Isolation of MS clones from cultures of tracheal, cloacal or egg swabs was hampered by the presence of another Mycoplasma species in many samples, growing faster than MS in vitro. Assays performed with FM4 broth medium supplemented with erythromycin failed to arrest the growth of this Mycoplasma species, suggesting its resistance to erythromycin. Analyses performed by MALDI-TOF MSP on 14 clones identified this species as M. pullorum. This identification was confirmed by analysis of whole genome sequences obtained on these 14 clones.