FIG 1.

Serotype M4 and M22 GAS (group A streptococcus) strains lack the genes for hyaluronic acid capsule biosynthesis. (A) Schematic of the alignment of the hasABC region and flanking DNA sequence in serotypes M3 (MGAS315), M22 (MGAS23384), and M4 (MGAS10750). Homologous regions were extracted from the reference genomes for serotype M3 and M4 strains. The identical region in serotype M22 was obtained by de novo assembly of short-read genome sequences of strain MGAS23384 using the serotype M4 reference genome as a scaffold and confirmed by Sanger sequencing. The regions flanking the hasABC operon in the reference serotype M3 are >99% identical to the reference genome of serotype M4. Likewise, the serotype M22 sequence is >99% identical to that of the serotype M4 reference sequence. Primer positions for targeted PCR are identified by numbered arrows. (B) Targeted PCR of the hasABC operon using primers 1 and 2 in a subset of serotype M4 (left) and M22 (right) isolates of both pharyngeal (blue) and invasive (red) origin. An approximately 5,000-bp fragment containing hasABC was amplified in strain MGAS315, and a 1,500-bp fragment was amplified from MGAS10750 and strains lacking hasABC.