Search

Molecular typing techniques with sufficient discriminatory power are required to better understand the transmission of Mycoplasma synoviae, a poultry pathogen with increasing clinical and economic relevance. A promising molecular technique is polymerase chain reaction and subsequent sequencing based on the conserved 5' region of the M. synoviae variable lipoprotein and haemagglutinin (vlhA) gene. This technique was used for genotyping 27 mainly Dutch M. synoviae isolates from different organs of various categories of poultry housed on different farms and collected during a period of 10 years. The obtained vlhA sequences were compared with those of M. synoviae strains from Genbank and data obtained by amplified fragment length polymorphism (AFLP). Grouping based on 100% similarity revealed nine genotypes. Some isolates had identical vlhA gene sequences although they originated from different geographical areas, different years and organs. AFLP analysis results largely confirmed the results obtained by vlhA sequence typing. Our findings raise concern regarding the discriminatory power of these techniques for its use in molecular epidemiology of Dutch M. synoviae isolates and for the differentiation between M. synoviae vaccine strains and field isolates, and indicate that molecular typing based on additional markers should be considered.

Mycoplasma synoviae is a major pathogen of chickens and turkeys, causing economic losses to the poultry industry worldwide. In this study, we validated and applied polymerase chain reaction (PCR) and DNA sequence analysis on the N-terminal end of the hemagglutinin encoding gene vlhA as an alternative for the detection and initial typing of field strains of M. synoviae in commercial poultry. PCR primers were tested against isolates of M. synoviae from various sources along with other avian mycoplasma and other bacterial species. The vlhA gene-targeted PCR assay was highly specific in the identification of M. synoviae, with a detection limit of 4.7 x 10(2) color changing units/ml. DNA sequence analysis of amplified products was also conducted to validate the potential for typing M. synoviae strains using the N-terminal region of the vlhA gene. To evaluate the test, we applied the PCR assay to tracheal swabs collected from chickens challenged with M. synoviae strain K1968 and compared the results to the serologic detection. The PCR assay was also evaluated directly on tracheal samples collected from commercial layers. Overall, this vlhA gene-targeted PCR is a useful tool for detection and initial typing of M. synoviae and can be applied in the preliminary identification of M. synoviae isolates directly from clinical samples.