Background:
Chlamydia trachomatis has two biovars which causes two distinct sexually transmitted diseases. The trachoma biovar causes oculo-genital infections while the LGV biovar causes lymphogranuloma venereum (LGV) which is classically characterized by genital ulceration and or by a severe proctitis among MSM. The current laboratory diagnosis of LGV infection is by clinical symptoms, serology, NAATs and genotyping based on sequencing of the MOMP gene. Such methods are time consuming and can only be performed in relatively sophisticated laboratories.

Objective:
To develop a new NAAT test for rapid detection of chlamydial DNA and to evaluate whether this newly developed NAAT test can reliably detect and differentiate between oculo-genital and LGV strains.

Method:
A multiplexed real-time PCR method was developed based on a 36-bp deletion in the PmpH gene which occurs only in the LGV biovar. Two TaqMan probes and two common primers were designed and tested for specificity and sensitivity. This method was then compared with a genotyping method in a panel of DNA collected from STD surveillance.

Result:
The real-time PCR test has a sensitivity of 0.2 IFU per reaction. Of 55 LGV, 32 non-LGV C. trachomatis and 30 negative specimens tested, 53 were correctly identified as LGV, 32 as non-LGV, and 30 negative. Only two non-LGV (by genotyping) were identified as LGV using real-time PCR. The real-time PCR method has a sensitivity of 98.1% and specificity of 91.4%.

Conclusion:
This newly developed real-time PCR method can correctly detect C. trachomatis DNA in all genotypes and differentiate LGV from the non-LGV strains. It offers rapid turn-around time, ease of use, and good sensitivity and specificity.

Implications:
Use of this testing method can enhance current STD surveillance and aid public health officials in making policy decisions regarding management of proctocolitis among MSM.