Comparison of different molecular methods for detection of Mycoplasma gallisepticum

An "In house" PCR method was compared with three commercial PCR kits for the detection of Mycoplasma gallisepticum (MG) in cultures grown in a modified Frey broth or agar, in vaccines, as well as in tracheal swabs of SPF chickens infected experimentally. The studied methods showed different specificity (poor specificity of commercial A test) and sensitivity. The "in house" method appeared to be more sensitive (7 fg/µL) than the rest of the tests (70 fg/µL). The "in house" PCR method could differentiate between TS-11 and 6/85 vaccine strains, also in the combination with restriction enzyme length polymorphism (RFLP). Furthermore, distinguishing between TS-11 and pathogenic field strains was also possible. To detect MG in tracheal swabs, SPF chickens were inoculated intranasally with 1x10⁶ colony forming unit (cfu)/mL of ATCC reference MG strain. Tracheal samples were collected 4, 7, 14, 28 and 35 d post infection (d.p.i) and examined with PCR-based methods. The MG strain was detected for the longest time, up to 28 d.p.i., by the "in house" method and commercial kit B, with a stronger result being obtained by the "in house" method. The results showed the usefulness of the studied methods for the MG direct detection in chicken swabs; however, some discrepancies were noted with regard to their different specificity and sensitivity.