Several factors influencing the colonization of group B streptococci--rectum probably the main reservoir.

Women (1 268) attending a gynaecological clinic or a venereal disease clinic had positive cultures of group B streptococci from urethra in 27.8% and from rectum in 29.4%. The colonization rate was highest in patients from the venereal disease clinic (p less than 0.001). In a study of 405 of the females at different parts of the menstrual cycle group B streptococci were detected during the last half of the cycle in specimens from cervix in 18%, from urethra in 29% (p less than 0.005), and from rectum in 35% (p less than 0.001). The correlation between contraceptive methods and isolation of group B streptococci was investigated for 435 women. Females with intrauterine devices but not those using oral contraceptives had a significantly increased colonization rate genitally. The colonization rate of group B streptococci was also studied in 271 women using sanitary tampons and 129 women using sanitary towel. Those using tampons were significantly more often colonized. Cultures for Neisseria gonorrhoeae were performed from 380 patients but no correlation between N. gonorrhoeae and group B streptococci was found. The study supports the view that rectum and not the genito-urinary tract is the main reservoir of group B streptococci in females, that genital colonization mainly represents contamination from the gastrointestinal flora and sexual transmission is only one of many factors influencing the colonization rate.