The findings and conclusions in these presentations have not been formally disseminated by the Centers for Disease Control and Prevention and should not be construed to represent any agency determination or policy.

Wednesday, March 12, 2008
P86

Abbott RealTime CT/NG Assay with Modified Formulation that Detects the Chlamydia trachomatis Variant Containing a 377 bp Cryptic Plasmid Deletion

Shiaolan Y. Ho1, Barbara Van Der Pol2, James A. Williams3, Amy D. Pantone3, Jie Lai-Zhang1, Erika M. Webb1, Catherine P. Barry1, Won S. Choi1, Klara Abravaya1, and John M. Robinson1. (1) Abbott Molecular, Des Plaines, IL, USA, (2) Marion County Health Department, Bell Flower Clinic, 1101 West Tenth Street, Indianapolis, IN, USA, (3) Division of Infectious Diseases, Indiana University School of Medicine, 545 North Barnhill Drive, Indianapolis, IN, USA


Background:
A new variant of Chlamydia trachomatis (nvCT) containing a 377 bp deletion in cryptic plasmid was reported in Sweden in late 2006. nvCT accounts for about 10 to 70% of the CT positive cases in certain counties in Sweden. The deleted region includes the CT primer binding sites for the Abbott RealTime CT/NG and CT assays.

Objective:
We have developed a modified formulation of the Abbott RealTime CT/NG and CT assays to detect nvCT. The modified formulation includes an additional set of CT primers and probe targeting a region of the cryptic plasmid outside the deletion. The performance of the modified formulation was compared to that of the original formulation and the Aptima Combo 2 (Gen-Probe) assay.

Method:
250 urine samples were collected and tested per manufacturer's instructions.

Result:
For Chlamydia trachomatis (CT), the two Abbott formulations agreed on 36/36 positives and 212/214 negatives. For Neisseria gonorrhoeae (NG), the two formulations agreed on 11/11 positives and 239/239 negatives. The performance concordance was also compared between the Abbott RealTime CT/NG assay with modified formulation and the Aptima Combo 2 assay. For CT, the two assays agreed on 37/41 positives and 208/209 negatives. There were 4 unique Gen-Probe positives and 1 unique Abbott positive. For NG, the two assays agreed on 11/11 positives and 239/239 negatives.

Conclusion:
Both the original and modified formulations of the Abbott RealTime CT/NG and CT assays provide sensitive and specific methodology for detection of CT and NG.

Implications:
A modified formulation of the Abbott RealTime CT/NG and CT assays has been developed for detection of nvCT.
(Product in development. Not available in the US.)

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