinctly different characteristics, suggesting a potential need for different treatment approaches.

Metabolic Characterization of Peripheral Host Responses to Drainage-Resistant Klebsiella pneumoniae Liver Abscesses by Serum 1H-NMR Spectroscopy

Purpose: To explore the metabolic characterization of host responses to drainage-resistant Klebsiella pneumoniae liver abscesses (DRKPLAs) with serum 1H-nuclear magnetic resonance (NMR) spectroscopy.

Materials and Methods: The hospital records of all patients with a diagnosis of a liver abscess between June 2015 and December 2016 were retrieved from an electronic hospital database. Eighty-six patients with Klebsiella pneumoniae (K. pneumoniae) liver abscesses who underwent percutaneous drainage were identified. Twenty patients with confirmed DRKPLAs were studied. Moreover, we identified 20 consecutive patients with drainage-sensitive Klebsiella pneumoniae liver abscesses (DSKPLAs) as controls. Serum samples from the two groups were analyzed with 1H NMR spectroscopy. Partial least squares discriminant analysis (PLS-DA) was used to perform 1H NMR metabolic profiling. Metabolites were identified using the Human Metabolome Database, and pathway analysis was performed with MetaboAnalyst 3.0.

Results: The PLS-DA test was able to discriminate between the two groups. Five key metabolites that contributed to their discrimination were identified. Glucose, lactate, and 3-hydroxybutyrate were found to be upregulated in DRKPLAs, whereas glutamine and alanine were downregulated compared with the DSKPLAs. Pathway analysis indicated that amino acid metabolisms were significantly different between the DRKPLAs and the DSKPLAs. The D-glutamine and D-glutamate metabolisms exhibited the greatest influences.

Conclusions: The five key metabolites identified in our study may be potential targets for guiding novel therapeutics of DRKPLAs and are worthy of additional investigation.

Culture-independent analysis of liver abscess using nanopore sequencing

The identification of microbial species has depended predominantly upon culture-based techniques. However, the difficulty with which types of organisms are cultured implies that the grown species may be overrepresented by both cultivation and plate counts. In recent years, culture-independent analysis using high-throughput sequencing has been advocated for use as a point-of-care diagnostic tool. Although it offers a rapid and unbiased survey to characterize the pathogens in clinical specimens, its accuracy is reduced by the high level of contamination of human DNA. In this paper, we propose using a culture-independent analysis for a Klebsiella pneumoniae clinical strain within a liver abscess using nanopore sequencing. Owing to the highly-contaminated cell population within a liver abscess, we managed to reduce the confounding effects of human DNA through the use of DNase and differential centrifugation. Genomic DNA was sequenced through the use of Nanopore MinION sequencer and analyzed using a suite of bioinformatics approaches. K. pneumoniae was successfully identified along with antibiotic-resistant genes. Our results indicate that, by integrating real-time nanopore sequencing and bioinformatics software, real-time pathogen identification in a liver abscess can be achieved.

Computed Tomography Features of Septic Pulmonary Embolism Caused by Klebsiella pneumoniae Liver Abscess Associated With Extrapulmonary Metastatic Infection

OBJECTIVES

The aims of the study were to investigate the computed tomography (CT) features and clinical course of septic pulmonary embolism (SPE) caused by Klebsiella pneumoniae liver abscess (KPLA) and to explore the possible mechanism underlying the spread of infection.

METHODS

Twenty-one patients with KPLA-induced SPE admitted to our hospital between January 2010 and May 2015 were evaluated. According to the presence or absence of extrapulmonary metastatic infection (EMI), they were divided into EMI and non-EMI groups and clinical and CT features of the 2 groups were compared. Hepatic vein thrombophlebitis was evaluated on liver CT images. Chest CT features included nodules, wedge-shaped lesions, ground-glass opacity, consolidation, cavitation, feeding vessel sign, pleural effusion, and lymphadenopathy.

RESULTS

All the vessels within the so-called feeding vessel sign were confirmed as pulmonary veins by multiplanar reconstruction, so we used an alternative name draining vessel sign (DVS) instead. Peripheral nodules, DVS, and consolidation were the main CT features of KPLA-induced SPE. Peripheral nodules and DVS were more frequently seen in the EMI group than in the non-EMI group (P = 0.019 and 0.008, respectively). Five of 8 patients with hepatic vein thrombophlebitis had lung consolidation, whereas only 3 of 13 patients without hepatic vein thrombophlebitis had lung consolidation, although the difference was not significant (P = 0.09).

CONCLUSIONS

Multiple pulmonary nodules and DVS were associated with EMI. Hepatic and pulmonary vein invasion are possible causes underlying the metastatic spread of infection.

Klebsiella pneumonia liver abscess syndrome: Case presentation to a college student health clinic

The authors describe a case of Klebsiella pneumoniae liver abscess (KPLA) in a student presenting to a university student health center. The authors also provide a review of KPLA and invasive Klebsiella pneumoniae liver abscess syndrome (IKPLAS), including epidemiology, common clinical manifestations, standard diagnostic work-up, management options, and potential complications.

Pyogenic Liver Abscess: A Retrospective Study of 105 Cases in an Emergency Department from East China

BACKGROUND

Pyogenic liver abscesses have become common in emergency departments (EDs) in recent years in Shanghai, China due to a variety of risk factors contributory to the disease.

OBJECTIVE

To review our experience in managing pyogenic liver abscesses to aid in the current management of this complex condition.

METHODS

This retrospective study was conducted to collect and analyze information from adult patients diagnosed with liver hepatic abscesses who were admitted to Ren Ji Hospital during the period from January 1, 2010 to December 31, 2015. The demographic data, etiology, underlying diseases, clinical presentation, imaging features, laboratory examinations, microbiological tests, treatment, and clinical outcomes were analyzed.

RESULTS

The data of a total 105 patients were retrospectively analyzed. The mean age of the patients was 62.0 ± 13.5 years. The etiology was predominantly hepatobiliary disease (43/105, 40.1%) or diabetes mellitus (42/105, 40.0%). During hospitalization, 12 patients (11.4%) with septic shock required intensive care. One patient died, yielding a 0.9% fatality rate. In addition to empiric antimicrobial therapy, 66/105 (62.9%) patients underwent ultrasound-guided percutaneous drainage of the liver abscess at diagnosis. Only 3 patients required surgical intervention. Bacterial culture of pyogenic fluids revealed 25 positive results of 66 cases (37.9%). Among them, Klebsiella pneumoniae was the primary pathogen detected in 15 cases (60.0%).

CONCLUSIONS

Pyogenic liver abscesses have become common in EDs in Shanghai, China. The early recognition of the disease, prompt use of empirical antimicrobial therapy, initiation of drainage in the appropriate patients, and controlling the underlying conditions were crucial for preventing severe sepsis and improving the outcome.

Klebsiella pneumoniae Liver Abscess: An Emerging Disease

Most of the cases of Klebsiella pneumoniae liver abscess reported early on were from Asia, predominantly Taiwan, with a significant number of patients being middle aged diabetic men, and developing metastatic complications, especially endophthalmitis. The entity is now being increasingly recognized in the United States. In this article, the authors review those reported cases, and also the literature regarding the pathophysiology of this intriguing syndrome.

Primary osteomyelitis caused by hypervirulent Klebsiella pneumoniae

Klebsiella pneumoniae is the most clinically relevant species of this genus, known to cause both community-acquired and nosocomial infections worldwide. In the past two decades, a distinct hypervirulent strain of K pneumoniae, characterised by its hypermucoviscous phenotype, has emerged as a clinically significant pathogen responsible for highly invasive infections. We present a case of osteomyelitis due to hypervirulent K pneumoniae reported in the USA. Genomic testing of the K pneumoniae isolate was performed due to the striking clinical presentation of the infection as well as the hypermucoid nature of the isolates, raising the suspicion for possible infection with the hypervirulent strain. Whole-genome sequencing and additional PCR testing demonstrated the isolate to be a K1 serotype, sequence type 23 strain expressing rmpA and rmpA2. Given the multiple reports of this pathogen causing invasive infections, clinicians should be aware of the possible presentation of metastatic and severe infection, including osteomyelitis, due to the hypervirulent strain of K pneumoniae not typical of classic K pneumoniae variants. In this Grand Round, we review the clinical features of hypervirulent K pneumoniae and its link to invasive infections, and discuss the need for improved awareness and identification of the pathogen.

[A Case of Delayed-onset Multiple Metastatic Infection following Liver Abscess]

Klebsiella pneumoniae liver abscess has a tendency to spread to distant sites early in the course of disease and to involve multiple organs synchronously. A 59-year-old male was admitted because of liver abscess accompanied by fever and abdominal pain. The patient underwent percutaneous catheter drainage and received intravenous antibiotics. Symptom relief was achieved after the treatment as well as marked reduction in the size of the abscess. Despite proper treatment of the liver abscess, however, patient developed multiple metastatic infections in a non-concurrent manner: left and right endophthalmitis, psoas abscess, and infectious spondylitis at 5, 23, 30 and 65 days after initial manifestations of liver abscess, respectively. Each infectious episode followed one another after resolution of the former one. For each episode of metastatic infections, the patient promptly underwent treatment with systemic and local antibiotics, interventional abscess drainage, and surgical treatments as needed. The patient fully recovered without sequelae after the use of intravenous antibiotics for an extended period of time. Herein, we report a case of K. pneumoniae liver abscess complicated with delayed-onset multiple metastatic infections.

Loss of hypermucoviscosity and increased fitness cost in colistin-resistant Klebsiella pneumoniae sequence type 23 strains

In this study, we investigated the effects of colistin resistance on virulence and fitness in hypermucoviscous (HV) Klebsiella pneumoniae sequence type 23 (ST23) strains. Colistin-resistant mutants were developed from three colistin-susceptible HV K. pneumoniae ST23 strains. The lipid A structures of strains were analyzed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. Changes in HV were investigated using the string test, and extracellular polysaccharide production was quantified. The expression levels of the phoQ, pmrD, pmrB, pbgP, magA, and p-rmpA2 genes, serum resistance, and biofilm-forming activity were determined. The fitness of colistin-resistant mutants compared to that of the parental strains was examined by determining the competitive index (CI). The colistin-resistant mutants exhibited reduced HV, which was accompanied by decreased formation of capsular polysaccharides (CPS) and reduced expression of genes (magA and p-rmpA2). While there was enhanced expression of pmrD and pbgP in all colistin-resistant derivatives, there were differences in the expression levels of phoQ and pmrB between strains. MALDI-TOF analysis detected the addition of aminoarabinose or palmitate to the lipid A moiety of lipopolysaccharide in the colistin-resistant derivatives. In addition, survival rates in the presence of normal human serum were decreased in the mutant strains, and CI values (0.01 to 0.19) indicated significant fitness defects in the colistin-resistant derivatives compared to the respective parental strains. In hypervirulent HV K. pneumoniae strains, the acquisition of colistin resistance was accompanied by reduced CPS production, impaired virulence, and a significant fitness cost.

Pneumonia and bacteremia in a golden-headed lion tamarin (Leontopithecus chrysomelas) caused by Klebsiella pneumoniae subsp. pneumoniae during a translocation program of free-ranging animals in Brazil

Klebsiella pneumoniae is an important emerging pathogen in humans, particularly the invasive hypermucoviscosity (HMV) phenotype. In addition, the organism is an important public health concern because of nosocomial infections and antimicrobial resistance. Nonhuman primates in captivity are susceptible to Klebsiella, particularly when a stress factor is involved. Infections vary depending on the species but can cause significant morbidity and mortality in these animals. The objective of this study was to describe a case of bronchopneumonia and bacteremia caused by Klebsiella pneumoniae in a free-ranging golden-headed lion tamarin (Leontopithecus chrysomelas) caught and maintained in quarantine during a translocation program for conservation purposes. An adult male, that had showed emaciation and apathy, was clinically examined and, despite being provided supportive therapy, died 2 days after onset of clinical signs. At postmortem examination, generalized bilateral pneumonia and pericarditis were observed. Tissue samples were fixed in 10% formalin for histology, and pulmonary tissues and cardiac blood were collected for microbiologic diagnostic procedures. Bacteria that were shown to be HMV K. pneumoniae subsp. pneumoniae strains were isolated from the pulmonary fluids and cardiac blood in pure cultures. Severe bronchopneumonia was the main pathological finding. The consequences of the confirmed presence of the HMV phenotype of K. pneumoniae subsp. pneumoniae in this wildlife species for human, animal, and ecosystem health should be determined. These results demonstrate the importance of quarantine and potential pathogen screening during wildlife translocation procedures.

Analysis of clinical and CT characteristics of patients with Klebsiella pneumoniae liver abscesses: an insight into risk factors of metastatic infection

PURPOSE

To compare the clinical and CT characteristics of patients with Klebsiella pneumoniae liver abscess (KPLA), with or without metastatic infection.

MATERIALS AND METHODS

Clinical information (age, sex, clinical symptoms, underlying disease, hematological parameters, abscess-related mortality) and CT characteristics of abscesses were analyzed to investigate associations with metastatic infection. Metastatic infections were divided into septic pulmonary embolism (SPE) and extra-pulmonary metastatic infection (EMI).

RESULTS

We identified 66 consecutive patients with KPLA. Metastatic infection occurred in 22/66 patients (33.3%); 8/66 (12.1%) patients had SPE, 6/66 (9.09%) patients had EMI; and 8/66 (12.1%) patients had both SPE and EMI. Patients with SPE were younger than patients without SPE (47.7±13.7 y vs.55.6±12.0 y; p=0.03). Unilocular abscess was significantly more common in patients with SPE than the non-SPE group (43.75% vs 18.0%, p=0.036). The mean maximal diameter of EMI was 56.5±21.3 mm and was significantly smaller than that of the non-EMI which was 79.9±31.4 (p=0.011). SPE was significantly associated with development of EMI (50% vs 17.3%, p=0.011).

CONCLUSION

Unilocular liver abscess is associated with SPE, and SPE is strongly associated with EMI among patients with KPLA. A maximal diameter of KPLA<55 mm can be used as a predictor of EMI.

Cryptogenic invasive Klebsiella pneumoniae liver abscess syndrome (CIKPLA) in Western Australia?

Virulent serotypes of Klebsiella pneumoniae are recognised to cause metastatic infections at various sites. Prevalence of this invasive syndrome has been observed worldwide with predominance in Asian series. However, reports in an Australian setting have been limited. We report two cases of fulminating community-acquired invasive Klebsiella pneumoniae liver abscess syndrome occurring in two Caucasian patients, from two different, distant suburbs in Western Australia with no known clinical comorbidities prior to the hospital presentation and no history of recent travel overseas. The interval between both admissions was 18 days, where only one patient survived.

Clinical and radiological features of invasive Klebsiella pneumoniae liver abscess syndrome

BACKGROUND

Recently, a striking new clinical manifestation of Klebsiella pneumoniae (KP) infection referred to as invasive KP liver abscess syndrome (IKPLAS), defined by liver abscess with contemporaneous metastatic KP infections at other body sites has been documented. Until now, however, there have been relatively few reports regarding its radiologic features.

PURPOSE

To describe the clinical and radiological features of IKPLAS patients, and to compare them with those with KP liver abscess without metastatic infections to ascertain possible predictors of IKPLAS.

MATERIAL AND METHODS

From January 2008 to May 2010, 35 patients (26 men and 9 women; mean age, 59.4 years) with both liver abscess and metastatic KP infections were diagnosed with IKPLAS. Their clinical and radiological features were retrospectively evaluated and compared with those of 25 contemporaneous non-metastatic patients to investigate predictive factors for metastatic infections.

RESULTS

The rate of intensive care unit admissions and overall mortality was 34.3% and 17.1% in IKPLAS patients, and was significantly higher than those of the non-metastatic group (8% and 0%, respectively). As for metastatic infections, the lung was the most common site and multiple nodules or masses (n = 9) were the most common manifestations. Univariate analysis revealed that liver abscess ≤5.8 cm, bilobar involvement of abscess and altered mentality were significantly related with IKPLAS. At multivariate analysis, liver abscess ≤5.8 cm was proven to be a significant independent predictor of IKPLAS (OR, 3.6; P = 0.038). In addition, altered mentality was present solely in IKPLAS (25.7% vs. 0%) although its P value (P = 0.052) did not reach a statistical significance at multivariate analysis.

CONCLUSION

IKPLAS has significantly worse prognosis than non-metastatic KP abscess patients. In patients with KP liver abscess, liver abscess ≤5.8 cm can be used as an independent predictor of IKPLAS and altered mentality as a very specific feature in diagnosing IKPLAS.

Ampicillin and amoxicillin use and the risk of Klebsiella pneumoniae liver abscess in Taiwan

BACKGROUND

Klebsiella pneumoniae liver abscess (KPLA) is prevalent in East Asia. Use of amoxicillin/ampicillin may lead to overgrowth of K. pneumoniae in the intestine and predispose to KPLA. We used an animal study and nationwide population-based database to investigate the association between ampicillin/amoxicillin use and KPLA in Taiwan.

METHODS

In an animal study, ampicillin or sterile water was administered orogastrically in serotype K1 K. pneumoniae-colonized mice and the outcome was compared. We identified 855 cases with liver abscess and selected 3420 age- and sex-matched control subjects from the National Health Insurance Research Database. Conditional logistic regression was used to estimate the adjusted odds ratios (ORs) for the association between recent use of ampicillin/amoxicillin and KPLA.

RESULTS

Ampicillin administration predisposed K. pneumoniae-colonized mice to increased bacterial burden, liver abscess and necrosis, and lethality. The population-based study showed that the adjusted OR associating the use of ampicillin/amoxicillin within the past 30 days with KPLA was 3.5 (95% confidence interval, 2.5-5.1). No association was found with use in the past 31-90 days.

CONCLUSIONS

Ampicillin/amoxicillin therapy started within the past 30 days was associated with increased risk for KPLA. We should avoid the overuse of these antibiotics to prevent undesired disease in the endemic area.

Klebsiella pneumoniae liver abscess in diabetic patients: association of glycemic control with the clinical characteristics

Background

Klebsiella pneumoniae liver abscess (KPLA) has been reported with increasing frequency in East Asian countries in the past 3 decades, especially in Taiwan and Korea. Diabetes is a well-known risk factor for KPLA and highly associated with septic metastatic complications from KPLA. We investigated the association of glycemic control in diabetic patients with the clinical characteristics of KPLA in Taiwan.

Methods

Adult diabetic patients with KPLA were identified retrospectively in a medical center from January 2007 to January 2012. Clinical characteristics were compared among patients with different levels of current hemoglobin A1c (HbA_1c). Risk factors for metastatic infection from KPLA were analyzed.

Results

Patients with uncontrolled glycemia (HbA_1c ≥ 7%) were significantly younger than those with controlled glycemia (HbA_1c < 7%). Patients with uncontrolled glycemia had the trend to have a higher rate of gas-forming liver abscess, cryptogenic liver abscess, and metastatic infection than those with controlled glycemia. Cryptogenic liver abscess and metastatic infection were more common in the poor glycemic control group (HbA_1c value >; 10%) after adjustment with age. HbA_1c level and abscess < 5 cm were independent risk factors for metastatic complications from KPLA.

Conclusions

Glycemic control in diabetic patients played an essential role in the clinical characteristics of KPLA, especially in metastatic complications from KPLA.

Prognostic factors and outcomes in endogenous Klebsiella pneumoniae endophthalmitis

PURPOSE

To determine risk factors for poor visual acuity outcomes in patients with endogenous Klebsiella pneumoniae endophthalmitis.

DESIGN

Retrospective case-control study.

METHODS

We reviewed all consecutive patients diagnosed with endogenous Klebsiella pneumoniae endophthalmitis over 20 years. Data collected included patients' demographics, clinical findings, investigations, and therapeutic intervention. Main outcome measures were visual acuity (VA) at 3 months postinfection and/or evisceration. Poor vision was defined as VA worse than 4/200.

RESULTS

Seventy-one eyes of 61 patients were studied. Mean age was 55.7 (standard deviation [SD] ± 13.1) years. Majority were male (49/61, 80.3%), Chinese (51/61, 83.6%), and had hepatobiliary sepsis (47/61, 77.5%). Mean time to ocular symptoms was 4.4 (± 3.0) days. Fifty-four of 71 eyes (80.2%) had poor vision and 19/71 eyes (26.8%) required evisceration. The most significant risk factor was hypopyon (41/71 eyes, 57.7%) on multivariate analysis (odds ratio [OR], 52.6; 95% confidence interval [CI], 1.7-1000; P = .01). Unilateral involvement (OR, 10.4; 95% CI, 1.2-90.2; P = .01) and patients that were managed before year 2000 (before routine screening was implemented) (OR, 5.2; 95% CI, 1.5-17.9; P = .037) were significant risk factors for evisceration on multivariate analysis.

CONCLUSION

Patients presenting with hypopyon and unilateral involvement have a poorer prognosis.

Community-acquired Klebsiella pneumoniae liver abscesses - an "emerging disease" in Australia

Liver abscess due to Klebsiella pneumoniae infection has been widely reported in Asia, but rarely reported in Australia until now. We describe four previously well Asian-born patients who presented across Australia with community-acquired K. pneumoniae liver abscesses. With prompt recognition, appropriate antibiotics and early drainage, outcome is significantly improved, although vigilance for metastatic complications is essential.

CT differentiation of pyogenic liver abscesses caused by Klebsiella pneumoniae vs non-Klebsiella pneumoniae

OBJECTIVE

Klebsiella pneumoniae is one of the organisms most commonly isolated from pyogenic liver abscesses in Asian populations. We compared CT findings in liver abscesses caused by K. pneumoniae with those caused by other bacterial pathogens.

METHODS

Of 214 patients with liver abscesses examined over a 5 year period, 129 patients with positive blood or aspirate cultures were enrolled. The patients were divided into two groups: the K. pneumoniae monomicrobial liver abscess (KLA) group (n = 59) and the non-K. pneumoniae monomicrobial or polymicrobial liver abscess (non-KLA) group (n = 70). Two radiologists blinded to the culture results evaluated the CT images, recording the number, size, location and configuration of abscesses, the thickness of the abscess wall, the pattern of rim enhancement, septal enhancement, the double target sign, internal necrotic debris, internal gas bubbles and underlying biliary disease. The presence of diabetes and metastatic infection was also compared between groups. Statistical analyses were performed using univariate (Student's t-test and χ(2) test) and multivariate analyses.

RESULTS

Multivariate analysis showed that a thin wall, necrotic debris, metastatic infection and the absence of underlying biliary disease were the most significant predictors of KLA. When three of the four criteria were used in combination, a specificity of 98.6% was achieved for the diagnosis of KLA.

CONCLUSION

A thin-walled abscess, internal necrotic debris, the presence of metastatic infection and the absence of underlying biliary disease may be useful CT findings in the early diagnosis of K. pneumoniae liver abscesses.

Pyogenic liver abscess: differences in etiology and treatment in Southeast Asia and Central Europe

Knowledge of etiology and timely treatment of underlying causes, when possible, play an important role in the successful therapy of patients with pyogenic liver abscess (PLA). Recent publications from Central Europe and Southeast Asia hint at considerable differences in etiology. In this article, we aim to elaborate these differences and their therapeutic implications. Apart from some special types of PLA that are comparable in Southeast Asia and Central Europe (such as posttraumatic or postprocedural PLA), there are clear differences in the microbiological spectrum, which implies different risk factors and disease courses. Klebsiella pneumoniae (K. pneumoniae) PLA is predominantly seen in Southeast Asia, whereas, in Central Europe, PLA is typically caused by Escherichia coli, Streptococcus or Staphylococcus, and these patients are more likely to be older and to have a biliary abnormality or malignancy. K. pneumoniae patients are more likely to have diabetes mellitus. Control of septic spread is crucial in K. pneumoniae patients, whereas treatment of the underlying diseases is decisive in many Central European PLA patients.

Correlation between Klebsiella pneumoniae carrying pLVPK-derived loci and abscess formation

Klebsiella pneumoniae-caused liver abscess (KLA) is an emerging infectious disease. However, factors other than K1-specific loci that contribute to the pathogenesis of this disease have not been identified. pLVPK is a 219,385-bp plasmid of K. pneumoniae CG43, an invasive K2 strain associated with KLA. We aimed in this study to evaluate the involvement of pLVPK in K. pneumoniae virulence and its clinical significance in abscess formation. A pLVPK-cured CG43 was isolated and its virulence was examined in a mouse model. The prevalence of pLVPK-derived loci terW, iutA, rmpA, silS, and repA was investigated in 207 clinical isolates by screening with specific primers. Loss of pLVPK abolished the ability of K. pneumoniae to disseminate into extraintestinal sites and, consequently, attenuated abscess formation in mice. Primary K. pneumoniae abscess isolates (n = 94) were more likely to be terW (+)-iutA (+)-rmpA (+)-silS (+) than those related to non-abscess infections (n = 113) (62% vs. 27%; p < 0.0001). Logistic regression analysis indicated that the presence of the terW-rmpA-iutA-silS loci was a significant risk factor (odds ratio, 4.12; 95% confidence interval, 2.02-8.4; p < 0.0001) for abscess formation. pLVPK is a determinant for K. pneumoniae virulence and infection with strains carrying the pLVPK-derived terW-rmpA-iutA-silS loci may predispose patients to abscess formation.

Rapid real-time PCR assays for detection of Klebsiella pneumoniae with the rmpA or magA genes associated with the hypermucoviscosity phenotype: screening of nonhuman primates

The relationship of mucoviscosity-associated (magA) and/or regulator of mucoid phenotype (rmpA) genes to the Klebsiella pneumoniae hypermucoviscosity (HMV) phenotype has been reported. We previously demonstrated that rmpA+ K. pneumoniae can cause serious disease in African green monkeys and isolated rmpA+ and magA+ HMV K. pneumoniae from other species of non-human primates. To rapidly screen African green monkeys/non-human primates for these infections, we developed three real-time PCR assays. The first was K. pneumoniae-specific, targeting the khe gene, while the others targeted rmpA and magA. Primer Express 2 was used with the three K. pneumoniae genes to generate sequence-specific TaqMan/TaqMan-Minor Groove Binder assays. Oral/rectal swabs and necropsy samples were collected; swabs were used for routine culture and DNA extraction. K. pneumoniae colonies were identified on the Vitek 2 with DNA tested using the K. pneumoniae-specific assays. Testing of 45 African green monkeys resulted in 19 khe+ samples from 14 animals with none positive for either rmpA or magA. Of these 19 khe+ samples, five were culture-positive, but none were HMV "string test"-positive. Subsequent testing of 307 non-human primates resulted in 64 HMV K. pneumoniae isolates of which 42 were rmpA+ and 15 were magA+. Non-human primate testing at the U.S. Army Medical Research Institute of Infectious Diseases demonstrated the ability to screen both live and necropsied animals for K. pneumoniae by culture and real-time PCR to determine HMV genotype.

Genetic requirements for Klebsiella pneumoniae-induced liver abscess in an oral infection model

Klebsiella pneumoniae is the predominant pathogen of primary liver abscess. However, our knowledge regarding the molecular basis of how K. pneumoniae causes primary infection in the liver is limited. We established an oral infection model that recapitulated the characteristics of liver abscess and conducted a genetic screen to identify the K. pneumoniae genes required for the development of liver abscess in mice. Twenty-eight mutants with attenuated growth in liver or spleen samples out of 2,880 signature-tagged mutants that produced the wild-type capsule were identified, and genetic loci which were disrupted in these mutants were identified to encode products with roles in cellular metabolism, adhesion, transportation, gene regulation, and unknown functions. We further evaluated the virulence attenuation of these mutants in independent infection experiments and categorized them accordingly into three classes. In particular, the class I and II mutant strains exhibited significantly reduced virulence in mice, and most of these strains were not detected in extraintestinal tissues at 48 h after oral inoculation. Interestingly, the mutated loci of about one-third of the class I and II mutant strains encode proteins with regulatory functions, and the transcript abundances of many other genes identified in the same screen were markedly changed in these regulatory mutant strains, suggesting a requirement for genetic regulatory networks for translocation of K. pneumoniae across the intestinal barrier. Furthermore, our finding that preimmunization with certain class I mutant strains protected mice against challenge with the wild-type strain implied a potential application for these strains in prophylaxis against K. pneumoniae infections.

Comparison of prevalence of virulence factors for Klebsiella pneumoniae liver abscesses between isolates with capsular K1/K2 and non-K1/K2 serotypes

Hypermucoviscosity, rmpA (regulator of mucoid phenotype), aerobactin (an iron siderophore), kfu (an iron uptake system), allS (associated with allantoin metabolism), and K1/K2 capsules are important virulence determinants in Klebsiella pneumoniae for liver abscesses. We determined the prevalence of these virulence factors of 50 nonrepeat K. pneumoniae isolates recovered from patients with primary liver abscesses who were treated at 2 medical centers in Taiwan. Virulence genes were surveyed by polymerase chain reaction analysis. The prevalence of hypermucoviscosity phenotype, plasmid-born rmpA, aerobactin, kfu, and allS genes revealed 96%, 100%, 100%, 100%, and 100% in 26 capsular K1 isolates; 90%, 100%, 100%, 0%, and 0% in 10 K2 isolates; and 79%, 86%, 93%, 50%, and 0% in 14 non-K1/K2 isolates; respectively. When injected into mice intraperitoneally, regardless of any capsule K serotype, K. pneumoniae isolates with hypermucoviscosity phenotype as well as presence of rmpA and aerobactin genes exhibited high virulence for mouse lethality (LD(50), <10(2) CFU). Without significant difference in the prevalence of expressing hypermucoviscosity phenotype and carriage of rmpA and aerobactin genes, these virulent non-K1/K2 isolates are as capable as K1/K2 isolates of causing primary liver abscesses.

Community-acquired Klebsiella pneumoniae meningitis in an alcoholic patient with an infected pancreatic pseudocyst; a case report and review of literature

We report a case of a 49-year-old male with a history of chronic alcoholism and evidence of a pancreatic pseudocyst on CT scanning. He presented with a 3-days history of fever, loss of appetite and upper abdominal pain. Blood cultures grew Klebsiella pneumoniae and he improved clinically with a seven-day course of intravenous co-amoxiclav and metronidazole. Two weeks later he was readmitted to hospital with impaired consciousness and septic shock, and died three days later in intensive care. Post mortem examination revealed bacterial meningitis and an infected pancreatic pseudocyst. Klebsiella pneumoniae was isolated from the pancreas and meninges.

Klebsiella pneumoniae genotype K1: an emerging pathogen that causes septic ocular or central nervous system complications from pyogenic liver abscess

BACKGROUND

Since 1986, researchers have noted a syndrome of Klebsiella pneumoniae pyogenic liver abscess that is complicated by endophthalmitis or central nervous system infections. There are limited data regarding the role of bacterial genotype in the pathogenesis of this syndrome.

METHODS

We conducted a retrospective cohort study involving 177 cases of K. pneumoniae pyogenic liver abscess treated during 1997-2005 at a tertiary university hospital in Taiwan. We performed bacterial cps genotyping by polymerase chain reaction detection of serotype-specific alleles at wzy and wzx loci and used an in vitro serum assay to evaluate the virulence of bacterial strains.

RESULTS

Septic ocular or central nervous system complications developed in 23 patients (13%). Logistic regression analysis showed that genotype K1 was the only significant risk factor (adjusted odds ratio, 4.8; 95% confidence interval, 1.5-15.7, P=.009). The serum resistance assay indicated that, on average, K1 strains (n=100) were significantly more virulent than were strains of K2 (n=36), K20/K5/K54 (n=21), or other genotypes (n=20) (P<.001 for each comparison). In addition to the serotype-specific cps region, the genomic background of K1 strains also differed significantly from that of non-K1 strains (20-kb kfu/PTS region, 97/100 vs. 13/77; P<.001). Of the 19 cases in which genotype K1 strains caused complications, 8 patients (42%) did not have identifiable underlying medical diseases.

CONCLUSIONS

K. pneumoniae genotype K1 is an emerging pathogen capable of causing catastrophic septic ocular or central nervous system complications from pyogenic liver abscess independent of underlying diseases in the host.