PPubMed26 Jun 2019Cited 20×

Finnish new variant of <i> Chlamydia trachomatis </i> escaping detection in the Aptima Combo 2 assay also present in Örebro County, Sweden, May 2019

Magnus Unemo, Marit Hansen, Ronza Hadad, Ylva Lindroth, Hans Fredlund, Mirja Puolakkainen, Martin Sundqvist

Abstract

'Hans Fredlund' 'Mirja Puolakkainen' 'Martin Sundqvist'] We identified the first two cases of the Finnish new variant of Chlamydia trachomatis (F-nvCT) beyond Finland in two clinical urogenital specimens in Örebro County, Sweden. These Aptima Combo 2 assay-negative specimens were Aptima Chlamydia trachomatis (CT) assay positive and had the characteristic C1515T mutation in the 23S rRNA gene. From 22 March to 31 May 2019, 1.3% (2/158) of the CT-positive cases in Örebro County were missed because of the F-nvCT. International awareness, investigations and actions are essential.

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First two Finnish‑variant Chlamydia trachomatis cases were found in Sweden, showing 1.3% of local CT‑positive cases were missed by the Aptima Combo 2 assay.

What’s new

i.Identified the first two cases of the Finnish new variant of C. trachomatis (F‑nvCT) outside Finland, in Örebro County, Sweden
ii.Quantified that 1.3% (2/158) of CT‑positive cases were missed due to assay escape during March‑May 2019
iii.Demonstrated that AC2 assay‑negative/equivocal specimens with RLUs 20‑99 can harbor F‑nvCT and recommended reflex testing with ACT
iv.Provided temporal data on the proportion of AC2 specimens with RLUs 20‑99, showing an increase from 0.07‑0.71% to 1.26‑2.94% after October 2018

How they did it

The team reviewed all consecutive AC2 specimens from Jan 2017 to May 2019, focusing on those with RLUs 20‑99 and negative for N. gonorrhoeae. They performed reflex testing of these specimens with the Aptima CT (ACT) assay and sequenced the 23S rRNA gene to detect the C1515T mutation characteristic of F‑nvCT.

What they found

Two F‑nvCT cases were confirmed in May 2019 (one male, one female)
1.3% (2/158) of CT‑positive cases in Örebro County were missed because of F‑nvCT
Among 77 AC2 negative/equivocal specimens with RLUs 20‑99 (Mar‑May 2019), two were ACT‑positive and harboured the C1515T mutation
The proportion of AC2 specimens with RLUs 20‑99 rose from ≤0.71% (Jan 2017‑Sep 2018) to up to 2.94% (Oct‑Dec 2018)

Caveats

✕Findings are based on only two confirmed cases from a single Swedish county
✕Surveillance was limited to retrospective data; broader national or pan‑European studies are needed
✕Current AC2 assay does not detect F‑nvCT, requiring reflex testing until a revised assay is available
✕The epidemiology, spread dynamics, and clinical impact of F‑nvCT remain uncertain

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Finnish new variant of <i> Chlamydia trachomatis </i> escaping detection in the Aptima Combo 2 assay also present in Örebro County, Sweden, May 2019

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