Group B Streptococcus:
S. agalactiae

TS. agalactiae is a well-known cause of mastitis in cows. In humans, S. agalactiae has been documented as a cause of joint and cutaneous infections, as well as osteomyelitis, meningitis, pneumonia and endocarditis following bacteremic spread. In addition, urogenital infection during pregnancy leads to neonatal sepsis and meningitis. However, these human infections occur NOT because of transmission from cows to humans, but because humans themselves can be colonized with S. agalactiae in the genital and GI tracts. There is no evidence for direct transmission to humans from cows with S. agalactiae mastitis.

Group C Streptococcus:
S. equi, S, equisimilis, S. zooepidemicus

These are well-known equine, bovine, and, to a lesser degree, porcine (S. equisimilis) pathogens. Other Group C streptococci are also part of the normal flora of the human nasopharynx, skin and genital tract, and most Group C infections in people are of human origin. However, there are several examples of zoonotic Group C infections:

• Pharyngitis has developed in people following consumption of raw milk or cheese contaminated with Group C streptococci.
• Streptococcus zooepidemicus meningitis has been documented in a woman who had had close contact with and head trauma inflicted by a horse. Streptococcus zooepidemicus organisms with pulsed-field gel electrophoresis patterns identical to her isolates were also recovered from her horses.
• Streptococcus equisimilis infections in people have been linked to direct contact with jerboas (rodents) imported from Egypt.

Groups G Streptococcus:

S. canis

The most common important Streptococcus from dogs and cats is Group G S. canis. This organism causes otitis media, neonatal septicemia, cervical lymphadenopathy, polyarthritis and reproductive tract infections with abortion and mastitis in dogs. It also causes neonatal sepsis in cats.

• Streptococcus canis has also been recovered from human beings with wound infections and bacteremia.
• Beyond the potential for zoonotic infections from domestic dogs and cats, Group G infections in people have also been linked to direct contact with jerboas.

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