Chlamydia trachomatis incidence and re-infection among young women--behavioural and microbiological characteristics.
BACKGROUND
This study aimed to estimate rates of chlamydia incidence and re-infection and to investigate the dynamics of chlamydia organism load in prevalent, incident and re-infections among young Australian women.


METHODS
1,116 women aged 16 to 25 years were recruited from primary care clinics in Australia. Vaginal swabs were collected at 3 to 6 month intervals for chlamydia testing. Chlamydia organism load was measured by quantitative PCR.


RESULTS
There were 47 incident cases of chlamydia diagnosed and 1,056.34 person years of follow up with a rate of 4.4 per 100 person years (95% CI: 3.3, 5.9). Incident infection was associated with being aged 16 to 20 years [RR = 3.7 (95%CI: 1.9, 7.1)], being employed [RR = 2.4 (95%CI: 1.1, 4.9)] and having two or more new sex partners [RR = 5.5 (95%CI: 2.6, 11.7)]. Recent antibiotic use was associated with a reduced incidence [RR:0.1 (95%CI: 0.0, 0.5)]. There were 14 re-infections with a rate of 22.3 per 100 person years (95%CI: 13.2, 37.6). The median time to re-infection was 4.6 months. Organism load was higher for prevalent than incident infections (p<0.01) and for prevalent than re-infections (p<0.01).


CONCLUSIONS
Chlamydia is common among young women and a high proportion of women are re-infected within a short period of time, highlighting the need for effective partner treatment and repeat testing. The difference in organism load between prevalent and incident infections suggests prevalent infection may be more important for ongoing transmission of chlamydia.
CERSH Melbourne Medical School, University of Melbourne, Victoria, Australia. walker@unimelb.edu.au
Jennifer
J
Walker
Sepehr N
SN
Tabrizi
Christopher K
CK
Fairley
Marcus Y
MY
Chen
Catriona S
CS
Bradshaw
Jimmy
J
Twin
Nicole
N
Taylor
Basil
B
Donovan
John M
JM
Kaldor
Kathleen
K
McNamee
Eve
E
Urban
Sandra
S
Walker
Marian
M
Currie
Hudson
H
Birden
Francis
F
Bowden
Jane
J
Gunn
Marie
M
Pirotta
Lyle
L
Gurrin
Veerakathy
V
Harindra
Suzanne M
SM
Garland
Jane S
JS
Hocking
D000293:Adolescent; D000328:Adult; D001315:Australia / Q000453:epidemiology; D002690:Chlamydia Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000382:microbiology; D002692:Chlamydia trachomatis / Q000302:isolation & purification; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D015995:Prevalence; D012725:Sexual Behavior; D055815:Young Adult