Rapid detection of Chlamydia Psittaci by isothermal recombinase polymerase amplification assays

Chlamydia psittaci (Cps) is a zoonotic pathogen widely distributed in nature that strictly parasitizes eukaryotic cells. Cps is typically carried by parrots and other birds, possesses high virulence and toxicity, and can cause psittacosis in humans and animals. Therefore, monitoring and preventing the spread of psittacosis holds significant economic and public health importance. In this study, the specific primers and probes targeting the CPSIT_0429 gene of Cps were designed and synthesized, and recombinase polymerase amplification (RPA) assays were developed. Utilizing a real-time fluorescence detection platform (qRPA) and a lateral flow strip combined with RPA (LFS RPA), the rapid and effective detection of Cps was achieved. The limit of detection for the qRPA assay and the LFS RPA assay with Cps DNA standards was 120 copies/uL and 13 copies/uL, respectively. The developed qRPA and LFS RPA could specifically detect Cps without cross-reactings with other common respiratory pathogens tested in this study. The qRPA assay and the LFS RPA assay were further evaluated on 334 clinical oropharyngeal-cloacal swabs, feces, and lung samples, and the detection rates of CPs were 4.80% (16/334) and 5.70% (19/334) for the qRPA and the LFS RPA, respectively. Compared with qPCR detection results, the concordance rates were 98.80% and 99.70%, respectively. Furthermore, A, B and E genotype of Cps were identified in the above positive samples. These results indicated that the qRPA assay and the LFS RPA assay developed in this study could serve as effective diagnostic tools of Cps, especially in the field detection and in resource-limited settings.