A survey of avian Mycoplasma species for neuraminidase enzymatic activity

Among 23 currently recognized avian Mycoplasma (AM) species only Mycoplasma gallisepticum, Mycoplasma synoviae, Mycoplasma meleagridis and Mycoplasma iowae cause disease and loss of production in chickens and/or turkeys. Because neuraminidases are considered virulence factors in many pathogenic microorganisms the aim of our study was to determine which AM species possess neuraminidase enzymatic activity (NEAC). Small samples of AM cells were assayed for NEAC using the chromogenic substrate 5-bromo-4-chloro-3-indolyl-α-d-N-acetylneuraminic acid. In the case of positive NEAC reaction the substrate gave the insoluble indigoblue product what enabled simple test and easy estimation of NEAC. M. gallisepticum and M. synoviae which share sequences of the gene encoding neuraminidase (sialidase NanH) exhibited considerable levels of NEAC. However, NEAC levels differed among their strains, as well as among cultures of different strains. Only certain cultures of the type strain of M. meleagridis showed NEAC, whereas among six serovars of M. iowae only serovar I (type strain 695) showed NEAC. Weak NEAC was detectable in M. anseris, M. cloacale and M. pullorum, whereas the type strain of M. corogypsi (BV1) showed strong NEAC. Our study provides novel informations about NEAC in AM species and suggests that higher invasiveness and possibly, the pathological processes might be associated with their NEAC.