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At least 1,621 records · Page 90Linked to original sources
PubMed2006

Pathogens in maternal blood and fetal cord blood using Q-PCR assay.

OBJECTIVE: To evaluate the rates of infection of asymptomatic fetuses and mothers through fetal cord blood and maternal blood examination results. MATERIALS AND METHODS: Quantitative PCR (Q-PCR) was used to detect pathogens in maternal peripheral blood and fetal cord blood after delivery of term pregnancy at Buddhist Tzu Chi Medical Center, Hualien, between July 2002 and June 2003. RESULTS: We used Q-PCR to detect pathogens in 29 samples of maternal blood. The maternal hepatitis B virus (HBV) DNA detection rate was 51.72% (15/29); for human cytomegalovirus DNA, the detection rate was 10.34% (3/29) and for Chlamydia trachomatis DNA the detection rate was 3.45% (1/29). No Neisseria gonorrhoeae DNA was detected. Whereas, in 29 samples of paired fetal cord blood, the detection rates were 27.59% (8/29), 10.34% (3/29), and 3.45% (1/29) for HBV DNA, C. trachomatis DNA, and N. gonorrhoeae DNA, respectively. No human cytomegalovirus DNA was detected in fetal cord blood. CONCLUSION: Our results revealed an unexpectedly high incidence of pathogens in fetal cord blood. Screening for the above pathogens in donor cord blood in cord blood banks using Q-PCR is strongly urged to decrease morbidity and mortality rates in fetal cord blood stem cell transplant recipients.

Chlamydia trachomatis↗
PubMed2002

In the absence of IL-12, CD4(+) T cell responses to intracellular pathogens fail to default to a Th2 pattern and are host protective in an IL-10(-/-) setting.

IL-12-deficient mice exposed to nonlethal infections with intracellular pathogens or repeatedly immunized with a pathogen extract developed lowered but nevertheless substantial numbers of IFN-gamma(+) CD4(+) T cells compared to those observed in wild-type animals. Moreover, the CD4(+) responses in these knockout animals failed to default to a Th2 pattern. The protective efficacy of the Th1 cells developing in an IL-12-deficient setting was found to be limited by IL-10 since mice doubly deficient in IL-10 and IL-12 survived, while animals deficient in IL-12 alone succumbed to pathogen challenge. In contrast to IL-12 knockout mice, MyD88-deficient animals exposed to a Th1 microbial stimulus developed a pure Th2 response, arguing that this signaling element plays a more critical function than IL-12 in determining pathogen-induced CD4 polarization.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Biosynthesis of fungal melanins and their importance for human pathogenic fungi.

For more than 40 years fungi have been known to produce pigments known as melanins. Predominantly these have been dihydroxyphenylalanine (DOPA)-melanin and dihydroxynaphthalene (DHN)-melanin. The biochemical and genetical analysis of the biosynthesis pathways have led to the identification of the genes and corresponding enzymes of the pathways. Only recently have both these types of melanin been linked to virulence in some human pathogenic and phytopathogenic fungi. The absence of melanin in human pathogenic and phytopathogenic fungi often leads to a decrease in virulence. In phytopathogenic fungi such as Magnaporthe grisea and Colletotrichum lagenarium, besides other possible functions in pathogenicity, DHN-melanin plays an essential role in generating turgor for plant appressoria to penetrate plant leaves. While the function of melanin in human pathogenic fungi such as Cryptococcus neoformans, Wangiella dermatitidis, Sporothrix schenckii, and Aspergillus fumigatus is less well defined, its role in protecting fungal cells has clearly been shown. Specifically, the ability of both DOPA- and DHN-melanins to quench free radicals is thought to be an important factor in virulence. In addition, in several fungi the production of fungal virulence factors, such as melanin, has been linked to a cAMP-dependent signaling pathway. Many of the components involved in the signaling pathway have been identified.

Cryptococcus neoformans↗
PubMed2003

Analysis of loss of pathogenicity mutants reveals that repeat-induced point mutations can occur in the Dothideomycete Leptosphaeria maculans.

Restriction enzyme mediated insertional mutagenesis using a plasmid, pUCATPH, that confers hygromycin resistance, generated loss-of-pathogenicity mutants of Leptosphaeria maculans, the fungus that causes blackleg disease of Brassica napus. Of 516 L. maculans transformants analysed, 12 were pathogenicity mutants. When eight of these mutants were crossed to an isolate that attacks B. napus, cosegregation of pUCATPH sequences and loss of pathogenicity was not observed, suggesting that these mutations were not linked to plasmid sequences. In seven of eight crosses analysed, progeny with the hygromycin resistance gene were hygromycin-sensitive. Sequence analysis of an amplified fragment of pUCATPH in six clones derived from one 'silenced' progeny showed mutation of GC to AT on one DNA strand, reminiscent of repeat-induced point mutation (RIP) in Neurospora crassa. One loss-of-pathogenicity mutant had pUCATPH inserted in the promoter of a gene with an open reading frame of 529 amino acids that had no database match. Reintroduction of a wild-type copy of the gene to this mutant restored the ability to form lesions on cotyledons of B. napus.

Amino Acid Sequence↗
PubMed2000

Use of a chinese herbal medicine for treatment of hiv-associated pathogen-negative diarrhea.

Background: Diarrhea is a frequent problem among persons with advanced HIV disease. In the absence of treatable pathogens, symptomatic relief is all that is available for current therapy. As a result, many patients with HIV and chronic diarrhea have turned to herbal formulas for treatment. We assessed the effectiveness and safety of a Chinese herbal formulation (Source Qi) in reducing the number of stools per day related to HIV-associated, pathogen-negative diarrhea. Methods: Sixteen male patients received treatment with Source Qi in an 8-week, open-label study. Patients tested negative for cryptosporidium and other gastrointestinal pathogens, and had chronic diarrhea, defined as having three or more loose stools/day for >/=14 days (and no other treatable causes for diarrhea). Measurements of diarrhea included numbers of bowel movements/day, abnormal bowel movements/day, and liquid bowel movements/day. Subjects completed daily stool diaries an average of 2 weeks before and up to 8 weeks after starting Source Qi. Paired Wilcoxon tests compared the last week before treatment with each week of treatment. Results: There was a reduction in average number of stools/day in each week of treatment (-0.2 to -0.8), except week 1 (+0.1), with improvements in weeks 2-6 approaching or reaching statistical significance. Conclusions: A modest but sustained decrease in average number of stools/day was observed in patients with HIV-associated, pathogen-negative diarrhea. The entry criteria, 2-week run-in period, lack of benefit in week 1, and sustained benefit thereafter all suggest that the improvement was not due to bias.

Journal Article↗
PubMed2001

The Yersinia high-pathogenicity island: an iron-uptake island.

Highly pathogenic Yersinia carry a pathogenicity island termed high-pathogenicity island (HPI). The Yersinia HPI comprises genes involved in the synthesis of the siderophore yersiniabactin and can thus be regarded as an iron-uptake island. A unique characteristic of the HPI is its wide distribution among different enterobacteria such as Escherichia coli, Klebsiella, Citrobacter and Salmonella. Other types of iron-uptake systems are also carried by different pathogenicity islands in enterobacteria.

Animals↗
PubMed2006

Host-pathogen systems biology.

Unlike traditional biological research that focuses on a small set of components, systems biology studies the complex interactions between a large number of genes, proteins and other elements of biological networks and systems. Host-pathogen systems biology examines the interactions between the components of two distinct organisms, either a microbial or viral pathogen and its animal host or two different microbial species in a community. With the availability of complete genomic sequences of various hosts and pathogens, together with breakthroughs in proteomics, metabolomics and other experimental areas, the investigation of host-pathogen systems on a multitude of levels of detail has come within reach.

Animals↗
PubMed2003

Common infection strategies of plant and animal pathogenic bacteria.

Gram-negative bacterial pathogens use common strategies to invade and colonize plant and animal hosts. In many species, pathogenicity depends on a highly conserved type-III protein secretion system that delivers effector proteins into the eukaryotic cell. Effector proteins modulate a variety of host cellular pathways, such as rearrangements of the cytoskeleton and defense responses. The specific set of effectors varies in different bacterial species, but recent studies have revealed structural and functional parallels between some effector proteins from plant and animal pathogenic bacteria. These findings suggest that bacterial pathogens target similar pathways in plant and animal host cells.

Animals↗
PubMed1999

Early events in host-pathogen interactions.

Research focused on early events in host-pathogen interactions has provided new insights into fundamental aspects of microbial pathogenicity and plant responses. Considerable progress has been made in understanding regulation of the delivery of pathogenicity determinants from bacteria into plant cells, signal cascades involved in fungal pathogenicity, the co-ordinating role of the plant cytoskeleton in plant defence and calcium flux as a primary signalling function during the hypersensitive reaction.

Bacteria↗
PubMed2001

Whole genome plasticity in pathogenic bacteria.

The exploitation of bacterial genome sequences has so far provided a wealth of new general information about the genetic diversity of bacteria, such as that of many pathogens. Comparative genomics uncovered many genome variations in closely related bacteria and revealed basic principles involved in bacterial diversification, improving our knowledge of the evolution of bacterial pathogens. A correlation between metabolic versatility and genome size has become evident. The degenerated life styles of obligate intracellular pathogens correlate with significantly reduced genome sizes, a phenomenon that has been termed "evolution by reduction". These mechanisms can permanently alter bacterial genotypes and result in adaptation to their environment by genome optimization. In this review, we summarize the recent results of genome-wide approaches to studying the genetic diversity of pathogenic bacteria that indicate that the acquisition of DNA and the loss of genetic information are two important mechanisms that contribute to strain-specific differences in genome content.

Bacteria↗
PubMed1999

Difference between Escherichia coli O157:H7 and non-pathogenic E. coli: survival and growth in seasonings.

We examined the survival and growth of Escherichia coli O157:H7 cells incubated with several seasonings, in comparison with those of non-pathogenic E. coli. The cells were incubated at 25 degrees C for 24 h with several concentrations of NaCl, sucrose, soy sauce, worcester sauce and tomato ketchup, and their survival ratios were determined. The E. coli O157:H7 strains showed relatively higher survival ratios in 0.5-1.0 M sucrose, 25% soy sauce and 12.5-50% worcester sauce than the non-pathogenic strains, but slightly lower survival ratios in 0.5-2.0 M NaCl. A noteworthy difference between E. coli O157:H7 and the non-pathogenic strains was that incubation in the presence of 12.5% soy sauce allowed the growth of E. coli O157:H7 strains but reduced the viable cell numbers of non-pathogenic E. coli strains.

Journal Article↗
PubMed2004

Zoonotic Babesia: possibly emerging pathogens to be considered for tick-infested humans in Central Europe.

The three host-tick Ixodes (I.) ricinus is regarded as an important vector of tick-borne microorganisms pathogenic for humans in central Europe and is primarily known as the main vector of Borrelia (B.) burgdorferi and the virus causing tick-borne encephalitis (TBE), the most clinically relevant tick transmitted pathogens for humans in European countries. Furthermore, it is now well established that I. ricinus also transmits Ehrlichia (E.) phagocytophila, Babesia (Ba.) divergens, and Ba. microti, all agents of zoonotic infections in dear, sheep, cattle, dogs, and horses. In addition to their known zoonotic potential, recent molecular-epidemiological and seroepidemiological surveys as well as increasingly reported clinical cases of infections caused by these tick-borne organisms other than B. burgdorferi (TOBB) also strongly suggest a possible relevance of Babesia, Ehrlichia and Rickettsia for humans at risk in Europe. However, there are few medical microbiological investigations and epidemiological data on the distribution and relevance of Babesia for humans in our part of the northern hemisphere. There is also very little diagnostic and clinical knowledge on human babesiosis in many regions of Europe. Furthermore, sophisticated diagnostic tools designed for the reliable detection of the underlying pathogens, are not yet generally available to the microbiological laboratory. This review aims to provide basic information on human babesiosis and the most relevant causative pathogens of the disease in Europe and to draw attention to this parasitic infection as a possibly emerging and probably under-diagnosed disease in this part of the northern hemisphere.

Animals↗
PubMed2000

Host-pathogen interactions in mycoplasma pathogenesis: virulence and survival strategies of minimalist prokaryotes.

Despite their very small genomes mycoplasmas are successful pathogens of man and a wide range of animal hosts. Because of the lack of effective therapeutics and vaccines, mycoplasma diseases continue to be a significant problem for public health as well as livestock production with major socio-economic consequences worldwide. Recent outbreaks and epidemiological studies predict that the incidence of human and animal mycoplasma diseases might increase which indicates the urgent need to develop new approaches for prevention and therapy. Development of such reagents, however, requires a solid understanding of the molecular biology of mycoplasma infections. Knowledge in this field has considerably increased during the past decade since new techniques have been developed and adapted to mycoplasmas that allow these organisms to be studied at the molecular level. Research on the two human pathogens Mycoplasma pneumoniae and Mycoplasma genitalium of which the genome sequences have recently been completed as well as the substantial number of studies carried out on the AIDS-associated mycoplasmas, Mycoplasma penetrans and Mycoplasma fermentans, has led the way, but a number of animal mycoplasmas are becoming increasingly appreciated as models for the study of the molecular basis of mycoplasma diseases. This review summarizes and highlights some of the recent findings concerning the molecular interactions that occur between pathogenic mycoplasmas and their hosts, both the common strategies as well as some unique approaches evolved by particular mycoplasma pathogens, including adherence to and uptake into non-phagocytic host cells, as well as mechanisms of escaping the host immune system.

Animals↗
PubMed1993

Pathways to the impairment of human nutritional status by gastrointestinal pathogens.

Gastrointestinal pathogens are of three varieties, those that can, and often do, take the life of the host, those that infect transiently and rarely are life-threatening, and those (parasites) that establish a relatively prolonged residence or colonization of the host's alimentary tract. In the case of the second form, if infections are recurrent, both catabolic effects during the episode and failure to digest foods and/or absorb nutrients results. Similarly, catabolic wastage through activation of the acute phase response, and interference with the host's acquisition of nutrients by maldigestion, malabsorption, intestinal losses and competition with the parasite burden can impair growth and nutrition with helminthic infections. Growth and nutrition with respect to all of the macronutrients and virtually all of the micronutrients have been documented to be adversely affected by gastrointestinal pathogens. For its burgeoning importance as a worldwide health problem, both with the HIV virus as a direct intestinal pathogen and with the opportunistic gut infections occurring in the immunocompromised host, AIDS represents the emerging context of the impairment of nutritional status by intestinal pathogens.

AIDS-Related Opportunistic Infections↗
PubMed2006

Genetic variation in Drosophila melanogaster pathogen susceptibility.

Genetic variation in susceptibility to pathogens is a central concern both to evolutionary and medical biologists, and for the implementation of biological control programmes. We have investigated the extent of such variation in Drosophila melanogaster, a major model organism for immunological research. We found that within populations, different Drosophila genotypes show wide-ranging variation in their ability to survive infection with the entomopathogenic fungus Beauveria bassiana. Furthermore, striking divergence in susceptibility has occurred between genotypes from temperate and tropical African locations. We hypothesize that this may have been driven by adaptation to local differences in pathogen exposure or host ecology. Genetic variation within populations may be maintained by temporal or spatial variation in the costs and benefits of pathogen defence. Insect pathogens are employed widely as biological control agents and entomopathogenic fungi are currently being developed for reducing malaria transmission by mosquitoes. Our data highlight the need for concern about resistance evolution to these novel biopesticides in vector populations.

Animals↗
PubMed1998

Emerging pathogens: Isospora, Cyclospora and microsporidia.

Isospora belli, Cyclospora cayetanensis as well as several species of microsporidia are recognized as emerging protozoan pathogens of humans. All are obligate intracellular parasites, with Isospora and the microsporidia being primarily associated with immunocompromised hosts. Cyclospora is a cause of traveller's diarrhoea, and is responsible for water-borne and food-borne outbreaks of disease. Drug treatment is available for these infections. Improved diagnostic methods including the autofluorescence of I. belli and C. cayetanensis oocysts have assisted in the routine detection of these pathogens. Since the recognition of immunosuppression due to HIV infection, microsporidia have become recognized as important human pathogens with a continuing expansion of the parasite-associated clinico-pathological spectrum. The small size, intracellular nature and poor staining properties with many histological stains result in under-reporting of microsporidial infections. Trichrome stain and optical brighteners are used to detect spores in faeces, urines, respiratory secretions and other aspirates. Electron microscopy remains an important diagnostic method but its sensitivity is relatively poor. Molecular techniques should overcome current diagnostic limitations. The ability to extract DNA and amplify by PCR directly from clinical samples has increased the usefulness of molecular methods. Restriction fragment length polymorphism analysis of amplicons can be used to determine genus, species and strain types of various microsporidia. Increased specificity is required in primer design because current primers used for amplifying non-microsporidian DNA also amplify microsporidian DNA. Diagnosis and pathogen characterisation rely increasingly on PCR-based approaches, and the sequence analysis approach becomes increasingly feasible and affordable. However, robust, reliable and sensitive methods are still required for dissecting pathogenesis, epidemiology, transmission routes and sources of infections.

Animals↗
PubMed2001

Epidemiologic profiling: evaluating foodborne outbreaks for which no pathogen was isolated by routine laboratory testing: United States, 1982-9.

The objective was to evaluate foodborne outbreaks of undetermined aetiology by comparing them to pathogen-specific epidemiologic profiles of laboratory-confirmed foodborne outbreaks. National foodborne outbreak data reported to CDC during 1982-9 were categorized by clinico-epidemiologic profiles based on incubation, duration, percent vomiting, fever and vomiting to fever ratio. From the pathogen-specific profiles, five syndromes were developed: a vomiting-toxin syndrome resembling Bacillus cereus and Staphylococcus aureus; a diarrhoea-toxin syndrome characteristic of Clostridium perfringens, a diarrhaeogenic Escherichia coli syndrome, a Norwalk-like virus syndrome, and a salmonella like syndrome. Of 712 outbreaks, 624 (87.6%) matched one of five syndromes; 340 (47.8%) matched the Norwalk-like syndrome and 83 (11.7%) matched the salmonella-like syndrome. After combining information on known pathogens and epidemiologic profiles, only 88 (12.4%) outbreaks remained unclassified. Norwalk-like virus outbreaks appear as common as salmonella-like outbreaks. We conclude that profiling can help classify outbreaks, guide investigations and direct laboratory testing to help detect new and emerging pathogens.

Algorithms↗
PubMed2002

Epidemiological consequences of a pathogen having both virulent and avirulent modes of transmission: the case of rabbit haemorrhagic disease virus.

A number of pathogens cause chronic infection in survivors of acute disease and this is believed to be a common means of persistence, including for highly virulent agents. We present a model in which transmission from chronically infected hosts causes chronic infection in naive individuals, without causing acute disease--indeed 'protecting' against it. Thus the pathogen obtains the benefit of virulence (high transmission rate), but mitigates against the cost (high host mortality). Recent findings suggest that rabbit haemorrhagic disease virus (RHDV), a highly contagious and virulent pathogen, may also utilize this alternative, 'avirulent', mode of transmission. The model may resolve the paradox of how RHDV can be highly prevalent in some populations, in the absence of mortality. Differences in host demography determine whether avirulent transmission prevents large-scale mortality (as in most UK populations) or not. Other pathogens may exhibit similar behaviour and the implications for emerging diseases in general are discussed.

Acute Disease↗