Chlamydial genital infections and laparoscopic findings in infertile women

Several studies have shown that previous chlamydial genital infection, reflected by serological markers, is strongly associated with tubal damage leading to tubal infertility. In 105 women undergoing laparoscopy, multiple samples were collected from the lower (urethra and cervix) and upper (endometrium, peritoneal fluid, tubal lumen) genital tract, in order to isolate Chlamydia trachomatis in cell culture. Chlamydia trachomatis was isolated from at least one site in 13 (30.9%) of 42 infertile women with tubal infertility, in 5 (12.1%) of 41 women with unexplained infertility, in 1 of 4 women affected by acute salpingitis and in 1 (5.5%) of 18 women with endometriosis or uterine malformations. The latter group was the control group. Thirteen (65%) of the 20 positive women harboured Chlamydia trachomatis in their upper genital tract alone and 16 women were positive in one or both tubes. Only one of the positive women showed laparoscopic signs of acute pelvic infection. Four of the 5 positive women with unexplained infertility harboured Chlamydia trachomatis in the tubal lumen. This study confirms that chlamydial infection is strongly associated with tubal damage. It suggests that cervical cultures are inadequate for excluding a tubal infection and that chlamydial colonization of the tubal mucosa is possible in the absence of symptoms and laparoscopic signs of active infection.     

Chlamydia trachomatis infections

Chlamydia trachomatis is the most common bacterial cause of sexually transmitted disease in the developed countries. The most important implications of genital chlamydia infections involve the reproductive health sequalae of upper genital tract infections in women: pelvic inflammatory disease, ectopic pregnancy, and infertility, infection by this organism is insidious, symptoms are absent or minor among most infected women and many man. This large group of asymptomatic and infectious persons sustains transmission within a community. This review discusses the epidemiology, of sexually transmitted chlamydial infections, the spectrum of clinical manifestations and their sequelae, the laboratory diagnosis of genital chlamydiasis, antibiotic treatment and prevention.     

Serological responses of patients with ectopic pregnancy to epitopes of the Chlamydia trachomatis 60 kDa heat shock protein

Clinical and histopathological correlations of immunoreactivity to Chlamydia trachomatis and to epitopes of the C. trachomatis 60 kDa heat shock protein (hsp60) among women with ectopic pregnancy were evaluated in a case-control study. Serological responses to 13 synthetic peptides corresponding to major epitopes of the chlamydial hsp60 were determined in 67 women treated for ectopic pregnancy and 45 women with uncomplicated pregnancy in utero. Plasma cell salpingitis was detected in 29 (43.3%) of the ectopic patients. Its presence correlated with antibodies to two hsp60 epitopes, encompassing amino acids 260-271 and 411-422 (P = 0.02). Antibodies to these two epitopes, along with five other epitopes, also correlated with peritubal adhesion formation in ectopic pregnant patients (P < 0.01). Antibodies to epitopes 260-271 and 188-199 also correlated with a history of pelvic inflammatory disease (PID; P = 0.05). Patients with ectopic pregnancy were also more likely than their intrauterine pregnant controls to have present anti-chlamydial immunoglobulin G (P < 0.005). Women positive for both C. trachomatis and hsp60 epitope antibodies had an increased prevalence over controls of salpingitis, pelvic adhesions or history of PID (P < 0.05). In contrast, patients who were positive for only C. trachomatis antibodies or only hsp60 epitope antibodies did not differ from antibody-negative patients in each of these categories.     

The association between Chlamydia trachomatis serology and pelvic damage in women with tubal ectopic gestations

OBJECTIVE: To determine whether pelvic damage is associated with positive Chlamydia trachomatis serology in women with tubal ectopic pregnancy. DESIGN: Cross-sectional retrospective study. SETTING: A prepaid health maintenance organization. PATIENTS: Two-hundred eighty-one women admitted with confirmed tubal ectopic pregnancy were interviewed for history of sexually transmitted diseases. Chlamydia serology was obtained for 135 subjects, and operative findings were available for 121 of these. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Pelvic damage, as determined by review of operative findings of the pelvis at the time of ectopic surgery. RESULTS: Pelvic damage was associated with positive chlamydia serology with an adjusted odds ratio of 4.2 (95% confidence interval: 1.8 to 9.7). Moderate and severe pelvic damage were more strongly associated with positive serology than mild damage. CONCLUSIONS: Women with ectopic pregnancies and antibodies to C. trachomatis are more likely to have damaged pelves than women with ectopic pregnancies without such antibodies. Prevention or early treatment of C. trachomatis infection may reduce pelvic damage and, therefore, reduce incidence of ectopic pregnancy.     

Antibody to chlamydial hsp60 predicts an increased risk for chlamydial pelvic inflammatory disease

To determine whether serum antibody to Chlamydia trachomatis antigens alters the risk of C. trachomatis pelvic inflammatory disease (PID), 280 female sex workers were prospectively evaluated over a 33-month period for incident C. trachomatis and Neisseria gonorrhoeae cervical infection and for clinical PID. At enrollment, women were tested for antibody to C. trachomatis elementary bodies by an indirect microimmunofluorescence assay and to recombinant chlamydial hsp60 (Chsp60) by an ELISA format. At each follow-up visit, women were tested for cervical chlamydial and gonococcal infection and were identified as having clinical PID if they complained of lower abdominal pain and were found to have uterine and adnexal tenderness on pelvic examination. The data demonstrate that antibody to Chsp60 predicts a 2- to 3-fold increased risk for C. trachomatis PID.     

Chlamydial infection in inducible nitric oxide synthase knockout mice

Type 1 CD4+-T-cell-mediated immunity is crucial for the resolution of chlamydial infection of the murine female genital tract. Previous studies demonstrating a correlation between CD4+-T-cell-mediated inhibition of chlamydial growth and gamma interferon (IFN-gamma)-mediated induction of nitric oxide synthase suggested a potential role for the nitric oxide (NO) effector pathway in the clearance of Chlamydia from genital epithelial cells by the immune system. To clarify the role of this pathway, the growth levels of Chlamydia trachomatis organisms in normal (iNOS+/+) mice and in genetically engineered mice lacking the inducible nitric oxide synthase (iNOS) gene (iNOS-/- mice) were compared. There was no significant difference in the course of genital chlamydial infections in iNOS+/+ and iNOS-/- mice as determined by recovery of Chlamydia organisms shed from genital epithelial cells. Dissemination of Chlamydia to the spleen and lungs occurred to a greater extent in iNOS-/- than in iNOS+/+ mice, which correlated with a marginal increase in the susceptibility of macrophages from iNOS-/- mice to chlamydial infection in vitro. However, infections were rapidly cleared from all affected tissues, with no clinical signs of disease. The finding of minimal dissemination in iNOS-/- mice suggested that activation of the iNOS effector pathway was not the primary target of IFN-gamma during CD4+-T-cell-mediated control of chlamydial growth in macrophages because previous reports demonstrated extensive and often fatal dissemination of Chlamydia in mice lacking IFN-gamma. In summary, these results indicate that the iNOS effector pathway is not required for elimination of Chlamydia from epithelial cells lining the female genital tract of mice although it may contribute to the control of dissemination of C. trachomatis by infected macrophages.     

Anthropometric, strength, endurance and flexibility characteristics of elite and recreational climbers

Chlamydia trachomatis is a primary cause of acute or silent salpingitis leading to infertility and ectopic pregnancy. The C. trachomatis epidemic, undiscovered in most cases, spreads, mostly in adolescents, during the years following the onset of sexual activity. As opposed to gonococcal infection which has greatly decreased, C. trachomatis cervical and urethral infection is common in young occidentals. More then 30 different studies covering 200-12,000 subjects screened in family planning centers, college women and men, students and military recruits in different parts of the USA, in Scandinavian countries and France, indicate a prevalence of 5-20% (mean 10%) in apparently healthy young females < 25 years and 5-10% in males. Female prevalence is strongly related to age, being highest (15-20%) in women < 20 years old. Several cost-benefit analyses show that the total cost of the general screening in young populations, which can easily be carried out for women in family planning centers, could save twice the cost of treatment for pelvic inflammatory disease caused by C. trachomatis and six times the total cost of C. trachomatis epidemics if late sequelae are taken into account (tubal infertility treatment, ectopic pregnancy). There is a debate among authors concerning the relative merits of total screening versus selective screening in family planning centers, the most common opinion being to do a total screening of women < 20 years old and selective screening of women 20-30 years of age with at least one risk factor, the most common risk factors being more than one partner in a year, purulent, cervical discharge, failure to use condoms and use of a contraceptive pill. Although the data clearly show that C. trachomatis screening is cost-effective, conducting of the diagnostic laboratory tests used in such screening programs should be carefully evaluated relative to cost, feasibility, specificity and sensitivity and should be adapted to the presumed prevalence in screened populations.     

Periodic health examination, 1996 update: 2. Screening for chlamydial infections. Canadian Task Force on the Periodic Health Examination

OBJECTIVE: To update the 1984 recommendations of the Canadian Task Force on the Periodic Health Examination on the routine screening of asymptomatic patients for infection with Chlamydia trachomatis. OPTIONS: Screening, with the use of culture or nonculture tests, of the general population, of certain high-risk groups or of all pregnant women; or no routine screening. OUTCOMES: Rates of asymptomatic and symptomatic chlamydial infection, perinatal complications, longterm complications of infection (i.e., pelvic inflammatory disease, infertility and ectopic pregnancy), coinfection with other sexually transmitted diseases, disease spread, hospital care, complications of therapy and costs of infection and of screening. EVIDENCE: Search of MEDLINE for articles published between Jan. 1, 1983, and Dec. 31, 1995, with the use of the major MeSH heading "chlamydial infections," references from recent review articles and recommendation by other organizations. VALUES: The evidence-based methods of the Canadian Task Force on the Periodic Health Examination were used. Advice from reviewers and experts and recommendations of other organizations were taken into consideration. Prevention of symptomatic disease and decreased overall costs were given high values. BENEFITS, HARMS AND COSTS: The greatest potential benefits of screening asymptomatic patients for chlamydial infections are the prevention of complications, especially infertility and perinatal complications, and the prevention of disease spread. There is no evidence that screening of the general population for chlamydial infections leads to a reduction in complications, and screening may increase costs. However, there is evidence that annual screening of selected high-risk groups and of pregnant women during the first trimester is beneficial in preventing symptoms and reducing the overall cost resulting from infection. RECOMMENDATIONS: There is fair evidence to support screening and treatment of pregnant women during the first trimester (grade B recommendation) as well as annual screening and treatment of high-risk groups (sexually active women less than 25 years of age, men or women with new or multiple sexual partners during the preceding year, women who use nonbarrier contraceptive methods and women who have symptoms of chlamydial infection: cervical friability, mucopurulent cervical discharge or intermenstrual bleeding; grade B recommendation). There is fair evidence to exclude routine screening of the general population (grade D recommendation). VALIDATION: These recommendations are similar to those of the US Preventive Services Task Force and the US Centers for Disease Control and Prevention, Atlanta. SPONSOR: These guidelines were developed and endorsed by the Canadian Task Force on the Periodic Health Examination, which is funded by Health Canada and the National Health Canada and the National Health Research and Development Program. The principal author (H.D.D.) was supported in part by the Ontario Ministry of Health and the Canadian Infectious Diseases Society Lilly Fellowship.     

Cell-mediated immune response to the recombinant 57-kDa heat-shock protein of Chlamydia trachomatis in women with salpingitis

Peripheral blood mononuclear cells (PBMC) from 9 of 18 women with laparoscopy-verified salpingitis proliferated in response to recombinant Chlamydia trachomatis 57-kDa heat shock protein (hsp). In contrast, PBMC from 0 of 10 women with cervicitis, 1 of 5 women with recurrent abortions, and 3 (7.1%) of 42 healthy reproductive-age women were responsive to hsp (P < .001). After passage of the hsp through an endotoxin-removing column, PBMC from 6 of 14 additional women with salpingitis were responsive to hsp, while those from 10 controls, including the 3 previously positive women, were negative. PBMC from all patients responsive to the chlamydial hsp were unresponsive to Mycobacterium bovis 65-kDa hsp. PBMC from 6 of the 15 women with a positive hsp-induced lymphocyte response were unresponsive to C. trachomatis elementary bodies. Induction of a cell-mediated immune response to the chlamydial 57-kDa hsp is a common feature of an upper genital tract infection but does not appear to be limited to women with apparent chlamydial infections.     

Recovery of cytomegalovirus and herpes simplex virus from upper and lower genital tract specimens obtained from women with pelvic inflammatory disease

Lower genital tract specimens and endometrial biopsies from 147 women with pelvic inflammatory disease (PID) and surgical specimens (fallopian tubes, ovaries, or both) from 22 women with PID and 37 women without PID were cultured for cytomegalovirus (CMV) and herpes simplex virus (HSV), as well as for organisms commonly associated with PID. CMV was isolated from 39 cervical or endometrial samples from 30 (20.4%) of 147 women with PID and from ovaries or fallopian tubes from 5 (22.7%) of 22 women with PID, but CMV was not recovered from surgical specimens obtained from 37 women undergoing surgery for tubal ligation, ectopic pregnancy, or other gynecologic conditions (P = .005). HSV was isolated from cervical samples obtained from 5 (3.4%) of 147 women with PID but not from any endometrial or surgical specimens. These data suggest that CMV, but not HSV, may contribute to the pathogenesis of PID in some patients.     

Role of Chylamydia in the pathology of pregnancy and chronic gynecological diseases

For the elucidation of the role of chlamydial infection in pathological pregnancies, serological examination by the CFT with group-specific and species ornithosis antigen was carried out on 723 blood serum specimens from women with obstetrical pathology, 124 specimens from patients with various chronic gynecological diseases and 124 control blood serum specimens from women with nromal pregnancy and favourable obstetrical anamnesis. The complement-fixing antibody (CF) was detected in 72 (9.9%) serum specimens from women with obstetrical pathology and chronic gynecological diseases. No CF antibody was found in control sera. Negative results of the CFT were obtained with species ornithosis antigen in all sera. In parallel examinations of the blood serum specimens from women with obstetrical and gynecological pathology by the CFT and intradermal test, correlation of positive results was demonstrated in 62.5% of the patients. Among the women with positive reactions for chlamydial infection, in 52.8% thee pregnancy was pathological. Among 52 sero-positive pregnant women the death of the fetus was observed in the perinatal period in 21.2%. Among 111 babies born alive after previous pregnancies 55 babies (49.5%) died at the age under 1 year. Thus, chlamydial infection may possibly have causative relation to pathological pregnancy, death of the fetus in the perinatal period, and death of the babies under 1 year.     

Chlamydial cervical infection in jailed women

OBJECTIVES: The prevalence of Chlamydia trachomatis cervical infection in incarcerated adult women has not been reported. To develop a policy for testing and treatment, we determined the prevalence of and risk factors for chlamydial infection in women in a New York City jail. METHODS: Interviews and cervical cultures for C trachomatis were obtained from 101 consenting female inmates. RESULTS: Positive cultures for C trachomatis were found in 27% of the participants. Mucopurulent cervical discharge and education of 8 years or less were two independent risk factors for infection, but only 63% of the infected women had one or both of these factors. If pelvic tenderness were considered as a third factor, an additional 7% of the infected women would have been identified. CONCLUSIONS: The prevalence of chlamydial infection in this population was as high as that in populations for which presumptive treatment is recommended. Although the optimal policy for detection and treatment of chlamydial infection may vary depending on practical considerations, we suggest that women entering correctional facilities should be screened or offered presumptive therapy for C trachomatis infection.     

Chlamydia trachomatis, pelvic inflammatory diseases and sterility

The authors analyse the results of direct (cervical, urethral, tubal) and serological research of Chlamydia trachomatis in a sample population of 420 women undergoing celioscopy due to sterility and pelvic pain, paying particular attention to a group of 193 who were found to be suffering from PID (acute, sequelae). In terms of absolute numbers the correlation between chlamydial contact-PID-sterility is confirmed, whereas in an analysis of the levels of direct positivity it is only significant for acute PID, and in cases of sequelae and in sterility with chronic infection with or without tubal damage the direct identification of Chlamydia trachomatis does not differ much from controls. Salpingo-peritoneal isolation was found to be completely lacking in significance.     

The risk of ectopic pregnancy after tubal sterilization. U.S. Collaborative Review of Sterilization Working Group

BACKGROUND: Tubal sterilization is an increasingly common method of contraception in the United States. Although pregnancy after sterilization is uncommon, it can occur and may be ectopic. We used data from the U.S. Collaborative Review of Sterilization to estimate the risk of ectopic pregnancy in women who had undergone the common types of tubal sterilization. METHODS: A total of 10,685 women undergoing tubal sterilization were followed in a multicenter, prospective cohort study. We intended to follow all the women for 5 years by means of annual telephone interviews; for women enrolled early in the study, we attempted an additional follow-up telephone interview 8 to 14 years after sterilization. To assess the risk of ectopic pregnancy in these women, we used cumulative life-table probabilities and proportional-hazards analysis. RESULTS: There were 47 ectopic pregnancies in the 10,685 women; the 10-year cumulative probability of ectopic pregnancy for all methods of tubal sterilization combined was 7.3 per 1000 procedures. The cumulative probability varied substantially according to the method of sterilization and the woman's age at the time of sterilization. Women sterilized by bipolar tubal coagulation before the age of 30 years had a probability of ectopic pregnancy that was 27 times as high as that among women of similar age who underwent postpartum partial salpingectomy (31.9 vs. 1.2 ectopic pregnancies per 1000 procedures). The annual rate of ectopic pregnancy for all methods combined in the 4th through 10th years after sterilization was no lower than that in the first 3 years. CONCLUSIONS: A history of tubal sterilization does not rule out the possibility of ectopic pregnancy, even many years after the procedure.     

Kinetics of interaction of HLA-C ligands with natural killer cell inhibitory receptors

OBJECTIVE: To measure effectiveness, adverse event experience, and acceptability of the Food and Drug Administration-approved variant of levonorgestrel capsule implants in the United States through 5 years and to examine determinants of these outcomes. METHODS: In a prospective, multicenter study, 511 sexually active women selecting contraceptive implants were monitored four times in the 1st year, then semiannually through 5 years. Adverse events were elicited by query and physical examination, and their incidence was measured. Lifetable analyses computed pregnancy and other discontinuation rates. Cox regression models examined effects of age, parity, and preadmission desire for more children on continuation. Removal times were analyzed by analysis of variance. RESULTS: Three pregnancies occurred, yielding a 5-year cumulative rate of 1.3+/-0.8 per 100 users, an average annual rate of three per 1000 women, and an ectopic pregnancy rate of 0.6 per 1000 woman years. No pregnancies occurred to women weighing less than 79 kg. Prolonged or irregular menstrual bleeding, followed distantly by headache, weight gain, and mood changes, was the most frequent medical conditions leading to removal. Weight gain averaged 1 kg per year. Each annual continuation rate was above 80 per 100, for a cumulative 5-year rate of 39 per 100. Continuation was age-dependent, with younger women (younger than 25 years at entry) having lower 5-year continuation rates than older subjects (P < .01). Tissue trauma from deeply placed or poorly aligned implants or severe reactions to local anesthetic affected subjects in 3.1% of removals (nine cases). CONCLUSION: As measured by annual continuation rates of 80 per 100 or higher and annual pregnancy rates below one per 100, implant contraception in the United States was found to be highly acceptable and effective, year after year, regardless of the woman's age or family formation status. The cumulative 5-year pregnancy rate, 1.3 per 100, is comparable to that of tubal ligation.     

Ectopic bone formation in a child with a head injury: complete regression after immobilisation

OBJECTIVE: To study the correlation between microsurgical tubal reversal after tubal sterilization and ectopic pregnancy. METHODS: 1029 women who underwent microsurgical tubal reversal were followed up. The causes of ectopic pregnancy were analysed and discussed. RESULTS: 960 intrauterine pregnanciess and 12 ectopic pregnancies occurred. The 12 ectopic pregnancies were all tubal ones, among which 2 had intrauterine pregnancies. The rate of ectopic pregnancy in the 1029 women was 1.17%, and in the pregnant cases was 1.23%. The ratio of intrauterine pregnancy to ectopic pregnancy was 1:80. The rates of ectopic pregnancy in the 1st, 2nd year and 2 years later after tubal reversal were not significantly different respectively among the tubal reversal and among the pregnant cases. The rates of ectopic pregnancy in the 1st and 2nd 6 months after tubal reversal were not statistically different. The early tubal hydrapertubation could only increase the chance of ectopic pregnancy. The sterilization method, reversal mode, and interval between sterilization and reversal were not related to the ectopic pegnancy. CONCLUSION: When the lesion in the sterilized position is completely removed, the sutures being through the tubal mucosa and the early tubal hydrapertubation not carried out, the chance of ectopic pregnancy can not be increased after tubal reversal. The contraception 6 months after tubal reversal is not related to ectopic pregnancy.     

Antibodies to chlamydia trachomatis in semen and relationship with parameters of male fertility

To screen for infection with Chlamydia trachomatis in semen samples from asymptomatic men in couples consulting for infertility and to determine the relationship of seminal chlamydial antibodies with clinically relevant parameters of male fertility, 197 randomly chosen patients were enrolled in a prospective study. The median duration of infertility was 4 years (range 1-18). Screening for C. trachomatis and chlamydial antibodies of the immunoglobulin (Ig) A and IgG classes were performed in ejaculates and, in parallel, endocervical material from the partners of the patients and serum samples from both partners were evaluated. A comprehensive examination of semen quality included sperm analyses, semen cultures, local antisperm antibody (ASA) testing, the determination of potential infection markers, and sperm-cervical mucus interaction testing in vitro (SCMPT) and in vivo (post-coital testing). Chlamydial IgA antibodies were found in the semen samples of 18.8% (37/197) of the patients, while chlamydial IgG antibodies were found in 8.1% (16/197) of the patients. Screening for C. trachomatis was negative in all semen and cervical specimens. Only 5.5% of men remembered a past genital infection. Chlamydia antibodies (IgA/Ig/G) in semen were significantly correlated with chlamydia IgG antibodies in serum samples (P < 0.001). No marked relationship was found between the presence of seminal chlamydial antibodies and the major parameters of sperm analysis, semen cultures, local ASA and sperm penetration testing as an indicator of functional capacity. Seminal chlamydial antibodies were not significantly associated with potential infection or inflammation markers in aliquots of the same ejaculates. However, a significant relationship of chlamydial antibodies in patients' semen with past genital infections of their female partners was found with clinical relevance for a tubal infertility factor. The results indicate that in asymptomatic patients the presence of chlamydial antibody IgA or IgG in semen is not associated with reduced semen quality, potential seminal infection markers or impaired functional capacity as important determinants of male fertility; however, seminal chlamydial antibodies suggesting a previous sexually transmitted disease are significantly related to a tubal infertility factor of female partners.     

Chlamydial serology in 1303 asymptomatic subfertile couples

The clinical significance of antichlamydial antibodies (Chlam Ab) was determined in a total of 1303 subfertile couples consulting for infertility investigation and treatment. Median age of the women was 30 (range 22-44) years and of the men 33 (range 21-53) years. The median duration of infertility was 4 (range 1-21) years. All patients were asymptomatic for genital tract infection. A comprehensive infertility investigation included examination of the endocrine, cervical, and tubal factor, and semen analysis, antisperm antibody (ASA) testing, sperm-mucus interaction testing in vitro using a standardized protocol, and post-coital testing (PCT). Screening for Chlam IgG Ab was performed in serum of both partners, obtained at the same time. Simultaneous microbial cultures in genital secretions of both partners included a broad spectrum of potentially pathogenic bacteria. Elevated titres of Chlam IgG Ab as seromarker for previous infection were found in 20.8% of all women, and in 12.6% of men. Chlam Ab were significantly more frequent in partners of seropositive patients (in 51.8% of women with a Chlam Ab positive partner, compared to 15.8% of the other women). Microbial screening outcome was not significantly related to results of chlamydial serology in both partners. In women, elevated titres of Chlam Ab were significantly associated with a tubal factor, but were not related to reduced quality of the endocervical mucus (CM), including the in-vitro penetrability of the CM (using partners' or donors' spermatozoa). In males, Chlam Ab were not significantly related to the outcome of semen analysis, including screening for ASA (IgG and/or IgA) in semen, and several parameters of sperm functional capacity. After exclusion of couples with tubal disease, subsequent male fertility did not significantly differ in males with or without Chlam Ab. The results suggest that during basic infertility investigation, positive chlamydial serology as an easy screening procedure indicates a higher risk for a tubal infertility factor. However, in asymptomatic patients, Chlam IgG Ab in serum are not associated with a cervical factor or with the male factor, using several determinants for evaluation of semen quality including subsequent fertilizing capacity.     

Cloning and expression of apolipophorin-III from the common cutworm, Spodoptera litura

Infections of the eye and genital tract with the bacterium Chlamydia trachomatis are a major cause of morbidity worldwide and are costly to treat. Development of a vaccine capable of protecting against infection or severe disease presents special challenges but would be the most effective long-term option for control of chlamydial disease. Progress has been made in understanding protective and pathological immune mechanisms in these infections, and a number of potential vaccine candidates have been developed.