International Journal of STD & AIDS 2002; 13 (Suppl. 2): 19± 22
Prevalence and persistence of asymptomatic Chlamydia trachomatis infections in urine specimens from Danish male military recruits Adriaan J C van den Brule 1, Christian Munk2, Jeanette F Winther2, Susanne KruÈger Kjaer2, Hans O Jù rgensen3, Chris J L M Meijer1 and Servaas A MorreÂ1 1Department
of Pathology, Section of Molecular Pathology, Vrije Universiteit Medical Center, Amsterdam, The Netherlands, 2Danish Cancer Society, Institute of Cancer Epidemiology, Copenhagen, and 3Defence Medical Training Center, Gentofte, Denmark Summary: Danish male military recruits (n ˆ 388) were included in a follow-up study to investigate the prevalence and persistence of asymptomatic Chlamydia trachomatis infections. Urine specimens were collected at enrolment and after approximately six months. C. trachomatis was detected by polymerase chain reaction (Amplicor, Roche). Questionnaires were ® lled out concerning sexual behaviour and clinical symptoms. The prevalence of asymptomatic C. trachomatis in Danish male military recruits was 4.6% (18 out of 388). From ® ve C. trachomatis-positive men no follow-up sample was obtained. From the remaining 13 C. trachomatis-positive men four (31%) were treated for C. trachomatis between the two visits (outside the study protocol). Of the remaining nine men, one cleared the infection and eight men (89%) had a persistent infection. The number of lifetime sexual partners was associated with the presence of C. trachomatis at enrolment. Although based on small numbers, this follow-up study shows, in contrast to women with asymptomatic C. trachomatis infections, a high percentage of C. trachomatis persistence in asymptomatically infected males. Keywords: prevalence, persistence, C. trachomatis infection, clearance
INTRODUCTION
are reported in less than 4% of C. trachomatis-infected men 2. Eggert et al.3 found a correlation between the presence of C. trachomatis antibodies in males and tubal factor infertility in their female partners. The infections among men will mostly affect their female partners, leading to severe consequences such as pelvic in¯ ammatory disease, ectopic pregnancy and tubal infertility in 8± 20% of the infected women4. Despite the obvious importance of this microorganism, little is known about the natural course of asymptomatic C. trachomatis infections. This is one major issue raised by Wilson and Jungner 5 in their 10 prerequisites for screening. Elucidation of the duration of infection is essential for disease modelling, as recently stated by Golden et al.6 Among women, clearance of asymptomatic C. trachomatis infections has been reported, but the number of women who cleared the infection differs depending on the detection techniques, such as cell culture and enzyme immunoassay. No such studies have yet been reported in men.
Chlamydia trachomatis is the most prevalent sexually transmitted agent in the USA and Europe and has an aetiologic role in non-gonococcal urethritis in men. The complications due to C. trachomatis infections in men are less frequent and less severe than in women. In women, 70± 80% of C. trachomatis infections are asymptomatic1, whereas only 25± 30% of the infections in men are asymptomatic. However, more recent studies using sensitive DNA ampli® cation techniques show that up to 50% of C. trachomatis infections are asymptomatic in men 1. The most frequent complications of an untreated C. trachomatis-urethritis, epididymitis and prostatitis, Correspondence to: Dr A J C van den Brule, Department of Pathology, Section of Molecular Pathology, Vrije Universiteit Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands E-mail:
[email protected] 19
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Nucleic acid ampli® cation techniques have increased the number of detected asymptomatic C. trachomatis infections by 35%. However, the clinical relevance of the additional detection of asymptomatic C. trachomatis infections is largely unknown. The use of urine specimens instead of inconvenient urethral swabs has greatly increased the participation rates in studies of asymptomatic C. trachomatis infections among men 7. In a followup study, we have investigated the prevalence and persistence of asymptomatic C. trachomatis infection in young men in relation to sexual behaviour and clinical symptoms.
Amplicor assay, or samples that were C. trachomatisnegative while the proceeding sample was C. trachomatis-positive, were subjected to an in-house PCR using puri® ed DNA from the original urine specimens. The in-house PCR and the DNA isolation were performed as described previously8± 11.
MATERIALS AND METHODS
RESULTS
Study population and clinical specimen collection
At enrolment, 18 (4.6%) out of 388 male military recruits had an asymptomatic C. trachomatis infection. After approximately six months, 322 men were included in the follow-up visit. No statistically signi® cant difference was found between the C. trachomatis-negative men and C. trachomatispositive men with regard to the percentage of nonresponders. In ® ve of the 18 men who were positive at enrolment no follow-up sample was obtained (Table 1). Four of the men who had cleared the infection reported that they (and their partners) had been treated for C. trachomatis outside the study protocol during the follow-up period. Of the nine remaining men who were C. trachomatispositive at ® rst examination, eight (89%) also had a C. trachomatis infection at the second examination, whereas only one man had cleared the infection. The incidence of chlamydial infection among 309 C. trachomatis-negative men included in the followup was low as only one man became C. trachomatispositive (data not shown in Table 1). Table 2 gives selected baseline characteristics among the 388 male military recruits. No difference according to C. trachomatis status at enrolment was found for C. trachomatis treatment in the six months prior to inclusion. The C. trachomatis-positive men reported a higher lifetime number of partners than C. trachomatis-negative men: among those testing positive, 67% reported to have had more than nine partners, whereas this only applied to 22% of the
Between September and October 1998, 388 male Danish military recruits, aged 18± 29 years (93% between 19 and 22 years) were included in a follow-up study of 5± 8 months. During the medical check-up at enrolment in the army, participants were requested to collect a ® rst void urine sample. After approximately six months, a second urine specimen was collected (March± April 1999). At both examinations a self-administered questionnaire was completed providing data about age, life-time number of sexual partners, history of C. trachomatis infection, treatment for C. trachomatis in the last six months prior to inclusion, C. trachomatis treatment during follow-up, C. trachomatis treatment of partner during follow-up, and clinical symptoms or a urogenital infection (dysuria, frequent urination, urethral discharge). All urine specimens were transported by plane at room temperature to a laboratory in The Netherlands (University Hospital Vrije Universiteit, Amsterdam) for C. trachomatis testing by polymerase chain reaction (PCR) (Amplicor, Roche). In this study, an asymptomatic infection was de® ned as having a C. trachomatis infection without having contacted a physician for possible complaints related to the infection. Medical ethics
Statistical analyses For statistical testing the Chi-square test or twotailed Fisher’s exact test were used where appropriate. A P-value of P ˆ 0.05 or less was considered statistically signi® cant.
The Medical Ethics Committee covering the study area approved the study design. Informed consent was obtained from all participants. At the end of the study all C. trachomatis-positive men were treated with anti-chlamydial antibiotics.
Table 1. Chlamydia trachomatis (CT) status after six months followup among 18 CT-positive men at enrolment
C. trachomatis detection
CT status
No.
All urine specimens were tested for C. trachomatis by PCR according to the instructions of the manufacturer (Amplicor, Roche Diagnostic Systems, Basel, Switzerland). An internal control to monitor inhibition for ampli® cation was introduced into each ampli® cation reaction. To assess the true C. trachomatis-negative status of urine samples, those with either inhibition in the
Persistent infection # Spontaneous clearance Treatment-related clearance* No follow-up
8 1 4 5
#Persistent:
CT positive at tˆ 0 months and at tˆ 6 months *Treated for CT outside the study protocol
van den Brule et al. Asymptomatic C. trachomatis infections in Danish men
Table 2. Baseline characteristics among 388 male military recruits in Denmark according to Chlamydia trachomatis (CT) status at enrolment CT positive (n ˆ18) n Self-reported treatment for CT within six months prior to enrolment
n
(%)
0 (0)
2 (0.5)
0 (0) 6 (33) 8 (44) 3 (17) 1 (6)
191* (52) 99 (27) 40 (11) 18 (5) 22 (6)
Life-time number of sexual partners 0± 4 5± 9 10± 14 15± 19 20‡ Men with unspeci® c urological or urogenital complaints Dysuria Urethral discharge Dysuria and frequent urination
(%)
CT negative (n ˆ 370)
2 (11)
32
(8.6)
2 (11)
9 3 2
(2.4) (0.8) (0.5)
± ±
*19 persons had never had sexual intercourse
C. trachomatis-negative men (OR 7.25, 95% CI: 2.6± 20). There was no statistically signi® cant difference in the percentage of C. trachomatis-positive men that reported any urogenital complaints (overall or speci® c) as compared to the C. trachomatis-negative men (Table 2). Finally, a self-reported C. trachomatis infection in the past was not associated with C. trachomatis positivity at enrolment (2/18 versus 11/370). DISCUSSION In a 5± 8 months follow-up study among a low C. trachomatis prevalence population of male Danish military recruits we showed that a high percentage of asymptomatic C. trachomatis infections in men persisted. These data concerning the duration of chlamydial infections are essential for disease modelling, especially since the clinical relevance of the additionally detected asymptomatic C. trachomatis infections, as assessed by DNA ampli® cation assays, is still unknown. In this male population, 4.6% had an asymptomatic infection based on C. trachomatis-DNA detection by PCR in mailed urine specimens. The prevalence in the investigated population is comparable to the prevalence of 4.1% found recently by Stary et al.12 using PCR in asymptomatic male military recruits, although the mean age in that particular group was slightly higher (20± 37 years old), and urine specimens were used directly without prior mailing to the laboratory. However, the approach of using mailed urine specimens has recently been shown by our group to be reliable8. To date, there is no information concerning the natural course of asymptomatic C. trachomatis infections in men. Symptomatic C. trachomatis infection
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in men has been studied up to 56 days with a clearance rate of 15%13. Our study is the ® rst to examine persistence and clearance of asymptomatic C. trachomatis infections in males with a follow-up of approximately six months. We showed that eight out of nine (89%) of the men had a persistent C. trachomatis infection. In ® ve of the men who were C. trachomatis-positive at enrolment no follow-up samples were obtained. Even if we hypothesize that these men all became C. trachomatis-negative at follow-up, the persistence rate would still be high (8/17ˆ 57%). A study focusing on the detection of C. trachomatis in semen showed that part of the C. trachomatispositive semen samples remained positive over a period of two years, suggesting persistence of C. trachomatis in men for long periods of time14, although reinfection in that study could not be ruled out. McCormack et al.15 showed in 1979 for the ® rst time, using culture and serology, that C. trachomatis infections could clear spontaneously in women. They reported a clearance rate of 50% after 16± 17 months. To study the factors associated with a C. trachomatis infection, questionnaire information was obtained at enrolment and after approximately six months of follow-up. The lifetime number of sexual partners was associated with C. trachomatis positivity at enrolment. This association has also been found for asymptomatically infected Danish women10. Neither non-speci® c urogenital complaints (self-reported) nor speci® c urogenital complaints were associated with having a C. trachomatis infection. Thus, these self-reported complaints were not useful for selective screening purposes and identi® cation of potential high-risk groups. Four men (31%), initially C. trachomatis-positive, reported to have received anti-chlamydial antibiotic treatment during follow-up. Several explanations for receiving chlamydial speci® c antibiotics are possible: 1) the men became symptomatic and contacted a physician for treatment, 2) their partners became symptomatic and the men were treated together with the women, 3) the women were asymptomatically infected and were found to be positive during a routine medical check-up (pregnancy, insertion of an intrauterine device) and were treated together with their men. Since in men more symptomatic C. trachomatis infections are reported, these four cases most likely converted to a symptomatic infection for which a physician was contacted. In conclusion, although based on small numbers, this study showed a high rate of persistence of asymptomatic C. trachomatis infections in men in contrast to asymptomatic C. trachomatis infections in women (see Morre et al, this supplement, pp. 12± 18). Nearly a third of the initially asymptomatic C. trachomatis infections were treated during follow-up. However, large-scale studies are needed to provide more accurate estimates of the persistence rates of asymptomatic C. trachomatis infections in men.
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International Journal of STD & AIDS
Volume 13
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Acknowledgements: This work was partly supported by ZON (Prevention Fund) grants 28-1182-1 and 28-2705. We are very grateful to Mette S Jù rgensen, Bente B Jensen and other staff at the participating barracks for their co-operation. We thank A Joan P Boeke for critically reading the manuscript.
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