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At least 757 records · Page 42Linked to original sources
PubMed2004

Antimicrobial and pore-forming peptides of free-living and potentially highly pathogenic Naegleria fowleri are released from the same precursor molecule.

The pore-forming polypeptides of Naegleria fowleri, naegleriapores A and B, are processed from separate multipeptide precursor structures. According to their transcripts, each precursor molecule appears to contain additional naegleriapore-like polypeptides, all of which share a structural motif of six invariant cysteine residues within their amino acid sequence. To identify the putative pronaegleriapore-derived peptides at the protein level, amoebic extracts were screened for small cysteine-rich polypeptides by fluorescently labeling their cysteine residues. Three novel naegleriapore isoforms derived from the precursor molecule of naegleriapore B were identified. Two of the isoforms were purified to homogeneity and tested for their biological activity. The pore-forming activity of the novel peptides was remarkably lower than that of the originally isolated naegleriapores, but both peptides killed bacteria by permeabilizing their cytoplasmic membranes. Collectively, these results indicate that naegleriapore isoforms with antibacterial and pore-forming activity are proteolytically released from the same precursor protein, presumably to generate a phylogenetically ancient complementary antimicrobial arsenal.

Amino Acid Motifs↗
PubMed2003

Screening of Bifidobacterium strains isolated from human faeces for antagonistic activities against potentially bacterial pathogens.

As probiotic bacteria, strains belonging to the genus Bifidobacterium colonise the gastro-intestinal tract of humans and animals at the time of birth, and they are found in young as well as in adult individuals in great numbers. Moreover, they can interact with the development of enteric infections by the production of antimicrobial metabolites. In this work 281 strains of bifidobacteria were anaerobically isolated from human faecal samples, supplied by volunteers of different ages (youngs, adults, elders), and preliminarly described by microscopic observation. All strains were screened by the fructose 6-phosphate phosphoketolase (F6PPK) test in order to confirm their classification within the genus Bifidobacterium. Selected strains were used to evaluate their antagonistic activities against Escherichia coli, Salmonella thyphimurium, Staphylococcus lentus, Enterococcus faecalis, Acinetobacter calcoaceticus, Sphingomonas paucimobilis, Listeria monocytogenes, Yersinia enterocolitica, Bacillus cereus, Clostridium sporogenes. Experiments were performed in vitro by different methods based on the observation of growth inhibition in Petri dishes. The strains that showed the highest inhibiting activities were compared by SDS-PAGE for total cell proteins, using type strains of human origin as references. Representative isolates were metabolically characterised by the BIOLOG system; a specific database was created with strains obtained from our collection and a statistical evaluation for metabolic patterns was carried out.

Adolescent↗
PubMed2002

Complement activation selectively potentiates the pathogenicity of the IgG2b and IgG3 isotypes of a high affinity anti-erythrocyte autoantibody.

By generating four IgG isotype-switch variants of the high affinity 34-3C anti-erythrocyte autoantibody, and comparing them to the IgG variants of the low affinity 4C8 anti-erythrocyte autoantibody that we have previously studied, we evaluated in this study how high affinity binding to erythrocytes influences the pathogenicity of each IgG isotype in relation to the respective contributions of Fcgamma receptor (FcgammaR) and complement. The 34-3C autoantibody opsonizing extensively circulating erythrocytes efficiently activated complement in vivo (IgG2a = IgG2b > IgG3), except for the IgG1 isotype, while the 4C8 IgG autoantibody failed to activate complement. The pathogenicity of the 34-3C autoantibody of IgG2b and IgG3 isotypes was dramatically higher (>200-fold) than that of the corresponding isotypes of the 4C8 antibody. This enhanced activity was highly (IgG2b) or totally (IgG3) dependent on complement. In contrast, erythrocyte-binding affinities only played a minor role in in vivo hemolytic activities of the IgG1 and IgG2a isotypes of 34-3C and 4C8 antibodies, where complement was not or only partially involved, respectively. The remarkably different capacities of four different IgG isotypes of low and high affinity anti-erythrocyte autoantibodies to activate FcgammaR-bearing effector cells and complement in vivo demonstrate the role of autoantibody affinity maturation and of IgG isotype switching in autoantibody-mediated pathology.

Anemia, Hemolytic, Autoimmune↗
PubMed2001

Overexpression of Pti5 in tomato potentiates pathogen-induced defense gene expression and enhances disease resistance to Pseudomonas syringae pv. tomato.

The tomato Pti5 gene encodes a pathogen-inducible ethylene response element-binding protein-like transcription factor that interacts with the disease resistance gene product Pto. Overexpression of Pti5 or Pti5-VP16, a translational fusion with a constitutive transcriptional activation domain, in tomato enhanced resistance to Pseudomonas syringae pv. tomato. Constitutive expression of Pti5 or Pti5-VP16 did not affect the basal level of pathogenesis-related gene expression, but it accelerated pathogen-induced expression of GluB and Catalase. The results demonstrate a positive role of Pti5 in defense gene regulation and disease resistance and suggest that a pathogen-activated posttranscriptional regulatory step is necessary for the pathogen induction of the defense gene expression.

DNA-Binding Proteins↗
PubMed1996

Neonatal enterococcal bacteremia: an increasingly frequent event with potentially untreatable pathogens.

BACKGROUND: Enterococci can cause serious infections in the newborn. The increased number of these infections since the late 1970s and the increased isolation of organisms resistant to many commonly used antimicrobials prompted review of our experience with enterococcal bacteremia in the neonatal intensive care unit. This review was aimed at defining the character of illness of newborns who had these infections during a 20-year period. METHODS: This was a retrospective review of the medical records of newborns with enterococci isolated from blood. RESULTS: Between January, 1974, and December, 1993, 138 episodes of enterococcal bacteremia occurred in newborns hospitalized in the neonatal intensive care unit. Thirty-four episodes occurred during the first decade and 104 episodes during the second decade. One hundred of the 138 episodes were reviewed. In 64% of these episodes other microorganisms were also isolated from blood. Comparison of clinical characteristics associated with these episodes in the first and second decade demonstrated that episodes occurring in the more recent decade occurred in older infants (mean age of onset, 44.7 vs. 16.1 days; episodes occurring after 14 days, 73% vs. 41%). Common characteristics associated with enterococcal bacteremia included the presence of a central vascular catheter (77%), necrotizing enterocolitis (33%) and abdominal distension (21%). Vancomycin-resistant enterococci caused bacteremia in 6 infants and caused illnesses indistinguishable from those caused by susceptible organisms. CONCLUSIONS: In the more recent decade there were three times the number of episodes of enterococcal bacteremia in our neonatal intensive care unit than there were in the previous decade. The characteristics associated with these infections were similar to those occurring with other nosocomial bacterial infections in the neonate and did not change during the period reviewed. Most recent episodes occurred as part of polymicrobial infections in newborns hospitalized for more than 1 month. Infections caused by vancomycin-resistant enterococci occurred in older patients but were clinically indistinguishable from infections caused by sensitive organisms.

Age Factors↗
PubMed1995

Mycobacterium branderi sp. nov., a new potential human pathogen.

A number of mycobacterial strains with similar growth characteristics, metabolic properties, and lipid compositions, which were previously placed in the Helsinki group (E. Brander, E. Jantzen, R. Huttunen, A. Juntunen, and M.-L. Katila, J. Clin. Microbiol. 30:1972-1975, 1992), were characterized by performing 16S rRNA gene sequencing. Of the 14 strains studied, 9 had a unique, previously undescribed sequence in the variable region of 16S rRNA. These nine strains, all of which were isolated from respiratory tract specimens, were nonpigmented and grew at 25 degrees C to 45 degrees C, reaching full colony size after 2 to 3 weeks. They produced arylsulfatase, nicotinamidase, and pyrazinamidase and were negative for Tween 80 hydrolysis, catalase, urease, and nitrate reductase activities, and niacin. Their glycolipid patterns were identical. A mycolic acid analysis performed by using thin-layer chromatography showed that these organisms contained alpha-mycolates, ketomycolates, and carboxy mycolates. Gas-liquid chromatography revealed that 2-eicosanol was the major alcohol and hexacosanoic acid was the major mycolic acid cleavage product. On the basis of their growth, biochemical, and lipid characteristics and their unique 16S rRNA sequence, we propose that these organisms should be assigned to a new species, Mycobacterium branderi. Comparative 16S rRNA sequencing revealed that this new species is closely related to Mycobacterium celatum, Mycobacterium cookii, and Mycobacterium xenopi. Strains 52157T (T = type strain) and 43548 have been deposited in the American Type Culture Collection as strains ATCC 51789 and ATCC 51788, respectively.

Antibiotics, Antitubercular↗
PubMed1989

Experimental infections by Bacteroides gingivalis in non-immunized and immunized rabbits.

The interactions between Bacteroides gingivalis and systemic antibodies were studied in tissue cages implanted in the backs of New Zealand white rabbits. Infectivity was evaluated according to clinical signs and to leukocyte and bacterial counts in material aspirated from the tissue cages. Pre- and post-inoculation antibody levels to sonicated whole bacterial cells were determined by enzyme-linked immunosorbent and agar immunodiffusion assays. Rabbits immunized against B. gingivalis and then challenged with pure cultures of B. gingivalis revealed complete elimination or markedly lower postinoculation bacterial counts and considerably weaker tissue reactions than non-immunized animals. B. gingivalis co-inoculated with Actinobacillus actinomycetemcomitans caused significantly more severe infections than observed in monoinfected animals. The present results suggest that the immune system acting through systemic antibodies and/or cellular mechanisms may modulate the pathogenic potential of infecting periodontal pathogens.

Animals↗
PubMed2005

Fungal pathogen reduces potential for malaria transmission.

Using a rodent malaria model, we found that exposure to surfaces treated with fungal entomopathogens following an infectious blood meal reduced the number of mosquitoes able to transmit malaria by a factor of about 80. Fungal infection, achieved through contact with both solid surfaces and netting for durations well within the typical post-feed resting periods, was sufficient to cause >90% mortality. Daily mortality rates escalated dramatically around the time of sporozoite maturation, and infected mosquitoes showed reduced propensity to blood feed. Residual sprays of fungal biopesticides might replace or supplement chemical insecticides for malaria control, particularly in areas of high insecticide resistance.

Animals↗
PubMed2005

Induction of {beta}-defensin resistance in the oral anaerobe Porphyromonas gingivalis.

Induction of resistance of oral anaerobes to the effects of human beta-defensin 1 (hbetaD-1) to hbetaD-4 was investigated by pretreating cells with either sublethal levels of defensins or environmental factors, followed by a challenge with lethal levels of defensins. Cultures of Porphyromonas gingivalis were (i) pretreated with defensins at 1 ng/ml, (ii) heated to 42 degrees C (heat stress), (iii) exposed to normal atmosphere (oxidative stress), or (iv) exposed to 1 mM hydrogen peroxide (peroxide stress). Samples (10 microl) were distributed among the wells of sterile 384-well plates containing hbetaD-1 to -4 (100 microg/ml). Plates were incubated at 37 degrees C for 36 h in an anaerobe chamber. Growth inhibition was determined by a system that measures the total nucleic acid of a sample with a DNA binding dye. The MICs of the four defensins for P. gingivalis were 3 to 12 microg/ml. We found that sublethal levels of the defensins and heat and peroxide stress, but not oxidative stress, induced resistance to 100 microg of defensin per ml in P. gingivalis. Resistance induced by sublethal levels of hbetaD-2 lasted 90 min, and the resistance induced by each defensin was effective against the other three. Multiple strains exposed to hbetaD-2 all evidenced resistance induction. Defensin resistance is vital to the pathogenic potential of several human pathogens. This is the first report describing the induction of defensin resistance in the oral periodontal pathogen P. gingivalis. Such resistance may have an effect on the ability of oral pathogens to persist in the mouth and to withstand innate human immunity.

Anaerobiosis↗
PubMed1991

Pathogenic properties of Edwardsiella species.

The pathogenic characteristics of 35 Edwardsiella strains from clinical and environmental sources were investigated. Overall, most Edwardsiella tarda strains were invasive in HEp-2 cell monolayers, produced a cell-associated hemolysin and siderophores, and bound Congo red; many strains also expressed mannose-resistant hemagglutination against guinea pig erythrocytes. Edwardsiella hoshinae strains bound Congo red and were variable in their invasive and hemolytic capabilities while Edwardsiella ictaluri strains did not produce either factor; neither E. hoshinae nor E. ictaluri expressed mannose-resistant hemagglutination nor elaborated siderophores under the tested conditions. Selected strains of each species tested for mouse lethality indicated strain variability in pathogenic potential, with E. tarda strains being the most virulent; 50% lethal doses in individual strains did not correlate with plasmid content, chemotactic motility, serum resistance, or expression of selected enzyme activities. The results suggest some potential important differences in pathogenic properties that may help explain their environmental distribution and ability to cause disease in humans.

Animals↗
PubMed2004

Variability of germinative potential among pathogenic species of Aspergillus.

The objective of our study was to evaluate parameters influencing the germination of Aspergillus conidia. Inoculum concentration and age significantly influenced germination. Different incubation temperatures revealed significant differences among Aspergillus species. The internal human milieu provides the ideal conditions for the development of invasive disease by Aspergillus fumigatus but restricts invasion by Aspergillus flavus and Aspergillus niger.

Aspergillus↗
PubMed2005

Potential secondary pathogenic role for bovine herpesvirus 4.

Bovine herpesvirus 4 (BoHV-4) is a gammaherpesvirus with no clear disease association. Previous studies have demonstrated that macrophages can harbor persistent BoHV-4. We found that the addition of prostaglandin E2 (PGE2) to bovine macrophage cells persistently infected with BoHV-4 increases viral replication. Because opportunistic infection can increase PGE2 production, we propose a link between opportunistic infection, PGE2 production, and BoHV-4 replication.

Animals↗
PubMed2002

Potential viral pathogenic mechanism for new variant inflammatory bowel disease.

AIMS: A new form of inflammatory bowel disease (ileocolonic lymphonodular hyperplasia) has been described in a cohort of children with developmental disorder. This study investigates the presence of persistent measles virus in the intestinal tissue of these patients (new variant inflammatory bowel disease) and a series of controls by molecular analysis. METHODS: Formalin fixed, paraffin wax embedded and fresh frozen biopsies from the terminal ileum were examined from affected children and histological normal controls. The measles virus Fusion (F) and Haemagglutinin (H) genes were detected by TaqMan reverse transcription polymerase chain reaction (RT-PCR) and the Nucleocapsid (N) gene by RT in situ PCR. Localisation of the mRNA signal was performed using a specific follicular dendritic cell antibody. RESULTS: Seventy five of 91 patients with a histologically confirmed diagnosis of ileal lymphonodular hyperplasia and enterocolitis were positive for measles virus in their intestinal tissue compared with five of 70 control patients. Measles virus was identified within the follicular dendritic cells and some lymphocytes in foci of reactive follicular hyperplasia. The copy number of measles virus ranged from one to 300,00 copies/ng total RNA. CONCLUSIONS: The data confirm an association between the presence of measles virus and gut pathology in children with developmental disorder.

Adolescent↗