Berlot JR, et al. - Considering the classification of Mycoplasma pneumoniae (M. pneumoniae) isolates into two major genetic groups, P1 type 1 (MP1) and P1 type 2 (MP2), based on the DNA sequence of the P1 adhesion protein gene, researchers assessed if M. pneumoniae P1 genotype is associated with disease manifestation and severity of acute M. pneumoniae infection. On comparing data of 356 patients infected with MP1 with those of 126 patients infected with MP2, it was noted that the two P1 subtypes may have different pathogenic potential. Compared to infections with MP1 strains, those with MP2 strains seemed to be more virulent.