Ans. b (Group B). (Ref. Textbook of microbiology by Ananthanarayan 6th ed. 187).Serological or Lancefield classification system for streptococci1Group A streptococciCatalase -,Beta-hemolysis,Bacitracin sensitive,PYR test +,Ribose not fermented.Includes Streptococcus pyogenes.2Group B streptococciCAMP + and Beta-hemolysis +.CAMP reaction (Christie, Atkins and Munch Peterson reaction) due to their ability to hydrolyze hippurate, which can be demonstrated as accentuated zone of hemolysis when streptococcus agalactiae is inoculated perpendicular to streak of staph aureus grown on blood agar.Includes only one bacterium, S. agalactiae.Currently, it has been found to be a cause of sexually transmitted urogenital infections in females.3Group C streptococciRibose and trehalose fermentation4Group D streptococciGrow in 6.5% NaCI and are optochin sensitive.Hydrolysis of bile esculin (dark brown medium)-this indicates the ability of the bacteria to tolerate bile from the liver and growth in high salt cone.Includes Enterococcus and non-Enterococcus.The Enterococci include E. faecalis, a cause of urinary tract infections, and E. faecium, a bacterium resistant to many common antibiotics. Diseases such as septicemia, endocarditis, and appendicitis have also been attributed to group D Strep. Once identified, Group D Strep can be treated with ampicillin alone or in combination with gentamicin. Viridans GroupThe Viridans Streptococci, consisting of S. mutans and S. mitis, are alpha-hemolytic bacteria.These bacteria inhabit the mouth.In fact, a large percentage of tooth decay can be attributed to S. mutans.5Group F streptococciMinute streptococci;streptococcus MG.