Studies on the virulence of Neisseria gonorrhoeae. I. Relation of colonial morphology and resistance to phagocytosis by polymorphonuclear leukocytes.

Colonial varieties of Neisseria gonorrhoeae that are associated with virulence, types 1 and 2, were more resistant to phagocytosis by rabbit exudative polymorphonuclear leukocytes than colonial types of lesser virulence, types 3 and 4. Type 1 bacteria were resistant and type 4 gonococci were susceptible to phagocytosis by human polymorphonuclear leukocytes. Recent local type 1 isolates were similar in resistance to type 1 organisms of a standard laboratory strain (F62). Living and Formalin-treated, heat-killed, type 1 gonococci were equally resistant to phagocytosis. The antiphagocytic property of virulent colonial types was independent of leukotoxic action. Phagocytosis of both type 1 and type 4 gonococci by rabbit and human leukocytes was bactericidal. Rabbit leukocytes were superior to human leukocytes in killing gonococci. The results suggest that N. gonorrhoeae has virulence properties similar to those of extracellular bacterial pathogens, i.e., virulence is associated with antiphagocytic properties.