Molecular analysis of type 3 fimbrial genes from <Emphasis Type="Italic">Escherichia coli</Emphasis>, <Emphasis Type="Italic">Klebsiella</Emphasis> and <Emphasis Type="Italic">Citrobacter</Emphasis> species

Background  

Catheter-associated urinary tract infection (CAUTI) is the most common nosocomial infection in the United States and is caused by a range of uropathogens. Biofilm formation by uropathogens that cause CAUTI is often mediated by cell surface structures such as fimbriae. In this study, we characterised the genes encoding type 3 fimbriae from CAUTI strains of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Citrobacter koseri and Citrobacter freundii.     

Seroepidemiology of <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> 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.     

Klebsiella pneumoniae triggers a cytotoxic effect on airway epithelial cells

Background  

Klebsiella pneumoniae is a capsulated Gram negative bacterial pathogen and a frequent cause of nosocomial infections. Despite its clinical relevance, little is known about the features of the interaction between K. pneumoniae and lung epithelial cells on a cellular level, neither about the role of capsule polysaccharide, one of its best characterised virulence factors, in this interaction.     

Identification,expression and serological evaluation of the recombinant ATP synthase beta subunit of <Emphasis Type="Italic">Mycoplasma pneumoniae</Emphasis>

Background  

Mycoplasma pneumoniae is responsible for acute respiratory tract infections (RTIs) common in children and young adults. As M. pneumoniae is innately resistant to β-lactams antibiotics usually given as the first-line treatment for RTIs, specific and early diagnosis is important in order to select the right treatment. Serology is the most used diagnostic method for M. pneumoniae infections.     

<Emphasis Type="Italic">Chlamydia pneumoniae</Emphasis> induces aponecrosis in human aortic smooth muscle cells

Background  

The intracellular bacterium Chlamydia pneumoniae is suspected to play a role in formation and progression of atherosclerosis. Many studies investigated cell death initiation versus inhibition by Chlamydia pneumoniae in established cell lines but nothing is known in primary human aortic smooth muscle cells, a cell type among others known to be involved in the formation of the atherosclerotic plaque. Type of cell death was analyzed by various methods in primary aortic smooth muscle cells after infection with Chlamydia pneumoniae to investigate a possible pathogenic link in atherosclerosis.     

Validity and reliability of two brief physical activity questionnaires among Spanish-speaking individuals of Mexican descent

Background

Klebsiella pneumoniae is a leading cause of hospital-acquired urinary tract infections and pneumonia worldwide, and is responsible for many cases of pyogenic liver abscess among diabetic patients in Asia. A defining characteristic of this pathogen is the presence of a thick, exterior capsule that has been reported to play a role in biofilm formation and to protect the organism from threats such antibiotics and host immune challenge.

Findings

We constructed two knockout mutants of K. pneumoniae to investigate how perturbations to capsule biosynthesis alter the cellular phenotype. In the first mutant, we deleted the entire gene cluster responsible for biosynthesis of the extracellular polysaccharide capsule. In the second mutant, we deleted the capsule export subsystem within this cluster. We find that both knockout mutants have lower amounts of capsule but produce greater amounts of biofilm. Moreover, one of the two mutants abolishes fimbriae expression as well.

Conclusions

These results are expected to provide insight into the interaction between capsule biosynthesis, biofilm formation, and fimbriae expression in this organism.     

<Emphasis Type="Italic">Chlamydophila pneumoniae</Emphasis> derived from inclusions late in the infectious cycle induce aponecrosis in human aortic endothelial cells

Background  

Atherosclerosis is still the leading cause of death in the western world. Besides known risk factors studies demonstrating Chlamydophila pneumoniae (C. pneumoniae) to be implicated in the progression of the disease, little is known about C. pneumoniae infection dynamics. We investigated whether C. pneumoniae induce cell death of human aortic endothelial cells, a cell type involved in the initiation of atherosclerosis, and whether chlamydial spots derive from inclusions.     

Differences in the BAL proteome after <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> infection in wild type and SP-A-/- mice

Background  

Surfactant protein-A (SP-A) has been shown to play a variety of roles related to lung host defense function. Mice lacking SP-A are more susceptible to infection than wild type C57BL/6 mice. We studied bronchoalveolar lavage (BAL) protein expression in wild type and SP-A-/- mice infected with Klebsiella pneumoniae by 2D-DIGE.     

Interactions between flagellar and type III secretion proteins in <Emphasis Type="Italic">Chlamydia pneumoniae</Emphasis>

Background  

Flagellar secretion systems are utilized by a wide variety of bacteria to construct the flagellum, a conserved apparatus that allows for migration towards non-hostile, nutrient rich environments. Chlamydia pneumoniae is an obligate, intracellular pathogen whose genome contains at least three orthologs of flagellar proteins, namely FliI, FlhA and FliF, but the role of these proteins remains unknown.     

Discovery of novel inhibitors of <Emphasis Type="Italic">Streptococcus pneumoniae</Emphasis> based on the virtual screening with the homology-modeled structure of histidine kinase (VicK)

Background  

Due to the widespread abusage of antibiotics, antibiotic-resistance in Streptococcus pneumoniae (S. pneumoniae) has been increasing quickly in recent years, and it is obviously urgent to develop new types of antibiotics. Two-component systems (TCSs) are the major signal transduction pathways in bacteria and have emerged as potential targets for antibacterial drugs. Among the 13 pairs of TCSs proteins presenting in S. pneumoniae, VicR/K is the unique one essential for bacterium growth, and block agents to which, if can be found, may be developed as effective antibiotics against S. pneumoniae infection.     

Heterogeneity of pneumococcal phase variants in invasive human infections

Background  

Streptococcus pneumoniae can be carried asymptomatically in the nasopharynx of its human host but can also cause a wide range of infections. A role for pneumococcal phase variants in the different lifestyles of this bacterium has been suggested but no systematic survey of the colony phenotypes of isolates associated with human infections has been undertaken.     

Evaluation of an <Emphasis Type="Italic">in silico</Emphasis> predicted specific and immunogenic antigen from the OmcB protein for the serodiagnosis of <Emphasis Type="Italic">Chlamydia trachomatis</Emphasis> infections

Background  

The OmcB protein is one of the most immunogenic proteins in C. trachomatis and C. pneumoniae infections. This protein is highly conserved leading to serum cross reactivity between the various chlamydial species. Since previous studies based on recombinant proteins failed to identify a species specific immune response against the OmcB protein, this study evaluated an in silico predicted specific and immunogenic antigen from the OmcB protein for the serodiagnosis of C. trachomatis infections.     

Identification of critical residues in Gap3 of <Emphasis Type="Italic">Streptococcus parasanguinis</Emphasis> involved in Fap1 glycosylation,fimbrial formation and <Emphasis Type="Italic">in vitro</Emphasis>adhesion

Background  

Streptococcus parasanguinis is a primary colonizer of human tooth surfaces and plays an important role in dental plaque formation. Bacterial adhesion and biofilm formation are mediated by long peritrichous fimbriae that are composed of a 200 kDa serine rich glycoprotein named Fap1 (fimbriae-associated protein). Glycosylation and biogenesis of Fap1 are modulated by a gene cluster downstream of the fap1 locus. A gene encoding a glycosylation-associated protein, Gap3, was found to be important for Fap1 glycosylation, long fimbrial formation and Fap1-mediated biofilm formation.     

Optimization of culture conditions to obtain maximal growth of penicillin-resistant <Emphasis Type="Italic">Streptococcus pneumoniae</Emphasis>

Background  

Streptococcus pneumoniae, particularly penicillin-resistant strains (PRSP), constitute one of the most important causes of serious infections worldwide. It is a fastidious microorganism with exquisite nutritional and environmental requirements to grow, a characteristic that prevents the development of useful animal models to study the biology of the microorganism. This study was designed to determine optimal conditions for culture and growth of PRSP.     

Identification of a human immunodominant B-cell epitope within the immunoglobulin A1 protease of <Emphasis Type="Italic">Streptococcus pneumoniae</Emphasis>

Background  

The IgA1 protease of Streptococcus pneumoniae is a proteolytic enzyme that specifically cleaves the hinge regions of human IgA1, which dominates most mucosal surfaces and is the major IgA isotype in serum. This protease is expressed in all of the known pneumococcal strains and plays a major role in pathogen's resistance to the host immune response. The present work was focused at identifying the immunodominant regions of pneumococcal IgA1 protease recognized by the human antibody response.     

Isolation of a Bacteriophage Specific for a New Capsular Type of Klebsiella pneumoniae and Characterization of Its Polysaccharide Depolymerase

Background

Klebsiella pneumoniae is one of the major pathogens causing hospital-acquired multidrug-resistant infections. The capsular polysaccharide (CPS) is an important virulence factor of K. pneumoniae. With 78 capsular types discovered thus far, an association between capsular type and the pathogenicity of K. pneumoniae has been observed.

Methodology/Principal Findings

To investigate an initially non-typeable K. pneumoniae UTI isolate NTUH-K1790N, the cps gene region was sequenced. By NTUH-K1790N cps-PCR genotyping, serotyping and determination using a newly isolated capsular type-specific bacteriophage, we found that NTUH-K1790N and three other isolates Ca0507, Ca0421 and C1975 possessed a new capsular type, which we named KN2. Analysis of a KN2 CPS⁻ mutant confirmed the role of capsule as the target recognized by the antiserum and the phage. A newly described lytic phage specific for KN2 K. pneumoniae, named 0507-KN2-1, was isolated and characterized using transmission electron microscopy. Whole-genome sequencing of 0507-KN2-1 revealed a 159 991 bp double-stranded DNA genome with a G+C content of 46.7% and at least 154 open reading frames. Based on its morphological and genomic characteristics, 0507-KN2-1 was classified as a member of the Myoviridae phage family. Further analysis of this phage revealed a 3738-bp gene encoding a putative polysaccharide depolymerase. A recombinant form of this protein was produced and assayed to confirm its enzymatic activity and specificity to KN2 capsular polysaccharides. KN2 K. pneumoniae strains exhibited greater sensitivity to this depolymerase than these did to the cognate phage, as determined by spot analysis.

Conclusions/Significance

Here we report that a group of clinical strains possess a novel Klebsiella capsular type. We identified a KN2-specific phage and its polysaccharide depolymerase, which could be used for efficient capsular typing. The lytic phage and depolymerase also have potential as alternative therapeutic agents to antibiotics for treating K. pneumoniae infections, especially against antibiotic-resistant strains.     

Multi locus sequence typing of <Emphasis Type="Italic">Chlamydiales</Emphasis>: clonal groupings within the obligate intracellular bacteria <Emphasis Type="Italic">Chlamydia trachomatis</Emphasis>

Background  

The obligate intracellular growing bacterium Chlamydia trachomatis causes diseases like trachoma, urogenital infection and lymphogranuloma venereum with severe morbidity. Several serovars and genotypes have been identified, but these could not be linked to clinical disease or outcome. The related Chlamydophila pneumoniae, of which no subtypes are recognized, causes respiratory infections worldwide. We developed a multi locus sequence typing (MLST) scheme to understand the population genetic structure and diversity of these species and to evaluate the association between genotype and disease.     

Study of CTX-M Type of Extended Spectrum β-Lactamase among Nosocomial Isolates of <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> in South India

Data on CTX-M type extended-spectrum β-lactamase (ESBL) produced by Gram-negative bacteria by molecular methods are limited from India. This study was conducted to investigate the prevalence of CTX-M type ESBL producing Escherichia coli and Klebsiella pneumoniae from nosocomial isolates in a tertiary care hospital in southern India. A total of 179 clinical isolates of K. pneumoniae (n = 72) and E. coli (n = 107) were obtained in a period of 3 months and assessed for ESBL production phenotypically. Associated resistance to a panel of antibiotics and Minimum Inhibitory Concentration for 3rd generation cephalosporins was determined. Phenotypically ESBL positive isolates were subjected to PCR for bla _CTX-M gene using two sets of primers for the simultaneous detection of all the five major groups of CTX-M types. All the positive isolates were then subjected to a group specific PCR to detect the prevalent group. Out of 179 isolates, 156 (87.1%) were positive for ESBL phenotypically, which includes 39.2% of K. pneumoniae and 60.8% of E. coli. All of them were examined by PCR using two primers for the presence of bla _CTX-M genes. Among the 156 phenotypic positive isolates, 124 (79.4%) were positive for bla _CTX-M genes, of which 45 (36.2%) were K. pneumoniae, 79 (63.7%) were E. coli. When the 124 positive clinical isolates were further tested with CTX-M group-specific primers, all were positive for the CTX-M-1 group. Our findings document evidence of the high prevalence of multidrug resistant CTX-M group 1 type ESBL among nosocomial isolates in this region. High co-resistance to other non-β-lactam antibiotics is a major challenge for management of ESBL infections. This is alarming and calls for the judicious use of carbapenems, especially in developing countries. This has significant implications for patient management, and indicates the need for increased surveillance and for further molecular characterization of these isolates.     

Molecular mechanisms of Streptococcus pneumoniae‐targeted autophagy via pneumolysin,Golgi‐resident Rab41, and Nedd4‐1‐mediated K63‐linked ubiquitination

Streptococcus pneumoniae is the most common causative agent of community‐acquired pneumonia and can penetrate epithelial barriers to enter the bloodstream and brain. We investigated intracellular fates of S. pneumoniae and found that the pathogen is entrapped by selective autophagy in pneumolysin‐ and ubiquitin‐p62‐LC3 cargo‐dependent manners. Importantly, following induction of autophagy, Rab41 was relocated from the Golgi apparatus to S. pneumoniae‐containing autophagic vesicles (PcAV), which were only formed in the presence of Rab41‐positive intact Golgi apparatuses. Moreover, subsequent localization and regulation of K48‐ and K63‐linked polyubiquitin chains in and on PcAV were clearly distinguishable from each other. Finally, we found that E3 ligase Nedd4‐1 was recruited to PcAV and played a pivotal role in K63‐linked polyubiquitin chain (K63Ub) generation on PcAV, promotion of PcAV formation, and elimination of intracellular S. pneumoniae. These findings suggest that Nedd4‐1‐mediated K63Ub deposition on PcAV acts as a scaffold for PcAV biogenesis and efficient elimination of host cell‐invaded pneumococci.     

The <Emphasis Type="Italic">Mycoplasma pneumoniae</Emphasis> MPN229 gene encodes a protein that selectively binds single-stranded DNA and stimulates Recombinase A-mediated DNA strand exchange

Background  

Mycoplasma pneumoniae has previously been characterized as a micro-organism that is genetically highly stable. In spite of this genetic stability, homologous DNA recombination has been hypothesized to lie at the basis of antigenic variation of the major surface protein, P1, of M. pneumoniae. In order to identify the proteins that may be involved in homologous DNA recombination in M. pneumoniae, we set out to characterize the MPN229 open reading frame (ORF), which bears sequence similarity to the gene encoding the single-stranded DNA-binding (SSB) protein of other micro-organisms.