Organism resembling Neisseria gonorrhoeae and Neisseria meningitidis.

A problem isolate resembling Neisseria gonorrhoeae and Neisseria meningitidis is reported. Growth and biochemical characteristics indicated the organism to be N. meningitidis, whereas serological characteristics indicated it to be N. gonorrhoeae. This vaginal isolate may be a genetically transformed gonococcus with the ability to utilize maltose. Conversely, it may be a meningococcus which has acquired antigenic determinants of N. gonorrhoeae.     

Assessment of attachment of Neisseria gonorrhoeae to HeLa cells by double radiolabeling.

Attachment of Neisseria gonorrhoeae to HeLa cells was assessed by a technique using double radioisotopic labeling. Piliated, virulent bacteria from colony type 2 attached to HeLa cells to a greater extent than nonpiliated, avirulent bacteria from colony type 4. Maximal attachment rates for bacteria from both colony types occurred during the early incubation periods at 37 degrees C, and the HeLa cells appeared saturated at 4 h. Attachment was maximum at pH 6.5 and dependent upon the multiplicity of infection. Treatment of the HeLa cells with trypsin diminished the degree of attachment, but this effect substantially disappeared by 24 h after trypsin treatment. Scanning electron microscopy revealed bacteria of colony types 2 and 4 adhered to the HeLa cell surface. Thin-section transmission electron microscopy showed that bacteria were associated with the surface of the HeLa cell but not ingested.     

Characteristics of Neisseria gonorrhoeae isolated in Australia showing decreased sensitivity to quinolone antibiotics.

Forty three strains of Neisseria gonorrhoeae with decreased sensitivity to quinolone antibiotics were detected amongst 2141 Australian isolates of gonococci examined in the years 1984 to 1990. The strains examined belonged to 23 different auxotype/serovar classes, were generally more resistant to other antibiotics and, in the majority of cases, were isolated from travellers entering or returning to Australia from SE Asia. Quinolone-sensitive wild-type gonococci became less sensitive to these agents in vitro at a relatively high frequency when grown in the presence of quinolone concentrations at or around the MIC (Mean Inhibitory Concentration) of the antibiotic. Further increments in the levels of quinolone resistance of the already less-sensitive gonococci were also produced by this means, but high-level resistance to these agents was not observed. This suggests that mechanisms other than alterations in the DNA-gyrase of the organisms were responsible for the changes seen. Although spread of quinolone resistance in gonococci in Australia is unlikely to be rapid, if these antibiotics are used in therapy, treatment regimens with higher rather than lower dosages of quinolone antibiotics should be employed.     

Novel lipoprotein expressed by Neisseria meningitidis but not by Neisseria gonorrhoeae.

The ppk gene, which codes for the enzyme polyphosphate kinase in Neisseria meningitidis strain BNCV, is preceded by an open reading frame coding for a protein with a predicted size of 19.2 kDa with a typical lipoprotein signal sequence of 21 amino acids. The protein has significant homology to the N-terminal portion of an outer membrane protein from Haemophilus somnus (J. Won and R. W. Griffith, Infect. Immun. 61:2813-2821, 1993). Sequencing of the same open reading frame from meningococcus strain M1080 predicted an almost identical protein. Antisera were raised against the lipoprotein, expressed in Escherichia coli as a fusion protein with glutathione S-transferase. The antisera reacted with meningococcal membrane fractions on a Western blot (immunoblot) but did not elicit complement-dependent bactericidal activity. Restriction enzyme digestion demonstrated conservation of this portion of the meningococcal and gonococcal chromosomes. However, antisera raised to the recombinant protein showed that the protein was absent from all strains of gonococcus tested. The sequences of the gene from several strains of Neisseria gonorrhoeae and N. meningitidis were compared and found to be almost identical, except that the coding sequences from all of the gonococcal strains were terminated prematurely as a result of a frameshift mutation. The significance of the remarkable conservation of these gonococcal genes is discussed.     

Lipopolysaccharide banding patterns of Neisseria meningitidis and Neisseria gonorrhoeae.

The lipopolysaccharides of Neisseria meningitidis and Neisseria gonorrhoeae were examined by electrophoresis after whole-cell lysis and proteinase K digestion. The banding patterns observed from clinical isolates and laboratory strains demonstrated lipopolysaccharide which included a small number of smooth high-molecular-weight molecules as well as the previously reported lower-molecular-weight rough lipopolysaccharide.     

Evidence for functionally distinct pili expressed by Neisseria meningitidis.

In order to investigate possible functional consequences of phase and antigenic variation of meningococci, the attachment of 15 strains of Neisseria meningitidis to human erythrocytes was studied by a nitrocellulose hemadsorption assay. This assay allows the study of individual meningococcal colonies with respect to erythrocyte attachment. Of the 15 strains studied, 7 demonstrated binding of human erythrocytes (HA+). Among these seven strains, the percentage of colonies that were HA+ ranged from 0.2 to 97%. Meningococcal colonies that did not produce pilin (the major structural subunit of pili) did not demonstrate erythrocyte binding (HA-). The HA+ colony phenotype was correlated with assembly of pilin into pili and expression of pili on the meningococcal surface. However, only some piliated colonies bound human erythrocytes. This could not be explained by differences between piliated HA+ and HA- colonies in the amount of pilin produced or by differences in number of pili expressed per diplococcus. Pili of five of the meningococcal strains with HA+ colonies were antigenically related to gonococcal pili (class I meningococcal pili), but HA+ colonies were also seen in two meningococcal strains expressing class II meningococcal pili. Changes from HA+ to HA- and from HA- to HA+, in the presence of continuing pilin production and pilus assembly, occurred at frequencies of up to 10(-2)/CFU per generation. Such frequencies resemble those of phase and antigenic variation described previously for Neisseria species pilin. These studies indicate that phase variation influences the ability of meningococci to attach to human cells and suggest that meningococci may express functionally different pili.     

Rapid identification of Neisseria gonorrhoeae and Neisseria meningitidis by using enzymatic profiles.

The enzymatic profiles of Neisseria gonorrhoeae, N. meningitidis, and related species were determined, using a total of 48 chromogenic substrates. Enzyme classes assayed for included glycosidases, aminopeptidases, phosphoamidases, proteases, lipases, esterases, and aryl sulfatase. A final test selection of 10 substrates, based upon their differential and reproducible characteristics, allowed the separation of N. gonorrhoeae and N. meningitidis from each other and from all species tested within 4 h after primary isolation on modified Thayer-Martin medium. The need for subculturing suspect colonies from modified Thayer-Martin medium to chocolate medium with a subsequent loss of 18 to 24 h of identification is eliminated.     

Adherence of Neisseria meningitidis to human epithelial cells.

Carrier strains of Neisseria meningitidis are recovered almost solely from the posterior pharynx and they are often nongroupable or rough. Invasive strains can be serogrouped (encapsulated). We studied adherence of both carrier- and patient-derived serogroupable and nongroupable meningococci to buccal epithelial and posterior pharyngeal cells. Fresh meningococcal isolates attached significantly better to pharyngeal than to buccal cells (P = 0.01). Strains that could be serogrouped adhered less than nongroupable strains (P less than 0.05). Meningococci passed in vitro became hemagglutinin negative and nonpiliated. Hemagglutinin-negative meningococci always adhered less to both epithelial cell types than the hemagglutinin-positive variants of the same strain. These results indicate that meningococcal pili probably mediate attachment to oropharyngeal cells, but encapsulation may reduce adherence. Localization of meningococci in the posterior pharynx is in part explained by the receptivity of the epithelial cells in this area for meningococci.     

Differential response of human monocytes to Neisseria gonorrhoeae variants expressing pili and opacity proteins.

Experiments in vitro suggest that Neisseria gonorrhoeae surface variation plays a key role in gonococcal pathogenesis by providing the appropriate bacterial phenotypes to go through different stages of the infection. Here we report on the effects of phase and antigen variation of two major gonococcal adhesins, pili and opacity (Opa) outer membrane proteins, on the interaction of the gonococci with human monocytes. Using a set of recombinants of gonococcus strain MS11 that each express 1 of 11 genetically defined Opa proteins or a defined type of pilus, we found that both Opa proteins and pili promote bacterial phagocytosis by monocytes in the absence of serum and that this feature largely depends on the type of protein that is expressed. One of the Opa proteins (Opa[50]) strongly promoted uptake by monocytes but had little effect on the interaction with polymorphonuclear leukocytes under the conditions employed. Similarly, the phagocytosis-promoting effect of the pili was much more pronounced in monocytes than in neutrophils (4-fold versus 22-fold stimulation of uptake, respectively). Only a subpopulation of both types of phagocytes actively ingested bacteria, as has been observed during natural infections. Measurements of luminol-enhanced chemiluminescence demonstrated that phagocytosis of opaque but not piliated gonococci was accompanied by an increase in oxygen-reactive metabolites. These findings demonstrate that the monocyte response towards gonococci is highly dependent on the bacterial phenotype and differs from the neutrophil response. This diversity in bacterial behavior towards various types of human phagocytic cells underlines the biological impact of gonococcal surface variation and may explain previous contradictory results on this subject.     

Monoclonal antibody analysis of lipopolysaccharide from Neisseria gonorrhoeae and Neisseria meningitidis.

A hybridoma produced by the polyethylene glycol fusion of the NS-1 variant of the P3x63Ag8 BALB/c plasmacytoma to splenocytes harvested from a BALB/c mouse immunized with whole gonococci was found to be producing antibody to a common region on gonococcal lipopolysaccharide (LPS). Enzyme-linked immunosorbent assay inhibition systems were established by utilizing this antibody, designated 3F11, and 100% inhibition occurred with both LPS and the LPS-LPS and LPS-derived polysaccharides partially inhibited the enzyme-linked immunosorbent assay, whereas similar preparations isolated from Escherichia coli O:111, the J-5 mutant of this strain, and Salmonella minnesota Re595 failed to inhibit the assay. Studies utilizing whole gonococcal strains 4505 and the isogenic variant 4505r, which lacks both the LPS serotype and common determinants as inhibitors, demonstrated that the determinant recognized by the 3F11 antibody was present on the surface of 4505 and absent on 4505r. Inhibition studies were performed with beta-glucose, beta-galactose, D-glucosamine, D-galactosamine, heptose, 2-keto-3-deoxyoctanoate, N-acetylglucosamine, N-acetylgalactosamine, alpha-lactose, and beta-lactose. Complete inhibition of the enzyme-linked immunosorbent assay occurred with D-galactosamine, and partial inhibition was achieved with both alpha-lactose and beta-lactose. Based on these observations, the 3F11 antibody recognizes a site common to gonococcal LPS which is partially shared by meningococcal LPS. The chemical structure of the determinant appears to be a D-galactosamine-O-D-galactopyranosyl-(1-4)-D-glucopyranose. Additional specificity may be conferred by the steric relationship of the determinant on the intact LPS.     

Species specificity of attachment and damage to oviduct mucosa by Neisseria gonorrhoeae.

Neisseria gonorrhoeae colony type 1 were inoculated into organ cultures of oviducts obtained from various animal species. Gonococci rapidly attached to extensive areas of the mucosa of human oviducts (fallopian tubes), entered the mucous-secreting cells, and caused histological damage to the tissues. In addition, 2 to 4 days after infection there was complete loss of ciliary activity. In contrast, gonococci attached very scantily or not at all to the mucosa of rabbit, porcine, or bovine oviducts. However, the organisms multiplied in the medium of these organ cultures and were located sometimes in the base of mucosal cells and in large numbers in the submucosa. Despit this, there was no histological evidence of damage, and at least 7 days after infection ciliary activity was maintained equally as well as it was in uninfected control cultures. The host specificity of N. gonorrhoeae appears to be determined, at least in part, by a markedly diminished ability of the organisms to attach to and damage the genital mucosa of nonhuman species.     

Proteins that appear to be associated with pili in Neisseria gonorrhoeae.

Pili of Neisseria gonorrhoeae are thought to be composed entirely of identical subunits, called pilin, that self-assemble in vitro. Previous pilus purification methods have relied on this latter point, and dissociation and reassociation of pilin subunits has yielded pilin preparations of high purity. Such a procedure could result in the loss of any pilus-associated proteins. We have developed a procedure for the isolation of intact native pili in a deoxycholate-urea buffer in which the pili are fractionated on the basis of size and hydrophobicity. Electron microscopy indicates that the pili are largely free from outer membrane vesicles and other cellular material. Electrophoretic analysis has shown that a number of proteins copurify with pilin. Antibodies to these proteins could be removed from an antiserum against whole piliated cells by absorption with piliated cells but not by absorption with nonpiliated cells. Hence, our results indicate that these proteins could be pilus associated.     

Tn916-generated, lipooligosaccharide mutants of Neisseria meningitidis and Neisseria gonorrhoeae.

A library of Tn916-generated, tetracycline-resistant (Tc) mutants of the group B Neisseri meningitidis strain NMB was screened by using monoclonal antibodies (MAbs) that recognize structural differences in neisserial lipooligosaccharide (LOS). The LOS of parental strain NMB had a relative molecular mass of 4.5 kDa, reacted with MAbs 3F11 and 6B4 but not with MAb 4C4 or 6E4, and contained a lacto-N-neotetrose unit. Two phenotypically stable mutants, SS3 and R6, altered in LOS, were identified by colony immunoblots, electrophoresis, and Western immunoblots. The LOS of mutant SS3 was 3.4 kDa and reacted with MAbs 4C4 and 6E4 but not MAb 3E11 or 6B4. The LOS of mutant R6 was 3.1 to 3.2 kDa and reacted with MAb 6E4 but not MAb 3F11, 6B4, or 4C4. Thus, the LOSs of the R6 and SS3 mutants were predicted to contain different truncations of the core oligosaccharide. The LOS phenotype of each mutant was linked to Tc(r), as determined by transformation of the parent strain with DNA from the mutant. Southern hybridizations and single-specific-primer PCR revealed in each mutant a single truncated tn916 insertion which had lost genes required for mobilization. Tn916 mutagenesis was used to identify two distinct genetic sites in the meningococcal chromosome involved in biosynthesis of the oligosaccharide chain of LOS and to create genetically defined LOS mutants of N. meningitidis and Neisseria gonorrhoeae.     

Ability of Neisseria gonorrhoeae, Neisseria meningitidis, and commensal Neisseria species to obtain iron from lactoferrin.

The ability of 107 Neisseria isolates to compete for iron with human lactoferrin (LF) was examined. Each of 15 meningococci, 53% of 59 selected gonococci, and 24% of 33 commensal Neisseria could use LF-bound iron for growth. Isolates which could not obtain iron from LF were growth inhibited when sufficient LF was added to defined agar medium to bind available free iron. No difference was observed in the ability of colony type 1 and colony type 4 gonococci of the same strain to compete with LF for iron. LF was growth inhibitory for 50% of 22 disseminated disease isolates (DGI strains) and 51% of 35 local urogenital disease isolates (UGI strains). Only 14% of gonococcal isolates requiring arginine, hypoxanthine, and uracil for growth were able to compete with LF for iron, whereas 87% of all other gonococcal isolates could do so (P less than 0.005). Ability to obtain iron from LF does not appear to be required for survival of Neisseria on mucosal surfaces, nor essential for invasion of the bloodstream by gonococci. However, ability to utilize LF as a source of iron may contribute to differences in pathogenicity among certain gonococcal isolates.     

Inhibition of bacterial adhesion by subinhibitory concentrations of antibiotics

Background: Urinary Tract Infections (UTIs) due to Escherichia coli is one of the most common diseases encountered in clinical practice. Most common recognised pathogenic factor in E.coli is adhesion. There is accumulating evidence that through subinhibitory concentrations (sub – MICs) of many antibiotics do not kill bacteria, they are able to interfere with some important aspects of bacterial cell function. Materials and Methods: A study was conducted to investigate the effect of sub MICs (1/2–1/8 MIC) of ciprofloxacin, ceftazidime, gentamicin, ampicillin and co - trimoxazole on E. coli adhesiveness to human vaginal epithelial cells using three strains ATCC 25922, MTCC 729 and U 105. Results: The 1/2 MIC of all the antibiotics tested produced the greatest inhibition of bacterial adhesion. Morphological changes were observed with ciprofloxacin, ceftazidime and ampicillin at 1/2 MIC and to a lesser extent at 1/4 and 1/8 MIC. Co-trimoxazole caused the greatest suppression of adhesion at 1/2 MIC of E. coli strain MTCC 729 when compared with the controls, followed by ceftazidime. Conclusion: These results suggest that co - trimoxazole is the most effective antibiotic in the treatment of urinary tract infections caused by uropathogenic E. coli.     

Analysis of C3 deposition and degradation on Neisseria meningitidis and Neisseria gonorrhoeae.

The deposition and degradation of human complement component C3 on the cell surfaces of Neisseria meningitidis and Neisseria gonorrhoeae were studied. Bacteria were incubated in human serum, and ester-linked C3 fragments were analyzed by hydroxylamine release and immunoblot detection. Similar patterns of C3 degradation were found for both serum-resistant and serum-sensitive meningococcal strains of serogroups A, B, C, Y, and W135, as well as for serum-sensitive gonococcal strains and their sialylated serum-resistant variants. The predominant fragments in all cases were the 40-kDa alpha' 2 chain of iC3b and the 75-kDa beta chain common to both C3b and iC3b. The 67-kDa alpha' 1 chain of iC3b was also detected. The 105-kDa alpha' chain of intact C3b represented a minor proportion of deposited C3. Capsule-specific immunoglobulin G or immunoglobulin A1 did not alter the observed degradation patterns, nor did incubation of meningococci in properdin-deficient serum. The degradation of C3 in C5-, C6-, or C8-deficient serum was the same as that in normal serum, although the deposition of C3 was severely limited, based as indicated by the intensity of the fragments. With the use of an enzyme-linked immunosorbent assay that measured total iC3b and C3, I found that both iC3b deposition and C3 deposition varied among meningococcal and gonococcal strains and that the amounts of iC3b and C3 were independent of the relative quantities of cell surface sialic acid and of serum sensitivity for meningococci but not for gonococci. I conclude that complement activation on neisserial cell surface results in the formation of an identical repertoire of predominantly iC3b fragments of ester-linked C3b molecules regardless of the presence of sialic acid in either the capsule or the lipooligosaccharide or of the sensitivity of the organism to complement-mediated lysis but that the quantities of both ester- and amide-linked iC3b molecules deposited exhibit strain variability.     

Type IV pili of Neisseria gonorrhoeae influence the activation of human CD4+ T cells

Neisseria gonorrhoeae is the causative agent of the sexually transmitted disease gonorrhea, and infection with this organism is typically associated with an intense inflammatory response. In many individuals, however, the infection is asymptomatic and can progress to serious secondary complications. The type IV pili of Neisseria gonorrhoeae mediate binding of the bacteria to host cells and are involved in cellular signal transduction. In these studies we have demonstrated that gonococcal pili influence human CD4+ T cells by using isogenic strains of N. gonorrhoeae with piliated and nonpiliated phenotypes. To determine the impact of piliation on the cellular status, we examined the expression of activation markers, cellular proliferation, and the production of cytokines after infection. The activation marker CD69 showed significantly increased expression on cells infected with the piliated strain, and this expression was dependent on costimulation of the T-cell receptor. Infection with piliated gonococci also altered T-cell proliferation and influenced the production of the regulatory cytokine interleukin-10. PilC, the putative pilus adhesin, was also observed to influence cellular activation but had no impact on the proliferation of cells further indicating that pilus-mediated adhesion is important in gonococcal stimulation of CD4+ T cells. These results show that the piliation status of gonococci influences CD4+ T-cell activation and that the adhesion mediated by pilus components aids in the regulation of the T-cell response to N. gonorrhoeae.     

Homology of cryptic plasmid of Neisseria gonorrhoeae with plasmids from Neisseria meningitidis and Neisseria lactamica.

DNA probe hybridisation was used to examine the relation between the cryptic plasmid from Neisseria gonorrhoeae and plasmids carried by pharyngeal isolates of Neisseria meningitidis and Neisseria lactamica. The complete gonococcal cryptic plasmid and HinfI derived digestion fragments subcloned into Escherichia coli were used to probe Southern blots of plasmid extracts. Homology was found to a plasmid of approximate molecular weight 4.5 kilobase pairs (Kb) but not to plasmids of less than 3.2 Kb or 6.5 Kb. Eleven of 16 strains of N meningitidis and two of six strains of N lactamica carried plasmids that showed strong hybridisation with the 4.2 Kb gonococcal plasmid. Hybridisation of plasmids from non-gonococcal species of neisseria with the gonococcal cryptic plasmid indicates that caution should be taken when using the cryptic plasmid as a diagnostic probe for gonorrhoea.     

Loss of antibody activity in human immunoglobulin A exposed extracellular immunoglobulin A proteases of Neisseria gonorrhoeae and Streptococcus sanguis.

Immunoglobulin A (IgA) proteases are extracellular enzymes elaborated by Neisseria gonorrhoeae, N. meningitidis, and Streptococcus sanguis. These enzymes each cleave human IgA1 at a critically situated prolyl-threonyl peptide bond to yield Fab alpha and Fc alpha fragments. To study their effect on the antibody activity of human IgA, we enzymatically digested a group of five human IgA monoclonal immunoglobulins with high-titer rheumatoid factor or cold agglutinin activity and human serum macroamylase, an amylase-IgA complex. In contrast to four control IgM rheumatoid factor monoclonal proteins, whose activity was unaffected by enzyme, gonococcal and streptococcal IgA proteases caused prompt, major reductions of IgA antibody activity to negligible levels and converted macroamylase activity to amylase of normal size, as determined by molecular sieve chromatography. In addition, both enzymes promptly deagglutinated sensitized cells that had been aggregated by IgA rheumatoid factors, indicating that IgA bound to antigen is also susceptible to enzyme cleavage. Fab fragments of Iga protein Chr, a rheumatoid factor, showed essentially no antigen-binding activity despite the high titers observed with the parent protein. These studies emphasize the high degree of specificity of the microbial proteases for IgA and their potential for interfering with antibody activity in the IgA1 subclass.     

Model for invasion of human tissue culture cells by Neisseria gonorrhoeae.

A tissue culture model has been developed for studying the ability of Neisseria gonorrhoeae to invade eucaryotic cells. The cell line HecIB, a human adenocarcinoma endometrial cell line, was found to support gonococcal invasion. The bactericidal antibiotic gentamicin was used to kill those bacteria that had not entered the HecIB cells, allowing us to quantitate internalized bacteria. Kinetic studies showed an increase in the titer of gentamicin-protected gonococci at 4 h postinfection followed by a decrease; a second increase occurred after 6 h. The state of piliation did not affect the degree of invasion when the bacteria were spun down onto the monolayer. Gonococcal invasion was inhibited when the HecIB cells were preincubated with cytochalasin D before bacterial infection. N. lactamica was used as a negative control. No internalized N. lactamica cells were observed by electron microscopy. Electron microscopy documented the intracellular location of the gonococci in HecIB cells and the eventual destruction of the invaded HecIB cells. After 24 h, clusters of gonococci encased in a matrix of cell debris were observed.