Isolation of Dialister pneumosintes isolated from a bacteremia of vaginal origin

In this report, we review one case of bacteremia infection due to Dialister pneumosintes. The patient was admitted in post-partum with vaginosis and suppurative thrombosis of the ovarian veina. D. pneumosintes was isolated in pure culture from the three blood culture flasks. Identification of this bacterium was difficult and requires the amplification and partial sequencing of the 16S rRNA gene. The patients had favorable outcome after antibiotic treatment.

First molecular cloning and characterisation of caspase-9 gene in fish and its involvement in a gram negative septicaemia

Caspase-9 is an initiator caspase in the apoptotic process whose function is to activate effector caspases that are downstream in the mitochondrial pathway of apoptosis. This work reports for the first time the complete sequencing and characterisation of caspase-9 in fish. A 1924bp cDNA of sea bass caspase-9 was obtained, consisting of 1308bp open reading frame coding for 435 amino acids, 199bp of the 5'-UTR and 417bp of the 3'-UTR including a canonical polyadenilation signal 10 nucleotides upstream the polyadenilation tail. The sequence retains the pentapeptide active-site motif (QACGG) and the putative cleavage sites at Asp(121), Asp(325) and Asp(343). The sequence of sea bass caspase-9 exhibits a very close homology to the sequences of caspase-9 from other vertebrates, particularly with the putative caspases-9 of Danio rerio and Tetraodon nigroviridis (77.5 and 75.4% similarity, respectively), justifying the fact that the phylogenetic analysis groups these species together with sea bass. The sea bass caspase-9 gene exists as a single copy gene and is organised in 9 introns and 10 exons. The sea bass caspase-9 showed a basal expression in all the organs analysed, although weaker in spleen. The expression of sea bass caspase-9 in the head kidney of sea bass infected with the Photobacterium damselae ssp. piscicida (Phdp) strain PP3, showed increased expression from 0 to 12h returning to control levels at 24h. Caspase-9 activity was detected in Phdp infected sea bass head kidney from 18 to 48h post-infection, when the fish were with advanced septicaemia.

Identification by microarray of a common pattern of gene expression in intact intestine and cultured intestinal cells exposed to virulent Aeromonas hydrophila isolates

The genus Aeromonas comprises known virulent and avirulent isolates and has been implicated in waterborne disease. A common infection model of human gastroenteritis associated with A. hydrophila uses neonatal mice. The goal of this research was to evaluate whether a murine small intestinal cell line could provide comparable results to the gene expression changes in the neonatal mouse model. Changes in mRNA expression in host cell cultures and intestinal tissues were measured after exposure to virulent Aeromonas hydrophila strains. A. hydrophila caused the up-regulation of more than 200 genes in neonates and over 50 genes in cell culture. Twenty-six genes were found to be in common between the two models, of which the majority are associated with the innate immune response.

Culture-independent detection of Eikenella corrodens and Veillonella parvula in primary endodontic infections

Eikenella corrodens and Veillonella parvula are normal cultivable inhabitants of the oral cavity but their presence in endodontic infections has not been as common as it could be anticipated. This might have been because of shortcomings of culture techniques when it comes to bacterial isolation or identification. The present study intended to survey samples from primary endodontic infections for the presence of E. corrodens and V. parvula using a culture-independent 16S rRNA gene-based nested PCR protocol. Genomic DNA was isolated directly from samples taken from different forms of periradicular lesions, and the presence of E. corrodens and V. parvula was determined by nested PCR. Specificity for each primer pair was confirmed by sequence analysis of PCR products from positive clinical samples. V. parvula and E. corrodens were, respectively, detected in 33% and 14% of the root canals associated with chronic apical periodontitis. Both V. parvula and E. corrodens were found in 10% of the cases diagnosed as acute apical periodontitis. V. parvula and E. corrodens were detected in 21% and 26% of the samples from acute apical abscesses, respectively. In general, species-specific nPCR allowed the detection of V. parvula in 24% and E. corrodens in 18% of the samples taken from primary endodontic infections. Findings confirmed that V. parvula and E. corrodens can take part in the microbiota of primary endodontic infections, but in prevalence values somewhat higher when compared to most of the previous culture studies that had reported recovery of these species.

Host gene expression profiling in pathogen–host interactions

Microarray technology is a powerful high-throughput tool for the analysis of host-pathogen interactions that permits simultaneous interrogation of the transcriptional status of thousands of genes. Emerging topics from microarray-based studies employing diverse pathogens and cell types suggest an initial common host response largely characterised by features of the innate immune response. However, specific host gene expression patterns that reflect differences between bacteria of related genera, different species of a particular genus, as well as strains within a single species can also be discerned. These differences are indicative of virulence determinant functions and suggest adaptive survival strategies. These studies have led to a more comprehensive understanding of the host response and identified new avenues of research for potential control strategies against pathogens.

R-form LPS, the master key to the activation ofTLR4/MD-2-positive cells

Lipopolysaccharide (endotoxin, LPS) is a major recognition marker for the detection of gram-negative bacteria by the host and a powerful initiator of the inflammatory response to infection. Using S- and R-form LPS from wild-type and R-mutants of Salmonella and E. coli, we show that R-form LPS readily activates mouse cells expressing the signaling receptor Toll-like receptor 4/myeloid differentiation protein 2 (TLR4/MD-2), while the S-form requires further the help of the LPS-binding proteins CD14 and LBP, which limits its activating capacity. Therefore, the R-form LPS under physiological conditions recruits a larger spectrum of cells in endotoxic reactions than S-form LPS. We also show that soluble CD14 at high concentrations enables CD14-negative cells to respond to S-form LPS. The presented in vitro data are corroborated by an in vivo study measuring TNF-alpha levels in response to injection of R- and S-form LPS in mice. Since the R-form LPS constitutes ubiquitously part of the total LPS present in all wild-type bacteria its contribution to the innate immune response and pathophysiology of infection is much higher than anticipated during the last half century.

STAT-1-mediated repression of monocyte interleukin-10 gene expression in vivo

There have been substantial advances in understanding the events that regulate gene expression at the cellular and molecular level; however, there has been limited progress integrating this information to understand how biological systems function in vivo. For example, the anti-inflammatory cytokine IL-10 is thought to down-regulate the effects of the pro-inflammatory cytokine IFN-gamma on monocyte activation following LPS stimulation. However, the often-postulated reciprocal regulation of IL-10 gene expression by IFN-gamma has not been studied in vivo. Here we demonstrate that the regulation of IL-10 gene expression has at least two phases following challenge with LPS or a gram-negative organism. In C57BL/6 mice, early IL-10 induction occurs independently of STAT-1, while a delayed active repression of IL-10 gene expression is critically dependent on STAT-1, but only partially dependent upon IFN-alpha/beta and IFN-gamma. This in vivo IL-10 production comes from blood monocytes, but not tissue macrophages, and cannot be reproduced in vitro. This study provides new insights into the regulation of IL-10 following challenge with a gram-negative organism, and highlights the importance of studying these cytokine regulatory pathways in vivo.

The Toll-like receptor 4 (Asp299Gly) polymorphism is a risk factor for Gram-negative and haematogenous osteomyelitis

Osteomyelitis is a bone infection caused mostly by Staphylococcus aureus but also by Gram-negative bacteria. Toll-like receptors (TLRs), after recognizing microbial products, induce a signal in neutrophils, leading to NF-kappaB activation and transcription of pro-inflammatory genes. Polymorphisms in TLR2 (Arg753Gln) and TLR4 (Asp299Gly, Thr399Ile) genes are associated with bacterial infections, we therefore studied these polymorphisms in osteomyelitis patients. Homozygotes for the TLR4 (Asp299Gly) polymorphism were significantly more frequent among the 80 osteomyelitis patients than in the 155 healthy controls (3/80, 3.8%versus 0/155, 0%; P = 0.038). Carriers of one or two G alleles of this tlr4 polymorphism were more likely to have Gram-negative, haematogenous and/or chronic osteomyelitis than those without this mutation (P < 0.031). Patients with the TLR4 (Thr399Ile) mutant, which cosegregates with the TLR4 (Asp299Gly), were also carriers of this second polymorphism. No differences for the TLR2 (Arg753Gln) genotypes were found between patients and controls. Neutrophils of patients homozygous for the TLR4 (Asp299Gly) polymorphism showed lower LPS-induced apoptosis reduction, phosphorylation of the inhibitor of NF-kappaB, and lower IL-6 and TNF-alpha levels (P < 0.05). We report here for the first time an association between this TLR4 polymorphism and susceptibility to Gram-negative bacteria and haematogenous osteomyelitis.

Complement deficiency and disease: an update

Complement deficiencies are probably vastly under-diagnosed within clinical medicine. Judging from a Swedish study of C2 deficiency, a deficiency with an estimated prevalence of about 1/20,000 in Western countries, less than 10% of the deficiencies of the classical and alternative pathways and the late complement components are identified in Sweden. C1 inhibitor deficiency and deficiencies of MBL and MASP-2 were not included in the assessment. The introduction of new screening methods should facilitate detection of complement deficiencies in clinical practice. In our study of C2 deficiency (n=40), 57% of the patients had a history of invasive infection with encapsulated bacteria, mainly Streptococcus pneumoniae. This emphasizes the importance of the classical and/or the lectin pathway in defence against severe infection. Rheumatological disease, mainly systemic lupus erythematosus was present in 43% of the patients. In addition, a significant association was found between C2 deficiency and atherosclerosis. Complement-dependent disease mechanisms are discussed together with the potential importance of non-complement genes for disease expression in complement deficiencies. Analysis of larger patient groups is required in order to establish guidelines for investigation and treatment of patients with complement deficiency.

Identification of a transcript encoding a soluble form of toll-like receptor 5 (TLR5) in Atlantic salmon during Aeromonas salmonicida infection

Toll-like receptors (TLRs) are involved in the innate immune response against microbial pathogens in vertebrates and insects. The extracellular region of a TLR recognizes pathogen-associated molecules, while the intracellular region initiates the signaling pathway leading to immune response. Membrane-bound TLRs have been found in most vertebrates, but few soluble forms have been reported. A novel transcript corresponding to a portion of a soluble TLR was identified in liver of infected Atlantic salmon. The complete coding sequence of this TLR was obtained and BLASTN analysis showed the highest sequence identity to a recently described full-length cDNA sequence of a soluble TLR5 from rainbow trout (GenBank Accession No.: ). The deduced protein is 40% identical to the mammalian counterpart of the leucine-rich repeat (LRR)/LRR-like motifs of TLR5. Based on the structure of human TLRs, it contains 21 LRRs with conserved LxxLxLxxNx*xx*xxxxFxxL pattern. Since TLR5 is essential for the recognition of bacterial flagellins, we hypothesize that flagellin and perhaps some other pathogen-derived factors from Aeromonas salmonicida bind to this soluble TLR through an unknown binding domain within the LRR.

Fluorescent amplified fragment length polymorphism (FAFLP) based molecular epidemiology of hospital infections in a tertiary care setting in Hyderabad, India

Bacterial isolates from respiratory and urinary tract infections in an Indian hospital setting were genotyped using FAFLP analysis. The 77 different isolates analyzed belonged to five genera namely Escherichia, Staphylococcus, Pseudomonas, Enterobacter and Pantoea. Before carrying out FAFLP analysis all the isolates were subjected to16S-23S ribosomal RNA-based species identification. Cluster analysis of FAFLP profiles of 77 isolates generated five groups corresponding to five bacterial genera that are used in the study. Further analyses of the dendrograms revealed efficient species and strain differentiation. Cluster analysis identified genetically distant clones among the clinical isolates of Staphylococcus aureus, two distinct genetic lineages among the Escherichia coli strains and a single cluster of closely related Pseudomonas aeruginosa isolates. Ribosomal spacer region amplification identified different species accurately but intraspecies discrimination could not be accomplished completely. Comparison of FAFLP profiles of our isolates, with a pilot database of validated strains, was very useful in identification and worked better in conjunction with dendrogram analysis.

Defining the need for new antimicrobials: clinical and economic implications of resistance in the hospitalised patient

Resistance among pathogens causing the most common infections encountered in hospitalised patients is increasing. Due to this resistance, the clinical efficacy of current antimicrobial agents is decreasing against many pathogens, including Streptococcus pneumoniae, methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, Pseudomonas aeruginosa, extended-spectrum beta-lactamases, and AmpC beta-lactamase-producing organisms. Studies assessing the impact of these resistance mechanisms on clinical outcomes have been performed; however, studies determining the economic impact of resistance have been limited. Strategies to retain the clinical efficacy of currently available agents include the initiation of antimicrobials with efficacy against the suspected pathogen(s) based on data obtained from local antibiograms, the use of combination therapy, and pharmacodynamic optimisation. Once a broad-spectrum regimen has been initiated, de-escalation to narrow, targeted antimicrobial therapy based on susceptibility data is warranted. Despite these efforts, new antimicrobials with novel mechanisms of action are eagerly anticipated to extend the current armamentarium against the growing population of multi-drug-resistant pathogens.

[Study on the molecular epidemiology of Stenotrophomonas maltophilia infection in patients on mechanical ventilation]

OBJECTIVE

To investigate a potential outbreak of Stenotrophomonas maltophilia (pma) infection occurred in patients on mechanical ventilation in a respiratory ICU (RICU) and to track the infective origins by antibiotype and pulsed-field gel electrophoresis (PFGE) typing methods.

METHODS

(1) Thirteen pma strains were isolated from 9 patients on mechanical ventilation (9 strains), hand swabs of medical staffs in RICU (2 strains) and fiberscope used for intubations and aspiration (2 strains) from December, 2002 to February, 2003. (2) Sixteen strains gathered from different wards during the period of 1997 - 2000 were collected and used as control. (3) Antibiotic susceptibility data of all strains were collected. (4) Homology of the strains was analyzed by the methods of antibiotype and PFGE genotype.

RESULTS

Of the 9 pma isolated from patients on mechanical ventilation, eight had identical PFGE genotype. The isolates from two RICU staffs and two fiberscope displayed the same genotype with the eight patients above. Seven of the 9 isolates shared an identical antibiotype. The consistent rate of antibiotype with PFGE genotype was 85% (11/13). There were 11 PFGE genotypes and 9 antibiotypes in 16 strains of the control group, which indicated that they came from different clones.

CONCLUSIONS

Eight pma strains of patients in RICU came from the same clone. This result proved that clone transmission occurred in patients on mechanical ventilation. Contaminated fiberscope and hands of staffs may be the infective origin and the route of transmission.

Differential Gene Expression in Gram-negative and Gram-positive Sepsis

Sepsis is the most common cause of death in patients in the intensive care unit. Genome-wide gene expression analysis can provide insights into the molecular alterations of sepsis. Total mRNA was extracted from the livers of 6 uninfected control mice and 60 septic mice after infusion of either live Escherichia coli or Staphylococcus aureus. Using a murine complementary DNA microarray system, changes in gene expression were monitored at six time points (uninfected, 2, 8, 24, 48, and 72 hours). Overall, 4.8% of 6,144 assessed genes were differentially regulated with a greater than twofold change across all time points. Most of the genes with altered expression were commonly present in gram-negative and gram-positive sepsis, but the expression levels of 17 genes were different between both types of sepsis at particular time points after infection. The microarray results support the hypothesis that both gram-positive and gram-negative sepsis share a final common pathway involved in the pathogenesis of sepsis, but certain genes are differentially expressed under distinct regulation. These results may provide insights into the pathogenesis of sepsis and may also help identify some altered genes that can serve as new targets for diagnostic tools and therapeutic strategies.

Molecular characterization of the acute inflammatory response to infections with gram-negative versus gram-positive bacteria

Sepsis caused by gram-negative bacteria and that caused by gram-positive bacteria often manifest similar clinical features. We investigated plasma proinflammatory cytokine profiles in patients with sepsis due to gram-positive and gram-negative bacteria and studied the cytokine production and differential gene regulation of leukocytes stimulated ex vivo with Escherichia coli lipopolysaccharide or heat-killed Staphylococcus aureus. Concentrations of tumor necrosis factor alpha, interleukin 1 receptor antagonist (IL-1Ra), IL-8, IL-10, IL-18 binding protein, procalcitonin, and protein C in plasma did not differ between patients with sepsis due to gram-negative and gram-positive bacteria. However, plasma IL-1beta, IL-6, and IL-18 concentrations were significantly higher in patients with sepsis due to gram-positive bacteria. Ex vivo stimulation of whole blood with heat-killed S. aureus markedly increased IL-1beta and IL-18 levels more than E. coli lipopolysaccharide stimulation. Microarray analysis revealed at least 359 cross-validated probe sets (genes) significant at the P < 0.001 level whose expression discriminated among gram-negative-organism-stimulated, gram-positive-organism-stimulated, and unstimulated whole-blood leukocytes. The host inflammatory responses to gram-negative and gram-positive stimuli share some common response elements but also exhibit distinct patterns of cytokine appearance and leukocyte gene expression.

Vaccine Development for Potential Bioterrorism Agents

Vaccines are considered to be one of the most effective ways of combating disease caused by bioterrorism agents. Such vaccines must be able to provide protection against pathogens which might enter the body by a number of routes, including the respiratory tract. They should also be able to induce protective immunity rapidly and would ideally be given non-invasively. There are few vaccines which currently meet these requirements. In part, this reflects the low level of research on many bioterrorism agents over the past few decades. Little is known about basic mechanisms of pathogenicity of many of these agents. However, by their very nature these agents cause serious disease, and must be handled in high containment laboratories. This requirement also limits the speed and ease with which research on these pathogens can now take place. Against this background, research on vaccines against potential bioterrorism agents is likely to proceed along two lines. Firstly because the genome sequences of most of the principal bioterrorism agents have either been completed or are close to completion, there is likely to be reliance on the exploitation of this information to devise improved vaccines. A number of groups are working on methodologies to identify vaccine antigens directly from genome sequences. Secondly, there will be a need to formulate such vaccines appropriately for the rapid induction of protective immunity after non-invasive delivery. The prospects for the development of a new generation of bioterrorism vaccines which exploit these technologies are reviewed in this manuscript.

MHC polymorphism and disease resistance in Atlantic salmon (Salmo salar); facing pathogens with single expressed major histocompatibility class I and class II loci

Few studies have yet addressed the functional aspects of MHC molecules in fish. To lay the foundation for this, we evaluated the association between disease resistance and MHC class I and class II polymorphism in Atlantic salmon. Standardized disease challenge trials were performed on a semi-wild Atlantic salmon population with subsequent MHC typing and statistical analysis. The pathogens employed were infectious salmon anaemia virus (ISAV) causing infectious salmon anaemia and the Aeromonas salmonicida bacteria causing furunculosis. The material consisted of 1,182 Atlantic salmon from 33 families challenged with A. salmonicida and 1,031 Atlantic salmon from 25 families challenged with ISAV. We found highly significant associations between resistance towards infectious diseases caused by both pathogens and MH class I and class II polymorphism in Atlantic salmon. The observed associations were detected due to independently segregating MH class I and class II single loci, and inclusion of a large number of fish allowing an extensive statistical analysis.

Monoallelic expression of the murine gene encoding Toll-like receptor 4

Defects in the gene encoding Toll-like receptor 4 (Tlr4) result in impaired responses to lipopolysaccharide (LPS), rendering mice sensitive to infections by Gram-negative bacteria. C3H/HeJ mice have a codominant allele with a mutation in Tlr4, which results in an intermediate response to LPS in F1 mice from crosses of responder and C3H/HeJ mice. Here we show that this intermediate response to LPS is due to monoallelic expression of Tlr4. Allele usage is maintained during clonal expansion, a situation that resembles allelic exclusion. In contrast, Tlr4 is deleted on the recessive C57BL/10ScCr allele and all cells from F1 mice from crosses of responder and C57BL/10ScCr mice express TLR4 protein. Thus, Tlr4 is an autosomal gene whose expression is regulated similarly to that of genes on the X chromosome.

Human toll-like receptor 4 mutations but not CD14 polymorphisms are associated with an increased risk of gram-negative infections

Human toll-like receptor 4 (hTLR4) and CD14 are known to be components of the lipopolysaccharide receptor complex. Our study investigated the association between TLR4 mutations (Asp299Gly and Thr399Ile) and CD14 polymorphism(s) with outcome in an intensive care unit (ICU) population at risk for sepsis. By use of a polymerase chain reaction-based restriction fragment-length polymorphism analysis technique, the hTLR4 gene was altered in 14 (18%) of 77 ICU patients (all positive for systemic inflammatory response syndrome) and in 5 (13%) of 39 volunteers. There was a significantly higher incidence of gram-negative infection among patients with the mutations (11 [79%] of 14), compared with that in the wild-type population (11 [17%] of 63; P=.004). No association between CD14 polymorphism(s) and the incidence of infection or outcome was observed. These findings indicate that hTLR4 mutations are associated with an increased incidence of gram-negative infections in critically ill patients in a surgical setting.

Development of broad-range polymerase chain reaction (PCR) bacterial identification in diagnosis of infective endocarditis

BACKGROUND AND AIMS OF THE STUDY

The study aim was to identify the value of broad-range bacterial PCR in infective endocarditis (IE) of bacterial etiology, and to determine its specificity and sensitivity.

METHODS

Thirty blood samples were taken for analysis from patients with IE (diagnosed according to Duke criteria) and acquired valvular heart disease. Two control groups of patients with (n = 10) or without (n = 15) urinary tract infection were defined. DNA was isolated, and three different primer pairs for the region of the gene coding for 16S rRNA were tested, to determine the most specific pair. Amplification products were analyzed with gel electrophoresis, stained with ethidium bromide, and located under UV light.

RESULTS

Positive blood cultures were found in 25 patients with IE. A typical echocardiography picture with bacterial vegetations was found in all patients with sterile blood cultures, and in 20 patients with positive blood cultures. The highest specificity was found for forward/reverse (F/R) primers, as the relevant amplified PCR product was present in all blood samples with IE, and in four of 10 patients with urinary tract infection.

CONCLUSION

Broad-range PCR in bacterial endocarditis is a rapid, sensitive and inexpensive technique for the detection of bacteria, but is far more prone to contamination than species-specific PCR. However, under controlled conditions, broad-range PCR may be valuable for the identification of non-specific infection, permitting a more rapid clinical diagnosis of endocarditis.

An Aeromonas salmonicida type IV pilin is required for virulence in rainbow trout Oncorhynchus mykiss

Aeromonas salmonicida expresses a large number of proven and suspected virulence factors including bacterial surface proteins, extracellular degradative enzymes, and toxins. We report the isolation and characterization of a 4-gene cluster, tapABCD, from virulent A. salmonicida A450 that encodes proteins homologous to components required for type IV pilus biogenesis. One gene, tapA, encodes a protein with high homology to type IV pilus subunit proteins from many gram-negative bacterial pathogens, including Aeromonas hydrophila, Pseudomonas aeruginosa, and Vibrio vulnificus. A survey of A. salmonicida isolates from a variety of sources shows that the tapA gene is as ubiquitous in this species as it is in other members of the Aeromonads. Immunoblotting experiments demonstrate that it is expressed in vitro and is antigenically conserved among the A. salmonicida strains tested. A mutant A. salmonicida strain defective in expression of TapA was constructed by allelic exchange and found to be slightly less pathogenic for juvenile Oncorhynchus mykiss (rainbow trout) than wild type when delivered by intraperitoneal injection. In addition, fish initially challenged with a high dose of wild type were slightly more resistant to rechallenge with wild type than those initially challenged with the tapA mutant strain, suggesting that presence of TapA contributes to immunity. Two of the other three genes identified, tapB and tapC, encode proteins with homology to factors known to be required for type IV pilus assembly in P. aeruginosa, but in an as yet unidentified manner. TapB is a member of the ABC-transporter family of proteins that contain characteristic nucleotide-binding regions, and which may provide energy for type IV pilus assembly through the hydrolysis of ATP. TapC homologs are integral cytoplasmic membrane proteins that may play a role in pilus anchoring or initiation of assembly. The fourth gene, tapD, encodes a product that shares homology with a family of proteins with a known biochemical function, namely, the type IV prepilin leader peptidases. These bifunctional enzymes proteolytically cleave the leader peptide from the pilin precursor (prepilin) and then N-methylate the newly exposed N-terminal amino acid prior to assembly of the subunits into the pilus structure. We demonstrate that A. salmonicida TapD is able to restore type IV pilus assembly and type II secretion in a P. aeruginosa strain carrying a mutation in its type IV peptidase gene, suggesting that it plays the same role in A. salmonicida.