This chapter focuses on well‐known and novel streptococcal species found in human specimens and covers changes that were applied to the taxonomy of streptococci in recent years. Streptococci can cause infections in humans and in many animal species, including mammals and fish. Transmission of streptococcal infections occurs by various routes. Pathogenic species such as
S. pyogenes
and
S.pneumoniae
, which colonize the upper respiratory tract, are primarily transmitted through direct contact or droplets.
S. agalactiae
transmission from mother to child can occur during birth and within the first seven days of life. Human beta‐hemolytic group C and group G streptococci are defined as
S. dysgalactiae subsp. equisimilis
, while group C and L streptococcal animal isolates are classified as
S. dysgalactiae subsp. dysgalactiae
.
S. mutans
and
S. sobrinus
belong to the S. mutans group.