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.     

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.     

Mutations affecting peptidoglycan acetylation in Neisseria gonorrhoeae and Neisseria meningitidis

Neisseria gonorrhoeae acetylates its cell wall peptidoglycan (PG) at the C-6 position on N-acetylmuramic acid. To understand the effects of PG acetylation on PG metabolism and release of PG fragments, we have made mutations in the genes responsible for PG acetylation. An insertion mutation in a putative PG acetylase gene (designated pacA) resulted in loss of PG acetylation as detected by a high-performance liquid chromatography-based assay. Sequence analysis of a naturally occurring non-acetylating strain revealed the presence of a 26-bp deletion in pacA. Introduction of the deletion mutation into wild-type gonococci resulted in lack of acetylation, and the phenotype was complemented by the addition of a wild-type copy of pacA at a distant location on the chromosome. Mutations were also introduced into three genes downstream of pacA. The gene directly downstream of pacA was required for acetylation and was designated pacB, whereas the next two genes were not required. Sequences highly similar to pacA and pacB were also found in N. meningitidis and N. lactamica strains, and an insertion in the meningococcal pacA eliminated PG acetylation. Phenotypic analyses of an N. gonorrhoeae pacA mutant did not show any decrease in lysozyme resistance or serum resistance, and the release of PG fragments during growth was unchanged. However, purified PG from the wild-type strain was significantly more resistant to the action of human lysozyme than was PG purified from the pacA mutant. Interestingly, the pacA mutant was more sensitive to EDTA, a compound known to trigger autolysis.     

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.     

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.     

Difficulties in differentiating Neisseria cinerea from Neisseria gonorrhoeae in rapid systems used for identifying pathogenic Neisseria species.

Neisseria cinerea and Neisseria gonorrhoeae may occur at the same body sites and may have similar colony morphologies. Ideally, systems used for rapid identification of N. gonorrhoeae should be able to differentiate N. cinerea from gonococci. We tested seven N. cinerea strains using the Gonochek II (Du Pont Diagnostics), Minitek (BBL Microbiology Systems), RapID-NH (Innovative Diagnostics, Inc.), RIM-N (American Microscan), and Phadebact (Pharmacia Diagnostics) systems. We found that the reactions produced by N. cinerea in Gonochek II, Minitek, and RapID-NH kits could be confused with the results produced by some strains of N. gonorrhoeae. The susceptibility of N. cinerea to colistin, its ability to grow on tryptic soy or Mueller-Hinton agar, and its inability to grow on modified Thayer-Martin medium help differentiate it from gonococci.     

Prosthetic valve endocarditis due to Neisseria skkuensis, a novel Neisseria species

We describe the first reported case of endocarditis due to Neisseria skkuensis. The organism from the blood cultures taken on admission day was identified initially as unidentified Gram-negative cocci by Vitek2. Finally, it was identified as Neisseria skkuensis by 16 rRNA gene sequence analysis.     

Neisseria sicca osteomyelitis.

Neisseria sicca was identified as the cause of vertebral osteomyelitis in a male patient who had previously suffered a nonpenetrating, traumatic back injury. The identifying characteristics and antimicrobial susceptibility patterns are presented for this rare human pathogen, which heretofore has not been reported as a cause of infection localized to bone.     

Genomics of Neisseria meningitidis

An important feature of disease caused by Neisseria meningitidis is the propensity to invade the meninges. Much progress has been made in our understanding of how this pathogen circumvents the physical properties of this cellular barrier. This review will address the new possibilities offered by the recent availability of meningococcal genome sequences.     

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.     

Identification of Regions of the Chromosome of Neisseria meningitidis and Neisseria gonorrhoeae Which Are Specific to the Pathogenic Neisseria Species

Neisseria meningitidis and Neisseria gonorrhoeae give rise to dramatically different diseases. Their interactions with the host, however, do share common characteristics: they are both human pathogens which do not survive in the environment and which colonize and invade mucosa at their port of entry. It is therefore likely that they have common properties that might not be found in nonpathogenic bacteria belonging to the same genetically related group, such as Neisseria lactamica. Their common properties may be determined by chromosomal regions found only in the pathogenic Neisseria species. To address this issue, we used a previously described technique (C. R. Tinsley and X. Nassif, Proc. Natl. Acad. Sci. USA 93:11109-11114, 1996) to identify sequences of DNA specific for pathogenic neisseriae and not found in N. lactamica. Sequences present in N. lactamica were physically subtracted from the N. meningitidis Z2491 sequence and also from the N. gonorrhoeae FA1090 sequence. The clones obtained from each subtraction were tested by Southern blotting for their reactivity with the three species, and only those which reacted with both N. meningitidis and N. gonorrhoeae (i.e., not specific to either one of the pathogens) were further investigated. In a first step, these clones were mapped onto the chromosomes of both N. meningitidis and N. gonorrhoeae. The majority of the clones were arranged in clusters extending up to 10 kb, suggesting the presence of chromosomal regions common to N. meningitidis and N. gonorrhoeae which distinguish these pathogens from the commensal N. lactamica. The sequences surrounding these clones were determined from the N. meningitidis genome-sequencing project. Several clones corresponded to previously described factors required for colonization and survival at the port of entry, such as immunoglobulin A protease and PilC. Others were homologous to virulence-associated proteins in other bacteria, demonstrating that the subtractive clones are capable of pinpointing chromosomal regions shared by N. meningitidis and N. gonorrhoeae which are involved in common aspects of the host interaction of both pathogens.     

Neisseria meningitidis B vaccines

Invasive infections caused by Neisseria meningitidis are a serious public health problem worldwide and have a heavy economic impact. The incidence of invasive disease due to Neisseria meningitidis is highly variable according to geographical area and serogroup distribution. Since the introduction of vaccination programs with conjugated vaccine C in children and adolescents, most cases of invasive meningococcal disease in developed countries have been caused by meningococcus B. It is important to underline that invasive meningococcal disease will not be controlled until safe and effective vaccines for meningococcal B are available and widely used. The aims of this article are to describe the most recent developments in meningococcal B vaccines and to discuss how these vaccines can contribute to containing meningococcal disease.     

The phenotypic relationship of Neisseria polysaccharea to commensal and pathogenic Neisseria spp

Eight of 22 non-capsulate strains of Neisseria meningitidis previously isolated from primary school children were re-identified as N. polysaccharea by aminopeptidase reactions and polysaccharide production. N. polysaccharea was not identified amongst 91 non-capsulate strains of N. meningitidis isolated from adults attending the Genito-urinary Medicine clinic, Westminster Hospital, London. The biochemical reactions of N. polysaccharea strains were similar to those of N. lactamica and N. gonorrhoeae, but N. polysaccharea could be distinguished from these organisms by examination of beta-galactosidase activity, carbohydrate reactions and polysaccharide production. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed closer similarity of N. polysaccharea to N. lactamica than to the pathogenic Neisseria spp. An additional finding was variation in the position of one of the major proteins of N. lactamica in the 34-39-Kda region.