Primary Liver Abscess Research Articles

Double trouble: an unusual case of Klebsiella pneumoniae invasive syndrome with liver abscess, gallbladder empyema and infective endocarditis

BackgroundKlebsiella pneumoniae invasive syndrome (KPIS) is characterized by primary pyogenic liver abscess associated with metastatic infections. Although rare, Klebsiella endocarditis carries a high mortality risk.Case presentationA 60-year-old lady with type II diabetes mellitus presented with fever, malaise, right hypochondriac pain and vomiting for two weeks. Ultrasound abdomen revealed a collection within liver, and distended gallbladder with echogenic debris within. 3 days after ultrasound guided pigtail drainage of gallbladder empyema, newly presence murmur detected. Pus, urine, and blood cultures obtained were positive for Klebsiella pneumonia. Echocardiogram exhibited oscillating mass attached to anterior mitral valve leaflet. After 6 weeks of intravenous ceftriaxone, follow-up echocardiogram and ultrasound showed complete resolution of mitral valve vegetation, hepatic and gallbladder collection.ConclusionConcomitant extrahepatic infective endocarditis (IE) should raise concerns in daily practice for patients with Klebsiella pneumoniae liver abscesses, despite the rarity of Klebsiella endocarditis. In the absence of diagnostic suspicion, antibiotic treatment regimens may be shortened, and adverse effects from IE infection may ensue.

Involvement of Tn3 transposon in formation and transmission of hypervirulent and carbapenem-resistant Klebsiella pneumoniae

ABSTRACT Hypervirulent and carbapenem-resistant Klebsiella pneumoniae poses a severe threat to public health for its high pathogenicity, transmissibility, and drug resistance. This study aims to explore the evolutionary path and the role of Tn3 transposon in the virulence and carbapenem resistance transmission of K. pneumoniae . Bioinformatics analysis and some experimental tests such as plasmid conjugation experiments, antimicrobial susceptibility testing, and virulence-associated tests were performed to explore the virulence and drug resistance transmission. The complete genome sequencing, S1 nuclease pulsed-field gel electrophoresis, and bioinformatics analysis were used to investigate their transmission mechanism mediated by Tn3 transposons. Three hypervirulent and carbapenem-resistant K. pneumoniae isolates, which were obtained from different patients at different time points in the same ward, harbored a virulence plasmid and a carbapenem resistance plasmid. They were confirmed to have first evolved from hypervirulent isolates and then acquired a bla KPC -positive plasmid (CR-hvKp evolutionary pattern). The non-conjugative virulence plasmid pVir could be transferred to other bacterial strains via mobilization by the conjugative IncN/U-type plasmid pKPC, as well as by fusing with the conjugative pKPC plasmid (mediated by Tn3-based homologous recombination) to be self-transmissible, thus transferring drug resistance and virulence. The cointegration, pVir/KPC fusion plasmid, was further resolved into pVir and pKPC between the duplicated copies of the Tn3 transposon resolution site mediated by site-specific recombination. Therefore, Tn3 transposons can mediate hypervirulent and carbapenem-resistant K. pneumoniae strains transferring drug resistance and virulence to other bacteria. We must be vigilant to emerging transposon-mediated hypervirulent and carbapenem-resistant pathogens. IMPORTANCE Carbapenem-resistant Klebsiella pneumoniae (CRKP) is resistant to most common antibiotics, becoming the most important and prevalent nosocomial opportunity pathogen. Besides, K. pneumoniae can also cause severe community-acquired infections, such as primary liver abscess and endophthalmitis. These pathogens are commonly referred to as hvKp. CRKP and hvKp have evolved separately, each occupying its own clonal lineage and exhibiting a variety of properties. Our study provides important insights into the evolutionary events related to the arousal of virulence and drug resistance in K. pneumoniae through plasmid transmission, mediated by Tn3 transposon. Our study also provides evidence that multiple mechanisms contribute to the successful transfer of non-conjugative virulence plasmid, and the involvement of transposons enhances the efficiency. A good knowledge of its transmission mechanisms is fundamental to finding effective strategies to combat these threatening pathogens. Transposons are widely present in bacteria, spreading resistance and virulence genes between the environment and humans. Therefore, emerging transposon-mediated hypervirulent and carbapenem-resistant pathogens should be highly valued.

Comparison of clinical and microbiological characteristics of community-acquired hypervirulent Klebsiella pneumoniae liver abscess in diabetic and non-diabetic patients.

Invasive infection caused by hypervirulent Klebsiella pneumoniae (HvKP) has been reported worldwide. Most of the patients are community population, related to diabetes mellitus (DM), chronic liver disease and other basic diseases, which prone to systemic migratory infection. In this study, we collected 377 patients with community acquired Klebsiella pneumoniae liver abscess in our hospital from January 2013 to December 2018, 65.8% of whom were male, and 49.6% had DM. Patients with DM are prone to eye and central nervous system (CNS) infection, which need continuous local abscess drainage during treatment. Among them, patients with poor blood glucose control have a higher rate of blood stream infections (BSI). 219 strains of HvKP were obtained, with K1/K2 Serotype accounted for 81.7%. The incidence of BSI in K2 patients was higher than that in K1 patients. The PCR results indicate that the carrying rate of virulence genes (rmpA、areo、kfu、allS、iroN、magA、uge、wcaG) in K1/K2 type strains is significantly higher than that in non K1/K2 type strains. ST23 and ST65 are the most common multilocus sequence typing (MLST), which belong to K1 and K2 Serotype respectively. All of HvKP strains showed high sensitivity to commonly used clinical antibiotics other than ampicillin, with 54.3% of the strains exhibiting high viscosity characteristics. Meanwhile, 35 classic Klebsiella pneumoniae (cKP) strains were collected, and their serum typing is mainly non K1/K2. The carrying rate of virulence genes and viscosity degree in HvKP are significantly higher than those in cKP. Primary liver abscess caused by HvKP is prone to multiple tissue and organ infections, but it shows higher sensitivity to most commonly used antibiotics in clinical practice except for ampicillin. After effective treatment, the overall prognosis of patients is better. This study analyzes the pathogenic characteristics of HvKP and elaborates on the clinical characteristics of patients, which can provide reference for clinical and scientific research work.

Cerebral venous sinus thrombosis in a patient with Klebsiella pneumoniae primary liver abscess: a case report

BackgroundLiver abscess is a common emergency in the emergency department. However, cerebral venous sinus thrombosis (CVST) is a rare and serious cerebrovascular disease. Cases of CVST in patients with Klebsiella pneumoniae primary liver abscess (KLA) have not been described in the literature. We report a case of CVST in patients with KLA.Case presentationA 54-year-old male patient came to our department with a fever for 2 days and altered mental status for 1 day. Abdominal computed tomography (CT) and liver magnetic resonance imaging (MRI) revealed multiple liver abscesses. The blood culture was identified as Klebsiella pneumoniae sepsis. Head contrast-enhanced MRI and magnetic resonance venography (MRV) imaging showed multiple thrombus formation in the right transverse sinus and sigmoid sinus. The patient's infection and thrombosis were controlled within one week of multidisciplinary comprehensive treatment such as antibiotic and antithrombotic therapy, and a good clinical recovery during the 1-month follow-up.ConclusionCVST after liver abscess is rare, clinicians should be aware of this complication and vigilant for the possibility of bacterial meningitis. The underlying mechanisms need to be further studied.

Characterizing outcomes of primary liver abscesses in a single institution

Characterizing outcomes of primary liver abscesses in a single institution

Invasive liver abscess syndrome caused by Klebsiella pneumoniae, case series

Primary liver abscesses caused by Klebsiella pneumoniae and their related systemic complications produce the invasive liver abscess syndrome due to Klebsiella pneumoniae. To describe the clinical, epidemiological and evolution characteristics in our center. A retrospective cohort of hospitalized adults in Hospital Italiano de Buenos Aires between January 1st, 2001 and May 1st, 2020. We included patients with diagnosis of abscess in any organ with rescue in culture or positive blood culture for Klebsiella pneumoniae. Epidemiological, clinical characteristics and prognosis of those with hepatic primary localization were analyzed. 10 patients were included. Two (20%) patients were Oriental. Median age was 69 years (interquartile range 64-79), nine (90%) were men. The most frequent comorbidity was type 2 diabetes (40%). Four (40%) patients had spread to other organs. The median hospitalization was 21.5 days (IIC 15-43), 60% (n: 6) were hospitalized in the intensive care unit and 30% (n: 3) died. The invasive liver abscess syndrome due to Klebsiella pneumoniae is a rare life-threatening disease. Our study reports the characteristics of patients with this syndrome in our population.

Characteristics of Klebsiella pneumoniae Isolates from Stool Samples of Patients with Liver Abscess Caused by Hypervirulent K. pneumoniae.

BackgroundHypervirulent Klebsiella pneumoniae (hvKP) has been the most significant pathogen for liver abscesses in East Asia including the Republic of Korea (ROK). Although gastrointestinal colonization of K. pneumoniae may cross the intestinal barrier to invade the liver, characteristics of gastrointestinal carriage K. pneumoniae of hvKP liver abscess patients in the ROK are not well known.MethodsCharacteristics of K. pneumoniae isolated from stool samples and liver aspirate samples of patients with hvKP liver abscess at a tertiary care hospital in the ROK between 2017 and 2018 were evaluated.ResultsOut of 37 patients with hvKP liver abscess, 11 patients were noted to have K. pneumoniae isolated from stool samples and were enrolled for analysis. The median age was 71 years. For hvKP isolates from the liver aspirate samples, the most common serotype was K1 (72.7%) followed by K2 (27.3%). For K. pneumoniae isolates from the stool sample, the majority was non-K1/K2 serotype (72.7%). Among non-K1/K2 serotype isolates, high variability of sequence type (ST; ST15, ST307, ST37, ST273, ST2622, and ST42) with high rate of presence of extended-spectrum beta-lactamase (100.0%) was noted. The concordance rate of the K. pneumoniae isolates between the liver aspirate samples and the stool samples from the primary hvKP liver abscess was low (27.3%).ConclusionThis study suggests that significant heterogeneity of K. pneumoniae colonizing intestinal tract of the hvKP liver abscess patients. Further studies involving a larger number of hvKP liver abscess patients with continuing surveillance are needed to define the changing epidemiology and the role of gastrointestinal K. pneumoniae in the hvKP liver abscess patients in the ROK.

PLEURAL EFFUSION CAUSED BY KLEBSIELLA PYOGENIC LIVER ABSCESS

SESSION TITLE: Monday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/21/2019 02:30 PM - 03:15 PM INTRODUCTION: Historically, pyogenic liver abscesses were most commonly of Escherichia coli or polymicrobial etiology. Klebsiella pneumoniae has become a rising cause of pyogenic liver abscesses, particularly in Taiwan, since 1996 [1]. Predisposing factors of Klebsiella primary liver abscess (KLA) include diabetes, prior antibiotic use, and specific virulence factors including the K1 capsular antigen genotype[2]. This case details a middle-aged, non diabetic, male who presented with KLA that resulted in metastatic pleural empyema after abscess drainage. CASE PRESENTATION: A 52 year old male without medical history, presented with sharp, right upper quadrant moderate abdominal with radiation to the back for three months. He had mild guarding with active bowel. One month prior, he had a computed tomography (CT) of the abdomen showed cholecystectomy and a complex fluid collection posterior to the right hepatic lobe that measured 3.0 x 2.5 cm. A repeated CT upon this admission revealed a 5 x 3.1 x 4.8 cm heterogeneous collection along the posterior aspect of the right lobe of liver. The fluid collection was increased in size compared to prior imaging and concerning for an abscess. The patient underwent CT-guided abscess drainage with a drain placement five days after admission. Antibiotic treatment with Zosyn was initiated; the patient also received Flagyl and vancomycin. The culture of the abscess grew K. pneumoniae. Shortly following the abscess drainage, the patient began exhibiting shortness of breath with decreased breath sounds, dyspnea with activity, ongoing low grade fever, and leukocytosis. At the day of the drainage, his white blood cell count (WBC)15,800. CT-guided pleural fluid drainage with pigtail chest tube placement done. Pleural fluid analysis showed a lactate dehydrogenase(LDH) of 2,628 and a total protein (TP) of 4.7 consistent with exudate, and a pH of 7. The culture of the pleural fluid also grew K. pneumoniae. Infectious disease recommendation to continue the course of Zosyn for a total of four weeks from the day of the abscess drain placement. A repeated CXR reported slight improvement of the right pleural effusion with symptomatic improvement with chest tube placement and significant drainage of pleural fluid. The patient was seen as an outpatient with significant improvement. DISCUSSION: The clinical significance of the increasing trend of KLA should be noted due to potential metastasis, most commonly endophthalmitis and meningitis, which occur more frequently than in other microbial etiologies of liver abscesses. In a 1998 study done in Taiwan 11.9% of KLA resulted in metastatic complications compared to 0% of polymicrobial liver abscesses [2]. Furthermore, the significant risk factor of diabetes mellitus as a predisposing factor. CONCLUSIONS: To keep in our mind that pleural empyema due to Klebsiella Pneumoniae can be a consequnt complication of liver abscess. Reference #1: 1. Yang CC, Yen CH, Ho MW, & Wang JH (2004). Comparison of pyogenic liver abscess caused by non-Klebsiella pneumoniae and Klebsiella pneumoniae. J Microbiol Immunol Infect., 37(3), 176. Reference #2: 2. Wang JH, Liu YC, Lee SS, Yen MY, Chen YS, Wang JH, Wann SR, & Lin HH (1998). Primary liver abscess due to Klebsiella pneumoniae in Taiwan. Clin Infect Dis., 26(6), 1434. DISCLOSURES: No relevant relationships by WAQAS HAFEEZ, source=Web Response No relevant relationships by Nooraldin Merza, source=Web Response No relevant relationships by Mazin Saadaldin, source=Web Response

3197 Pyogenic Liver Abscess in B-Thalassemia: A Case Report

INTRODUCTION: Pyogenic liver abscess typically develops via systemic seeding of an infection or from biliary disease through direct spread or portal circulation. Invasive liver abscess though may occur in Beta-thalassemia major patients are a rarity in Beta-thalassemia minor. CASE DESCRIPTION/METHODS: 36-year-old woman with a history of B-thalassemia minor presents to the ED with complaints of acute onset severe, non-radiating right upper quadrant pain. She endorses fevers, chills and night sweats but denied anorexia, nausea, vomiting, diarrhea or urinary symptoms. Never been transfused. Physical exam was pertinent for a temperature of 102.8 F, tachycardia of 138 bpm, and an upper quadrant abdominal tenderness with some guarding. Labs was notable for leukocytosis with neutrophil predominant, anemia with Hb of 5.3 g/dl. Elevated ESR and CRP. Lipase and amylase were normal. CT abdomen showed 10.3 cm thick-walled, complex fluid collection in the right hepatic lobe and splenic abscesses consistent with a pyogenic abscess. Blood cultures were negative. She was started on empiric antibiotic with vancomycin and piperacillin/ tazobactam and was subsequently taken to interventional radiology for drainage of the abscess, with a J-P drain left insitu. The patient received 2 units of packed red blood cells. Fluid culture from drain was positive for Klebsiella pneumoniae which was sensitive to Levaquin. The patient's condition improved while on antibiotics with subsequent removal of the J-P drain. She was successfully discharged on oral Flagyl and Levaquin for 14 days. DISCUSSION: Typically, thalassemia minor carriers are clinically asymptomatic with very little to no complications. Infections however, are a major complication, and constitute the second most common cause of mortality and a main cause of morbidity in patients with thalassemia. The major culprit bacterial infections in thalassemia patients are Klebsiella sppand Yersinia enterocolitica. K. pneumoniae is also associated with a community-acquired primary invasive liver abscess syndrome. Liver abscess occur more commonly in beta- thalassemia major as these group of patient have predisposing factors such as underlying hepatobiliary dysfunction and recurrent transfusions. This condition is rare in beta- thalassemia minor. Abscess rupture is a rare complication, while metastatic infection to other sites can occur. Diagnosis is usually made with CT scan of the abdomen while treatment is should be started with empiric broad-spectrum and drainage of the abscess.

Klebsiella pneumoniae Invasive Syndrome.

Klebsiella pneumoniae invasive syndrome (KPIS) is a rare clinical condition characterized by primary liver abscess associated with metastatic infection. Most case reports are from Southeast Asia, with only one case described in Portugal. The Authors present the case of a 44-year-old man with a history of fever, dry cough and cervicalgia. A thoracic computed tomography (CT) scan showed multiple pulmonary and hepatic nodules, suggestive of metastatic malignancy. Both blood cultures and bronchoalveolar lavage were positive for Klebsiella pneumoniae. Imaging studies were repeated during his hospital stay, showing a reduction in both number and volume of identified lesions, thus revealing their infectious nature. This case illustrates how much this entity can mimic other illnesses.LEARNING POINTSKlebsiella pneumoniae invasive syndrome is emerging as a global disease.The imaging-led diagnosis of neoplasia was proved incorrect and could have been deleterious for the patient.The lack of diagnostic suspicion can lead to shorter antibiotic treatment regimens, therefore compromising the patient’s full recovery.

Liver Abscess Turned Metastatic Infection in an Otherwise Healthy Patient: A Case Report

The most common type of visceral abscesses are liver abscesses, which have a mortality rate of at least 2.5 percent.1,2 Most liver abscesses are polymicrobial, containing both facultative and anaerobic enteric pathogens, and develop secondary to another infection such as peritonitis and cholangitis, or from hematogenous spread.2-4 Liver abscesses are sometimes associated with systemic diseases such as colorectal cancer and diabetes mellitus.5,6 Rarely, as in our case presentation, primary liver abscesses occur spontaneously in patients with no identifiable precipitating or predisposing conditions.

Primary liver abscess caused by Klebsiella pneumoniae: An increasingly common entity

Primary liver abscess caused by Klebsiella pneumoniae: An increasingly common entity

Hypermucoviscosity, rmpA, and aerobactin are associated with community-acquired Klebsiella pneumoniae bacteremic isolates causing liver abscess in Singapore.

This retrospective study investigated the clinical etiology of community-acquired bacteremic Klebsiella pneumoniae infections, and characterized laboratory and genetic markers which may be associated with primary liver abscess (PLA). Community-onset K. pneumoniae bacteremic episodes from 2010 to 2011 were identified from the laboratory information system. Isolates were retrieved for susceptibility testing, hypermucoviscosity testing, PCR-based serotyping (K1, K2 and K5) and PCR detection of virulence genes (rmpA, alls, kfu and aerobactin). Clinical data collected from electronic medical records included primary and secondary diagnoses, co-existing morbidities, antibiotic therapy, and in-patient mortality. 129 bacteremic episodes were identified. The most common primary infections were pneumonia (n=24, 18.6%), primary liver abscess (n=21, 16.3%) and urinary tract infections (n=21, 16.3%). Hypermucoviscosity was present in 55 isolates (42.6%). The most commonly detected virulence genes were aerobactin (n=63, 48.8%) and rmpA (n=59, 45.7%). Isolates causing liver abscess were significantly associated with a positive string test, rmpA, aerobactin gene, and capsular serotype K1 (all p<0.01), but not with capsular serotype K2, K5, kfu, or allS genes. The absence of a positive string test, rmpA, or aerobactin genes had a 97.3%-100% negative predictive value for PLA. The positive predictive values of the string test, rmpA, aerobactin genes, and serotype K1 for PLA ranged from 31.7% to 35.6%. In our study population, pneumonia and PLA were the most common sources of community-acquired bacteremia. Hypermucoviscosity, rmpA, aerobactin, and serotype K1 could be useful laboratory markers to alert clinicians to arrange abdominal imaging to detect liver abscess.

Involvement of cAMP receptor protein in biofilm formation, fimbria production, capsular polysaccharide biosynthesis and lethality in mouse of Klebsiella pneumoniae serotype K1 causing pyogenic liver abscess.

The global regulator cAMP receptor protein (CRP) has been shown to be required for the full virulence and/or for the expression of virulence determinants in a wide set of bacterial pathogens. In this work, the crp mutant as well as the complemented mutant was constructed from a wild-type Klebsiella pneumoniae capsular serotype K1 strain causing the primary pyogenic liver abscess. The phenotypes of wild-type strain, crp mutant and complemented mutant were characterized systematically. It was disclosed that K. pneumoniae CRP was required for the in vitro growth, fimbria production, biofilm formation and lethality in mouse, but it inhibited the capsular polysaccharide biosynthesis. These indicated the important roles of CRP in regulating the expression of virulence and biofilm genes in K. pneumoniae.

Two Genome Sequences of Klebsiella pneumoniae Strains with Sequence Type 23 and Capsular Serotype K1.

Here, we report the whole-genome sequences of Klebsiella pneumoniae ED2 and ED23, isolated, respectively, from bacteremic patients with liver abscesses (ED2) and patients with primary liver abscess and metastatic meningitis (ED23). Both strains were of multilocus sequence type 23 with capsule serotype K1.

The emerging problems of Klebsiella pneumoniae infections: carbapenem resistance and biofilm formation.

Klebsiella pneumoniae is an opportunistic pathogen that commonly causes nosocomial infections in the urinary tract, respiratory tract, lung, wound sites and blood in individuals with debilitating diseases. Klebsiella pneumoniae is still a cause of severe pneumonia in alcoholics in Africa and Asia, and the predominant primary pathogen of primary liver abscess in Taiwan and Southeast Asia, particularly in Asian and Hispanic patients, and individuals with diabetes mellitus. In the United States and Europe, K. pneumoniae infections are most frequently associated with nosocomial infections. The emergence of antibiotic-resistant strains of K. pneumoniae worldwide has become a cause of concern where extended-spectrum β-lactamases (ESBLs) and carbapenemase-producing strains have been isolated with increasing frequency. The pathogen's ability to form biofilms on inserted devices such as urinary catheter has been proposed as one of the important mechanisms in nosocomially acquired and persistent infections, adding to the increased resistance to currently used antibiotics. In this review, infections caused by K. pneumoniae, antibiotic resistance and formation of biofilm will be discussed.

Invasive liver abscess syndrome caused by Klebsiella pneumoniae with definite K2 serotyping in Japan: a case report.

BackgroundKlebsiella pneumonia is a well-known human pathogen, and recently, a distinct invasive syndrome caused by K. pneumoniae serotypes K1 and K2 has been recognized in Southeast Asia. This syndrome is characterized by primary liver abscess and extrahepatic complications resulting from bacteremic dissemination. We report the first adult case of primary liver abscess caused by the definite K2 serotyped pathogen, with endogenous endophthalmitis in Japan.Case presentationA 64-year-old woman was admitted to a nearby hospital for a high fever and diarrhea. She had visual loss of her right eye, renal dysfunction, and thrombocytopenia within 24 h from admission. She was transferred to our institution. On admission, she had no alteration of mental status and normal vital signs; however, she had almost complete ablepsia of the right eye. Laboratory data showed severe inflammation, liver dysfunction, thrombocytopenia, an increased serum creatinine level, and coagulopathy. Computed tomography showed a low density area in the right lobe of the liver. Invasive liver abscess syndrome probably caused by K. pneumonia was highly suspected and immediately administered broad-spectrum antibiotics for severe sepsis. Concurrently, endogenous endophthalmitis was diagnosed, and we performed vitrectomy on the day of admission. The blood culture showed K. pneumoniae infection. Percutaneous drainage of the liver abscess was also performed. Although she was discharged in a good general condition on day 22, she had complete ablepsia of the right eye. The K2A gene was detected by polymerase chain reaction (PCR), which is consistent with the K2 serotype. PCR was also positive for the virulence-associated gene rmpA. Final diagnosis was invasive liver abscess syndrome caused by K2 serotype K. pneumonia.ConclusionsAlthough the primary liver abscess caused by K. pneumoniae with a hypermucoviscous phenotype is infrequently reported outside Southeast Asia, physicians should recognize this syndrome, and appropriate diagnosis and treatment is essential for saving patients’ lives and preserving organ function, especially for visual acuity.

Clinical and molecular characteristics of bloodstream infection caused by K. pneumonia

Objective To investigate the clinical features and molecular characteristics of bacteremia caused by K. pneumoniae and study on the differences between classical and hypervirulent K. pneumonia(hvKP). Methods The clinical features of 70 cases of K. pneumoniae bacteremia collected from Beijing Chaoyang Hospital from 2008 to 2012 were retrospectively analyzed. The patients were identified according to the records from the Clinical Microbiology Department. Patients' data were obtained from medical records. The molecular characteristics of the K. pneumoniae strains were also studied using PCR, multilocus sequence typing and pulsed field gel electrophoresis(PFGE) methods. Data were analyzed using the statistical package SPSS for windows version 17.0. For categorical data, different groups were compared using the Chi-square test to analyze the quantitative variables. P≤0.05 was considered to be statistically significant. All susceptibility data were analyzed using Whonet, version 5.6. Results The hvKP was identified from 31.4% of the patients with K. pneumoniae bacteremia, which displayed 4 serotypes (K1, K2, K20, and K57). About 40.9% (9/22) hypervirulent strains were isolated from patients without underlying diseases, while 95.8% (46/48) of the classic K. pneumoniae infections were found in patients with the presence of one or more underlying diseases. More hvKP positive patients (95.5%, 21/22) had community-acquired infections compared with classical K. pneumonia (cKP) infected patients (35.4%, 17/48). There was a significant difference between these two groups (χ2=21.912, P<0.001). Two ESBLs-producing hvKP strains were found. The 22 hvKP isolates had 14 different PFGE patterns, among which 6 isolates (patients with primary liver abscess) shared similar PFGE patterns. Conclusions The emerging hvKP was prevalent in patients with severe community-acquired infections in healthy individuals. Two ESBLs-producing hvKP strains were identified. Drug resistance had a rising trend, which called for more attention in clinical settings. (Chin J Lab Med, 2015, 38: 627-631) Key words: Liver abscess; Community-acquired infections; Klebsiella pneumoniae; Virulence

Eight cases of invasive Klebsiella pneumoniae infection from a public teaching medical institution in the USA

Background: Klebsiella pneumoniae is a common human bacterial pathogen known to cause invasive infections such as primary liver abscesses, necrotizing fasciitis, meningitis and endophthalmitis with bacteraemia among patients in eastern Asia. Over the last decade, geographical spread and emergence of invasive K. pneumoniae infection has occurred in the USA. The majority of reported cases involve males with diabetes mellitus, of Asian ethnicity and who have recently travelled to Asia. Results: We identified eight invasive cases with liver abscesses and necrotizing fasciitis at our institution. The most common risk factors associated with invasive infection were male gender and diabetes mellitus, which is consistent with other reported cases. However, Caucasians and Hispanics represented the majority of invasive disease (n = 7), and history of recent travel to Asia was not identified in any of the cases. Discussion: Further studies with larger cohorts involving multiple healthcare institutions in the USA are warranted to confirm these two unusual characteristics of infection. Healthcare professionals should be informed of the possible association between K. pneumoniae and invasive disease in male diabetic persons of non-Asian descent and without recent travel to Asia in the USA.

Capsular Polysaccharide Is Involved in NLRP3 Inflammasome Activation by Klebsiella pneumoniae Serotype K1.

Klebsiella pneumoniae (strain 43816, K2 serotype) induces interleukin-1β (IL-1β) secretion, but neither the bacterial factor triggering the activation of these inflammasome-dependent responses nor whether they are mediated by NLRP3 or NLRC4 is known. In this study, we identified a capsular polysaccharide (K1-CPS) in K. pneumoniae (NTUH-K2044, K1 serotype), isolated from a primary pyogenic liver abscess (PLA K. pneumoniae), as the Klebsiella factor that induces IL-1β secretion in an NLRP3-, ASC-, and caspase-1-dependent manner in macrophages. K1-CPS induced NLRP3 inflammasome activation through reactive oxygen species (ROS) generation, mitogen-activated protein kinase phosphorylation, and NF-κB activation. Inhibition of both the mitochondrial membrane permeability transition and mitochondrial ROS generation inhibited K1-CPS-mediated NLRP3 inflammasome activation. Furthermore, IL-1β secretion in macrophages infected with PLA K. pneumoniae was shown to depend on NLRP3 but also on NLRC4 and TLR4. In macrophages infected with a K1-CPS deficiency mutant, an lipopolysaccharide (LPS) deficiency mutant, or K1-CPS and LPS double mutants, IL-1β secretion levels were lower than those in cells infected with wild-type PLA K. pneumoniae. Our findings indicate that K1-CPS is one of the Klebsiella factors of PLA K. pneumoniae that induce IL-1β secretion through the NLRP3 inflammasome.