Classification Immunology and Pathology

The importance of gonorrhea is measured not only by its considerable burden of acute disease and long-term consequences, but also by some of its extraordi nary biological characteristics. The virulence of the gonococcus rests in its ability to adhere to muscosal surfaces, to resist immunological defenses, to cause asymptomatic infection, and to resist antibiotic killing. These qualities have been important in the development of four major classification schemes based upon the following:

1. The presence or absence of pili (long, filamentous projections on the surface of the gonococcus), which determine adherence to mucosal cells. Their presence is, in turn, reflected in the size, shape, and opacity of gonococcal bacterial colonies, and forms the basis for the earliest classification scheme used.

2. The nutritional requirements of the gonococci. Typing of organisms based on their need for certain amino acids (auxotyping) has determined the presence of special strains that are more or less sensitive to antiobiotics, and that have a greater propensity to cause disseminated infection.

3. The antigenic structure of the gonococcal cell envelope, which provides a mechanism for classification (serovars). Serovars have been used, in conjunction with auxotyping, to show patterns of distribution and to link cases epidemiologically.

4. Susceptibility to antibiotics. Four transferable pieces of genetic material (plasmids) have been identified, which have helped in geographic localization of cases.

These systems for classification reflect the considerable pathogenetic repertoire available to the gonococcus. In contrast, the immunologic armamentarium of the host seems inadequate. Genital secretions may have some inhibitory effect on gonococci in vitro, but are not protective. Local immunoglobulin production has been demonstrated but may be counteracted by protease produced by the gonococcus. Serum antibody is usually demonstrable in previously infected persons, but resistance to serum killing is a typical feature of freshly isolated gonococci. Indeed the net result of studies to date simply reflects the time-honored observation that people may contract gonorrhea again and again. There is no apparent protective human immunity. The existence of asymptomatic infection, and the apparent immunologic tolerance of the host, may account in part for the ecological success of the gonococcus.

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