Background:
Repeat Chlamydia trachomatis (CT) infections are often attributed to the same sex partner as the source of the original infection who may have been inadequately treated, though the actual contribution of this source to the overall frequency of repeat infections has not been empirically evaluated.

Objective:
To estimate the relative contributions of same (inadequately treated) and different (either the patients or the partners) sex partners in the burden of repeat CT infections.

Method:
Women diagnosed with CT were enrolled in a longitudinal study. Data collection included interview and genotyping of CT DNA.

Result:
A total of 118 women were followed during 2005-2007. Mean age was 20.7 years (SD 4.0) and the sample was ethnically diverse (63% black, 18% Latina). At 4-month follow-up, 23 women (19%) had repeat infections and 7 had viable CT DNA for genotyping from both visits (treatment prior to enrollment often precluded collecting a diagnostic specimen). Five women (71%) had different genotypes at baseline and follow-up (one each of the following pairs: J-E, E-J, G-D, D-E, I-J). Two of these women reported new sex partners or multiple partners, and one reported her partner was not monogamous. One woman had the same genotype at both infections (E), and one woman was co-infected with two genotypes at baseline and had one genotype at follow-up (D/E-E).

Conclusion:
Though based on a small sample, these results show that new sources of infection from different sex partners may contribute to at least 70% of repeat infections.

Implications:
While ensuring partner treatment for CT diagnoses remains important for partners' health and reducing further spread, reducing the burden of repeat CT infections will require addressing risk associated with additional sex partners. Prevention counseling should focus on communication and condom use with all sex partners, and the possible misperception of partner monogamy.