A comparison of a commercial PCR-based test to culture methods for detection of Mycoplasma gallisepticum and Mycoplasma synoviae in concurrently infected chickens.

The suitability of commercial PCR-based test kits for the detection of either Mycoplasma gallisepticum (MG) or M. synoviae (MS) was compared to detection by culture. The MG and MS kit detected six and five homologous strains respectively in broth cultures and there were no reactions with thirteen het-erologous species including M. imitans, a species phylogenetically closely related to MG. Tracheal and lung/air-sac swabs were collected from twenty 17-week-old commercial pullets which were seropositive for MS and were compared for detection of MS by kit and by culture. The results were in agreement for 13 positive and 22 negative swabs, while the remaining five swabs were either PCR-positive only (two) or culture-positive only (three). Tracheal swabs taken from seventy-six 31-week-old layers from a MS seropositive commercial flock which had been experimentally infected with MG were used to compare the MG DNA probe kit and culture. Of 76 swabs 39 were MG positive and 12 were negative by both methods. MG was detected by PCR test only in 23 other specimens, while only two swabs were negative by PCR but positive by culture. The difference between the detection methods was significant (McNemar test, P < 0.001). Concurrent MS infection was detected by the PCR-based kit in 45 of these hens.