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A Study of Surface Proteins, Other Adhesins and Iron Acquiring Mechanisms in the Pathogenesis of Neisseria gonorrhoea strains Isolated from STD Patients in Ethiopia

Aberra Geyid


Background information: Neisseria gonorrhoea is one of the most world wide prevalent Gram-negative diplococci bacteria causing the disease called Sexually Transmitted Disease on humans. Its stages of infection involve, first, colonization of columnar epithelial cells of mucosal surfaces; then an inflammatory response is elicited; and finally, the phagocytosis of the organisms by PMNs results in the formation of purulent discharges where the PMNs are found accumulated in it. The antigenic composition of N.gonorrhoea is complex with three major classes that are associated with the surface layers, namely, the pilus protein antigens, the polysaccharide component of cell wall and the outer membrane protein constitution. The pathogenicity determinant factors of N.gonorrhoea have been proved to include: Colonial Morphology which indicates that the virulence factors are based on the five major colony forms designated as T1, T2, T3, T4 and T5, indicating differences in surface antigens, virulence and in colony appearances; and, the Pili are the other pathogenesis determinant factors that are functioning by having adherence to the mucosal cell surface and serving as conjugal transfer of genetic material. It has been observed that piliated bacterial strains are resistant to phagocytosis, giving inefficient digestion ability to the macrophages compared to nonpiliated strains. Thus, types T1 and T2 are most virulent to humans because they are the piliated (fimbriated) strains.

The Ethiopian situation in relation to gonococcal infections indicates that it is known to be highly prevalent among both sexes of most age groups. However no work has been conducted to assess the prevalence of the different virulence factors of N.gonorrhoeae strains.

Objective : The aim of this study was thus to assess the prevalence of all the essential surface antigens as virulence factors of N.gonorrhoeae among the most vulnerable group of individuals for the infection and try to assess and recommend the possibility of getting important surface components to serve as vaccine candidates against gonococcal infections.

Patients & methods: a total of over 300 STD male and female patients from three study sites, Addis Ababa, Nazareth, and Awassa, were used as study subjects by collecting urogenital specimen after their clinical examination. The specimens were then used for the isolation of the N.gonorrhoea strains that were identified for their virulence types, tested for their antimicrobial sensitivity patterns and determined their surface antigenic components for the most prevalent virulence factors using haemagglutination and other detection assay methods.

Results: It was found that out of the total 335 specimens, N.gonorrhoea strains were isolated in 59% positive rate from males compared to the 43% positive rate was obtained from the females. The sensitivity pattern of these strains indicate that there were 19 different antibiogram patterns showing that only 12.3% were sensitive to all drugs while over 70% of the strains were resistant against more than two combined

drugs and above 90% of these multi-drug resistant strains showed to be PPNGs. Out the total N.gonorrhoea isolates, 200 were tested for their haemagglutination and Iron-binding protein production properties and 35% of them were found to be Mannose Resistant Haemagglutinating (MRHA) strains while 20% were Mannose Sensitive Haemaggluintating (MSHA) strains when tested using the human AB blood types of. By the use guinea pig blood cells this was found to be 15% MRHA and 25% MSHA strains. When tested for their iron-binding protein (IBP) production, the MRHAs were positive for IBPs while the MSHA were positive for this property in 10%. Finally, based on the results obtained conclusions and recommendations are given at the end of the paper.

[J Ethiopia Med Pract. 2002;4(1):14– 20]

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eISSN: 1560-1560