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At least 109 records · Page 6Linked to original sources
PubMed2001

Characterization of less pathogenic infectious molecular clones derived from acute-pathogenic SHIV-89.6p stock virus.

For a better understanding of the acute pathogenicity of SHIV-89.6P stock virus, which induces prominent CD4 cell loss within a month after inoculation in monkeys, we have constructed four infectious molecular clones (cl 18, cl 64, cl 69, and cl 71). Cl 64, cl 69, and cl 71, like the parental virus, showed a high in vitro replication ability and a pathogenic-like effect (CD4 downmodulation) in a monkey CD4(+) cell line, whereas cl 18 showed a lower replication ability and could not downmodulate CD4. Cl 64, which has characteristics similar to those of the parental virus in vitro, was inoculated into four rhesus monkeys. All monkeys showed a plasma viral load similar to that of the parental virus with a peak at 2 weeks after inoculation. However, the viral load gradually decreased and the virus failed to cause an AIDS-like disease in infected monkeys, but it induced a strong antiviral antibody response. These results demonstrate the polyclonal nature of the parental SHIV-89.6P virus stock and demonstrate that cl 64, aside from its high replicability, may differ qualitatively from the parental virus.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Adherence of pathogenic and non-pathogenic Entamoeba histolytica strains to neutrophils.

The adherence of polymorphonuclear leukocytes (PMNs) to eight pathogenic and nine nonpathogenic strains of Entamoeba histolytica was examined. No difference between pathogenic and nonpathogenic strains was found. The addition of different carbohydrates confirmed the importance of the 170-kDa lectin of E. histolytica in binding to PMNs, corroborated by the finding that treatment of PMNs with galactosidase inhibited adherence. Inhibition of the microfilament system of E. histolytica using cytochalasin B resulted in a loss of adherence to PMNs. Inhibition of the microtubule system using nocodazole did not affect adherence. Preincubation of the trophozoites with serum resulted in enhanced adherence, but the serum factor responsible for this effect could not be identified. Fibronectin, vitronectin, integrins (CD11/CD18 molecules), complement, and mannose-binding protein did not seem to mediate adherence between E. histolytica and PMNs. In summary, these results indicate that defective adherence mechanisms are not a common feature of nonpathogenic E. histolytica strains.

Acetylgalactosamine↗
PubMedDate not supplied

Virulence of pathogenic and non-pathogenic zymodemes of Entamoeba histolytica (Indian strains) in guinea-pigs.

Guinea-pigs were inoculated with Entamoeba histolytica strains isolated from cases of amoebic liver abscess, amoebic dysentery and asymptomatic cyst passers and the strains were classified in zymodemes by isoenzyme electrophoresis. It was observed that certain non-pathogenic zymodemes were potentially pathogenic for the guinea-pigs. The relationship of zymodemes and virulence in laboratory animals is discussed.

Amebiasis↗
PubMed1984

Protection against establishment of latent infections in mice immunized with a non-pathogenic herpes simplex virus mutant and reinfected with the pathogenic parental strain.

Immunization of hairless mice with a TK-, ACVr, non-pathogenic herpes simplex virus (HSV) type 1 mutant protected the mice against reinfection with lethal doses of the parental pathogenic HSV strain. The protection conferred by the mutant against the establishment of latency after reinfection with the parental strain was dependent on the site of reinfection; after reinfection at the same site, only 2% of mice became latently infected, compared to 32% after reinfection at a distant site. When inoculation with the mutant was done at two different sites, single reinfections at any site led to the establishment of latency in 4% of the mice. The mutant by itself was almost completely latency-negative: only 4.5% of the mice developed latency in trigeminal ganglia and 2.3% in the spinal ganglia. The rate of mutant-induced latent infections is partly related to the dose of the virus; however, lower doses of the mutant may not colonize the ganglia, and therefore fail to protect against challenge infections.

Animals↗
PubMed1992

Sequence analysis and relationships between meningococcal class 3 serotype proteins and other porins from pathogenic and non-pathogenic Neisseria species.

The presence of highly conserved regions within previously determined porin gene sequences from Neisseria meningitidis and Neisseria gonorrhoeae permitted the construction of oligonucleotide primers for PCR amplification of other neisserial porin genes. Although two separate porin genes (porA and porB) are present in N. meningitidis only a single fragment, corresponding to porB, could be amplified from this species. The amplified porB genes from four different meningococcal serotypes, which express the class 3 outer membrane protein, were sequenced. Amplified fragments corresponding to porin genes from N. lactamica and N. sicca were also sequenced. In common with the known neisserial porins, models of the organisation of the predicted proteins indicated trans-membrane structures with eight surface exposed loops. In the meningococcal class 3 proteins the main regions of sequence variation, which must be responsible for serotype specificity, were located on loops 5 and 7. A phylogenetic analysis of the family of porins from the Neisseria confirmed the close relationship of the meningococcal class 3 protein with the gonococcal PIA protein, while the gonococcal PIB protein was shown to be closely related to the N. lactamica porin. The close relationship seen between porins of the pathogenic and non-pathogenic Neisseriae identified no obvious virulence-associated regions in the proteins, but did suggest that the current nomenclature for neisserial porin genes may need reviewing.

Alleles↗
PubMed1995

Similarity between the Rhizobium meliloti fliP gene and pathogenicity-associated genes from animal and plant pathogens.

The nucleotide sequence of the Rhizobium meliloti (Rm) fliP gene was determined. Rm strains carrying insertions within this gene were non-motile, lacked flagella and formed normal N2-fixing root nodules on alfalfa. The FliP protein showed similarity to several bacterial gene products involved in pathogenicity in both plant and animal pathogens. It is likely that all of these proteins share a common functional role in the secretion of specific proteins from bacterial cells.

Amino Acid Sequence↗
PubMed1998

Determinants of pathogenicity and avirulence in plant pathogenic bacteria.

Many plant pathogenic bacteria possess a conserved protein secretion system that is thought to transfer Avr (avirulence) proteins, with potential activities in both parasitism and defense elicitation, into plant cells. avr genes may be acquired horizontally by these bacteria, and avr gene compositions are highly variable. In the past year, heterologous expression experiments have revealed that the products of avr genes can be interchanged among different genera of bacteria with retention of secretion, pathogenicity, and avirulence activities, suggesting mechanisms for rapid coevolution of these parasites with changing plant hosts.

Bacteria↗
PubMedDate not supplied

Use of the ProSpecT microplate enzyme immunoassay for the detection of pathogenic and non-pathogenic Entamoeba histolytica in faecal specimens.

A commercial microplate enzyme immunoassay (ProSpecT EIA; Alexon Inc., Sunnyvale, CA 94089, USA) was compared with conventional microscopy for the diagnosis of Entamoeba histolytica infection. Using specimens known to be infected, the sensitivity of the ProSpecT EIA was 78% and its specificity was 99%. No cross reaction with other intestinal parasites was observed. The ProSpecT EIA and conventional microscopy (using merthiolate-iodine-formaldehyde direct wet mounts and concentration techniques) were then used to detect E. histolytica infections in 431 patients in a mental hospital in Taiwan. Using single stool specimens, microscopy detected infection in 10.9% of the patients, compared with 16.9% detected by ProSpecT EIA. The latter method was simple and quick, but more expensive, and could be used to complement microscopy if a prompt diagnosis is desired clinically. However, ProSpecT EIA cannot differentiate between pathogenic E. histolytica and non-pathogenic strains (= E. dispar), which limits its usefulness.

Animals↗
PubMed1992

Ribosomal DNA sequences in the differentiation of pathogenic and non-pathogenic isolates of Entamoeba histolytica.

Recombinant ribosomal DNA sequences were amplified by PCR and used as probes to perform a fingerprint analysis of total DNA from different Entamoeba histolytica isolates. RFLPs obtained with one of the probes, R-1, support previous proposals that pathogenic and non-pathogenic E. histolytica are closely related, yet genotypically distinct. Another probe, R-2, while not distinguishing between the two forms of E. hystolytica, was able to differentiate between them and E. moshkovskii, which has morphologically identical cysts and trophozoites. A third probe, BR-1, identified strain-specific RFLPs.

Animals↗
PubMed1998

Quorum sensing and the cell-cell communication dependent regulation of gene expression in pathogenic and non-pathogenic bacteria.

Although it has been clear for some time that individual bacterial cells employ intra-cellular signalling systems to sense, integrate and process information from their surroundings, their widespread capacity to perceive information from other bacterial cells is only just beginning to be recognised. Recent work has established that diverse bacteria exploit a cell-cell communication device to regulate the transcription of multiple target genes. This communication device termed 'quorum sensing', depends on the production of one or more diffusible signal molecules termed 'autoinducers' or 'pheromones' which enable a bacterium to monitor its own cell population density. Quorum sensing is thus an example of multicellular behaviour in prokaryotes and regulates diverse physiological processes including bioluminescence, swarming, antibiotic biosynthesis, plasmid conjugal transfer and the production of virulence determinants in animal, fish and plant pathogens. In Gram-negative bacteria, the best understood family of signal molecules are the N-acylhomoserine lactones (AHLs) which vary predominantly in the presence or absence of an acyl chain C3 substituent (oxo- or hydroxy-) and length of the N-acyl side chain. However not all quorum sensing signal molecules are AHLs; in Gram-positive bacteria, they are often post-translationally modified peptides. Irrespective of the chemical 'language' employed, interference with either the synthesis or transmission of a quorum sensing signal molecule in pathogenic bacteria offers an exciting new strategy for controlling infection.

Gene Expression Regulation, Bacterial↗
PubMed2000

Pathogen-induced apoptosis of macrophages: a common end for different pathogenic strategies.

Microbe-macrophage interactions play a central role in the pathogenesis of many infections. Several bacterial pathogens induce apoptosis specifically in macrophages, but the mechanisms by which it occurs differ, and the resulting pathology can take different courses. Macrophage death caused by Shigella flexneri and Salmonella spp. has been shown to result in the release of pro-inflammatory cytokines. Conversely, Yersinia spp. induce apoptosis by suppressing the signalling pathways that lead to the production of tumour necrosis factor (TNF)-alpha, a cytokine essential for the control of this infection. It is likely that there are a variety of reasons why macrophages are particularly susceptible to pathogen-induced apoptosis. One reason may be the expression of surface receptors that recognize highly conserved bacterial components, such as lipopolysaccharide (LPS) and bacterial lipoproteins (BLPs). These receptors have recently been shown to activate pro-apoptotic signalling pathways. The roles of macrophage apoptosis in different disease processes are discussed.

Animals↗
PubMed1999

Identification of a pathogenicity island, which contains genes for virulence and avirulence, on a large native plasmid in the bean pathogen Pseudomonas syringae pathovar phaseolicola.

The 154-kb plasmid was cured from race 7 strain 1449B of the phytopathogen Pseudomonas syringae pv. phaseolicola (Pph). Cured strains lost virulence toward bean, causing the hypersensitive reaction in previously susceptible cultivars. Restoration of virulence was achieved by complementation with cosmid clones spanning a 30-kb region of the plasmid that contained previously identified avirulence (avr) genes avrD, avrPphC, and avrPphF. Single transposon insertions at multiple sites (including one located in avrPphF) abolished restoration of virulence by genomic clones. Sequencing 11 kb of the complementing region identified three potential virulence (vir) genes that were predicted to encode hydrophilic proteins and shared the hrp-box promoter motif indicating regulation by HrpL. One gene achieved partial restoration of virulence when cloned on its own and therefore was designated virPphA as the first (A) gene from Pph to be identified for virulence function. In soybean, virPphA acted as an avr gene controlling expression of a rapid cultivar-specific hypersensitive reaction. Sequencing also revealed the presence of homologs of the insertion sequence IS100 from Yersinia and transposase Tn501 from P. aeruginosa. The proximity of several avr and vir genes together with mobile elements, as well as G+C content significantly lower than that expected for P. syringae, indicates that we have located a plasmid-borne pathogenicity island equivalent to those found in mammalian pathogens.

Bacterial Proteins↗
PubMed1992

Asymptomatic intestinal colonization by pathogenic Entamoeba histolytica in amebic liver abscess: prevalence, response to therapy, and pathogenic potential.

Since the application of isoenzyme electrophoresis to the study of Entamoeba histolytica, the prevalence and natural history of asymptomatic intestinal colonization in patients with amebic liver abscess (ALA) has not been addressed. We prospectively evaluated this enteric phase in 50 patients with ALA, using two dosage regimens of metronidazole. The overall prevalence of asymptomatic colonization was 72% (36/50). All these isolates, without exception, proved to express pathogenic zymodemes. Despite a 100% clinical response of the hepatic lesions, failure to eradicate the organism from the bowel occurred in 20 of these 36 subjects. During longitudinal posttreatment surveillance, three carriers returned with second bouts of invasive disease: one with dysentery and two with liver abscesses. Thus, in patients with ALA, there is a high prevalence of intestinal colonization with exclusively pathogenic strains, and treatment with metronidazole frequently results in a continued carrier state. These carriers have a propensity for developing recurrent invasive disease and constitute a public health hazard.

Adult↗
PubMed2001

A pathogen-induced chitin-binding protein gene from pepper: its isolation and differential expression in pepper tissues treated with pathogens, ethephon, methyl jasmonate or wounding.

A chitin-binding protein (CBP) cDNA (CACBP1) was isolated from a cDNA library of pepper (Capsicum annuum L.) leaves infected with Xanthomonas campestris pv. vesicatoria. The deduced amino acid sequence of the CACBP1 gene which has chitin-binding domain and hinge region shares a high level of identity with CBP sequences from tomato, potato and tobacco. The CACBP1 gene was organ-specifically regulated in pepper plants, and differentially induced during the compatible and incompatible interactions of pepper with X. campestris pv. vesicatoria or Phytophthora capsici. Expression of the CACBP1 gene was rapidly induced in the incompatible interactions upon pathogen infection. Transcripts of the CACBP1 gene was highly inducible in the leaves of matured pepper plants by Colletotrichum coccodes infection. In situ hybridization results showed that CACBP1 mRNA was expressed in the phloem area of vascular bundles in C. coccodes-infected leaf tissues. The pathogen-inducible CACBP1 gene was also strongly induced and accumulated in pepper leaves by ethephon, methyl jasmonate or wounding. These data suggest that ethylene and jasmonate may act as signal molecules in the signal transduction pathways of the CBP gene induction during the pepper defense- or pathogenesis-related plant responses.

Acetates↗
PubMed2001

A cell wall component from pathogenic and non-pathogenic gram-positive bacteria (peptidoglycan) synergises with endotoxin to cause the release of tumour necrosis factor-alpha, nitric oxide production, shock, and multiple organ injury/dysfunction in the rat.

The incidence of sepsis and septic shock due to gram-positive organisms has increased dramatically over the last two decades. Interestingly, many patients with sepsis/septic shock have both gram-positive and gram-negative bacteria present in the bloodstream and these polymicrobial or "mixed" infections often have a higher mortality than infection due to a single organism. The reason for this observation is unclear. The aim of this study was to investigate whether cell wall fragments from gram-positive and gram-negative bacteria could synergise to cause the release of cytokines, shock, and organ injury/ dysfunction in vivo. Male Wistar rats were anaesthetised and received an intravenous bolus of vehicle (saline), lipopolysaccharide (LPS) from Escherichia coli (0.1 mg/kg), peptidoglycan (Pep G) from Staphylococcus aureus (S10 mg/kg), co-administration of LPS (0.1 mg/kg) and PepG from S. aureus (10 mg/kg), LPS (10 mg/kg), PepG from Bacillus subtilis, or co-administration of LPS and PepG from B. subtilis. Blood pressure and heart rate were monitored for 6 h before plasma samples were taken for the measurement of TNF-alpha, total nitrite, and biochemical indices of organ injury. Peptidoglycan from both pathogenic (S. aureus) and non-pathogenic (B. subtilis) gram-positive bacteria synergised with endotoxin to cause formation of TNF-alpha, nitrite, shock, and organ injury. Synergism between PepG and LPS may partly explain the high mortality associated with mixed bacterial infections, as well as the deleterious effects of translocation of bacteria, or their cell wall components from the gut lumen in patients with sepsis.

Animals↗
PubMed1994

Candida krusei: biology, epidemiology, pathogenicity and clinical manifestations of an emerging pathogen.

Early reports of Candida krusei in man describe the organism as a transient, infrequent isolate of minor clinical significance inhabiting the mucosal surfaces. More recently it has emerged as a notable pathogen with a spectrum of clinical manifestations such as fungaemia, endophthalmitis, arthritis and endocarditis, most of which usually occur in compromised patient groups in a nosocomial setting. The advent of human immunodeficiency virus infection and the widespread use of the newer triazole fluconazole to suppress fungal infections in these patients have contributed to a significant increase in C. krusei infection, particularly because of the high incidence of resistance of the yeast to this drug. Experimental studies have generally shown C. krusei to be less virulent than C. albicans in terms of its adherence to both epithelial and prosthetic surfaces, proteolytic potential and production of phospholipases. Furthermore, it would seem that C. krusei is significantly different from other medically important Candida spp. in its structural and metabolic features, and exhibits different behaviour patterns towards host defences, adding credence to the belief that it should be re-assigned taxonomically. An increased awareness of the pathogenic potential of this yeast coupled with the newer molecular biological approaches to its study may facilitate the continued exploration of the epidemiology and pathogenesis of C. krusei infections.

Animals↗
PubMed1990

Fate of pathogenic and non-pathogenic Escherichia coli strains in two fermented milk products.

The growth and survival of pathogenic and non-pathogenic strains of Escherichia coli was determined in traditionally fermented pasteurized and unpasteurized milk and in Lacto, an industrially fermented milk. Each milk treatment was incubated at 20 degrees C for 24 h and then stored at either 20 degrees C or 5 degrees C for 96 h. Lacto inhibited all the three E. coli strains. Two strains could not be recovered and the third survived only in very low numbers after 24 h storage of Lacto at both 20 degrees C and 5 degrees C. All three E. coli strains survived and multiplied to maximum cell numbers in the range 10(7)-10(9)/ml during traditional fermentation of unpasteurized milk. Cell numbers decreased to 10(3)-10(6) and 10(2)-10(5) during storage of the fermented product at 20 degrees C and 5 degrees C respectively. Higher maximum numbers, 10(9)-10(10), of the three strains of E. coli were attained during traditional fermentation of pasteurized milk. The numbers decreased to 10(5)-10(8) and 10(4)-10(7) during storage of the fermented product at 20 degrees C and 5 degrees C respectively. Generally, fewer E. coli survived when the fermented milk products were stored at refrigeration temperature.

Animals↗