Investigating the Epidemiology of Repeat Chlamydia trachomatis Detection after Treatment by Using C. trachomatis OmpA Genotyping

Abstract

RepeatChlamydia trachomatisdetection frequently occurs within months afterC. trachomatisinfection treatment. The origins of such infection (persistence versus reinfection from untreated or new partners) are varied and difficult to determine.C. trachomatisstrains can be differentiated by sequencing theompAgene encoding the outer membrane protein A (OmpA). We used OmpA genotyping to investigate the epidemiology of repeatC. trachomatisdetection after treatment inC. trachomatis-infected subjects seen at a sexually transmitted diseases clinic. Subjects were enrolled, tested forC. trachomatis, treated with azithromycin, and scheduled for a 6-month follow-up for repeatC. trachomatistesting. OmpA genotyping was performed onC. trachomatis-positive urogenital specimens obtained from patients at enrollment and follow-up. The enrollment visit OmpA genotypes forC. trachomatiswere determined for 162 subjects (92% female, 94% African American).C. trachomatiswas detected at follow-up in 39 subjects (24%). The OmpA genotype distribution at enrollment did not differ in those with versus those without repeatC. trachomatisdetection. Of the 35 subjects withC. trachomatisstrains genotyped at enrollment and follow-up, 7 (20%) had the sameompAsequence at both visits, while 28 (80%) had discordant sequences. A new sexual partner was reported more often in subjects with discordantC. trachomatisstrains than in those with concordant strains (13 [46%] versus 1 [14%];P= 0.195). Half of the subjects with discordantC. trachomatisstrains who reported sexual activity since treatment denied a new sexual partner; 62% of these subjects reported that their partner was treated. Our study demonstrates that most repeatC. trachomatisdetections after treatment were new infections with a differentC. trachomatisstrain rather than reinfection with the same strain. OmpA genotyping can be a useful tool in understanding the origins of repeatC. trachomatisdetection after treatment.