Proof of adherence of group B streptococci (GBS) to human and bovine vaginal epithelial cells and to bovine cells of milk cisternae of the mammary gland was employed as a criterion determining the possibility of colonization of these organs with GBS, or as another method of testing the transfer of GBS between man and cattle. GBS of both human and animal origin adhered to human epithelial cells in a similar way. On the other hand, a significantly stronger adherence of bovine GBS to vaginal epithelial cells and cells of milk cisternae of cattle was found than of human GBS. Thus the direction of colonization - animal is more probable than the opposite way. Neither in animal nor in human strains a correlation between the equipment of strains with type antigens and intensity of adherence could be found.

Adhesion of group B streptococci to human epithelial vaginal and buccal cells proceeded in three phases which differed qualitatively. Maximum adhesion took place within 10 min of interaction, during the second phase (10-15 min), the percentage of adherent cells decreased significantly (P less than 0.05) whereas during the last phase the decrease became stabilized at a value which differed significantly from the maximum (P less than 0.01). The cause of variability in the number of positively reacting cells in relation to the exposure time is discussed.

Hydrogen ion concentration in a medium in which the adherence of group B streptococci to vaginal and buccal cells takes place, significantly influences the reaction intensity. At physiological pH, group B streptococci adhere significantly more weakly than at pH 5.5 to buccal epithelia, and at pH 7.2 to vaginal epithelia. Thus at nonphysiological pH values the percentage of adherent cells is markedly higher.