Intrahost sequence variation in the streptococcal inhibitor of complement gene in patients with human pharyngitis.
Selection of new variants of the streptococcal inhibitor of complement protein has been implicated in the perpetuation of epidemics caused by serotype M1 strains of group A Streptococcus (GAS). The frequency at which new streptococcal inhibitor of complement (Sic) variants arise in an infected individual is not known. To study this issue, the sic gene was sequenced in 100 isolates cultured from throat swabs of each of 20 patients with acute pharyngitis caused by serotype M1 GAS. Five patients were infected with GAS populations expressing 2 Sic variants characterized by deletion of a region of the protein. In contrast, no intrahost variation was detected in the number of a pentanucleotide repeat (CAAAA) that controls production of a bacterial cell-surface collagen-like protein by slipped-strand mispairing. Sic variation occurs at a sufficient frequency in vivo to result in mixed infections on the mucosal surface of human hosts, potentially contributing to pathogen survival.
Matsumoto
Masakado
M
Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA.
Hoe
Nancy P
NP
Liu
Mengyao
M
Beres
Stephen B
SB
Sylva
Gail L
GL
Brandt
Claudia M
CM
Haase
Gerhard
G
Musser
James M
JM
D000208:Acute Disease; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D003094:Collagen / Q000235:genetics; D017353:Gene Deletion; D014644:Genetic Variation; D006801:Humans; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D010612:Pharyngitis / Q000382:microbiology*; D010614:Pharynx / Q000382:microbiology; D013290:Streptococcal Infections / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000737:chemistry / Q000235:genetics*
D001426:Bacterial Proteins; C097739:SIC protein, Streptococcus; C423453:Scl2 protein, Streptococcus; D003094:Collagen