Reduction of non-typeable results using a plasmid oriented Lymfogranuloma venereum PCR for typing of Chlamydia trachomatis positive samples

Chlamydia trachomatis genovariant L2b in men who have sex with men in Taiwan, 2020-2023

OBJECTIVES

Lymphogranuloma venereum (LGV) caused by Chlamydia trachomatis genotypes L1-L3 has been resurging among men who have sex with men (MSM) and people with HIV (PWH) in Western countries. While historically attributed to tropical regions, rectal LGV has been rarely recognised in Asia, with Taiwan recently becoming the second Asian country to report cases.

METHODS

A multicentre, laboratory-based surveillance was conducted from January 2020 to December 2023 in Taiwan. Specimens were collected from MSM through syndromic testing and screening of high-risk populations. C. trachomatis was identified using commercial multiplex PCR assays, with genotyping performed through ompA gene sequencing. LGV-positive samples underwent multilocus sequence typing (MLST) following established protocols.

RESULTS

Among 446 C. trachomatis-positive samples, 391 (87.7%) underwent successful ompA sequencing. Genovariant L2b accounted for 9.7% of cases, predominantly among PWH with rectal chlamydia (18.2%). PWH accounted for 85.7% of all genovariant L2b cases. Of 38 genovariant L2b samples from 35 cases, 34 (84.2%) samples completed MLST, revealing sequence type (ST) 53 as the predominant strain (74%). ST39 and ST63 were identified as unreported STs in Western countries, along with previously reported ST58. The four identified STs formed a cluster.

CONCLUSIONS

Our findings indicate the clonal spread of C. trachomatis L2b-ST53 among MSM in Taiwan, primarily affecting PWH. The predominance of ST53 suggests potential international and domestic spread, indicative of the need for enhanced surveillance.

The challenges in lymphogranuloma venereum diagnosis whether NAAT is negative, a case series

BACKGROUND

Persistent inguinal lymphadenopathy can range from benign to malignant causes. Lymphogranuloma venereum (LGV), a sexually transmitted infection (STI), is a possible cause, particularly in individuals engaged in sexual practices associated with a higher likelihood of transmitting STIs. This case series outlines the diagnostic challenges of LGV.

CASE PRESENTATION

Two male patients, aged 36 and 48, with sexual practices associated with an elevated risk of STI transmission, presented with inguinal lymphadenopathy. Initial investigations, including rectal and genital nucleic acid amplification tests (NAATs) for STIs, were negative. Patient one underwent two fine-needle aspirations, both inconclusive. An excisional biopsy later confirmed LGV through a positive NAAT for Chlamydia trachomatis and consistent pathology. The diagnosis took several years, included three PET scans, and was complicated by a surgical site infection with Staphylococcus aureus. Patient 2, despite negative NAAT results, was empirically treated for LGV based on clinical suspicion, with resolution after doxycycline.

INTERVENTION AND OUTCOME

Both patients improved significantly with doxycycline. Retrospective serology showed elevated Chlamydia trachomatis IgG titers, supporting this diagnosis.

CONCLUSION

This case series emphasizes the need to consider LGV in patients with persistent lymphadenopathy and sexual practices that may increase the likelihood of STIs.

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.