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Gram-positive Organisms (gram-positive + organism)
Selected AbstractsAntisense RNA regulation of the par post-segregational killing system: structural analysis and mechanism of binding of the antisense RNA, RNAII and its target, RNAIMOLECULAR MICROBIOLOGY, Issue 2 2001Tony J. Greenfield The par stability determinant of the Enterococcus faecalis plasmid pAD1 is the first antisense RNA regulated post-segregational killing system (PSK) identified in a Gram-positive organism. Par encodes two small, convergently transcribed RNAs, designated RNAI and RNAII, which are the toxin and antitoxin of the par PSK system respectively. RNAI encodes an open reading frame for a 33 amino acid toxin called Fst. Expression of fst is regulated post-transcriptionally by RNAII. RNAII interacts with RNAI by a unique antisense RNA mechanism involving binding at the 5, and 3, ends of both RNAs. Par RNA interaction requires a complementary transcriptional terminator stem-loop and a set of direct repeat sequences, DRa and DRb, located at the 5, end of both RNAs. The secondary structures of RNAI, RNAII and the RNAI,RNAII complex were analysed by partial digestion with Pb(II) and ribonucleases. Probing data for RNAI and RNAII are consistent with previously reported computer generated models, and also confirm that complementary direct repeat and terminator sequences are involved in the formation of the RNAI,RNAII complex. Mutant par RNAs were used to show that the binding reaction occurs in at least two steps. The first step is the formation of an initial kissing interaction between the transcriptional terminator stem-loops of both RNAs. The subsequent step(s) involves an initial pairing of the complementary direct repeat sequences followed by complete hybridization of the 5, nucleotides to stabilize the RNAI,RNAII complex. [source] Microbial and clinical determinants of time-to-positivity in patients with bacteraemiaCLINICAL MICROBIOLOGY AND INFECTION, Issue 7 2007J. A. Martínez Abstract Time-to-positivity is useful in the diagnosis of catheter-related bacteraemia and as a predictor of an endovascular source in patients with Staphylococcus aureus bacteraemia. However, this parameter has been evaluated for only a limited number of microorganisms. In the present study, time-to-positivity was recorded for 1872 episodes of significant monomicrobial bacteraemia diagnosed at a teaching hospital during a 2-year period, and the associated microbial and clinical variables were investigated. According to multivariate analysis, Streptococcus pneumoniae, ,-haemolytic streptococci, Escherichia coli, Klebsiella, Enterobacter, Citrobacter and Aeromonas were characterised by fast growth, with an endovascular source, shock, liver cirrhosis and neutropenia also predicting a short time-to-positivity. For patients not receiving appropriate antibiotics, detection of Gram-positive cocci in clusters within 14 h was predictive of Staph. aureus; a time-to-positivity of >21 h ruled out the possibility that a Gram-positive organism in chains was a ,-haemolytic streptococcus or Strep. pneumoniae, and a time-to-positivity of ,12 h meant that it was very unlikely that a Gram-negative bacillus was a non-fermenter. A time-to-positivity of ,8 h was predictive of a non-urinary tract source in patients with E. coli bacteraemia, and detection of growth within 13 h predicted an endovascular source in those with Staph. aureus bacteraemia. In conclusion, time-to-positivity depended on the microorganism, original source and clinical variables involved. Although this measurement may provide some early clues concerning the microorganisms involved and the source of bacteraemia, its clinical impact remains to be defined. [source] Phylogenetic reconstruction of Gram-positive organisms based on comparative sequence analysis of molecular chaperones from the ruminal microorganism Ruminococcus flavefaciens FD-1FEMS MICROBIOLOGY LETTERS, Issue 1 2003Dionysios A. Antonopoulos Abstract Primers designed on the basis of nucleotide sequences conserved in DnaK and GroEL from Gram-positive organisms were used to PCR amplify internal regions of the cognate genes from the anaerobic ruminal cellulolytic bacterium Ruminococcus flavefaciens FD-1. Genome walking was then utilized to elucidate the remainder of the sequences in addition to upstream and downstream regions. The full sequence of the gene encoding the GroES protein (groES) was found directly upstream from groEL. The deduced amino acid sequence of the groEL gene showed the highest homology with the amino acid sequence of the Clostridium thermocellum GroEL protein (72% amino acid identity). Similarly, translation of the groES nucleotide sequence showed highest homology to the C. thermocellum GroES protein (61% amino acid identity). Analysis of the upstream region of this chaperonin operon revealed a CIRCE regulatory element 45 bp upstream from the putative start of the groES ORF. The deduced amino acid sequence of the putative dnaK gene showed the highest homology with the amino acid sequence of the Clostridium acetobutylicum DnaK protein (68% amino acid identity). Phylogenetic analyses based on the translated sequences reiterate this relationship between R. flavefaciens and the Clostridia. However, when the nucleotide sequences of Gram-positive organisms are analyzed, a different topology occurs of the relationship between high- and low-G+C Gram-positive organisms to the 16S rRNA interpretation. [source] Premature Salmonella Typhimurium growth inhibition in competition with other Gram-negative organisms is redox potential regulated via RpoS inductionJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2004E. Komitopoulou Abstract Aims:, To identify the role of oxidation,reduction (redox) potential in the premature growth inhibition and RpoS induction in Salmonella serotype Typhimurium in competitive growth experiments. Methods and Results:, Oxidation,reduction potential was measured throughout the growth of a minority population of Salm. Typhimurium in mixed cultures with other Gram-negative and Gram-positive organisms. A lux -based reporter was also used to evaluate RpoS activity in Salm. Typhimurium in competitor studies. In a mixed culture, the multiplication of a minority population of Salm. Typhimurium was inhibited when competing Gram-negative organisms entered the stationary phase. This was not seen when the competing flora was Gram-positive. The change in redox potential during growth in mixed cultures was closely linked to the inhibition of Salm. Typhimurium growth by Gram-negative competitors. An artificially induced drop in redox potential earlier during growth in mixed cultures with Gram-negative organisms reduced the time to RpoS induction in Salm. Typhimurium and thus inhibited its multiplication prematurely. In contrast, RpoS induction and growth inhibition were prevented under high redox potential conditions. Conclusions:, This work shows that the inhibitory activity of competitive organisms can be mediated through their effect on redox potential-regulated RpoS induction. Significance and Impact of the Study:, Redox potential is shown to be an important determinant of Salm. Typhimurium growth, an observation with practical implications both for its control and detection. [source] Three gene products govern (p)ppGpp production by Streptococcus mutansMOLECULAR MICROBIOLOGY, Issue 6 2007José A. Lemos Summary The current dogma implicating RelA as the sole enzyme controlling (p)ppGpp production and degradation in Gram-positive bacteria does not apply to Streptococcus mutans. We have now identified and characterized two genes, designated as relP and relQ, encoding novel enzymes that are directly involved in (p)ppGpp synthesis. Additionally, relP is co-transcribed with a two-component signal transduction system (TCS). Analysis of the (p)ppGpp synthetic capacity of various mutants and the behaviour of strains lacking combinations of the synthetase enzymes have revealed a complex regulon and fundamental differences in the way S. mutans manages alarmone production compared with bacterial paradigms. The functionality of the RelP and RelQ enzymes was further confirmed by demonstrating that expression of relP and relQ restored growth of a (p)ppGpp0Escherichia coli strain in minimal medium, SMG and on medium containing 3-amino-1,2,4-triazole, and by demonstrating (p)ppGpp production in various complemented mutant strains of E. coli and S. mutans. Notably, RelQ, and RelP and the associated TCS, are harboured in some, but not all, pathogenic streptococci and related Gram-positive organisms, opening a new avenue to explore the variety of strategies employed by human and animal pathogens to survive in adverse conditions that are peculiar to environments in their hosts. [source] Bacillus subtilis antibiotics: structures, syntheses and specific functionsMOLECULAR MICROBIOLOGY, Issue 4 2005Torsten Stein Summary The endospore-forming rhizobacterium Bacillus subtilis, the model system for Gram-positive organisms, is able to produce more than two dozen antibiotics with an amazing variety of structures. The produced anti-microbial active compounds include predominantly peptides that are either ribosomally synthesized and post-translationally modified (lantibiotics and lantibiotic-like peptides) or non-ribosomally generated, as well as a couple of non-peptidic compounds such as polyketides, an aminosugar, and a phospholipid. Here I summarize the structures of all known B. subtilis antibiotics, their biochemistry and genetic analysis of their biosyntheses. An updated summary of well-studied antibiotic regulation pathways is given. Furthermore, current findings are resumed that show roles for distinct B. subtilis antibiotics beyond the ,pure' anti-microbial action: Non-ribosomally produced lipopeptides are involved in biofilm and swarming development, lantibiotics function as pheromones in quorum-sensing, and a ,killing factor' effectuates programmed cell death in sister cells. A discussion of how these antibiotics may contribute to the survival of B. subtilis in its natural environment is given. [source] Early bacteremia in pediatric hematopoietic stem cell transplant patients on oral antibiotic prophylaxisPEDIATRIC BLOOD & CANCER, Issue 2 2005Leslie S. Kersun MD, MSCE Abstract Background Bacteremia occurs during hematopoietic stem cell transplant (HSCT) in 20%,25% of patients and the use of gut decontamination (GD) to decrease this risk is controversial. Our purpose was to determine the incidence of bacteremia and antimicrobial resistance post-HSCT in pediatric patients receiving GD, and to identify risk factors associated with infection. Procedures This was a retrospective cohort study of 182 pediatric patients undergoing first HSCT for malignant disease at The Children's Hospital of Philadelphia from January, 1999 to December, 2002. We examined the impact of age, sex, race, diagnosis, disease status, conditioning regimen, recent bacteremia, stem cell source, donor, graft versus host disease prophylaxis agents, and mucositis severity using Cox proportional hazard models. GD consisted of amoxicillin (azithromycin, if penicillin allergic) and oral gentamicin. Outcome was first episode of bacteremia prior to absolute neutrophil count (ANC) 500/mm3. Antibiotic susceptibilities were performed on all isolates. Results Seventy-four patients (41%) developed bacteremia. The majority were Gram-positive cocci, with Staphylococcal (50%) and Streptococcal species (28%) the most common. Gram-negative organisms were identified in 22% with Pseudomonas (5.7%) and Klebsiella species (3.4%) the most common. Of the Streptococcal infections, 72% were resistant to ampicillin; only 25% of the Gram-negative bacteria were resistant to gentamicin. Race was the only factor associated with early bacteremia (hazard ratio 2.3 for non-Caucasian, non-African-American patients, CI 1.3,4.3, P,=,0.007) Conclusions Early bacteremia is common after HSCT, despite the use of GD. Resistant Gram-positive organisms predominate, consistent with recent trends in immunocompromised patients. Although used in practice, there is no clear evidence for the efficacy of GD and this study provides the basis upon which to develop a randomized clinical trial evaluating the current GD regimen with placebo. © 2004 Wiley-Liss, Inc. [source] Emesis predicts bacteremia in immunocompromised children with central venous catheters and fever,CANCER, Issue 14 2009Matthew W. Richardson MD Abstract BACKGROUND: The objective of this study was to determine whether vomiting at presentation of a febrile illness in immunocompromised children with central venous catheters (CVCs) predicts bacteremia. METHODS: A chart review was conducted of children who were admitted to the hospital with a diagnosis of cancer or aplastic anemia, fever, and a CVC. Data were collected on the presence or absence of vomiting, catheter type, presence or absence of severe neutropenia, C-reactive protein (Crp) value, and culture results. RESULTS: There were 143 admissions for fever among 48 children. Among 35 admissions with emesis, 19 included bacteremia; whereas, among 107 admissions without emesis, 19 included bacteremia (P < .001). There was a 5-fold greater risk of bacteremia in children with children without vomiting (odds ratio, 5.50; 95% confidence interval, 2.20-13.67). Gram-negative organisms were more likely to be associated with vomiting than Gram-positive organisms (P = .008). Children with severe neutropenia did not have a significantly higher rate of bacteremia than children who had neutrophil counts >500 cells/mm3. Other factors that were associated with higher rates of bacteremia were underlying diagnosis and catheter type. CONCLUSIONS: Immunocompromised children with a CVC and a fever who presented with vomiting were more likely to have bacteremia than similar children who presented without vomiting. Gram-negative organisms were more likely to be associated with emesis than Gram-positive organisms. The absence of severe neutropenia was not associated with a decreased likelihood of bacteremia. These findings may be useful in identifying children who are at high risk for bacteremia and in determining initial, empiric therapy. Cancer 2009. © 2009 American Cancer Society. [source] Cyanoacrylate glue for corneal perforations: a description of a surgical technique and a review of the literatureCLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 6 2000Brendan Jt Vote MBBS ABSTRACT The effective early application of a cyanoacrylate glue corneal patch can aid in the management of small corneal perforations, corneal melts and wound leaks. Their use gives improved visual outcomes with reduced enucleation rates (6%vs 19%). It may also avoid the need for tectonic penetrating keratoplasty. Cyanoacrylate glue prevents re-epithelialization into the zone of damaged and naked stroma and prevents the development of the critical setting for collagenase production that leads to stromal melting. Cyanoacrylates also have significant bacteriostatic activity against Gram-positive organisms. We describe a simple and easily reproducible method of cyanoacrylate corneal patch application, with neglible risk of inadvertent glue complications. It has the further advantage of a smooth corneal surface rather than an irregular surface as often occurs with direct application methods. With corneal application, the major concern is toxicity of cyanoacrylates through direct contact with the corneal endothelium and lens. Fibrin glues may be less toxic; however, they are not as readily available. The longer alkyl chains of currently available cyanoacrylate glues (e.g. Histoacryl) slows degradation significantly, limiting accumulation of histotoxic by-products to amounts that can be effectively eliminated by tissues. Vigilance in monitoring for infection/corneal infiltrate is necessary at all times, especially when the glue has been present for more than 6 weeks. Corneal patching with cyanoacrylate glue is a temporizing procedure only, buying time to allow healing secondary to medical treatment of the underlying condition, or allowing surgery to be elective and under more optimal conditions once inflammation has been reduced and the integrity of the globe restored. [source] | |||||||||||||