All are medically important streptococci except -: (A) Strep. pyogenes, (B) Strep. agalactiae, (C) Strep. equisimilis, (D) Strep. salivarius
Answer is D. STREPTOCOCCI 

Streptococci are gram-positive, nonmotile, non-spore-forming, catalase & oxidase negative medically important bacteria.
Many organisms of streptococcus genus cause human diseases.