Staphylococcus saprophyticus is responsible for up to 26 percent of urinary tract infections reported in young sexually active women. The risk factors for acquiring S. saprophyticus infection are not clear. Risk factors for acquiring a urinary tract infection from coliform bacteria are better understood and include the use of vaginal spermicide, spermicide-coated condoms or contraceptive diaphragms. Fihn and associates conducted a population-based, case-control study to determine if the same factors might predispose women to acute urinary tract infections caused by S. saprophyticus.

The case group comprised 96 sexually active women who had been diagnosed with a urinary tract infection caused by S. saprophyticus in the previous month. They were matched with 629 sexually active women who served as control subjects. Among the study population, condoms were the most common method of contraception and protection from sexually transmitted disease. In the case group, condoms were used during the previous year by 71 percent of the women and during the previous month by 53 percent. In the control group, condoms were used during the previous year by 31 percent of the women and during the previous month by 19 percent. Patients in the case group were slightly younger than patients in the control group and were significantly more likely to be unmarried, to have had multiple partners during the previous year and to have had frequent sexual intercourse and a history of urinary tract infections.

Exposure to spermicide-coated condoms during the previous month was associated with a statistically significant risk of urinary tract infection caused by S. saprophyticus, compared with no exposure to any type of condom. When women were exposed to even a lubricated condom, the risk of urinary tract infection was modestly increased. The risk of urinary tract infection associated with a spermicide-coated condom was highly significant. With more frequent use of spermicide-coated condoms during the prior month, the risk of acquiring a urinary tract infection with S. saprophyticus rose dramatically. The risk of urinary tract infection did not extend to exposure to uncoated condoms. This finding suggests that most of the excess risk of urinary tract infection among condom users was related to exposure to nonoxynol 9. There was no increased risk of urinary tract infection associated with S. saprophyticus among women who had used other contraceptive methods such as foam or jelly.

The authors conclude that the risk of a young sexually active woman acquiring a urinary tract infection after being exposed to condoms coated with nonoxynol 9 was three times higher than the risk for sexually active women who did not use coated condoms. The study suggests that vaginal spermicides damage normal vaginal flora in a manner that promotes colonization with S. saprophyticus. This association is supported by the consistency of these findings with earlier studies regarding spermicide exposure and urinary tract infection. Women who use coated condoms and have recurrent urinary tract infections, particularly infections caused by S. saprophyticus, should be advised to consider using other methods of contraception.