Evaluation of four commercial real-time PCR assays for the detection of lymphogranuloma venereum in Chlamydia trachomatis-positive anorectal samples

An Ulcer by Any Other Name

The myriad presentations of ulcerative sexually transmitted infections, other than genital herpes and syphilis, challenge even the most astute clinician given the considerable overlap in clinical presentation and lack of widely available diagnostic resources, such as nucleic acid testing, to confirm the diagnosis. Even so, case prevalence is relatively low, and incidence of chancroid and granuloma inguinale are declining. These diseases still cause substantial morbidity and increased chance for HIV acquisition, and with the recent advent of mpox as a cause, it remains imperative to identify and treat accurately.

Sexually transmitted infections and clinical features in monkeypox (mpox) patients in Madrid, Spain

Since the beginning of the monkeypox (mpox) virus outbreak in May 2022, there has been an increase in the number of cases worldwide in the setting of sexual transmission. We have tested by real-time PCR 187 mpox patients, of which 157 patients were screened for sexually transmitted infections (STI) in 245 samples. Thirty-six pathogens were detected in 30 patients: herpes simplex virus (HSV-I/II, 12/36, 33.3%), Neisseria gonorrhoeae (NG, 9/36, 25%), Chlamydia trachomatis (CT, 5/36, 13.8%), Chlamydia trachomatis-lymphogranuloma venereum (CT-LGV, 3/36, 8.3%), Treponema pallidum (TP, 4/36, 11.1%) and Mycoplasma genitalium (MG, 3/36, 8.3%). Screening of STI is recommended in mpox patients for the differential diagnosis of the main infections of sexual tract especially in patients with rectal involvement.

Use of real-time PCR as an alternative to conventional genotyping methods for the laboratory detection of lymphogranuloma venereum (LGV)

Lymphogranuloma venereum (LGV) can be differentiated from non-LGV chlamydial infection using Sanger sequencing or molecular assays, including those that are commercially-available internationally. Here, we describe the performance of a rapid real-time PCR (RT-PCR)-based strategy in differentiating Chlamydia trachomatis infections associated with LGV or non-LGV serovars. One hundred three rectal swabs, previously genotyped using Sanger sequencing of the ompA gene as a reference method, were tested in the RT-PCR assays. All non-LGV specimens were correctly identified, but the RT-PCR failed to detect 1 LGV specimen, resulting in a sensitivity of 87.5% for the non-LGV/LGV RT-PCR assay. Additional performance characteristics (e.g., specificity, accuracy, and reproducibility) were all between 93% and 100% with a limit of detection ≤100 copies/reaction. Thus, this rapid RT-PCR method for LGV detection in clinical specimens is comparable to the reference method.