A random selection of 25 strains isolated during an epidemic caused by serogroup A Neisseria meningitidis in Sudan (1988), 3 preepidemic meningococcal strains (1985), and 26 serogroup A strains isolated from sporadic cases of meningitis in Sweden (1973 to 1987) were assessed for multilocus enzyme genotypes (ETs), DNA restriction enzyme patterns, outer membrane proteins, lipopolysaccharides, pilus formation, and antibiograms. All of the 25 Sudanese epidemic isolates and 22 of the Swedish strains were of the same or closely related ETs (ETs 3, 4, and 5), corresponding to clone III-1, which has been responsible for two pandemic waves in the last three decades. The earlier pandemic involved Scandinavia, and the last one caused an outbreak during the pilgrimage to Mecca, Saudi Arabia (August 1987), spreading to Sudan, Chad, and Ethiopia. The three Sudanese preepidemic isolates (1985) were clone IV-1 (sulfonamide susceptible), which has been resident in the African meningitis belt for the last 25 years. The uniformity of clone III-1 strains (all sulfonamide resistant) from Sudan and Sweden was confirmed by DNA restriction enzyme patterns. ETs 3, 4, and 5 from Sudan and Sweden had 86 to 100% similarity to a Swedish clone III-1 reference strain, whereas ETs 1, 2, 6, and 7 showed 50 to 80% similarity. Class 1 protein for clone III-1 showed serosubtype antigens P1.9 and P1.x, whereas ET6 strains (clone IV-1) had serosubtype P1.7. Lipopolysaccharides were variable in the Sudanese and Swedish strains. Pili were expressed in all clone III-1 isolates from Sudan and Sweden but in none of the clone IV-1 isolates (Sudan, 1985).
In 1979 an indirect haemagglutination test (gonococcal antibody test) using gonococcal pilus antigen replaced the gonococcal complement fixation test as our routine procedure to show gonococcal antibodies. In the diagnosis of current gonorrhoea the sensitivity of the gonococcal antibody test was far superior to that of the gonococcal complement fixation test (about 55% versus 9% for first episode gonorrhoea). To evaluate the usefulness of the test result the following population groups were studied: 1376 patients undergoing medical examination for gonorrhoea (386 had gonorrhoea), 1384 healthy people aged 15-65, 54 patients with meningococcal disease, 30 children with respiratory tract infection, and 254 patients with evidence of various diseases other than neisserial infections that might be associated with symptoms of arthritis. These investigations showed that (1) non-specific positive gonococcal antibody test results occur rarely, (2) at least half the people who have had gonorrhoea remain seropositive (with titres of 1/40 to 1/160), and (3) a positive test result is more significant the younger the patient and the higher the titre. For younger people a positive test result should always be followed up by bacteriological examination; in all age groups titres of 1/320 or more should indicate medical examination for current gonorrhoea.
Oral surfaces are bathed in secretory antibodies and other salivary macromolecules that are potential inhibitors of specific microbial adhesion. Indigenous Gram-positive bacteria that colonize teeth, including viridans streptococci and actinomyces, may avoid inhibition of adhesion by host secretory molecules through various strategies that involve the structural design and binding properties of bacterial adhesins and receptors. Further studies to define the interactions of these molecules within the host environment may suggest novel approaches for the control of oral biofilm formation.