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PubMed2006

Modelling the unidentified mortality burden from thirteen infectious pathogenic microorganisms in infants.

Official statistics routinely underestimate mortality from specific microorganisms and deaths are assigned to non-specific syndromes. Here we estimate mortality attributed to specific pathogens by modelling non-specific infant deaths from laboratory reports and codes on death certificates for these pathogens, 1993-2000 in England and Wales using a generalized linear model. In total, 22.4-59.8% of non-specific deaths in infants (25-66 deaths a year) are attributable to specific pathogens. Yearly deaths from Bordetella pertussis in neonates are 6.8 [95% confidence interval (CI) 1.5-11.9]. In post-neonates 9.4 (95% CI 2.3-16.6) deaths a year are attributable to Neisseria meningitidis, 7.3 (95% CI 2.4-12.3) to Streptococcus pneumoniae, from 2.8 (95% CI 0.8-4.9) to 15.1 (95% CI 9.4-20.9) to respiratory syncytial virus (RSV) and 3 (95% CI 0.3-5.9) to parainfluenza type 2. Our results suggest there is substantial hidden mortality for a number of pathogens in infants. A considerable proportion of deaths classified to infectious syndromes are non-infectious, suggesting low specificity of death certification. Laboratory reports were the more reliable source, reinforcing the asset of strong surveillance systems.

Bacteria↗
PubMed2003

Molecular genetic variability of Australian isolates of five cereal rust pathogens.

Rust fungi cause economically important diseases of cereals, and their ability to rapidly evolve new virulent races has hindered attempts to control them by genetic resistance. PCR-based molecular tools may assist in understanding the genetic structure of pathogen populations. The high multiplex DNA fingerprinting techniques, amplified fragment length polymorphisms (AFLP), selectively amplified microsatellites (SAM) and sequence-specific amplification polymorphisms (S-SAP) were assessed for their potential in investigations of the genetic relationships among isolates of the wheat rust pathogens, Puccinia graminis f. sp. tritici (Pgt), Puccinia triticina (Pt), and P. striiformis f. sp. tritici (Pst), the oat stem rust pathogen P. graminis f. sp. avenae (Pga), and a putative new P. striiformis special form tentatively designated Barley grass yellow rust (Bgyr). Marker information content, as indicated by the number of species-specific fragments, polymorphic fragments among pathotypes, percentage of polymorphic loci, and the marker index, was highest for the SAM assay, followed by the AFLP and S-SAP assays. UPGMA analysis revealed that all marker types efficiently discriminated the five different taxa and Mantel tests revealed significant correlations between the marker types. Within pathogen groups, the marker types differed in the amount of variation detected among isolates; however, the major differences were consistent and polymorphism was generally low. This was reflected by the AMOVA analysis that significantly partitioned 90% of the genetic variation between taxa. Of the three marker types, SAMS were the most informative, and have the potential for the development of locus-specific microsatellites.

Avena↗
PubMed2005

Pythium phragmitis sp. nov., a new species close to P. arrhenomanes as a pathogen of common reed (Phragmites australis).

During a study on the occurrence and pathogenicity of oomycetes in the reed-belt (Phragmites australis) of Lake Constance (Germany), a new Pythium resembling the important cereal pathogen species complex P. arrhenomanes/P. graminicola was consistently isolated from necrotic mature reed leaves and reed rhizosphere samples. The new species proved to be significantly more aggressive towards reed leaves and seedlings in vitro than related species. It is characterised by filamentous, inflated sporangia and plerotic oospores with usually more than one antheridium. ITS and cox II sequence data indicate this new species shares a common ancestor with P. arrhenomanes, but the sequence differences are clearly consistent with a divergence of the two taxa and with P. phragmitis being a distinct species. ITS 1 and 2 of 15 isolates of the taxon consistently differed from P. arrhenomanes by 13 positions. Sequence analyses of the cox II gene confirmed the new species' phylogenetic position. This paper gives a formal description of the taxon as P. phragmitis sp. nov., providing information on morphology, ecology and pathogenicity in comparison to related species. As indicated by the close association to Phragmites australis, the high aggressiveness towards reed leaves and seedlings, and the abundance in the investigated stands, Pythium phragmitis might act as a reed pathogen of considerable importance, in particular under flooding situations.

Cyclooxygenase 2↗
PubMed2025

Discovery of Isonitrile Lipopeptide Chalkophores from Pathogenic Mycobacteria.

The virulence-associated isonitrile lipopeptide (INLP) biosynthetic gene cluster is conserved across Mycobacterium tuberculosis and many nontuberculous mycobacteria (NTM) pathogens, yet the corresponding mycobacterial metabolites have not been fully characterized, and their biological functions are still debated. Here, we report a precursor neutral loss chromatography based mass spectrometry strategy that enables the targeted discovery of INLPs from Mycobacterium fortuitum, a fast-growing NTM pathogen. By monitoring a characteristic neutral loss of 27.1 Da corresponding to hydrogen cyanide, we identified a family of INLPs directly from bacterial culture extracts. Structural elucidation of a representative compound using NMR and high-resolution MS revealed a distinctive terminal methylated carboxyl group, contrasting with previously reported INLPs bearing linear alcohol, acetal, or cyclic motifs. Bioinformatic analysis and in vitro enzymatic assays identified a methyltransferase encoded within the INLP BGC responsible for methyl ester formation. Furthermore, metal-binding assays demonstrated selective chelation of Cu(I) and Cu(II) by the isolated INLP, but no detectable interaction with Zn(II), suggesting a role in copper homeostasis. These findings represent the first full structural characterization of an INLP from pathogenic mycobacteria, expand our understanding of the enzymes involved in INLP modification, and unequivocally support the copper-binding activity of INLPs from these pathogens.

Lipopeptides↗
PubMedDate not supplied

Design of adsorptive columns for specific pathogen removal: application to staphylococcal enterotoxin B.

The removal of pathogens such as toxins, viruses, bacteria, and prions in human blood, mammalian cell culture media, fermentation broths, food items, and water streams has gained increasing importance in ensuring product safety and in combatting acts of terrorism. Adsorption processes can play an important role in removing such pathogens from solution without affecting other desirable components. Adsorptive columns that can remove specific families of pathogens would need to achieve a reduction of several logs in pathogen concentration. This requirement is much more stringent than the normal yield requirements associated with adsorptive separations aimed at product recovery and purification in a process stream. This paper considers the design of an adsorptive column aimed at reducing the concentration of infectious agents from a known volume of solution by several logs in a fixed amount of time. The general rate (GR) model of chromatography is used in the analysis, including all major transport and kinetic steps in the adsorption process. The theory, with no adjustable parameters, is shown to predict with great accuracy the effect of residence time on the log removal of staphylococcal enterotoxin B (SEB) from solution using an affinity resin with a small peptide (YYWLHH) that has been found to bind specifically to this toxin.

Adsorption↗
PubMed2005

Relative value of surrogate indicators for detecting pathogens in lakes and reservoirs.

This study investigated the relative behavior of pathogens, fecal indicator organisms, and particles of varying size during transport through a reservoir following a storm event inflow in Myponga Reservoir, South Australia. During the inflow, samples were collected from the river and at various locations within the reservoir to determine the fate and transport of microroganisms as they progressed through the water body. Microbiological analysis included the indicator organisms Escherichia coli, enterococci, Clostridium perfringens, aerobic spores, and somatic coliphages, the protozoan pathogens Cryptosporidium spp. and Giardia spp., and the potential physical surrogates of pathogen contamination including particle size and turbidity. Of the microbial indicator groups, C. perfringens spores were the most highly correlated with Cryptosporidium spp. concentrations (Spearman Rho = 0.58), closely followed by enterococci (Spearman Rho = 0.57). Cryptosporidium spp. oocysts were predominantly associated with small sized particles (range of 14.3-27.7 microm). All of the microbial indicator groups tested were associated with larger sized particle ranges (> 63.3 microm) except C. perfringens spores which were associated with particles in the size range of 45.5-63.3 microm. Although indicators may rank correlate with Cryptosporidium spp., the variation in settling rates of different microorganisms has significant implications for the use of surrogates to estimate pathogen attenuation within reservoirs. For example, concentrations of Cryptosporidium spp. oocysts were reduced by a factor of 3 on reaching the dam wall, whereas enterococci were reduced by a factor of 10.

Animals↗
PubMed1998

Pathogenicity and immunosuppressive properties of infectious bursal disease virus field isolates and commercial vaccines in India.

The pathogenicity and immunosuppressive properties of two field isolates of infectious bursal disease. virus (IBDV) and five commercial IBDV live virus vaccines marketed in India were evaluated in this study. The pathogenicity of the wild type viruses and vaccines were based on mortality, the bursa:body weight ratio and microscopic lesions in the bursa in 3-week-old chicks that received these viruses. The immunosuppressive effects of these viruses were evaluated by measuring the antibody responses to sheep red blood cells, Brucella abortus plain antigen and Newcastle disease virus (NDV) vaccine in one-day-old chicks. One field isolate (N35/93) was found to be more pathogenic and immunosuppressive than the other (N45/92) while none of the commercial mild Lukert type vaccines were found to be pathogenic. One of the vaccine strains marked as Mild Lukert type was highly immunosuppressive; one was moderate and one could be classified as mild. Both the intermediate vaccines tested were highly immunosuppressive.

Animals↗
PubMed1999

Molecular detection of pathogen DNA in ticks (Acari: Ixodidae): a review.

Ticks play an important role in human and veterinary medicine, in particular due to their ability to transmit a wide spectrum of pathogenic micro-organisms of protozoal, rickettsial, bacterial and viral origin. Pathogens in ticks can be identified by conventional methods such as indirect immunofluorescence, isolation in cell culture or by using histological staining techniques. However, the advent of the polymerase chain reaction (PCR) has resulted in tremendous improvements in the specific and sensitive detection of pathogen DNA in ticks. In this paper, literature on DNA extraction methods, PCR protocols, primers and probes, which are in use for the successful detection and identification of pathogens in ticks, are critically reviewed. Some recommendations are also given towards the end of this review.

Anaplasma↗
PubMed2001

A unique surface membrane anchored purine-salvage enzyme is conserved among a group of primitive eukaryotic human pathogens.

Previously, we isolated and characterized the gene encoding the 3'-Nucleotidase/Nuclease (Ld3'NT/NU) from the human pathogen, Leishmania donovani. This unique cell surface enzyme has been shown to be involved in the salvage of host-derived purines, which are essential for the survival of this important protozoan parasite. In this report, we assessed whether the 3'-Nucleotidase/Nuclease was conserved amongst other pathogenic Leishmania and related trypanosomatid parasites. Results of pulsed field gel electrophoresis and Southern blotting showed that a Ld3'NT/NU gene homolog was present in each of the visceral and cutaneous Leishmania species tested (i.e. isolates of L. donovani, L. infantum, L. tropica, L. major and L. mexicana, respectively). Further, results of colorimetric assays using 3'-adenosine monophosphate as substrate demonstrated that each of these organisms also expressed significant levels of 3'-nucleotidase enzyme activity. In addition, we showed that a Ld3'NT/NU gene homolog was expressed in each of these Leishmania species as a > 40 kDa 3'-nucleotidase enzyme activity. A Ld3'NT/NU gene homolog was also identified in two Crithidia species (C. fasciculata and C. luciliae) and Leptomonas seymouri but was only marginally detectable in Trypanosoma brucei, Trypanosoma cruzi and Phytomonas serpens. Cumulatively, results of this study showed that an Ld3'NT/NU homolog was conserved amongst pathogenic Leishmania sp. which suggests that this enzyme must play an critical role in purine salvage for all members of this group of human pathogens.

Animals↗
PubMed2002

Infection of Arabidopsis with a necrotrophic pathogen, Botrytis cinerea, elicits various defense responses but does not induce systemic acquired resistance (SAR).

Botrytis cinerea is a non-specific necrotrophic pathogen that attacks more than 200 plant species. In contrast to biotrophs, the necrotrophs obtain their nutrients by first killing the host cells. Many studies have shown that infection of plants by necrosis-causing pathogens induces a systemic acquired resistance (SAR), which provides protection against successive infections by a range of pathogenic organisms. We analyzed the role of SAR in B. cinerea infection of Arabidopsis. We show that although B. cinerea induced necrotic lesions and camalexin biosynthesis, it did not induce SAR-mediated protection against virulent strains of Pseudomonas syringae, or against subsequent B. cinerea infections. Induction of SAR with avirulent P. syringae or by chemical treatment with salicylic acid (SA) or benzothiadiazole also failed to inhibit B. cinerea growth, although removal of basal SA accumulation by expression of a bacterial salicylate hydroxylase (NahG) gene or by infiltration of 2-aminoindan-2-phosphonic acid, an inhibitor of phenylpropanoid pathway, increased B. cinerea disease symptoms. In addition, we show that B. cinerea induced expression of genes associated with SAR, general stress and ethylene/jasmonate-mediated defense pathways. Thus, B. cinerea does not induce SAR nor is it affected by SAR, making it a rare example of a necrogenic pathogen that does not cause SAR.

Arabidopsis↗
PubMed2002

Morphological, cultural and pathogenic characteristics of Coniothyrium zuluense isolates from different plantation regions in South Africa.

Coniothyrium canker caused by Coniothyrium zuluense, is a serious stem canker disease of Eucalyptus species in sub-tropical regions of South Africa. This disease is typified by necrotic bark lesions that coalesce to form large kino-impregnated cankers along the stems of trees. The strategy currently used to manage Coniothyrium canker in plantations is to deploy Eucalyptus species or clones that are resistant to the disease. Considerable success has already been achieved in this regard, but the long-term durability of resistance is of concern. Thus, forest managers are interested in the genetic diversity of the pathogen and its potential to overcome disease resistance in planting stock. In this study, 344 isolates of C. zuluense from different plantation regions in South Africa were compared on the basis of colony colour, conidial morphology, growth characteristics on agar and pathogenicity to a susceptible E. grandis clone. Conidia of all C. zuluense isolates measured were similar in size and shape. The fungus is slow growing in culture, which is indicative of its apparent biotrophic habit, with optimum growth observed at 30 degrees C. Isolates of C. zuluense displayed considerable variation in colony colour and pathogenicity in inoculation trials. Variation in morphology and pathogenicity amongst isolates suggests that C. zuluense has been present in South Africa for an extended period of time, or that it is changing rapidly due to strong directional selection pressures.

Animals↗
PubMed2003

Members of a unique histidine acid phosphatase family are conserved amongst a group of primitive eukaryotic human pathogens.

Recently, we identified and characterized the genes encoding several distinct members of the histidine-acid phosphatase enzyme family from Leishmania donovani, a primitive protozoan pathogen of humans. These included genes encoding the heavily phosphorylated/glycosylated, tartrate-sensitive, secretory acid phosphatases (Ld SAcP-1 and Ld SAcP-2) and the unique, tartrate-resistant, externally-oriented, surface membrane-bound acid phosphatase (Ld MAcP) of this parasite. It had been previously suggested that these enzymes may play essential roles in the growth, development and survival of this organism. In this report, to further examine this hypothesis, we assessed whether members of the L. donovani histidine-acid phosphatase enzyme family were conserved amongst other pathogenic Leishmania and related trypanosomatid parasites. Such phylogenetic conservation would clearly indicate an evolutionary selection for this family of enzymes and strongly suggest and support an important functional role for acid phosphatases to the survival of these parasites. Results of pulsed field gel electrophoresis and Southern blotting showed that homologs of both the Ld SAcPs and Ld MAcP were present in each of the visceral and cutaneous Leishmania species examined (i.e. isolates of L. donovani, L. infantum, L. tropica, L. major and L. mexicana, respectively). Further, results of enzyme assays showed that all of these organisms expressed both tartrate-sensitive and tartrate-resistant acid phosphatase activities. In addition, homologs of both the Ld SAcPs and Ld MAcP genes and their corresponding enzyme activities were also identified in two Crithidia species (C. fasciculata and C. luciliae) and in Leptomonas seymouri. In contrast, Trypanosoma brucei, Trypanosoma cruzi and Phytomonas serpens had only very-low levels of such enzyme activities. Cumulatively, results of this study showed that homologs of the Ld SAcPs and Ld MAcP are conserved amongst all pathogenic Leishmania sps. suggesting that they may play significant functional roles in the growth, development and survival of all members of this important group of human pathogens.

Acid Phosphatase↗
PubMed2003

Induction of H2O2 in transgenic rice leads to cell death and enhanced resistance to both bacterial and fungal pathogens.

Oxidative burst, mediated by hydrogen peroxide (H2O2), has been recognized as a key component of plant defense response during an incompatible interaction. To determine if elevated levels of H2O2 lead to cell death, activation of defense genes and enhanced resistance to diverse pathogens, transgenic rice plants expressing a fungal glucose oxidase gene (GOX) were generated using both constitutive and inducible expression systems. Constitutive or wound/pathogen-induced expression of GOX also allowed us to determine the effectiveness of these systems in conferring long lasting resistance to various pathogens. Both constitutive and wound/pathogen-induced expression of GOX lead to increases in the endogenous levels of H2O2, which in turn caused cell death. Elevated levels of H2O2 also activated the expression of several defense genes and these transgenic plants showed enhanced resistance to both bacterial and fungal pathogens. In comparison to inducible expression, constitutive expression of GOX resulted in 3-10-fold higher levels of the GOX transcript and the corresponding enzymatic activity. Such increased levels of GOX, which would result in elevated levels of H2O2, caused improper seed set and decreased seed viability in transgenic plants constitutively expressing GOX. Our results suggest that pathogen inducible expression of heterologous genes may be a practical and robust way of generating broad spectrum disease resistance.

Apoptosis↗
PubMed2003

Rapid induction of a protein disulfide isomerase and defense-related genes in wheat in response to the hemibiotrophic fungal pathogen Mycosphaerella graminicola.

Mycosphaerella graminicola, incitant of septoria tritici blotch, is a widespread and significant pathogen of wheat that is not closely related to other fungi being developed as genetic models for host-pathogen interactions. Several resistance genes in wheat have been identified, yet the molecular mechanisms of resistance are unknown. To identify host genes involved in the resistance response, expression profiles of the wheat line Tadinia (containing the Stb4 gene for resistance) and the susceptible line Yecora Rojo, non-inoculated or inoculated with M. graminicola, were compared by differential-display polymerase chain reaction (DD-PCR). Among the differentially expressed genes was a protein disulfide isomerase (PDI), which is well known as a molecular chaperone and component of signal-transduction pathways in animal systems but had not been implicated previously in plant defense response. Real-time quantitative reverse-transcription PCR and northern analysis revealed that PDI was induced within 3 h of inoculation with highest induction in the pathogen-treated resistant lines. These responses of PDI were similar to the early and strong resistance-related responses displayed by the pathogenesis-related (PR) proteins, PR-1, PR-2 and PR-5. In contrast, a wheat lipoxygenase was down-regulated in the resistant lines at time points corresponding with peak induction of the PR genes. Thus, part of the resistance mechanism may involve repression of a gene that could otherwise aid fungal growth. Wheat responds much more rapidly than believed previously to signals produced by M.graminicola. These early responses begin prior to penetration of the host and appear to determine the outcome of the host-pathogen interaction.

Ascomycota↗
PubMed2003

Periodontal pathogens in subgingival plaque of HIV-positive subjects with chronic periodontitis.

Many putative periodontal pathogens associated with periodontal disease in human immunodeficiency virus (HIV)-infected patients also occur in non-HIV-infected individuals. This study examined the prevalence of eight periodontal pathogens in HIV-positive and HIV-negative patients with chronic periodontitis using the 16s RNA polymerase chain reaction technique. The results showed a significant prevalence of Porphyromonas gingivalis and Treponema denticola among HIV-negative patients compared to HIV-positive patients. Sixty percent of the patients in both groups were colonized by five to six species. Odds ratio analysis revealed a statistically significant positive association between three of the 28 possible combinations in the HIV-positive group. They included Prevotella nigrescens/Campylobacter rectus, P. nigrescens/P. gingivalis and P. nigrescens/T. denticola. Although the prevalence of periodontal pathogens is similar in both the groups, the combination of certain periodontal pathogens may be responsible for chronic periodontitis seen in HIV-infected adults.

Adult↗
PubMed2003

Antigenic variations in the CD4 induced sites of the CCR5-tropic, pathogenic SHIVsf162p3 gp120 variants.

In vivo passage of non-pathogenic, CCR5-tropic simian/human immunodeficiency virus (SHIV) - SHIVsf162 resulted in a pathogenic isolate, SHIVsf162p3. In an attempt to characterize envelope (Env)-mediated properties that may contribute to its pathogenicity, major (P3 major) and minor (P3 minor) Env gp120 variants were cloned from the plasma of a SHIVsf162p3-infected animal, and expressed in the context of luciferase reporter viruses. Entry mediated by these envelopes and susceptibility to neutralization by CD4 induced-site (CD4i) antibodies (MAbs) was analyzed in comparison to parental SF162. Sequence analysis revealed that the P3 major and minor variant Envs contained 14 and 17 amino acid changes, respectively, compared with SF162. The rank order of entry mediated by the three envelopes was P3 major > SF162 > P3 minor, whereas the reverse order was observed for susceptibility to neutralization by CD4i MAbs. Since CD4i epitopes overlap the coreceptor (CoR) binding site, these findings suggest that the amino acid changes accumulated upon in vivo passage of SHIVsf162 result in Env gp120 structural rearrangements that modulate the exposure and/or conformation of the CoR binding site. This, in turn, led to increased entry and infectivity of the P3 major variant and may be responsible, in part, for the enhanced pathogenicity of SHIVsf162p3.

Amino Acid Sequence↗
PubMed2001

Effect of lipopolysaccharide from periodontal pathogens on the production of tissue plasminogen activator and plasminogen activator inhibitor 2 by human gingival fibroblasts.

Both tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 2 (PAI-2) are important proteolysis factors present in inflamed human periodontal tissues. The aim of the present study was to investigate the effect of lipopolysaccharide (LPS) on the synthesis of t-PA and PAI-2 by human gingival fibroblasts (HGF). LPS from different periodontal pathogens including Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Fusobacterium nucleatum were extracted by the hot phenol water method. The levels of t-PA and PAI-2 secreted into the cell culture media were measured by enzyme-linked immunosorbent assays (ELISA). The mRNA for t-PA and PAI-2 were measured by RT-PCR. The results showed t-PA synthesis was increased in response to all types of LPS studied and PAI-2 level was increased by LPS from A. actinomycetemcomitans and F. nucleatum, but not P. gingivalis. When comparing the effects of LPS from non-periodontal bacteria (Escherichia coli and Salmonella enteritidis) with the LPS from periodontal pathogens, we found that the ratio of t-PA to PAI-2 was greater following exposure of the cells to LPS from periodontal pathogens. The highest ratio of t-PA to PAI-2 was found in those cells exposed to LPS from P. gingivalis. These results indicate that LPS derived from periodontal pathogens may cause unbalanced regulation of plasminogen activator and plasminogen activator inhibitor by HGF and such an effect may, in part, contribute to the destruction of periodontal connective tissue through dysregulated pericellular proteolysis.

Aggregatibacter actinomycetemcomitans↗
PubMed2000

Parallel evolution of virulence in pathogenic Escherichia coli.

The mechanisms underlying the evolution and emergence of new bacterial pathogens are not well understood. To elucidate the evolution of pathogenic Escherichia coli strains, here we sequenced seven housekeeping genes to build a phylogenetic tree and trace the history of the acquisition of virulence genes. Compatibility analysis indicates that more than 70% of the informative sites agree with a single phylogeny, suggesting that recombination has not completely obscured the remnants of ancestral chromosomes. On the basis of the rate of synonymous substitution for E. coli and Salmonella enterica (4.7 x 10(-9) per site per year), the radiation of clones began about 9 million years ago and the highly virulent pathogen responsible for epidemics of food poisoning, E. coli O157:H7, separated from a common ancestor of E. coli K-12 as long as 4.5 million years ago. Phylogenetic analysis reveals that old lineages of E. coli have acquired the same virulence factors in parallel, including a pathogenicity island involved in intestinal adhesion, a plasmid-borne haemolysin, and phage-encoded Shiga toxins. Such parallel evolution indicates that natural selection has favoured an ordered acquisition of genes and the progressive build-up of molecular mechanisms that increase virulence.

DNA, Bacterial↗