An Investigation of Some Factors Influencing the Pathogenicity of Neisseria Meningitidis
The nasopharyngael carriage rate of Neisseria meningitidis among 639 school children in Ijede, Ikorodu, Lagos State was 6.2% (40/639). The proportion of male carriers 62.5% (25/40) was significantly higher than females (37.5%; 15/40 (P < 0.05). N. meaningitidis groups C and A were the most frequently isolated serogroups accounting for 40% (16/40) and 22.5% (9/40) of the isolates respectively. In-vitro assessment of the attachment of N. meaningitidis to human nasopharyngeal epithelial cells (NEC) dropped that meningococci of all serogroups attached in significantly higher numbers to NEC of infants (160/HDC) and children (164/NEC) than NEC from neonates, (115/NEC) adults (124/NEC) and elderly (109/NEC). Attachment of meningococci to NEC of males and females was not significantly different. N. meningitidis group C clinical strain attached significantly better to non-carrier NEC than to the NEC of group C meningococcal carrier. The cell free supernates of some strains of Escherichia coli, Staphylococcus aureus and vridans streptococci isolated from the upper respiratory tracts of meningococcal carriers and non-carriers were found to produce substances inhibitory to serogroups of menigococci in vitro. Purified meningococcal endotoxin, and heat-killed meningococcal inocula from both clinical and carrier isolates were lethal for 12 day old chick embryo on chorioallantotic vein and yolk sac inoculation. Experimental laboratory animals including day old chicks suckling mice and infant rats did not develop meningitis subsequent to inoculation with meningococci through various routes. The collective results of these studies suggest that N. meningitidis possesses numerous pathogenicity factors which may act in synchrony depending on various host factors to enable this organism to overcome host defence and cause life threatening infections.