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.

Plasmids in throat and genital isolates of meningococci.

Plasmids 1.6, 2.8, or greater than 40 megadaltons in size were found in one urethral and nine throat strains of meningococci. Throat meningococci are known to be heterogeneous in their aminopeptidase profiles. Their unexpected content of plasmids is further evidence of their difference from classic systemic strains. Although the 2.8 megadalton plasmid has some resemblance to the well known 2.6 megadalton gonococcal plasmid, restriction enzyme studies gave no evidence of identity. Possible sources of the plasmids are discussed.

The specificity of serum and local antibodies in female gonorrhoea.

Immunoblotting has been used to compare the specificity of serum and local IgG and IgA antibodies in 13 women with gonorrhoea and in 13 controls. The technique allowed the simultaneous detection of antibodies to the major outer membrane proteins I, II, and III, pili and lipopolysaccharide; antibodies to another antigen which is probably a 'carbohydrate' were also detected. Serum and local IgG and IgA were found to be produced to several antigens during gonococcal infections, although the quantity of antibody was greater in serum. There was little change in the specificity of serum antibodies whereas the local response to LPS and pili increased over the two week study period. Serum antibody to LPS was more often IgG than IgA. Sera contained antibodies to 'carbohydrate', pili and lipopolysaccharide (LPS) whilst the local response was largely to the latter two antigens. Antibody to the outer membrane proteins was rarely detected. Control sera, but not vaginal washings, contained IgG and IgA to the major antigens but the staining of the immunoblots was less intense than those from patient's sera suggesting quantitative differences.