A nested multiplex polymerase chain reaction assay for the differential identification of three zooanthroponotic chlamydial strains in porcine swab samples.

Porcine chlamydial infection is an enzootic infectious disease caused by multiple members of the family Chlamydiaceae (e.g. Chlamydophila abortus, Chlamydia suis, and Chlamydophila pneumoniae). Rapid and accurate differentiation of these pathogens is critical in the control and prevention of disease. The aim of the current study was to develop a nested multiplex polymerase chain reaction (nmPCR) assay to simultaneously detect the 3 chlamydial pathogens in clinical samples. In the first round of the nmPCR, 1 pair of family-specific primers were used to amplify the 1,100 base pair (bp) fragment of chlamydial ompA gene. In the second round of the nmPCR, 4 inner primers were designed for Ch. abortus, C. suis, and Ch. pneumoniae. Each pathogen produced a specific amplicon with a size of 340 bp, 526 bp, and 267 bp respectively. The assay was sensitive and specific for detecting target pathogens in both cell cultures and clinical specimens. The results, incorporated with the improved rapid DNA extraction protocol, suggest that the nmPCR could be a promising assay for differential identification of different chlamydial strains in pigs.