Epidemiologic and microbiologic correlates of Chlamydia trachomatis infection in sexual partnerships.

OBJECTIVES

To determine the frequency of Chlamydia trachomatis genital infection within sexual partnerships using highly sensitive polymerase chain reaction (PCR) amplification and to identify the variables that might modify transmission.

DESIGN

Cross-sectional study of sexual partnerships comparing in vitro culture and PCR amplification for C trachomatis.

SETTING

Two outpatient sexually transmitted disease clinics.

PARTICIPANTS

Four hundred ninety-four people in sexual partnerships attending sexually transmitted disease clinics.

MAIN OUTCOME MEASURE

Genital infection with C trachomatis.

METHODS

DNA sequencing was performed to examine specific genotypes within and between partnerships. Cross-sectional analysis was performed to determine characteristics associated with concordance or discordance of infection with partnerships.

RESULTS

Cultures were positive for C trachomatis in 8.5% of males and 12.9% of females (P=.03). Using PCR, more infections were identified both in males (14.2%) and in females (15.8%), and the difference in infection rates analyzed by sex was no longer significant. In 20.4% of 494 couples, at least 1 partner had PCR results positive for C trachomatis, with a concordant infection rate of 10.7%, significantly higher than the 5.5% concordant infection rate demonstrable by culture (P<.01). Male-female and female-male transmission frequencies were equal (68%). The nucleotide sequences of the major outer membrane protein gene products were identical and unique for each of 15 culture-negative, PCR-positive concordant partnerships. In concordant infections, factors associated with infection in female partners were age less than 20 years, more than 1 partner in the past 6 months, and cervical ectopy greater than 25%.

CONCLUSIONS

Using PCR, the frequency of chlamydia transmission by infected males and females was nearly identical. The high rate of concordant infection, high frequency of infection among asymptomatic individuals, and high frequency of transmission regardless of sex underscore the importance of routine screening for chlamydia in both males and females, along with provision of treatment to all sexual partners of chlamydia-infected individuals.