Adhesion in meningococcus

The adhesive activity of 113 meningococcal strains with different invasive properties and 10 Neisseria nonpathogenic strains have been studied. Adhesive properties have been revealed in 80-82% of these strains. Meningococcal strains isolated from the nasopharynx of carriers possess high hemagglutinating activity. The percentage of cells with pili in these strain was also higher than that in meningococcal strains isolated from the liquor of patients. This shows the presence of direct correlation between the number of pili in the cells (according to the data of electron microscopy) and their activity in the hemagglutination test, which makes it possible to use this test for the determination of the adhesive capacity of meningococci, associated with the presence of pili.     

Analysis of lipooligosaccharide biosynthesis in the Neisseriaceae

Neisserial lipooligosaccharide (LOS) contains three oligosaccharide chains, termed the alpha, beta, and gamma chains. We used Southern hybridization experiments on DNA isolated from various Neisseria spp. to determine if strains considered to be nonpathogenic possessed DNA sequences homologous with genes involved in the biosynthesis of these oligosaccharide chains. The presence or absence of specific genes was compared to the LOS profiles expressed by each strain, as characterized by their mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel and their reactivities with various LOS-specific monoclonal antibodies. A great deal of heterogeneity was seen with respect to the presence of genes encoding glycosyltransferases in Neisseria. All pathogenic species were found to possess DNA sequences homologous with the lgt gene cluster, a group of genes needed for the synthesis of the alpha chain. Some of these genes were also found to be present in strains considered to be nonpathogenic, such as Neisseria lactamica, N. subflava, and N. sicca. Some nonpathogenic Neisseria spp. were able to express high-molecular-mass LOS structures, even though they lacked the DNA sequences homologous with rfaF, a gene whose product must act before gonococcal and meningococcal LOS can be elongated. Using a PCR amplification strategy, in combination with DNA sequencing, we demonstrated that N. subflava 44 possessed lgtA, lgtB, and lgtE genes. The predicted amino acid sequence encoded by each of these genes suggested that they encoded functional proteins; however, structural analysis of LOS isolated from this strain indicated that the bulk of its LOS was not modified by these gene products. This suggests the existence of an additional regulatory mechanism that is responsible for the limited expression of these genes in this strain.     

Interactions between Neisseria meningitidis and cell cultures (data of cytomorphologic studies)

The present work shows that the cytopathogenic action of N. meningitidis on continuous human amniotic epithelial cell culture FL begins from their active adhesion and subsequent invasion. The degree of the manifestation of the cytopathic effect depends on the capacity of the infective agent for adhesion and invasion and on its biological properties, as well as on the initial state of the cells. The infection of the cells is accompanied by disturbances in their mitotic activity together with the lesions of their chromosomal apparatus. The cells die either in the state of degenerative mitosis, or as the result of the rupture of the cytoplasm in massively invaded cells. The response of the cells to the invasion of faintly cytopathogenic and noncytopathogenic strains takes the form of nonprofessional phagocytosis.     

Immunological characteristics of the protein antigens of the family Neisseriaceae. II. The importance of an immunochemical analysis of the protein complexes for a study of taxonomy problems]

The study of antigenic interrelations in the family Neisseriaceae resulted in the isolation of 2 main immunologically separated variants of protein complexes: the first variant was characteristic of nonpathogenic and pathogenic species of the genus Neisseria as well as of 7 taxonomically undefined Neisseria species (N. lactamicus, N. cuniculi, N. ellongata, N. ovis, N. animalis, N. cinerea, N. canis) and Gemella haemolysans; the second variant was represented by the genera Branhamella and Acinetobacter. N. caviae and 3 out of 14 Neisseria strains of undefined species had no common antigens with the genera Neisseria and Branhamella. The importance of the immunotyping of protein complexes for studying the problems connected with the taxonomy of the family Neisseriaceae was considered.     

Interaction of T-activin with peritoneal macrophages

The action of T-activin on peritoneal macrophages of CBA mice after its introduction into the animals has been studied. In intact mice the phagocytic activity of macrophages and their resistance to the cytopathogenic action of Salmonella typhimurium live cells remains unchanged. The injection of corpuscular pertussis vaccine into mice leads to a decrease in the resistance of macrophages to the action of salmonellae. The simultaneous injection of T-activin into mice in doses of 0.1 and 1.0 microgram per animal abolishes the damaging action of the vaccine. The analysis of the in vitro action of T-activin on macrophages of intact mice revealed that the preliminary incubation of cells with the preparation sharply increases their resistance to the action of salmonellae, while its introduction simultaneously with bacteria or after them rapidly leads to the death of macrophages. The action of T-activin is supposed to be linked with triggering the biosynthetic processes mediating the resistance of macrophages to the cytopathogenic action of salmonellae.     

Colonization of flax roots and early physiological responses of flax cells inoculated with pathogenic and nonpathogenic strains of Fusarium oxysporum

Fusarium oxysporum includes nonpathogenic strains and pathogenic strains that can induce necrosis or tracheomycosis in plants. The objective of this study was to compare the abilities of a pathogenic strain (Foln3) and a nonpathogenic strain (Fo47) to colonize flax roots and to induce early physiological responses in flax cell culture suspensions. Both strains colonized the outer cortex of the root; however, plant defense reactions, i.e., the presence of wall appositions, osmiophilic material, and collapsed cells, were less frequent and less intense in a root colonized by Foln3 than by Fo47. Early physiological responses were measured in flax cell suspensions confronted with germinated microconidia of both strains. Both pathogenic (Foln3) and nonpathogenic strains (Fo47) triggered transient H(2)O(2) production in the first few minutes of the interaction, but the nonpathogenic strain also induced a second burst 3 h postinoculation. Ca(2+) influx was more intense in cells inoculated with Fo47 than in cells inoculated with Foln3. Similarly, alkalinization of the extracellular medium was higher with Fo47 than with Foln3. Inoculation of the fungi into flax cell suspensions induced cell death 10 to 20 h postinoculation, with a higher percentage of dead cells observed with Fo47 than with Foln3 beginning at 14 h. This is the first report showing that early physiological responses of flax cells can be used to distinguish pathogenic and nonpathogenic strains of the soil-borne fungus F. oxysporum.     

Neisserial pilin genes display extensive interspecies diversity

All Neisseria live in association with host cells, however, little is known about the genetic potential of nonpathogenic Neisseria species to express attachment factors such as pili. In this study, we demonstrate that type IV pilin-encoding genes are present in a wide range of Neisseria species. N. sicca, N. subflava, and N. elongata each contain two putative pilE genes arranged in tandem, while single genes were identified in N. polysaccharea, N. mucosa, and N. denitrificans. Neisserial pilE genes are highly diverse and display features consistent with a history of horizontal gene transfer.     

Evolution of an Autotransporter: Domain Shuffling and Lateral Transfer from Pathogenic Haemophilus to Neisseria

The genomes of pathogenic Haemophilus influenzae strains are larger than that of Rd KW20 (Rd), the nonpathogenic laboratory strain whose genome has been sequenced. To identify potential virulence genes, we examined genes possessed by Int1, an invasive nonencapsulated isolate from a meningitis patient, but absent from Rd. Int1 was found to have a novel gene termed lav, predicted to encode a member of the AIDA-I/VirG/PerT family of virulence-associated autotransporters (ATs). Associated with lav are multiple repeats of the tetranucleotide GCAA, implicated in translational phase variation of surface molecules. Laterally acquired by H. influenzae, lav is restricted in distribution to a few pathogenic strains, including H. influenzae biotype aegyptius and Brazilian purpuric fever isolates. The DNA sequence of lav is surprisingly similar to that of a gene previously described for Neisseria meningitidis. Sequence comparisons suggest that lav was transferred relatively recently from Haemophilus to Neisseria, shortly before the divergence of N. meningitidis and Neisseria gonorrhoeae. Segments of lav predicted to encode passenger and beta-domains differ sharply in G+C base content, supporting the idea that AT genes have evolved by fusing domains which originated in different genomes. Homology and base sequence comparisons suggest that a novel biotype aegyptius AT arose by swapping an unrelated sequence for the passenger domain of lav. The unusually mobile lav locus joins a growing list of genes transferred from H. influenzae to Neisseria. Frequent gene exchange suggests a common pool of hypervariable contingency genes and may help to explain the origin of invasiveness in certain respiratory pathogens.     

Induction of cytopathogenicity in mammalian cell lines challenged with culturable enteric viruses and its enhancement by 5-iododeoxyuridine.

Cultures of 17 established cell lines were tested against 105 enteric virus types for capacity to support viral replication as indicated by cytopathogenic effect production. Enhancement of susceptibility by treatment of the cells with 5-iododeoxyuridine was evaluated in parallel with untreated cells. Cytopathogenic effect was produced in two or more cell lines by every virus tested except six strains of group A coxsackie virus. No cell line was found to be susceptible to these six virus types. In general, treatment with 5-iododeoxyuridine provided a more rapid onset of cytopathogenic effect in susceptible cells and in some instances resulted in refractory cells becoming permissive to viral replication. The use of 5-iododeoxyuridine allowed two human embryonic lines (HEL-299 and L-132), in combination, to be susceptible to all but the six group A coxsackie virus strains.     

Induction of cytopathogenicity in mammalian cell lines challenged with culturable enteric viruses and its enhancement by 5-iododeoxyuridine

Cultures of 17 established cell lines were tested against 105 enteric virus types for capacity to support viral replication as indicated by cytopathogenic effect production. Enhancement of susceptibility by treatment of the cells with 5-iododeoxyuridine was evaluated in parallel with untreated cells. Cytopathogenic effect was produced in two or more cell lines by every virus tested except six strains of group A coxsackie virus. No cell line was found to be susceptible to these six virus types. In general, treatment with 5-iododeoxyuridine provided a more rapid onset of cytopathogenic effect in susceptible cells and in some instances resulted in refractory cells becoming permissive to viral replication. The use of 5-iododeoxyuridine allowed two human embryonic lines (HEL-299 and L-132), in combination, to be susceptible to all but the six group A coxsackie virus strains.     

Mycoplasma pneumoniae attachment to glutaraldehyde-treated human WiDr cell cultures

Attachment of Mycoplasma pneumoniae to host cells initiates disease, and the attachment components may represent important protective immunogens for preventing disease. We have studied the mechanisms of attachment using in vitro cell culture systems and selected pathogenic and nonpathogenic strains of M. pneumoniae. Attachment of the pathogenic strains M129 and PI-1428 was several fold greater than attachment of the nonpathogenic strain, and attachment of strains M129 and PI-1428 was reduced by 21 to 63% when human WiDr cell monolayers were exposed to neuraminidase, supporting the concept that M. pneumoniae attaches to mammalian cells by a neuraminidase-sensitive glycoconjugate. While attachment of the two pathogenic strains was markedly reduced by treating the WiDr cells with glutaraldehyde, glutaraldehyde treatment produced minimal effects on the attachment of the nonpathogenic strain B176. Glutaraldehyde treatment also altered the temperature dependence of attachment by the pathogenic strains. Because glutaraldehyde-treated WiDr cell monolayers showed little difference in attachment between pathogenic and nonpathogenic strains, glutaraldehyde-treated cells are not appropriate cell substrates for studying M. pneumoniae attachment mechanisms or identifying immunogens for vaccine development.     

Immunochemical properties of a protective cross-reacting antigen of meningococci

The study of protective cross-reacting antigenic preparations isolated from meningococci of groups A and C in the blot immunoassay has shown the presence of a group of proteins with a molecular weight ranging from 23 to 31 KD and common for 8 tested serological groups of meningococci, gonococci and 4 nonpathogenic Neisseria species. The possible role of these structures as common Neisseria antigen in the formation of natural resistance to meningococcal infection is discussed.     

Colonization of Flax Roots and Early Physiological Responses of Flax Cells Inoculated with Pathogenic and Nonpathogenic Strains of Fusarium oxysporum

Fusarium oxysporum includes nonpathogenic strains and pathogenic strains that can induce necrosis or tracheomycosis in plants. The objective of this study was to compare the abilities of a pathogenic strain (Foln3) and a nonpathogenic strain (Fo47) to colonize flax roots and to induce early physiological responses in flax cell culture suspensions. Both strains colonized the outer cortex of the root; however, plant defense reactions, i.e., the presence of wall appositions, osmiophilic material, and collapsed cells, were less frequent and less intense in a root colonized by Foln3 than by Fo47. Early physiological responses were measured in flax cell suspensions confronted with germinated microconidia of both strains. Both pathogenic (Foln3) and nonpathogenic strains (Fo47) triggered transient H₂O₂ production in the first few minutes of the interaction, but the nonpathogenic strain also induced a second burst 3 h postinoculation. Ca²⁺ influx was more intense in cells inoculated with Fo47 than in cells inoculated with Foln3. Similarly, alkalinization of the extracellular medium was higher with Fo47 than with Foln3. Inoculation of the fungi into flax cell suspensions induced cell death 10 to 20 h postinoculation, with a higher percentage of dead cells observed with Fo47 than with Foln3 beginning at 14 h. This is the first report showing that early physiological responses of flax cells can be used to distinguish pathogenic and nonpathogenic strains of the soil-borne fungus F. oxysporum.     

Comparative study of the pathogenicity of free-living amoebae in mice and their cytopathogenic effect in vitro

The study of the experimental pathogenic effect on the mouse of 47 strains of free-living amoebas (Vahlkampfia, Naegleria, Hartmannella and Acanthamoeba) showed that 5 strains belonging all to the species A. polyphaga could induce a fatal meningo-encephalitis in the mouse. After axenisation of 12 strains of Acanthamoeba, the study of the cytopathogenic effect in vitro showed that all the strains studied were able to induce, sooner or later, the destruction of the cellular layer. But, using the same inoculum, the strains pathogenic for the animal, seemed to have a quicker cytopathogenic effect in vitro.     

Cytopathogenic effect of E. coli cells containing heterogeneous human O(H) type antigen on human cells in culture]

Interaction of two enteropathogenic strains E. coli O55-K59 and human Hela cells containing O(H) isoantigen was studied. When E. coli strain No. 5789 containing heterologic antigen O(H) was added to HeLa cell culture the cytopathogenic effect with the microbial doses of 2 X 10(10), 2 X 10(5), 2X 10(4) was revealed on the third day of the interaction. A dose of 2 X 10(3) of E. coli microbes gave no such effect. Strain No. 3827 containing no heterologic antigen of ABO type failed to exert any cytopathogenic effect with maximal, mean, and minimal doses of the microbes. It is assumed that the cytopathogenic effect of strain No. 5789 is connected with the presence of the strain antigen identical to the group antigen of the human cell culture under study.     

An Infectious Agent Associated with Amebas of the Genus Naegleria*

A study of amebas of the genera Naegleria, Acanthamoeba, Polysphondylium, and Didymium shows that a cytopathogenic agent that is filterable and passageable is present only in the strains of the Naegleria whether they are obtained free-living from soil samples (N. gruberi) or as pathogens from humans (N. fowleri). The agents obtained from the different Naegleria strains are similar in amount and in their cytopathogenic interaction with chick cultures. The agent has characteristics that distinguish it from the known viruses.     

Phylogenetic and Variable-Number Tandem-Repeat Analyses Identify Nonpathogenic Xanthomonas arboricola Lineages Lacking the Canonical Type III Secretion System

Xanthomonas arboricola is conventionally known as a taxon of plant-pathogenic bacteria that includes seven pathovars. This study showed that X. arboricola also encompasses nonpathogenic bacteria that cause no apparent disease symptoms on their hosts. The aim of this study was to assess the X. arboricola population structure associated with walnut, including nonpathogenic strains, in order to gain a better understanding of the role of nonpathogenic xanthomonads in walnut microbiota. A multilocus sequence analysis (MLSA) was performed on a collection of 100 X. arboricola strains, including 27 nonpathogenic strains isolated from walnut. Nonpathogenic strains grouped outside clusters defined by pathovars and formed separate genetic lineages. A multilocus variable-number tandem-repeat analysis (MLVA) conducted on a collection of X. arboricola strains isolated from walnut showed that nonpathogenic strains clustered separately from clonal complexes containing Xanthomonas arboricola pv. juglandis strains. Some nonpathogenic strains of X. arboricola did not contain the canonical type III secretion system (T3SS) and harbored only one to three type III effector (T3E) genes. In the nonpathogenic strains CFBP 7640 and CFBP 7653, neither T3SS genes nor any of the analyzed T3E genes were detected. This finding raises a question about the origin of nonpathogenic strains and the evolution of plant pathogenicity in X. arboricola. T3E genes that were not detected in any nonpathogenic isolates studied represent excellent candidates to be those responsible for pathogenicity in X. arboricola.     

Electron microscopic study of the cytopathogenic action of meningococci in a continuous human amnion cell culture

The electron-microscopic study of the interaction of meningococci with continuous human amnion cell culture F1 has revealed that this process comprises 3 stages. The study has shown that, following the adhesion of meningococci to the surface of cells F1, these cells are invaded by individual coccal forms of meningococci. In response to infection vacuoles appear in the cytoplasm of the cells. Meningococci are either phagocytosed inside these vacuoles, or their release into the intercellular space and the death of the infected by meningococci are observed. When the cells are infected by cytopathogenic strains, the infectious process results in the appearance of degenerative changes in the cells.     

Starch gel electrophoresis: an effective method for separation of pathogenic and nonpathogenic Naegleria strains

Isoenzyme electrophoresis of 7 different enzyme systems was used to compare 24 strains of Naegleria fowleri and 6 strains of N. gruberi. The 30 strains could be grouped into 4 distinct categories based upon zymogram patterns. No interstrain band variation in all enzyme systems was demonstrated in pathogenic strains of N. fowleri. Three nonpathogenic high temperature-tolerant strains of Naegleria had similar zymograms. Four of the 5 remaining nonpathogenic Naegleria strains had no interstrain band variation. Based upon zymograms, the 22 pathogenic strains constitute a homogenous species. Similarly the high temperature-tolerant nonpathogenic strains formed a cohesive group. The remaining nonpathogenic strains could be separated into 2 groups.