Determinants of co-colonization with group B streptococcus among heterosexual college couples

Epidemiology. 2002 Sep;13(5):533-9. doi: 10.1097/00001648-200209000-00008.


Background: Group B causes morbidity and mortality among newborns, pregnant women, and nonpregnant adults. Among adults, sexual and fecal-oral routes of transmission are hypothesized; this study addresses whether sexual transmission occurs.

Methods: Our outcome of interest was group B. From our investigation of the heterosexual transmission of urinary tract infections among college students at the University of Michigan, conducted in 1996-1999, we identified 120 couples in which one or both partners carried group B. Each partner completed a questionnaire regarding potential risk factors for colonization.

Results: Co-colonization with the identical group B strain (as determined by pulsed-field gel electrophoresis) occurred in 86% of the 57 co-colonized couples. When the male sex partner carried group B, 64% of female partners also were colonized; conversely, 49% of male partners of colonized females were colonized with identical strains. Among behaviors predicting co-colonization within the partnership, male-to-female oral sex was a risk factor among both women (odds ratio [OR] = 2.9; 95% confidence interval [CI] = 1.2-6.9) and men (OR = 2.5; CI = 1.1-5.6). First sex at age 20 years or older was associated with an increased risk among women (OR = 2.1; CI = 0.7-6.4) and among men (OR = 3.0; CI = 1.0-9.3), and four or more lifetime sex partners was associated with a decreased risk of co-colonization among women (OR = 0.6; CI = 0.2-1.5) and among men (OR = 0.4; CI = 0.2-1.0).

Conclusions: Among heterosexual college couples, sexual activity, particularly male-to-female oral sex, increases the risk of co-colonization with an identical group B strain. Future studies should evaluate the role of the pharynx and examine the effects of both bacterial characteristics and host response on transmission.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Anal Canal / microbiology
  • Bacteriuria
  • Female
  • Humans
  • Logistic Models
  • Male
  • Sexual Behavior*
  • Sexually Transmitted Diseases, Bacterial / microbiology
  • Sexually Transmitted Diseases, Bacterial / transmission*
  • Streptococcal Infections / transmission*
  • Streptococcus agalactiae* / isolation & purification
  • Urinary Tract Infections / microbiology
  • Urinary Tract Infections / transmission*
  • Vagina / microbiology