The Streptococcus

Hemolytic streptococci:
Hemolytic streptococci are found to be human and animal pathogens. Most clinical isolates appear as beta-hemolytic streptococci when grown on blood agar. Streptococcus pyogenes, groups B and C streptococciand Streptococcus pneumoniae are the most prevalent streptococcal pathogens isolated from humans. The human oropharynx is the sole known natural reservoir for S. pyogenes in the environment. These organisms are maintained in the throats of humans (usually children) in a “carrier state”, with up to a 30% frequency . Group B streptococci are predominantly found colonizing the human vagina, but it is also associated with animal infections. Although resistance to penicillin-based antibiotics has yet to emerge in S. pyogenes, infections caused by this organism continue to occur with occasional widespread outbreaks.