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PubMed1990

Studies on the lipopolysaccharide of a virulent and an avirulent strain of Vibrio vulnificus.

Vibrio vulnificus is a marine bacterium associated with both primary septicemias and wound infections in humans. The lipopolysaccharides of a virulent and an avirulent strain of Vibrio vulnificus were compared with respect to their chemical constituents and electrophoretic characteristics. 2-Keto-3-deoxyoctonic acid, a normal constituent of the lipopolysaccharide of typical Enterobacteriaceae, was not found in the lipopolysaccharide of either strain. Hexadecenoate (C16:1) was the predominant fatty acid of the lipid A moiety of the lipopolysaccharides and of the membrane phospholipids of both strains. Hydroxy fatty acids composed 44% of the total fatty acids of the lipid A of the avirulent and 40% of those in the virulent strain. In addition, odd-numbered fatty acids were detected in both lipopolysaccharides. The electrophoretic profile was similar for both strains, but demonstrated no "ladder-like" pattern characteristic of "smooth" lipopolysaccharides. The result of this study showed no significant differences between the lipopolysaccharides of the virulent and avirulent strains of Vibrio vulnificus. The possible role for lipopolysaccharide in pathogenesis of Vibrio vulnificus infections is discussed.

Antigens, Bacterial↗
PubMed2005

GeneChip expression analysis of the VqsR regulon of Pseudomonas aeruginosa TB.

Two interlinked quorum sensing circuits, las and rhl, which control pathogenesis of Pseudomonas aeruginosa are further modulated by numerous regulators, including VqsR (virulence and quorum sensing regulator). High-density oligonucleotide microarrays were used to compare the global expression profile of a wild-type and VqsR mutant in ABC minimal medium. The expression of a large group of metabolic genes, ECF sigma factors as well as of many quorum-sensing genes previously not assigned to VqsR-regulon was found to be affected by the disruption of vqsR.

Culture Media↗
PubMed1992

The adherence of verocytotoxin-producing Escherichia coli to rabbit intestinal cells.

Verocytotoxin-producing Escherichia coli (VTEC) have been recognised recently as an important cause of human disease. The adherence of VTEC to rabbit intestinal tract and the relationship between adherence and other virulence traits were studied. Twenty clinical isolates of VTEC (O157:H7 and other serotypes) and a control, commensal E. coli strain, were examined. Bacteria were evaluated for the presence of surface fimbriae, plasmid profile and hybridisation with a 3.4 kb DNA probe derived from the 60-MDa plasmid of such strains. Adherence was determined by electronmicroscopy and quantitatively with radio-labelled bacteria. Of the VTEC strains, 12 (60%) had surface fimbriae; all O157:H7 and 10 (70%) of 14 of the non-O157:H7 strains hybridised with the probe. No isolate was negative for both of these virulence traits and there was no correlation between their presence. The plasmid profiles varied among the strains, with no correlation to virulence traits. The adherence of VTEC strains differed significantly, ranging from 0.3 to 34.0 bacteria/intestinal cell. The mean adherence of fimbriate strains was greater than that of non-fimbriate strains (3.9 versus 2.7 bacteria/cell), although marked variability was noted in both groups. This study showed that VTEC strains differed markedly in their adherence capability and that neither the presence of fimbriae nor hybridisation with the 3.4-kb probe was essential for adherence. Several distinct mechanisms probably play a role in VTEC adherence.

Animals↗
PubMed1991

The Yersinia pestis V antigen is a regulatory protein necessary for Ca2(+)-dependent growth and maximal expression of low-Ca2+ response virulence genes.

The low-Ca2+ response is a multicomponent virulence regulon of the human-pathogenic yersiniae in which 12 known virulence genes are coordinately regulated in response to environmental cues of temperature, Ca2+, and nucleotides such as ATP. Yersinial growth also is regulated, with full growth yield being permitted at 37 degrees C only if Ca2+ or a nucleotide is present. In this study, we constructed and characterized a mutant Yersinia pestis specifically defective in the gene encoding the V antigen, one of the virulence genes of the low-Ca2+ response. An in-frame internal deletion-insertion mutation was made by removing bases 51 through 645 of lcrV and inserting 61 new bases. The altered lcrV was introduced into the low-Ca2+ response plasmid in Y. pestis by allelic exchange, and the resulting mutant was characterized for its two-dimensional protein profiles, growth, expression of an operon fusion to another low-Ca2+ response virulence operon, and virulence in mice. The mutant had lost its Ca2+ and nucleotide requirement for growth, showed diminished expression of Ca2(+)-and nucleotide-regulated virulence genes, and was avirulent in mice. The mutation could be complemented with respect to the growth property by supplying native V antigen operon sequences in trans in high copy number (on pBR322). Partial complementation of the growth defect and almost complete complementation of the virulence defect were seen with a lower-copy-number complementing replicon (a pACYC184 derivative). The data are consistent with the interpretation that V antigen is bifunctional, with a role in regulating growth and expression of low-Ca2+ response virulence genes in addition to its putative role as a secreted virulence protein.

Antigens, Bacterial↗
PubMed2004

Biochemical and virulence characterization of viable but nonculturable cells of Vibrio parahaemolyticus.

Vibrio parahaemolyticus is a common foodborne pathogen frequently causing outbreaks in summer. Maintenance of virulence by the viable but nonculturable (VBNC) state of this pathogen would allow its threat to human health to persist. This study reports on the change in virulence and concomitant changes in activity of two enzymes and fatty acid profiles when V. parahaemolyticus ST550 entered the VBNC state in the modified Morita mineral salt-0.5% NaCl medium incubated at 4 degrees C. The major change in fatty acid composition occurred in the first week, with a rapid increase in C15:0 fatty acid and saturated/unsaturated ratio while a rapid decrease in C16:1 was observed. The activity level of the inducible protective enzyme superoxide dismutase became undetectable in the VBNC state, whereas that of constitutive glucose-6-phosphate dehydrogenase did not change in either the exponential phase or the VBNC state. Cytotoxicity against HEp-2 cells and a suckling mouse assay showed that virulence was lowered in the VBNC state compared with exponential-phase cells. Longer incubation times were required by the VBNC cells to achieve the same level of virulence as seen in exponential-phase cells. Culturable cells were recovered on selective agar medium from the VBNC cultures injected into suckling mice, probably as the result of in vivo resuscitation. Results of this study add to our understanding of the biochemical and physiological changes that have not been reported when V. parahaemolyticus enters into the VBNC state.

Animals↗
PubMed2000

High protease activity of Chryseobacterium indologenes isolates associated with invasive infection.

In order to understand virulence factors of Chryseobacterium indologenes isolates associated with invasive infection, enzymatic activities and cellular fatty acid profiles of 42 isolates recovered at National Taiwan University Hospital from January 1994 to December 1996 were studied. Among them, 12 blood isolates were considered as invasive and 30 (recovered from urine, sputa, infected burn wounds, and catheter tips) were noninvasive. All isolates showed strong activities of alkaline phosphatase, acid phosphatase, naphthol-AS-BI-phosphohydrolase, and N-acetyl-beta-glucosaminidase, and had no activities for alpha-galactosidase, beta-galactosidase, beta-glucuronidase, alpha-mannosidase, and alpha-fucosidase. The activities of other enzymes were variable. Thirty-two isolates (76%) had varying degrees of protease activity. Two profiles (profiles I and II) of cellular fatty acids of the isolates were found and profile I predominated. There was no significant difference of distribution of cellular fatty acid profiles and activities of enzymes between invasive and noninvasive isolates, except protease activity which was significantly higher in invasive isolates than that in noninvasive isolates. Protease activity may play an important role in virulence on invasive infections caused by C. indologenes.

Endopeptidases↗
PubMed1984

Some characteristics of four attenuated vaccine virus strains and a virulent strain of Aujeszky's disease virus.

In the present study four attenuated virus strains, used as vaccines, and a virulent strain of Aujeszky's disease virus (ADV) were compared with respect to their virulence in mice, their ability to induce virus-specified thymidine kinase (TK) in infected cells, and their cleavage profiles of viral DNA's after treatment with the restriction endonuclease KpnI. The survival time of mice inoculated with the B-KAL or the virulent NIA-3 strain was comparable, whereas the Bartha and BUK strains required significantly longer periods to kill mice. Mice were resistant to the MK-25 strain of ADV. The strains were assayed for TK phenotype by plaque autoradiography after 3H-thymidine labelling of infected cells. MK-25 proved to be the only strain defective in induction of TK in pig kidney cells. Restriction endonuclease analysis of viral DNA's revealed that each vaccine strain showed a characteristic fragment pattern that could easily be differentiated from that of other vaccine and field strains of ADV. The present results demonstrate that the mouse virulence test and the TK assay detect differences in biological properties of ADV strains, but that restriction endonuclease analysis is required for unambiguous identification of vaccine and field strains of ADV.

Animals↗
PubMed2006

Development and validation of an oligonucleotide microarray for detection of multiple virulence and antimicrobial resistance genes in Escherichia coli.

An oligonucleotide microarray detecting 189 Escherichia coli virulence genes or markers and 30 antimicrobial resistance genes was designed and validated using DNA from known reference strains. This microarray was confirmed to be a powerful diagnostic tool for monitoring emerging E. coli pathotypes and antimicrobial resistance, as well as for environmental, epidemiological, and phylogenetic studies including the evaluation of genome plasticity.

Animals↗
PubMed1999

Role of the 25 kDa major outer membrane protein of Legionella pneumophila in attachment to U-937 cells and its potential as a virulence factor for chick embryos.

The gene encoding the 25 kDa major outer membrane protein (MOMP) of Legionella pneumophila was transformed into Escherichia coli JM 83 and the resultant E. coli LP 116 clone expressed the Legionella-MOMP. Compared with the parent E. coli strain, the clone showed a fivefold increase in opsonin-independent binding to U-937 cells. Furthermore, this gene was incorporated by electroporation into a low virulence derivative of Leg. pneumophila which showed reduced expression of the MOMP but enhanced expression of a 31 kDa protein in the OMP profile. After electroporation, the attenuated strain showed an increased expression of the MOMP while the 31 kDa protein was eliminated and virulence for the chick embryo was re-established. The use of a monoclonal antibody specific for the MOMP abolished virulence and adherence. These studies suggest that the 25 kDa MOMP of Leg. pneumophila serves as an adhesive molecule for host cells and that this protein plays a major role in the virulence of the organism for the chick embryo.

Animals↗
PubMed1992

Cell surface characteristics and virulence in mice of Pasteurella multocida.

The virulence of three avian strains of Pasteurella multocida was evaluated in mice. Strains P-1059I (serotype A:3) and its uncapsulated variant P-1059B and strain 2723 (serotype A:16) were compared. Capsular material thickness after polycationic ferritin labelling of dextrose starch agar (DSA)-grown P. multocida was shown to vary with the strain and was not always related to virulence. Addition of alpha,alpha' bipyridyl (BIP) (160 microM) to the culture medium did not affect capsule production but increased virulence of strains P-1059B and 2723. None of the strains tested showed dermonecrotic activity. Using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), outer membrane protein (OMP) profiles indicated for strains P-1059I and P-1059B three proteins of 30, 35, and 38 KDa with the 30 KDa protein being the major one. Strain 2723 showed the same OMP profile but the 38 KDa protein was the major one. DSA + BIP-grown strains showed the same OMP profiles. Whole cell profiles were similar for all strains tested. However, addition of BIP to the culture media increased the virulence of strains P-1059B and 2723 and for all strains a 39 KDa protein was induced by the iron chelator. The results indicate that encapsulation may be important for virulence, but other surface components such as OMPs may be required as well.

Animals↗
PubMed2004

Disease outcome and cytokine responses in cats immunized with an avirulent feline infectious peritonitis virus (FIPV)-UCD1 and challenge-exposed with virulent FIPV-UCD8.

Eight cats were immunized with an avirulent strain of feline infectious peritonitis virus (FIPV)-UCD1, then challenge-exposed to a highly virulent cat passaged strain (FIPV-UCD8). Th1 and Th2 cytokine profiles in the peripheral blood mononuclear cells (PBMCs) were measured throughout in the experiment. No clinical signs of FIP were evident in the experimental cats after immunization. After challenge, the immunized cats demonstrated one of four clinical outcomes: (1) classical effusive FIP; (2) accelerated FIP; (3) non-effusive FIP, or (4) resistance to challenge. Only minor cytokine changes were observed following immunization, however, several cytokine changes occurred following challenge-exposure. The most noteworthy changes were in tumor necrosis factor-alpha (TNF-alpha) and interferon gamma (IFN-gamma) levels. Our preliminary findings suggest that immunity against FIP is associated with TNF-alpha and IFN-gamma response imbalance, with high TNF-alpha/low IFN-gamma mRNA responses favouring disease and low TNF-alpha/high IFN-gamma mRNA responses being indicative of immunity.

Animals↗
PubMed2006

Bird flu, influenza and 1918: the case for mutant Avian tuberculosis.

Influenza is Italian for "influence", Latin: influentia. It used to be thought that the disease was caused by a bad influence from the heavens. Influenza was called a virus long, long before it was proven to be one. In 2005, an article in the New England Journal of Medicine estimated that a recurrence of the 1918 influenza epidemic could kill between 180 million and 360 million people worldwide. A large part of the current bird-flu hysteria is fostered by a distrust among the lay and scientific community regarding the actual state of our knowledge regarding the bird flu or H5N1 and the killer "Influenza" Pandemic of 1918 that it is compared to. And this distrust is not completely unfounded. Traditionally, "flu" does not kill. Experts, including Peter Palese of the Mount School of Medicine in Manhattan, remind us that even in 1992, millions in China already had antibodies to H5N1, meaning that they had contracted it and that their immune system had little trouble fending it off. Dr. Andrew Noymer and Michel Garenne, UC Berkely demographers, reported in 2000 convincing statistics showing that undetected tuberculosis may have been the real killer in the 1918 flu epidemic. Aware of recent attempts to isolate the "Influenza virus" on human cadavers and their specimens, Noymer and Garenne summed that: "Frustratingly, these findings have not answered the question why the 1918 virus was so virulent, nor do they offer an explanation for the unusual age profile of deaths". Bird flu would certainly be diagnosed in the hospital today as Acute Respiratory Distress Syndrome (ARDS). Roger and others favor suspecting tuberculosis in all cases of acute respiratory failure of unknown origin. By 1918, it could be said, in so far as tuberculosis was concerned, that the world was a supersaturated sponge ready to ignite and that among its most vulnerable parts was the very Midwest where the 1918 unknown pandemic began. It is theorized that the lethal pig epidemic that began in Kansas just prior to the first human outbreaks was a disease of avian and human tuberculosis genetically combined through mycobacteriophage interchange, with the pig, susceptible to both, as its involuntary living culture medium. What are the implications of mistaking a virus such as Influenza A for what mycobacterial disease is actually causing? They would be disastrous, with useless treatment and preventative stockpiles. The obvious need for further investigation is presently imminent and pressing.

Animals↗
PubMed2006

Vertical transmission of a fluoroquinolone-resistant Escherichia coli within an integrated broiler operation.

The epidemiology of an enrofloxacin-resistant Escherichia coli clone was investigated during two separate outbreaks of colibacillosis in the Danish broiler production. In total five flocks were reported affected by the outbreaks. Recorded first-week mortalities were in the range of 1.7-12.7%. The clone was first isolated from dead broilers and subsequently demonstrated in samples from associated hatchers and the parent flock with its embryonated eggs, suggesting a vertical transmission from the parents. The second outbreak involved two broiler flocks unrelated to the affected flocks from the first outbreak. However, the clone could not be demonstrated in the associated parent flock. Furthermore, samplings from grand-parent flocks were negative for the outbreak clone. The clonality was evaluated by plasmid profiling and pulsed-field gel electrophoresis. None of the recognized virulence factors were demonstrated in the outbreak clone by microarray and PCR assay. The molecular background for the fluoroquinolone-resistance was investigated and point mutations in gyrA and parC leading to amino-acid substitutions in quinolone-resistance determining regions of GyrA and ParC were demonstrated. Vertical transmission of enrofloxacin-resistant E. coli from healthy parents resulting in high first-week mortality in the offspring illustrates the potential of the emergence and spreading of fluoroquinolone-resistant bacteria in animal husbandry, even though the use of fluoroquinolones is restricted.

Animals↗
PubMed2000

Inflammation is a component of neurodegeneration in response to Venezuelan equine encephalitis virus infection in mice.

Infection with the mosquito-transmitted Venezuelan equine encephalitis virus (VEE) causes an acute systemic febrile illness followed by meningoencephalitis. In this communication we characterize the cytokine profile induced in the central nervous system (CNS) in response to virulent or attenuated strains of VEE using RNase Protection Assays. Virulent VEE causes an upregulation of multiple pro-inflammatory genes including inducible nitric oxide synthase (iNOS) and tumor necrosis factor alpha (TNF-alpha). To determine if iNOS and TNF-alpha contribute to the neuropathogenesis of VEE infection, iNOS and TNF receptor knockout mice were used in VEE mortality studies and exhibited extended survival times. Finally, CNS tissue sections labeled for VEE antigen, and adjacent sections double-labeled for an astrocyte marker and apoptosis, revealed that apoptosis of neurons occurs not only in areas of the brain positive for VEE-antigen, but also in areas of astrogliosis. These findings suggest that the inflammatory response, which is in part mediated by iNOS and TNF-alpha, may contribute to neurodegeneration following encephalitic virus infection.

Animals↗
PubMed2000

Invasiveness of Salmonella serotypes Typhimurium and Enteritidis of human gastro-enteritic origin for rabbit ileum: role of LPS, plasmids and host factors.

An organ culture system involving explants of distal rabbit ileum was used to study the roles of lipopolysaccharide (LPS) and plasmids in primary invasiveness for enterocytes in situ of strains of Salmonella serotypes Typhimurium and Enteritidis. Long-chain LPS per se does not confer invasiveness on Typhimurium, as known avirulent, hypo-invasive strains express smooth LPS. However, the invasiveness of a naturally occurring rough isogenic derivative of Salmonella serotype Enteritidis PT 4 was about half that of its wild-type parent. Therefore, smooth LPS appears to play a secondary role in maximising invasiveness. No evidence was found to correlate primary invasiveness for gut of 18 strains of Typhimurium with plasmid profiles in general or with the 60-MDa serovar-specific virulence plasmid in particular. Evidence is presented that strongly suggests a seasonal variability in susceptibility of rabbit gut to invasion by Typhimurium. Although no explanation is given for this summer insusceptibility, the data indicate the importance of the physiological status of the host in relation to susceptibility to invasion by Salmonella.

Animals↗
PubMedDate not supplied

Infectious bovine keratoconjunctivitis: a review.

The economic impact of infectious bovine keratoconjunctivitis (IBK) warrants continued investigation of the mechanisms by which Moraxella bovis survives on and colonizes the corneal surface. Virulent strains of M bovis produce hemolysin and exhibit different plasmid profiles than nonvirulent strains. Interactions among host, environment, vector, season, and concurrent infection influence the prevalence of IBK. Mycoplasma sp. or infectious bovine rhinotracheitis virus may enhance or hasten the disease process. The manifestations of IBK may range from mild conjunctivitis to severe ulceration, corneal perforation, and blindness. Treatment of IBK is dictated by economic considerations, intended animal use, and feasibility of administration. Antibiotic therapy is aimed at achieving drug concentrations in tears to meet or exceed the minimum inhibitory concentration for prolonged periods. At present, IBK is not a preventable disease. Affected animals must be separated from the herd and vector control vigorously instituted. Carrier animals must be identified and removed from the herd. Vaccination trials have been unsuccessful because of pili antigen cross-reactivity, variable strains, and uncontrolled environmental factors. Recent investigations have determined that M bovis may utilize host iron sources via iron-repressible outer membrane proteins and siderophores for growth. Elucidation of normal defense mechanisms of the bovine eye may lead to new strategies to enhance the immune response against M bovis.

Animals↗
PubMed2001

Cloning and characterization of the gene encoding the glutamate dehydrogenase of Streptococcus suis serotype 2.

Given the lack of effective vaccines to control Streptococcus suis infection and the lack of a rapid and reliable molecular diagnostic assay to detect its infection, a polyclonal antibody was raised against the whole-cell protein of S. suis type 2 and used to screen an S. suis gene library in an effort to identify protective antigen(s) and antigens of diagnostic importance. A clone that produced a 45-kDa S. suis-specific protein was identified by Western blotting. Restriction analysis showed that the gene encoding the 45-kDa protein was present on a 1.6-kb pair DraI region on the cloned chromosomal fragment. The nucleotide sequence contained an open reading frame that encoded a polypeptide of 448 amino acid residues with a calculated molecular mass of 48.8 kDa, in close agreement with the size observed on Western blots. A GenBank database search revealed that the derived amino acid sequence is homologous to the sequence of glutamate dehydrogenase (GDH) protein isolated from various sources, including conserved motifs and functional domains typical of the family 1-type hexameric GDH proteins, thus placing it in that family. Because of these similarities, the protein was designated the GDH of S. suis. Hybridization studies showed that the gene is conserved among the S. suis type 2 strains tested. Antiserum raised against the purified recombinant protein was reactive with a protein of the same molecular size as the recombinant protein in S. suis strains, suggesting expression of the gene in all of the isolates and antigenic conservation of the protein. The recombinant protein was reactive with serum from pigs experimentally infected with a virulent strain of S. suis type 2, suggesting that the protein might serve as an antigen of diagnostic importance to detect S. suis infection. Activity staining showed that the S. suis GDH activity is NAD(P)H dependent but, unlike the NAD(P)H-dependent GDH from various other sources, that of S. suis utilizes L-glutamate rather than alpha-ketoglutarate as the substrate. Highly virulent strains of S. suis type 2 could be distinguished from moderately virulent and avirulent strains on the basis of their GDH protein profile following activity staining on a nondenaturing gel. We examined the cellular location of the protein using a whole-cell enzyme-linked immunosorbent assay and an immunogold-labeling technique. Results showed that the S. suis GDH protein is exposed at the surface of intact cells.

Animals↗
PubMed1985

Induction of protective immunity to Plasmodium falciparum in Saimiri sciureus monkeys with partially purified exoantigens.

Soluble Plasmodium falciparum exoantigens in crude culture supernatant fluids induced protective immunity against experimental falciparum malaria in Bolivian Saimiri sciureus monkeys. Susceptible squirrel monkeys were vaccinated with an aluminum hydroxide-fortified fraction purified from culture supernatants of P. falciparum Indochina I and Geneve/SGE-1 by cation-exchange (sulfopropyl-trisacryl) chromatography. Animals immunized with sulfopropyl-purified and corresponding control immunogens were challenged with whole blood containing monkey-adapted virulent organisms of the Indochina I strain. Hematological, serological, and parasitological profiles, including the appearance of crisis forms, served as potential indicators of protection. This immunogen conferred significant clinical protection of squirrel monkeys against needle challenge with the homologous Indochina I strain and a moderate degree of heterologous strain immunity.

Animals↗