Two-step polymerase chain reactions and restriction endonuclease analyses detect and differentiate ompA DNA of Chlamydia spp.

Specific and sensitive amplification of major outer membrane protein (MOMP) gene (ompA) DNA sequences of Chlamydia species with various MOMP genotypes was achieved by a two-step polymerase chain reaction (PCR). Degenerate, inosine-containing oligonucleotide primers homologous to the 5' and 3' ends of the translated regions of all chlamydial MOMP genes were used in a PCR to amplify a DNA fragment of approximately 1,120 bp. A portion of this DNA fragment was amplified in a second genus-specific reaction that yielded a DNA fragment of approximately 930 bp. A pair of degenerate oligonucleotide primers homologous to internal sequences of the primary DNA fragment was used in this PCR. This method detected three cognate chlamydial genomes in a background of 1 microgram of unrelated DNA. MOMP genes of 13 representative chlamydial MOMP genotypes of the species C. trachomatis, C. pneumoniae, and C. psittaci were amplified. In a secondary PCR, group-specific detection was achieved by the simultaneous use of one genus-specific primer and three primers derived from different fingerprint regions of three major groups of chlamydiae. This multiplex PCR differentiated the groups by the length of the amplified DNA fragments and detected the simultaneous presence of DNA sequences of the Chlamydia spp. with different MOMP genotypes. Further differentiation as ompA restriction fragment length polymorphism types among all chlamydial strains with the various MOMP genotypes analyzed here was achieved by restriction endonuclease analysis of the secondary PCR products. DNA sequences corresponding to the ompA restriction fragment length polymorphism type B577 of C. psittaci were detected in two of seven milk samples from cases of bovine mastitis.