Isolation and characterization of an atypical Mycoplasma gallisepticum strain showing a new mgc2 variant.

Mycoplasma gallisepticum (MG) is an important pathogen of the poultry industry able to cause chronic respiratory disease in chickens and infectious sinusitis in turkeys. Despite the application of biosecurity measures and the availability of vaccines for chickens, monitoring systems routinely applied for MG detection are still essential for infection control. Pathogen isolation is time-consuming and not suitable for rapid detection, albeit it is a compulsory step for genetic typing and antimicrobial susceptibility evaluation of single strains. The mgc2 gene is a species-specific molecular target adopted by most of the PCR protocols available for MG diagnosis, which are also included in the WOAH Terrestrial Manual. We describe the case of an atypical MG strain, isolated in 2019 from Italian turkeys, characterized by an mgc2 sequence not detectable by common endpoint PCR primers. Considering the potential risk of false negative results during diagnostic screenings with the endpoint protocol, the authors propose an alternative mgc2 PCR endpoint protocol, named MG600, which should be considered as a further diagnostic tool. • The authors identified a novel strain of M. gallisepticum with a mutant mgc2 gene sequence. • A deletion of 30 bp impairs M. gallisepticum detection using a common PCR test. • A novel PCR protocol, was developed to successfully identify this atypical strain. • ST74 is the novel sequence type assigned to the atypical strain after genetic typing through MLST. [ABSTRACT FROM AUTHOR]