SEARCH · PubMed Health

Results for “Pathogen”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

PubMed1992

Differentiation between pathogenic and non-pathogenic Yersinia enterocolitica strains by colony hybridization with a PCR-mediated digoxigenin-dUTP-labelled probe.

The Polymerase Chain Reaction (PCR) method was used to generate a vector-free digoxigenin-dUTP labelled probe that targets the Yersinia enterocolitica gene encoding the heat stable enterotoxin (yst). The probe was used in DNA-DNA colony hybridization to screen 113 strains of Y. enterocolitica and related species for the presence of the enterotoxin gene. In Y. enterocolitica, the probe clearly discriminated between pathogenic and non-pathogenic strains even those belonging to the same serotype. Of the other Yersinia species, only three strains of Y. kristensenii possessed DNA sequences homologous to the yst gene. The probe was further checked for its specificity in artificially inoculated fecal samples and could easily detect the target sequence of the yst gene. The digoxigenin-labelled probe proved to be a reliable epidemiological tool to discriminate between pathogenic and non-pathogenic strains in pure and mixed culture, thus offering the advantage of using a non-radioactive detection system in clinical laboratories with the possibility of reusing the same hybridization solution several times and obtaining results within a relatively short time.

Animals↗

PubMed1975

Untraditional glucose fermenting actinomycetes as human pathogens. Part II: Rothia dentocariosa as a cause of abdominal actinomycosis and a pathogen for mice.

Rothia dentocariosa was proved as a primary pathogen for man in the case of abdominal infection of a 19 year old woman. Clinical findings were typical for actinomycosis and the patient was cured with penicillin following surgery. Actinomycotic granules were proved by direct microscopy in the pus and R. dentocariosa was recovered as a single pathogen according to the microscopy. Two morphologically distinct isolates recovered from primocultures were described. They were studied separately and finally they were recognized as physiologically identical varieties of a single organism. In addition, the two morphological varieties of R. dentocariosa were considered to represent a particular kind of variability of the A-N type. The isolated germ was found to be pathogen for mice. Intraperitoneal infections provoked multiple nodules formation which were grown into the internal organs of experimental animals. The nodules were encapsulated and tended to spread without regard to the natural tissue plan. They contained pus involving microgranules of viable germs. This first report of the natural human infection caused by R. dentocariosa is the precedent for the definite establishing of this aerobic glucose fermenting actinomycete amidst the untraditional potential pathogens of human actinomycosis.

Actinomycetaceae↗

PubMed1978

Pathogenicity of cultivated murine leprosy bacilli Hawaiian-Ogawa strain in mice. 1. The pathogenicity of bacilli from rough colonies.

This paper deals with the pathogenicity of cultivated murine leprosy bacilli from rough colonies of Hawaiian-Ogawa strain in mice. This strain was isolated by Ogawa, in 1970, on Ogawa's 1% egg yolk medium [1], from mice previously inoculated with Hawaiian strain of murine leprosy bacilli which has been maintained by passages from mice to mice. The pathogenicity of Hawaiian-Ogawa strain was found to belong to the same pattern as Hawaiian strain when the subcutaneous inoculation test was carried out in C57BL/6 and C3H mice, the former being representative of the benign type and the latter being representative of the malignant type. In KK mice of the intermediate type with Hawaiian bacilli, however, Hawaiian-Ogawa bacilli produced the lesions with malignant features in almost all the male mice, while the female mice were divided into two groups roughly half showing the intermediate or malignant type. In DDD mice of the benign type with Hawaiian bacilli, some cases of the male mice showed the malignant features, whereas almost all the female mice were of the benign type in the same experimental conditions. The pathogenicity of Hawaiian-Ogawa bacilli in mice did not revert into that of Hawaiian bacilli even after serial mouse passage. There are slight but definite differences in the mouse pathogenicity between Hawaiian-Ogawa and Hawaiian strains.

Animals↗

PubMedDate not supplied

[Comparative study of the RNA-polymerase activity of non-pathogenic and pathogenic influenza viruses A and B].

Activity of RNA polymerase was studied in original non-pathogenic for mice viruses of influenza A and B (A/seal/Massachusetts 1/80, A/USSR 05/81, A/Philippines 2/82 and B/Singapore 227/79) and of their pathogenic derivatives. All the non-pathogenic viruses studied exhibited the low rate of transcriptase activity. Pathogenic derivatives of these strains exhibited higher activity of RNA polymerase, which was 1.5-3-fold higher as compared with the original strain. During passage of influenza viruses A and B in mice organism selection of the population appears to occur, which had the highest transcriptase activity.

Animals↗

PubMed1988

Biochemistry and pathogenicity of echovirus 9. III. Thermosensitive mutants of echovirus 9, strain Barty, with reduced pathogenicity for newborn mice.

Different clinical isolates of echovirus 9 are known to vary strikingly with regard to pathogenicity. Prototype strain Hill and strain Barty have previously been shown to differ not only in paralytogenic potency for newborn mice but also in a number of in vitro characteristics related to virus capsid structures. A series of mutants of strain Barty, thermosensitive for replication at 40 degrees C, was isolated after mutagenization with 5-fluorouracil. For all mutants the virus dose required to paralyze 50% of the infected animals was significantly higher than of the parent strain Barty. This reduced pathogenicity was observed at normal room temperature where the baby mice had a body temperature of 32.5 degrees C, which is even below the permissive temperature for growth of the mutants. The paralytogenic potencies did not further decrease when the mice where kept at elevated room temperature and had a body temperature of 35.1 degrees C. Thus, the reduced pathogenicity is apparently not a direct consequence of thermosensitivity of growth. Biochemical and biophysical characterization indicated that at least two of the eight mutants have an alteration in capsid protein.

Animals↗

PubMed1981

Characterization of volatile sulphur production by pathogenic and non-pathogenic strains of oral Bacteroides.

Marked differences were observed in intermediate sulphur metabolism between non-pathogenic strains of Bacteroides melaninogenicus var melaninogenicus (CP-) and pathogenic Bacteroides melaninogenicus asaccharolyticus (CP+). The CP+ strains, which produced collagenase and protease and caused formation of abscesses when injected subcutaneously into groins of guinea pigs, produced copious amounts of volatile sulphur compounds (VSC) which consisted predominantly of CH3SH and (CH3S)2. Hydrogen sulphide occurred in considerably lesser amounts. CP+ cultures yielded 8-fold more total volatile S, 15-fold more CH3SH and 260-fold more (CH3S)2 during 24 h of incubation in trypticase-yeast extract medium. Whereas H2S accounted for 60 per cent of the total volatile S content of the head-space of CP- cultures, it represented only 8 per cent of the volatile S in CP + systems. Although the CP-organisms did not grow as well as CP +, the differences in concentration of VSC may be only partly related to the disparity in growth rates. When the VSC concentrations were calculated on the basis of equivalent optical density of 1.0, the CP + strains still produced over 3-fold more total volatile S, 6-fold more CH3SH and 100-fold more (CH3S)2. A similar allowance for growth rate suggests that CP-strains may possess a greater potential to produce H2S. Both groups metabolized S-containing amino acids and serine, resulting in appreciable increases in H2S production by CP-. However, the two groups appeared to metabolize the carbon moiety of cystine an cysteine by different pathways. The addition of glucose to the medium depressed total volatile S production by both CP+ and CP-strains, attributable mostly to lower H2S levels. Whereas the omission of yeast extract and charcoal treatment of trypticase did not adversely effect the activity of CP+, it further markedly reduced the capacity of CP-cultures to produce VSC. These results suggest that VSC analysis offers a convenient means of assessing strain differences and pathogenic potential of B. melaninogenicus.

Bacteroides↗

PubMed1992

Polymerase chain reaction for differentiation between pathogenic and non-pathogenic serotype 1 Marek's disease viruses (MDV) and vaccine viruses of MDV-serotypes 2 and 3.

A polymerase chain reaction (PCR) test based on primers flanking the 132 bp tandem repeat in pathogenic MDV-1 DNA was developed. These primers amplify a dimer or a trimer 132 bp repeat in pathogenic MDV-1 DNA from blood and organs of commercial chickens with Marek's disease (MD) symptoms. Using the same primers in a radioactive PCR test, it was possible to distinguish between vvMDV-1 and the non-pathogenic MDV-1 CVI-988 vaccine in which the 132 bp repeats in the DNA were increased up to 9 repeats. The MDV-1 specific primers did not amplify MDV-2 (SB1) and MDV-3 (HVT) DNA. Primers prepared according to the nucleotide sequence of MDV-1 antigen A gene amplified MDV-1 DNA only. Specific primers prepared according to the nucleotide sequence of MDV-3 (HVT) antigen A gene amplified MDV-3 DNA but not MDV-1 nor MDV-2 DNA. The results of the present study show that the PCR tests can be used for the early identification of vvMDV-1 DNA in pathological samples from diseased commercial chickens and to distinguish between the vvMDV-1 and the three types of virus vaccines used to immunize chickens. The tests are accurate and can be performed in the presence of vaccine virus DNA in the sample.

Animals↗

PubMed1988

Pathogenic and non-pathogenic Entamoeba: pore formation and hemolytic activity.

Pore-forming activity in planar lipid bilayers and liposomes of extracts from differentially pathogenic Entamoeba and the capacity of trophozoites and subcellular fractions to lyse human red blood cells (hrbc) were investigated. In all amebas studied, the two activities paralleled each other. They were high in E. histolytica irrespective of the virulence of the particular strain, but low in non-pathogenic E. histolytica-like amebas of human origin as well as in E. invadens, which is pathogenic for reptiles, and in E. moshkovskii isolated from sewage. We conclude that the capacities to insert pores and to lyse are not sufficient for virulence although they may be necessary. The subcellular distribution of the hemolytic activity of E. histolytica and its sensitivity to a variety of inhibitors and activators differ from those of other known amebic cytotoxic activities including pore formation. Therefore, there may be an additional constituent of E. histolytica involved in the cytotoxicity of the parasite.

Animals↗

PubMed1989

Nasopharyngeal culture with quantitative analysis of pathogenes in chronic otitis media with effusion. Effects on pathogen yield of different swabs and transport methods.

The influence of different swabs and transport media on nasopharyngeal culture pathogen recovery has been studied in patients with chronic otitis media with effusion. Transport times of less than two hours have been used. Protecting the cotton wire swab with a polyethylene shealth to prevent contamination by nasal flora did not have any significant influence either on the recovery of potential pathogens or on the contaminating nasal flora. Facilitating a quantitative analysis of the nasopharyngeal culture by transporting the specimen in empty tubes gave a pathogen recovery rate similar to that with transport in Stuart medium, whereas an attempt at transporting in sodium chloride or prereduced PY broth led to significantly lower yields of Branhamella catarrhalis (p less than 0.01) and in PY broth on Haemophilus influenzae as well (p less than 0.01).

Child, Preschool↗

PubMed1976

Attenuation of pathogenicity of fowl plague virus by recombination with other influenza A viruses nonpathogenic for fowl: nonexculsive dependence of pathogenicity on hemagglutinin and neuraminidase of the virus.

A number of antigenic hybrids of influenza A viruses were produced possessing either the hemagglutinin or the neuraminidase of fowl plague virus and the corresponding antigen derived from another influenza A virus. Other recombinants were obtained carrying both surface antigens of fowl plague virus but differing from the parent in certain biological properties. None of the recombinants isolated were pathogenic for adult chickens. Most recombinants obtained after crosses between reciprocal recombinants carrying both fowl plague virus surface antigens were also apathogenic for chickens. Using the same parent recombinants for double infection some of the progeny "back-recombinants" were pathogenic, whereas others were not. From these results it is concluded that the surface components do not by themselves determine the pathogenicity of influenza A viruses.

Animals↗

PubMed1990

[Pneumonia in AIDS: pathogen spectrum and diagnostic value of various fiberoptic bronchoscopy methods for the detection of pathogens].

39 fibre-bronchoscopic examinations were performed prospectively in 29 AIDS-patients with pneumonia. Specimens were obtained from the central bronchial system with a protected brush and by suction, from the infiltrated peripheral area by catheter suction, protected brush, bronchoalveolar lavage (BAL) and transbronchial biopsy in randomized order. In patients with non-bacterial pneumonia, pneumocystis carinii (n = 20) was the most frequent pathogen. In this group BAL had a significantly higher rate of pathogen detection than other techniques. In patients with bacterial pneumonia (n = 10) the pathogens were found in all cases by suction from the central bronchial system. Fibre-bronchoscopy in patients with AIDS and pneumonia should include specimens from the central bronchial system and a bronchoalveolar lavage.

Acquired Immunodeficiency Syndrome↗

PubMed1987

Superiority of the chimpanzee animal model to study the pathogenicity of known Mycoplasma pneumoniae and reputed mycoplasma pathogens.

As far as we know, humans are the only known natural hosts for M. pneumoniae disease. Whereas volunteer studies have provided useful data on the pathogenesis of disease and efficacy of vaccines, experimentally inducing disease in humans raises serious ethical questions and has become increasingly difficult to defend. Thus, there is a genuine need for a satisfactory animal model to study M. pneumoniae disease. Using the cotton rat and developing chick embryo models, Eaton and co-workers (9-13) have clearly shown that the infectious "Eaton agent" was the cause of primary atypical pneumonia. After the causative agent was identified as M. pneumoniae (14), more definite and quantitative studies were possible. The hamster animal model has provided most of our information on the pathogenicity of strains, the pathogenesis of disease and the potency of inactivated vaccines. However, protective data obtained in hamsters immunized with the TS mutant vaccines did not correlate with data obtained in humans, raising concern regarding the use of the hamster animal model to evaluate the potency of live TS vaccines. The chimpanzee animal model has a number of advantages. Chimpanzees become clinically ill, show positive X-ray findings, and develop cold agglutinin titers. In fact, the experimentally induced disease in chimpanzees is remarkably similar to naturally occurring primary atypical pneumonia in patients. Because of the close genomic relationship, immunologic reagents prepared and used for human studies can also be used successfully in chimpanzee studies. The chimpanzee model also has some serious disadvantages. They are expensive to house and maintain and are generally not available to the scientific community. Nonetheless, chimpanzees are probably the best, most meaningful animal models established thus far to examine the infectious process, the immune response and the pathogenesis of this disease and to determine approaches to effective therapy and immunization of diseases produced by known pathogens, like M. pneumoniae, as well as reputed mycoplasma pathogens, such as M. genitalium and M. hominis.

Animals↗

PubMed1992

The pathogenicity of Ab4p, the sequenced strain of equine herpesvirus-1, in specific pathogen-free foals.

The sequencing of the genome of equine herpesvirus-1 (EHV-1) is reported in Elizabeth A. R. Telford, Moira S. Watson, Kathryn McBride, and Andrew J. Davison, 1992, Virology, 189, 304-316. The sequence was derived using a plaque-purified clone of EHV-1 strain Ab4 (designated Ab4p). To ensure that Ab4p shares the pathogenic characteristics of parental Ab4 (hereafter Ab4), both were inoculated intranasally into foals, specifically free from EHV-1 and EHV-4. Clinical signs, including rectal temperature, were similar for both viruses. In addition, nasal shedding of virus was observed over a 1- to 2-week period postinfection, and viremia was established with both Ab4 and Ab4p. Isolation of virus from one foal following intravenous administration of steroids indicates that Ab4p can establish latency and undergo reactivation. Finally, retinal lesions were observed and these were similar to those seen with Ab4. In conclusion, several pathogenic characteristics of Ab4 are retained in the plaque-purified clone, Ab4p.

Animals↗

PubMedDate not supplied

Occurrence of acute infectious bursal disease with high mortality in Japan and pathogenicity of field isolates in specific-pathogen-free chickens.

Highly virulent infectious bursal disease virus (IBDV) was isolated from field cases, and the pathogenicity of the isolates was examined in specific-pathogen-free chickens. Chickens inoculated with the isolates developed severe clinical disease with a high mortality rate. Histopathologically, infectious bursal disease was characterized by bursal and thymic necrosis, aplastic anemia, acute hepatitis with fatty change, and systemic inflammatory response. In addition to functional abnormalities in the liver, a hypoxic state was induced by aplastic anemia and severe inflammation in the pulmonary air capillary walls. These pathological changes appeared to be closely related to the cause of death.

Animals↗

PubMedDate not supplied

Pathogenicity of recent isolates of infectious bursal disease virus in specific-pathogen-free chickens: protection conferred by an intermediate vaccine strain.

The pathogenicity of recent isolates of infectious bursal disease virus and the protection conferred against them by a commercial vaccine strain of intermediate virulence were examined in specific-pathogen-free chickens. Based on clinical signs, mortality, and macroscopic lesions in susceptible chickens, the isolates designated as A-Delmarva and U-28 were distinct from a previously known serotype I virulent isolate (Edgar). Histopathological analysis of the bursa of Fabricius did not establish differences between the field isolates. Although the vaccine strain produced some degree of bursal damage in antibody-free chickens, it was significantly less severe than the damage caused by the field isolates. The active immune response induced by vaccination was cross-protective against the pathological effects produced by the different isolates used in this study.

Animals↗

PubMed1986

Comparative study of the temperature profiles of growth and death of the pathogenic yeast Cryptococcus neoformans and the non-pathogenic Cryptococcus albidus.

The temperature profiles of two species of Cryptococcus were compared. The pathogenic Cr. neoformans had a maximum temperature for growth of 39.8 degrees C and the non-pathogenic Cr. albidus, of 30.2 degrees C. The specific growth rates measured in the former were of an order of magnitude higher than in the latter, whereas the Arrhenius plots of the specific thermal death rates did not show a significant difference.

Cryptococcus↗

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↗