False Agglutination

FALSE AGGLUTINATION (spontaneous), a condition of bacteria causing them to precipitate not only in the presence of immune serum (see Agglutination), but also in normal serum or in physiological saline. False agglutination is frequently observed with cultures used for the Widal reaction. Typhoid and other pathogenic bacteria of the intestinal group freshly isolated from patients agglutinate well with immune serum and do not agglutinate with physiological saline; however, upon preservation on nutrient media over time, they begin to exhibit false agglutination. Sometimes such bacterial strains can be isolated directly from the organism of a sick person or a bacillus carrier. The phenomenon of false agglutination was first studied by Nicolle (1892-1902). He succeeded in inducing the capacity for autoagglutination in typhoid bacteria by cultivating them in immune serum. Savage (1905) achieved the same goal by cultivating them in the presence of weak solutions of disinfectants. A large number of facts characterizing the properties of spontaneously agglutinating bacteria were gathered between 1898 (Nicolle's first work) and 1921. In that year, Arkwright's work on the regular variation of intestinal bacteria was published; Hadley (1927) gave this biological law the name of bacterial dissociation. According to the theory of dissociation, in the final stage of bacterial development, conventionally designated by the letter R (from the word Rough), bacteria partially lose the capacity for specific agglutination, acquire the property of autoagglutination, and become 'serological cosmopolitans' (Schütze). The R-type of bacteria changes gradually and in its terminal forms completely loses the capacity for agglutination. The loss of the specific properties of bacteria depends on the loss of the hapten (the carbohydrate group of the antigen). According to d'Herelle, bacteriophage acts as the primary factor in the process of transformation of the specific (S) type of bacteria through an intermediate type (O) into the unspecific (R) type. The reverse transformation of a spontaneously agglutinating culture into a specifically agglutinating one is possible if a certain amount of hapten is present in the bacteria. Its regeneration and the return of specificity occur when the R-type of bacteria is cultivated in broth with immune serum for the same type (Hadley). When a culture of the R-type is cultivated in bile after 3-4 subcultures, a dissociation process is frequently observed with the formation of smooth-type (S) colonies capable of specific agglutination (Klyueva). Upon parenteral infection of laboratory animals with large doses of weakly virulent R-type bacteria that agglutinate spontaneously, it is possible to isolate S-type bacteria that agglutinate specifically from the organism of the deceased animal. Through such pathways, it is possible for laboratory purposes to restore the capacity of bacteria to agglutinate specifically.

Bacterial dissociation and false agglutination play a significant role in laboratory diagnostics, as aging laboratory cultures or certain strains isolated from carriers can produce false-positive reactions, confounding the identification of pathogens such as the typhoid bacillus. Recognizing these dissociated forms is essential for maintaining accurate diagnostic standards in bacteriological practice.