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At least 91 records · Page 5Linked to original sources
PubMed2003

Evaluation of pathogenic potential of avian influenza virus serotype H9N2 in chickens.

Recently seven isolates of avian influenza virus (AIV) serotype H9N2 recovered from an outbreak of AI were analyzed on the basis of their biological and molecular characteristics. All the isolates belonged to the low-pathogenicity group of AIV. To further evaluate their pathogenic potential in association with other organisms, an isolate was inoculated experimentally in chickens using different routes and subsequently challenged with infectious bronchitis virus, Ornithobacterium rhinotracheale or Escherichia coli. The virus isolation and seromonitoring data revealed a significant role of Escherichia coli in aggravating the clinical condition of the birds earlier infected with AIV (H9N2). The AIV-antigen was detected in lung, trachea, kidney, and cloacal bursa among the infected birds, using immunofluorescent antibody technique. In another experiment, chickens that were immunosuppressed chemically showed high mortality when challenged with AIV H9N2. The results indicated that this low pathogenicity AIV (H9N2) isolate could produce severe infection depending on the type of secondary opportunistic pathogens present under field conditions. This may explain the severity of infection with the present H9N2 outbreak in the field. A prolonged antibacterial therapy in flocks infected with AIV H9N2 and use of oil-based vaccine at an early age in new flocks has helped to control this infection and the disease.

Animals↗
PubMed1999

Loss of pathogenic potential after cloning of the low-passage Borrelia burgdorferi ZS7 tick isolate: a cautionary note.

To study clonal polymorphism of Borrelia hurgdorferi antigens in the course of an experimental infection sequence, the low-passage tick isolate ZS7 was cloned by two rounds of agar subsurface plating. The resulting clones showed a variable pathogenic potential after experimental infection of C.B-17. scid mice. The test clone 4.2.II, selected for virulence by two passages in immunodeficient scid mice, failed to establish a successful infection in immunocompetent AKR/N mice, indicating the loss of pathogenicity traits required for evasion of the specific immune response. Cloning of natural or clinical B. burgdorferi isolates is a prerequisite for analyzing genetic and antigenic variation of the pathogen. However, the inevitable propagation in artificial media during cloning may lead to a loss of pathogenic features rendering the subsequent experimental infection of animals impossible. A combined procedure of in vitro cloning and in vivo selection also does not solve the dilemma because B. burgdorferi variants arise by recombinatorial processes in the pathogen's dynamic genome during the course of infection. Consequently, the resulting bacterial isolates from infected animal tissues represent again non-clonal, heterogeneous B. burgdorferi populations. In principle, cloning of a B. burgdorferi population is the appropriate method to analyze the polymorphism of individual molecules during infection. As a caveat, however, one has to envisage that during propagation of individual clones in vitro and in vivo independent genetic variations

Animals↗
PubMed1983

The relationship between three potential pathogens and pollution indicator organisms in Nova Scotian coastal waters.

Fifteen stations, in two estuaries, along the Northumberland Strait of Nova Scotia were examined between June and September 1981 for a relationship between the concentrations of commonly monitored fecal indicator bacteria and the potential pathogens Candida albicans, Pseudomonas aeruginosa, and Vibrio parahaemolyticus. Increased densities of these three organisms were usually associated with high densities of indicator bacteria. Whereas C. albicans and P. aeruginosa occur in human fecal wastes, V. parahaemolyticus is indigenous to the marine environment and positively responds to elevated nutrient levels in sewage. There is also some evidence that these bacteria survive as long or longer in marine waters than the common indicator bacteria. While membrane-filtration techniques for the enumeration of C. albicans and P. aeruginosa proved satisfactory, a V. parahaemolyticus membrane-filtration method lacked specificity and was supplemented by a most-probable-number method. In marine recreational and shellfish waters, these three organisms could complement fecal coliforms and fecal streptococci as indicators of human fecal contamination.

Candida albicans↗
PubMed1994

Antimicrobial susceptibility of nasopharyngeal isolates of potential pathogens recovered from infants before antibiotic therapy: implications for the management of otitis media.

Antimicrobial susceptibility was determined for strains of Streptococcus pneumoniae, nontypable Haemophilus influenzae and Moraxella catarrhalis recovered from the nasopharynxes of children followed from birth. The bacteria tested were the first potential pathogens isolated from each child before any treatment with antibiotics. Minimal inhibitory concentrations of commonly used oral antibiotics demonstrated the following overall rates of resistance for (1) S. pneumoniae: penicillin 1.2% (intermediate susceptibility 4.8%), trimethoprim-sulfamethoxazole 20%; (2) nontypable H. influenzae: ampicillin 32%, cefaclor 17%; (3) M. catarrhalis: ampicillin 90%, trimethoprim-sulfamethoxazole 19%. Antibiotic regimens used for treatment of otitis media may have to be evaluated in light of changing antibiotic susceptibilities.

Anti-Bacterial Agents↗
PubMedDate not supplied

[Effect of the ingestion of wheat bran on the fecal microbial flora of human donors and of recipient gnotoxenic mice, and on the barrier effects exerted by these flora against various potentially pathogenic microorganisms].

The effect of bran ingestion on the flora of the human digestive tract was studied using two methods: quantitative enumeration of various microbial populations of the faecal flora, and a demonstration of the antagonistic effect exerted by the faecal flora against various potentially pathogenic bacteria of the environment. Since this latter study cannot be effected in human subjects, we used a model constituted by axenic mice inoculated with patients' flora. Faecal samples from 3 human donors receiving bran-containing diets were obtained prior to treatment and 30 days thereafter. These faecal samples were inoculated into axenic mice fed a diet with or without bran. The dominant floras of the human donors, before and after bran ingestion, were highly similar. The faecal floras of the gnotoxenic mice resembled those of the donors and no change resulting from the presence of bran in the diet could be observed. The drastic or permissive barrier effects exerted in the gnotoxenic mice by the human donors against Clostridium perfringens, Staphylococcus aureus, Candida albicans and Pseudomonas aeruginosa were not modified by the presence of bran in the diet. The large variability between animals in the barrier effect against Clostridium difficile masked any possible role of the bran. Study of the transit of Bacillus spores in the digestive tract of various mouse groups showed the existence of differences according to the origin of the inoculated floras, but not according to the presence or absence of bran in the diet.

Animals↗
PubMed1999

High pathogenic potential of low-affinity autoantibodies in experimental autoimmune hemolytic anemia.

To assess the potency of low-affinity anti-red blood cell (RBC) autoantibodies in the induction of anemia, we generated an immunoglobulin (Ig)G2a class-switch variant of a 4C8 IgM anti-mouse RBC autoantibody, and compared its pathogenic potential with that of its IgM isotype and a high-affinity 34-3C IgG2a autoantibody. The RBC-binding activity of the 4C8 IgG2a variant was barely detectable, at least 1,000 times lower than that of its IgM isotype, having a high-binding avidity, and that of the 34-3C IgG2a monoclonal antibody (mAb). This low-affinity feature of the 4C8 mAb was consistent with the lack of detection of opsonized RBCs in the circulating blood from the 4C8 IgG2a-injected mice. However, the 4C8 IgG2a variant was highly pathogenic, as potent as its IgM isotype and the 34-3C IgG2a mAb, due to its capacity to interact with Fc receptors involved in erythrophagocytosis. In addition, our results indicated that the pentameric form of the low-affinity IgM isotype, by promoting the binding and agglutination of RBCs, is critical for its pathogenic activity. Demonstration of the remarkably high pathogenic potency of low-affinity autoantibodies, if combined with appropriate heavy chain effector functions, highlights the critical role of the Ig heavy chain constant regions, but the relatively minor role of autoantigen-binding affinities, in autoimmune hemolytic anemia.

Anemia, Hemolytic, Autoimmune↗
PubMed1995

Isolation of potentially pathogenic mycobacteria in the Finnish environment.

Atypical mycobacteria have become more common in clinical samples, and their reservoirs, known to be in the environment, are poorly identified. In the Finnish natural environment, mycobacteria can be cultivated from surface waters in a mean of 1500 CFU/l and from soil samples in a mean of 3.6 x 10(5) CFU/g dry weight. The majority of isolates are not pathogenic to man. Less than 10% of cultivable mycobacteria belong in species which are also found in human samples, either as infectious agents or as harmless colonizers of human epithelia. The two most important potentially pathogenic atypical mycobacteria in Finland, the Mycobacterium avium-intracellulare-scrofulaceum (MAIS) complex and M. malmoense, were detected in 40% and 4%, respectively, of the examined waters.

Finland↗
PubMedDate not supplied

[Primary amebic meningoencephalitis and the pathogenic potential of limax amoebas].

During the last two decades it has been proved that free amoeba of the Naegleria and Acanthamoeba (Hartmanella) genera, formerly considered as inocuous protozoa, are the etiological agent of a newly described morbid entity: primary amoebic meningoencephalitis. The clinical aspects of this disease, its clinical and laboratory diagnosis, the pathogenic potential of these amoebae, epidemiological data, prophylaxis and treatment, have promoted medical interest in this disease and in the possibility of a differential diagnosis with other meningoencephalitides.

Amebiasis↗
PubMed1995

Pathogenic potential of myeloblastosis-associated viruses.

Myeloblastosis-associated viruses (MAV) are replication competent avian retroviruses responsible for the induction of lymphoid leukosis, osteopetrosis, and nephroblastoma. Although both the route of infection and the strain of host used has been reported to be a critical factor in determining the outcome of viral infection, genetically distinct strains of MAV that exhibit a multiple pathogenic potential have been molcularly cloned. Osteopetrosis is a proliferative disease of the bones and nephroblastoma is a kidney cancer. Both diseases occur in chickens a few weeks after MAV injection. In both cases, the nature of the target cells and mechanisms of transformation induced by MAV remain to be established. Molecular cloning and sequencing of three MAV proviral genomes inducing both osteopetrosis and nephroblastoma or only nephroblastoma have allowed the identification of viral determinants essential for osteopetrosis induction. For the last decade we have focused our attention on the MAV-induced nephroblastoma because it is a unique animal model of the human Wilms' tumor. Studies that we have conducted to understand the molecular basis of MAV tumorigenic potential have led to the identification of viral sequences required for tumor induction and to the discovery of a new cellular gene (nov) likely to play a critical role in avian and human nephroblastoma development.

Amino Acid Sequence↗
PubMed2002

Evidence for the emergence of non-O1 and non-O139 Vibrio cholerae strains with pathogenic potential by exchange of O-antigen biosynthesis regions.

The novel epidemic strain Vibrio cholerae O139 Bengal originated from a seventh-pandemic O1 El Tor strain by antigenic shift resulting from homologous recombination-mediated exchange of O-antigen biosynthesis (wb*) clusters. Conservation of the genetic organization of wb* regions seen in other serogroups raised the possibility of the existence of pathogenic non-O1 and non-O139 V. cholerae strains that emerged by similar events. To test this hypothesis, 300 V. cholerae isolates of non-O1 and non-O139 serogroups were screened for the presence of virulence genes and an epidemic genetic background by DNA dot blotting, IS1004 fingerprinting, and restriction fragment length polymorphism (RFLP) analysis. We found four non-O1 strains (serogroups O27, O37, O53, and O65) with an O1 genetic backbone suggesting exchange of wb* clusters. DNA sequence analysis of the O37 wb* region revealed that a novel approximately 23.4-kb gene cluster had replaced all but the approximately 4.2-kb right junction of the 22-kb O1 wbe region. In sharp contrast to the backbones, the virulence regions of the four strains were quite heterogeneous; the O53 and O65 strains had the El Tor vibrio pathogenicity island (VPI) cluster, the O37 strain had the classical VPI cluster, and the O27 strain had a novel VPI cluster. Two of the four strains carried CTXphi; the O27 strain possessed a CTXphi with a recently reported immune specificity (rstR-4** allele) and a novel ctxB allele, and the O37 strain had an El Tor CTXphi (rstR(ET) allele) and novel ctxAB alleles. Although the O53 and O65 strains lacked the ctxAB genes, they carried a pre-CTXphi (i.e., rstR(cla)). Identification of non-O1 and non-O139 serogroups with pathogenic potential in epidemic genetic backgrounds means that attention should be paid to possible future epidemics caused by these serogroups and to the need for new, rapid vaccine development strategies.

Base Sequence↗
PubMed1980

Epidemiology of infection by nontuberculous Mycobacteria. III. Isolation of potentially pathogenic mycobacteria from aerosols.

Nontuberculous mycobacteria (21 isolates), biochemically similar to those that are recovered from humans, were recovered from rainwater and from natural river waters and their aerosols in the area of Richmond, Virginia. Field experiments have confirmed the existence of a natural mechanism for the transfer of significant numbers of mycobacteria from water to air. These findings support the hypothesis that aerosolization of potentially pathogenic mycobacteria from waters of the southeastern United States may be a major pathway for human infection.

Aerosols↗
PubMed1989

[Presence of potentially pathogenic bacteria and fungi in the cooling-lubricating emulsion used in the aluminum sheet rolling process].

Microbiological tests of aluminium rolling water-oil emulsion reveal high level of contamination: relatively anaerobic bacteria 10(6)-10(8) cells/ml, fungi and yeasts 10(3)-10(4) cells/ml, and also anaerobic bacteria Desulfovibrie sp. reducing sulfates to hydrogen sulfide. In emulsion samples there were present bacterial strains potentially dangerous to health, belonging to the family Enterobacteriaceae, Vibrionaceae, Pseudomonadaceae, Bacillaceae. The fungi and yeasts found in the emulsion were identified as: Aspergillus sp., Penicillium sp., Cladosporium sp., Cephalosporium sp., Candida sp. The emulsion sprayed in aerosol in air of the mill was the infecting source for the workers. The emulsion was protected by a biocid and thus the growth of potentially pathogenic microorganisms was inhibited.

Aluminum↗
PubMedDate not supplied

Sequence analysis of the hemagglutinin gene of H9N2 Korean avian influenza viruses and assessment of the pathogenic potential of isolate MS96.

Sequence analysis of the hemagglutinin (HA) gene of five Korean H9N2 avian influenza virus (AIV) isolates showed that these viruses were closely related and possibly came from the same source. Phylogenetic analysis of the HA1 subunit of H9 subtype isolates revealed that Korean AIV isolates were different from isolates from the poultry markets in Hong Kong in 1997. None of the Korean AIVs had multiple basic amino acids at the HA cleavage site that confer high pathogenicity to some H5 and H7 AIVs. Phylogenetic analysis of the nucleoprotein and matrix gene demonstrated that Korean isolates cluster with Eurasian origin AIVs. The pathogenic potential of one of the isolates (MS96) was assessed after several passages in 14-day-old embryonated chicken eggs (ECE). Fourteen-day-old ECE derivatives of MS96 showed increased HA titer and embryo mortality in eggs; this was apparent after the third passage in 14-day-old ECE. Sequence analysis of the cleavage site of MS96 after the third and tenth passages in 14-day-old ECE revealed no changes in the amino acid sequence. The pathogenicity of MS96 after the tenth passage in 14-day-old eggs (MS96p10(ECE14)) was tested with 4-wk-old specific-pathogen-free chickens. The 14-day-old derivative, MS96p10(ECE14), showed wider tissue tropism and induced more severe clinical signs than the parent virus. Furthermore, after intranasal inoculation of 86-wk-old broiler breeders and 30-wk-old layers, the MS96p10(ECE14) derivative induced more severe signs of depression than the parent virus as well as a transient drop in egg production.

Amino Acid Sequence↗
PubMed1997

Suppression of the growth of six potentially-pathogenic mycobacteria by beta-lactam/beta-lactamase-inhibitors.

Drug-resistant tuberculosis and opportunistic infections by mycobacteria in immunocompromised subjects are not readily controlled with the antimycobacterial drugs now available. beta-Lactam antibiotics, the most widely used antibacterial agents, are ineffective against mycobacteria since they synthesize beta-lactamases. The beta-lactam/beta-lactamase-inhibitor combinations are used at present to treat infections caused by other beta-lactamase-positive organisms. Six potentially-pathogenic mycobacteria: Mycobacterium avium, M. chelonei, M. haemophilum, M. microti, M. scrofulaceum and M. simiae, were cultured in 7H9 medium (containing Tween 80 and albumin, dextrose, catalase) at 37 degrees C for 10-14 days, with or without various concentrations (2-100 micrograms/ml) of ampicillin/sulbactam, amoxicillin/clavulanate and piperacillin/tazobactam. More than 50-80% inhibition of the mycobacterial growth was observed at drug levels of 40-100 micrograms/ml in the medium; the drugs were active even when the detergent (Tween 80) was omitted. Against four of the mycobacteria, ampicillin/sulbactam proved to be the most active. The beta-lactam/beta-lactamase-inhibitor combinations may be of use as rational therapeutic agents against mycobacterial infections.

Anti-Bacterial Agents↗
PubMed2000

[Signal identification of potentially pathogenous Yersinia].

A four-tube method with diagnostic nutrient media is proposed for differentiating between pathogenic and apathogenic Yersinia. Yersinia cultures are detected by inoculating typical or suspected colonies from solid media to media with lactose, glucose, urea, and indicators. Subsequent culturing in three other media (with sucrose and sorbitol, with esculin, rhamnose, and salicin, and with pyrasinamide) and the use of appropriate indicators help detect potentially pathogenous pseudotuberculous and enteric Yersinia of 1B, 2, 3, and 5 biovars from apathogenic species and variants. The method is simple, rapid, economic, reliable, and is recommended for clinical laboratory diagnosis.

Bacterial Typing Techniques↗
PubMed2004

Rare occurrence of heterotrophic bacteria with pathogenic potential in potable water.

Since the discovery of Legionella pneumophila, an opportunistic pathogen that is indigenous to water, microbiologists have speculated that there may be other opportunistic pathogens among the numerous heterotrophic bacteria found in potable water. The US Environmental Protection Agency (USEPA) developed a series of rapid in vitro assays to assess the virulence potential of large numbers of bacteria from potable water to possibly identify currently unknown pathogens. Results of surveys of potable water from several distribution systems using these tests showed that only 50 of the approximately 10,000 bacterial colonies expressed one or more virulence characteristics. In another study, 45 potable water isolates that expressed multiple virulence factors were tested for pathogenicity in immunocompromised mice. None of the isolates infected mice that were compromised either by treatment with carrageenan (CG), to induce susceptibility to facultative intracellular pathogens, or by cyclophosphamide (CY), to induce susceptibility to extracellular pathogens. These results indicate that there are very few potential pathogens in potable water and that the currently developed in vitro virulence screening tests give an overestimation of the numbers of heterotrophic bacteria that may be pathogens. Current efforts are focused on using the animal models to screen concentrated samples of waters known to contain large numbers of heterotrophic bacteria and newly discovered Legionella-like organisms that parasitize amoebae.

Animals↗
PubMed1998

Smokeless tobacco extracts activate complement in vitro: a potential pathogenic mechanism for initiating inflammation of the oral mucosa.

The use of smokeless tobacco has been linked to an increased incidence of inflammation of the buccal and gingival mucosa. However, the mechanisms by which smokeless tobacco initiates inflammation are not well understood. The complement cascade is a ubiquitous source of proinflammatory molecules and can be activated rapidly by a wide variety of agents. Therefore, the effect of smokeless tobacco on complement was investigated as a potential pathogenic mechanism for triggering inflammation of the oral mucosa. Aqueous extracts of loose leaf chewing tobacco (1S1), dry snuff (1S2), and moist snuff (1S3), added to normal human serum, depleted complement hemolytic activity in a dose-dependent manner. Experiments utilizing sera deficient in one specific complement component indicated that the smokeless tobacco-induced depletion of hemolytic activity was due largely to consumption of C3. Furthermore, assays designed to test the activity of the alternative pathway of complement clearly showed that all three extracts depleted the hemolytic activity of this pathway. Finally, all three smokeless tobacco extracts activated the alternative pathway since significantly elevated levels of the cleavage fragments iC3b and Bb were detected in extract-treated serum. High quantities of the classical pathway cleavage fragment C4d also were detected in serum treated with moist snuff (1S3). The results clearly demonstrate that smokeless tobacco extracts activate the alternative pathway and also suggest some measure of classical pathway activation. Activation of complement by smokeless tobacco may be a mechanism for initiating inflammation of the oral mucosa.

Complement Activation↗
PubMed1991

Intestinal bacteria of newborn Ethiopian infants in relation to antibiotic treatment and colonisation by potentially pathogenic gram-negative bacteria.

The aerobic and anaerobic intestinal microflora of 60 newborn infants in Addis Ababa was studied. As opposed to earlier published studies from Stockholm, there were no consistent changes of the microflora attributable to antibiotic treatment. The reason why antimicrobial agents caused quantitatively smaller changes of the intestinal microflora in newborn infants in Addis Ababa than in Stockholm is not known, but may be due to antimicrobial inactivation, or marked, continuous ingestion of bacteria. Colonisation by potentially pathogenic gram-negative bacteria was coupled to a low isolation rate of bifidobacterium, but not of lactobacillus. This is consistent with the hypothesis that bifidobacterium might convey some kind of resistance to colonisation by and overgrowth of gram-negative bacteria in newborn infants. Similar results have previously been obtained in Stockholm. In comparison to 45 healthy infants in Stockholm, the Ethiopian infants had more enterococcus and lactobacillus and less staphylococcus and bacteroides during the first 2 weeks of life. After that time, the only difference was more frequent colonisation by lactobacillus in Addis Ababa.

Anti-Bacterial Agents↗