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      Resistance of hypervirulent Klebsiella pneumoniae to both intracellular and extracellular killing of neutrophils

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          Abstract

          Hypervirulent Klebsiella pneumoniae (HvKP) is hypermucoviscous organism, carrying genes of rmpA and aerobactin, causing serious community-acquired infection and metastatically spread in young healthy hosts. Neutrophils play an important role during innate immune response against bacterial infection by phagocytosis and neutrophil extracellular traps (NETs). Whether neutrophils can effectively defend against HvKP remains unclear. In this study, we observed that the HvKP was significantly more resistant to neutrophil-mediated phagocytosis and intracellular killing than classic Klebsiella pneumoniae (cKP) isolates. Although both HvKP and cKP induced NETs under scanning electron microscopy and confocal microscopy, more cKP than HvKP were trapped in NETs, and the killing by intracellular and extracellular mechanisms of neutrophils was detected only on cKP. Together, our results demonstrated that HvKP resisted to both intracellular and extracellular killing of neutrophils.

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          A global emerging disease of Klebsiella pneumoniae liver abscess: is serotype K1 an important factor for complicated endophthalmitis?

          Over the past two decades in Taiwan, pyogenic liver abscess has usually been caused by a single microorganism, Klebsiella pneumoniae, and is frequently associated with the serious complication of endophthalmitis, especially in diabetic patients. However, the relationship between the clinical presentation and bacterial factors remains unclear. The aim of this study was to investigate the clinical features of patients and the serotype and ribotype of K pneumoniae liver abscess. From July 1991 to June 1998, a total of 134 cases of K pneumoniae liver abscess with 248 K pneumoniae isolates from the same patients were collected from two large medical centres in northern Taiwan. Clinical data were collected from medical records. Serotyping and ribotyping were performed using the countercurrent immunoelectrophoresis method and automated Riboprinter. Serotyping revealed that the most common serotypes were K1 (63.4%) and K2 (14.2%). K1 isolates occurred at a significantly higher frequency (p<0.01) than all other serotypes. Among 134 patients, 105 (78.4%) had suffered from diabetes mellitus for 3-15 years. Fourteen patients (10.4%) had metastatic infection to the eye causing septic endophthalmitis. Liver aspirates, and blood and vitreous pus cultures yielded the same serotype of K pneumoniae in all patients. Among patients with septic endophthalmitis, 92.3% (13/14) were diabetic, and 85.7% (12/14) of the isolates belonged to serotype K1. For molecular typing, different degrees of genetic polymorphism among isolates with the same K1 serotype suggested no particular prevalence of any one strain in K pneumoniae liver abscess. K pneumoniae serotype K1 was significantly associated with liver abscess and the complication of endophthalmitis, especially in diabetic patients. Physicians should request an immediate report of serotyping and susceptibility test results simultaneously if a diagnosis of pyogenic liver abscess has been made so that early and appropriate management for possible complications will not be delayed. The use of ceftriaxone because of its higher concentration in the aqueous humor is suggested to decrease the chance of septic endophthalmitis.
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            Capsule and D-alanylated lipoteichoic acids protect Streptococcus pneumoniae against neutrophil extracellular traps.

            Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. Pneumococci can counteract the action of neutrophils with an antiphagocytic capsule and through electrochemical repulsion of antimicrobial peptides via addition of positive charge to the surface. Pneumococci are captured, but not killed in neutrophil extracellular traps (NETs). Here, we study the role of the polysaccharide capsule and lipoteichoic acid (LTA) modification on pneumococcal interaction with NETs. Expression of capsule (serotypes 1, 2, 4 and 9V) significantly reduced trapping by NETs, but was not required for resistance to NET-mediated killing. Pneumococci contain a dlt operon that mediates the incorporation of d-alanine residues into LTAs, thereby introducing positive charge. Genetic inactivation of dltA in non-encapsulated pneumococci rendered the organism sensitive to killing by antimicrobial components present in NETs. However, the encapsulated dltA mutant remained resistant to NET-mediated killing in vitro. Nevertheless, in a murine model of pneumococcal pneumonia, the encapsulated dltA-mutant strain was outcompeted by the wild-type upon invasion into the lungs and bloodstream. This suggests a non-redundant role for LTA alanylation in pneumococcal virulence at the early stage of invasive disease when capsule expression has been shown to be low.
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              Seroepidemiology of Klebsiella pneumoniae colonizing the intestinal tract of healthy chinese and overseas chinese adults in Asian countries

              Background Capsular serotypes K1 and K2 of Klebsiella pneumoniae are thought to the major virulence determinants responsible for liver abscess. The intestine is one of the major reservoirs of K. pneumoniae, and epidemiological studies have suggested that the majority of K. pneumoniae infections are preceded by colonization of the gastrointestinal tract. The possibility of fecal-oral transmission in liver abscess has been raised on the basis of molecular typing of isolates. Data on the serotype distribution of K. pneumoniae in stool samples from healthy individuals has not been previously reported. This study investigated the seroepidemiology of K. pneumoniae isolates from the intestinal tract of healthy Chinese in Asian countries. Stool specimens from healthy adult Chinese residents of Taiwan, Japan, Hong Kong, China, Thailand, Malaysia, Singapore, and Vietnam were collected from August 2004 to August 2010 for analysis. Results Serotypes K1/K2 accounted for 9.8% of all K. pneumoniae isolates from stools in all countries. There was no significant difference in the prevalence of K1/K2 isolates among the countries excluding Thailand and Vietnam. The antimicrobial susceptibility pattern was nearly the same in K. pneumoniae isolates. The result of pulsed-field gel electrophoresis revealed no major clonal cluster of serotype K1 isolates. Conclusions The result showed that Chinese ethnicity itself might be a major factor predisposing to intestinal colonization by serotype K1/K2 K. pneumoniae isolates. The prevalent serotype K1/K2 isolates may partially correspond to the prevalence of K. pneumoniae liver abscess in Asian countries.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                1932-6203
                10 March 2017
                2017
                : 12
                : 3
                : e0173638
                Affiliations
                [001]Department of Microbiology, Chinese General Hospital of People’s Liberation Army, Beijing, China
                Louisiana State University, UNITED STATES
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                • Conceptualization: LFW DXS.

                • Data curation: LFW HW DXS.

                • Formal analysis: LFW DXS.

                • Funding acquisition: DXS.

                • Investigation: LFW HW DXS.

                • Methodology: LFW HW DXS.

                • Project administration: LFW DXS.

                • Resources: LFW HW YNM DXS.

                • Supervision: LFW DXS.

                • Validation: LFW HW DXS.

                • Visualization: LFW DXS.

                • Writing – original draft: LFW.

                • Writing – review & editing: LFW DXS.

                Author information
                http://orcid.org/0000-0002-2645-9093
                http://orcid.org/0000-0002-0232-1217
                Article
                PONE-D-16-49533
                10.1371/journal.pone.0173638
                5345822
                28282434
                d82ff594-57d4-40f1-a927-8ee4a90f253b
                © 2017 Wang et al

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                History
                : 19 December 2016
                : 23 February 2017
                Page count
                Figures: 5, Tables: 0, Pages: 10
                Funding
                Funded by: funder-id http://dx.doi.org/10.13039/501100001809, National Natural Science Foundation of China;
                Award ID: 81472012
                Award Recipient :
                This work was supported by the National Natural Science Foundation of China (grant number 81472012). DXS acquired the funder, who participated in study design, decision to publish, and preparation of the manuscript.
                Categories
                Research Article
                Biology and Life Sciences
                Cell Biology
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                Animal Cells
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                Animal Cells
                Immune Cells
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                Biology and Life Sciences
                Immunology
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