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Background: Lymphogranuloma venereum (LGV) is a sexually transmitted infection caused by Chlamydia trachomatis (CT) serovars L1, L2, and L3. LGV outbreaks caused by serovar L2 among men who have sex with men (MSM) have been reported in Western Europe. In the US, sporadic cases of inguinal and anorectal LGV have been documented but surveillance data are lacking. Currently, there is no FDA-cleared PCR test for LGV.
Methods: A total of 149 male anorectal swabs that tested positive for CT by BD ProbeTec ET CT and Neisseria gonorrhoeae amplified DNA assay were subjected to two real-time PCR assays for LGV. The first PCR is a duplex assay that specifically detects the L2 serovar, the CT plasmid and assesses for inhibition. The second PCR is a quadriplex assay that detects all LGV strains (L1 - L3), non-LGV CT, CT plasmid and human DNA as an internal control. The L-variants were distinguished by sequencing the variable domain (VD)-2 of ompA gene.
Results: Both real-time PCR assays identified 27 LGV or L2 (18.1%), 113 non-LGV CT (75.8%) and 4 negative cases out of 149 samples. Two specimens that had inconclusive results by the duplex assay were positive for LGV by the quadriplex PCR. Of three specimens identified as non-LGV by the duplex PCR, two were indeterminate and one was negative by the quadriplex PCR. Sequencing of VD-2 of ompA confirmed the LGV strains were all L2 variants with 14/24 identified as L2b and 10/24 as L2f. Co-infections with LGV and non-LGV CT were not detected by the quadriplex PCR.
Conclusions: The two real-time multiplex PCR assays performed well for detecting CT and simultaneously confirming LGV or the L2 serovar using anorectal specimens. Both PCRs are useful diagnostic and screening tools for LGV, and genotyping of L-variants could aid in the understanding of LGV transmission dynamics.