chlamydia genital infection is the most common bacterial infection sexually transmitted in the world ( 1 ) . the highest age - specific rate was reported in females aged 15 - 35 years .
the majority of the females are asymptomatic ( 2 ) , thus , providing a continuous reservoir for the infection ( 3 ) .
it is estimated that 5 - 12% of sexually active adults in the age group of 16 - 34 years in the united kingdom are infected with chlamydia trachomatis ( 4 ) . according to the world health organization ( who )
, 101.5 million people with chlamydia infection are detected globally each year ( 5 ) .
the infection risk factors include being young or adolescent , having new or frequent sexual contacts , inconsistent use of barrier contraception , history of prior sexual transmitted infection , and low educational and socioeconomic levels ( 6 ) .
thus , the prevalence of c. trachomatis may differ among racial groups because of differences in sexual risk behavior and cultural backgrounds ( 7 ) .
untreated chlamydial infections may lead to pelvic inflammatory disease ( pid ) , ectopic pregnancy , premature delivery , spontaneous abortion , low birth weight , tubal infertility and subsequent scarring of the fallopian tubes ( 8) . during pregnancy ,
chlamydial infection can cause miscarriage , premature rupture of membranes , preterm labor , low birth weight , infant mortality , neonatal chlamydial infection , and postpartum endometritis ( 9 ) .
screening , early diagnosis and treatment is considered the main policy to prevent complications and further transmission of the infection ( 10 ) .
conventional laboratory diagnosis of c. trachomatis infection is done by cell culture or antigen detection .
commercially available naats using methods such as polymerase chain reaction ( pcr ) , and ligase chain reaction ( lcr ) , are now the gold standard tests for genital chlamydia infection ( 11 ) .
pcr has good sensitivity ( 100% ) and specificity ( 99.3% ) for endocervical samples compared with urethral culture .
it is the preferred test and the most commonly used method of diagnosis , which amplifies c. trachomatis dna sequences ( 12 ) .
there are no accurate data regarding the prevalence of c. trachomatis infection in kashan and few studies from iran examined the prevalence of genital chlamydia infection based on age .
the current study aimed to assess the prevalence of endocervical c. trachomatis infection in a population of females aged 17 - 35 years in kashan , iran .
endocervical swab samples were collected by the gynecologists from 255 married females aged 17 - 35 years , with or without symptoms , referring to the obstetrics and gynecology clinics of kashan , iran , from december 2012 to july 2013 .
the study was approved by the regional research ethics committee of kashan university of medical sciences ( p 2331 ) , and all participants signed informed consent forms prior to enrolment in the study .
demographics , sexual behavior , method of contraception , previous history of sexually transmitted infections ( stis ) and symptoms were assessed by a questionnaire routinely used in the clinic .
cervical samples were collected from the endocervical region after inserting a sterile speculum into the vagina .
mucus was cleaned with a sterile cotton swab without causing any bleeding or using antiseptics .
dacron swabs were used to collect endocervical specimens . the specimen placed into sterile collection tubes containing 2 ml of transport buffer ( nah2po4 20 mm , na2hpo4 20 mm , sucrose 20 mm
, glutamin 5 mm , gentamycin 50 g / ml , vancomycin 100 g / ml , amphotericin b 25 g / ml supplemented with 10% of inactivated fetal calf serum ) and transported to the laboratory for further processing .
pcr was set up using positive control dna from c. trachomatis serovar l2 type strain 434/bu ( atcc vr-902b ) . for the negative control ,
the dna was isolated using a kiaspin pcr template purification kit , ( kiagen , iran ) according to the manufacturer s instructions .
briefly , samples were vortexed and centrifuged for 30 minutes at 14000  g. then , dna purification was performed , 200 l of each specimen was transferred and mixed with 300 l of buffer lb and 2 l of dna / rna carrier and 5 l of proteinase k in a 1.5 ml microcentrifuge tube and incubated at 65c for 10 minutes .
after incubation , 100 l of isopropanol was added to the tubes , mixed and centrifuged for 2 minutes at 5000  g. the supernatant was applied to the spin column and centrifuged at 12000  g for 1 minute , after which the filtrate was discarded and 500 l of buffers irb and 600 l of wb were added to each spin column and centrifuged again at 12000  g for 1 minute .
chlamydia trachomatis was detected by a pcr designed in the laboratory to amplify a sequence in the cryptic plasmid generating a fragment of about 512 base pair .
primers were hl1 forward , 5-tagagataggaaaccaactc-3and hl2 reverse , 5ctcgggttaatgttgcatga-3 ( 13 ) ( cinnagen , tehran , iran ) .
amplification reactions were performed in a final volume of 25 l containing 5 l of sample , 12.5 l of the master mix pcr solution ( cinnagen , tehran , iran ) , and 1 l of each reverse and forward primers .
the reaction mixture was incubated for 5 minutes at 94c , followed by 40 cycles of 1 minute at 94c , 1 minute at 45c , and 1 minute at 72c , and a final elongation step of 7 minutes at 72c .
the pcr products were analyzed by electrophoresis in the 1% tbe buffer through 1.5% agarose gel , stained with ethidium bromide 0.5 g / ml and dna bands were visualized using a uv transilluminator ( figure 1 ) .
lane m : marker ; lane 1 : negative control ; lane 2 : positive control ; lane 3 - 6 : positive samples ; 7 : negative sample .
data were analyzed using spss version 16 and the outcome variables including prevalence rates and their 95% confidence intervals ( cis ) were calculated . the chi - square or fisher s exact test was used to analyze the categorical data .
endocervical swab samples were collected by the gynecologists from 255 married females aged 17 - 35 years , with or without symptoms , referring to the obstetrics and gynecology clinics of kashan , iran , from december 2012 to july 2013 .
the study was approved by the regional research ethics committee of kashan university of medical sciences ( p 2331 ) , and all participants signed informed consent forms prior to enrolment in the study .
demographics , sexual behavior , method of contraception , previous history of sexually transmitted infections ( stis ) and symptoms were assessed by a questionnaire routinely used in the clinic .
cervical samples were collected from the endocervical region after inserting a sterile speculum into the vagina .
mucus was cleaned with a sterile cotton swab without causing any bleeding or using antiseptics .
dacron swabs were used to collect endocervical specimens . the specimen placed into sterile collection tubes containing 2 ml of transport buffer ( nah2po4 20 mm , na2hpo4 20 mm , sucrose 20 mm
, glutamin 5 mm , gentamycin 50 g / ml , vancomycin 100 g / ml , amphotericin b 25 g / ml supplemented with 10% of inactivated fetal calf serum ) and transported to the laboratory for further processing .
pcr was set up using positive control dna from c. trachomatis serovar l2 type strain 434/bu ( atcc vr-902b ) .
for the negative control , sterile deionized water was used as the pcr template instead of nucleic acid .
the dna was isolated using a kiaspin pcr template purification kit , ( kiagen , iran ) according to the manufacturer s instructions .
briefly , samples were vortexed and centrifuged for 30 minutes at 14000  g. then , dna purification was performed , 200 l of each specimen was transferred and mixed with 300 l of buffer lb and 2 l of dna / rna carrier and 5 l of proteinase k in a 1.5 ml microcentrifuge tube and incubated at 65c for 10 minutes .
after incubation , 100 l of isopropanol was added to the tubes , mixed and centrifuged for 2 minutes at 5000  g. the supernatant was applied to the spin column and centrifuged at 12000  g for 1 minute , after which the filtrate was discarded and 500 l of buffers irb and 600 l of wb were added to each spin column and centrifuged again at 12000  g for 1 minute .
chlamydia trachomatis was detected by a pcr designed in the laboratory to amplify a sequence in the cryptic plasmid generating a fragment of about 512 base pair .
primers were hl1 forward , 5-tagagataggaaaccaactc-3and hl2 reverse , 5ctcgggttaatgttgcatga-3 ( 13 ) ( cinnagen , tehran , iran ) .
amplification reactions were performed in a final volume of 25 l containing 5 l of sample , 12.5 l of the master mix pcr solution ( cinnagen , tehran , iran ) , and 1 l of each reverse and forward primers .
the reaction mixture was incubated for 5 minutes at 94c , followed by 40 cycles of 1 minute at 94c , 1 minute at 45c , and 1 minute at 72c , and a final elongation step of 7 minutes at 72c .
the pcr products were analyzed by electrophoresis in the 1% tbe buffer through 1.5% agarose gel , stained with ethidium bromide 0.5 g / ml and dna bands were visualized using a uv transilluminator ( figure 1 ) .
lane m : marker ; lane 1 : negative control ; lane 2 : positive control ; lane 3 - 6 : positive samples ; 7 : negative sample .
data were analyzed using spss version 16 and the outcome variables including prevalence rates and their 95% confidence intervals ( cis ) were calculated .
the chi - square or fisher s exact test was used to analyze the categorical data
the age of the 255 subjects ranged 17 - 35 years with a mean of 27.3  4.37 years .
the majority of them were married or living with a partner ( 98% ) , had high school education or higher ( 74% ) .
the prevalence of c. trachomatis was 2.4% ( 95% confidence interval [ ci ] 0.54 - 4.26% ) with a mean of 25.8  6.17 years ; 50% ( 3/6 ) of the subjects with a positive chlamydia test result were under the age of 25 .
of the 92 subjects in the  25-year - old group , 3 ( 3.3% ) were positive for c. trachomatis compared to three out of 163 ( 1.8% ) in the > 25-year - group ; 83.3% ( 5/6 ) of the subjects with a positive chlamydia test result were older than 16 at first sexual encounter and all of the infected subjects lived in the city .
the most general symptoms among c. trachomatis infected young subjects were vaginal discharge ( 66.6% ) and lumbar pain ( 50% ) .
no significant relationships were found between c. trachomatis infection and the risk factors , probably reflecting the small number of those who were positive in the test .
the prevalence of c. trachomatis genital infections among young females in kashan , iran was 2.4% .
the previous published reports from iran showed various prevalence of 2% to 11% ( 14 ) .
the study by chamani - tabriz et al . on the prevalence of chlamydia infection in females aged 15 - 42 attending obstetrics and gynecology clinics in tehran , from may 2003 to october 2003 showed that 12.6% were positive for chlamydia by pcr ( 15 ) . in another study on the females < 45 years attending gynecology clinics in babol , iran ,
european centre for disease prevention and control ( ecdc ) described the prevalence ranging from 1.4% to 3.0% among females aged 15 - 40 years ( 17 ) .
the prevalence of c. trachomatis infection and the risk factors in individuals < 35 years old attending sexual health clinics in barcelona province , spain , in 2006 was 3.8% and the prevalence was significantly higher in those under 25 years ( 5.8% ) compared with the ones aged 25 - 35 ( 1.6% ) ( 18 ) .
another study in melbourne , australia , showed that the chlamydia prevalence was 3.7% among sexually active females aged 18 - 24 years compared with 0.2% among 25 - 35-year - old ones ( 19 ) .
a study among the brazilian females referred to sexually transmitted diseases ( std ) clinic showed that 68% of the infected ones aged 15 - 25 year ( 13 ) . in the current study , the c. trachomatis prevalence in females
 25 years ( 3.2% ) was similar to those of reported in australia 4.9% ( 20 ) , spain 4% ( 21 ) , france 3.6% ( 22 ) and the united kingdom 3% ( 23 ) .
the current cdc guidelines recommend annual screening for chlamydia in sexually active females  25 years and the ones > 25 years old who are at increased risk ( 24 ) .
screening is especially important in pregnant females who are at risk of transmission of their infection to the fetus ( 25 ) .
chlamydia trachomatis infection is the main causative agent of abortion ( 26 ) . in the current study , abortions were reported by 16.7% of females with positive test results .
early detection and appropriate treatment of c. trachomatis can prevent the development of the disease after abortion ( 27 ) .
prevalence of c. trachomatis was found to be low among females in kashan , iran .
the reason for c. trachomatis infection low prevalence in the population under study was the scarcity of pre - marriage sexual intercourse frequency in females , having stable sexual intercourse only after marriage .
to date it was the first study in kashan to determine the prevalence of endocervical c. trachomatis infection in young females .
there were several limitations to the study , which should be considered in the interpretation of the results .
data on sexual behavior was not specifically collected for the current study . knowing a patient s number of sexual partners , sexual activity before and after sti diagnosis , and frequency of condom use may help identify the patients who are at increased infection risk .
chlamydia prevalence was low in young sexually - active females , but there is a significant difference regarding chlamydia infection in females younger than 25 years .
the new information provides evidence for the need to implement active opportunity to screen young sexually active females and the patients in all socioeconomic groups .
all sexually active females should be offered a c. trachomatis test when attending a physician .
 background : chlamydia trachomatis is one of the major bacterial agents of the sexually transmitted diseases worldwide , especially among young females . 
 there is no data regarding the prevalence of genital chlamydia infection among young females in kashan , iran.objectives:the current study aimed to determine the prevalence of endocervical c. trachomatis infection among females aged 17 - 35 years in kashan , iran.patients and methods : in the current descriptive study , 255 endocervical swab samples were collected from the obstetrics and gynecology clinics of kashan , iran from december 2012 to july 2013 . 
 cervical swabs were placed in transport media and sent to the laboratory . to identify c. trachomatis in the samples polymerase chain reaction ( pcr ) 
 was performed to amplify a sequence in the cryptic plasmid , generating a fragment of about 512base pair . 
 demographic data was collected considering the relevant risk factors by a standard questionnaire.results:a total of 255 females were tested . the prevalence of genital c. trachomatis was 2.4% ( 95% confidence interval [ ci ] 0.54% - 4.26% ) ; 3.2% of the females in the  25-year - old group were positive versus 1.8% in the 26 - 35-year - old group . 
 the most general presented symptoms of genital c. trachomatis infection were vaginal discharge ( 66.6% ) and lumbar pain ( 50% ) . 
 no significant relationships were found between c. trachomatis infection and the risk factors.conclusions:to the authors knowledge this is the first study to describe endocervical c. trachomatis infection in this area . 
 the obtained results also emphasized the importance of routine diagnosis of c. trachomatis to control of the infection . 