Community-acquired Klebsiella pneumoniae bacteremia: global differences in clinical patterns

An Outbreak of Carbapenem-Resistant and Hypervirulent Klebsiella pneumoniae in an Intensive Care Unit of a Major Teaching Hospital in Wenzhou, China

Carbapenem-resistant, hypervirulent Klebsiella pneumoniae (CR-hvKP) has recently emerged as a significant threat to public health. In this study, 29 K. pneumoniae isolates were isolated from eight patients admitted to the intensive care unit (ICU) of a comprehensive teaching hospital located in China from March 2017 to January 2018. Clinical information of patients was the basis for the further analyses of the isolates including antimicrobial susceptibility tests, identification of antibiotic resistance and virulence gene determinants, multilocus sequence typing (MLST), XbaI-macrorestriction by pulsed-field gel electrophoresis (PFGE). Selected isolates representing distinct resistance profiles and virulence phenotypes were screened for hypervirulence in a Galleria mellonella larvae infection model. In the course of the outbreak, the overall mortality rate of patients was 100% (n = 8) attributed to complications arising from CR-hvKP infections. All isolates except one (28/29, 96.6%) were resistant to multiple antimicrobial agents, and harbored diverse resistance determinants that included the globally prevalent carbapenemase bla_KPC−2. Most isolates had hypervirulent genotypes being positive for 19 virulence-associated genes, including iutA (25/29, 86.2%), rmpA (27/29, 93.1%), ybtA (27/29, 93.1%), entB (29/29, 100%), fimH (29/29, 100%), and mrkD (29/29, 100%). MLST revealed ST11 for the majority of isolates (26/29, 89,7%). Infection assays demonstrated high mortality in the Galleria mellonella model with the highest LD₅₀ values for three isolates (<10⁵ CFU/mL) demonstrating the degree of hypervirulence of these CR-hvKP isolates, and is discussed relative to previous outbreaks of CR-hvKP.

Molecular analysis of virulence factors of hypermucoviscous Klebsiella pneumoniae in a diabetes patient with multifocal intramuscular and musculoskeletal abscesses

Unusual community-acquired invasive Klebsiella pneumoniae infection has been reported worldwide, particularly in Asia. Recently, several virulence-associated genes of the isolates have been investigated. We report a case of multifocal intramuscular and musculoskeletal abscesses caused by K. pneumoniae in a 61-year-old male diabetes patient. A string test of the K. pneumoniae isolate, which was recovered from abscesses obtained by surgical debridement and drainage, was positive. We used whole-genome sequencing to analyze the virulence-associated gene profile of the isolate. The isolate belonged to the K2 genotype with sequence type 375. The isolate harbored rmpA and rmpA2, which induce serum resistance (hypermucoviscosity). The isolate also carried siderophores, i.e., aerobactin and salmochelin, which are associated with enhanced bacterial growth. The isolate did not harbor K1-unique virulence factors, such as colibactin, microcin, and yersiniabactin. Our K2 strain harbored a combination of virulence plasmid-associated genes-rmpA/A2 and siderophores (aerobactin and salmochelin). Hence, we advocate that essential molecular virulence factors of isolates that cannot be identified by a string test and capsular serotyping alone may exist.

Hypervirulent Klebsiella pneumoniae

Hypervirulent K. pneumoniae (hvKp) is an evolving pathotype that is more virulent than classical K. pneumoniae (cKp). hvKp usually infects individuals from the community, who are often healthy. Infections are more common in the Asian Pacific Rim but are occurring globally. hvKp infection frequently presents at multiple sites or subsequently metastatically spreads, often requiring source control. hvKp has an increased ability to cause central nervous system infection and endophthalmitis, which require rapid recognition and site-specific treatment. The genetic factors that confer hvKp's hypervirulent phenotype are present on a large virulence plasmid and perhaps integrative conjugal elements. Increased capsule production and aerobactin production are established hvKp-specific virulence factors. Similar to cKp, hvKp strains are becoming increasingly resistant to antimicrobials via acquisition of mobile elements carrying resistance determinants, and new hvKp strains emerge when extensively drug-resistant cKp strains acquire hvKp-specific virulence determinants, resulting in nosocomial infection. Presently, clinical laboratories are unable to differentiate cKp from hvKp, but recently, several biomarkers and quantitative siderophore production have been shown to accurately predict hvKp strains, which could lead to the development of a diagnostic test for use by clinical laboratories for optimal patient care and for use in epidemiologic surveillance and research studies.

Treatment with andrographolide sulfonate provides additional benefits to imipenem in a mouse model of Klebsiella pneumoniae pneumonia

Klebsiella pneumoniae is a primary cause of community-acquired and nosocomial respiratory infections, and K. pneumoniae resistance to the current treatment approach with carbapenem is worsening. Andrographolide is a natural diterpenoid from Andrographis paniculata that was shown to exert anti-inflammatory activity. We herein show that pretreatment with a water-soluble andrographolide sulfonate significantly attenuate lung injury and infiltration of inflammatory cells. Interestingly, mice receiving combined treatment with andrographolide sulfonate displayed perfect survival rate than the mice treatment with imipenem alone, and monocyte chemotactic protein 5 (MCP-5) level was decreased further. These findings suggest that andrographolide sulfonate could as a potential synergist for antibiotic treatment of bacteria-induced inflammation.

The Determination and Correlation of Various Virulence Genes, ESBL, Serum Bactericidal Effect and Biofilm Formation of Clinical Isolated Classical Klebsiella pneumoniae and Hypervirulent Klebsiella pneumoniae from Respiratory Tract Infected Patients

Klebsiella pneumoniae strains that are commonly recognized by clinicians and microbiologists are termed as classical K. pneumoniae (cKP). A strain with capsule-associated mucopolysaccharide web is known as hypervirulent K. pneumoniae (hvKP) as it enhances the serum resistant and biofilm production. Aim is to determine and correlate various virulence genes, ESBL, serum bactericidal effect and biofilm formation of clinical isolated cKP and hvKP from respiratory tract infected patients. A total of 96 K. pneumoniae strains were isolated from sputum of respiratory tract infected patients. The isolates were performed string test, AST, ESBL virulence gene, serum bactericidal and biofilm assays. Out of 96 isolates, 39 isolates (40.6%) were identified with hypervirulent phenotypes. The number of cKP exhibiting resistance to the tested antimicrobials and ESBLs were significantly higher than that of the hvKP strains. The virulence genes of K. pneumoniae such as K1, K2, rmpA, uge, kfu and aerobactin were strongly associated with hvKP than cKP. However, no significant difference was found in FIM-1 and MrKD3 genes. ESBL producing cKP and hvKP were significantly associated with strong biofilm formation (both P &lt; 0.05) and highly associated with bactericidal effect of serum (both P &lt; 0.05) than cKP strains. However, neither biofilm formation nor bactericidal effect of serum was found with significant difference in between ESBL producing cKP and ESBL producing hvKP strains (both P &gt; 0.05). Although the hvKP possess more virulence gene, but they didn't show any significant difference between biofilm formation and bactericidal effect of serum compared with ESBL producing cKP strains.

Association Between Alcohol Use Disorders and Outcomes of Patients Hospitalized With Community-Acquired Pneumonia

IMPORTANCE

Patients with alcohol use disorder (AUD) are at elevated risk of developing pneumonia, but few studies have assessed the outcomes of pneumonia in patients with AUD.

OBJECTIVES

To compare the causes, treatment, and outcomes of pneumonia in patients with and without AUD and to understand the associations of comorbid illnesses, alcohol withdrawal, and any residual effects due to alcohol itself with patient outcomes.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective cohort study was conducted of 137 496 patients 18 years or older with pneumonia who were admitted to 177 US hospitals participating in the Premier Healthcare Database from July 1, 2010, to June 30, 2015. Statistical analysis was conducted from October 27, 2017, to August 20, 2018.

EXPOSURE

Alcohol use disorders identified from International Classification of Diseases, Ninth Revision, Clinical Modification codes.

MAIN OUTCOMES AND MEASURES

Pneumonia cause, antibiotic treatment, inpatient mortality, clinical deterioration, length of stay, and cost. Associations of AUD with these variables were studied using generalized linear mixed models.

RESULTS

Of 137 496 patients with community-acquired pneumonia (70 358 women and 67 138 men; mean [SD] age, 69.5 [16.2] years), 3.5% had an AUD. Patients with an AUD were younger than those without an AUD (median age, 58.0 vs 73.0 years; P < .001), more often male (77.3% vs 47.8%; P < .001), and more often had principal diagnoses of aspiration pneumonia (10.9% vs 9.8%; P < .001), sepsis (38.6% vs 30.7%; P < .001), or respiratory failure (9.3% vs 5.5%; P < .001). Their cultures more often grew Streptococcus pneumoniae (43.7% vs 25.5%; P < .001) and less frequently grew organisms resistant to guideline-recommended antibiotics (25.0% vs 43.7%; P < .001). Patients with an AUD were treated more often with piperacillin-tazobactam (26.2% vs 22.5%; P < .001) but equally as often with anti-methicillin-resistant Staphylococcus aureus agents (32.9% vs 31.8%; P = .11) compared with patients without AUDs. When adjusted for demographic characteristics and insurance, AUD was associated with higher mortality (odds ratio, 1.40; 95% CI, 1.25-1.56), length of stay (risk-adjusted geometric mean ratio, 1.24; 95% CI, 1.20-1.27), and costs (risk-adjusted geometric mean ratio, 1.33; 95% CI, 1.28-1.38). After additional adjustment for differences in comorbidities and risk factors for resistant organisms, AUD was no longer associated with mortality but remained associated with late mechanical ventilation (odds ratio, 1.28; 95% CI, 1.12-1.46), length of stay (risk-adjusted geometric mean ratio, 1.04; 95% CI, 1.01-1.06), and costs (risk-adjusted geometric mean ratio, 1.06; 95% CI, 1.03-1.09). Models segregating patients undergoing alcohol withdrawal showed that poorer outcomes among patients with AUD were confined to the subgroup undergoing alcohol withdrawal.

CONCLUSIONS AND RELEVANCE

This study suggests that, compared with hospitalized patients with community-acquired pneumonia but without AUD, those with AUD less often harbor resistant organisms. The higher age-adjusted risk of death among patients with AUD appears to be largely attributable to differences in comorbidities, whereas greater use of health care resources may be attributable to alcohol withdrawal.

Transcriptome Analysis Reveals AI-2 Relevant Genes of Multi-Drug Resistant Klebsiella pneumoniae in Response to Eugenol at Sub-MIC

Eugenol, the major active essential oil component of clove, was reported to possess QS (quorum sensing) inhibitory activity. A previous study found that eugenol could bind to quorum sensing receptors of Pseudomonas aeruginosa and down-regulate the expression of Streptococcus mutans virulence genes at sub-MIC (minimum inhibitory concentration) without affecting the bacterial growth. However, the alterations of QS signal molecules at transcription levels was not well understood. To better understand interactions of Klebsiella pneumoniae in response to eugenol and explore molecular regulations, transcriptome sequencing was performed. A total of 5779 differentially expressed genes (DEGs) enriched in a variety of biological processes and pathways were identified. The transcriptional data was validated by qPCR and the results showed that the expression profiles of 4 major genes involved in autoinducers-2 (AI-2) synthesis, including luxS, pfs, and lsrK were consistent with transcriptome analysis except for lsrR, a transcriptional repressor gene of lsr operon, which may repress the expression of following genes responsible for AI-2 signal transmission in vivo. In vitro AI-2 synthesis assay also revealed that eugenol could inhibit AI-2 generation. The results of our study offer insights into the mechanisms of QS inhibitory activity and K. pneumoniae AI-2 alterations after eugenol treatment.

Antibiotic Resistance and Clinical Presentation of Health Care-Associated Hypervirulent Klebsiella pneumoniae Infection in Korea

Hypervirulent Klebsiella pneumoniae typically presents as a community-acquired infection causing a liver abscess. It is often associated with rmpA and magA genes and confers a mucoid phenotype. Our aim was to evaluate the clinical presentation and antibiotic resistance of hypervirulent K. pneumoniae (hvKP) of health care-associated origin. The study was performed on 414 K. pneumoniae isolates recovered from patients that visited our hospital from December 2013 through November 2015. Hypervirulence was determined by the presence of a hypermucoviscous phenotype, in 155 isolates (37.4%). We compared health care-associated hvKP infections with community-acquired infections. The hypermucoviscous phenotype was 60 isolates (24.2%) in health care-associated infection and 90 isolates (53.8%) in community-acquired infection. Respiratory infection was the most common source of health care-associated K. pneumoniae. Antibiotic resistance was higher in health care-associated hvKP infections, which were more frequently associated with non-K1/K2 serotypes and less frequently associated with rmpA gene. In our study, 38% of hvKP was health care associated. Pneumonia is the most common infection, besides intraabdominal infection, in community-originating strains. These results suggest that health care-associated hvKP may have different microbiological characteristics from classical community-associated infections. Further investigation is needed for other virulent factors associated with health care-associated hvKP.

Identification of three podoviruses infecting Klebsiella encoding capsule depolymerases that digest specific capsular types

Klebsiella pneumoniae is an important human pathogen causing opportunistic nosocomial and community-acquired infections. A major public health concern regarding K. pneumoniae is the increasing incidence of multidrug-resistant strains. Here, we isolated three novel Klebsiella bacteriophages, KN1-1, KN3-1 and KN4-1, which infect KN1, KN3 and K56, and KN4 types respectively. We determined their genome sequences and conducted a comparative analysis that revealed a variable region containing capsule depolymerase-encoding genes. Recombinant depolymerase proteins were produced, and their enzymatic activity and specificity were evaluated. We identified four capsule depolymerases in these phages that could only digest the capsule types of their respective hosts. Our results demonstrate that the activities of these capsule depolymerases were correlated with the host range of each phage; thus, the capsule depolymerases are host specificity determinants. By generating a capsule mutant, we demonstrate that capsule was essential for phage adsorption and infection. Further, capsule depolymerases can enhance bacterial susceptibility to serum killing. The discovery of these phages and depolymerases lays the foundation for the typing of KN1, KN3, KN4 and K56 Klebsiella and could be useful alternative therapeutics for the treatment of K. pneumoniae infections.

Clinical characteristics of bacteremia caused by hypermucoviscous Klebsiella pneumoniae at a tertiary hospital

This study aimed to assess the predictive factors of bacteremia due to hypermucoviscous Klebsiella pneumoniae (hvKP), as well as the mortality. The medical records of 114 patients with K. pneumoniae bacteremia who were divided into the hvKP (n = 24) and non-hvKP (n = 90) groups and were retrospectively reviewed. The male-to-female ratio, age, and underlying disease did not differ between the 2 groups. Mortality was higher among patients in the hvKP bacteremia group than in the non-hvKP bacteremia group (29.2% vs 6.7%). Multivariate analysis showed that the independent predictors associated with hvKP bacteremia were abscess (P = 0.01) and no antibiotic exposure (P = 0.02); thus, early assessment of these conditions is important. For patients with a history of abscess and no antibiotic exposure, it is necessary to administer treatment while keeping the risk of hvKP in mind.

[Endogenous endophthalmitis following staphylococcus aureus meningitis]

Endogenous endophthalmitis is a rare complication of acute meningitis. A healthy 82-year-old woman suddenly developed septic bacteremia and meningitis owing to Staphylococcus aureus (methicillin-susceptible Staphylococcus aureus); she presented with a high fever and drowsiness. Improvement of these initial symptoms unveiled impaired bilateral visual acuity. Detailed ophthalmological assessments diagnosed it as probable endogenous endophthalmitis, which was immediately treated with vitrectomy. Subsequently, the patient totally recovered without any neurologic or ophthalmic sequela.

Community-acquired pneumonia and Gram-negative bacilli in Cambodia-incidence, risk factors and clinical characteristics

Background

In Western settings, community-acquired pneumonia (CAP) due to Gram-negative bacilli (GNB) is relatively rare. Previous studies from Asia, however, indicate a higher prevalence of GNB in CAP, but data, particularly from Southeast Asia, are limited.

Methods

This is a prospective observational study of 1451 patients ≥15 y of age with CAP from two hospitals in Cambodia between 2007 and 2010. The proportion of GNB was estimated. Risk factors and clinical characteristics of CAP due to GNB were assessed using logistic regression models.

Results

The prevalence of GNB was 8.6% in all CAP patients and 15.8% among those with a valid respiratory sample. GNB infection was independently associated with diabetes, higher leucocyte count and CAP severity. Mortality was higher in patients with CAP due to GNB.

Conclusions

We found a high proportion of GNB in a population hospitalized for CAP in Cambodia. Given the complex antimicrobial sensitivity patterns of certain GNBs and the rapid emergence of multidrug-resistant GNB, microbiological laboratory capacity should be strengthened and prospective clinical trials comparing empiric treatment algorithms according to the severity of CAP are needed.

Sticky Business: a syndrome of mucoid bacterial spread

A 70-year-old man presented with acute wrist pain concerning for septic arthritis. Shortly thereafter, he developed acute monocular vision loss and was diagnosed with endogenous endophthalmitis. Subsequent imaging revealed numerous visceral abscesses and a mycotic abdominal aortic aneurysm. Cultures, in conjunction with the clinical syndrome, were strongly suggestive of hypervirulent Klebsiella pneumoniae syndrome (hvKP). hvKP syndrome may present with multiple sites of infection or subsequent metastatic spread may develop; the liver, lungs, central nervous system and eye are most commonly involved. Prompt source control and intravenous antibiotic therapy leads to a cure in the majority of patients. This case highlights the risk factors, presentation, management and prognosis of this disease as well as its increasing incidence in North America and Europe.

Klebsiella pneumoniae infection biology: living to counteract host defences

Klebsiella species cause a wide range of diseases including pneumonia, urinary tract infections (UTIs), bloodstream infections and sepsis. These infections are particularly a problem among neonates, elderly and immunocompromised individuals. Klebsiella is also responsible for a significant number of community-acquired infections. A defining feature of these infections is their morbidity and mortality, and the Klebsiella strains associated with them are considered hypervirulent. The increasing isolation of multidrug-resistant strains has significantly narrowed, or in some settings completely removed, the therapeutic options for the treatment of Klebsiella infections. Not surprisingly, this pathogen has then been singled out as an 'urgent threat to human health' by several organisations. This review summarises the tremendous progress that has been made to uncover the sophisticated immune evasion strategies of K. pneumoniae. The co-evolution of Klebsiella in response to the challenge of an activated immune has made Klebsiella a formidable pathogen exploiting stealth strategies and actively suppressing innate immune defences to overcome host responses to survive in the tissues. A better understanding of Klebsiella immune evasion strategies in the context of the host-pathogen interactions is pivotal to develop new therapeutics, which can be based on antagonising the anti-immune strategies of this pathogen.

Hypervirulent Klebsiella pneumoniae (hypermucoviscous and aerobactin positive) infection over 6 years in the elderly in China: antimicrobial resistance patterns, molecular epidemiology and risk factor

BACKGROUND

The definition of hypervirulent Klebsiella pneumoniae (hvKp), traditionally regarded as hypermucoviscosity, is controversial. However, data based on both phenotype (hypermucoviscous) and genetic (aerobactin) criteria are limited.

METHODS

A retrospective study was conducted in 175 geriatric patients between January 2008 and January 2014. The clinical and molecular data, including antimicrobial susceptibility testing, extended-spectrum-β-lactamase (ESBL) production, virulence gene, and multilocus sequence typing of the hvKp-group (hypermucoviscosity and aerobactin positive) were compared with those of classic K. pneumoniae (cKp) isolates.

RESULTS

Of 175 Kp isolates, 45.7% were hvKp. In pathogenicity, K1, K2, magA, rmpA, and rmpA2 genes were strongly associated with hvKp (P < 0.01). In the hvKp group, invasive infections (P < 0.000), liver abscess (P = 0.008), abdominal infection (P = 0.002) and septic shock (P = 0.035) are significantly higher than cKp group. Patients with better nutritional status were frequently infected with hvKp. However, host inflammatory reaction is most severe in hvKp group. Patients with diabetes (odds ratio [OR] = 2.548) and digestive diseases (OR = 2.196) are more likely to be infected with hvKp. Importantly, the detection of hvKp isolates increased from January 2008 to January 2010, January 2010 to January 2012, and January 2010 to January 2014 (12, 30, and 48 isolates, respectively). Overall, 16.3% of hvKp isolates produced ESBLs and 20.0% were MDR-hvKp. Multivariate analysis implied that infection occurred in the ICU (OR = 5.826) and patients with indwelling stomach tubes (OR = 6.461) are independent risk factors for ESBL-hvKp infection.

CONCLUSIONS

HvKp, especially ESBL-hvKp and MDR-hvKp, is emerging in the elderly. It is essential to enhance clinical awareness and management of hvKp infections.

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

Background

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

Methods

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

Results

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

Conclusion

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

Characterization of a multidrug-resistant Klebsiella pneumoniae ST607-K25 clone responsible for a nosocomial outbreak in a neonatal intensive care unit

PURPOSE

Multidrug-resistant Klebsiella pneumoniae strains are regularly involved in hospital outbreaks. This study describes an ESBL-producing K. pneumoniae clone (ST607-K25) responsible for a nosocomial outbreak in a neonatal intensive care unit.

METHODOLOGY

Fourteen strains isolated from 13 patients were included. Antimicrobial susceptibility testing was performed by the agar diffusion method. A clonal link was first investigated by fingerprinting (ERIC-PCR and REP-PCR) then confirmed by MLST. Characterization was performed by molecular detection and identification of several drug resistance and virulence determinants.

RESULTS

All strains expressed the same antibiotype, combining ESBL production, fluoroquinolones and aminoglycoside resistance, except for one which remained susceptible to fluoroquinolones. Fingerprinting methods confirmed the clonal link and MLST identified a ST607 clone. Molecular investigations revealed: (I) genes encoding for two narrow-spectrum beta-lactamases (SHV-1 and TEM-1) and an ESBL (CTX-M-15); (II) absence of any chromosomal mutation in quinolone resistance-determining- regions (QRDR) of gyrA/gyrB and parC/parE genes; (III) genes encoding for three plasmid-mediated quinolone-resistance (PMQR) determinants: oqxAB (14/14), aac(6')-Ib-cr (14/14) and qnrB (13/14); (IV) production of a K25 capsule; and (V) carriage of three genes encoding for virulence factors: mrkD (type 3 fimbriae) (14/14), ybts (yersiniabactin) (12/14) and entB (enterobactin) (14/14).

CONCLUSION

We described a multidrug-resistant Kp ST607 clone responsible for a nosocomial outbreak in vulnerable and premature newborns. Molecular investigations allowed us to identify several resistance factors responsible for ESBL production (CTX-M-15) and quinolone resistance (three PMQR determinants). The detection of a gene (ybtS) belonging to the high-pathogenicity island yersiniabactin could partly explain its high colonization and diffusion potential.

Platelet reactivity in diabetic patients with invasive Klebsiella pneumoniae liver abscess syndrome

Objective

Platelets catalyze the development of hyperinflammation and microthrombosis and contribute to increases in accumulation of circulating platelet-leukocyte complex, the key event in the development of disseminated infection.

Subjects and methods

To determine the relationships of platelet activity in diabetic patients with invasive Klebsiella pneumoniae liver abscess syndrome (IKLAS), a total of 175 diabetic patients with community-acquired Klebsiella pneumoniae (KP) bacteremia were included in this study. We compared the platelet reactivity of 40 patients with IKLAS, 40 patients with non-IKLAS, and eight healthy controls using a whole-blood flow cytometry-based assay.

Results

Patients who were infected with strains expressing K₁/K₂ serotype (adjusted odds ratio [AOR], 8.81; 95% CI, 2.18–35.53) and those with HbA_1c ≥9% (AOR, 4.97; 95% CI, 1.73–14.23) were more likely to present with IKLAS, whereas those who had recent therapy with aspirin (AOR, 0.17; 95% CI, 0.04–0.79) were less likely to present with IKLAS. Among patients with IKLAS, patients with a poor glycemic control were more likely to present with hepatic venous thrombo-phlebitis than those with suboptimal or good glycemic control (P=0.03). Patients with IKLAS had a higher median fluorescence intensity of the platelet membrane expression of P-selectin than those with non-IKLAS (78.0 vs 28.0, P<0.001) and controls (78.0 vs 22.0, P< 0.001). The IKLAS group also demonstrated a significantly higher platelet-monocyte aggregation and higher plasma levels of PF-4 than the non-IKLAS group (47.0 vs 18.0 and 47.0 vs 4.0, respectively, both P <0.001) and controls (46.0 vs 24.0 and 46.0 vs 13.0, respectively, both P <0.001).

Conclusion

Diabetic patients with IKLAS demonstrated platelet hyperreactivity, which may be associated with a higher risk for vascular complications.

Clinical, Radiological and Bacteriological Profile of Lung Abscess - An Observational Hospital Based Study

BACKGROUND:

The incidence of lung abscess acquired in the community is unknown, but this is a common clinical problem encountered in developing countries. The incidence of lung abscess was high in the pre-antibiotic era but the advent of susceptible antibiotics it has reduced with an equal fall in mortality to 8.7%. With the emerging antibiotic resistance and change in the trends of bacteriological profile causing lung abscess, it is the need of time to reevaluate lung abscess.

AIM:

The study aimed to determine the clinical, radiological and bacteriological profile of lung abscess.

MATERIAL AND METHOD:

The study was a non-randomized prospective observational study conducted in the department of pulmonary medicine for 18 months. In the study, patients > 15 years of age with clinical features of lung abscess were recruited and were subjected to chest X-ray, routine blood test. Sputum gram stain and culture, as well as antibiotic sensitivity according to the organism, were evaluated. Reports of all investigations along with patient characteristics and risk factors were analysed statistically using SPSS 20.0.

RESULTS:

Forty-six cases of lung abscess were included, and the majority of patients were found to be adults with a mean age of 42.9 years with a male to female ratio of 6.6:1. The most common predisposing factor was an unhygienic oral cavity in 28% of cases with alcohol ingestion being the most important risk factor in 22% of cases. The most common organism found in lung abscess cases was Klebsiella pneumoniae, and they were sensitive to ceftazidime.

CONCLUSION:

Our study shows that Klebsiella pneumoniae should be considered an important pathogen in community-acquired lung abscesses.

Diversity of virulence level phenotype of hypervirulent Klebsiella pneumoniae from different sequence type lineage

BACKGROUND

Hypervirulent Klebsiella pneumoniae (hvKP) is emerging around the Asian-Pacific region and it is the major cause of the community-acquired pyogenic liver abscesses. Multidrug-resistant hypervirulent Klebsiella pneumoniae (MDR-hvKP) isolates were reported in France, China and Taiwan. However, the international-ally agreed definition for hvKP and the virulence level of hvKP are not clear.

RESULTS

In this study, 56 hvKP isolates were collected from March 2008 to June 2012 and investigated by string test, capsule serotyping, multilocus sequence typing (MLST), virulence gene detection and serum resistance assay. Among the 56 K. pneumoniae isolates, 64.3% had the hypermucoviscosity phenotype, meanwhile, 64.3% were the K1 serotype and 19.6% were the K2 serotype. Within the K1 serotype, 94.4% were ST23, and within the K2 serotype, ST65, ST86 and ST375 accounted for the same percentage 27.3%. The serum resistance showed statistically normal distribution. According to the 50% lethal dose of Galleria. mellonella infection model, hvKP isolates were divided into high virulence level group and moderate virulence level group. The ability of each method evaluating the virulence level of hvKP was assessed using the area under the receiver operating characteristic curve.

CONCLUSIONS

K1 ST23 K. pneumoniae was the most prevalent clone of the hvKP. However, K1 ST23 K. pneumoniae was the dominant clone in the moderate virulence level group. MLST was a relatively reliable evaluation method to discriminate the virulence level of hvKP in our study.

Hypervirulent Klebsiella pneumoniae: a Call for Consensus Definition and International Collaboration

Hypervirulent Klebsiella pneumoniae strains have higher potential to cause more severe and disseminated infections than classic K. pneumoniae strains. While initially reported from East Asian countries, cases have now been identified worldwide, sometimes in conjunction with extensive drug resistance. In this issue of the Journal of Clinical Microbiology, T. A. Russo et al. (J Clin Microbiol 56:e00776-18, 2018, https://doi.org/10.1128/JCM.00776-18) validated the diagnostic accuracy of biomarkers that differentiate hypervirulent K. pneumoniae strains from classic strains. This represents a major step forward in building a consensus definition and designing international studies aimed at elucidating the global epidemiology, clinical features, and outcome of this important pathogen.

Antimicrobial resistance and outcomes of community-onset bacterial bloodstream infections in patients with type 2 diabetes

OBJECTIVES

Antimicrobial resistance of bacterial pathogens in the diabetic population with infection is seldom investigated. This study evaluated the antimicrobial resistance and outcomes of community-onset bloodstream infections (CO-BSIs) in patients with diabetes.

METHODS

From 2007-2014, 1271 monomicrobial CO-BSIs and 178 polymicrobial CO-BSIs were identified in patients with type 2 diabetes from three teaching hospitals in Taiwan. Antimicrobial-resistant strains of the ten most prevalent bacterial pathogens in monomicrobial CO-BSIs were recorded and were defined according to individual drug resistance. The 30-day mortality rate and factors associated with outcome were analysed.

RESULTS

Antimicrobial-resistant strains were found in 33.7% (379/1125) of monomicrobial CO-BSIs involving the 10 most prevalent pathogens. The leading pathogens in these monomicrobial CO-BSIs were Staphylococcus spp. (33.8%; 430/1271), Escherichia coli (20.9%; 266/1271) and Klebsiella spp. (9.6%; 122/1271); antimicrobial-resistant strains accounted for 61.9%, 18.4% and 10.7% of each, respectively. A higher overall 30-day mortality rate was observed for patients infected by antimicrobial-resistant strains compared with antimicrobial-susceptible strains (9.5% vs. 5.5%; P=0.011, log-rank test). A lower serum albumin level was a predictor of mortality after adjusting for antimicrobial-resistant strains and C-reactive protein level.

CONCLUSIONS

Antimicrobial-resistant bacterial pathogens pose a serious threat to diabetic patients with CO-BSIs owing to a higher risk of mortality.

Phyto-mediated synthesis of silver nanoparticles using fucoidan isolated from Spatoglossum asperum and assessment of antibacterial activities

The present study was aimed to investigate the antibacterial efficacy of fucoidan mediated silver nanoparticles (Fu-AgNPs) synthesized from Spatoglossum asperum. The synthesized Fu-AgNPs were characterized by UV-visible, Field emission - scanning electron microscope (FE-SEM), Tranmission electron microscope (TEM), X-ray diffraction (XRD), Selected area electron diffraction (SAED) pattern, Energy-dispersive X-ray spectroscopy (EDAX), Fourier transform infrared spectroscopy (FT-IR), Dynamic light scattering (DLS) and Zeta potential analysis. The UV-visible spectrum of Fu-AgNPs exhibited a characteristic surface plasmon resonance (SPR) peak at 440 nm. The electron microscopic results revealed that the nanoparticles were spherical to oval in shape and are found to be 20 to 46 nm. Altogether the X-ray diffraction analysis showed that the Fu-AgNPs were crystalline in nature. The FT-IR spectrum confirmed the existence of CC stretching vibration of aromatic compounds and sulfated groups of fucoidan plays a major role in the synthesis of Fu-AgNPs. The biosynthesized Fu-AgNPs shows potential antibacterial activity against Klebsiella pneumoniae in agar bioassay, disk diffusion, reactive oxygen species, protein leakage and confocal laser scanning microscopy assays. Furthermore, Artemia toxicity assay results showed less mortality (3.3 ± 0.8%) even at higher concentration of Fu-AgNPs. Therefore, Fu-AgNPs can be effectively used as an antibacterial agent in the pharmaceutical fields.

Hypervirulent Klebsiella pneumoniae, a 5-year study in a French ICU

PURPOSE

Hypervirulent Klebsiella pneumoniae (hvKp) has emerged as a leading cause of severe community-acquired pneumonia, liver abscess and disseminated infection in the Far East. Data regarding the incidence, clinical features and microbiological characteristics related to hvKp infections in the Western world are scarce.

METHODOLOGY

The incidence, clinical features and microbiological characteristics of hvKp infections were investigated through a 5-year survey conducted in a single French intensive care unit. K. pneumoniae strains were screened for hypermucoviscosity based on a string test. Multilocus sequence typing and multiplex PCR analysis targeting virulence genes were performed on string test-positive strains.

RESULTS

Over a 53-month period, a total of 59 infections due to K. pneumoniae were identified including 26 community-onset infections. Twelve hvKp infections were documented, accounting for 46.1 % of community-acquired K. pneumoniae. Community-acquired pneumonia (n=6), aspiration pneumonia (n=4) and liver abscess (n=2) represented initial sites and mode of infection. Compared to non-hvKp infections, patients with hvKp infections displayed higher rates of multi-organ failure (83.3 % vs 35.7 %; P=0.04), but mortality rates were not different (50 % vs 35 %; P=0.71). Strains K1/ST23 (n=5) and K2/ST86 (n=5) predominated. All hvKp strains displayed wild-type susceptibility.

CONCLUSION

hvKp represent a potentially underestimated cause of fatal infections in the Western world.

Pseudomonas aeruginosa and Klebsiella pneumoniae Adaptation to Innate Immune Clearance Mechanisms in the Lung

Many different species of gram-negative bacteria are associated with infection in the lung, causing exacerbations of chronic obstructive pulmonary disease, cystic fibrosis (CF), and ventilator-associated pneumonias. These airway pathogens must adapt to common host clearance mechanisms that include killing by antimicrobial peptides, antibiotics, oxidative stress, and phagocytosis by leukocytes. Bacterial adaptation to the host is often evident phenotypically, with increased extracellular polysaccharide production characteristic of some biofilm-associated organisms. Given the relatively limited repertoire of bacterial strategies to elude airway defenses, it seems likely that organisms sharing the same ecological niche might also share common strategies to persistently infect the lung. In this review, we will highlight some of the major factors responsible for the adaptation of Pseudomonas aeruginosa to the lung, addressing how growth in biofilms enables persistent infection, relevant to, but not limited to, the pathogenesis of infection in CF. In contrast, we will discuss how carbapenem-resistant Klebsiella pneumoniae evade immune clearance, an organism often associated with ventilator-associated pneumonia and health-care-acquired pneumonias, but not a typical pathogen in CF.

Colonization, Infection, and the Accessory Genome of Klebsiella pneumoniae

Klebsiella pneumoniae is a Gram-negative pathogen that has a large accessory genome of plasmids and chromosomal gene loci. This accessory genome divides K. pneumoniae strains into opportunistic, hypervirulent, and multidrug-resistant groups and separates K. pneumoniae from two closely related species, Klebsiella variicola and Klebsiella quasipneumoniae. Some strains of K. pneumoniae act as opportunistic pathogens, infecting critically ill and immunocompromised patients. These K. pneumoniae are a common cause of health-care associated infections including pneumonia, urinary tract infections (UTIs), and bloodstream infections. K. variicola and K. quasipneumoniae are often clinically indistinguishable from opportunistic K. pneumoniae. Other strains of K. pneumoniae are hypervirulent, infecting healthy people in community settings and causing severe infections including pyogenic liver abscess, endophthalmitis, and meningitis. A third group of K. pneumoniae encode carbapenemases, making them highly antibiotic-resistant. These strains act as opportunists but are exceedingly difficult to treat. All of these groups of K. pneumoniae and related species can colonize the gastrointestinal tract, and the accessory genome may determine if a colonizing strain remains asymptomatic or progresses to cause disease. This review will explore the associations between colonization and infection with opportunistic, antibiotic-resistant, and hypervirulent K. pneumoniae strains and the role of the accessory genome in distinguishing these groups and related species. As K. pneumoniae infections become progressively more difficult to treat in the face of antibiotic resistance and hypervirulent strains, an increased understanding of the epidemiology and pathogenesis of these bacteria is vital.

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.

Molecular Epidemiology of Klebsiella pneumoniae Strains Causing Bloodstream Infections in Adults

Molecular epidemiology of Klebsiella pneumoniae bacteremic strains allows for a better understanding of preventive and therapeutic strategies. Clinical and microbiological characteristics of 348 K. pneumoniae bacteremia cases (2007-2009) were retrospectively characterized by multilocus sequence typing and extended-spectrum beta-lactamases (ESBL) production. Overall, 223 (64.08%) cases were nosocomial (NA), 58 (16.67%) healthcare associated, and 67 (19.25%) community acquired. The main infection origins were urinary tract (16.6%, 50.0%, and 43.3%), biliary tract (10.8%, 24.2%, and 31.3%), and catheter-related infection (39.9%, 5.2%, and 0%). The 30-day mortality rate was around 20%. The rates of resistance were around 45% the highest being among NA cases, and ESBL production was detected in 7.2% of cases. A total of 161 different sequence types were grouped into 13 clonal sets by e-burst analysis. No relationship could be established between clonal sets and the origin of infection or the healthcare-related settings. The high genetic variability among the isolates suggests their intrapatient endogenous origin.

Serotype and virulence genes of Klebsiella pneumoniae isolated from mink and its pathogenesis in mice and mink

In the study, 15 K. pneumoniae strains were isolated from the mink experiencing respiratory distress in mideastern Shandong province, China, and the prevalence of K. pneumoniae in the sampled mink was 11.9% (15/126). Fourteen (93.33%) of the 15 K. pneumoniae isolates were identified as serotype K2 and hypermucoviscosity phenotype. The 12 virulence-associated genes of the K. pneumoniae isolates were tested. The prevalence of the wabG gene for the isolates were 100% (15/15), the ureA gene 100% (15/15), the rmpA gene 93.33% (14/15), the aerobactin gene 93.33% (14/15), the uge gene 93.33% (14/15), the IucB gene 80% (12/15) and the ybtA gene 13.33% (2/15). But the other five genes, fim, iroNB, wcaG, alls and kfuBC, gave a negative PCR reaction in the 15 isolates, respectively. The animal experiments using K. pneumoniae-SD-12 and K. pneumoniae-SD-21 demonstrated that the serotype K2 was high virulence for mice and mink. These finding implied there exist potential threat that K. pneumoniae pathogens could transmit to human, especially the fur animal farm workers and residents lived near the fur animal farms. Therefore, the etiology and epidemiological surveillance of K. pneumoniae in mink should be strengthened for people's public health.

Antimicrobial Resistance of Hypervirulent Klebsiella pneumoniae: Epidemiology, Hypervirulence-Associated Determinants, and Resistance Mechanisms

Klebsiella pneumoniae is one of the most clinically relevant species in immunocompromised individuals responsible for community-acquired and nosocomial infections, including pneumonias, urinary tract infections, bacteremias, and liver abscesses. Since the mid-1980s, hypervirulent K. pneumoniae, generally associated with the hypermucoviscosity phenotype, has emerged as a clinically significant pathogen responsible for serious disseminated infections, such as pyogenic liver abscesses, osteomyelitis, and endophthalmitis, in a generally younger and healthier population. Hypervirulent K. pneumoniae infections were primarily found in East Asia and now are increasingly being reported worldwide. Although most hypervirulent K. pneumoniae isolates are antibiotic-susceptible, some isolates with combined virulence and resistance, such as the carbapenem-resistant hypervirulent K. pneumoniae isolates, are increasingly being detected. The combination of multidrug resistance and enhanced virulence has the potential to cause the next clinical crisis. To better understand the basic biology of hypervirulent K. pneumoniae, this review will provide a summarization and discussion focused on epidemiology, hypervirulence-associated factors, and antibiotic resistance mechanisms of such hypervirulent strains. Epidemiological analysis of recent clinical isolates in China warns the global dissemination of hypervirulent K. pneumoniae strains with extensive antibiotic resistance in the near future. Therefore, an immediate response to recognize the global dissemination of this hypervirulent strain with resistance determinants is an urgent priority.

Draft Genome Sequences of Clinical and Nonclinical Isolates of Klebsiella spp. Exhibiting Nonheritable Tolerance toward Antimicrobial Compounds

A clinical isolate and a nonclinical isolate of Klebsiella pneumoniae were found to exhibit nonheritable tolerance in response to antimicrobial compounds. The draft genome sequences of both isolates are presented here.

Virulence Characteristics of Carbapenem-Resistant Klebsiella pneumoniae Strains from Patients with Necrotizing Skin and Soft Tissue Infections

Two types of Klebsiella pneumoniae (KP) strains are currently emerging: hypervirulent (hvKP) strains and carbapenem-resistant (CR-KP) strains. To date, these two strain types rarely overlap. Recent reports, however, suggest that CR-KP strains are increasing in virulence. hvKP strains frequently present as highly invasive infections, such as necrotizing skin and soft tissue infections (NSSTI). To examine whether CR-KP strains with features of hvKP were present in our U.S. hospital, we retrospectively identified four cases of CR-KP NSSTI diagnosed between January 2012 and January 2016. Whole-genome sequencing was used to perform multilocus sequence typing, capsular typing, and identification of virulence and antimicrobial resistance genes. Additionally, the virulence of each isolate was determined in vitro and using murine pneumonia and subcutaneous infection models. We identified one CR-KP isolate that possessed features of hypervirulent KP, including a hypermucoviscous phenotype, K2 capsule, and resistance to phagocytosis. Of the four CR-KP isolates, two had no evidence of enhanced pathogenicity in either mouse model, demonstrating that low-virulence strains can cause NSSTI in immunosuppressed patients. The remaining two isolates exhibited low virulence in the pneumonia model but high virulence in the subcutaneous infection model, suggesting that the virulence attributes of these isolates are adapted to causing NSSTI.

Etiology of community-onset monomicrobial bacteremic pneumonia and its clinical presentation and outcome: Klebsiella and Pseudomonas matters

To describe the difference of the clinical features, bacteremia severity, and outcome of patient with community-onset bacteremic pneumonia between Pseudomonas, Klebsiella, and other causative microorganisms, the total 278 adults with community-onset monomicrobial bacteremic pneumonia were studied in a retrospective cohort. Klebsiella (61 patients, 21.9%) and Pseudomonas (22, 7.9%) species was the leading and the fifth common pathogen, respectively. More patients having initial presentation with critical illness (a Pitt bacteremia score ≥ 4) and a fatal comorbidity (McCabe classification) as well as a higher short- (30-day) or long-term (90-day) mortality rate was evidenced in patients infected with Klebsiella or Pseudomonas species, compared to other causative microorganisms. Compared to patients in the Klebsiella group, more frequencies of recent chemotherapy and an initial presentation of febrile neutropenia, and less proportions of diabetes mellitus were disclosed among those in the Pseudomonas group. Of importance, a significantly differential survival curve between Klebsiella or Pseudomonas species and other species during 30-day or 90-day period after bacteremia onset but a similarity of Pseudomonas and Klebsiella species was evidenced, using the Cox-regression after adjusting the independent predictors of 30-day mortality. Conclusively, of pathogens causing community-onset bacteremic pneumonia, Klebsiella and Pseudomonas species should be recognized as the highly virulent pathogens and resulted in poor short- and long-term prognoses.

Metabolite Transporter PEG344 Is Required for Full Virulence of Hypervirulent Klebsiella pneumoniae Strain hvKP1 after Pulmonary but Not Subcutaneous Challenge

Hypervirulent Klebsiella pneumoniae (hvKP) is an emerging pathotype that is capable of causing tissue-invasive and organ- and life-threatening infections in healthy individuals from the community. Knowledge on the virulence factors specific to hvKP is limited. In this report, we describe a new factor (PEG344) that increases the virulence of hvKP strain hvKP1. peg-344 is present on the hvKP1 virulence plasmid, is broadly prevalent among hvKP strains, and has increased RNA abundance when grown in human ascites. An isogenic derivative of hvKP1 (hvKP1Δpeg-344) was constructed and compared with its wild-type parent strain in in vitro, ex vivo, and infection model studies. Both survival and competition experiments with outbred CD1 mice demonstrated that PEG344 was required for full virulence after pulmonary challenge but, interestingly, not after subcutaneous challenge. In silico analysis suggested that PEG344 serves as an inner membrane transporter. Compared to hvKP1, a small but significant decrease in the growth/survival of hvKP1Δpeg-344 was observed in human ascites, but resistance to the bactericidal activity of complement was similar. These data suggested that PEG344 may transport an unidentified growth factor present in ascites. The data presented are important since they expand our limited knowledge base on virulence factors unique to hvKP, which is needed to lay the groundwork for translational approaches to prevent or treat these devastating infections.

Complete Nucleotide Sequence of Klebsiella pneumoniae Bacteriophage vB_KpnM_KpV477

The double-stranded DNA (dsDNA) bacteriophage vB_KpnM_KpV477, with a broad spectrum of lytic activity against Klebsiella pneumoniae, including strains of capsular serotypes K1, K2, and K57, was isolated from a clinical sample. The phage genome comprises 168,272 bp, with a G+C content of 39.3%, and it contains 275 putative coding sequences (CDSs) and 17 tRNAs.

Multidrug-Resistant Bacteria in the Community: Trends and Lessons Learned

Multidrug resistant (MDR) bacteria are one of the most important threats to public health. Typically, MDR bacteria are associated with nosocomial infections. However, some MDR bacteria have become prevalent causes of community-acquired infections. The spread of MDR bacteria into the community is a crucial development, and is associated with increased morbidity, mortality, health care costs, and antibiotic use. Factors associated with community dissemination of MDR bacteria overlap but are distinct from those associated with nosocomial spread. Prevention of further community spread of MDR bacteria is of the utmost importance, and requires a multidisciplinary approach involving all stakeholders.

The KP1_4563 gene is regulated by the cAMP receptor protein and controls type 3 fimbrial function in Klebsiella pneumoniae NTUH-K2044

Klebsiella pneumoniae (K. pneumoniae) is an opportunistic pathogen that can adhere to host cells or extracellular matrix via type 1 and type 3 fimbriae. KP1_4563 is a gene encoding a hypothetical protein in K. pneumoniae NTUH-K2044. KP1_4563 is located between the type 1 and type 3 fimbrial gene clusters and is likely associated with fimbrial function given its putative conserved domains of unknown function (DUF1471). Cyclic AMP receptor protein (CRP) regulates virulence-related gene expression and is a crucial transcriptional regulator in many bacteria. The predicted DNA recognition motif of CRP is present in the KP1_4563 promoter region. This study aimed to investigate the function of KP1_4563 in fimbriae and its transcriptional regulation mechanism by CRP. We generated Kp-Δ4563 mutant and complementation strains. We utilized phenotype and adhesion assays to evaluate the role of KP1_4563 in fimbriae. We conducted quantitative RT-PCR (qRT-PCR), LacZ fusion, electrophoretic mobility shift, and DNase I footprinting assays to study the transcriptional regulation of KP1_4563 gene by CRP. We found that KP1_4563 negatively regulates the function of type 3 fimbriae. Compared with NTUH-K2044, the absence of KP1_4563 enhanced the ability of Kp-Δ4563 to adhere to A549 cells. CRP negatively regulates KP1_4563 by directly binding to its promoter region. KP1_4563 plays an important role in type 3 fimbrial function. This novel insight will assist in the development of strategies for preventing K. pneumoniae infection.

Two T7-like Bacteriophages, K5-2 and K5-4, Each Encodes Two Capsule Depolymerases: Isolation and Functional Characterization

Two Klebsiella bacteriophages K5-2 and K5-4, which are able to infect and grow on either capsular types K30/K69 and K5 or K8 and K5 of Klebsiella strains, were isolated and characterized. Each phage contained two open reading frames (ORFs), which encoded two putative capsule depolymerases, respectively. The first ORF encoded tail fiber proteins, which have K30/K69 depolymerase and K8 depolymerase activities. The second ORF encoded hypothetical proteins, which are almost identical in amino acid sequences, and have K5 depolymerase activity. Alcian blue staining of enzyme-treated capsular polysaccharides (CPS) showed that purified depolymerases can cleave purified Klebsiella CPS in vitro and liberate monosaccharaides. Capsule K5 deletion mutants were not lysed by either phage, suggesting that the capsule was essential for phage infection. Bacterial killing was observed when incubated Klebsiella strains with phages but not with purified depolymerases. Treatment with the K5-4 phage significantly increased the survival of mice infected with a K. pneumoniae K5 strain. In conclusion, two dual host-specific Klebsiella phages and their tailspikes exhibit capsule depolymerase activity were characterized. Each phage and phage-encoded depolymerase has specificity for capsular type K30/K69, K8 or K5, and could be used for the typing and treatment of K. pneumoniae infection.

Pneumonia is an independent risk factor for pyogenic liver abscess: A population-based, nested, case-control study

Background

Bacteremic pneumonia is considered a potential cause of distal organ abscess formation. Therefore, we hypothesize that pneumonia is a risk factor for pyogenic liver abscess (PLA).The aim of this study is to explore the association between pneumonia and PLA.

Methodology/Principal findings

A nationwide, population-based, nested, case–control study was conducted using data from the Taiwan National Health Insurance Research Database. In total, 494 patients with PLA and 1,976 propensity score matched controls were enrolled. Conditional logistic regression was used to estimate adjusted odds ratios (aORs) in patients with exposure to pneumonia before PLA. After matched and adjusted for confounding factors including age, sex, urbanization, income, chronic liver disease, alcohol-related disease, biliary stone, chronic kidney disease, diabetes mellitus, chronic liver disease, and cancer, hospitalization for pneumonia remained an independent risk factor for PLA with an aORs of 2.104 [95% confidence interval (CI) = 1.309–3.379, p = 0.0021]. Moreover, the aORs were significantly higher among patients hospitalized for pneumonia within 30 days (aORs = 10.73, 95% CI = 3.381–34.054), 30–90 days (aORs = 4.698, 95% CI = 1.541–14.327) and 90–180 (aORs = 4.000, 95% CI = 1.158–13.817) days before PLA diagnosis.

Conclusion

Pneumonia is an independent risk factor for subsequent PLA. Moreover, hospitalization for pneumonia within 180 days before PLA diagnosis was associated with an increased risk of PLA.

Propensity score matched analysis comparing the clinical outcome of Klebsiella pneumoniae and Escherichia coli causing community-onset monomicrobial bacteremia

Bacteremia is a life-threatening condition that is associated with substantial healthcare costs. Escherichia coli and Klebsiella pneumoniae are the leading causes of community-onset gram-negative bacteremia. However, a comprehensive comparison between these pathogens involved in bacteremia episodes has yet to be reported.In this retrospective cohort study, adults with community-onset monomicrobial bacteremia caused by E coli or K pneumoniae were recruited in the emergency department of a medical center during a 6-year period, and the clinical variables were collected retrospectively from medical records. The complicated abscess occurrence was determined through imaging studies, according to the opinion of an infectious disease consultant. According to the independent predictors of 28-day mortality identified through multivariate regression analyses, patients in the E coli group were propensity score matched (PSM) in a 1:1 ratio to those in the K pneumoniae group.A total of 274 and 823 adults with K pneumoniae and E coli bacteremia were included in the present study. The K pneumoniae group had more patients with fatal comorbidities (McCabe classification), critical illness (Pitt bacteremia score ≥ 4) at bacteremia onset, and initial syndrome (e.g., severe sepsis and septic shock) as well as a higher crude mortality rate than did the E coli group. After appropriate matching, no significant differences were observed in the critical illness at bacteremia onset, initial syndrome, major comorbidities, and comorbidity severity of the 2 groups (E coli, n = 242; K pneumoniae, n = 242). Furthermore, despite similar 14- and 28-day crude mortality rates between the 2 PSM groups, more frequent abscess occurrences and a longer length of hospitalization were observed in the K pneumoniae group than in the E coli group.Conclusively, numerous clinical features at initial presentations varied between the E coli and K pneumoniae groups. Despite conducting a PSM analysis to control the differences in the baseline characteristics, a longer length of hospitalization and more frequent abscess occurrences were observed in the K pneumoniae group than in the E coli group.

Septicemic invasive Klebsiella pneumoniae infection in a cynomolgus monkey (Macaca fascicularis) with severe diffused suppurative meningoencephalitis

A 2-year-old male cynomolgus monkey (Macaca fascicularis) showed neurological symptoms during quarantine for importation into Japan, and was euthanized due to poor prognosis. Gross anatomical examination revealed a hemorrhagic lesion around the lateral ventricle in the cerebrum. Histologically, severe diffused suppurative meningitis and ventriculitis were detected with numerous Gram-negative bacilli in the cerebrum. Immunohistochemically, the bacilli were positively stained with an antibody against Klebsiella pneumoniae. The bacterium was isolated from the liver, and it was confirmed to be K. pneumoniae by 16S rDNA sequencing. The isolate displayed a hypermucoviscosity phenotype, was positive for the rmpA and k₂A genes, and demonstrated multidrug resistance. These results suggest that invasive K. pneumoniae can cause septicemic infection, characterized by severe diffused suppurative meningoencephalitis in monkeys.

Delay in Human Neutrophil Constitutive Apoptosis after Infection with Klebsiella pneumoniae Serotype K1

Klebsiella pneumoniae serotype K1 is a major cause of invasive syndrome defined by liver abscess with metastatic infections at other body sites. This culprit is known to be resistant to neutrophil phagocytosis and bactericidal activity. We hypothesized that K. pneumoniae serotype K1 might regulate neutrophil apoptosis and enhance the survival of the infected neutrophils that might serve as a vector for dissemination of the bacteria. Two serotypes of K. pneumoniae, KP-M1 isolated from a patient with liver abscess and DT-X (an acapsular mutant strain of KP-M1), were used to infect human neutrophils. The infected neutrophils were examined for their cytotoxicity, annexin V staining, proteins, DNA fragmentation, cytokine production, and viability that are involved in apoptosis. We found that KP-M1 was not destroyed and the ingested bacteria survived within neutrophils. While the uninfected neutrophils became apoptotic within 10 h, the neutrophils infected with KP-M1 could survive up to 24 h post infection. Constitutive apoptosis of KP-M1-infected neutrophils was significantly delayed compared to that of DT-X-infected or uninfected neutrophils (p < 0.01). KP-M1 modulated the anti-apoptotic effects by down-regulating the ratio of Bax to Bcl-2 and Mcl-1, and then delayed caspase-3 activation in the neutrophils, which was accompanied by inducing the anti-apoptotic cytokine, IL-8. These data suggest that K. pneumoniae serotype K1 can prolong the lifespan of infected neutrophils by delaying constitutive apoptosis within the first several hours of infection.

Genome Sequence of Klebsiella pneumoniae Bacteriophage PMBT1 Isolated from Raw Sewage

A bacteriophage virulent for extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae strain 182 was isolated from sewage. The double-stranded DNA (dsDNA) genome showed high similarity to the genomes of other Klebsiella pneumoniae phages. It comprises 175,206 bp with a mol% G+C content of 41.9 and contains 276 putative open reading frames (ORFs) and one tRNA.

Generation and Validation of the iKp1289 Metabolic Model for Klebsiella pneumoniae KPPR1

Klebsiella pneumoniae has a reputation for causing a wide range of infectious conditions, with numerous highly virulent and antibiotic-resistant strains. Metabolic models have the potential to provide insights into the growth behavior, nutrient requirements, essential genes, and candidate drug targets in these strains. Here we develop a metabolic model for KPPR1, a highly virulent strain of K. pneumoniae. We apply a combination of Biolog phenotype data and fitness data to validate and refine our KPPR1 model. The final model displays a predictive accuracy of 75% in identifying potential carbon and nitrogen sources for K. pneumoniae and of 99% in predicting nonessential genes in rich media. We demonstrate how this model is useful in studying the differences in the metabolic capabilities of the low-virulence MGH 78578 strain and the highly virulent KPPR1 strain. For example, we demonstrate that these strains differ in carbohydrate metabolism, including the ability to metabolize dulcitol as a primary carbon source. Our model makes numerous other predictions for follow-up verification and analysis.

Panel strain of Klebsiella pneumoniae for beta-lactam antibiotic evaluation: their phenotypic and genotypic characterization

Klebsiella pneumoniae is responsible for numerous infections caused in hospitals, leading to mortality and morbidity. It has been evolving as a multi-drug resistant pathogen, acquiring multiple resistances such as such as horizontal gene transfer, transposon-mediated insertions or change in outer membrane permeability. Therefore, constant efforts are being carried out to control the infections using various antibiotic therapies. Considering the severity of the acquired resistance, we developed a panel of strains of K. pneumoniae expressing different resistance profiles such as high-level penicillinase and AmpC production, extended spectrum beta-lactamases and carbapenemases. Bacterial strains expressing different resistance phenotypes were collected and examined for resistance genes, mutations and porin alterations contributing to the detected phenotypes. Using the Massive parallel sequencing (MPS) technology we have constructed and genotypically characterized the panel strains to elucidate the multidrug resistance. These panel strains can be used in the clinical laboratory as standard reference strains. In addition, these strains could be significant in the field of pharmaceuticals for the antibiotic drug testing to verify its efficiency on pathogens expressing various  resistances.

Community-Acquired Pneumonia in the Asia-Pacific Region

Community-acquired pneumonia (CAP) is an important cause of mortality and morbidity worldwide. Aging population, dense urbanization, and poor access to health care make the Asia-Pacific region vulnerable to CAP. The high incidence of CAP poses a significant health and economic burden in this region. Common etiologic agents in other global regions including Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, Chlamydophila pneumoniae, Staphylococcus aureus, and respiratory viruses are also the most prevalent pathogens in the Asia-Pacific region. But the higher incidence of Klebsiella pneumoniae and the presence of Burkholderia pseudomallei are unique to the region. The high prevalence of antimicrobial resistance in S. pneumoniae and M. pneumoniae has been raising the need for more prudent use of antibiotics. Emergence and spread of community-acquired methicillin-resistant S. aureus deserve attention, while the risk has not reached significant level yet in cases of CAP. Given a clinical and socioeconomic importance of CAP, further effort to better understand the epidemiology and impact of CAP is warranted in the Asia-Pacific region.

Community-acquired meningitis caused by a CG86 hypervirulent Klebsiella pneumoniae strain: first case report in the Caribbean

Background

Community-acquired bacterial meningitis due to Klebsiella pneumoniae has mainly been described in Southeast Asia and has a poor prognosis. Severe invasive infections caused by K. pneumoniae, including meningitis, are often due to hypervirulent strains (hvKP), which are characterized by capsular serotypes K1 and K2, a gene responsible for hypermucoviscosity, and the cluster for synthesis of the siderophore aerobactin.

Case presentation

A 55 year old man with a history of essential hypertension, benign prostate hyperplasia, hyperlipidemia, obstructive sleep apnea, and chronic alcoholism was admitted for meningitis due to Klebsiella pneumoniae with a wild-type susceptibility profile. Its genomic features were consistent with a capsular K2 strain belonging to clonal group 86 (CG86) displaying the large virulence of Klebsiella plasmid (pLVPK) with heavy metal resistance gene clusters, aerobactin, rmpA.

Conclusion

This is the first case of community-acquired meningitis caused by a hypervirulent strain of hvKP ever reported in the Caribbean.